Unique cerebellar-cerebral form of autosomal recessive ataxia.

We describe a unique condition affecting two siblings with a form of progressive spinocerebellar ataxia. After a period of very slowly progressive ataxia, the patients developed an extremely accelerated progression of the condition which consisted of cerebellar ataxia, seizure, progressive dementia and spastic tetraparesis. Age of onset was variable at 7 to 18 years. Brain magnetic resonance image (MRI) showed marked atrophy of the cerebellum and cerebrum with strikingly preserved brainstem dimensions. Biochemical or molecular genetic analysis was performed in an elder sister and her parents to exclude known forms of familial spinocerebellar ataxia, dentatorubral-pallidoluysian atrophy (DRPLA), progressive myoclonic epilepsy, and some metabolic disorders which could have a similar phenotype. The mode of inheritance appears to be autosomal recessive. We think that the affected siblings may have a new type of autosomal recessive cerebellar ataxia.