Comparative Study of Focused Ultrasound Unilateral Thalamotomy and Subthalamotomy for Medication-Refractory Parkinson's Disease Tremor.

Background: Unilateral focused ultrasound ventral intermediate thalamotomy (Vim-FUS) is effective in treating Parkinson's disease (PD) tremor. Ultrasound ablation of the subthalamic nucleus (STN-FUS) has demonstrated efficacy in improving all cardinal motor features of PD, including tremor.

Objective: To compare the efficacy in parkinsonian tremor control between Vim-FUS and STN-FUS.

Methods: Retrospective, two-center study including consecutive PD patients with medication-refractory tremor who underwent unilateral Vim-FUS or STN-FUS between June 2015 and August 2022. Patients scored ≥2 for postural and/or resting tremor on the most affected body side in the off-medication state. The primary outcome was the between-group difference in tremor improvement on the treated side at 12-month follow-up, including a responder's analysis. Data regarding safety, global motor status, and dopaminergic requirements were also collected. Group comparisons used repeated measures ANOVA with Bonferroni correction; statistical significance for P < 0.05.

Results: Among 175 patients treated at the two sites, 63 were included (23 Vim-FUS, 40 STN-FUS). At baseline, both groups were equivalent in disease duration (6.7 ± 3.8 vs. 6.1 ± 3.4 years, P = 0.48) and tremor severity (5.7 ± 1.5 vs. 5.9 ± 2.5, P = 0.7). While the benefit in tremor was equivalent between the groups at 4 months (P = 0.15), tremor reduction was greater in STN- FUS patients at 12 months (4.4 ± 2.0, 95% CI 3.7-5.0 compared with 2.7 ± 3.7, 95% CI 1.1-4.3 for Vim-FUS, P = 0.012). In 47.5% (19/40) of STN-FUS patients tremor was completely abolished versus 8.7% (2/23) in Vim-FUS patients (P < 0.01). Most adverse events were mild (91%) and resolved by 12 months.

Conclusions: STN-FUS and Vim-FUS significantly improved medication-refractory PD tremor; however, subthalamotomy might have greater and more sustained effect. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.