Spinocerebellar ataxia type 3 (SCA-3)/Machado-Joseph disease (MJD), the most common autosomal dominant ataxia, affects many regions of the brain and spinal cord. Similar to SCA-1, SCA-2, SCA-6, SCA-7, and SCA-17, the mutation consists of a pathogenic translated cytosine-adenine-guanine (CAG)