Static Balance in Hereditary Spastic Paraplegias: a Cross-sectional Study

Background: Motor and somatosensory pathways dysfunction due to degeneration of long tracts in hereditary spastic paraplegias (HSP) indicates that postural abnormalities may be a relevant disease feature. However, balance assessments have been underutilized to study these conditions. Research question: how does the static balance of individuals with HSP with eyes open and closed differ from healthy controls, and how does it relate to disease severity? Methods: : This cross-sectional case-control study assessed the static balance of 17 subjects with genetically confirmed HSP and 17 healthy individuals, evaluating the center of pressure (COP) variables captured by a force platform. The Root-mean-square of velocities and mean of displacements amplitudes in mediolateral and anteroposterior axes were correlated with disease severity. Results: : All COP parameters performances were significantly impaired in HSP subjects compared to controls (p<0.001 for all comparisons). COP with eyes open and closed differed for all variables within the HSP-group, whereas in the control-group, differences were observed only for anteroposterior velocity and amplitude. Spastic Paraplegia Rating Scale (SPRS) presented moderate direct correlations with the most COP variables (Rho=-0.520 to - 0.736). Significance: HSP individuals presented significant postural instability with eyes open and to a greater extent with eyes closed, corroborating the clinical findings of somatosensorial and proprioceptive pathways dysfunction. The degrees of proprioceptive and motor impairments are mutually correlated, suggesting that similar pathophysiological mechanisms operate for the degeneration of these long tracts. COP parameters can be seen as disease severity biomarkers of HSP, and they should be assessed in future clinical trials.