Objective: We describe tremor outcomes, adverse effects, and impact to quality of life after staged bilateral MRI-Guided Focused Ultrasound (MRgFUS) Thalamotomy for Essential Tremor.

Background: Essential tremor (ET) can be extremely disabling, may not respond to conservative therapy, and is often bilateral. Unilateral MRgFUS thalamotomy is effective, leading to strong interest in bilateral treatment. Other than clinical trial data, there is little experience with outcomes following bilateral MRgFUS thalamotomy. [1] [2]

Method: We analyzed a cohort of ET patients who underwent staged bilateral MRgFUS from 2020 to 2024, with a minimum of three months of follow up. Sonication parameters were compared between first- and second-side treatments. Upper extremity tremor outcomes were assessed using the Clinical Rating Scale for Tremor Part B (CRST-B) normalized based on maximum score for dominant and non-dominant arms. Adverse effects were graded using the Common Terminology Criteria for Adverse Events (CTCAE). Quality of life changes were assessed using the Quality of Life in Essential Tremor (QUEST) instrument.

Results: Twenty-six patients underwent staged bilateral MRgFUS with a median treatment interval of 11.6 months, and median follow up of 11.9 months after bilateral treatment. Baseline demographics are described in Table 1 [table1]. Second-side treatment tended to be less aggressive than first-side treatments with lower sonication power, energy delivered, and lesion temperatures achieved overall [table2]. After second side treatment, contralateral tremor was significantly improved from baseline, but improvement was not as robust as that achieved after first side treatment [figure1]. Multiple adverse effects were observed including dysarthria, dysesthesia, gait disturbance, dysphagia, dysgeusia, and ataxia [figure2]. QUEST summary index scores improved significantly after bilateral treatment and were sustained at combined last follow up [figure3]. When asked “Given what you know now, would you treat the second side again,” 19 patients (76%) reported that they elect to repeat bilateral treatment in retrospect.

Conclusion: Staged bilateral MRgFUS thalamotomy can provide significant bilateral tremor control; however, rates of reported adverse effects, particularly dysarthria, appear higher than with unilateral treatment.

Table 1

Table 2

Figure 1

Figure 2

Figure 3

References: [1] Iorio-Morin C, Yamamoto K, Sarica C, et al. Bilateral Focused Ultrasound Thalamotomy for Essential Tremor (BEST-FUS Phase 2 Trial). Movement Disorders. 2021;36(11):2653-2662. doi:10.1002/mds.28716

[2] Kaplitt MG, Krishna V, Eisenberg HM, et al. Safety and Efficacy of Staged, Bilateral Focused Ultrasound Thalamotomy in Essential Tremor: An Open-Label Clinical Trial. JAMA Neurology. Published online July 29, 2024. doi:10.1001/jamaneurol.2024.2295

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MDS Abstracts - https://www.mdsabstracts.org/abstract/staged-bilateral-mri-guided-focused-ultrasound-thalamotomy-in-essential-tremor-a-single-institution-experience-of-26-patients/