Static posturography across the EDSS scale in people with multiple sclerosis: a cross sectional study

Background: Posturography is considered the gold standard objective measure of standing postural control in people with multiple sclerosis (PwMS). This reliable tool provides quantitative data related to risk of falling and white and gray matter brain damage due to MS. Nevertheless, it remains unclear whether and to what extent, postural control declines throughout the disease process. We therefore examined the impact of disability on posturography measures in PwMS. Methods: In this cross-sectional study, the data pool was divided into seven levels of disability based on the Expanded Disability Status Scale (EDSS) score. The study group comprised 464 PwMS, mean disease duration was 6.2 (SD = 7.5) years and mean age 42.6 (SD = 14.1). Static postural control parameters were obtained from the Zebris FDM-T instrumented Treadmill (Medical GmbH, Germany). Results: A significant positive correlation between the EDSS and posturography parameters was found. Scores for the ellipse area, center of pressure (CoP) path length and sway rate with eyes open were Spearman's rho = 0.512, 0.527, 0. 528; (P-value < 0.001), respectively. Non-significant differences were observed between the EDSS subgroups at the lower end of the spectrum (EDSS 0-2.5) in all posturography parameters. In contrast, MS patients with an EDSS score of 3.0-3.5 demonstrated a significant increase in the ellipse area with eyes open (similar to 108 %) and closed (similar to 169 %), CoP path length with eyes open (similar to 83 %) and closed (similar to 88 %) and sway rate with eyes open (similar to 39 %) and closed (similar to 148 %), compared with those who scored within the range of 0-2.5 in the EDSS. Non-significant differences were observed between MS patients with an EDSS score of 3.0-5.5. MS patients with an EDSS score of 6.0-6.5 were significantly poorer in 4 (out of 6) balance measures compared to other disability subgroups. Conclusions: Posturography CoP trajectories are appropriate outcome measures indicating disability deterioration in PwMS.