Two-year Follow-up Results of Magnetic Resonance Imaging-guided Focused Ultrasound Unilateral Thalamotomy for Medication-refractory Essential Tremor

OBJECTIVE: To investigate the long-term efficacy and safety of magnetic resonance imaging-guided focused ultrasound (MRgFUS) unilateral ventral intermediate nucleus (Vim) thalamotomy for medication-refractory essential tremor (ET). METHODS: We performed MRgFUS left-sided Vim thalamotomy for 10 medication-refractory ET patients (8 men and 2 women, aged 67.1±17.5 years, all right-handed). We followed them for 2 years using the clinical rating scale for tremor (CRST) and the quality of life in essential tremor questionnaire (QUEST). RESULTS: Right-handed tremor improved immediately after the left Vim thalamotomy in all patients. The tremor became re-exacerbated in 2 patients by 6 months after treatment; however, an approximately 60% decrease in the average CRST score of the right hand persisted until 2 years. On the other hand, the average CRST score of the left hand and the average QUEST score showed no improvement. Headache was the most common adverse event during the sonication (8 patients), followed by a floating sensation (4 patients). On the other hand, sensory disturbances (4 patients) and gait instability (4 patients) were observed after the treatment, but most of them were mild and transient. There were no delayed adverse events. CONCLUSION: MRgFUS unilateral Vim thalamotomy could be adopted as one of the therapeutic options for intractable ET. Further improvement of tremor in the targeted hand or contralateral Vim thalamotomy may be necessary to improve the quality of life.