Optimizing Deep Brain Stimulation in Essential Tremor: A Randomized Controlled Trial for Target Consideration

The thalamic ventral intermediate nucleus (VIM) is a well-established target for deep brain stimulation (DBS) in the treatment of essential tremor (ET). Increasing data indicate that the posterior subthalamic area (PSA) may be superior, but high-level evidence is limited. We aimed at further comparing the intraindividual efficacy and side effect profile of PSA vs VIM DBS in ET.

In this randomized, double-blind, crossover trial, 4-contact DBS leads were bilaterally implanted with single-trajectory covering the VIM and PSA. Patients were randomized postsurgery to 2 groups, receiving VIM stimulation (4-7 months) and then PSA stimulation (8-11 months) or vice versa. The primary end point was the difference in improvement from baseline to the end of the VIM vs PSA DBS period in the total score of the Fahn-Tolosa-Marin Tremor Rating Scale (FTM-TRS).

Ten patients with medically refractory ET were enrolled, and 9 completed the study. The difference between reduction of FTM-TRS total score in the PSA vs VIM DBS period was -7.4 (95% CI: -28.5 to 13.7, P = .328). Clinical benefit was achieved at significantly lower stimulation intensity under PSA DBS. Furthermore, PSA DBS provided greater improvement in head tremor subscore of FTM-TRS (PSA vs VIM: -2.2, P = .020) and disease-specific quality of life (PSA vs VIM: -13.8, P = .046) and induced fewer speech (Dysphonia Severity Index score: P = .043; diadochokinetic rate: P = .007; VDI score: P = .005) and gait disturbances compared with VIM DBS. Seven patients remained with PSA DBS after the crossover phase.

Our study confirms that PSA-DBS is comparable with VIM-DBS in suppressing tremors, superior in improving disease-specific quality of life, and possibly more effective in reducing head tremor.