To evaluate the efficacy and safety of staged, bilateral MR-guided focused ultrasound (MRgFUS) thalamotomy in medication-refractory essential tremor (ET) and report on the second-side treatment landscape since FDA approval.

Staged, bilateral MRgFUS was FDA-approved in 2022 for ET, broadening its clinical utility. MRgFUS is an incisionless technique that enables precise targeting and is the leading advanced therapy for ET, prompting renewed interest in its bilateral application. By addressing the complete clinical presentation of bilateral disorders, like ET, MRgFUS may help bridge existing therapeutic gaps.

In a prospective, open-label, single-arm, seven-center study, 51 subjects underwent staged, bilateral MRgFUS thalamotomy at least 9 months after unilateral treatment. The primary endpoint was change in tremor/motor score (CRST parts A+B) at 3 months; secondary outcomes included tremor severity, functional disability, and safety through 1 year. Utilization data review of unilateral and second-side MRgFUS treatments.

Mean tremor/motor scores improved by 66% reduction (P<0.001, 17.4 at baseline to 6.4 at 3 months), with sustained improvement to at least 12 months. Tremor severity and functional disability improved from 2.5 to 0.6 (81% reduction; P<0.001) and from 10.3 to 2.2 (73% reduction; P<0.001), respectively. Of 188 total related adverse events (AEs), 85% were mild, 13% moderate, and 1 was a severe urinary tract infection. The most common AEs included numbness/tingling, dysarthria, and ataxia. As clinical experience grows and outcomes remain favorable, utilization of both unilateral and staged, bilateral MRgFUS treatments increased 30% and 69%, respectively, from 2023 to 2024, reflecting a need and patient preference.

Staged, bilateral MRgFUS thalamotomy provides significant and durable tremor improvement with an acceptable safety profile. Growing clinical adoption of both unilateral and bilateral treatments underscores the potential of MRgFUS as a viable, incisionless, and effective treatment option capable of addressing the inherently bilateral nature of essential tremor.