Cerebellar vermis hypoplasia - non progressive congenital ataxia: clinical and radiological findings in a pair of siblings.

We describe the clinical and radiological findings of a pair of siblings with cerebellar vermis hypoplasia and compare them with the literature. Both of them present pregnancies and deliveries uneventful and both presented some grade of hypotonia, ataxia, ocular motor abnormalities and mild motor delay and slurred speech. These siblings meet many of the criteria described in non-progressive congenital ataxia in which can occur familial cases with cerebellar atrophy, including vermis hypoplasia. As differential diagnosis we compare them with related syndromes and with Joubert's syndrome which main radiological finding on MRI is vermis hypoplasia associated with "molar tooth" appearance. The correct answer for these cases will only be possible by molecular genetics.