All 5 Releases Whether you are part of our community or are interested in joining us we welcome you to Washington University School of Medicine Artificial intelligence identified 3 subtypes of Chiari type-1 malformations by Mark Reynolds•November 18 An MRI scan shows a Chiari type-1 malformation in which the cerebellum extends beyond the gap in the skull where it connects to the spinal cord Researchers at Washington University School of Medicine in St Louis have used AI tools to describe three sub-types of Chiari type-1 which will help guide clinicians to make the most effective treatment decisions for their patients Roughly 4% of the population is affected by a congenital brain malformation that has eluded researchers’ efforts to find causes and treatments the diagnosis is straightforward: the lower part of the brain protrudes at least five millimeters through the gap in the skull that connects to the spinal cord There’s no one known cause for Chiari type-1 and the symptoms it can cause are unpredictable The most common problems include chronic headaches difficulty swallowing and decreased muscle strength a condition that occurs when a cyst forms in the spinal cord Sometimes these symptoms occur in combination people can live their whole lives with no ill effects The breadth of Chiari type-1 presentations has made it difficult for physicians to develop a consistent treatment protocol for their patients Louis researchers has begun to fill that gap A collaboration among neurosurgeons and computer scientists has defined three sub-types of Chiari type-1 with distinct characteristics that physicians can use to plan treatment options for their patients The results are available in the journal Neurosurgery More and better information was needed to refine Chiari type-1 diagnoses so doctors could reliably determine which cases call for which clinical interventions a surgical operation can widen the opening at the base of the skull to reduce pressure on the brain and relieve certain symptoms in some Chiari type-1 patients “Chiari represents a substantial proportion of all the patients that pediatric neurosurgeons see – it’s probably in the top three leading causes of surgeries,” said Sean Gupta, MD a neurosurgery resident at WashU Medicine and a co-lead author of the study He explained that not every type of patient responds to or needs the procedure It is particularly necessary in patients who present with both syringomyelia and headaches though some patients continue to experience effects despite surgery Other cases may be managed with pain medications or monitored Most cases remain undetected to patients and their doctors alike looking at a random selection of people who had MRIs but no diagnosis when we specifically look for Chiari malformations you find something like up to 4% of the population has it but it doesn’t necessarily cause them any problems,” Gupta said For the cases that are affecting the health and quality of life of patients doctors only had incomplete information on how and when to best treat a spectrum of symptoms that did not always respond to interventions in the same way There was no shortage of available data to search for patterns in malformations and symptoms to identify subtypes for which treatment protocols could be devised. WashU Medicine is the lead institution in the Park-Reeves Syringomyelia Research Consortium with information from more than 1,200 patients with Chiari type-1 to comb for correlations hundreds of variables for each patient — ranging from clinical data and brain imaging to health insurance status a subset of these variables was carefully selected using a combination of data-driven methods and clinician input gathered through a survey of expert pediatric neurosurgeons nationwide “It’s what we call a very high-dimensional problem, in that there are many variables that have to be considered,” said Chenyang Lu, PhD, a co-senior author of the study and the Fullgraf Professor of Computer Science & Engineering in the McKelvey School of Engineering and founding director of the AI for Health Institute at WashU McGlothlin chair of the Department of Neurosurgery at Virginia Commonwealth University School of Medicine approached Lu because the artificial intelligence tools like those with which he works are extremely good at sifting through large data sets to identify patterns and correlations within the many variables associated with Chiari type-1 cases These patterns could then serve as indicators to physicians seeking the best treatment options for their patients a PhD student in the Lu lab at WashU and co-lead author developed the AI algorithm to sort through which of the 500-plus variables in the dataset clustered together Three distinct subtypes of Chiari type-1 emerged Cluster 1 patients were more likely to be female tended to be diagnosed slightly later in childhood and presented with chronic headaches and few other health issues Cluster 2 patients were younger and had fewer headaches but a wider range of other issues such as muscle control and swallowing difficulties The third cluster usually presented with spinal deformities which may require the standard decompression procedure and possible further spine surgeries “This should help in the effort to develop guidelines that will decide which patients need to get surgery or what other therapy may need to happen,” Gupta said “We need to have some sort of evidence-based consensus opinion on how a clinician treats or manages these patients Until now we have been working from very imperfect data.” who is already working to further refine and develop this model said she believes that the collaboration between clinicians and computer scientists in this study has the potential to be transformative across the field of medicine “With the growing power of computational tools and the vast data in electronic health records AI can serve as a catalyst for generating novel insights for clinicians enabling us to work together toward impactful discoveries and better patient care.” Gupta VP, Xu Z, Greenberg, JK, Strahle JM, Haller G, Meehan T, Roberts A, Limbrick Jr DD, Lu C. Using artificial intelligence to identify three presenting phenotypes of Chiari type-1 malformation and syringomyelia. Neurosurgery. Nov. 18, 2024 DOI: 10.1227/neu.0000000000003249 Neurosurgery is  the official publication of the Congress of Neurological Surgeons, published in the Lippincott portfolio by Wolters Kluwer This project received grant funding from the Neurosurgery Research and Education Foundation (NREF) 2023-24 NREF & AANS/CNS Section on Pediatric Neurological Surgery Research Fellowship Grant (VPG) and the NIH NINDS P01NS131131-01 5758 Program Project Grant (DDL) The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH About Washington University School of Medicine WashU Medicine has a storied history in MD/PhD training recently dedicated $100 million to scholarships and curriculum renewal for its medical students and is home to top-notch training programs in every medical subspecialty as well as physical therapy j.church@wustl.edu Mark Reynolds r.mark@wustl.edu and both occupational and physical therapy specializing in science and medicine with publications in CNRS International He is a former editor of McGill University’s Headway/En Tête research magazine and has won awards from the Canada Council for the Advancement of Education including for best science writing He has a bachelor’s degree from Dalhousie University in Halifax Could help determine which patients are likely to benefit from new Alzheimer’s drugs GLP-1 medications tied to decreased risk of dementia At WashU Medicine, we transform lives and shape the future of healthcare through pioneering research, world-class education, and unparalleled patient care. As one of the nation's largest academic clinical practices, we bring the full power of WashU Medicine to every patient, advancing treatment and training the medical leaders of tomorrow at Barnes-Jewish and St. Louis Children's hospitals and more than 130 clinics across Missouri and Illinois Consistently recognized among the nation's top institutions for research we are driven to challenge convention and elevate care for all Metrics details Chiari malformation type I (CMI) typically manifests with Valsalva-induced occipital headaches and commonly co-occurs with syringomyelia The disruption of cerebrospinal fluid (CSF) dynamics at the craniocervical junction (CCJ) is a key pathophysiological feature The rectus capitis posterior minor (RCPmi) innervated by the C1 nerve root’s posterior branch significantly facilitates CSF flow at the CCJ correlating closely with occipital headaches This study aims to explore RCPmi functionality in CMI patients compared to healthy controls using needle electromyography (nEMG) Data from adult CMI patients and a health group collected from January 2023 to May 2024 were analyzed Both groups underwent bilateral RCPmi nEMG testing and spontaneous potentials during Valsalva maneuvers with additional subgroup analyses based on headache presence tonsillar herniation relative to the C1 vertebra The study included 40 CMI patients and 30 healthy controls with no demographic differences Healthy controls displayed stable RCPmi-nEMG parameters with intense electrical activity during Valsalva maneuvers CMI patients exhibited substantial denervation damage in bilateral RCPmi characterized by insufficient electrical signal response and sparse motor units Subgroup analysis revealed increased denervation in patients with headaches RCPmi plays a critical role in maintaining cranio-cervical stability and modulating intracranial pressure CMI patients show widespread denervation damage in RCPmi strongly linked to enhanced obstruction of CCJ-CSF flow and typical headache symptoms likely related to pathological factors like C1 nerve root compression by herniated cerebellar tonsils and inflammatory mediator release at the CCJ highlights the functional failure of RCPmi as a novel target for understanding the headache mechanism in CMI and for developing pain interventions RCPmi plays a crucial role in the pathophysiological mechanism of CMI RCPmi is critically involved in both CCJ-CSF circulation and cervical-occipital stability making the study of its functional status essential there are currently no studies on the needle electromyography (nEMG) of RCPmi in CMI patients the objectives of this study are to explore: (1) the nEMG parameters of RCPmi in a healthy adult population; (2) the nEMG characteristics and presence of denervation damage in RCPmi of CMI patients; (3) the pathophysiological mechanisms causing denervation damage in RCPmi of CMI patients; (4) new pathophysiological mechanisms and interventional targets based on RCPmi denervation damage in CMI We selected CMI patients treated at the Neurosurgery Department of Sichuan Provincial People’s Hospital between January 2023 and May 2024 A control group of healthy individuals with no demographic differences was also recruited All participants were informed of the potential risks associated with nEMG and signed an informed consent form Our research team will protect the privacy and personal information security of the participants and use it solely for the purpose of this study This study strictly adheres to applicable national and international regulations and ethical standards including but not limited to the Declaration of Helsinki Any unexpected harm that occurs during the research process will be properly handled by the research team and reported to the ethics committee The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request Exclusion criteria: (1) Incomplete research data; (2) History of cranio-cervical trauma (especially Whiplash injuries) or high cervical disc herniation that could damage the C1 nerve or RCPmi; (3) Age < 18 or > 80 years; (4) Contraindications to nEMG of RCPmi (including those with CVJ occupying lesions vascular malformations; coagulation disorders; dermatitis in the posterior cervical region) CMI patients and healthy controls were independently recruited by our Center of Neurology (combining departments of Neurosurgery and Neurology) The nEMG testing and assessment were independently performed by our Electrophysiology Center maintaining blinding of both the testers and the subjects Reference diagram for nEMG puncture localization of RCPmi sagittal view near midline RCPmi localization slice 3D perspective reconstruction localization slice 3D body surface reconstruction localization slice (F) Localization diagram of RCPmi puncture site on the subject (G) Intraoperative C-arm X-ray sagittal localization diagram during puncture (I) Preoperative nEMG examination puncture using methylene blue to stain RCPmi immediately followed by posterior cranial fossa decompression surgery to verify puncture accuracy Results show that the deep blue part is the left side RCPmi Concentric circle needle electrodes (37 mm × 0.45 mm, 1.5″ × 26G) were inserted and connected to a neurological electrophysiological monitoring stimulator (Keypoint-four channels-Dantec, Denmark) (Fig. 1H) Signals with missing baseline or excessive noise were corrected passed through a band-pass filter (20–10,000 Hz) Data corrections were performed using software developed in Matlab (The Mathworks) which involved removing offset voltages and QRS waves nEMG data were collected consistently to ascertain baseline activity/noise values ensuring that each data channel was free of noise and artifacts nEMG assessments of the left and right Rectus Capitis Posterior Minor were performed sequentially Measurements included spontaneous potentials at rest and average amplitude of motor unit action potentials (MUAPs) during light contraction and recruitment phases during intense contraction (IP) as well as nEMG images during coughing (with the head and neck stationary) the presence of two or more fibrillation potentials or sharp waves in the same muscle was considered abnormal recruitment phase potentials were classified as normal if presenting as simple or simple-mixed phases; a purely simple phase during intense contraction suggested abnormalities whereas mixed and interference phases were deemed normal Data analyses were conducted using SPSS 25.0 and Graphpad Prism 9.5 Quantitative data following a normal distribution were expressed as mean ± standard deviation (\({\bar{\text{X}}}\) ± σ) and comparisons between groups were made using t-tests For non-normally distributed quantitative data medians (interquartile ranges) M (IQR) were used and group comparisons were performed using the Mann-Whitney U test Categorical data were presented as frequencies (n) and percentages (%) with comparisons made using the Chi-square test with a p value < 0.05 considered statistically significant The datasets used and/or analysed during the current study available from the corresponding author on reasonable request We prospectively collected data from 40 CMI patients (22 females, 18 males; average age = 45.88 years) and 30 healthy controls (21 females, 9 males; average age = 49.10 years), with no demographic differences between the groups (Table 1) the average tonsillar herniation (TH) was 8.76 mm with 25 cases (62.5%) experiencing headaches and 27 cases (67.5%) having syringomyelia adjacent to the C1 segment Typical nEMG graphs of healthy adults and CMI patients (A–D) Typical feature graphs of RCPmi nEMG in healthy adults Figure (A) Motor unit action potential (MUAP) graph during light contraction showing that motor units have relatively short average durations Figure (B) High interference amplitude during intense contraction with recruitment phases as interference phases Figure (C) RCPmi shows no spontaneous abnormal potentials at rest Figure (D) During coughing or other Valsalva maneuvers RCPmi has instantaneous ultra-high amplitudes (E–H) Typical feature graphs of RCPmi nEMG in CMI patients Figure (E) Motor unit action potential (MUAP) graph during light contraction showing that motor units have relatively long average durations Figure (F) Low interference amplitude during intense contraction Figure (G) RCPmi often shows spontaneous abnormal potentials at rest Figure (H) During coughing or other Valsalva maneuvers Display of differences in nEMG parameters between healthy adults and CMI patient subgroups The vertical axis represents parameter names Figures (A (R))–(G (R)) represent the nEMG parameters of the right RCPmi Figures (A (L))–(G (L)) represent the nEMG parameters of the left RCPmi CMI patient subgroups are marked with common colors: red represents the CMI headache and non-headache groups blue represents the cerebellar tonsil herniation (TH) groups exceeding or not exceeding C1 and green represents the syringomyelia (SM) groups involving or not involving C1 Figures (A–E) data are continuous numerical parameters SM/C1 syringomyelia involving the C1 vertebra Mechanism of action and anatomical relationships of RCPmi in normal populations and CMI patients (A) Anatomical mechanism of RCPmi at the CCJ area in resting state healthy individuals In healthy individuals at rest or during low-intensity activities ensuring stability of the occipitocervical joint and relaxation of the CCJ dura during daily activities (B) Physiological mechanism of RCPmi at the CCJ area during Valsalva maneuvers in healthy individuals When healthy individuals experience a sudden increase in ICP during Valsalva maneuvers or other causes the cerebellar tonsils move rapidly towards the CCJ and the CCJ-CSF flow speed increases sharply pulling on the CCJ dura through MDBs to expand outward (C) Anatomical mechanism of RCPmi at the CCJ area in asymptomatic CMI patients during Valsalva maneuvers or other causes of sudden ICP increase In asymptomatic CMI patients during Valsalva maneuvers the cerebellar tonsils move noticeably towards the CCJ causing significant dorsal expansion of the CCJ dura instantly expanding the arachnoid space at the CCJ to promote rapid CSF flow through the CCJ quickly alleviating this sudden ICP pressure the cerebellar tonsils appropriately rebound thus restoring a relatively balanced state at the CCJ (D) Pathological mechanism of RCPmi at the CCJ area in symptomatic CMI patients during Valsalva maneuvers In symptomatic CMI patients during Valsalva maneuvers or other causes of sudden ICP increase the CCJ also encounters physical obstruction from herniation of the cerebellar tonsils also compressing the posterior branch of the C1 nerve root and causing denervation damage to RCPmi (fat liquefaction further increasing the pressure differential at the CCJ pushing the cerebellar tonsils further downward and exacerbating the compression on the CRN1/2 The sensory fibers of the CRN1 then radiate this stimulation to the occipitocervical region the cerebellar tonsils undergo chronic herniation compression under long-term overload and inflammatory infiltration gradually become sclerotic and lose compliance compression friction by the cerebellar tonsils Because of compression by the cerebellar tonsils the CRN1 suffers damage and demyelination reactions participating in and exacerbating the vicious cycle of RCPmi denervation damage Considering RCPmi’s susceptibility to traction injuries from whiplash could such injuries disrupt CCJ-CSF flow by damaging the C1 nerve or RCPmi leading to a pressure differential in the craniovertebral area and thus a passive descent of the cerebellar tonsils (CMI) Their results indicated that electromyographic activity of RCPmi did not change significantly under different directional forces leading the authors to suggest that RCPmi’s function might be to maintain stability of the joint surfaces in the occipitocervical region Our nEMG results indicate that compared to healthy individuals the CMI group exhibits extensive evidence of denervation in RCPmi although this difference has not yet reached statistical significance and requires further verification with a larger sample size our study reveals significant denervation damage in bilateral RCPmi of CMI patients Although this prospective double-blind evidence is quite reliable it still requires further validation through multi-center large data studies the cerebellar tonsils may rebound appropriately thus restoring a relatively balanced state System Mapping flowchart of the pathological processes related to the CCJ in CMI patients during Valsalva maneuvers or daily cerebellar tonsils pulsate there are three factors causing Denervation of RCPmi: (A) Compression of PB-CNR1 by tonsillar; (B) Syringomyelia; (C) Inflammation of CNR1 branch; (D) Cervicomedullary injury And there are four mechanisms causing Head (neck) pain: ① Compression of CNR1 by tonsillar herniation/pulsation; ② Stimulation of CCJ dural receptors by tonsillar; ③ CCJ instability; ④ Inflammation of C1 branch patients with CMI who exhibit cerebellar tonsillar herniation extending beyond the level of the C1 vertebra may be at risk of C1 nerve root compression only those patients who concurrently present with significant denervation of the RCPmi necessitate opening the dura mater for exploration and neural decompression as well as numerous other suboccipital muscle groups releasing the C1 nerve root can aid in restoring the function of these muscles the sensory fibers of the C1 nerve root contribute to the sensory perception of the occipitocervical region Decompressing the compressed C1 nerve root can help alleviate the typical cervico-occipital pain symptoms it is necessary during surgery to perform intradural exploration and decompression of the C1 nerve root in patients whose cerebellar tonsillar herniation extends beyond C1 and who have severe denervation of the RCPmi Although Syringomyelia can cause certain denervation damage to RCPmi it is more likely a result of the exacerbation of CCJ-CSF circulation disorders caused by RCPmi damage treating denervation of RCPmi might take precedence over direct treatments for Syringomyelia (such as spinal shunting) Research connects these symptoms to morphological changes in RCPmi These inconsistencies may stem from unclear headache classifications the inherently small size of the RCPmi makes it susceptible to demographic influences and the low sample sizes in some studies can easily lead to systematic errors in measurements functional nEMG testing of RCPmi might provide more accurate assessments than morphological studies alone Since cough-induced Valsalva occipital headaches are the most typical symptom in CMI patients perhaps the typical headaches in CMI patients are also closely related to the Occipital Nerve and can be treated minimally invasively in this manner compression of the C1 nerve root simultaneously causes occipitocervical headaches and denervation damage to RCPmi And the damage to RCPmi then triggers instability in the occipitocervical area Our results show that occipitocervical pain in CMI patients is closely related to degenerative damage to the suboccipital muscle group treating pain and relaxing the suboccipital muscle group while simultaneously alleviating the compression or damage to the C1 nerve is a new target for treating CMI patients Some physiotherapy programs have inadvertently produced therapeutic effects on the RCPmi we administered targeted rehabilitation therapy focusing on the RCPmi to four CMI patients with significant symptoms who declined surgical intervention All patients experienced varying degrees of symptom relief post-treatment electrophysiological reassessment of their RCPmi revealed partial recovery from denervation in two patients Although the follow-up period is currently short and the sample size is limited these findings suggest that rehabilitation therapy targeting the RCPmi may be effective for some CMI patients intraoperative excessive bone removal should be minimized to prevent postoperative instability of the atlanto-occipital joint which led to most observed differences within CMI subgroups lacking statistical significance and no asymptomatic CMI patients were collected to verify some of our theories In addition to RCPmi, muscles that can affect CCJ-CSF flow or stability of the CCJ include RCPma, suboccipital oblique muscles, etc42 due to the safety and variable control of nEMG testing But the real situation might be that the entire suboccipital muscle group and muscle-dural bridge group are working together which requires further research to explore this complex mechanism The C1 nerve root has many motor fibers but few sensory fibers so it may only play a partial role in occipitocervical pain The C2 nerve root might also play an important role For the sake of safety and simplicity of analysis in nEMG which requires further research in the future The nEMG parameters of RCPmi in healthy adults remain relatively constant at rest or during light contraction indicating its role in maintaining the stability of the occipitocervical joint RCPmi plays an important role in maintaining constant ICP Compared to the healthy control group: CMI patients exhibit widespread denervation damage in RCPmi This may cause further exacerbation and symptom manifestation of CCJ-CSF fluid dynamic disturbances in CMI patients the causal relationship between the two requires further research The cause of RCPmi denervation damage may stem from compression of the C1 nerve root by the herniated cerebellar tonsil stimulation of CCJ dural receptors (from compression of posterior cranial fossa brain tissue or excessive pulling of RCPmi) overload of RCPmi and other deep cervical muscles Occipitocervical headaches in CMI patients are mainly 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invasive tubular retractors for foramen magnum decompression of Chiari malformation: A technical note and case series Download references We thank Chief physician Ying Liu and Meiyun Hu (Sichuan Provincial People’s Hospital Electrophysiological center) for their guidance in electrophysiology Funding was provided by Natural Science Foundation of Sichuan Province (Grant No JNKY2024-103) Sichuan Medical and Health Care Promotion Institute (Grant No Sichuan Lansheng Brain Hospital and Shanghai Lansheng Brain Hospital Investment Co. University of Electronic Science and Technology of China Chengdu wenjiang District people’s hospital Sichuan Provincial Center for Mental Health and Minbing Bao contributed equally to this work and should be regarded as joint first authors All authors made substantial contributions