Electrophysiological evaluation of spinocerebellar ataxias 1, 2 and 3

IntroductionSubclinical neuropathy is an important feature of spinocerebellar ataxias (SCA) but the true prevalence and electrophysiological characteristics in genetically proven patients of SCA 1, 2 and 3 are largely unknown.MethodsWe prospectively compared the electrophysiological characteristics of neuropathy in 61 genetically confirmed cases of SCA (SCA1 = 28, SCA2 = 16 and SCA3 = 17). Nerve conduction studies were performed in at least one sensory and one motor nerve, in right upper and lower limb using standard methods.ResultsThe mean age of patients and duration of illness were comparable among SCA groups (mean age (years): SCA1—34.1 ± 12.7, SCA2—35.2 ± 13.9 and SCA3—38.1 ± 11.3; mean duration (years): SCA1—5.4, SCA2—6.1, and SCA3—4.4). Electrophysiological evidence of neuropathy was highest in SCA1 (96.4%), followed by SCA3 (94.1% and SCA2 (87.5%). A mixed sensorimotor neuropathy was commonly observed in all the subgroups (SCA1—78.6%, SCA2—50%, and SCA3—41.2%). Pure sensory neuropathy was most common in SCA3 (55.9%), followed by 31.3% in SCA2 and 17.9% in SCA1. Pure motor neuropathy was uncommon (6.3% in SCA2 and none in SCA1 and SCA3).ConclusionsElectrophysiological evidence of mixed sensorimotor and pure sensory neuropathy is seen in all the three subtypes of SCAs, while pure motor neuropathy is distinctly uncommon.