Postural control in multiple sclerosis: effects of disability status and dual task.

Persons with Multiple Sclerosis (PwMS) have postural control impairments. The simultaneous performance of a cognitive task while maintaining an upright posture (i.e. dual task) negatively influences postural control in PwMS with mild disability. This investigation compares the effect of simultaneous cognitive task performance on postural control in PwMS with mild and moderate disability. Forty-five PwMS were divided into groups based on Expanded Disability Status Scale (EDSS) scores: mild (EDSS: 2.0-3.5) and moderate (EDSS: 4.0-6.5) disbaility. Each participant underwent posturography testing during a quiet baseline condition and a cognitive task condition (i.e. dual task). The cognitive task was a word list generation (WLG) task. Median sway velocity, root mean square displacement, and sway area were calculated for each condition. The moderate disability group had significantly worse postural control than the mild disability group. There was an increase in postural sway in the dual task condition. There were no significant task-by-group interactions on postural control. Postural control declines with disability status and is negatively affected by a concurrent cognitive task in PwMS. The dual task cost during a balance task is not different between disability levels and this conflicts with findings for the effect of dual tasking during walking in PwMS.