Postural Sway and Spatio-Temporal Parameters of Gait in Multiple Sclerosis

Background: There is evidence of alterations in postural sway and gait in persons with multiple sclerosis (MS). Postural sway further has been associated with gait and gait variability (i.e., fluctuations in gait parameters between steps measured by standard deviation [SD] and co-efficient of variation [CV]) in older adults. This is important as postural sway might represent a target for mitigating impairments in gait and its variability as two metrics of fall risk in people with MS.

Objectives: This study examined the association between antero-posterior and medio-lateral sway with average and variability metrics of spatio-temporal parameters of gait in older adults with MS and a fall history.

 Methods: The sample included 33 older participants [Mean (SD) - 60 (6.1) years] with a definite diagnosis of MS who had fallen one or more times over the past year. Participants walked across a 16-foot instrumented gait mat with sensors arranged in a grid-like pattern to identify the pressure applied by each foot during normal walking. The software program calculates the average and absolute variability (SD) of step length, step width, and step time whereas the relative variability (CV) of step length, step width, and step time are calculated by taking the ratio of SD by mean. Participants then underwent a postural sway measurement by having the participants stand on a foam surface while they were equiped with a swaymeter. Postural sway was indexed by sway length along the antero-posterior (AP) and medio-lateral (ML) axes. The relationship between AP and ML postural sway with mean and gait variability spatio-temporal parameters were examined using one-tailed, Spearman rho rank-order correlation coefficients (r_s).

 Results: Overall, AP postural sway had significant correlations with the average step time (r_s  = .349, p = .023) and variability of spatio-temporal parameters indexed by SD and CV in terms of step length (SD: r_s  = .310, p = .04; CV: r_s  = .307, p = .04) and step time (SD: r_s = .483, p = .002; CV: r_s = .498, p =.002). There were no significant correlations between ML postural sway and gait metrics.

Conclusions: These data suggest that AP postural sway is associated with variability of gait, and this might represent a target of rehabilitation interventions designed towards fall risk reduction in older adults with MS who have a fall history.