to the study design and final approval of this manuscript.Bo Wu and Zhou Zhang contributed equally to the conception and provided financial and equipment support They should be recognized as co-corresponding authors The authors declare no competing interests Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41598-025-86528-4 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science This Clinician's View is written by Joseph Lopez, MD AdventHealth for Children medical director for pediatric head & neck surgery Paisley Battles had experienced more medical tests than many people do in a lifetime yet she was still suffering from frequent severe headaches daily pain in her lower extremities and delayed speech with no clear diagnosis after Paisley experienced a syncope episode in her car seat her parents drove straight from their home in Edgewater to the AdventHealth for Children emergency room where the medical team admitted her A magnetic resonance imaging (MRI) scan revealed the diagnosis — Chiari malformation type 1 (CM1) Chiari malformations (CM) are caused by problems in the structure of the brain and skull Affecting approximately 1 in 1,000 children Chiari malformation type 1 is the most common form and occurs when the cerebellar tonsils (the lower part of the cerebellum) push into the foramen magnum (the opening between the skull and spinal cord) The condition develops as the skull and brain are growing and can put pressure on the brain At AdventHealth for Children, James Baumgartner, MD and I recently began taking a new surgical approach to treating Chiari malformation type 1 with the aim of improving patient outcomes: suboccipital posterior vault distraction osteogenesis (PVDO) and we have since successfully performed 4 additional suboccipital PVDO procedures The Challenges of Chiari Malformation Type 1 While Chiari malformation type 1 can be asymptomatic the altered cerebrospinal fluid dynamics along with the pressure from the cerebellum on the spinal cord or lower brainstem can cause troubling symptoms to arise in some patients As in Paisley’s case, when patients present with symptoms, we use MRI to help make the proper diagnosis. The presence of associated cranial nerve deficits, brainstem dysfunction, kyphosis (excessive forward rounding of the upper back), and syringomyelia (the development of a fluid-filled cyst within the spinal cord), particularly in young patients in early stages of disease, are indications for operative intervention Paisley’s MRI revealed crowding of the foramen magnum and a mass effect on her cervicomedullary junction the region where the brainstem continues as the spinal cord indicating a potential benefit from surgical treatment Traditional Surgical Approach to Treating Chiari Malformation Type 1 suboccipital posterior fossa decompression (PFD) has served as the standard surgical approach to treating Chiari malformation type 1 It involves removal of a portion of the skull to create more space for the cerebellum PFD is typically performed alone or with associated duraplasty the thick membrane covering the brain and spinal cord the removal of part of the vertebra to create more space this approach comes with risks and challenges possible cervical instability and cerebrospinal fluid leakage (pseudomeningocele) Applying an Effective Craniosynostosis Surgical Approach to Treating Chiari Malformation Type 1 Posterior cranial vault distraction osteogenesis (PVDO) is utilized routinely for treatment of multi-suture craniosynostosis a rare birth defect that occurs when one or more joints in a baby’s skull fuse together before the brain finishes developing The procedure is designed to expand the back of the skull Chiari malformation type 1 frequently occurs with craniosynostosis, and surgeons have found that performing PVDO improves symptoms of both conditions That is why after careful research and consideration we have started using a suboccipital PVDO surgical approach to treat appropriate patients who suffer only from Chiari malformation type 1 without craniosynostosis We believe suboccipital PVDO offers a safe option for these patients and can enhance their outcomes PVDO creates space but without having to cut into the dura or remove bone PVDO promotes the formation of new bone (ossification) in the posterior fossa allowing the cerebellum to unherniate itself thus creating more space as the skull grows Current published literature on the use of PVDO to treat Chiari malformation type 1 is limited to case reports and small retrospective case series. In 2022, one such report presented a case series of 9 patients with Chiari I malformations treated with distraction osteogenesis along with a novel technique to safely and effectively expand the posterior fossa while minimizing the risk of cerebellar ptosis All patients treated experienced improvements in prior presenting symptoms How Suboccipital Posterior Cranial Vault Distraction Osteogenesis is Performed When using suboccipital PVDO to treat patients with Chiari malformation type 1 the main goal is to create more space in the posterior fossa alleviating the compression and pressure on the cerebral tonsils and brainstem gradual distraction facilitates new bony growth which helps maintain the additional space posteriorly in the long-term While we continue to evaluate each case and enhance our approach to optimize treatment the basic suboccipital PVDO procedure on patients with Chiari malformation type 1 involves several key components: Effective provider and caregiver education on post-operative care is critical to alleviating complications and re-operation rates the suboccipital PVDO approach is only appropriate if they have not previously had PFD having PVDO does not preclude a patient from having PFD later if determined necessary our team works to ensure the scar is imperceptible and hair follicles eventually grow through the scar Improving Patient Outcomes and Helping Children Feel Whole we believe in taking a whole-person approach to the care we provide and our goal is to help every child return to just being a child I’m pleased to report that of the 8 suboccipital PVDO surgeries we have performed to date on children with Chiari malformation type 1 all have experienced complete resolution of their symptoms something her parents Krysta and Justin said had not happened before neuropathy and incontinence have also ceased she has no limitations on her physical activity and just started pre-K where her parents report she is performing at the top of her class in almost all subjects Paisley loves to dance and is working on perfecting her cartwheel She also enjoys playing soccer with her siblings and hopes to start karate soon Optimizing Care for Patients with Chiari Malformation Type 1 Our team remains committed to innovation that enhances care and optimizes outcomes for our patients With every suboccipital PVDO case we perform we are closely evaluating each step of the process to identify opportunities to refine our approach we are currently working to develop a new distractor device that we believe will better meet the specific needs of performing suboccipital PVDO on patients with Chiari malformation type 1 we recently conducted a systematic review of the published literature for PVDO as a treatment for Chiari malformation type 1 and our work has been accepted for publication in an upcoming issue of the Journal of Craniofacial Surgery we also hope to collaborate with other high-volume craniofacial centers on additional research efforts and to further refine techniques and protocols that will continue to transform the treatment of patients with Chiari malformation type 1 alleviating their symptoms and helping them to grow up healthy Our website uses cookies. Please review our privacy policy to find out more about the cookies we use Browsing our website means you accept these terms Please press and hold the button until it turns completely green If you believe this is an error, please contact our support team 147.45.197.102 : fef05703-0db6-4be1-9394-0850b413 More information for Referring Providers More information for Services & Specialties More information on Community Events More information on Giving Chiari Starling faced a serious health issue Doctors had prenatally diagnosed him with gastroschisis a rare condition — affecting 3 to 4 of every 10,000 children — in which infants are born with a portion of their intestines outside of the abdomen “We didn’t know the severity or the complication that it would have on his life,” said Chiari’s aunt and legal guardian he was taken to the operating room to have his intestines put back in his abdomen Chiari recovered well from the surgery and remained in the hospital for about two months Chiari’s medical team and family worked on feeding him through intravenous (IV) fluids and helping him grow appropriately and then worry that he was so young and tender and having to go through something like that,” Crystal recalled Chiari was brought back to the hospital — critically ill He was soon diagnosed with necrotizing enterocolitis (NEC) a condition that is characterized by necrosis NEC is another rare and life-threating condition that affects 1 to 3 babies every 1,000 births It’s usually diagnosed in infants who are born prematurely When Chiari was taken to the operating room the surgeon found that Chiari only had 11 centimeters of small bowel — massively below the 200-250 centimeter average for a child at birth It was such a small amount that the surgeon remarked in his operative note that he feared it was “incompatible with life.” Chiari faced a third diagnosis caused by NEC: ultrashort bowel syndrome (USBS) a condition where the length of bowel is less than 10 percent of what is expected for a particular age Approximately one third of infants with USBS have died by the time they’re 6 years old Surviving infants are faced with a 47 percent chance of their bowel being able to absorb all the nutrients it needs to live and being about to wean off the IV Many of these patients had more bowel than Chiari Chiari faced the strong possibility of having to continue to rely on an IV for nutrition for his entire life which can be further complicated by serious blood stream infections and loss of central venous access options over time Chiari continued to show great resilience for being so young and fragile and quickly recovered from this surgery although he had to receive all of his nutrition through IV the time he spent in the hospital was overwhelming and scary “At times I felt like there was no hope,” shared Crystal It seemed to be an uphill battle with no end in sight: Chiari was hospitalized 15 times in the first two years of his life with complications associated with his central line He had suffered life-threatening infections and the ability to feed him was severely limited due to his inability to absorb nutrients in what was left in his intestine Due to the ongoing need for IV-based nutrition, he was diagnosed with intestinal failure. In an attempt to improve his condition, Derek Wakeman, M.D. assistant professor in the Department of Surgery, and Walter Pegoli Jr., M.D. performed a serial transverse enteroplasty procedure (STEP) to surgically lengthen Chiari’s intestine when he was 10 months old STEP is an innovative procedure that was first introduced in the medical field in 2002 and requires advanced surgical expertise Doctors also connected the small intestine to what was left of Chiari’s colon to take advantage of the water absorption there Chiari wasn’t allowed to stay home because of the treatment he needed which required a tube in his stomach to suck out the contents because his intestine wasn’t working Chiari was able to steadily improve with feeding and close-monitoring that required meticulous care both in and out of the hospital Due to the tireless efforts of the GCH caregiving team and the support of Crystal Chiari was able to be taken off the IV and start eating regularly by his third birthday and now he now has no tubes at all and is thriving “Being able to wean off total parenteral nutrition completely in such a relatively short period of time after having only 11 centimeters of small bowel left is truly remarkable,” said Wakeman “We know that there are certain foods that can enhance the bowel’s ability to adapt after massive bowel resection I think this is a testament to the intestinal failure team and his family for really encouraging him to eat a variety of healthy foods.” “Here at Golisano Children’s Hospital we are privileged to be able provide advanced care for patients with intestinal failure,” said Megan Gabel, M.D. assistant professor in the Division of Pediatric Gastroenterology “We have all of the key elements needed to consistently deliver optimal care for these children A strength of our program is the multidisciplinary team that finds joy in treating complex patients like Chiari.” Both doctors and Chiari’s family credit his survival to the “village of providers” that helped care for him “I couldn’t ask for a better team to have worked with,” said Crystal Chiari does have some lifelong effects from his conditions and treatment His left leg is a little longer than his right leg because of a complication with blood flow during his hospitalization But he recently got a “lift” for his shoe and wears a brace when he’s active and when you ask Crystal how he’s doing now and engaging in the general silliness of a being a young boy: “He likes to dance and loves gorillas He thinks he’s King Kong and talks about going to the moon every day,” says Crystal He has certainly left a positive impression on his medical team at Golisano Children's Hospital Read more stories about our amazing Miracle Kids! » ©2025 University of Rochester Medical Center Rochester Unlock discounted publishing that highlights your organization and the peer-reviewed research and clinical experiences it produces Find out how channels are organized and operated including details on the roles and responsibilities of channel editors Offering a variety of advertising and sponsorship options for reaching influential specialists from targeted demographic splits efficient publishing and peer reviewing experience without sacrificing publication times Generate broad awareness and deliver relevant peer-reviewed clinical experiences directly to potential customers Dedicated Cranial Radiosurgery: Clinical Experience with New & Innovative SRS Technologies Real-Time Adaptive Motion Management on Helical and Robotic RT Platforms Please note that by doing so you agree to be added to our monthly email newsletter distribution list shed light on how Chiari malformation arises by Tamara Bhandari•December 28 The lowest part of a child's brain is visible below the bottom of the skull in this MRI scan and shows evidence of a Chiari 1 malformation Researchers at Washington University School of Medicine in St Louis have shown that Chiari 1 malformation can be caused by variations in two genes linked to brain development and that children with large heads are at increased risk of developing the condition About one in 100 children has a common brain disorder called Chiari 1 malformation but most of the time such children grow up normally and no one suspects a problem but scientists have understood little about the genetic alterations that contribute to the condition scientists at Washington University School of Medicine in St Louis have shown that Chiari 1 malformation can be caused by variations in two genes involved in brain development The condition occurs when the lowest parts of the brain are found below the base of the skull The study also revealed that children with unusually large heads are four times more likely to be diagnosed with Chiari 1 malformation than their peers with normal head circumference 21 in the American Journal of Human Genetics could lead to new ways to identify people at risk of developing Chiari 1 malformation before the most serious symptoms arise It also sheds light on the development of the common but poorly understood condition “A lot of times people have recurrent headaches, but they don’t realize a Chiari malformation is the cause of their headaches,” said senior author Gabriel Haller, PhD not everyone is willing to have brain surgery to fix it and the first step to better treatments is a better understanding of the underlying causes.” If people start experiencing severe symptoms like chronic headaches the malformation is treated with surgery to decompress the Chiari malformation “There’s an increased risk for Chiari malformations within families but nobody had really identified a causal gene,” Haller said “We were able to identify two causal genes and we also discovered that people with Chiari have larger head circumference than expected it might be worth checking with your pediatrician.” a professor of neurology and director of the Division of Pediatric and Developmental Neurology Sequencing revealed that people with Chiari 1 malformation were significantly more likely to carry mutations in a family of genes known as chromodomain genes meaning the mutation had occurred in the affected person during fetal development and was not present in his or her relatives the chromodomain genes CHD3 and CHD8 included numerous variants associated with the malformation transparent zebrafish showed that the gene CHD8 is involved in regulating brain size When the researchers inactivated one copy of the fish’s chd8 gene the animals developed unusually large brains Chromodomain genes help control access to long stretches of DNA thereby regulating expression of whole sets of genes Since appropriate gene expression is crucial for normal brain development variations in chromodomain genes have been linked to neurodevelopmental conditions such as autism spectrum disorders “It’s not well known how chromodomain genes function since they have such a wide scope of activity and they are affecting so many things at once,” Haller said “But they are very intriguing candidates for molecular studies to understand how specific mutations lead to autism or developmental delay or just to increased brain size without cognitive or intellectual symptoms We’d like to figure out the effects of each of these mutations so that in the future if we know a child has a specific mutation we’ll be able to predict whether that variant is going to have a harmful effect and what kind.” The association between chromodomain genes and head size inspired Haller and colleagues to measure the heads of children with Chiari malformations comparing them to age-matched controls and to population averages provided by the Centers for Disease Control and Prevention Children with Chiari tended to have larger than average heads Those children with the largest heads – bigger than 95% of children of the same age – were four times more likely to be diagnosed with the malformation The findings suggest that children with larger heads or people with other neurodevelopmental disorders linked to chromodomain genes may benefit from screening for Chiari malformation “A lot of kids that have autism or developmental disorders associated with chromodomain genes may have undiscovered Chiari malformations,” Haller said Discovering the condition early would allow us to watch knowing the potential for serious symptoms is there and perform that surgery as soon as it’s necessary.” Rare and de novo coding variants in chromodomain genes in Chiari I malformation This study was funded by Sam and Betsy Reeves and the Park-Reeves Syringomyelia Research Consortium; the University of Missouri Spinal Cord Injury Research Program; the Children’s Discovery Institute of St Louis Children’s Hospital and Washington University; the Washington University Institute of Clinical and Translational Sciences grant number UL1TR000448 from the National Center for Advancing Translational Sciences of the National Institutes of Health (NIH); the Eunice Kennedy Shriver National Institute of Child Health & Human Development award number U54HD087011 to the Intellectual and Developmental Disabilities Research Center at Washington University; the Swiss National Science Foundation grant number 31003A_182632; and the Jérôme Lejeune Foundation martinju@wustl.edu Tamara Bhandari tbhandari@wustl.edu Metrics details Chiari malformation type I (CM-I) is the most common subtype of Chiari malformation which can lead to brainstem compression and alterations in cerebrospinal fluid (CSF) flow Common complications in patients undergoing traditional surgical approach include pseudomeningocele The authors present a new minimally invasive surgery technique for protection and strengthening of the myodural bridge (MDB) in order to prevent the postoperative complications A retrospective study was performed on 55 CM-I patients undergoing surgical treatment from January 2019 to April 2024 in a center These patients underwent the surgical procedure of either posterior fossa decompression with duraplasty and tonsillar coagulation (PFDDC) or PFDDC with protection and strengthening of the MDB (PFDDC + MDB) The clinical outcomes and complications of the two procedures Overall complications rates were significantly reduced in the PFDDC + MDB group (3.8% vs Meningitis was observed in 3 (10.3%) in the PFDDC group and 1 (3.8%) in the PFDDC + MDB group (P = 0.613) Pseudomeningocele was more frequent in the PFDDC group than in the PFDDC + MDB group (24.1% vs There were no statistical differences in symptom improvement between the two groups PFDDC + MDB seems to be a safe and effective treatment for CM-I patients with or without syringomyelia This new procedure can bring clinical improvement and lower complication rates The methods for reducing CSF leak and chronic headache after surgery are still unclear Schematic presentation of the myodural bridge complex Posterolateral illustration of the craniocervical junction The myodural bridges are seen connecting the cervical spinal dura mater to the suboccipital muscles (red arrow) They proposed that the three sources of fibers should be protected during cervical surgeries to prevent dura damage we established an MDB-protecting concept and sought a novel surgical approach to preserve the structures and functions of the MDB The aim of this study was to analyze the outcome of a less invasive PFD using an MDB-protecting technique in CM-I 55 patients with symptomatic CM-I underwent surgical treatment by the same surgeon at our hospital Posterior fossa decompression with duraplasty and tonsillar coagulation (PFDDC) was performed in 29 patients while 26 patients underwent PFDDC with protection and strengthening of the MDB (PFDDC + MDB) The diagnosis of CM-I was confirmed by MRI Patients with other types of Chiari Malformation acquired CM-I following normal or high-pressure hydrocephalus and craniovertebral instability requiring fusion at the time of decompression were excluded Duration of operation and hospitalization were collected All patients were followed up at 3 months after surgery The retrospective study was approved by the Ethics Committee for Clinical Research in Shenyang General Hospital of Northern Theater Command (Date: 20.06.2023 All methods were carried out in accordance with relevant guidelines and regulations The informed consent was waived by the Ethics Committee for Clinical Research in Shenyang General Hospital of Northern Theater Command as the data for this study was taken from a hospital data which is not publicly available Patient confidentiality was protected by anonymizing all records prior to analysis Identifiable information was replaced with unique codes and the master list linking these codes to patient identities was securely stored with restricted access Only authorized researchers involved in the study had access to the data and all team members signed confidentiality agreements PFDDC was conducted between January 2019 and May 2022 guided by the new theory of the function of the MDB the main surgeon has decided to adopt PFDDC + MDB for all CM-I patients to avoid potential complications Surgeries were performed in the prone position with the three-point pin head fixation A 5 to 6 cm midline skin incision extending from the inion to the atlas (C1) was made in the atlanto-occipital region to expose the foramen magnum In the PFDDC group (Fig. 2a) a standard subperiosteal dissection of muscle from the inferior aspect of the occipital bone and the arch of the C1 was performed followed with a 25–30 mm suboccipital craniectomy and C1 laminectomy The posterior atlanto-occipital membrane was removed and the dura was incised under a microscope in a Y-shaped fashion View of the posterior occipito-cervical junction during posterior fossa decompression with duraplasty and tonsillar coagulation with protection and strengthening of the myodural bridge (PFDDC+MDB) (a) After retracting the suboccipital muscles bilaterally the occipital bone (triangle) and foramen magnum were exposed without removing the posterior arch of the atlas (blue arrow) and the attachment of the rectus capitis posterior minor (RCPmi) The MDB (green asterisk) was clearly visualized (b and c) After a 25–30 mm suboccipital craniectomy an incision was made strictly on the posterior atlanto-occipital membrane and the dura at the atlanto-occipital gap along the midline The MDB fibers were preserved at the same time The dura at the lower edge of the incision was sutured with the RCPmi to strengthen the MDB (yellow arrow) The underlying arachnoid and the tonsils (red asterisk) could be seen (d and e) After exploring the foramen of Magendie tonsil coagulation or subpial resection was performed (f) The duraplasty was performed with synthetic dural substitute (blue asterisk) and watertight sutures The intradural surgical procedures were same in both groups Tonsil coagulation or subpial resection was performed to the lowermost end of the tonsil especially in cases with herniation of cerebellar tonsils below the posterior arch of the C1 This could be improved by adjusting microscope angle and performing gradual tonsil coagulation and subpial resection After completing the duraplasty using synthetic dural substitute with No 5 − 0 Prolene suture and reinforcement with fibrin sealant (Porcine Fibrin Sealant Kit the outer layers were carefully sutured step-by-step Patients were transferred to the neuro intensive care unit postoperatively All statistical analyses were performed