A case of Arnold-Chiari malformation type II

The Chiari type II malformation (Arnold-Chiari malformation) is a complex congenital malformation of the brain, nearly always associated with myelomeningocele, and the most common serious malformation of the posterior fossa. This condition has skull, dural, brain, spinal, and spinal cord manifestations, including downward displacement of the medulla, fourth ventricle, and cerebellum into the cervical spinal canal, as well as elongation of the pons and fourth ventricle, probably due to a relatively small posterior fossa.