Immediate Motor Control Enhancement via Pallidothalamic Tract (PTT) Circuit Ablation: A Dual-Target MR-Guided Focused Ultrasound Approach for Tremor-Dominant Parkinson's Disease

Abstract

Background: Stepwise dual-target MR-guided Focused Ultrasound (dtMRgFUS) is a novel treatment for Parkinson's disease (PD), targeting both Ventral Intermediate Nucleus (VIM) and the pallidothalamic tract (PTT). While previous studies have demonstrated its 12-month efficacy, this study focuses on the immediate effects of additional PTT lesioning after VIM ablation. Methods: Twenty patients (age 69.3 ± 8.9 years) with both tremor and akinetic rigidity received dtMRgFUS when they were off medications, with a series of primary and secondary outcome measures on the table. We performed unilateral VIM first, with subsequent ipsilateral PTT ablation in the same session. The primary outcomes were the off-status sub-score of the Unified Parkinson's Disease Rating Scale part III (UPDRS-III) and the Clinical Rating Scale for Tremor (CRST). In addition, we compared the outcome changes from the baseline to the first VIM treatment with the changes from VIM treatment to the subsequent PTT treatment. Results: During the procedure, the severity of tremor, rigidity, and bradykinesia improved significantly (all p < 0.05 by paired t-test) after both VIM and PTT treatment. Notably, major improvement of parameters was noted after VIM lesioning (all p < 0.02 by paired t-test), except for rigidity, which showed significant changes immediately after PTT lesioning (p < 0.02 by paired t-test). Conclusion: These findings highlight the immediate therapeutic impact of PTT lesioning following VIM lesioning in the same treatment session, reinforcing its role as a crucial add-on target for managing refractory PD symptoms beyond tremor. This dtMRgFUS approach offers a more comprehensive motor benefit, particularly for patients with rigidity.