[Clinical features and MRI findings in spinocerebellar ataxia type 31 (SCA31) comparing with spinocerebellar ataxia type 6 (SCA6)].

Since the discovery of spinocerebellar ataxia type 31 (SCA31) gene, we identified 6 patients whose SCA type had been unkown for a long period of time as having SCA31 in our hospital and realized that SCA31 is not a rare type of autosomal dominant spinocerebellar ataxia in this region. We examined and compared the clinical details of these six SCA31 patients and the same number of SCA6 patients, finding that some SCA31 patients had hearing loss in common while there are more wide range and complicated signs of extra cerebellum in SCA6 such as pyramidal signs, extrapyramidal signs, dizzy sensations or psychotic, mental problems. There is a significant difference in the number of extracerebellar symptoms between SCA31 and SCA6. There are differences also in MRI findings. Cerebellar atrophy starts from the upper vermis in SCA31, as well as some SCA types, whereas the 4th ventricule becomes enlarged in SCA6 even in the early stage of disease. We suggest that these differences in clinical and MRI findings can be clues for accurate diagnosis before gene analysis.