SPINOCEREBELLAR ATAXIA TYPE-6 WITH POSITIONAL VERTIGO AND ACETAZOLAMIDE RESPONSIVE EPISODIC ATAXIA

The SCAB mutation, a small expansion of a CAG repeat in a calcium chan nel gene CACNA1A, was identified in three pedigrees. Point mutations i n other parts of the gene CACNA1A were excluded and new clinical featu res of SCA6 reported-namely, central positional nystagmus and episodic ataxia responsive to acetazolamide. The three allelic disorders, epis odic ataxia type 2, familial hemiplegic migraine, and SCA6, have overl apping clinical features.