using R software (version 4.2.2) Independent samples t-test and Wilcoxon rank-sum test were utilized for the continuous variables comparisons between groups were performed using Chi-squared test For indices measured both preoperatively and three months postoperatively an analysis of covariance (ANCOVA) was applied A P value < 0.05 was considered significant To validate the adequacy of the sample size a post-hoc power analysis was conducted using G*Power software (version 3.1.9.7) A two-tailed z-test was performed with a significance level of 0.05 The total sample size of 55 cases provided an achieved power of 80.3% in estimating the rate of complication based on the observed rate in this cohort With regard to postoperative complications (Table 3) overall complications were significantly reduced in the PFDDC + MDB compared with that in the PFDDC group (3.8% vs Meningitis was observed in 4 (7.3%) of the overall cohort with 3 (10.3%) in the PFDDC group and 1 (3.8%) in the PFDDC + MDB group (P = 0.613) PMC was more frequent in the PFDDC (24.1%) than in the PFDDC + MDB (0%) group (P = 0.011) Pre- (a) and post-operative (b) T2-weighted sagittal MRI of the occipito-cervical junction in a 65-year-old male who underwent posterior fossa decompression with duraplasty and tonsillar coagulation with protection and strengthening of the myodural bridge (PFDDC+MDB) for pain and weakness in left upper limb The MRI images revealed an obvious decrease in syrinx size Postoperative 3D reconstruction CT (c) showed the adequate decompression range of posterior cranial fossa and the preservation of the posterior arch of the atlas This study described a novel surgical approach (PFDDC + MDB) for CM-I and showed the early outcome of a retrospective cohort study comparing PFDDC + MDB with regular PFDDC surgery This new procedure significantly reduced the postoperative complications All patients in the PFDDC + MDB group achieved good outcome in short-term follow-up and SDM will structurally aid in force transmission Traditional PFD procedures often lead to MDB damage and impair its ability to relieve tensile stress concentration on the dura which result in PMC or CSF leak after surgery removing the posterior arch of the C1 and the attachment of RCPmi on the C1 can expand the volume of the postoperative epidural space meticulous surgical approach for MDB preservation is required so as to avoid CSF leak We believe that MDB dysfunction is one of the causes of headache in CM-I patients In order to reduce the incidence of CSF-related events caused by traditional PFD procedures Protection and strengthening of the MDB protection are carried out with regular PFDDC in the study Key techniques for protection and strengthening of the MDB include (1) preserving the origin and insertion points of the RCPmi and the posterior arch of C1 (2) protecting the PAOM and the MDB fibers (3) midline incision of the PAOM and the dura at the atlanto-occipital gap and (4) suturing the dura at the lower edge of the incision with the RCPmi Overall complication rates of the PFDDC + MDB group significantly decreased compared with that of the PFDDC group (3.8% vs or revision surgeries in patients underwent PFDDC + MDB similar outcomes were presented in the two groups the new approach minimized the extent of the procedure and reduced the volume of the postoperative epidural space the present results showed that PFDDC + MDB was a useful surgical approach for CM-I with or without syringomyelia Clinical improvement and lower rate of CSF leak could be achieved through protection and strengthening of the MDB Preserving the roles of the MDB in CSF circulation and reducing the amount of suture edge tension as well as providing adequate intradural decompression named this space as the “occipito-atlantal cistern (OAC)” They supposed that the OAC and the cisterna magna may act as a buffer zone for CSF dynamics stability in both cranial cavity and spinal canal at the OCJ The main pathological lesions and surgical area of CM-I occurred at the OAC We considered that PFDDC + MDB provided a wide decompression space at the OCJ composed of the OAC and the cisterna magna the MDB promotes the CSF flow in the space and decreases pressure on the dura which can reduce the occurrence of CSF leakage and chronic headache The PFDDC + MDB approach emphasizes the protection of MDB balancing the reduction of complications and obtaining sufficient decompression and reduces the volume of the postoperative epidural space providing a new option for CM-I with syringomyelia the principles of MDB protection described in this study may extend to other procedures at the OCJ such as surgeries for basilar invagination or atlantoaxial instability the integrity of the dura mater and CSF dynamics also need to be carefully considered which indicates that the concept of MDB protection can be more widely used The small sample size limits the generalizability of the results a post-hoc power analysis was performed to confirm sufficient statistical power to detect significant differences in complication rates there are potential selection and reporting biases particularly due to the shift in surgical technique during the study period Patient selection and one experienced doctor may amplify the effectiveness of the new surgical procedure the study included a diverse patient group and employed validated outcome measures and statistical adjustments but the early postoperative outcomes showed the advantage of PFDDC + MDB and reported our preliminary achievements in CM-I surgery Subsequent multicenter prospective studies with large sample size and longer follow-up periods are needed to validate these findings and evaluate long-term outcomes we introduce a novel surgical approach for CM-I with or without syringomyelia Given that traditional surgical methods can lead to complications such as CSF leak and postoperative headache due to MDB damage PFDDC + MDB seems to be an effective treatment & Chiari Malformations A review of the current literature Definition of the adult Chiari malformation: a brief historical overview Long-term follow-up of Chiari-related Syringomyelia in adults: analysis of 157 surgically treated cases Surgical treatment of Chiari I malformation–analysis of intraoperative findings and outcome for 371 foramen magnum decompressions Adult Chiari I malformations: an analysis of surgical risk factors and complications using an international database Persistent/Recurrent Syringomyelia after Chiari decompression-natural history and management strategies: a systematic review Significance of Pseudomeningocele after decompressive surgery for Chiari I malformation Configuration of the connective tissue in the posterior atlanto-occipital interspace: a sheet plastination and confocal microscopy study Patterns of attachment of the myodural Bridge by the rectus capitis posterior minor muscle Anatomical connection between the rectus capitis posterior major and the dura mater The obliquus capitis inferior myodural Bridge Histological examination of the human obliquus capitis inferior myodural Bridge Definition of the to be named ligament and vertebrodural ligament and their possible effects on the circulation of CSF A proposed etiology of cervicogenic headache: the neurophysiologic basis and anatomic relationship between the dura mater and the rectus posterior capitis minor muscle A comparison of spindle concentrations in large and small muscles acting in parallel combinations an important contributor to human cerebrospinal fluid circulation Head-nodding: a driving force for the circulation of cerebrospinal fluid and physiological function of the suboccipital myodural connections Scanning Electron microscopic observation of myodural Bridge in the human suboccipital region Anatomical study on the connections between the suboccipital structures and the spinal dura mater A new concept of the fiber composition of cervical spinal dura mater: an investigation utilizing the P45 sheet plastination technique Compromised Cranio-Spinal suspension in Chiari malformation type 1: A potential role as secondary pathophysiology The relationship between compensatory hyperplasia of the myodural Bridge complex and reduced compliance of the various structures within the cranio-cervical junction A novel scoring system for assessing Chiari malformation type I treatment outcomes Syringomyelia-Chiari complex: magnetic resonance imaging and clinical evaluation of surgical treatment The addition of duraplasty to posterior fossa decompression in the surgical treatment of pediatric Chiari malformation type I: a systematic review and meta-analysis of surgical and performance outcomes Posterior fossa decompression with duraplasty in Chiari malformation type 1: a systematic review and meta-analysis Efficacy of posterior Fossa decompression with duraplasty for patients with Chiari malformation type I: A systematic review and Meta-Analysis Comparison of results between posterior Fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation type I: A systematic review and Meta-Analysis Dual dural patch graft with alloderm and duragen underlay for duraplasty in Chiari malformation results in significantly decreased cerebrospinal fluid leak complications Incidence and management of postoperative Pseudomeningocele and cerebrospinal fluid leak after Chiari malformation type I decompression Pseudomeningocele formation following Chiari decompression: 19-year retrospective review of predisposing and prognostic factors Surgical experience in 130 pediatric patients with Chiari I malformations Symptomatic Chiari malformations: an analysis of presentation Complications and outcomes of posterior fossa decompression with duraplasty versus without duraplasty for pediatric patients with Chiari malformation type I and Syringomyelia: a study from the Park-Reeves Syringomyelia research consortium Surgical outcomes after posterior fossa decompression with and without duraplasty in Chiari malformation-I Comparison of dural peeling versus duraplasty for surgical treatment of Chiari type I malformation: results and complications in a monocentric patients’ cohort The pathogenesis of Chiari I malformation and Syringomyelia A valuable subarachnoid space named the occipito-atlantal cistern Minimally invasive subpial tonsillectomy for Chiari I decompression Atlantoaxial fixation for treatment of Chiari formation and Syringomyelia with no craniovertebral bone anomaly: report of an experience with 57 cases Posterior fossa decompression with or without duraplasty in the treatment of paediatric Chiari malformation type I: a literature review and meta-analysis High long-term symptomatic recurrence rates after Chiari-1 decompression without dural opening: a single center experience Download references The authors acknowledge Wei-kai Zhu and Song Tao for wonderful suggestions in designing the present study and An-ying Wang for assistance in data collection This study was supported by National Natural Science Foundation of China (NSFC 32100928 awarded to Xiao-Ying Yuan) Innovation Support Project for Science and Technology Talent of Dalian (2023RG003 awarded to Hong-Jin Sui) and Key R&D Project of Liaoning Province (2020JH/1050004 awarded to Sheng-Bo Yu) Dong-Sheng Pan and Kai-Qi Yang contributed equally to this work General Hospital of Northern Theater Command China Denmark Joint Research Center for Biological Plastination Technique and Dong-Sheng Pan contributed to conceived and designed the experiments and Zhen Wang contributed to performing the experiments Dong-Sheng Pan and Kai-Qi contributed to analyzing the data and the drafting of the manuscript and Xiao-Ying Yuan contributed to funding acquisition and Xiao-Ying Yuan contributed to the critical revision of the manuscript Below is the link to the electronic supplementary material Download citation DOI: https://doi.org/10.1038/s41598-025-92506-7 Sorry, a shareable link is not currently available for this article. Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily. The Chiari II is a relatively common birth defect that is associated with open spinal abnormalities and is characterized by caudal migration of the posterior fossa contents through the foramen magnum. The pathophysiology of Chiari II is not entirely known, and the neurobiological substrate beyond posterior fossa findings remains unexplored. We aimed to identify brain regions altered in Chiari II fetuses between 17 and 26 GW. We used in vivo structural T2-weighted MRIs of 31 fetuses (6 controls and 25 cases with Chiari II). The results of our study indicated altered development of diencephalon and proliferative zones (ventricular and subventricular zones) in fetuses with a Chiari II malformation compared to controls. Specifically, fetuses with Chiari II showed significantly smaller volumes of the diencephalon and significantly larger volumes of lateral ventricles and proliferative zones. We conclude that regional brain development should be taken into consideration when evaluating prenatal brain development in fetuses with Chiari II. Volume 17 - 2023 | https://doi.org/10.3389/fnana.2023.1116948 This article is part of the Research TopicWomen in NeuroanatomyView all 10 articles Introduction: The Chiari II is a relatively common birth defect that is associated with open spinal abnormalities and is characterized by caudal migration of the posterior fossa contents through the foramen magnum The pathophysiology of Chiari II is not entirely known and the neurobiological substrate beyond posterior fossa findings remains unexplored We aimed to identify brain regions altered in Chiari II fetuses between 17 and 26 GW Methods: We used in vivo structural T2-weighted MRIs of 31 fetuses (6 controls and 25 cases with Chiari II) Results: The results of our study indicated altered development of diencephalon and proliferative zones (ventricular and subventricular zones) in fetuses with a Chiari II malformation compared to controls fetuses with Chiari II showed significantly smaller volumes of the diencephalon and significantly larger volumes of lateral ventricles and proliferative zones Discussion: We conclude that regional brain development should be taken into consideration when evaluating prenatal brain development in fetuses with Chiari II characterizing the regional growth and development of transient fetal zones in Chiari II may be relevant to a better understanding of its pathophysiology it is highly likely that something else explains worse neurodevelopmental outcomes for some cases Fetal MRI is currently used to quantify regional brain volumes and characterize normal (Vasung et al., 2019, 2021) and abnormal brain development (Rollins et al., 2021) the aim of our study was to use fetal MRI to characterize the differences in spatiotemporal brain maturation between Chiari II malformation and normal fetal controls which could serve as potential biomarkers of neurodevelopmental outcome in the future The study was approved by the institutional review board Due to the low prevalence and frequent association of Chiari II with brain and body abnormalities the exclusion criteria were related to acute/subacute and chronic brain injury resulting from hypoxic/ischemic insults (e.g. For the age- and sex-matched control group, we used fetal MRIs of women with healthy pregnancies who were prospectively recruited for previous studies (Gholipour et al., 2017; Rollins et al., 2021) Inclusion criteria for controls were the following: no serious maternal medical conditions (drug dependence fetal gestational age matching the age of cases fetuses recruited prospectively as controls in other research studies and fetuses with MRI acquired for reasons other than suspected malformation or injury of the central nervous system that was read by both pediatric radiologists (body) and neuroradiologists (neuro) as normal Exclusion criteria for controls included multiple gestation pregnancies dysmorphic features on ultrasound (US) examination brain malformations or brain lesions identified on the US other identified organ anomalies on the US and referral to MRI due to the suspicion of central nervous system injury or malformation we included only the subjects whose fetal MRI and outputs of the MRI processing pipeline (quality of 3D reconstruction and segmentation) passed our quality check All exams were performed on a 3T Siemens Skyra MRI except for one exam performed on a 3T GE Signa MRI with 18 or 30 channel body coils and included T2-weighted half-Fourier acquired single-shot turbo spin-echo (HASTE) scans along orthogonal planes T2 HASTE parameters were the following: slice thickness 2−3 mm acquisition matrix size 256 × 256 mm diencephalon (thalamus and subthalamic nucleus) The segmentations were used to calculate volumes for the left and right sides of the five regions for each subject Each subject provided a set of 10 volume measurements (5 regions the measurements were repeated by a second rater The data were log-transformed for analysis to eliminate skew and facilitate the expression of the findings from smaller and larger regions on a common ratio scale We fitted the data with a repeated-measures regression model consisting of the region- and hemisphere-specific mean log volumes; a region-specific fixed effect describing the ratio between Chiari and control volumes; covariate adjustment for gestational age; an interaction term adjusting for region-specific left-right differences; and random effects to account for rater variability and correlation among the 5 regions within-subject Sex was not included as a covariate because of missing information in 2 Chiari subjects and uncertainty about balance in the control group The total of 450 data points provided 433 residual degrees of freedom for the region-specific comparison between Chiari II and control volumes We applied robust regression to identify outliers and down-weight extreme values using the bisquare weighting function with 99% efficiency Contrasts estimated on the log scale (X ± SE) were retransformed to percentages for reporting [100% × (10X–1) ± 100% × 10X × (10SE–1)] Results were illustrated with box plots showing raw data with median and “whiskers” delimiting the range of non-outliers Dice’s coefficient was used to evaluate the overlap between segmentations edited by the two raters we included 25 Chiari II subjects (12 females and 2 with no sex reported on MRI or ultrasound) and six controls (2 females and 4 males) The remaining Chiari II subjects were excluded due to poor segmentation or MRI quality The mean age of the Chiari II subjects included in our study was 20.35 ± 1.65 GW The mean age of control subjects was 21.38 ± 1.51 GW There was no significant difference in age between Chiari II and the control group 15 had abnormalities of telencephalon [abnormalities of corpus callosum including dysgenesis subependymal gray matter heterotopia (N = 2) and 2 had visible abnormalities of the diencephalon (prominent massa intermedia) 13 had abnormalities of bones [flattening of frontal bones (N = 10) or meninges absent septum pellucidum or defects of septal leafs (N = 2)] all subjects included in our study had abnormalities of the spine [open spinal dysraphism (N = 25)] and spinal cord [myelomeningocele (N = 22) and hydrosyringomyelia (N = 1)] most commonly at lumbar or lumbosacral level Additional abnormalities (aside from posterior fossa findings) were found on fetal MRI in Chiari II fetuses To evaluate the overlap between structure segmentation of the two raters Dice similarity coefficient was calculated between the two raters’ structure segmentations in all subjects and then averaged across subjects Mean Dice was as follows: Diencephalon left = 90% and right = 91% lateral ventricle left = 96% and right = 96% cerebral hemisphere left = 87% and right = 87% proliferative zone left = 79% and right = 80% and ganglionic eminence left = 94% and right = 93% 25 Chiari II) provided 80% power to detect a true underlying difference as small as 25−30% Boxes indicate the median and interquartile range (IQR) with vertical lines extending to the last data point within a distance of 1.5 × IQR from the quartile boundary The percentage difference between mean Chiari and control volumes is indicated with standard error and test of statistical significance derived from repeated-measures regression analysis The volume of segmented clusters in the Chiari II and controls [cc] and comparison between two groups (% difference) with standard errors (SE) we used fetal MRI and an innovative fetal MRI processing approach (semiautomatic MRI segmentation based on fetal MRI atlases) to underpin differences in fetal brain development between Chiari II and controls that aside from the known dilatation of the lateral ventricles fetuses with Chiari II have significantly smaller volumes of the diencephalon and larger volumes of proliferative compartments (ventricular and subventricular zones) Although dilatation of lateral ventricles is a frequent prenatal finding in Chiari II subjects, our study indicates that ventriculomegaly is not found in every fetus with Chiari II, at least between 17 and 23 GW (Figure 1) There are two potential explanations for our findings an atrial diameter ≥10 mm is used to diagnose fetal ventriculomegaly which is further classified into borderline (AD = 10 mm) atrial measurements are susceptible to errors due to the orientation of the axial plane given that the dysmorphic shape of lateral ventricles is a radiological hallmark of Chiari II it remains unclear whether the atrial diameter is the best measure to estimate the severity of its ventriculomegaly Secondly, the atrial diameter above the critical threshold (10 mm) shows only a moderate to weak linear relationship with the volume of the lateral ventricles (Kyriakopoulou et al., 2014) Because it captures only the posterior portion of the ventricles with small differences in diameter In our cohort, we observed a large variation in the volume of ventricles (spanning from normal to severe ventriculomegaly, Figure 1) Whether the severity of prenatal ventricular dilatation between 17 and 23 GW reflects different stages of Chiari II remains to be determined by future prospective studies that would take into account both linear and volumetric measurements of lateral ventricles This early egress of CSF from the cranium and spine likely leads to non-distension of the ventricles causing displacement of posterior fossa content whether the migration of posterior fossa content is the only consequence of the non-distension of ventricles remains unclear Future longitudinal fetal MRI studies and better animal models are warranted to answer this question Fetuses with Chiari II included in our cohort showed significantly larger volumes of proliferative compartments (ventricular and subventricular zone) This relationship between the increase in ventricular size and proliferative zones can be explained by considering mechanical and biological factors A simple increase in the diameter of a cavity (in this case ventricles) will lead to an increase in the surface of the cavity and to an increase in the volume of the ventricular lining (proliferative zones) if there is minimal change in thickness of proliferative zones cannot show if there is an increase in the ventricular pressure that would consequently lead to a thinning of the ventricular lining (the thickness of proliferative compartments is ∼1 mm) although we did observe a strong correlation between the volume of ventricles and proliferative zones we cannot identify which proliferative compartments (ventricular or subventricular zone) contribute the most to this increase in volume we cannot speculate about the biological causes behind the enlargement of proliferative zones seen in Chiari II our findings of enlarged proliferative compartments in Chiari II together with the results of the MOMS study indicate there is reasonable doubt that fetuses in Chiari II might have abnormal brain development that could underlie higher risk for the poor neurodevelopmental outcome In conclusion, despite the limitations imposed by fetal MRI, we suggest that the rate of prenatal increase in ventricular volumes, which affects the size of proliferative zones before 20 GW [i.e., while the majority of neuronal precursors are still being born and are migrating toward the final destination in the cortex (Bystron et al., 2008)] should be taken into consideration when characterizing fetal brain development in Chiari II we found significantly smaller volumes of the diencephalon in Chiari II Our study is the first to report this finding suggesting the vulnerability of this region the causes leading to the altered development of diencephalon in Chiari II remain to be determined we hypothesize that several pathophysiological mechanisms might lead to the altered development of the diencephalon altered cytoarchitectonic differentiation) it is possible that conditions such as Chiari II that are associated with spinal dysraphism lead to altered sensory signal transmission from the body and consequently altered maturation of structures that serve as their relay station (notably thalamus) since our study only addresses the volume differences between structures we acknowledge that the smaller volume of certain brain structures does not necessarily mean worse developmental and/or clinical outcomes future experimental animal and prospective human studies are needed to prove these hypotheses Such studies recognize that limited research exists comparing pre- and postnatal MRI for patients with Chiari II and emphasize the need for further investigation between MR imaging and the clinical significance of prenatal intervention there is an increasing need to continue to strengthen our understanding of the relationship between radiographic morphology and clinical severity associated with Chiari malformation so we can continue to optimize management within the pre- and postnatal periods guidelines for surgical intervention in fetuses are based on the severity of the malformation They do not consider additional body findings or changes in volume or volume trajectories of certain brain regions Further research is necessary to deepen our understanding of the neurodevelopmental and long-term outcomes of such procedures The retrospective design of our study is a limitation The most important to mention are unknown confounders and sources of bias that could affect the selection of Chiari II cases (e.g. socioeconomic status and access to prenatal care that is associated with higher rates of prenatal MRI) quality of prenatal MRI images (suboptimal quality of the clinically acquired MRI due to the short time of MRI acquisitions and low image resolution despite fetal movements) and segmentation algorithms (optimized for in utero MRI segmentation of fetuses older than 20 GW) since the majority of pregnancies included in the current study ended in termination or loss to follow-up future prospective and longitudinal imaging studies of Chiari II are warranted to better characterize brain development and disease stages in Chiari II that could be used to guide clinical decision-making and prenatal counseling prenatal MRI has a limited diagnostic value in detecting certain pathologies such as subependymal gray matter heterotopia postnatal MRI is warranted for more precise detection of subtle brain abnormalities The datasets presented in this article are not readily available because of retrospectively collected patient information. Requests to access the datasets should be directed to LV, bGFuYS52YXN1bmdAY2hpbGRyZW5zLmhhcnZhcmQuZWR1 The author stated that no potentially identifiable human images or data are presented in the manuscript The study was approved by the Institutional Review Board All authors contributed to the preparation of the manuscript This work was supported in part by the Harvard Catalyst (Five Senses Award) and NIH grants R01EB013248 and R01HD109395 and the Office of the Director of the NIH under award number S10OD025111 We thank patients and their families whose MRIs were used for this study The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations Any product that may be evaluated in this article or claim that may be made by its manufacturer 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Estroff, Grant and Vasung. