Cerebellar vermian clefts disconnecting the hemispheres: a different entity unassociated with Joubert's syndrome.

In the consecutive evaluation of 3000 cranial MR imaging and CT examinations in pediatric patients we found 13 patients with cerebellar vermian clefts. Three of these belonged to asymptomatic patients, and 10 to those with Joubert's syndrome. Although, the only known condition associated with a developmental cleft in the cerebellar vermis is the Joubert's syndrome, the MR imaging findings in the three asymptomatic patients with complete vermian clefts disconnecting the two hemispheres suggested that this represents a distinct entity of a "vermian defect", which presents as a single lesion in a sporadic fashion with a frequency of 0.1%.