Why patients with multiple sclerosis perceive improvement of gait during treatment with natalizumab?

Gait impairment is one of the common manifestations of multiple sclerosis (MS) and contributes to a loss of quality of life. Natalizumab, an anti-α4 integrin monoclonal antibody, has been shown to have an effect in treatment of MS, reducing relapses and inflammatory lesions. Aim of our study was to assess how patients perceive gait impairment over the first year of treatment with natalizumab and what is the objective correlate of this change. This is an open-label prospective observational study. Subjective gait evaluation was measured by Multiple Sclerosis Walking Scale-12 (MSWS-12). Objective gait assessment included Timed 25-Foot Walk Test (T25FW) and spatiotemporal parameters of gait measured by a GAITRite instrument during a self-selected speed of walking (normal walk) and a fast speed of walking (fast walk). We analysed data of 50 patients with a relapsing-remitting form of MS, median EDSS 3.5 (range 1.5-5). MSWS-12 score significantly decreased between the baseline and month 12 of treatment (p < 0.001). Walking velocity and step length were significantly improved in Normal walk tests (p < 0.001). During the Fast walk tests, a step length and a double support time of the gait cycle were significantly improved (p = 0.001). Change in MSWS-12 score confirmed the clinically significant improvement of gait in patients with MS treated with natalizumab for 1 year. The analysis of spatiotemporal gait parameters has shown a significant improvement in self-selected gait velocity and step length.