Factors involved in long-term efficacy of deep brain stimulation of the thalamus for essential tremor

Although nucleus ventralis intermedius stimulation has been shown to be safe and efficacious in the treatment of essential tremor, there is a subset of patients who eventually lose benefit from their stimulation. Proposed causes for this phenomenon include tolerance, disease progression, and suboptimal location. The goal of this study was to assess the factors that may lead to both stimulation failure, defined as loss of meaningful tremor relief, and less satisfactory outcomes, defined as leads requiring voltages>3.6 V for effective tremor control. The authors present their clinical outcomes from 31 leads in 27 patients who had effective tremor control for >1 year following nucleus ventralis intermedius stimulation. All patients postoperatively had a mean decrease in both the writing and drawing subscales of the Fahn-Tolosa-Marin Tremor Rating Scale (p