Introduction: Magnetic resonance guided focused ultrasound (MRgFUS) is a non-invasive procedure that has recently been investigated as a new treatment modality for essential tremor (ET). Although an initial report demonstrated ~50% reduction in tremor at one year(1), the long-term durability of the procedure has not yet been evaluated. This study reports results at a 2- year follow-up after MRgFUS thalamotomy for ET.

Methods: A total of 76 patients with moderate-to-severe ET, who had not responded to at least two medications, were enrolled in the original randomized study of unilateral MRgFUS thalamotomy and evaluated using the clinical rating scale for tremor. Sixty-seven of the patients continued in the open-label extension phase of the study with monitoring for 2 years. Nine patients did not continue to the two year endpoint. All patients remaining in the study at each follow-up period were analyzed for improvement in tremor persistent adverse effects.

Results: Mean hand tremor score at baseline (19.8±4.9, 76 patients) improved by 55% at 6 months (8.6±4.5, 75 patients). The improvement in tremor score from baseline was durable at 1 year (53%, 8.9±4.8, 70 patients) and at 2 years (56%, 8.8±5.0, 67 patients). Similarly, the disability score at baseline (16.4±4.5, 76 patients) improved by 64% at 6 months (5.4±4.7, 75 patients). This improvement was also sustained at 1 year (5.4±5.3, 70 patients) and at 2 years (6.5±5.0, 67 patients). Paresthesiae and gait disturbances were the most common adverse effects at 1 year-each observed in 10 patients, with an additional 5 patients experiencing neurological adverse effects. None of the adverse events worsened over the period of follow up and 2 of these resolved. There were no new delayed complications at 2 years.

Conclusions: Improvement in tremor after MRgFUS thalamotomy for ET is stably maintained at 2 years. Latent or delayed complications do not develop after treatment.

Patient Care: MRgFUS is a new, non-invasive treatment modality that can provide alternatives for patients with essential tremor who do not desire surgical treatment.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the 2-year results of MRgFUS thalamotomy for ET and 2) Discuss the applicability of MRgFUS to the treatment of ET

References: (1)Elias, W. J., Lipsman, N., Ondo, W. G., Ghanouni, P., Kim, Y. G., Lee, W., et al. (2016). A Randomized Trial of Focused Ultrasound Thalamotomy for Essential Tremor. N Engl J Med, 375(8), 730-739. http://doi.org/10.1056/NEJMoa1600159