Effect of a cognitive task on postural control in patients with a clinically isolated syndrome suggestive of multiple sclerosis

Background. Patients with multiple sclerosis (MS) frequently experience poor postural control affecting mobility and/or cognitive impairment, even in the early stages of the disease. As postural control consumes attentional resources, it is essential to test stability during a cognitive task. Aim. To assess postural control and determine the effect of a cognitive task on balance in patients with a clinically isolated syndrome (CIS) suggestive of MS, within 3 months from onset. Design. Observational case control study Setting. Multiple Sclerosis Center and Institute of Motor Functions, Sheba Medical Center, Tel Hashomer, Israel Population. Fifty-two CIS patients, aged 35.2±1.3 years, disease duration of 54±6.2 days and Expanded Disability Status Scale (EDSS) of 1.7+0.2, participated in the study. The control group consisted of 28 age and gender matched healthy subjects. Methods. Stability was evaluated by the quantifying movement of the center of pressure (CoP) during standing under three conditions: eyes open, eyes closed, and while performing the modified Stroop test. Sway rate and CoP data was collected by a computerized force platform device. Results. After combining major postural control parameters, only 50% of the patients performed normally. Differences in postural variables were found between patients and healthy subjects (P<0.01). Both sway rate and standard deviation of the CoP in all test conditions were significantly higher in patients compared to controls. The cognitive task resulted in an elevated sway rate both in CIS patients and the control group when compared with the eyes open task. Within 3 months of the onset of neurological symptomatology, postural instability was detected in 50% of CIS patients using a dedicated balance measurement device. Conclusions. As these findings are associated with the very early phase of MS, it appears that the ongoing pathological disease process is already taking place with regard to the balance control system. Clinical Rehabilitation Impact. Identification of postural abnormalities in the early stages is important in order to establish proper intervention programs.