Somatosensory Evoked Potentials in Spinocerebellar Ataxia Type 3 and Type 10

Background Spinocerebellar ataxias (SCAs) are heterogeneous neurodegenerative disorders with variable phenotypes. Somatosensory evoked potentials (SSEPs) provide insights into the integrity of the dorsal-lemniscal pathway. Objective To evaluate SSEP findings in patients with SCA3 and SCA10 and compare their neurophysiological profiles. Methods We conducted a cross-sectional study including 20 SCA3 patients and 20 SCA10 patients under follow-up at a tertiary ataxia clinic in Southern Brazil. Clinical assessment comprised demographic, genetic, and phenotypic characterization, including the Scale for the Assessment and Rating of Ataxia (SARA). SSEPs were recorded bilaterally after median and tibial nerve stimulation, assessing latencies and amplitudes of N9, N20, N21, and P40 potentials, as well as interpotential intervals. Examinations were classified as normal or abnormal, and abnormalities were categorized. Results Abnormal SSEPs were detected in 18 SCA3 patients (90%) and in 3 SCA10 patients (15%) (p < 0.001). In SCA3, abnormalities predominantly involved central generators. In contrast, most SCA10 patients exhibited normal SSEPs, with only a few isolated cortical responses and interval abnormalities. No significant associations were found between SSEP abnormalities and demographic, clinical, imaging, or genetic variables in either group. Conclusions SCA3 shows widespread somatosensory dysfunction, whereas SCA10 patients, particularly in Southern Brazil, show preserved SSEPs consistent with a pure cerebellar phenotype. These findings highlight distinct neurophysiological signatures in SCAs, reinforcing their heterogeneity and supporting SSEPs as potential biomarkers for differential characterization.