CHIARI MALFORMATIONS RADIOLOGY CT MRI 

Group of congenital defects ass varying degree caudal displacement of post fossa contents into cervical canal.
Caudal tonsillar herniation (≥ 5 mm below BO line)
Pointed, peg-like tonsils with angled folia
“Crowded” foramen magnum on axial
Small, shallow posterior fossa
Inferiorly herniation medulla, vermis and choroid plx of 4th v into cervical canal
Cervicomedullary spur”
upward displacement of cerebellum and vermis --“Towering” and “creeping” cerebellum
compression of quadrigeminal plate by superiorly displaced cerebellum --Tectal beaking
“fourth ventricle--- elongated and thin “Soda straw”
Hydrocephalus (90%)
Lacunar skull