Fig. 3

Linear regression analyses of the reduction ratio of the M/P area ratio over time. Longitudinal changes in the M/P area ratio were calculated by serial brain MRI obtained from the NSDD(+) (n = 5) (a) and NSDD(−) (n = 9) (b) groups. Male patients in the NSDD(−) group were placed into the male patients with NSDD(−) group (n = 6, NSDD(−)m) (c). x represents the time interval (year) from the day of the first MRI examination to the second or later MRI examination in each patient. The dependent variable y represents the reduction ratio of the M/P area ratio. The M/P area ratio derived from the first MRI examination was defined as 1, and the M/P area ratio derived from the second or later MRI was divided by the M/P area ratio derived from the first MRI in each patient. M/P, midbrain-to-pons; NSDD, nigrostriatal dopaminergic dysfunction; NSDD(+), SCA31 with NSDD; NSDD(−), SCA31 without NSDD; NSDD(−)m, male patients with SCA31 without NSDD; SCA31, spinocerebellar ataxia type 31