Chiari III Joseph Junewick, MD FACR 07/02/2010 History Newborn with suboccipital mass. Diagnosis Chiari III Additional Clinical Surgery-Skin covered suboccipital cystic mass confined by the dura. Pathology-Leptomeningeal tissue with few nodular neuroglial elements. Discussion Chiari III malformation is an extremely rare anomaly. The pathogenesis of malformation is not clear, however, underdistension of the embryonic ventricular system secondary to the abnormal neurulation might result in a hypoplastic posterior fossa and consequently in the caudal displacement of brain stem and cerebellum in Chiari malformations. The low occipital or skull base osseous defects and associated cephaloceles probably develop due to the failure of induction of enchondral bone by incomplete closure of neural tube, or due to the failure of ossification centers to fuse completely in Chiari III malformations. Patients with Chiari III malformation most commonly present with a cystic mass of low occipital and/or high cervical location. The infants suffer from hydrocephalus, frequently associated with the evidence of increased intracranial pressure, within the first few months of life. The clinical findings related to the compression of cerebellum, brain stem and lower cranial nerves. The prognosis of patients is usually poor. Chiari III malformation is characterized by the hermiation of posterior fossa contents through a low occipital or upper cervical osseous defect. Upper cervical vertebrae show an incomplete fusion of posterior arches, most commonly at the level of C1 vertebra. The patients with Chiari III malformation will also show imaging findings related to Chiari II malformation. Findings MR-Sagittal T1 and axial and coronal T2 images demonstrate occipitocervical meningocele with dysrhaphism. Note cervicomedullary kink, tectal beak, cerebellar hypoplasia, callosal dysgenesis and ventricular dysmorphism. Reference Cakirer S. Chiari III malformation: Varieties of MRI appearances in two patients. Clinical Imaging (2003); 27(1):1-4.
Sponsored By Disclaimer This teaching site is partially funded by an educational grant from GE Healthcare and Advanced Radiology Services, PC. The material on this site is independently controlled by Advanced Radiology Services, PC, and GE Healthcare and Spectrum Health have no influence over the content of this site Content Download Agreement The cases and images on this website are owned by Spectrum Health. Permission is granted (for nonprofit educational purposes) to download and print materials to distribute for the purpose of facilitating the education of health professionals. The authors retain all rights to the material and users are requested to acknowledge the source of the material. Site Disclaimer This site is developed to reach healthcare professionals and medical students. Nothing this site should be considered medical advice. Only your own doctor can help you make decisions about your medical care. If you have a specific medical question or are seeking medical care, please contact your physician. The information in this website is provided for general medical education purposes only and is not meant to substitute for the independent medical judgment of a physician relative to diagnostic and treatment options of a specific medical condition. The viewpoints expressed in these cases are those of the authors. They do not represent an endorsement. In no event will Advanced Radiology Associates, PC, Spectrum Health Hospitals (Helen Devos Children's Hospital) or GE Healthcare be liable for any decision made or action taken in reliance upon the information provided through this website.