DBS for Essential Tremor: Aligning Thalamic and Subthalamic Targets in One Surgical Trajectory.

Objective: Evaluating aligning ventral intermediate nucleus (VIM) and posterior subthalamic area (PSA) in one surgical trajectory for deep brain stimulation (DBS) in essential tremor (ET). Background: Both VIM DBS and more recent PSA DBS have shown to suppress tremor for ET. Considering it is currently not clear which target is optimal for individual patients we wanted to explore both during intraoperative test stimulation. For this, we applied the technique of aligning both targets in one surgical trajectory. Design/Methods: Technical aspects of planned trajectories, intraoperative test stimulation findings, final lead placement, target used for chronic stimulation and adverse and beneficial effects were evaluated. Results: In 17 patients representing 33 planned trajectories (16 bilateral, one unilateral), we successfully aligned VIM and PSA targets in one surgical trajectory in 26 (79%) trajectories (15 patients). Average trajectory distance between both targets was 7.5 mm (range 6-10). In 17 aligned trajectories, optimal intraoperative tremor suppression was obtained in PSA. During follow up, optimal active electrode contacts of these leads were in or just above PSA in the large majority of cases. In the remaining 9 aligned trajectories, optimal intraoperative tremor suppression was obtained in VIM (n = 3) or the area just above PSA (n = 6). During follow up, most active electrode contacts of these latter six leads were in VIM. Overall, successful tremor control was achieved in 74% of contralateral body sides, or 69% of patients. Stimulation-induced dysarthria or gait ataxia occurred in, respectively, 56% and 19%. No difference in tremor suppression efficacy or side effect profile was noted between aligned and non-aligned leads, nor between the different anatomical locations of active stimulation. Conclusion: Alignment of VIM and PSA for DBS in ET is well feasible and enables intraoperative exploration of both in one single trajectory. This facilitates optimal positioning of electrode contacts in these adjacent areas, where multiple optimal points of stimulation can be found. In the majority of aligned leads, both optimal intraoperative tremor suppression and active contacts used for chronic stimulation were in or just above PSA. [ABSTRACT FROM AUTHOR]