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.