The Association Between Diplopia and Clinical Phenotypes in Spinocerebellar Ataxia Type 3

Background: Spinocerebellar ataxia type 3 (SCA3) is a rare monogenic hereditary neurodegenerative disease. It is the most common form of spinocerebellar ataxia worldwide, with diplopia being one of its most frequent symptoms. Diplopia has been reported to be associated with clinical phenotypes and daily living activities in various neurodegenerative diseases. Objectives: Our objective is to investigate the association between diplopia and the clinical phenotype of SCA3. Methods: We conducted a retrospective analysis of 182 patients with SCA3. Participants were categorized into two groups based on the presence or absence of diplopia: the diplopia group and the non-diplopia group. We used the Mann-Whitney U test to analyze phenotypic differences between the groups. We performed univariate and multivariate logistic regression analyses to identify risk factors for the development of diplopia. Additionally, we conducted a multivariate linear regression analysis to determine the association of diplopia with age at onset (AAO), severity of ataxia, and disease progression. Results: In this study, the frequency of diplopia among subjects was 45.6%, while 54.4% of subjects did not experience diplopia. The diplopia group exhibited significantly higher ICARS scores (p = 0.002) . We found that visual impairment (p = 0.027, OR = 2.22) was a risk factor for diplopia and diplopia significantly affected the severity of ataxia (β = 7.77, p = 0.003). Conclusion: Diplopia is common in patients with SCA3. Visual impairment has been identified as a risk factor for developing diplopia. Additionally, diplopia is associated with the severity of ataxia, necessitating intensive focus and interventions in the care of SCA3 patients.