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) distribution or reproduction in other forums is permitted provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited in accordance with accepted academic practice distribution or reproduction is permitted which does not comply with these terms *Correspondence: Olivia Masse, b2xpdmlhbWFzc2UyMDI0QHUubm9ydGh3ZXN0ZXJuLmVkdQ==; Emily Kraft, ZWtyYWZ0QG55aXQuZWR1; Lana Vasung, bGFuYS52YXN1bmdAY2hpbGRyZW5zLmhhcnZhcmQuZWR1 Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. 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Volume 5 - 2018 | https://doi.org/10.3389/fvets.2018.00171 Chiari-like Malformation (CM) and secondary syringomyelia (SM) as well as their analogous human conditions is a complex developmental condition associated with pain and accompanying welfare concerns thanks in part to the increased availability of magnetic resonance imaging in veterinary medicine Research over the last two decades has focused primarily on its pathophysiology relating to overcrowding of the cranial caudal fossa More recent characterizations of CM/SM include brachycephaly with osseous reduction and neural parenchymal displacement involving the entire brain and craniocervical junction to include rostral flattening reduced cranial base with spheno-occipital synchondrosis angulation reduced supraoccipital and interparietal crest and rostral displacement of the axis and atlas with increased odontoid angulation The most shared manifestation of CM is the development of fluid-filled pockets (syrinx syringes) in the spinal cord that can be readily quantified Dogs with symptomatic CM without SM have a reduced basioccipital bone compensatory increased cranial fossa height with displaced parenchyma whereby the cerebellum is invaginated beneath the occipital lobes but without compromising cerebrospinal fluid channels enough to cause SM CM might be described as any distortion of the skull and craniocervical junction which compromises the neural parenchyma and cerebrospinal fluid circulation causing pain and/or SM potentially including genetically-influenced breed-specific abnormalities in both skeletal and neural components Since causation between specific morphologic changes and SM or clinical signs is unproven CM might be more appropriately considered as a brachycephalic obstructive CSF channel syndrome (BOCCS) rather than a single malformation Understanding the normal development of the brain skull and craniocervical junction is fundamental to identifying deviations which predispose to CM/SM and genetic underpinnings to update the profession's understanding of this condition and meaningfully inform future research to diminish its welfare impact Although the working group agreed the acronym as CM/SM for Chiari-like malformation and secondary syringomyelia CLM has been used as an acronym for CM in some research articles to distinguish it from the corresponding human condition but further research is required to establish the pathophysiology of the pain associated with CM Mid-sagittal T2-weighted image of brain and cervical spinal cord of CKCS with CM and SM Yellow arrows indicate generalized skeletal variances from normal CKCS skull and cervical junction Red arrows indicate displaced neural parenchyma Schematic framework of selected CM traits (red lines) and “normal” traits (blue lines) to illustrate underlying anatomical differences in the caudal cranium and cranial cervical vertebrae The red (SM affected) lines are superimposed on those for representing normal (blue) and aligned along the skull base at fixed point “*” the dorsum of spheno-occipital synchondrosis is flexed dorso-caudally (“sphenoid flexure”) The cranial cervical vertebrae are more rostral angled ventrally with medullary elevation (“cervical flexure”) A considerable body of research has been undertaken worldwide to understand the relationship/s between CM and SM in an attempt to elucidate the pathogenesis of SM in the dog Attention has focused on secondary SM rather than CM Various morphometric studies measured alterations in volume and/or linear dimensions and/or angles of the cranium and craniocervical junction of dogs with and without CM/SM The conclusions of key studies summarized below reflect the depth and breadth of investigations rather than a comprehensive literature review on the morphometrics of CM/SM: • Caudal fossa was reduced in dogs with SM (34–37) • Cerebellar volume was greater in CKCS with CM/SM (38) and abnormal in dogs with CM/SM (37, 39, 40) compared to normal controls • There was no correlation between severity of cerebellar herniation and neurological signs (39) • There was a mismatch or rearrangement of neural parenchyma with SM-affected dogs (29, 35, 41, 42) • SM-affected young dogs developed more severe clinical signs and syringes that enlarge over time (43–45) • There was no difference in volumetric measurement of the neural parenchyma with changes in head position during MRI but there was a significant difference between the cerebellar herniation and CSF space between the cerebellum and brainstem which was larger in the flexed position (46) • Venous sinus volume in the caudal cranial fossa is reduced in CKCS with CM/SM compared to dogs with CM (47) and the skull base is reduced, with narrowing of the jugular foramina which theoretically could increase intracranial venous pressure and impair CSF absorption (18, 48) • CSF flow was impeded in dogs with CM/SM (26) and this could lead to a mismatch in the timing of arterial and CSF pulse waves predisposing to SM (49) • Maximum syrinx width was the strongest predictor of pain, phantom scratching and scoliosis in dogs with SM. Both pain and syrinx size were positively correlated with syrinxes located in the dorsal half of the spinal cord (50, 51) • Craniocervical junction abnormalities did not predict development or worsening clinical signs of SM but may contribute to them. These included atlantooccipital overlapping (52), atlantoaxial bands (53), and medullary elevation (54) • The presence of a CSF flow void in the mesencephalic aqueduct associated with ventricular enlargement and SM in dogs suggests CSF turburlence and possibly reduced intracranial compliance (55) Despite considerable variation in skull shape and body weight these breeds are accepted as being small in size but not all are recognized in the dog world as brachycephalic with obviously shortened craniofacial bones supporting the observation that brachycephaly affects the CSF channels In these respects CM/SM can be considered comparable to BOAS i.e. a Brachycephalic obstructive CSF channel syndrome (BOCCS) BOCCS can be considered any distortion of the skull and/or craniocervical junction that compromises the neural parenchyma and CSF circulation causing pain and/or SM with variation between breeds and individuals the range of craniocervical junction anatomical abnormalities associated with CM/SM highlight the multifactorial nature of this condition in dogs (and humans) How each of these assemblies develops in a coordinated manner during normal embryonic morphogenesis and post-natal growth remains poorly understood Embryology, as in human CM, provides the means to understanding the developmental inter-relations between the brain, derived from the neuroectoderm, and the skull, derived from mesodermal and neural crest cells (61, 92–94) The multipotent neural crest cells which delaminate from the dorsal neural tube contribute not only to the peripheral nervous system but also to the ectomesenchymal precursors that underpins the cranial skeleton and thus the potential to influence irregularities associated with CM the normal development of the neural and skeletal components are described to give context for identifying where any abnormalities arise that might influence CSF circulation with resultant CM and secondary SM Schematic diagram of the differentiation of vesicles in the developing brain The three stages in the development of the vesicles within the brain as changes in differential growth and proportions of the forebrain mid brain and hindbrain (1st and 2nd stages) are modified by flexures that still allow the continuity of the CSF channels within Stage 3 illustrates the formation of cerebellum and its relationship with the fourth ventricle and the cerebral aqueduct Schematic adult brain with ventricular system with enlarged fourth ventricle inset illustrating formation of CSF Red arrows indicate movement of filtrate from the venous system into the ventricles at the choroid plexus; Aqua arrows indicate movement of CSF through the ventricles to the subarachnoid space and central canal Inset: Transverse section of medulla oblongata (myelencephalon) illustrating relationship of the choroid plexus epithelium invaginated into the CSF space of the fourth ventricle and the blood/brain barrier and compliance with CSF drainage The canine skull, as in other vertebrates, is a product of its evolutionary origins whereby the loss of lateral walls of the neurocranium in both birds and mammals enabled the brain to expand into the dermal skull roof (115). Four skull components can be described [Figure 5, based on (115)] Neurocranium: trough-like skull base which has a primitive cartilaginous forerunner (chondrocranium) supporting the brain and sensory organs 2. Viscerocranium (splanchnocranium or orognathofacial complex): modified cartilaginous supports for the gill arches of early aquatic vertebrates associated with feeding but also part of the senses. In later evolutionary vertebrates these features contribute to the jaws, hyoid and inner ear bones (61, 116) Dermatocranium or cranial vault (calvaria): dermal or intramembranously-ossified bones which encase the telencephalon and the nose which originated from the bony head armor without a cartilaginous precursor 4. Sclerotomal occipital region: incorporation of the occipital vertebrae into the skull, supported by the annexation of the cranial part of the spinal cord into the brain, together with the first 2 spinal nerves as cranial nerves X1 and X11 (117) Diagram of the bones referred in text (lower jaw not illustrated) with arrows to indicate anatomical changes in dogs with CM The green colored bones are endochondral in origin (neurocranium of skull and notochord in axial skeleton) Calvaria and facial bones have membranous ossification (viscerocranium) craniocervical junction) indicated by red border interparietal and supraoccipital fuse (yellow arrow) The reduced volume of the caudal fossa in CM is indicated by the blue arrows: reduction of the supraoccipital and dorsal displacement of atlas and axis; premature closure of synchondroses of bones in skull base (blue*) shortening the skull base and compensatory increase in height of the parietal bone and frontal bone (red arrows) Constructed images using CT and MRI of the skull brain and craniocervical junction of a Chihuahua with CM and SM MRI and CT of a 5 year old female Chihuahua with CM and SM are used to construct images to illustrate the complexity of the skull craniocervical junction and neuroparenchymal malformation Fitzpatrick Referrals Ltd.) (A) cerebellum is invaginated under the occipital lobes with little space available for this organ Much of the atlas is rostral to the level of the occipital crest (B) caudal view of the skull with the supra-occipital bone missing either because it did not form in the first instance or was resorbed due to pressure necrosis Bottom row: (C) composite of midsagittal brain and cervical MRI and CT with the short skull base and complex craniocervical junction abnormality with overall reduction of volume loss of the cisterna magnum and medullary elevation over a dorsally angled den The overall complexity of the embryology of the skull and craniocervical junction has resulted in range of abnormities which results in a mismatch between the skull, craniocervical junction and neuroparenchyma that might compromise CSF circulation. The association of CM with craniofacial abnormalities that are paraxial mesoderm in origin and involve craniosynostosis is well documented in humans (9, 134) the desire and popularity to select and breed dogs that produce characteristic facial and breed specific features has resulted in breed-specific variations in suture/synchondrosis fusion which interfere with the natural morphogenetic processes of growth a property which is used clinically in fracture repair Although the majority of studies reported to date have focused on facial length rather than craniofacial index the large effect sizes identified raise the possibility that similar genetic pathways may influence risk of developing CM Robust phenotyping is essential for genetic investigation and further delineation of the genetic basis of canine CM/SM and potentially identify high-risk individuals at a very early age in order to allow selective monitoring or even the development of prophylactic targeted therapies This review reflects the key morphogenetic processes involved in CM/SM and how they relate to the most recent research findings for these conditions with respect to brachycephaly craniocervical junction abnormalities and diagnosis but highlighting the need for further investigation The challenge of quantifying and interpreting intermittent and variable clinical signs for a complex trait such as CM/SM cannot be overstated More investigation is required to defining the pathology of symptomatic CM and its relationship with brachycephaly and miniaturization This priority for future research can make a considerable and direct impact on dog welfare The genetic investigation for canine CM/SM has been carried out in conjunction with human studies and it reaffirms how “Man and his Dog” have an enduring partnership The progress made has been with the whole-hearted co-operation of breeders and pet owners supporting human sufferers of CM/SM under the umbrella “One Health.” CR: Concept; SK: Original draft and graphics; GG and CR: Editing and reviewing draft SK doctoral studies were funded by Cavalier Matters Charity http://cavaliermatters.org/ GG is funded by a Wellcome Trust Postdoctoral Clinical Research Training Fellowship (107474/Z/15/Z) and the Institute of Child Health is supported by the NIHR Great Ormond Street Hospital Biomedical Research Centre The views expressed are those of the author and not necessarily those of the NHS The authors would like to thank all the dedicated veterinary professionals breeders and pet owners worldwide who have supported research into CM/SM both in practical terms and financially We acknowledge their vital contribution towards knowledge and understanding of these complex conditions Dogs attending primary-care practice in England with clinical signs suggestive of Chiari-like malformation/syringomyelia Prevalence of asymptomatic syringomyelia in Cavalier King Charles spaniels Prevalence and heritability of symptomatic syringomyelia in Cavalier King Charles spaniels and long-term outcome in symptomatic and asymptomatic littermates Chiari—like malformation and syringomyelia CrossRef Full Text | Google Scholar Questionnaire-based behavior analysis of Cavalier King Charles spaniels with neuropathic pain due to Chiari-like malformation and syringomyelia Breeding and Welfare in Companion Animals Aspects of Modifications Through Selective Breeding or Breeding and Welfare in Companion Animals Chiari-like malformation: a substantive health and welfare problem in the Cavalier King Charles spaniel An update on the pathogenesis of syringomyelia secondary to Chiari-like malformations in dogs Syringomyelia: A Disorder of CSF Circulation Prevalence of Chiari-like malformations in clinically unaffected dogs Use of morphometric mapping to characterise symptomatic Chiari-like malformation secondary syringomyelia and associated brachycephaly in the Cavalier King Charles spaniel Persistent scratching in Cavalier King Charles spaniels PubMed Abstract | Google Scholar Behavioural and clinical signs of Chiari-like malformation and syringomyelia in cavalier King Charles Spaniels Birmingham: British Small Animal Veterinary Association Congress ISBN (2018) MRI characteristics for “phantom” scratching in canine syringomyelia 15. 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This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) *Correspondence: Susan P. Knowler, cy5rbm93bGVyQHN1cnJleS5hYy51aw== Landmark-based geometric morphometric techniques were used to asses CMI morphology in five anatomical planes of interest. Volume 18 - 2024 | https://doi.org/10.3389/fnana.2024.1434017 Background: Chiari I malformation (CMI) is characterized by inferior descent of the cerebellar tonsils through the foramen magnum and is associated with headache and neck pain Many morphometric research efforts have aimed to describe CMI anatomy in the midsagittal plane using classical measurement techniques such as linear dimensions and angles These methods are less frequently applied to parasagittal features and may fall short in quantifying more intricate anatomy with fewer distinct homologous landmarks Methods: Landmark-based geometric morphometric techniques were used to asses CMI morphology in five anatomical planes of interest Results: Significant shape differences between CMI and age/sex-matched controls were found in the midsagittal (Pseudo-F = 5.4841 p = 0.001) and axial planes through the rostral medulla (Pseudo-F = 7.6319 CMI principal component 1 (PC1) scores in the midsagittal protocol were associated with marked anterior concavity of the brainstem and generalized verticality of the cerebellum with anterior rotation of its anterior lobe CMI PC1 scores were associated with greater anterior–posterior (A-P) dimension with loss of medial-lateral (M-L) dimension Discussion: These results suggest that CMI is associated with greater curvature of the brainstem and spinal cord which may perturb normal neural activities and disrupt cerebrospinal fluid movements Previous reports on the A-P diameter of the posterior fossa in CMI have conflicted; our findings of greater A-P cerebellar dimensionality with concomitant loss of width alludes to the possibility that more caudal aspects of the posterior cranial fossa are more bowl-like (homogenous in axial dimensions) and less trough-like or elongated in the M-L direction Generalized Procrustes analysis serves to translate and rotate coordinate points to maximize superimposition and precedes downstream ordination techniques or group comparison Centroid size is the typical scale variable for GM analyses Many applications of these methods seek to connect allometric scaling to shape variation although other applications explicitly seek to exclude the element of size in deference to shape-only analysis Since less biological shape information is forfeited these techniques often offer a more nuanced quantification of form than that of traditional biometric methods We hope to build on these reports by increasing sample sizes using semilandmarks in greater density to increase resolution and adding four axial landmarking protocols A second primary aim is to address the relative dearth of research specifically designed to evaluate parasagittal characteristics of CMI In addition to the expected differences in tonsillar position a GM analysis will also reveal other locations of anatomical variability which may be appreciated in the midsagittal plane We predict that the congestion of the neural components around the foramen magnum and other osseous constraints in the posterior cranial fossa results in a ripple effect of deformation within the brainstem and cerebellum that may be detectable and describable by applying landmark-based GM techniques to neural elements visualized in axial sections Magnetic resonance imaging (MRI) studies of 94 Chiari-affected females and age/sex-matched controls were provided by the Chiari1000 database at the University of Akron Each deidentified patient file was imported into 3DSlicer (v.5.6.2) and assessed for resolution quality Visualization of the five landmarking protocols in 3D with corresponding 2D image for: (A) Midsagittal brainstem and cerebellum; (B) superior midbrain; (C) inferior midbrain; (D) pons/cerebellum; (E) medulla/cerebellum Colors on 3D model correspond with colors in MRI images Examples of discrete loci include single points that represent the intersection of tissues These point locations can be located accurately between scans PERMANOVA on all PC scores account for all related loadings between CMI and control groups for each protocol A Mann–Whitney U test was performed to test for differences between groups for PC1 scores for each protocol These results allow for direct comparison for higher impact PC axes so group-specific shape interpretations may be made Wireframe diagrams were created to visualize shape differences A total of 94 scans were included in this protocol (65 Chiari, 29 control). Principal component analysis for the midsagittal dataset revealed 93 principal components (PCs) with the first five eigenvalues accounting for 56.89% of the variance in the sample. Scores and shapes related to the first two PCs can be seen in Figure 2 The first principal component (PC1) captures 21.58% of the overall shape variation in the sample and is characterized by two notable shape features: first concavity/convexity of the brainstem from the midbrain through the upper cervical spinal cord and second the expected superior–inferior tonsillar movement Shape conformations related to PC2 (14.58%) included modest anterior–posterior (A-P) flattening/bulging of the brainstem with remarkable A-P displacement of the posterior lobe of the cerebellum more negative scores are associated with anterior displacement of the anterior lobe of the cerebellum resulting in a more vertically oriented primary fissure Gray wireframes represent the mean landmark configuration black wireframes represent shape changes along the respective PC axis This protocol was implemented for 77 individuals (54 Chiari, 23 control). The first PC accounted for 48.75% of the variation in the sample, whereas PC2 accounted for 20.65% (Figure 3A) Shape changes along PC1 are characterized by widening/narrowing of the cerebral peduncles leading to changes in the A-P dimensions of the midbrain Shape changes highlighted by PC2 (20.65%) included medio-lateral (M-L) changes to the tegmentum resulting in a more (or less) pronounced tectum A total of 88 scans were included in this protocol, including 65 Chiari and 23 controls. The shape characterized by PC1 (43.41%) was similar that of the superior midbrain, widening/narrowing of the cerebral peduncles with changes in the A-P dimensions along the midline (Figure 3B) Shape conformations related to PC2 (18.99%) were also similar to the results from the superior midbrain protocol including deep-set/protruding cerebral peduncles affecting overall tegmentum width and changes in the interpeduncular fossa Ninety scans were included in this landmarking protocol (66 Chiari, 24 control). The first PC accounted for 38.75% of the variation in the shape within the sample and was notable for concomitant inverse changes in the A-P and M-L dimensions (Figure 3C) The second PC (18.13%) highlighted changes in the relative size of the pons tissues around the cerebello-pontine angle and more prominent changes to the petrous surface of the cerebellum A total of 81 scans were landmarked in this dataset (57 Chiari, 24 control). The first PC accounted for 43.35% of the overall shape variation and is notable for an inverse relationship between the A-P and M-L dimensions of the medulla/cerebellum (Figure 3D) Similar to the results from the pons/cerebellum protocol PC2 (13.18%) showed that relatively larger medulla is associated with a cerebellum with a more prominent posterior M-L dimension whereas a more recessed medulla is associated with a cerebellum with more prominent anterior M-L dimension These negative scores were associated with reduced cerebellar width in favor of a greater A-P dimension which was most prominent at the cerebellopontine angle More positive scores along the medulla/cerebellum PC1 axis were associated with greater cerebellar width and reduced A-P dimension These results comport with our expectation that CNS shape deformation in the Chiari hindbrain may be detectable rostral to the typical area of interest around the foramen magnum Comparisons of the average Procrustes distance for each landmarked scan between the complete sample and its corresponding replicate set were significant