Long-term outcome following magnetic resonance imaging-guided focused ultrasound unilateral thalamotomy for medication-refractory essential tremor

Objective: To investigate the long-term outcome 5 years after transcranial magnetic resonance imaging-guided focused ultrasound (MRgFUS) unilateral ventral intermediate nucleus (Vim) thalamotomy for essential tremor (ET), following our interim reports. Methods: This was a prospective and open-labeled study involving a single center. Ten medication-refractory ET patients (8 men and 2 women, aged 67.1 +/- 17.5 years, all right-handed) underwent left MRgFUS Vim thalamotomy. They were assessed using the Clinical Rating Scale for Tremor (CRST) and the overall health and quality of life (QOL) scale of the Quality of Life in Essential Tremor Questionnaire (QUEST). Additionally, we assessed safety issues during the study period. Results: Right-hand tremor improved immediately after the procedure in all patients. The right-hand CRST score remained significantly improved by 60.2% and 33.5% from baseline at both 1- and 5-years post-treatment, respectively (both p < 0.05). On the other hand, the left-hand CRST score and the overall QOL score of QUEST showed no improvement. Adverse events during and immediately after the procedure were mild and reversible. We observed no delayed adverse events. Conclusion: MRgFUS unilateral Vim thalamotomy is adopted as one of the therapeutic options for intractable ET. Further investigation of the methodology for accurate targeting and sonication is important to improve long-term outcomes involving a larger number of patients. In addition, not only unilateral but also bilateral Vim thalamotomy may be necessary to achieve a better quality of life.