Asymptomatic Dandy-Walker variant in an adult.

A 50-year-old fisherman presented with numbness of the left hand and headache after a fall on the deck of a boat. Myelography revealed protrusions of the disks of C-7 and L-4. Computed tomography of the brain incidentally disclosed moderate hydrocephalus and hypoplasia of the inferior cerebellar vermis without cystic formation in the posterior fossa. The patient never developed evidence of cerebral involvement. Several entities associated with agenesis or hypoplasia of the cerebellar vermis have been described, all of which accompany abnormal clinical symptoms or signs attributable to cerebral involvement. This case is unique in that the patient has been entirely asymptomatic with this abnormality since birth.