for all groups (p < 0.001) (Figure 4) There was also much lower variation in each sample’s replicate group than in the complete sample The midsagittal group had a higher average Procrustes distance (0.060 ± 0.014) Simply having more landmarks or greater natural variability in structures in the midsagittal plane may have accounted for this finding the midsagittal replicate average was relatively low (0.013 ± 0.002) Comparison of Procrustes distances for each total sample and its corresponding replicate Bars represent median value for each group boxes show the interquartile range (25th to 75th percentile) and the extension of the whiskers represents 1.5 times the interquartile range All group comparisons are significant (p < 0.001 represented by ****) Beginning with early morphometric descriptions of the posterior cranial fossa, many efforts have focused on revealing linear and angular differences in Chiari populations (Nishikawa et al., 1997; Milhorat et al., 1999; Urbizu et al., 2014) our approach is to enhance the current understanding of the shape of the Chiari brainstem and cerebellum by applying landmark-based GM techniques Beyond exploring landmark configuration differences using PCA we also sought to test for shape differences between Chiari and age/sex matched controls The results of the PERMANOVA revealed significant differences between Chiari and control groups in the midsagittal plane and in axial section through the rostral medulla These local changes may also have a relationship with brainstem orientation Investigation into the relationship between shape conformation and the incidence of syringomyelia would further reveal the role of hindbrain shape in CMI CSF flow This skull base flattening with concurrent anterior inclination of the brainstem may be seen in CMI-only individuals without any other skeletal abnormalities around the craniocervical junction Aside from tonsillar changes, more negative midsagittal PC1 (21.58%) scores were also associated with generalized verticality of the cerebellum. Increased midsagittal cerebellar height has been previously reported in CMI patients (Biswas et al., 2019) Our results add greater resolution to the global midsagittal accommodations of the cerebellum showing that in CMI the posterior lobe tends to be far less deeply situated in the posterior cranial fossa while the anterior lobe is forced anteriorly with the primary fissure becoming less horizontally oriented Shape changes associated with midsagittal PC2 (14.58%) scores localize heavily on the posterior cerebellum We predicted the sensitivity of our methods would likely detect natural variability of the curvature of the posterior cerebellum it was much more difficult to account for this variation in a rigorous fashion that did not add unnecessary distortion to the results so instead we opted to anticipate this artifact in the results Our results suggest a more circular-shaped medulla/cerebellum in CMI as opposed to an oval medulla/cerebellum It is likely that the ultimate deformation of the CMI brainstem/cerebellum at this level is due to a multitude of influences including congestion at foramen magnum and other osseous constraints related to hypoplasia of the occipital bone It is important to consider that the shape in A-P and M-L dimensions illustrated by the results of the axial landmarking occurs concurrently with the shape in A-P and superior–inferior dimensions depicted by the midsagittal landmarking protocol The shape of the posterior cranial fossa may play an important role in pathology of CMI regardless of posterior fossa volume or metrics of scale It is possible that the more oval or “trough-like” medulla/cerebellum shape associated with the control group is a consequence of a similarly shaped posterior fossa which may offer more M-L cerebellar support As the CMI group was associated with a more circular medulla/cerebellum at that level a similarly shaped posterior fossa may act more like a funnel offering less support and functioning more like a drain Future morphological studies may specifically address these possibilities by targeting skeletal components The lack of significant differences between CMI and control groups in more superior landmarking configurations suggests that any gross compression or deformation forces on the natural outline boundary captured in the axial plane are diminished or negligible rostral to the pontomedullary junction Procrustes distances between each specimen and the mean configuration for each sample should be lower in a sample of replicates compared to a sample of different individuals the Procrustes distance would simply be a measure of error and therefore a useful proxy for the reliability of the landmarking strategy These results suggest the landmarking protocol was robust and yielded accurate measurements this research has revealed subtle features of the midsagittal CMI brainstem and cerebellum which may be difficult to ascertain without the aid of landmark-based GM techniques Some of these features corroborated previous evidence Additional morphometric interest in parasagittal CMI anatomy is an opportunity for future morphometric applications There are many limitations to this study which are important to acknowledge Although the strength of the methods lies in the amount of shape information retained by GM techniques they were nevertheless employed in two dimensions The outcomes of these landmarking strategies are only strictly applicable to the planes they are used to evaluate One must be cautious when extrapolating beyond these planes Despite the landmarkers being blinded to the identities of each scan and the results of the error studies being encouraging there is still an element of landmarking error introduced into the analysis our aims were not to evaluate skeletal components so speculations about the precise nature of the skeletal shape influencing the shape of the brainstem and cerebellum must be drawn with caution The datasets presented in this study can be found in online repositories. Datasets are available on Figshare online repository. Coordinates for all five datasets after sliding of semilandmarks – https://doi.org/10.6084/m9.figshare.25843861 and PC scores for all five datasets https://doi.org/10.6084/m9.figshare.25843885 This study involving humans was evaluated and approved by the institutional review board at the Edward Via College of Osteopathic Medicine (Project #1944161-1; VCOM IRB record #2022-049) The study was conducted in accordance with the local legislation and institutional requirements Written informed consent for participation was not required from the participants or the participants’ legal guardians/next of kin in accordance with the national legislation and institutional requirements The author(s) declare that financial support was received for the research This work was supported by the Edward Via College of Osteopathic Medicine (VCOM) Research Eureka Accelerator Program (REAP) grant # 22-0028 The authors like to show special gratitude to the individuals who released their imaging for research and to the Conquer Chiari Research Center for kindly supporting research that aims to improve the lives of patients and families impacted by Chiari malformation to the University of Akron for its role in imaging acquisition and management Magnetic resonance imaging measures of posterior cranial fossa morphology and cerebrospinal fluid physiology in Chiari malformation type I Crossref Full Text | Google Scholar Chiari type I malformations in adults: a morphometric analysis of the posterior cranial fossa Automated posterior cranial fossa volumetry by MRI: applications to Chiari malformation type I Crossref Full Text | Google Scholar Quantification of cerebellar crowding in type I Chiari malformation Google Scholar Landmark methods for forms without landmarks: morphometrics of group differences in outline shape Posterior cranial fossa morphometry in symptomatic adult Chiari I malformation patients: comparative clinical and anatomical study Ebrahimzadeh Diagnostic utility of parasagittal measurements of tonsillar herniation in Chiari I malformation Eppelheimer A retrospective 2D morphometric analysis of adult female Chiari type I patients with commonly reported and related conditions Basilar invagination: a study based on 190 surgically treated patients Crossref Full Text | Google Scholar Google Scholar Crossref Full Text | Google Scholar Normalization of hindbrain morphology after decompression of Chiari malformation type I The perplexity surrounding Chiari malformations – are we any wiser now A morphometric assessment of type I Chiari malformation above the McRae line: a retrospective case-control study in 302 adult female subjects Chiari I malformation with and without basilar invagination: a comparative study PubMed Abstract | Crossref Full Text | Google Scholar Google Scholar Cerebellar tonsil ectopia measurement in type I Chiari malformation patients show poor inter-operator reliability Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients Mitteroecker Thirty years of geometric morphometrics: achievements and the ongoing quest for biological meaningfulness The importance of precise plane selection for female adult Chiari type I malformation midsagittal morphometrics O’Shaughnessy Acquired Chiari malformation type I associated with a supratentorial arteriovenous malformation Statistical shape analysis of the brainstem in Chiari patients Reappraisal of the types of trigeminal Porus and importance in surgical applications Crossref Full Text | Google Scholar Error in geometric morphometric data collection: combining data from multiple sources Crossref Full Text | Google Scholar The influences of Porus acusticus internus on ethnicity and importance in preoperative and intraoperative approaches Clinical features of Chiari I malformations PubMed Abstract | Crossref Full Text | Google Scholar MRI-based morphometric analysis of posterior cranial fossa in the diagnosis of Chiari malformation type I Analysis of the volumes of the posterior cranial fossa and herniated tonsils using the stereological methods in patients with Chiari type I malformation Chiari malformations type I without basilar invagination in adults: morphometric and volumetric analysis Fahmy K and Millard JA (2024) Geometric morphometric analysis of the brainstem and cerebellum in Chiari I malformation Received: 16 May 2024; Accepted: 24 July 2024; Published: 07 August 2024 Copyright © 2024 Perera, Zahed, Moriarty, Simmons, Rodriguez, Botkin, Dickson, Kasper, Fahmy and Millard. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) *Correspondence: Jonathan A. Millard, am1pbGxhcmRAdnQudmNvbS5lZHU= Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher 94% of researchers rate our articles as excellent or goodLearn more about the work of our research integrity team to safeguard the quality of each article we publish Recent release “Living with Chiari Malformation” from Newman Springs Publishing author Tracy Young is a thought-provoking account that aims to shed light on the complexities of living with Chiari malformation a neurological condition affecting the brain and spinal cord Young aims to provide insight and clarity into the challenges the condition can bring about — The 17th annual Conquer Chiari Walk Across America took place across the country on Saturday where participants raised money and awareness for Chiari malformation Chiari is a condition that occurs when the bottom part of the brain descends out of the skull putting pressure on the spinal cord and affecting both the brain and spine These fundraising walks have become an annual tradition held nationwide on the third and fourth weekends of September "Stuff in life happens, and you just can't reverse what happens in life, because whatever happens, all you can do is just get up from the ground and just keep on walking," said Branden Witt Since the organization’s inception in 2008 the walks have raised more than $6.4 million for research and support Do you know about a good news story happening in your community? Click here to email WTVR.com and the CBS 6 News team Metrics details Chiari type 1 malformation is a neurological disorder characterized by an obstruction of the cerebrospinal fluid (CSF) circulation between the brain (intracranial) and spinal cord (spinal) compartments Actions such as coughing might evoke spinal cord complications in patients with Chiari type 1 malformation but the underlying mechanisms are not well understood More insight into the impact of the obstruction on local and overall CSF dynamics can help reveal these mechanisms our previously developed computational fluid dynamics framework was used to establish a subject-specific model of the intracranial and upper spinal CSF space of a healthy control we emulated a single cough and introduced porous zones to model a posterior (OBS-1) and severe posterior-anterior (OBS-3) obstruction OBS-1 and OBS-2 induced minor changes to the overall CSF pressures while OBS-3 caused significantly larger changes with a decoupling between the intracranial and spinal compartment Coughing led to a peak in overall CSF pressure pressure differences between the lateral ventricles and the spinal compartment were locally amplified for all degrees of obstruction These results emphasize the effects of coughing and indicate that severe levels of obstruction lead to distinct changes in intracranial pressure Although these in vivo flow and intracranial pressure measurements serve as a relevant reference they do not provide information on the pressure distribution and flow close to the herniation which are crucial to reveal the mechanism behind syrinx formation to a newly generated and comprehensive MRI dataset (ii) implemented sudden volume changes in the spinal compartment to emulate coughing and (iii) assessed the impact of various degrees of obstruction in the spinal canal on normal pulsatile CSF dynamics and under the action of coughing the setup of the 3D model and the implementation of boundary conditions are presented Magnetic resonance (MR) brain images of a healthy subject were acquired using a 3T MRI scanner (SIGNA Premier; General Electric Healthcare) at the medical research institute Mātai based in Gisborne Ethical approval for this study was obtained through the New Zealand Health and Disability Ethics Committee (20/CEN/107) Informed consent was obtained from all subjects involved in this study All methods were performed in accordance with the relevant guidelines and regulations Data collection included whole-brain anatomical T1 T2 and T2 FLAIR weighted images with isotropic resolution of 0.5 mm3 and axial PC-MRI slices at the level of the second cervical vertebra (C2) and the cerebral aqueduct and 0.7 mm2 in plane resolution was used for these measurements The 3D geometry of the cranial and the upper spinal CSF space was extracted from the anatomical MR images using Mimics 24.0 (Materialise thresholding and region-growing techniques were used to extract the CSF spaces and the geometry was adjusted manually to only preserve CSF regions a minimal thickness of four pixels or about 2 mm was imposed for the subarachnoid space (SAS) The resulting CSF space consisted of a large number of fine structures where the CSF seeps inside larger and finer sulci of the cerebellum and cerebrum these sulci were partially removed or heavily smoothed to facilitate meshing afterwards and limit computational cost All the resulting geometries were checked in 3-Matic 16.0 (Materialise Belgium) for possible meshing errors and boundary surfaces were selected An unstructured mesh was generated using ICEM 2021 R2 (Ansys The mesh was composed of tetrahedral elements with three prism layers at the boundaries and was refined in the aqueduct region to ensure that the parabolic laminar profile was accurately captured in this thin region (1–2 mm in diameter) A mesh sensitivity study was conducted with four different meshes (with a number of volumes ranging from 0.41 to 4.29 million) whereby we evaluated two variables that are critical in this study: the pressure difference between the lateral ventricles (lv) and spinal SAS corresponding to a difference of less than 3% for these two variables compared to the finest mesh More details on the mesh parameters and mesh sensitivity study can be found in the supplementary material (section A) (a) Model geometry with the inlet (blue) and outlet (red) boundary conditions and the anterior and posterior porous zones (green) (b) Section of the 3D model showing the intracranial (green) and upper spinal (blue) compartment and cross-sectional planes where flows in (c) and spatial pressure differences are calculated (c) Original and smoothed (as used in this model) PC-MRI measurements of volumetric flow through the cross-sections of cerebral aqueduct and spinal SAS with caudal/ventral flow being positive leading to an imposed velocity \(v_{production}\) in m/s the source term \(S_{basilar} \left( t \right)\) (kg/m3s) imposed in the region anterior to the brainstem can be described in the following way: where \(V_{basilar}\) (m3) is the volume of CSF region posterior to the brainstem and \(\rho_{csf}\) the density of CSF (\(998.2 \;{\text{kg}}/{\text{m}}\)) For each outlet i, \(Q_{i}\) is the outflow, \(P_{i}\) the pressure and \(R_{i}\) the corresponding resistance. \(P_{ext}\) is the external pressure and was considered zero. Meanwhile,2-element windkessel models were imposed at the interstitium and spinal outlet to model CSF absorption and buffering following Eq. 6 with \(C_{i}\) the compliance and t the time The peak-to-peak pressure difference was allowed to maximally deviate 0.01 mmHg compared to the targeted value for calculation of compliance Compliance values for the interstitium and spinal outlet were 0.0988 and 0.1977 ml/mmHg the pressure perturbation was varied between 1 to 1E-2 Pa to ensure a decreasing value of the flow residual over the coupling iterations and was implemented into the CFD model as a source term \(S_{cough} \left( t \right)\) (kg/m3s) which was described by a gaussian function leading to a subsequent steep positive (subscript p) and negative inflow (subscript n) factor A (kg/m3s) was estimated using the 0D windkessel model and the factor leading to an increase in intracranial pressure of minimally 35 mmHg was selected which was 2356.30 kg/m3s and corresponded to a peak volumetric inflow into the model of 50.46 ml/s This approach had as the major benefit that all computations could be done on identical geometries and meshes thereby avoiding that differences in the boundary zones or numerical meshes introduced differences between simulations which may interfere with the effects of the obstruction The validity of the approach for the computation of cranio-spinal pressure differences was verified by comparison of the porous zone approach with the conventional stenosed geometry methodology in a cropped model Results of this comparison study are provided in the supplementary material (section C) The anterior and posterior porous zones were created in ICEM 2021 R2 (Ansys USA) after meshing and extended along the spinal canal over a length of 1 cm (between z = − 0.050 to − 0.060 m) At an axial plane with z-coordinate − 0.055 m the posterior zone filled 75% of the spinal canal where the anterior zone entailed the remaining 25% the relation between pressure difference (\({\text{dP}}\)) and volumetric flow (\(Q\)) over a porous zone with cross-sectional area (\({\text{A}}\)) and length (\({\text{d}}\)) is given by where \({\text{R}}_{{{\text{viscous}}}}\)[1/m2] is the viscous resistance and \({\upmu }\) [kg/m.s] the dynamic viscosity different degrees of obstruction could be modelled by varying the viscous resistance (in all directions) CSF was modelled as an incompressible Newtonian fluid with properties the same as water (density 998.2 kg/m3 and dynamic viscosity of 0.001003 kg/m.s) The effects of gravity were not taken into account The Navier–Stokes equations were solved using the numerical finite volume solver Fluent 2021 R2 (Ansys the transient simulations were run using a PISO scheme a second-order temporal discretization and linear for pressure and second order for momentum spatial discretization The relaxation factors for momentum and pressure varied between 0.5 and 0.15 to stabilize the convergence An initial time-step size of 0.01 s was imposed This time-step was reduced during the cough to 0.001 s to improve the convergence of the simulation results All simulations were run for four cardiac cycles The convergence criterion for residuals in the solver iterations was set to 1E-5 for continuity and 1E-9 for the three velocity directions For the residuals of the coupling iterations with the windkessel models a dynamic flow criterium with a value of three orders of magnitude lower (1E-3) than the lymphatic volumetric outflow was set (on average 1E-9 m3/s) Less than 0.5% of coupling iterations did not meet the set convergence criterion for all simulations The central computing infrastructure of Ghent University (HPC) was used for the simulations using up to 128 processor cores The simulation of 4 s (1300 timesteps) took between 31 to 37 h to run for the different cases The results are organized into three sections: (i) comparison of simulation results for a healthy control with in vivo measurements and targeted pressures and evaluation of the impact of three different degrees of obstruction (ii) during pulsatile CSF dynamics and (iii) during coughing (a) Smoothed PC-MRI flow measurements compared to simulated flow through the cross-sections of the cerebral aqueduct and the spinal SAS (b-g) Selection of velocity contours at six different timepoints to visualize velocity distribution and with details of the velocity vectors in (b) and (e) (h) Pressure at the spinal and interstitium outlet presented together with the pressure in the 0D model (0D) with horizontal lines depicting the targeted mean pressure (10 mmHg) and amplitude (2 mmHg) (i) Plot of pressure differences between the fourth ventricle (v4) and the lateral ventricle (lv) To evaluate the impact of an obstruction, the simulation results of the healthy control are compared with those corresponding to three degrees of obstruction introduced in the control as porous zones (see overview in Table 1) Volumetric flow rate through (a) a cross-sectional plane of cerebral aqueduct and spinal SAS and (e) arachnoid villi outlet for four cardiac cycles and zoomed in for one cardiac cycle between 0.5 and 1.5 s Pressure at the (f) interstitium and (g) spinal outlet for four cardiac cycles and zoomed in for one cardiac cycle between 0.5 and 1.5 s (h) Locations of the four different outlets Pressure difference between the fourth ventricle and spinal SAS and the lateral ventricles and spinal SAS (a and zoomed in on one cardiac cycle between 0.5 and 1.5 s (b the effects on flow and pressure are evaluated during coughing starting by inducing coughing in the control case without obstruction and then gradually increasing the obstruction from OBS-1 to OBS-2 and OBS-3 (a) Simulated flow through the cerebral aqueduct and the spinal SAS and visualization of the selected timepoints (red) during a cough Velocity vectors in a sagittal cross-section at six different timepoints: (b) at the start of the cough (d) at peak spinal SAS flow in cranial direction (e) after the change in flow direction in the spinal SAS (f) at peak spinal SAS flow in caudal direction When introducing different degrees of obstruction, a close overlap is observed for the volumetric flow rates through the spinal SAS (Fig. 3a) and the four outlets (Fig. 3b-e) for the control Only the OBS-3 leads to a significant change in the volumetric flow during coughing with an increase in peak flow through the spinal outlet and a reduction of flow through the spinal SAS and into the interstitium outlet the impact of different degrees of obstruction on flow distribution pressure and local pressure differences is investigated by introducing three gradations of obstruction (OBS-1 and OBS-3) in a subject-specific 3D model of the cranial and upper spinal CSF circulation This 3D model (control) was first compared with in vivo flow measurements the impact of the different obstructions was evaluated both during normal arterial pulsations and during coughing The model allowed us to not only look at local effects but also at overall effects showing an important amplification of pressure differences during coughing in presence of an obstruction and an overall redirection of the CSF flow for OBS-3 simulation with the 0D model over multiple cardiac cycles shows that the pressure eventually evolves into an equilibrium situation with a stable pressure after minutes to hours these results demonstrate that the presented simulation approach leads to realistic pressures and flows in the subject-specific 3D model of the CSF space the compliance appears to be underestimated in our model although it should be noted that the targeted pressure is not derived from subject-specific pressure measurements and is based on multiple recordings typically performed in patients In vivo values would lead to intracranial pressure pulsations with amplitude between 0.5 and 1.5 mmHg in our model not accounting for physiological effects such as breathing or internal resistance effects (e.g due to the presence of trabeculae in the SAS) might cause this underestimation of compliance To verify that the foramen magnum obstruction by the herniated tonsils can be emulated using a porous zone approach an additional study was performed in a cropped model comparing the effects of a porous zone against those of four physical obstructions (herniation 1 3 and 4) with a shape based on the herniated tonsils as present in Chiari type 1 malformation More about this study can be found in the supplementary material (section C) The pressure difference between the fourth ventricle and the spinal SAS deviated maximally 10% between a 70% area obstruction (herniation 2) and OBS-1 and corresponding pressure-flow curves matched well the peak pressure differences were in the same order as those obtained for an area obstruction of 91% (herniation 3) and 99% (herniation 4) but the pressure-flow distributions were significantly different with a clear linear relation for the porous obstructions (OBS-2 and OBS-3) which was not observed in any of the