Corticospinal tract involvement in Spinocerebellar ataxias type 1, 2 and 3 characterized by motor evoked potentials and diffusion MRI.

INTRODUCTION

Spinocerebellar ataxias (SCAs) types 1, 2, and 3 are the most common autosomal dominant SCAs, characterized by neurodegeneration in the cerebellum, brainstem, and basal ganglia. However, corticospinal tract involvement remains underexplored using combined electrophysiological and neuroimaging approaches. This study aimed to investigate the electrophysiological and imaging characteristics of SCA subtypes.

METHODS

A total of 23 SCA1, 21 SCA2, and 40 SCA3 patients, along with 27 healthy controls, were enrolled. All subjects underwent neurological examination and motor evoked potential (MEP) testing. Additionally, SCA patients underwent diffusion kurtosis imaging (DKI). Correlations between central motor conduction time (CMCT) and corticospinal tract diffusion metrics, as well as clinical parameters, were analyzed.

RESULTS

All SCAs demonstrated prolonged CMCT in both upper and lower limbs. SCA3 patients exhibited significantly reduced MD values relative to SCA2 (P = 0.0437). Conversely, both SCA1 and SCA2 patients showed significantly lower FA, MK, and KFA values compared to SCA3. In SCA3 patients, lower limb CMCT correlated with DKI metrics (FA: r = -0.4815, P < 0.05; MK: r = -0.4411, P < 0.05) and disease duration (r = 0.5647, P = 0.0003), but not with streamline counts.

CONCLUSION

This study identifies distinctive electrophysiological and microstructural corticospinal tract abnormalities across SCA cohorts. The observed correlations of CMCT with DKI parameters and disease duration in SCA3 suggest its potential as a biomarker for monitoring disease progression.