[A case of spinocerebellar ataxia type 6 with its initial symptom of episodic ataxia-like phenotype].

: We reported a Japanese case of spinocerebellar ataxia type 6 (SCA6) with episodic ataxia type 2 (EA2) phenotype. A 28-year-old woman was admitted to our hospital because of episodic unsteadiness of gait and dysarthria for 4 years. Neurological examination revealed truncal ataxia and dysarthria during attacks, but no abnormal findings in interictal phases. A brain MRI showed no obvious cerebellar atrophy, whereas proton MR spectroscopy (1H-MRS) disclosed decrease of the N-acetylaspartate/ceatine (NAA/Cr) ratio in the cerebellar hemisphere. We identified the expanded 22 CAG repeats without a missense mutation in the CACNA1A gene. After one year from the discharge, her gait ataxia became gradually obvious even in the interictal phase. To our knowledge, although a few foreign papers had reported the SCA6 cases with EA2 phenotype, there is no particular report on such cases in Japan. 1H-MRS, in addition to CAG repeats analysis, might enable us to differentiate SCA6 from EA2, because the latter showed no decrease of NAA/Cr ratio in cerebellar hemisphere according to the previous reports.