Improvement of multiple sclerosis-associated tremor as a treatment effect of natalizumab

Background Tremor is among the most physically disabling symptoms associated with MS. The effect of MS disease modifying therapies (DMTs) on the severity of MS tremor is unclear. Objective To compare the change over time in scores reflecting tremor severity between subjects treated with natalizumab and other disease modifying drugs. Methods Questionnaires were sent to North American Research Committee on MS registrants reporting mild or greater tremor on semiannual updates. Respondents on natalizumab and other MS therapies completed a survey which included tremor-specific scales to indicate tremor severity both currently and when the current therapy was initiated. Differences between natalizumab and non-natalizumab groups were compared using ANOVA. Results Surveys were returned by 567 registrants, including 202 taking natalizumab. Subjects on natalizumab were more likely to report tremor improvement (29.6%) than those never (15.2%) or previously (14.8%, p=0.0002) on natalizumab. Over a mean recall period of 6.2+4.6 years, the Tremor Related Activities of Daily Living score worsened by 1.8 points among natalizumab-treated subjects, 3.3 points among those previously on natalizumab, and 5.3 points among those who never took natalizumab (p=0.009). Conclusion Respondents taking natalizumab were more likely to experience tremor improvement than those taking other MS disease modifying therapies.