Investigation of Adaptation to Successive Postural Perturbations in Patients with Multiple Sclerosis

Objective: It is well known that abnormal automatic postural responses impair balance control in patients with multiple sclerosis (PwMS) and these responses can be ameliorated with training. However, the difference between patients with MS and the healthy population on the adaptation capacity of postural responses to perturbations remains unclear. The aim of the present study was to evaluate the adaptation capability to postural perturbations in PwMS and to reveal differences between healthy controls. Materials and Methods: Sixty-nine ambulatory PwMS with Expanded Disability Status Scale (EDSS) scores below or equal to 5.5, and 61 healthy subjects were recruited for the study. Adaptation Test with NeuroCom Smart Balance Master System, Berg Balance Scale (BBS), and EDSS were administered. The adaptation test was performed in the toes-up and toes-down directions; five consecutive perturbations were given for each direction. The sway energy score was calculated for postural sway that were released during these perturbations. Results: According to the adaptation test results, healthy volunteers' sway energy scores were significantly lower than those of PwMS in five consecutive perturbations (toes-up p<0.001, toes-down p<0.001). Healthy volunteers and PwMS were adapted in trial 3 for both directions and sway energy score changes in time were found similar between the groups. The toes-up adaptation rate in PwMS (17%) was statistically lower than in healthy group (31%) (p=0.026), and the toes-down adaptation rate was similar (p=0.175). The BBS and EDSS had significant correlations with average toes-up sway energy scores (r=-0.402, r=0.392, respectively). Conclusion: Ambulatory PwMS have preserved adaptation to automatic postural responses, with higher sway energy scores. A low adaptation rate in the toes-up direction should be taking into account when planning the motor strategy training.