On-demand deep brain stimulation for essential tremor: a report on four cases.

Deep brain stimulation (DBS) is an established therapy for essential tremor (ET), but loss of efficacy due to tolerance can occur. Our objective was to evaluate if it is feasible to use DBS only on-demand and if this would prevent tolerance. We report on the effects of left-side thalamic DBS in 4 ET patients who were instructed to switch on stimulation only when using their right hand for motor tasks and were followed-up to 30 months after surgery. The patients were capable of using DBS only on-demand (DBS use of 22.0+/-13.5%/day). DBS led to a stable suppression of right arm tremor throughout the follow-up. No problems associated with tolerance such as tremor rebound or late therapy failure occurred. In comparison to publications stating that ET patients had been using DBS continuously during the daytime, the use of on-demand DBS saves battery life, which delays surgical replacement of the stimulator. Thus, on-demand DBS saves money, may help to prevent tolerance, and should be adopted for the long-term treatment of ET patients. (c) 2005 Movement Disorder Society.