Dual-Lesion Magnetic Resonance-Guided Focused Ultrasound Thalamotomy of the Ventralis Intermedius Nucleus and Ventralis Oralis Anterior and Posterior Nuclei for the Treatment of Tremor-Dominant Parkinson's Disease: Outcomes in 6 Treated Cases.

Background And Objectives: The ventralis intermedius nucleus of the thalamus (Vim) is the preferred target in magnetic resonance-guided focused ultrasound (MRgFUS) for tremor-dominant Parkinson's disease (TdPD), but some patients with TdPD have persistent tremor after Vim thalamotomy. Basal ganglia outflow through the ventralis oralis anterior and posterior (Voa/p) may be responsible. We present 6 cases with dual Vim and Voa/p MRgFUS thalamotomies for TdPD resistant to Vim treatment.

Methods: Six patients with TdPD underwent Vim MRgFUS thalamotomy with persistent intraprocedural tremors (resting 5 patients and/or action tremors 1 patient), who then underwent Voa/p thalamotomy during the same procedure. Demographic and treatment information was collected. Tremor was evaluated using the Clinical Rating Scale for Tremor (CRST)-A and CRST-B.

Results: Six patients were included in the study. The mean age was 71.5 years (SD = 2.7), 5 were male (83.3%), 4 had right-sided treatments (66.7%), and 1 had a repeat treatment (16.7%). The mean follow-up was 11 months (range 6-18 months). Mean Vim lesion coordinates from the posterior commissure were X = 13.9 mm, Y = 7.5 mm, and Z = 2 mm. Voa/p were targeted by moving approximately 3 to 5 mm anterior and 3 mm medial to the initial Vim lesion. Mean Voa/p lesion coordinates were X = 11.7 mm, Y = 11.3 mm, and Z = 2.3 mm. Five patients with resting tremor had improved postural/action tremor after Vim thalamotomy (mean CRST-B 8.8 improved to 0.4) but unsatisfactory control of resting tremor. After Voa/p thalamotomy, resting tremor improved in all 5 patients (mean CRST-A hand score 3.6 improved to 0.0). For the patient without resting tremor, postural/action tremor improved after Voa/p thalamotomy (CRST 3 improved to 1). All improvements were sustained at last follow-up except for 1 patient, who regressed to preoperative postural/action and resting tremor by 6 months. At last follow-up, 2 patients reported speech (33.3%) and 3 patients reported balance/gait (50%) changes.

Conclusion: Patients with TdPD with tremor refractory to Vim MRgFUS thalamotomy may benefit from a secondary lesion in Voa/p although incidence of adverse effects may be increased.