Increased visual reliance for postural control in multiple sclerosis: preliminary evidence from task-related cortical...

Balance impairment is one of the most disabling symptoms in multiple sclerosis (MS), yet the underlying cortical mechanisms remain poorly understood. This exploratory study investigated how postural demands modulate brain activity in MS.

Seven individuals with MS (mean age: 51.1 ± 9.7 years; 5 women; median Expanded Disability Status Scale: 5.5, IQR: 4.5-6.0) and seven age- and sex-matched healthy controls (mean age: 51.0 ± 9.6 years) performed three static balance tasks on a force plate: quiet stance with eyes open, quiet stance with eyes closed, and narrow stance with eyes open. Electroencephalography (EEG) and center of pressure (COP) were simultaneously recorded. Group differences were assessed using Linear Mixed Models. Significant effects are reported with false discovery rate (FDR)-corrected q-values, and otherwise with uncorrected p-values.

MS patients demonstrated greater postural sway than healthy controls, with FDR-corrected group × condition interactions across COP parameters (semi-partial R ² = 0.225-0.441; all q < 0.05), most pronounced during eyes closed (semi-partial R ² = 0.124-0.282; all p < 0.05). Resting-state EEG revealed no consistent group differences except for an uncorrected elevation of occipital theta power in MS patients (p = 0.017; r = -0.76). During stance, uncorrected group × condition interactions indicated that MS patients exhibited a greater task-induced decrease of theta, alpha, and beta power relative to their matched resting baseline compared to healthy controls (semi-partial R ² = 0.193-0.318; all p < 0.05). These effects were specific to the eyes-closed condition.

These preliminary findings are consistent with an increased reliance on visual information for postural control in MS, accompanied by a task-related cortical desynchronization specifically upon visual deprivation. The observed effect sizes, while likely subject to inflation given the small sample size, suggest that oscillatory EEG parameters warrant investigation in larger confirmatory studies.