Spinocerebellar ataxias type 1, 2 and 3: a study of heart rate variability

Objective To detect cardiac autonomic dysfunction, using analysis of heart rate variability in genetically defined spinocerebellar ataxias (SCA). Materials and methods Consecutive RR intervals were analyzed for time- and frequency- domain parameters in 22 genotypically proven SCA patients (SCA1 = 11, SCA2 = 6 and SCA3 = 5) and compared with that of age- and gender- matched controls. Results Reduction in the standard deviation of RR interval (RR_SD) was seen in 72.7% of SCA patients. There was a reduction in both the parasympathetic and sympathetic parameters in SCA without any change in the ratio of low- to high- frequency power. In SCA1, there was a significant negative correlation between RR_SD and duration of illness but not with the CAG repeat lengths of the abnormal allele. Small sample size of SCA2 and SCA3 precluded similar comparison. Conclusions Cardiac autonomic dysfunction, predominantly parasympathetic, was seen in SCA, and the severity correlated with the duration of illness in SCA1.