Ventral intermediate nucleus-posterior subthalamic area double-target deep brain stimulation in essential tremor plus dystonia: A potential therapeutic approach

Essential tremor (ET) with soft neurological signs, such as questionable dystonia, was defined as ET plus by the Movement Disorder Society (MDS). Ventral intermediate nucleus (Vim)-posterior subthalamic area (PSA) double-target deep brain stimulation (DBS) is a novel method of inhibiting tremors in patients with ET. Despite the established efficacy of the Vim and PSA as individual DBS targets in ET, their combined application in ET plus dystonia remains understudied. This study aimed to investigate the efficacy of Vim-PSA double-target DBS in patients with ET plus dystonia, and explore the potential mechanisms of DBS in ET plus dystonia. We reviewed 13 patients with ET plus dystonia who underwent bilateral Vim-PSA DBS between March 2022 and January 2025. Two patients were excluded because of their high BFMDRS scores, which indicated overt rather than “questionable” dystonia. The severity of tremor and dystonia was assessed using the Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS) and Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS), respectively. Clinical outcomes were evaluated by comparing optimal follow-up stimulation-on state with the baseline values. Electrodes, nuclei, and fiber tracts were reconstructed using Lead-DBS software. All patients underwent bilateral interleaving stimulation (ILS) mode DBS to ensure optimal efficacy. Following high-frequency stimulation (150–185 Hz) of the Vim and PSA, FTMTRS and BFMDRS scores declined by 82.07 % and 73.92 %, respectively. The anterior-ventral margin of the Vim and the realm of the fasciculus cerebellothalamicus (fct) in the PSA were effective stimulation regions. Gait and postural disorders were common adverse effects. Our findings suggest that Vim-PSA double-targeting DBS is a potential therapeutic approach for ET plus dystonia. High-frequency bilateral ILS may be an effective stimulation pattern for alleviating tremors and dystonia.