Spinocerebellar ataxia (SCA) is a family of dominant hereditary cerebellar ataxias that progressively degenerate the cerebellum and its pathways, causing postural instability and incoordination. Despite the importance of assessing functionality in individuals with SCA, data on performance in these tests is scarce.

To assess the impact of SCA over functionality based on disease progression and symptom severity by comparing the performance of individuals with SCA to health ones.

Thirty-nine individuals with SCA were invited to participate. Four decline the invitation. Thirty healthy participants, matched in gender and age, were also recruited. Individuals with SCA was assessed through the Scale of the Assessment and Rating of Ataxia (SARA) and the Inventory of Non-Ataxia Signs (INAS) to characterize disease gravity and presence of non-ataxic symptoms, respectively. All participants were evaluated with the Five times sit to stand (5TSTS), 10m walk test (10MWT) and Functional reach test (FRT) with accelerometry. During FRT, a linear artifact was acquired using signals from 3D accelerometers integrated into an Apple smartphone (Iphone 13, designed by Apple in California USA, assembled in Brazil) positioned in the lumbar region. The individuals with SCA were subdivided into three groups, according to the scores obtained on the SARA scale associated to the level of dependence when performing ADL (minimum-moderate, maximum, and severe-total dependence). To compare the control group and individuals with SCA subgroups, a one-way ANOVA was performed, followed by posttests in case of a significant main effect. Analysis of accelerometer recording during FRT was performed by comparing the groups using a t test for independent samples.

For the analyzes of the 5TSTS, FRT and 10MWT, data from the 35 individuals with SCA as well as 30 height controls were used. For the analysis of the movement pattern during FRT with accelerometry, data from only 28 individuals with SCA and 22 controls were included due to the enough quality of signals found needed to analysis. There was a main effect when comparing groups for all variables: 5TSTS (P < 0.001); TAF (P < 0.001); Time in the 10MWT (P < 0.001); and number of steps in the 10MWT (P < 0.001). The distances achieved in the FRT by the control group were significantly higher than those of the maximum and severe-total dependence groups, while for the minimal-moderate dependence group, there were no significant differences compared to the control group. Regarding the TAF movement phases, there were no significant differences for any variable (P < 0.132).

The results indicate that SCA impacts gait and postural control. In general, individuals with SCA with greater dependence for ADL and worse disease severity had the worst performance in the tests. Although the distances reached in the FRT were smaller for patients with SCA, the movement phases did not show significant differences between them, indicating that the movement pattern is not significantly altered.

These results help to improve the treatment of individuals with SCA, highlighting the changes that can cause disease progression, identifying the areas in which patients have more difficulties, and helping in designing their plans of assistance.