physical obstructions These findings imply that OBS-1 is a valid choice for investigating pressure differences resulting from a physical obstruction occupying 70% of the spinal canal OBS-2 and OBS-3 peak pressure differences are closest to an area obstruction of 91 and 99% respectively; the latter suggests that OBS-3 corresponds to an almost complete blockage of the spinal canal These results also show that the pressure difference and thus the impact of the obstruction increases with the degree of area obstruction implying that area obstruction relates to disease severity It is an interesting pathway to investigate whether overall compliance decreases in Chiari type 1 malformation which has been suggested by previous studies or whether the phenomenon occurs due to a disconnection of the spinal and intracranial compliance The latter would be caused by the obstruction hindering fluid exchange between the spinal and intracranial compartments This phase shift might either be related to patient-specific differences or to physiological changes in the intracranial compartment related to the obstruction A maximal cranial flow of about 10–20 ml/s was found which is in very good agreement with the peak estimated using our approach (18 ml/s) suggesting that it may take some time for the veins and consequently the CSF domain to return to the original size which contrasts with our assumption of an immediate restoration of venous volume They also found a pressure difference between OBS-1 and OBS-2 with a maximal pressure difference for a case with stenosis and without stenosis (with syringomyelia) of 83 and 28.5 mmHg respectively (an increase of 191%) over a distance of 28 cm Further investigation of the impact of these pressure gradients on the spinal cord parenchyma can provide us with more information on the exact mechanism of syrinx formation but at the same time will add an extra layer of complexity to our models but allow us to compare with results of previous studies also based on cardiac-gated measurements but in-depth evaluation of possible transitional phenomena is beyond the scope of this study we used our computational framework to evaluate the impact of three degrees of obstruction on CSF dynamics during pulsatile CSF flow and coughing The simulation results indicated that coughing amplified the pressure differences between the lateral ventricles and the spinal SAS for all degrees of obstruction and that OBS-3 led to a decoupling of the spinal and intracranial compartment with effects linked to a decrease in intracranial compliance Although further improvements and validation of the model are warranted system-wide models of Chiari type 1 malformation as first presented in this study can provide crucial insights regarding both local and overall CSF dynamics to better understand Chiari type 1 malformation The datasets generated during the current study are available in the 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Spine SPI 17, 367–380. https://doi.org/10.3171/2012.8.SPINE111059 (2012) Download references This work was supported by the Research Foundation Flanders (FWO) Ghent University Special Research Fund (BOF) and the Kānoa—Regional Economic Development & Investment Unit We wish to acknowledge Amith Balasubramanya and Haribalan Kumar (PhD) for brainstorming Tim De Pauw (MD) and Frank Dewaele (PhD) for their clinical input and VSC (Flemish Supercomputer Center) and HPC-UGent (High Performance Computing Ghent University) for providing computational resouces and services Institute of Biomedical Engineering and Technology (IBITECH-BioMMedA) Department of Electronics and Information Systems Faculty of Medical and Health Sciences & Centre for Brain Research was responsible for analysis of the MRI data design and set up of the modelling study and manuscript preparation performed image acquisition and assisted with the analysis of the MRI flow data arranged the image acquisition and assisted in revising and editing the manuscript were supervisors during the development of the model and assisted in revising and editing the manuscript Download citation DOI: https://doi.org/10.1038/s41598-024-62374-8 The Spanish Pediatric Association (Asociación Española de Pediatría AEP) has as one of its main objectives the dissemination of rigorous and up-to-date scientific information on the various areas of pediatrics Annals of Pediatrics is an open access journal that serves as the Association's Scientific Expression Organ and constitutes the vehicle through which members communicate as well as review articles prepared by experts in each specialty and guidelines or positioning documents prepared by the different Societies/Specialized Sections integrated into the Spanish Pediatric Association a reference for Spanish-speaking pediatrics is indexed in the most important international databases: Index Medicus/Medline IBECS A. Echocardiogram, subcostal view, patient 1. B. Echocardiogram, subcostal view, patient 1. Right-to-left shunt through patent foramen ovale (blue flow). C. 3D echocardiogram, subcostal view, patient 1. D. Echocardiogram, 4-chamber view, patient 1. E-F. CT angiography, patient 4. CT, computed tomography; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. Red arrow: Chiari network. Although it is an apparently benign structure, persistence of the CN should be included in the differential diagnosis of cyanosis in newborns. This research did not receive any external funding. The authors have no conflicts of interest to declare. We thank Dr. Flavio Zuccarino for his collaboration in obtaining the computed tomography images. Anales de Pediatría (English Edition) follows the Recommendations for the Conduct, Reporting, Editing and Publication of Scholarly Work in Medical Journals Volume 11 - 2024 | https://doi.org/10.3389/fmed.2024.1422652 This article is part of the Research TopicCase Reports in Hepatobiliary DiseasesView all 16 articles Intravenous leiomyomatosis (IVL) is a rare gynecological-related tumor It can invade and extend in the blood vessel and eventually involve the cardiac cavity or even the pulmonary artery IVL generally does not adhere to the vein wall and infrequently leads to the manifestation of Budd-Chiari syndrome (BCS) the presence of a sizable tumor obstructed the second hepatic portal impeding the return flow of the hepatic veins thereby precipitating the development of BCS The presence of collateral veins and dilation of the accessory hepatic vein were identified through computed tomography venography and ultrasonography The patient underwent a comprehensive surgical resection and was found to have a favorable prognosis Intravenous leiomyomatosis (IVL) is known as a rare intravascular disease that may be localized within the pelvic region or extend into the inferior vena cava, cardiac cavity or even pulmonary artery, with a high risk of sudden death and pulmonary embolism (1, 2). It may present asymptomatically or with symptoms such as abnormal uterine bleeding, chest distress, dyspnea, and lower limb edema (3) there have been few reports of Budd-Chiari syndrome (BCS) caused by IVL It is worth noting that the concurrent use of computed tomography and ultrasonography offers significant benefits in the diagnosis and assessment of this condition A 49-year-old female was admitted to the local hospital 1 month ago due to recurrent vaginal bleeding the patient had undergone a myomectomy procedure Subsequent gynecological ultrasonography identified multiple uterine fibroids one of which was located beneath the mucosa and measured 3.4 cm × 3.7 cm × 2.0 cm the patient was scheduled for surgical intervention preoperative echocardiography revealed the presence of space-occupying lesions in the right atrium and inferior vena cava it was observed that the heart sound exhibited low intensity and weakness no pathological murmurs were detected during auscultation of each valve area and no tumor-related fluttering sounds were present Below the umbilicus and above the pubic symphysis palpation revealed firm and less mobile mass located in the area between the outer margin of the rectus abdominis on both sides This mass exhibited a regular shape and displayed distinct boundary with the surrounding tissues Images of the mass in inferior vena cava (IVC) and right atrium on enhanced CT (A) Coronal image showed multiple soft tissue masses surrounding the uterus (B) Transverse section showed that the lesion occupies almost the entire right atrium The transverse sections of enhanced abdominal CT images (A) The second hepatic hilum was obstructed by the mass (B,C) Arrows demonstrated the presence of communicating branches between the hepatic veins (C) The arrow head pointed the dilated accessory hepatic vein These collateral circulations serve to drain the blood flow from the distal segment of the middle hepatic vein and the left hepatic vein into the inferior vena cava (A,B) The asterisks indicated the hypoechoic mass located within the right atrium and inferior vena cava measuring 6.3 cm × 4.8 cm in dimensions (B) The inferior vena cava exhibited dilation with a proximal diameter of 3.1 cm Images of liver greyscale and color Doppler sonography (A) The lesion (asterisk) obstructed the blood flow from the left and middle hepatic veins to the inferior vena cava resulting in a reversal of blood flow from the left hepatic vein into the middle hepatic vein (B) Arrows show the direction of the blood flow: the white arrows illustrate the normal direction of blood flow while the yellow arrows indicate the retrograde flow of the proximal segment of MHV which drains LHV and redirects it through collateral vessels (red arrows) to the veins in the right lobe of the liver Images of collateral circulation between hepatic veins on greyscale and color Doppler sonography White arrows indicated the collateral veins (A,C) Gray-scale images displayed the collateral veins connecting MHV and the dilated accessory hepatic vein in the posterior right lobe from various perspectives (B,D) Color Doppler blood flow images illustrated the blood flow within the collateral veins from different angles The blood flow direction was observed to move from MHV toward the dilated accessory hepatic vein ultimately draining into the inferior vena cava The asterisk denoted the presence of a tumor it was determined that the leiomyoma originated from the left side and subsequently merged into the left renal vein The postoperative pathological diagnosis revealed multiple uterine leiomyoma with intravenous leiomyomatosis The patient experienced a successful recovery with no recurrence observed for a period of 7 years CTV is capable of accurately assessing the growth trajectory, size, and extent of involvement of IVL tumors within blood vessels. IVL typically presents as soft tissue density within the vein on CTV, exhibiting heterogeneous contrast enhancement, frequently in conjunction with a background of multiple uterine fibroids or prior resection of multiple uterine fibroids. The luffa sponge sign or sieve sign is a typical manifestation on enhanced CT (12) The tumor demonstrates a tendency to grow cephalad along the iliac vein or ovarian vein eventually infiltrating the inferior vena cava and potentially extending into the right atrium Ultrasound imaging enables real-time observation of tumors and assessment of hemodynamics including tumor activity in the right atrium and inferior vena cava as well as evaluation of right heart function The combined use of CTV and ultrasound allows for a comprehensive evaluation of the tumor and accurate diagnosis of secondary Budd-Chiari syndrome This approach also provides clear indications of hemodynamic changes in the liver intravenous leiomyomatosis is a tumor that exhibits unique characteristics in terms of its biological behavior and imaging features and can lead to secondary complications such as Budd-Chiari syndrome The utilization of multiple imaging modalities is beneficial for the accurate diagnosis and assessment of IVL The original contributions presented in this study are included in this article/supplementary material further inquiries can be directed to the corresponding authors The studies involving humans were approved by the Institutional Review Board of Peking Union Medical College Hospital The studies were conducted in accordance with the local legislation and institutional requirements The participants provided their written informed consent to participate in this study Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article This study was supported by the Central High Level Hospital Clinical Research Project of Peking Union Medical College Hospital (2022-PUMCH-C-053 and 2022-PUMCH-B-064) Molecular pathological approach of uterine intravenous leiomyomatosis Google Scholar Manifestation and management of intravenous leiomyomatosis: A systematic review of the literature Management and prognosis comparison between incidental and nonincidental intravenous leiomyomatosis: A retrospective single-center real-life experience Update on intravenous leiomyomatosis: Report of five patients and literature review Google Scholar Google Scholar Intravenous leiomyomatosis presenting as acute Budd-Chiari syndrome Intravenous leiomyomatosis complicated by Budd-Chiari syndrome Google Scholar Obstruction of the hepatic venous flow caused by intravenous leiomyomatosis Computed tomography angiography manifestations of collateral circulations in Budd-Chiari syndrome Budd-Chiari syndrome/hepatic venous outflow tract obstruction Google Scholar Contrast-enhanced CT findings of intravenous leiomyomatosis Google Scholar Leiomyosarcoma of the inferior vena cava: analysis and search of world literature on 141 patients and report of three new cases Diagnostic value of contrast-enhanced ultrasound in intravenous leiomyomatosis: A single-center experiences Yang X and Li JC (2024) Imaging findings of Budd-Chiari syndrome caused by intravenous leiomyomatosis: a case report Copyright © 2024 Wang, Dong, Tian, Chen, Yang and Li. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) *Correspondence: Xiao Yang, eWFuZ19zbWlsZUAxNjMuY29t; Jianchu Li, amlhbmNodS5saUAxNjMuY29t Volume 9 - 2021 | https://doi.org/10.3389/fped.2021.574402 This article is part of the Research TopicDNA damage, genome stability and human diseaseView all 14 articles Frontometaphyseal dysplasia 1 (FMD1) is a rare otopalatodigital spectrum disorder (OPDSD) that is inherited as an X-linked trait and it is caused by gain-of-function mutations in the FLNA It is characterized by generalized skeletal dysplasia and craniofacial abnormalities including facial dysmorphism (supraorbital hyperostosis The involvement of the central nervous system in patients with OPDSD is rare we present the case of a 12-year-old boy with facial dysmorphism and irregular sclerosis with hyperostosis of the skull Brain and whole-spine magnetic resonance imaging revealed Chiari I malformation with extensive hydrosyringomyelia from the C1 to T12 levels Targeted next-generation sequencing identified a hemizygous pathologic variant (c.3557C>T/p.Ser1186Leu) in the FLNA This is the first report of a rare case of OPDSD with pansynostosis and Chiari I malformation accompanied by extensive syringomyelia these cases were only clinically reported and did not undergo genetic confirmation with pansynostosis and Chiari I malformation accompanied by extensive syringomyelia A 12-year-old boy visited our clinic with complaints of back pain since 2 years. His medical history included bilateral sensorineural hearing loss and multiple joint contractures on both wrists and fingers, most prominently in the proximal interphalangeal joint of the left fifth finger. He has two male cousins who resemble him in appearance. His parents and sister show no obvious anomalies (Figure 1) The asterisk indicates people tested for the FLNA pathogenic variant The affected members are indicated by gray shading Symbols divided into halves indicate heterozygous carriers of FMD1 Physical examination revealed facial dysmorphism with micrognathia hypoplasia of the left fifth digital phalanx and great toes The intrinsic muscles of both hands were graded as 2/5 based on the manual muscle test Knee and ankle jerks were hyperreflexic and ankle clonus was evoked and somatosensory and motor-evoked potential tests X-ray showing (A) scoliosis of the whole spine; (B) mild bowing of the tibia and (C) humerus; (D) flexion contracture of the left fifth proximal phalangeal joint; (E) hyperostosis Brain and whole-spine magnetic resonance imaging and computed tomography showing (A,B) Chiari I malformation with extensive hydrosyringomyelia from the C1 to T12 levels and (C) C2 spina bifida Reverse DNA sequencing chromatogram of the patients and his family members the author was unsure whether the CM1 was a characteristic of FMD1 or an incidental finding because it was the first report of such an occurrence many previous reports of FMD1 did not mention whether brain MRI was performed and it is not clear whether CM1 was present Because CM1 was observed in our patient with FMD1 there is a possibility that this type of malformation is a manifestation of this disease Craniofacial anomaly is one of the major features of OPDSD, and several cases with craniosynostosis have been reported. To date, six patients with gain-of-function variants of FLNA have been reported to show craniosynostosis, and there was only one patient who was diagnosed with FMD1 with pansynostosis similar to our patient (48) Our case is the seventh case of craniosynostosis in OPDSD and second for pansynostosis emphasizing that FMD1 can be associated with craniosynostosis if the patient is diagnosed as having gain-of-function variants of FLNA craniosynostosis should be promptly checked immediate surgical treatment can prevent CM1 and thus Several reported FMD1 cases exhibit hypoplasia of hand intrinsic muscles (11) the strength of the hand intrinsic muscles was graded as 2/5 in our patient The development of hand weakness has not been explored in previous studies it is currently difficult to determine whether extensive syringomyelia is the direct cause of hand weakness or whether hand weakness can appear without any CNS lesions because it is a clinical characteristic of FMD1 Additional research is warranted to address this issue Our patient exhibited CM1 with syringomyelia; however CNS anomalies were not reported in other patients with FMD1 who carried the same missense mutation The genotypic and phenotypic correlation in patients with OPDSD is complex and difficult to define Further genotypic and phenotypic correlation studies are needed to address these issues We reported a rare case of FMD1 resulting from a pathogenic variant (c.3557C>T) of FLNA This case was distinguished from those previously reported in that the patient had pansynostosis and showed CNS involvement in the form of Chiari I malformation accompanied by extensive syringomyelia evaluation of craniosynostosis and CM1 malformation may be essential and proper treatment is critical for the prognosis of these patients Further studies are warranted to determine whether CNS involvement is a phenotype of FMD1 The original contributions presented in the study are included in the article/Supplementary Material further inquiries can be directed to the corresponding author The studies involving human participants were reviewed and approved by the Catholic University of Korea Written informed consent to participate in this study was provided by the participants' legal guardian/next of kin Written informed consent was obtained from the parent of the patient for publication of this case report and critical revision of manuscript for intellectual content All authors contributed to the article and approved the submitted version The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fped.2021.574402/full#supplementary-material Novel X-linked syndrome of cardiac valvulopathy and reduced joint mobility due to filamin A substitution G1576R The X-linked filaminopathies: synergistic insights from clinical and molecular analysis Otopalatodigital syndrome spectrum disorders: otopalatodigital syndrome types 1 and 2 frontometaphyseal dysplasia and Melnick-Needles syndrome Actin-binding protein (ABP-280) filamin gene (FLN) maps telomeric to the color vision locus (R/GCP) and centromeric to G6PD in Xq28 Mapping of two genes encoding isoforms of the actin binding protein ABP-280 Amino- and carboxyl-terminal domains of Filamin-A interact with CRMP1 to mediate Sema3A signalling The filamins: organizers of cell structure and function Filamins as integrators of cell mechanics and signalling X-linked otopalatodigital spectrum disorders Google Scholar Localized mutations in the gene encoding the cytoskeletal protein filamin A cause diverse malformations in humans Frontometaphyseal dysplasia: mutations in FLNA and phenotypic diversity Autosomal dominant frontometaphyseal dysplasia: delineation of the clinical phenotype Mutations in MAP3K7 that alter the activity of the TAK1 signaling complex cause frontometaphyseal dysplasia Oto-palatal-digital syndrome type II with X-linked cerebellar hypoplasia/hydrocephalus Coexistence of 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CrossRef Full Text | Google Scholar Pathogenesis of Chiari malformation: a morphometric study of the posterior cranial fossa The incidence of craniocervical bony anomalies in the adult Chiari malformation Brain imaging in idiopathic intracranial hypertension Chronic tonsillar herniation in Crouzon's and Apert's syndromes: the role of premature synostosis of the lambdoid suture CrossRef Full Text | Google Scholar Stratified whole genome linkage analysis of Chiari type I malformation implicates known Klippel-Feil syndrome genes as putative disease candidates Chiari type 1-a malformation or a syndrome PubMed Abstract | CrossRef Full Text Chiari I malformation in defined genetic syndromes in children: are there common pathways A genetic hypothesis for Chiari I malformation with or without syringomyelia Population-based description of familial clustering of Chiari malformation Type I Sleep apnea and vocal cord paralysis secondary to type I Chiari malformation PubMed Abstract | Google Scholar Google Scholar CrossRef Full Text | Google Scholar Pathophysiology of syringomyelia associated with Chiari I malformation of the cerebellar tonsils Pathogenesis of Chiari I - pathophysiology of syringomyelia: implications for therapy: a summary of 3 decades of clinical research Association of mutations in FLNA with craniosynostosis CrossRef Full Text | Google Scholar Lee D-W and Jang D-H (2021) Case Report: Pansynostosis Chiari I Malformation and Syringomyelia in a Child With Frontometaphyseal Dysplasia 1 Received: 19 June 2020; Accepted: 08 June 2021; Published: 01 July 2021 Copyright © 2021 Kim, Lee and Jang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) *Correspondence: Dae-Hyun Jang, ZGhqYW5nbWRAbmF2ZXIuY29t 1) 0ms;transition:background-color 150ms cubic-bezier(0.4 1) 0ms;transition:fill 120ms cubic-bezier(0.4 1) 0ms;font-size:inherit;}.css-v4v4rs{-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none;width:1em;height:1em;display:inline-block;fill:currentColor;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;-webkit-transition:fill 120ms cubic-bezier(0.4 1) 0ms;font-size:inherit;}@media (min-width:0px){.css-v4v4rs{display:block;}}@media (min-width:1100px){.css-v4v4rs{display:none;}}.css-mps3fk{-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none;width:1em;height:1em;display:inline-block;fill:currentColor;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;-webkit-transition:fill 120ms cubic-bezier(0.4 At the time of Malone's firing, the Nuggets were 47-32, meaning they had only three games remaining on their regular-season schedule. Denver was also positioned as the No. 4 seed in the Western Conference when Malone was fired, which suggested they had a chance to make some noise in the playoffs. The timing of the firing was surprising, as was the abrupt parting of ways with a coach who had enjoyed so much success with the franchise. Over his 10 seasons as Nuggets head coach, Malone posted a 471-327 record, and he had the team poised for a seventh consecutive playoff appearance. Malone is also less than two years removed from leading the Nuggets to their first-ever NBA championship. David Adelman replaced Malone on an interim basis and led Denver to a 124-116 win over the Sacramento Kings in his first game at the helm Wednesday. The Nuggets now have just two regular-season games remaining against the Memphis Grizzlies on Friday and Houston Rockets on Sunday. At 48-32, the Nuggets are the No. 4 seed in the West, although they are tied with the fifth-seeded Los Angeles Clippers and just one game ahead of the Golden State Warriors, Grizzlies and Minnesota Timberwolves. With three-time NBA MVP Nikola Jokić leading the way, the Nuggets will be a threat to go the distance come playoff time no matter where they end up being seeded. It seems the Nuggets front office felt a coaching change would improve the chances of that happening, and while that could potentially be proved true, there is inherent risk involved with firing a coach who recently won a championship. Volume 9 - 2022 | https://doi.org/10.3389/fsurg.2022.850879 Diagnosis of Chirai malformation type I (CM-I) is based on magnetic resonance imaging of the brain or cervical spinal cord The main goal of surgery is to relieve the blockage to the free pulsatile flow of cerebrospinal fluid beyond the foramen magnum and to stop the progression of a syringomyelia Despite recent advances in imaging and surgery there is no consensus on optimal management of CM-I Ongoing focus is devoted to a better consideration of the pathophysiology of CM-I and the development of more effective medical and surgical treatments It is hoped that proposed algorithm helps the neurosurgeon to provide a precise management for patients with CM-I in advance In order to avoid the potentially surgical failure following the decompression of posterior cranial fossa (PCF) (also known as FMD) in clinical practice it is important to accurate evaluation through multiple tools before surgery and subsequently to perform an individual operation the essential strategy focused on CM-I surgery during perioperative period were highlighted in this article Preoperative over-extension/flexion dynamic X-ray showing