Introduction: A recent study showed technical feasibility to improve symptoms in patients with essential tremor utilizing MR guided focused ultrasound to create a lesion in the thalamus. A randomized, controlled, double-blinded trial was therefore conducted to demonstrate safety and efficacy of this treatment.

Methods: Seventy-six patients with severe medically refractory essential tremor were randomized to receive either unilateral MR guided focused ultrasound thalamotomy or sham lesion (3:1) after meeting inclusion/exclusion criteria for study participation. Primary outcome measure was upper limb tremor score on a subset of the Clinical Rating Scale for Tremor (CRST), for the arm contralateral to thalamotomy 3 months post treatment. Secondary measures included safety, treated arm tremor score at one year, total tremor score at 3 and 12 months, quality of life, and disability scores. Outcome measurements were obtained at 1, 3, 6, and 12 months following treatment.

Results: Mean contralateral hand tremor improved by 47% (18.1 to 9.6 on CRST subscores, p<0.001) compared to baseline, and remained significantly improved at 12 months (10.6, p<0.001). Sham treatment arm and ipsilateral limb to treatment showed no statistical improvement at 3 months. Quality of life scores improved by 54% in the treatment group compared to 1% in the sham at 3 months. Total disability at 3 months statistically improved only in the treatment group (16.5 to 6.2, p<0.001), and remained improved at 12 months (6.3, p<0.001). One serious treatment related adverse event (treated hand hypesthesia) was observed in the 12 months following treatment.

Conclusions: MR guided focused ultrasound thalamotomy can be performed in awake patients with a high degree of safety, and produces significant, durable improvements in contralateral hand tremor scores, disability, and quality of life.

Patient Care: Data from this trial will be evaluated by the FDA to determine if MR guided thalamotomy is safe and effective in improving tremor symptoms for patients with Essential Tremor.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of MR guided focused ultrasound in the treatment of patients with Essential Tremor. 2) Discuss, in small groups, the risks and benefits of focused ultrasound thalamotomy in treating tremor. 3) Identify an effective treatment for patients with medically refractory Essential Tremor.

References: Elias WJ, Huss D, Voss T, et al. A pilot study of focused ultrasound thalamotomy for essential tremor. N Engl J Med 2013; 369:640-8.