Deep brain stimulation for tremor recurrence after focused ultrasound thalamotomy - retrospective case series and literature review.

INTRODUCTION: MRI-guided focused ultrasound (MRgFUS) thalamotomy has demonstrated efficacy in tremor relief; however, tremor recurrence may occur. For patients experiencing such recurrence, deep brain stimulation (DBS) presents a viable alternative. This study reports our findings on the application of DBS following MRgFUS. METHODS: We evaluated four right-handed patients diagnosed with essential tremor (ET), with a mean age of 65 years (range 47-76); Three of them male and one female. Tremor was assessed using Fahn-Tolosa-Marin score (CRST) and hemi-CRST scores, while quality of life was assessed using quality of life in essential tremor questionnaire (QUEST). A responder analysis using ≥50% improvement cut-off was used for evaluation. These patients exhibited tremor recurrence at a mean time of 5 months post-MRgFUS. DBS electrodes were implanted bilaterally traversing the ventro-intermediate (VIM) nucleus of the thalamus and the posterior subthalamic area (PSA) in two patients, one patient had electrodes implanted to the VIM alone and another patient had the PSA as an only target. RESULTS: Responder analysis of hemi-CRST scores for the treated hand post-DBS showed improvement in patient 3 and a borderline positive response in patient 1 (0.44), whereas patients 2 and 4 had negative values, suggesting worsening post-DBS. Total CRST responder analysis after DBS showed improvement in patients 1, 3, and 4, while patient 2 showed a negative response. Quality-of-life outcomes were heterogeneous: patient 1 demonstrated sustained QUEST improvement after both MRgFUS and DBS, patients 2 and 4 showed worsening, and patient 3 showed improvement after MRgFUS but worsened after DBS. Adverse events included three patients developed stimulation induced gait disturbance, two of them also had stimulation induced dysarthria. CONCLUSION: The effects of DBS following MRgFUS in ET patients with tremor recurrence are not well characterized. Our single-center experience suggests that DBS can be effective in select patients with manageable adverse events, highlighting the importance of careful patient selection. Further studies are warranted to comprehensively evaluate this sequential treatment approach.