normal bone structure of atlantoaxial dislocation basilar invagination and assimilation of atlas (A and B) computerized tomography (CT) examination confirm concomitant multiple bony abnormalities in the same patient (C and D) Preoperative 3-dimensional T2-weighted CISS sequence demonstrating arachnoid veil resulting in the cerebrospinal fluid (CSF) blockage yellow arrow indicating the arachnoid veil intraoperative intradural exposure of the craniocervical junction dorsally illustrating an arachnoid veil causing fourth ventricular outlet obstruction postoperative MRI showing the remove of arachnoid vei and shrinkage of syringomyelia on red arrow (C) postoperative sagittal cine-PC showing the improvement of CSF flow (D) Preoperative midsagittal T2-weighted MRI scan showing slightly ventral compression but no syringomyelia in 40-year-old male patient (A) who underwent bony decompression and posterior stabilization of craniocervical junction for numb in both arms and stiff in neck postoperative midsagittal T2-weighted MRI scan displaying the marked improvement CSF flow anteriorly and posteriorly at the foramen magnum (B) the postoperative sagittal CT images showing the posterior reduction and stabilization (C) Preoperative midsagittal T2-weighted MRI scan showing seriously ventral compression but no syringomyelia in another 51-year-old male patient who experienced bony decompression and titanium cage implanting as well as posterior stabilization of craniocervical junction for ataxia and weakness in all limbs (D) postoperative midsagittal T2-weighted MRI scan illustrating that the compression of brain stem dissolved excellently (E) the postoperative sagittal CT images showing the satisfactory distraction after posterior reduction and stabilization (F) which is a new predictive tool for improvement in adult CM-I after decompression surgery More and more evidences demonstrated that variety of quantitative measurable tools were developed and used for individually evaluation which eventually lead to precise outcome analysis for patient with CM-I All human studies have been approved by the appropriate ethics committee of Zhengzhou University and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments FG: literature review and manuscript writing The authors thank the members of their research group for useful discussions Chiari conundrum: researchers tackle a brain puzzle for the 21st century PubMed Abstract | CrossRef Full Text | Google Scholar Chiari malformations: principles of diagnosis and management CrossRef Full Text | Google Scholar and management of clinical scenarios from a panel of 63 international experts in the field of Chiari I malformation Chiari malformation and atlantoaxial instability: problems of co-existence Surgical management of Chiari malformation: analysis of 128 cases Transoral approach and its superior extensions to the craniovertebral junction malformations: surgical strategies and results CrossRef Full Text | Google Scholar Correlation of hindbrain CSF flow and outcome after surgical decompression Switzerland: Springer Nature Switzerland AG (2020) PubMed Abstract | CrossRef Full Text | Google Scholar Clinical application of diffusion tensor imaging in Chiari malformation type I- advances and perspectives Which neuroimaging techniques are really needed in Chiari I A short guide for radiologists and clinicians CrossRef Full Text | Google Scholar The impact of neurosurgical technique on the short- and long-term outcomes of adult patients with Chiari I malformation High long-term symptomatic recurrence rates after Chiari-I decompression without dural opening: a single center experience Institutional experience with 500 cases of surgically treated pediatric Chiari malformation type I Malformations of the craniocervical junction (Chiari type I and syringomyelia: classification Improvement of syrinx resolution after tonsillar cautery in pediatric patients with Chiari Type I malformation Expansile duraplasty and obex exploration with bone-only decompression for Chiari malformation type I in children: retrospective review of outcomes and complications The complex Chiari: issues and management strategies PubMed Abstract | CrossRef Full Text | Google Scholar Complex Chiari malformation: using craniovertebral junction metrics to guide treatment Complex Chiari malformation presenting with bulbar symptoms in an adult: single-stage posterior fusion and foramen magnum decompression: a rare case report Complex Chiari malformation: proposal of a new set of diagnostic criteria and outcomes after fusion surgery Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion Intraoperative ultrasound in spine surgery: history patient-reported outcome after posterior fossa decompression in 79 patients with Chiari malformation type I A noved scoring system for assessing Chiari malformation type I treatment outcomes Positive and negative predictors for good outcome after decompressive surgery for Chiari malformation type 1 as scored on the Chicago Chiari Outcome Scale Clinical outcome measures in Chiari malformation PubMed Abstract | CrossRef Full Text | Google Scholar Pediatric Chiari malformation type I: long-term outcomes following small-bone-window posterior fossa decompression with autologous-fascia duraplasty Surgical decompression for Chiari malformation type I: an age-based outcomes study based on the Chicago Chiari Outcome Scale Prognostic significance of C1-C2 facet malalignment after surgical decompression in adult Chiari malformation type I: a pilot study based on the Chicago Chiari Outcome Scale The Chiari severity index: a preoperative grading system for chiari malformation type 1 The Seow Operative Score (SOS) as a decision-making adjunct for paediatric Chiari I malformation: a preliminary study The SHORE Score: a novel predictive tool for improvement after decompression surgery in adult Chiari malformation type I Management: opinions from different centers-the Istituto Giannina Gaslini experience Citation: Guo F and Turgut M (2022) Precise Management of Chiari Malformation with Type I Received: 8 January 2022; Accepted: 10 March 2022; Published: 28 March 2022 Copyright © 2022 Guo and Turgut. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) *Correspondence: Fuyou Guo Y2h5b3U2NjZAaG90bWFpbC5jb20= basion to the inferoposterior portion of the C2 body; CXA Symptomatic patients usually require surgery, which attempts to restore CSF flow at the foramen magnum. Offered surgical procedures include suboccipital decompression, cerebellar tonsillar cautery, or resection of the C1 posterior arch. [5] When MRI scanning is contraindicated, a non-contrast CT brain or CT myelography may be used. While CT offers excellent spatial resolution, its ability to resolve soft tissues is limited. Radiographs of the head, neck, spine, and extremities are helpful in assessing associated skeletal abnormalities. [18] Acquired Chiari I malformation is reported to develop after lumboperitoneal or ventriculoperitoneal shunt placement Radiologic findings in patients with acquired Chiari I malformation cannot be distinguished from those in the congenital form of the malformation Evaluation by Davidson et al of a large group of patients with incidentally discovered Chiari I malformations demonstrated that most patients can be managed conservatively, especially in the absence of syringomyelia. [23]   (The anatomic landmarks pertinent to this disorder are shown in the image below. [24] ) spine and proximal extremities are helpful for assessing associated skeletal abnormalities in patients with Chiari I malformation Skull xrays may show reduced height of the supraocciput and clivus Additional radiographs of the spine and extremities may be needed skeletal abnormalities are present in 23%–45% of patients with Chiari I malformation These include the following (frequency of association is given in parentheses): Klippel-Feil syndrome (5%–10%) Proatlantal remnant spina bifida at the C1 level Kyphosis a non-contrast CT brain or CT myelography may be used While CT offers excellent spatial resolution its ability to resolve soft tissues is limited. The real strength of CT is in delineating osseous abnormalities and bony details On CT scans of patients with Chiari I malformation Descending peg-like cerebellar tonsils (> 5 mm in adults cervical or spinal CT scans may show syringomyelia CT can also be used to assess associated bony abnormalities of the skull base and vertebral column. These associated abnormalities may include basilar invagination, platybasia, small posterior fossa, short horizontal clivus, retroverted dens, hypoplastic occipital condyles, segmentation anomalies (such as atlanto-occipital assimilation), scoliosis, etc. [5] so regular follow-up using this modality is to be discouraged (unless MRI is absolutely contraindicated).  supplemented by image reconstruction in non-axial planes were used to assess tonsillar position and configuration CT myelograms do not demonstrate the lower brainstem and bulbomedullary junction in sufficient detail These techniques are rarely used now due to these limitations.  Displacement of cerebellar tonsils below the level of the foramen magnum Associated abnormalities such as syringomyelia and skeletal abnormalities (if covered in the imaging field) The degree of tonsillar ectopia in Chiari I malformation is expressed as the number of millimeters that the tonsillar tips extend below a line connecting the basion with the opisthion (see the first image below) These measurements are usually undertaken on sagittal T1-weighted images A key consideration is to use the signal intensity of cortical bone (black/low signal) to define the anatomic landmarks (see the second image below) Tonsillar tips that extend less than 3 mm below the landmark are normal Tonsillar ectopia of 5 mm is 100% specific and 92% sensitive for Chiari I malformation in adults Tonsillar herniation of less than 5 mm does not exclude the diagnosis Herniation of both tonsils that are 3–5 mm below the foramen magnum when accompanied by certain other features These other features include a syrinx (see the image below) elongation of the fourth ventricle and a pointed or peglike appearance of the tonsils A key consideration is whether the patient is symptomatic.  Narrowing or obliteration of the retrocerebellar CSF spaces is observed in association with a meniscus sign at the lower pole of the cerebellar tonsils The height of supraocciput is reduced and the slope of tentorium is increased in absolute terms and expressed as a ratio of supratentorial volume (posterior fossa ratio) mean brain volumes have not differed between patients and control subjects The cervical subarachnoid space below the level of the C2-3 discs is markedly narrowed in patients with syringomyelia as a result of spinal cord expansion The posterior subarachnoid space below the tip of the cerebellar tonsils may be completely obliterated Other findings include anterior displacement of the cerebellum The cerebral aqueduct is frequently elongated and narrowed no significant descent of the latter structure or brainstem is observed Syringohydromyelia is most commonly observed between the C4 and C6 levels Holocord hydromyelic cavities may be present Cervical/upper thoracic and bulbar/cervical syrinxes also are observed Isolated thoracic syrinxes are not described The level of widest syrinx diameter most frequently occurs at the C2-3 level Asymmetric or multiple axial syrinxes are described Literature shows that foramen magnum diameter, aqueductal stroke volume (ASV), diameter of herniated tonsil, and prepontine cistern diameter-to-aqueduct of sylvius ratio (PPC/AS ratio) are important factors in syrinx development. [31] Several investigators have studied CSF flow abnormalities in Chiari I malformation All patients had narrowing of the CSF pathways at the foramen magnum at the C2-3 disc level and in the posterior subarachnoid space below the tip of the cerebellar tonsils The cardiac cycle and respiration-related CSF flow pulsatility is altered These effects are detectable with motion-sensitive MRI sequences and these can be gated to the cardiac cycle A prolongation of CSF systole is observed in the area above the foramen magnum In the anterior subarachnoid space below the foramen magnum and in the posterior subarachnoid space immediately below the tips of the cerebellar tonsils The duration of CSF systole and the ratio of systolic-to-diastolic CSF displacement are also decreased These findings indicate impaired CSF systolic (craniocaudal) pulsations A reduction of CSF flow can be observed in the subarachnoid space of the posterior cranial fossa (cisterna magna and prepontine cisterns) along with a compensatory pulsatile downward motion of the cerebellar tonsils These flow abnormalities have been shown to revert to normal levels after cranial decompression A relationship exists between CSF flow abnormalities detected on MRIs and syringomyelia CSF flow abnormalities are not correlated with the degree of tonsillar ectopia or the presence of clinical symptoms or their severity Phase-contrast cine MRI may be helpful in demonstrating a disturbance of CSF velocity and/or flow at the foramen magnum in patients with tonsillar ectopia of less than 5 mm.  Intraoperative use of phase-contrast MRI can assess the impact of decompression on the overall CSF flow A review article elaborated on the current status of the literature available for CSF flow studies undertaken in Chiari 1 malformation and possible future directions. [32] Surgery is generally only indicated if the patient is symptomatic The goal of surgery is to restore CSF flow at the foramen magnum Surgical procedures offered include resection of C1 posterior arch ± duraplasty These procedures aim to correct cerebellar tonsillar descent With the widespread availability and use of MRI incidental Chiari I malformation is now more commonly recognized In the absence of relevant clinical symptoms or a syrinx This practice incurs unnecessary costs with no benefit and adds to patient anxiety Correlation with careful clinical assessment remains the cornerstone of proper diagnosis and management Novegno F, Caldarelli M, Massa A, Chieffo D, Massimi L, Pettorini B, et al. The natural history of the Chiari Type I anomaly. J Neurosurg Pediatr. 2008 Sep. 2(3):179-87. [QxMD MEDLINE Link] Caldwell DL, Dubose CO, White TB. Chiari malformations. Radiol Technol. 2009 Mar-Apr. 80(4):340MR-354MR; quiz 355MR-358MR. [QxMD MEDLINE Link] Radswiki T, Khoshnaw K, Goel A. Chiari IV malformation. Radiopaedia.org. Available at https://radiopaedia.org/articles/chiari-iv-malformation Hidalgo JA, Dulebohn SC. Arnold Chiari Malformation. 2017 Jun. [QxMD MEDLINE Link]. [Full Text] Nagaraj UD, Vattoth S. Chiari 1 Malformation. STATdx. Available at https://my.statdx.com/document/chiari-1-malformation/97837e15-0d39-4c87-8af0-028652b399a6?term=Chiari%201%20Malformation&searchType=documents&category=All Rozenfeld M, Frim DM, Katzman GL, Ginat DT. MRI Findings After Surgery for Chiari Malformation Type I. AJR Am J Roentgenol. 2015 Nov. 205 (5):1086-93. [QxMD MEDLINE Link]. [Full Text] Radek Frič, Per Kristian Eide. Chiari type 1-a malformation or a syndrome? A critical review. Acta Neurochir 162, 1513–1525 (2020). [QxMD MEDLINE Link]. [Full Text] McClugage SG, Oakes WJ. The Chiari I malformation. J Neurosurg Pediatr. 2019 Sep 1. 24 (3):217-226. [QxMD MEDLINE Link] Jansen PR, Dremmen M, van den Berg A, et al. Incidental Findings on Brain Imaging in the General Pediatric Population. N Engl J Med. 2017 Oct 19. 377 (16):1593-1595. [QxMD MEDLINE Link] Vernooij MW, Ikram MA, Tanghe HL, et al. Incidental findings on brain MRI in the general population. N Engl J Med. 2007 Nov 1. 357 (18):1821-8. [QxMD MEDLINE Link] Pindrik J, McAllister AS, Jones JY. Imaging in Chiari I Malformation. Neurosurg Clin N Am. 2023 Jan. 34 (1):67-79. [QxMD MEDLINE Link] Zamel K, Galloway G, Kosnik EJ, Raslan M, Adeli A. Intraoperative neurophysiologic monitoring in 80 patients with Chiari I malformation: role of duraplasty. J Clin Neurophysiol. 2009 Apr. 26(2):70-5. [QxMD MEDLINE Link] Akar E, Kara S, Akdemir H, Kırış A. Fractal dimension analysis of cerebellum in Chiari Malformation type I. Comput Biol Med. 2015 Sep. 64:179-86. [QxMD MEDLINE Link] Kadoya T, Takenaka I, Kinoshita Y, Shiraishi M, Uehara H, Yamamoto T, et al. [Monitoring of Somatosensory Evoked Potentials during Foramen Magnum Decompression of Chiari Malformation Type I Complicated with Syringomyelia: A Report of Two Cases]. Masui. 2015 Mar. 64 (3):313-7. [QxMD MEDLINE Link] Alperin N, Loftus JR, Oliu CJ, Bagci AM, Lee SH, Ertl-Wagner B, et al. Magnetic resonance imaging measures of posterior cranial fossa morphology and cerebrospinal fluid physiology in Chiari malformation type I. Neurosurgery. 2014 Nov. 75 (5):515-22; discussion 522. [QxMD MEDLINE Link] Khatwa U, Ramgopal S, Mylavarapu A, Prabhu SP, Smith E, Proctor M, et al. MRI findings and sleep apnea in children with Chiari I malformation. Pediatr Neurol. 2013 Apr. 48 (4):299-307. [QxMD MEDLINE Link] Kular S, Cascella M. Chiari I Malformation. 2023 Jan. [QxMD MEDLINE Link]. [Full Text] Holste KG, Muraszko KM, Maher CO. Epidemiology of Chiari I Malformation and Syringomyelia. Neurosurg Clin N Am. 2023 Jan. 34 (1):9-15. [QxMD MEDLINE Link] Delavari N, Wang AC, Bapuraj JR, et al. Intraoperative Phase Contrast MRI Analysis of Cerebrospinal Fluid Velocities During Posterior Fossa Decompression for Chiari I Malformation. J Magn Reson Imaging. 2020 May. 51 (5):1463-1470. [QxMD MEDLINE Link] Ebrahimzadeh SA, Du E, Chang YM, et al. MRI findings differentiating tonsillar herniation caused by idiopathic intracranial hypertension from Chiari I malformation. Neuroradiology. 2022 Dec. 64 (12):2307-2314. [QxMD MEDLINE Link] Saindane AM, Bruce BB, Desai NK, Roller LA, Newman NJ, Biousse V. Transverse sinus stenosis in adult patients with Chiari malformation type I. AJR Am J Roentgenol. 2014 Oct. 203 (4):890-6. [QxMD MEDLINE Link]. [Full Text] Davidson L, Phan TN, Myseros JS, et al. Long-term outcomes for children with an incidentally discovered Chiari malformation type 1: what is the clinical significance?. Childs Nerv Syst. 2021 Apr. 37 (4):1191-1197. [QxMD MEDLINE Link] Milhorat TH, Chou MW, Trinidad EM, et al. 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[QxMD MEDLINE Link] Department of Specialist Rehabilitation Services New ZealandDisclosure: Nothing to disclose The authors and editors gratefully acknowledge Fred J Laine previously called an Arnold-Chiari malformation is where the lower part of the brain pushes down into the spinal canal the lowest part of the back of the brain extends into the spinal canal This can put pressure on the brainstem and spinal cord This page focuses on Chiari I malformations The severity of Chiari malformations can vary from person to person Talk to your doctor about what the condition means what the implications may be for your health and what treatment you may need Many people with a Chiari I malformation will not have any symptoms. Sometimes they're only found after an MRI scan of the brain is carried out for another reason you may also experience problems using your hands and problems with bladder or bowel control If you've been diagnosed with a Chiari malformation you should contact your doctor for advice if you develop any new symptoms or your symptoms worsen Treatment for Chiari I malformation depends on whether you have any symptoms and how severe they are You might not need any treatment if you do not have any symptoms Painkillers can help relieve any headaches and neck pain If your headaches are severe or you have problems caused by the pressure on your spinal cord (such as movement difficulties) The main operation for Chiari malformation is called decompression surgery Under general anaesthetic a cut is made at the back of your head and the surgeon removes a small piece of bone from the base of your skull They may also remove a small piece of bone from the top of your spine This will help reduce the pressure on your brain and allow the fluid in and around your brain and spinal cord to flow normally Read more about decompression surgery for Chiari malformation: Other procedures that may be necessary include: The aim of surgery is to stop existing symptoms getting any worse Some people also experience an improvement in their symptoms However, surgery sometimes results in no improvement or symptoms getting worse. There's also a small risk of serious complications, such as paralysis or a stroke Talk to your surgeon about the different surgical options and what the benefits and risks of each are The exact cause of Chiari I malformations is unknown but is normally only found in adulthood when symptoms develop or when an MRI scan is done Many cases are thought to be the result of part of the skull not being large enough for the brain Chiari I malformations can also develop in people with a tethered spinal cord, a build-up of fluid on the brain (hydrocephalus) Chiari malformations can sometimes run in families It's possible that some children born with it may have inherited a faulty gene that caused problems with their skull development But the risk of passing a Chiari malformation on to your child is very small And remember: even if your children do inherit it If you have been affected by a Chiari malformation your clinical team may pass information about you on to the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS) This helps scientists look for better ways to prevent and treat this condition You can opt out of the register at any time Find out more about the National Congenital Anomaly and Rare Disease Registration Service Metrics details Chiari malformation type I (CM-I) with cervicothoracic syringomyelia can progress slowly this condition which is very common in clinical practice Patients typically present with chronic complaints although are few reports in the literature describing pediatric patients who developed acute neurological deficits caused by CM-I we report an unusual presentation of this condition; the patient presented with sudden onset arm swelling with no precipitating factors that could explain the diagnosis This is an illustrated case report and literature review The patient’s condition improved post-operatively; in terms of arm and hand swelling which resolved but he still complained of persistent numbness on a follow-up visit a smoker with an unremarkable previous medical history presented with gradual onset chronic headache that lasted for the past four years It was moderate intensity exacerbated by coughing associated with neck pain and bilateral shoulder pain he developed numbness in his right arm which was worsened a few days prior to his presentation to our facility until he developed a sudden onset of the right arm and hand swelling or anything else that could be related to this event the patient showed asymmetrical upper limb size and contour; for which his right side was swollen compared to the left one and there was no change in color or appearance He also had a weak handgrip in the right hand mainly in his finger flexion motor about 3/5 An imaging workup was performed using Doppler ultrasound to rule out upper limb deep venous thrombosis Followed by a cervical spine x-ray that ruled out the presence of cervical rib or subluxation The patient was admitted initially as a picture of acute disc herniation was suspected, and a cervical MRI spine was ordered which revealed evidence of tonsillar ectopia about 9 mm below the foramen magnum, with extensive syringomyelia from cervical vertebrae level (C2) up to thoracic vertebrae level (T3). A brain MRI ruled out the hydrocephalus (Fig. 1). MRI finding sagittal view showing the extent of syrinx and tonsillar descent about 9-mm The axial view showing cross section of cervical segment evidence of syrinx Following the counseling of the patient and obtaining surgical consent he underwent a limited posterior fossa suboccipital craniectomy with the posterior arch of C1-laminectomy with regain of his motor strength in his hand function A unique feature of our Chiari case is the unilateral arm and hand swelling without an obvious cause of thrombosis or infection of the soft tissue such as; tendinitis and septic arthritis A standard midline suboccipital incision was made using the muscle-splitting technique A sub occipital 3 × 3 cm craniotomy was performed and then the posterior arch of C1 laminectomy was performed and the dura was stripped longitudinally with multiple fenestrations An intraoperative ultrasound probe with transcranial Doppler was used to assess the pattern of cerebrospinal fluid flow and velocity transmission along the edge of the foramen magnum we report a case of the common condition CM-I that presented with the unusual symptoms of arm swelling When such as pathophysiology presents with no clear explanation it is worthwhile to consider the possibility of CM-I especially in patients with craniocervical instability The data that support the findings of this study are available on request from the corresponding author The data are not publicly available due to privacy or ethical restrictions Rekate HL. Natural history of the Chiari Type I anomaly. J Neurosurg Pediatr. 2008;2:177–8. https://doi.org/10.3171/PED/2008/2/9/177 Yarbrough CK, Powers AK, Park TS, Leonard JR, Limbrick DD, Smyth MD. Patients with Chiari malformation Type I presenting with acute neurological deficits: case series. J Neurosurg Pediatr. 2011;7:244–7. https://doi.org/10.3171/2010.11.PEDS1097 Oldfield EH, Muraszko K, Shawker TH, Patronas NJ. Pathophysiology of syringomyelia associated with Chiari I malformation of the cerebellar tonsils. Implications for diagnosis and treatment. J Neurosurg. 1994;80:3–15. https://doi.org/10.3171/jns.1994.80.1.0003 Yoshikawa H. Sudden respiratory arrest and Arnold-Chiari malformation. Eur J Paediatr Neurol. 2003;7:191 https://doi.org/10.1016/s1090-3798(03)00052-7 Carew CL, Prasad A, Tay KY, de Ribaupierre S. Unusual presentation of Chiari I in toddlers: case reports and review of the literature. Childs Nerv Syst. 2012;28:1965–70. https://doi.org/10.1007/s00381-012-1826-5 Sudden death revealing Chiari type 1 malformation in two children Hentschel SJ, Yen KG, Lang FF. Chiari I malformation and acute acquired comitant esotropia: case report and review of the literature. J Neurosurg. 