Cognitive dysfunction in patients with spinocerebellar ataxia type 6.

The aim of this study was to assess the cognitive functions of patients with spinocerebellar ataxia type 6 (SCA6). We examined 13 patients with genetically confirmed SCA6 and 13 healthy control subjects matched for age, years of education, global cognitive status, and intellectual ability. We administered verbal memory (word recall and word recognition), executive function (digit span, category and letter fluency, Frontal Assessment Battery, and Trail Making Test-A and B), and visuospatial construction (figure copying) tests. We found that the patients with SCA6 had significantly lower scores on the demanding word recall and letter fluency tests compared to the control subjects, while word recognition was well preserved in the patients with SCA6. The other executive functions tested, as well as visuospatial construction, were preserved in the SCA6 group. However, although memory encoding and storage processes were preserved, the retrieval of memorized information concerning frontal function might be selectively affected in patients with SCA6 compared to in control subjects. The impaired word recall and letter fluency noted in patients with SCA6 were interpreted as being related to a word-retrieval disability. Such dysfunctions may be attributed to damage in the frontal-cerebellum circuit owing to SCA6.