The efficacy of primidone in reducing severe cerebellar tremors in patients with multiple sclerosis.

Objectives: Cerebellar tremor is a disabling sign of multiple sclerosis (MS), and various kinds of treatments have been proposed with different results. Primidone is one of the medications, mostly advised for essential tremor. The aim of our study was to determine the tolerability and efficacy of primidone in reducing severe cerebellar tremor in patients with MS. Methods: Ten patients with severe cerebellar tremor were enrolled in this study. Primidone started with dose of 31.5 mg and gradually increased up to maximum of 750 mg/d. The severity of tremor was assessed with Activity of Daily Living (ADL), Nine-Hole Peg Test (NHPT), and Fahn Tremor Rating Scale (FTRS) at baseline and 2 follow-up studies after 6 and 12 weeks. Results: All outcome measures including ADL, FTRS, and NHPT of dominant and nondominant hands improved. The mean ADL changed from 51.8 at baseline to 36.8 after 12 weeks. FTRS was 14.8 at baseline, which reduced to 9.5 during this period. These changes were statistically significant. Although the time of the NHPT showed some improvement, it did not reach a statistically significant point after 6 weeks. The drug was well tolerated in all patients, and mild drowsiness reported by the patients disappeared at the end of the study. Conclusions: Our study showed that primidone is tolerable in MS patients and effectively reduces severe cerebellar tremor in such patients.