Spinocerebellar ataxia type 6 is a slowly progressive form of cerebellar ataxia with initial features that include lack of coordination and balance and dysarthria. Over time, vision problems including nystagmus and double vision, dysphagia, and tremors will develop. Average age of onset is in the 40s, and the rate of progression is typically slow with a normal lifespan.
SCA6 is inherited in an autosomal dominant pattern, and it is caused by a CAG trinucleotide repeat expansion in the CACNA1A gene. Repeat ranges are as follows: Normal (≤ 18), Intermediate (19), Pathogenic (≥ 20).