Chiari III malformation: varieties of MRI appearances in two patients.

Chiari III malformation is an extremely rare anomaly, which is characterized by the herniation of posterior fossa contents, i.e., cerebellum, brain stem and fourth ventricle, and in some cases upper cervical spinal cord through a low occipital and/or upper cervical osseous defect. We report different presentations of Chiari III malformation in two unusual cases to show the diversity of imaging findings of this rare malformation.