Balance and body movement strategies for controlling postural stability in people with spinocerebellar ataxia type 3

Abstract

Introduction: Postural instability with an excessive body sway is a disabling manifestation in spinocerebellar ataxia (SCA). However, whether the larger body sway reflects distinct movement strategies for postural control in this population remains uncertain. Objective: To describe the control of postural stability of people with SCA3 using body sway and movement strategy analyses derived from posturography, and to compare these findings with healthy subjects. Methods: Posturography was performed under static standing with eyes open/closed tasks. Postural stability was assessed using elliptical area (Area) and average velocity (Vavg). Spatial patterns (single-, double-, or multi-centered) were derived from the number of highdensity regions (nHDR) in the three-dimensional statokinesigram. Results: Twenty-three participants with SCA3 (7 men, 16 women, age 47±11 years) and 102 healthy participants (34 men, 68 women; age 44±22 years). Repeated measures two-way analysis-of-variance showed a vision-by-group interaction effect for Area (F1,122=28.831, p<0.001, h2=0.037) and Vavg (F1,123=59.367, p<0.001, h2=0.073); sway area and velocity were higher in the SCA3 group and increased under eyes-closed condition, with a higher increase in the SCA3 group. A main effect for group (F1,123=11.702, p<0.001, h2=0.061) but not vision (F1,123=2.257, p=0.136, h2=0.005) was found for nHDR. Spatial patterns were different between groups under trials with eyes closed (c22,125=7.46, p=0.023) but not open (c22,125=2.026, p=0.363), with an overall shift from single-centered to double- or multicentered spatial patterns in this test condition. Conclusion: Compared to healthy subjects, a larger body displacement and velocity in people with SCA3, mainly under visual constraints, are not related to the predominance of either ankle-hip movement strategies.