Chiari II Malformation

Etiology: abnormality of dorsal induction -> small posterior fossa -> inferior displacement of cerebellum, brainstem, slit like 4th ventricle
Imaging: Lacunar skull, cervicomedullary kink, tectal beaking, large massa intermedia, fenestrated falx, colpocephaly, 100% have lumbar meningomyelocele

Radiology Cases of Chiari II Malformation

Radiograph of lacunar skull in Chiari II malformation — Lateral radiograph of the skull shows a disordered arrangement of the inner table of the skull.

MRI of Chiari II malformation — Sagittal T1 MRI without contrast of the brain shows a small posterior fossa with downward cerebellar tonsil herniation and a small fourth ventricle. There is kinking of the spinal cord at the cervico-medullary junction. There is also agenesis of the body and rostrum of the corpus callosum.

MRI of Chiari II malformation and myelomeningocele — Sagittal T1 MRI without contrast of the brain (left) shows a small posterior fossa with downward cerebellar tonsil herniation and a small fourth ventricle. There is kinking of the spinal cord at the cervico-medullary junction. Sagittal (above right) and axial (below right) T2 MRI without contrast of the spine shows a low-lying conus medullaris with the spinal cord nerve roots terminating in a posteriorly located cerebrospinal fluid filled sac which is not covered by skin at the level of the L5-S1 vertebral bodies.