Multiple Sclerosis and Postural Control: The Role of Spasticity

Sosnoff JJ, Shin S. Motl RW. Multiple sclerosis and postural control: the role of spasticity. Arch Phys Med Rehabil 2010:91:93-9. Objectives: To examine the association between spasticity and postural control in subjects with multiple sclerosis (MS). Design: Cross-sectional. Setting: Motor control laboratory. Participants: Subjects with MS (n=16, 2 male) and age and sex-matched subjects (n=16) participated in the investigation. All subjects with MS had Expanded Disability Status Scale scores between 0 and 4.5 and modified Ashworth scale scores between 1 and 3. Interventions: Not applicable. Main Outcome Measures: Postural control was measured with a force platform that quantifies ground reaction forces and moments in mediolateral and anteroposterior directions. Postural control was indexed with anterior-posterior sway range, medial-lateral sway range, 95% elliptical area of the deviations of center of pressure (COP), velocity of COP sway, and the frequency at which 95% of spectral profile was contained. Participants with MS further underwent assessment of the soleus Hoffman reflex (H-reflex) as an index of spasticity. Results: Cluster analysis on H-reflex data identified groups of MS participants with high spasticity (n=7) and low spasticity (n=9). There were no differences in age, duration of MS, and disease severity between MS groups. There were no differences in anterior-posterior sway range between any of the groups. The high spasticity group had greater COP area, velocity, and mediolateral sway compared with the low spasticity and control group, and the low spasticity group had postural control values between the high spasticity and control groups. Conclusions: The pattern of results suggests that spasticity contributes to postural deficits observed in MS.