Vagus nerve stimulation for essential tremor - A pilot efficacy and safety trial

Objective: To assess the safety and efficacy of vagus nerve stimulation (VNS) for essential tremor (ET). Methods: This was a pilot open-treatment trial at three centers, with masked videotape tremor assessments. Inclusion required a severity score of 3 or 4 on the Tremor Rating Scale (TRS) in one or both hands. At baseline, tremor was assessed with TRS and Unified Tremor Rating Assessment (UTRA), accelerometry, and a videotape protocol. The VNS device was implanted with leads placed around the left cervical vagus nerve. Stimulation was adjusted over 4 weeks before the repeat tremor assessments. Two raters masked to the study visit scored the videotapes. Results: Nine subjects participated, with a mean age of 65 years and a mean age at onset of tremor of 24. Investigators rated hand tremor as mildly improved (TRS 2.3+/-0.7 during VNS vs 3.0+/-0.4 during baseline, p=0.06). Accelerometry-measured total power improved 50.2+/-31.8% (p<0.01). Videotape tremor scores were highly correlated between the masked raters and revealed no changes in tremor scores with treatment. VNS was well tolerated, with the most common adverse events being stimulation related. Conclusions: VNS was judged by investigators to mildly improve upper extremity tremor. This finding was not confirmed in videotape scoring by masked raters. VNS is not likely to have a clinically meaningful effect on ET.