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Spinocerebellar ataxia type 8 (SCA8) is a subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term) characterized by cerebellar ataxia and cognitive dysfunction in almost three quarters of patients and pyramidal and sensory signs in approximately a third of patients. Prevalence is unknown. However, SCA8 accounts for approximately 3% of ADCA cases. Other features include dysexecutive disorders and commonly psychiatric disorders. SCA8 is caused by a trinucleotide repeat on 13q21 that produces a polyglutamine expansion in the ataxin 8 gene (ATXN8). SCA8 is thought to result from RNA-mediated neurotoxicity. Prognosis is relatively good. Disease usually progresses slowly over decades. Life expectancy is not significantly reduced. |