2005;102:407–12. https://doi.org/10.3171/ped.2005.102.4.0407 Massimi L, Della Pepa GM, Caldarelli M, Di Rocco C. Abrupt clinical onset of Chiari type I/syringomyelia complex: clinical and physiopathological implications. Neurosurg Rev 2012;35:321–9. https://doi.org/10.1007/s10143-012-0391-4 Download references We disclose there is no source of acknowledgment in writing this manuscript King Fahad Specialist Hospital Dammam (KFSHD) Haitham Ben Ali & Muhammad Imran Bhatti and SB checked and approved the authenticity of the raw data All authors read and approved the final manuscript Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law Download citation DOI: https://doi.org/10.1038/s41394-023-00583-5 The dates displayed for an article provide information on when various publication milestones were reached at the journal that has published the article activities on preceding journals at which the article was previously under consideration are not shown (for instance submission All content on this site: Copyright © 2025 Elsevier B.V., its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies. For all open access content, the relevant licensing terms apply. Chiari-like malformation (CM) and syringomyelia (SM) are frequently diagnosed conditions in small and toy dog breeds, such as the Cavalier King Charles Spaniel and Griffon Bruxellois. CM/SM is only rarely reported in Pomeranians in literature to date. The aims of this study are to 1/describe the phenotype of Pomeranians with or without CM/SM and 2/evaluate for differences and associations between CM/SM and owner-reported clinical signs (ORCS) or signalment factors. From February 2015 to June 2023, historical data and signalment (including country of origin, pedigree, sex and neuter status, age, and body weight) and ORCS of Pomeranians were recorded at multiple institutions. MRI studies of all dogs were evaluated for classification of CM/SM. Additionally, quantitative measurements were performed for SM. Volume 10 - 2023 | https://doi.org/10.3389/fvets.2023.1320942 Introduction: Chiari-like malformation (CM) and syringomyelia (SM) are frequently diagnosed conditions in small and toy dog breeds such as the Cavalier King Charles Spaniel and Griffon Bruxellois CM/SM is only rarely reported in Pomeranians in literature to date The aims of this study are to 1/describe the phenotype of Pomeranians with or without CM/SM and 2/evaluate for differences and associations between CM/SM and owner-reported clinical signs (ORCS) or signalment factors Materials and methods: From February 2015 to June 2023 historical data and signalment (including country of origin and body weight) and ORCS of Pomeranians were recorded at multiple institutions MRI studies of all dogs were evaluated for classification of CM/SM quantitative measurements were performed for SM Results: A total of 796 dogs from 22 different countries were included Total prevalence of CM was 54.9% (437/796) and the prevalence of SM was 23.9% (190/796) The top 5 ORCS included 1/scratching with skin contact 3/spontaneous signs of pain (26.0% of dogs with ORCS) 4/persistent licking front and/or hind paws (22.6% of dogs with ORCS) 5/phantom scratching (22.6% of dogs with ORCS) and air licking were associated with having SM There were no statistically significant associations between quantitative syrinx measurements and ORCS There were statistically significant associations between CM classification and 1/country of origin There were statistically significant associations between SM classification and 1/age and 2/body weight Discussion: This is the first large study evaluating CM/SM in the Pomeranian dog breed Veterinary clinicians can use these findings to increase the likelihood of correctly determining the presence or absence of CM/SM in Pomeranians Breeders may consider using the information regarding signalment factors as well as ORCS associated with CM/SM classifications to select dogs for screening procedures But an MRI-based diagnosis is needed to properly ascertain the exact CM/SM status of their breeding stock until a fool-proof characteristic or genetic marker is found Most of the ORCS are not specific to either of these conditions on their own interpreting them as indicative of pain is inherently subjective relying on owners to report signs has limitations it is of great importance to evaluate the value of ORCS for the diagnosis of CM/SM Without knowing what ORCS are related to CM/SM clinicians cannot assess whether dogs with ORCS are likely to have these disorders or not As diagnostic procedures such as magnetic resonance imaging (MRI) studies require general anesthesia to be performed and costs are incurred by owners for such procedures knowledge of which ORCS linked to CM/SM could help owners and clinicians to ascertain the need for an MRI Although there are only a few documented cases of Pomeranians with CM/SM in veterinary literature, owners, breed clubs and veterinarians realize that CM/SM does occur with Pomeranians (1, 3, 19–22) referred herself to the last author (PM) as all eight dogs showed clinical signs reported as suggestive for CM/SM All eight Pomeranians were diagnosed with either CM a call was placed on social media platforms by this owner and the Belgian and Dutch breed clubs to present their Pomeranians for screening by MRI to estimate the prevalence of these two disorders in this breed some had not but were worried that their dog could be affected The aims of this study are to (1) describe the phenotype of Pomeranians with or without CM/SM and (2) evaluate for differences and associations between CM/SM and ORCS or signalment factors 1) there are no statistically significant associations between the classification of CM/SM and ORCS 2) there are no statistically significant associations between quantitative syrinx measurements and ORCS 3) there are no statistically significant associations between signalment and classification of CM and/or SM During the period of February 2015 to June 2023, Pomeranians, with or without a pedigree, with or without ORCS, were presented to multiple institutions for a so-called screening MRI study for CM/SM (17) All owners agreed to participate in this study and an informed consent of the owner was obtained Signalment factors including country of origin historical data pertaining to the presence or absence of ORCS was acquired via questioning of the owners during consultation and/or owners were requested to fill in an online questionnaire MRI studies were performed under general anesthesia (individualized anesthetic protocols) with either a low-field MRI scanner (<0.5T MRI) or a high-field MRI scanner (1.5T MRI) depending on the institution involved The majority of scans were made at four institutions: (1) Department of Clinical Sciences (2) IVC Evidensia Referral Hospital Arnhem The Netherlands (low-field MRI scanner) and (4) Orion Clinic Sequences obtained included a minimum of sagittal T2-weighted (T2W) sagittal T1W and transverse T2W or T1W sequences of the craniocervicothoracic region Inclusion of the thoracic spinal cord up to at least the 4th thoracic vertebra was required Measurements were performed with use of imaging software (Radiant DICOM viewer) by the first author (KS) Dogs diagnosed with intracranial space-occupying lesions or space-occupying lesions in the vertebral canal were excluded MRI studies with artifacts or insufficient image quality that did not allow for accurate assessments or measurements were also excluded Images were evaluated to assess the presence or absence of CM by evaluating shape of the cerebellum and position of the caudoventral cerebellum (uvula). CM was classified as follows (Figure 1)1: CM0 normal—no cerebellar herniation or impaction (cerebellar uvula rostral to foramen magnum) CM1 abnormal—cerebellar impaction (cerebellar uvula on the line of the foramen magnum no CSF present dorsal to the cervicomedullary junction) and non-rounded shape (e.g. pointed or indented by supraoccipital bone) CM2 abnormal—cerebellar herniation (cerebellar uvula caudal to the line of the foramen magnum no CSF present dorsal to the cervicomedullary junction) 5. The line of the foramen magnum was defined as a straight line between the most ventral aspect of the supraoccipital bone and the most caudal aspect of the basioccipital bone on sagittal MR images (23) Classification of Chiari-like malformation (CM) (A) CM0 = normal—no cerebellar herniation or impaction (cerebellar uvula rostral to foramen magnum) (B) CM1 = abnormal—cerebellar impaction (cerebellar uvula on the line of the foramen magnum (C) CM2 = abnormal—cerebellar herniation (cerebellar uvula caudal to the line of the foramen magnum Images were evaluated to assess the presence or absence of SM in the spinal cord. SM was defined as a well-demarcated intramedullary cavity associated with the central canal of the spinal cord, hyperintense on T2W and hypointense on T1W images. SM was classified as follows (Figure 2): F) SM2 = abnormal—asymmetric (e.g. (A–C) T2-weighted magnetic resonance images (D–F) T1-weighted magnetic resonance images Quantitative measurements were performed when a syrinx was present, including (Figure 3): • Maximum transverse syrinx width/spinal cord width ratio (STWR—T2W and T1W transverse images) • Maximum syrinx height/spinal cord height ratio on transverse images (SHRt—T2W and T1W transverse images) • Maximum syrinx cross-sectional area/spinal cord cross-sectional area ratio (SCSAR—T2W and T1W transverse images) • Maximum syrinx height/spinal cord height ratio on sagittal images (SHRs—T2W and T1W sagittal images) • Length of the syrinx:C3 vertebral body length ratio (SLC3R—T2W and T1W sagittal images) Quantitative syrinx measurements (only T2-weighted magnetic resonance images are shown) (A) Maximum transverse syrinx width/spinal cord width ratio [STWR—T2W (and T1W when available) transverse images] (B) Maximum syrinx height/spinal cord height ratio on transverse images [SHRt—T2W (and T1W when available) transverse images] (C) Maximum syrinx cross-sectional area/spinal cord cross-sectional area ratio [SCSAR – T2W (and T1W when available) transverse images] (D) Maximum syrinx height/spinal cord height ratio on sagittal images (SHRs—T2W and T1W sagittal images) (E) Length of the syrinx/C3 vertebral body length ratio (SLC3R—T2W and T1W sagittal images) Syrinx parameter measurements are depicted as green lines (A Reference measurements [spinal cord in (A–D)—C3 vertebra in (E)] are depicted as red lines (A it was noted where the syrinx was localized: cervical For extensive and multifocal localizations the most severely affected location (cervical or thoracic) was noted based on maximum SHRs Length of the syrinx was not measured for extensive of multifocal localizations Dogs were classified as “without” ORCS or “with” ORCS. Specific ORCS were recorded as present or absent (see Table 4 for specific ORCS) Table 1 summarizes the classification of dogs according to CM Classification of dogs based on MRI evaluations and owner-reported clinical signs A Kolmogorov-Smirnov test was used to assess if the data followed a normal distribution Differences between groups and associations between the presence of ORCS and signalment factors and quantitative syrinx measurements were analyzed by making use of a Mann-Whitney U test and Chi-squared test of independence where appropriate Odds ratios were calculated for significant results and reported with a 95% confidence interval (OR P < 0.05 were regarded as significant Correlations between T2W-based and T1W-based measurements were assessed by calculation of the Pearson correlation coefficient (r Analyses were performed using Microsoft Excel and R v4.3.1 A total of 871 Pomeranians were identified, of which 796 met the inclusion criteria. Table 2 includes the descriptive statistics regarding the study population The 796 dogs originated from 22 different countries with the majority (556; 69.9%) originating from either Russia (304; 38.2%) or The Netherlands (252; 31.7%) The origin of 114 (14.3%) dogs was unknown Five hundred and thirty-one (531; 66.7%) dogs were pure-bred dogs and 265 (33.3%) were not (i.e. proper documentation was lacking or the dog was not registered at any national kennel club) with 395 (49.6%) males of which 15 (3.8%) were neutered and 401 (50.4%) females of which 13 (3.2%) were neutered Median age was 2.19 years (range 0.17–11.02) Body weight of 385 dogs (48.4%) was available for analysis Median body weight was 3.3 kg (range 1.0–9.4) Descriptive statistics of the study population The prevalence of classifications of CM and SM are included in a contingency table (Table 3) The total prevalence of CM/SM Pomeranians included in this study the prevalence of CM/SM in Pomeranians with ORCS (i.e. those presented for specific evaluation for the presence or absence of CM/SM = 418/796; 52.5% of the total study population) and the prevalence of CM/SM in Pomeranians without ORCS (i.e those presented for screening purposes: 378/796; 47.5% of the total study population) are included here: - Total prevalence of CM was 54.9% (437/796) Total prevalence of SM was 23.9% (190/796) - Prevalence of CM in dogs with ORCS was 62.4% (261/418) Prevalence of SM in dogs with ORCS was 34.7% (145/418) - Prevalence of CM in dogs without ORCS was 53.4% (202/378) Prevalence of SM in dogs without ORCS was 11.9% (45/378) Contingency table including numbers and percentages of dogs combining CM and SM classifications Localization of SM was multifocal for 89/190 dogs (46.8%) 47/89 (52.8%) and 16/24 (66.7%) had more severe SM in the thoracic spinal cord than the cervical spinal cord ORCS are included in Table 4 A total of 376/796 (47.2%) dogs did not have ORCS and 420/796 (52.8%) did have ORCS The top 5 ORCS included (1) scratching with skin contact (3) spontaneous signs of pain (26.0% of dogs with ORCS) (4) persistent licking front and/or hind paws (22.6% of dogs with ORCS) (5) phantom scratching (22.6% of dogs with ORCS) Owner-reported clinical signs (ORCS) including number and percentage of dogs with specific ORCS Statistics for quantitative syrinx measurements are included in Table 5 All T1W-based measurements were smaller than T2W-based measurements and SLC3R were all higher when based on T2W-measurements than when based on T1W-measurements There was a statistically significant difference between all T2W-based measurements and T1W-based measurements (p ≤ 0.0274) T2W-based and T1W-based measurements for STWR and SLC3R were all very strongly correlated (r ≥ 0.90 Quantitative syrinx measurements of Pomeranians with syringomyelia (SM abnormal dogs) There was a significant difference between CM normal (CM0) dogs and CM abnormal dogs (CM1 and CM2) with regard to the presence or absence of ORCS (p < 0.0001) CM abnormal dogs were 1.9 times more likely to have ORCS than CM normal dogs (OR 1.9 There was no significant difference between CM1 and CM2 dogs (p = 0.4181) Five ORCS occurred significantly more often in CM abnormal dogs compared to CM normal dogs: (1) phantom scratching (OR 4.4 There were no specific ORCS that occurred significantly more or less often in CM1 compared to CM2 dogs There was a significant difference between SM normal (SM0) dogs and SM abnormal dogs (SM1 and SM2) with regard to the presence or absence of ORCS (p < 0.0001) SM abnormal dogs were 3.9 times more likely to have ORCS than SM normal dogs (OR 3.9 There was no significant difference between SM1 and SM2 dogs (p = 0.1902) Localization of SM was not associated with the presence or absence of ORCS (p = 0.2500) Five ORCS occurred significantly more often in SM abnormal dogs compared to SM normal dogs: (1) spontaneous signs of pain (OR 3.6 There were no specific ORCS that occurred significantly more or less often in SM1 compared to SM2 dogs Table 6 includes the odds ratios for having ORCS for comparisons between combined classifications of CM and SM Dogs classified as either CM or SM abnormal or both increased the likelihood of having ORCS compared to CM and SM normal dogs (OR between 1.5 and 4.9) Dogs having only CM were 1.5 times more likely to have ORCS than CM and SM normal dogs Dogs having SM were 4.4 times more likely to have ORCS than CM and SM normal dogs and 3.0 times more likely to have ORCS than CM abnormal/SM normal dogs Comparison between combined classifications of Chiari-like malformation (CM) and syringomyelia (SM) Specific ORCS that occurred significantly more likely in one group vs. the other are listed here and depicted in Figure 4 Odds ratios and 95% confidence intervals for specific owner-reported clinical signs Five ORCS occurred significantly more often in CM abnormal/SM abnormal dogs compared to CM normal/SM normal dogs: (1) phantom scratching (OR 8.6 Two ORCS occurred significantly more often in CM abnormal dogs compared to CM normal dogs: (1) phantom scratching (OR 4.3 p < 0.0001) and (2) scratching with skin contact Five ORCS occurred significantly more often in CM normal/SM abnormal dogs compared to CM normal/SM normal dogs: (1) phantom scratching (OR 4.9 There were no significant differences in any of the measurements (STWR – T2W and SLC3R – T1W) between SM abnormal dogs with ORCS and without ORCS There were also no significant differences in any of the measurements for SM abnormal dogs with or without specific ORCS Pomeranians originating from The Netherlands were 1.4 times more likely to be classified as CM abnormal than dogs from all other countries combined (OR 1.4 There were no significant differences in SM classification for dogs grouped according to country of origin Dogs with a pedigree were not significantly more or less likely to be classified as CM abnormal than dogs without a pedigree CM abnormal dogs without a pedigree were 1.9 times more likely to have a CM2 classification than CM abnormal dogs with a pedigree (OR 1.9 There were no significant differences in SM classification for dogs grouped according to pedigree status There were no significant differences in CM/SM classification for dogs grouped according to sex or neuter status range 0.4–11.0) were significantly older than CM normal dogs (median 2.0 years Dogs aged ≥ 1.5 years were 1.5 times more likely to be classified as CM abnormal than dogs aged < 1.5 years (OR 1.5 There was no significant age difference between CM1 and CM2 dogs range 0.8–11.0) were significantly older than SM normal dogs (median 2.1 years range 0.4–10.6) (p < 0.0001) Dogs aged ≥ 1.5 years were 3.2 times more likely to be classified as SM abnormal than dogs aged < 1.5 years (OR 3.2 There was no significant age difference between SM1 and SM2 dogs There were no significant associations between any of the quantitative syrinx measurements and age There were no significant associations between body weight and CM classification range 1.4–6.0) weighed significantly less than SM normal dogs (median 3.4 kg range 1.0–9.4) (p < 0.0001) Dogs with a body weight of < 2.5 kg were 6.3 times more likely to be classified as SM abnormal than dogs with a body weight of ≥2.5 kg (OR 6.2 There was no significant difference in body weight between SM1 and SM2 dogs This is the first large study evaluating CM/SM in the Pomeranian dog breed When interpreting the prevalence of CM/SM in Pomeranians in this study it must be taken into account that included dogs were not sampled at random from a population of Pomeranians Dog owners were mainly informed on the option of screening for CM/SM through social media platforms and breed clubs But in contrast to other large studies that often describe screening results of dog intended for breeding most of these Pomeranians were house-held dogs And although some owners came specifically for diagnostic imaging because they noted ORCS most dogs were presented for screening purposes The prevalence ranges for CM and SM reported here for dogs without and with ORCS were 53.4–62.4% and 11.9–34.7% respectively If a random selection of Pomeranians from the population had been employed the true prevalence would likely be included in these ranges This is because both dogs with and without ORCS would be part of such a random selection procedure it is clear that both CM and SM are prevalent in the Pomeranian dog breed but that there is also a large proportion of dogs without either of these disorders The latter subpopulation (CM normal/SM normal dogs) can be regarded as valid “controls” for studies focusing on possible genetic predispositions for CM and SM Both SM and CM were associated with the presence of ORCS the same 5 ORCS were identified to occur with increased likelihood in abnormal dogs: 1/phantom scratching these uncombined classifications do not account for differences between dogs with or without one of both these disorders CM abnormal/SM normal) and comparing the groups against one another it was evident that some specific ORCS were independently associated with each condition - phantom scratching and scratching with skin contact or both were associated with a CM abnormal classification (CM abnormal/SM normal vs and air licking were associated with a SM abnormal classification (CM normal/SM abnormal vs Such reports also delve into the pathophysiology of phantom scratching (i.e. spinal cord pathways involved in the scratch reflex) and hypothesize the influence of SM on its occurrence How the ORCS of phantom scratching in Pomeranians or other dogs with CM but without SM fits into these hypotheses remains to be determined including whether or not signs of pain where provoked vs spontaneous seemed to be an interesting differentiation to investigate in our study population we found a significant association for spontaneous signs of pain with SM and no significant association for provoked signs of pain regardless of which specific sign of pain is observed by an owner it can be valuable for assessing whether a dog is likely to have CM/SM or not Regarding localization of SM in Pomeranians, we found that 59.5% of dogs with SM had either extensive (both cervical and thoracic, continuous) or multifocal (both cervical and thoracic, discontinuous) syrinx formation. This finding is in line with results from studies in the CKCS, where SM is found in other than a cervical spinal cord location in many instances (30, 31) the thoracic spinal cord was most severely affected in most cases of extensive and multifocal localizations but inclusion of the whole spinal cord was not a requirement for this study we are unable to assess the exact distribution of SM in these dogs it is evident that SM in Pomeranians affects not only the cervical spinal cord but more caudal spinal cord segments as well An unknown portion of the owners of the included Pomeranians may have accidently misinterpreted their dog's behavior as indicative for CM and/or SM The authors therefore stress that MRI is needed to differentiate between ORCS associated with CM an/or SM and behavioral problems While assessment of the prevalence of PSOM was not an aim of this study no formal diagnosis of PSOM was made in any of the included Pomeranians in this study the prevalence of PSOM in the Pomeranian is likely to be very low This may reflect the differences in skull conformation between CKCS and brachycephalic breeds (e.g. and boxers) reported to be affected by PSOM so far we did find that T2W-based and T1W-based measurements were all very strongly correlated studies that also use T2W-based measurements are not necessarily invalid it does not seem logical to categorize dogs according to the measurements it is more logical to view dilatation of the central canal or presence of SM as abnormal and thus categorize dogs as SM normal and SM abnormal as we did in this study The C3 vertebral length was used as a reference to assess syrinx length As this study did not longitudinally assess quantitative syrinx parameters within individuals over time an effect of age on quantitative syrinx parameters cannot be excluded and requires future study The influence of body weight or other parameters accounting for size differences between dogs deserves more attention in future studies Selection of larger dogs may be one factor of use for breeders in selecting dogs less likely to give offspring with SM Low-field MRI studies may yield low quality images and influence assessment and measurements Although MRI studies with artifacts or insufficient image quality that did not allow for accurate assessments or measurements were excluded in this study we cannot rule out the possibility of misclassification for dogs scanned with low-field MRI machines low-field MRI machines for image acquisition does not by definition guarantee better image quality since image quality is not determined solely by field strength Among the strong points on this study are the large number of dogs that could be included and the fact that most Pomeranians were house-held dogs both with and without ORCS this study documents several associations for CM/SM classification and ORCS and signalment factors Veterinary clinicians may use these findings to increase the likelihood of correctly determining the presence or absence of CM/SM in Pomeranians though the diagnosis itself still necessitates diagnostic imaging (MRI) The raw data supporting the conclusions of this article will be made available by the authors The animal studies were approved by Animal Welfare Body Utrecht Written informed consent was obtained from the owners for the participation of their animals in this study The author(s) declare financial support was received for the research The IVC Evidensia research fund covered the article processing charges (publication fee) The authors would like to thank Erik Noorman of Dierenkliniek den Heuvel in Best for submitting cases for inclusion in the study The authors would also like to thank the Belgian and Dutch breeders' associations of Pomeranians and the owners for their cooperation in this study The author(s) declared that they were an editorial board member of Frontiers This had no impact on the peer review process and the final decision 1. ^Adapted from the BVA/KC scheme for CM grading Chiari Malformation/Syringomyelia Scheme (CM/SM Scheme) [Online] (2023). 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This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) *Correspondence: Koen M. Santifort, a29lbi5zYW50aWZvcnRAZXZpZGVuc2lhLm5s; Paul J. J. Mandigers, cC5qLmoubWFuZGlnZXJzQHV1Lm5s †ORCID: Koen M. Santifort orcid.org/0000-0001-7552-216X Paul J. J. Mandigers orcid.org/0000-0003-2547-6673