Loss in gait automaticity reflects in higher frontal cortical activity and gait impairments during obstacle crossing in people with multiple sclerosis

Background: The presence of walking impairment in people with Multiple Sclerosis (PwMS) is very common. Recent studies suggest that gait change in PwMS is to compensate for the damage caused by multiple sclerosis (MS). However, these gait adjustments seem to have no positive effects, leading to a higher number of falls. Also, this damage contributes to a loss in gait automaticity in this population, which requires a greater cortical source. Complex gait tasks, such as crossing an obstacle, can increase the use of the cortical source and represent better gait of daily living activities. Aim: This study aims to investigate the gait behavior and cortical activity of the frontal cortex in PwMS during unobstructed and obstacle gait. Material and Methods: Fifteen relapsing-remitting PwMS (EDDS=2.2 [+ or -] 1.3pts and PDDS=1.7 [+ or -] 0.9pts, 33 [+ or -] 7y, 1.67 [+ or -] 0.08m, 75 [+ or -] 13kg) and 15 healthy-matched controls (CG, 31 [+ or -] 5y, 1.68 [+ or -] 0.08m, 69 [+ or -] 10Kg) participated in the study. The participants walked, in a self-selected speed, under two gait conditions: unobstructed (UC) and obstacle avoidance (OA) (15cm). They performed 20 randomized trials (10 trials per condition). Ten tridimensional cameras with a sampling frequency of 200Hz were used to acquire the movements of thirty-nine reflective markers positioned on the participants according to the Plug-in-Gait Full Body model (Vicon[R]) and two markers placed on the top of the obstacle. The following gait parameters were calculated: step length, width, velocity and duration and percentage of double support (DS), as well as, the horizontal and vertical distance from leading and trailing foot to the obstacle. In the UC, the average of 5 steps was account for in each trial, while for the OA, the analysis was divided into two periods: approaching phase (AP- average of the three steps before the obstacle avoidance) and crossing phase (leading and trailing step). An electroencephalogram, with a sampling frequency of 1024Hz and a cap of 64 active electrodes, was used to measure the cortical activity. The band frequencies delta, theta, alpha, beta, and gamma were analyzed. Two-way ANOVAs with factor to group (PwMS x CG) and gait condition (UC x AP) were used to compared gait parameters. Also, one- way ANOVA with factor for the group was used for comparing the crossing phase and vertical and horizontal distance to the obstacle. For the EEG analysis, a different ANOVA two-way with group and gait conditions (UC x OA) factor, with repeated measures for the last factor was used. Results: PwMS presented lower step length and velocity.