Association of age of onset and CAG repeat number with the ratio of age of onset to onset NAA value.

R-NAA and V-NAA = right and vermis hemispheric N-acetyl aspartate/creatine ratio; SARA, scale for the assessment and rating of ataxia; SCA, spinocerebellar ataxia.Results are shown as standardized regression coefficients via regression analysis with or without adjusted SARA score. Greater absolute value of standardized regression coefficients indicates greater association between dependent variable and predictor.*P**P***P