Long-term follow-up of thalamic deep brain stimulation for essential tremor - patient satisfaction and mortality

Background: Ventral intermediate thalamic nucleus (VIM) deep brain stimulation (DBS) is an effective treatment for tremor, but there is limited data on long-term efficacy and mortality after VIM-DBS. Here we report the analysis of patient satisfaction and mortality in all patients treated in our center 1996-2010 with VIM-DBS for essential tremor (ET). Methods: Forty-six consecutive patients were included in this study. Medical records were reviewed, and a follow-up questionnaire was sent to all surviving patients. Results: Seventy percent of all possible participants (26 patients) answered the questionnaire. Follow-up time for the responding patients was median 6.0 years (2-16). Median self-reported score on visual analogue scale of the initial postoperative effect on tremor was 8.5 (0.1-10), with a significant reduction to 7.4 (0-10) at follow-up (p = 0.001). Patients reported a median score of 10 (0-10) for overall patient satisfaction with VIM-DBS treatment. Eight patients (17%) died after median 8.9 years (0.6-15) after surgery, at median age 77.4 years (70-89). One patient (2%) committed suicide seven months after the operation. Calculated standard mortality ratio among ET patients was 1.3 (CI 0.6-2.6), similar to the general population. Conclusion: We found no significant increase in mortality in this cohort of VIM-DBS operated ET patients compared to the general population in Norway. The patients reported high long-term satisfaction and continuing effect of VIM-DBS on tremor even after many years. VIM-DBS therefore seems to be an effective symptomatic long-term treatment of ET. However, one patient committed suicide. Only one other suicide has previously been reported after VIM-DBS. It is therefore still unclear whether VIM-DBS increases suicide risk.