Posterior subthalamic area stimulation for essential tremor: Long-term efficacy and the challenging balance of stimulation-related side effects.

Introduction Deep brain stimulation (DBS) targeting the posterior subthalamic area (PSA) is a more recent target to manage medication-refractory essential tremor (ET), with some studies suggesting enhanced tremor control and more favorable side-effects profile compared to traditional ventral intermediate nucleus (Vim). This study aims to assess the long-term efficacy and side effect profile of PSA-DBS in ET patients.Methods Fourteen ET patients who underwent bilateral PSA-DBS were evaluated using the Fahn-Tolosa-Marin Tremor Rating Scale preoperatively, at 12 months, and at the last follow-up (range 10-63 months). Within the first 6 months postoperatively, systematic monopolar contact testing was performed to determine individual thresholds for tremor suppression and adverse effects. Standardized neurological examinations and blinded video assessments were used to document stimulation-induced side effects.Results Tremor was significantly reduced postoperatively, allowing a 59% reduction at 12 months and 39% at last follow-up. Common side effects at last follow-up included dysarthria (93%), ataxia (57%), and gait disturbances (79%), mainly mild to moderate in severity. Additionally, stimulation-induced dyskinesia occurred in 21% of patients. Patient satisfaction remained high, with 85.7% reporting significant improvements.Conclusions Bilateral PSA-DBS demonstrates sustained tremor reduction but can frequently present stimulation-induced side-effects, highlighting the importance of careful long-term monitoring and programming adjustments.