Dysarthria in Spinocerebellar Ataxia Type 3: Prevalence and Disease Progression

Background: Spinocerebellar ataxia type 3 (SCA3), a common genetic disorder, results from an expanded CAG repeat in the ATXN3 gene. It often leads to dysarthria, which impacts patients' quality of life. Yet, there is limited research on how dysarthria's prevalence relates to clinical features and disease progression in SCA3. Method: We retrospectively analyzed 183 SCA3 patients, dividing them into dysarthria and non-dysarthria groups based on their “speech disturbance” subscale scores from the Scale for the Assessment and Rating of Ataxia (SARA). Patients with a score of zero were classified as non-dysarthria, while those with higher scores were classified as dysarthria. Spearman's rho tested factor associations with dysarthria; logistic regression identified dysarthria risk factors. Kaplan–Meier curves were employed to demonstrate the onset of dysarthria over the disease duration. Results: We identified a 78.7% prevalence of dysarthria among SCA3 patients. Patients with dysarthria had significantly higher SARA scores ( p < .001) and longer disease durations ( p < .001). Disease duration showed the strongest association with the occurrence of dysarthria ( r = .319, p < .001) and emerged as an independent prognostic factor ( p < .001). By the eighth year, 50% of patients exhibited dysarthria, with the highest incidence occurring in the later stages of the first decade. Conclusions: Dysarthria is common in SCA3 patients, with disease duration as the main prognostic factor. The prevalence of dysarthria increases as the disease progresses, particularly during the later stages of the first decade. These findings underscore the need for early intervention to address dysarthria in SCA3 patients, especially as they approach critical disease milestones.