Novel Biomarker of Balance Impairment in Minimally Impaired Individuals with MS

Background: Traditional measures of balance lack sensitivity to subtle balance impairments in multiple sclerosis (MS).

Objectives: Non-linear analyses, which examine the time dependent structure of posture may provide a novel biomarker for balance impairment in minimally impaired individuals with MS.

Methods: This secondary analysis included a sample of 30 individuals with MS who were sway matched to 36 healthy controls similar in age and gender. Participants stood on a force platform for two trials of 30 seconds with eyes open. Postural sway was indexed by total sway area (SA) and mean velocity along the antero-posterior (MV_AP) and mediolateral (MV_ML) axes. The time dependent structure of the COP was indexed with approximate entropy (ApEn) of sway in both AP and ML directions. T-tests and Mann-Whitney U Tests were utilized to analyze differences between groups.

Results: Per design, there were no differences in traditional sway metrics between the MS and control groups. The MS group had lower ApEn values compared to the control group for sway along the ML axis (U=376 p=.03).

Conclusions: The results indicate that individuals with MS with the same amount of postural sway as healthy controls had greater time dependent structure in their sway patterns. This investigation highlights the utility of non-linear analyses when assessing balance impairment in MS samples that present with minimal impairment.