Objective: To report on the outcomes between tremor subtypes, Essential Tremor (ET), Dystonic Tremor (DT) and Parkinson Disease Tremor (PDT), following a unilateral Magnetic Resonance Image guided Focused Ultrasound (MRgFUS) thalamotomy.

Background: Several centres have demonstrated sustained clinical benefit in the long-term following a unilateral MRgFUS thalamotomy in ET [1-3]. The literature in PDT patients is scant [4,5]. The treatment has also been extended to a few off-label indications in tremor, including DT. Though only a few published cases exist [6]. The current literature comparing outcomes between disease types is limited, and remains a possible predictive factor, among others, on the long-term outcomes.

Method: 66 patients underwent a unilateral MRgFUS thalamotomy for tremor between November 2018 and May 2020 at St Vincent’s Hospital Sydney. Each patient’s tremor syndrome was classified prior to treatment [7]. Pre-defined clinical assessments from baseline to 36 months; included Hand Tremor Score (HTS) and Quality of Life in Essential Tremor Questionnaire (QUEST).

Results: 63 patients return for at least one follow-up, including 30 ET, 24 DT and 9 PDT patients. The difference compared to baseline in HTS and QUEST persisted at all time-points in ET patients. At 24-months there was a 61% improvement in HTS (delta -13.0, 95% CI –15.8 to -10.3, p<0.001) and 50% improvement in QUEST (delta: -21.9, 95% CI –34.6 to –9.1, p<0.005). This is in comparison to PDT patients, where the 84% improvement in HTS (delta: -8.8, 95% CI -12.3 to -5.3, p<0.001) and 72% improvement in QUEST (delta: –31.4, 95% CI –52.4 to -10.4, p<0.005) seen at 1-month, waned at each follow-up, only remaining significant up until 12 and 6-months respectively. In the DT patients, as observed in the ET patients, the difference compared to baseline remained persistent through to 24-months. At this time point, DT patients had a 61% improvement in HTS (delta -12.2, 95% CI –15.6 to -8.9, p<0.001) and 43% improvement in QUEST (delta -22.4, 95% CI –40.3 to –4.4, p<0.05).

Conclusion: These results support the use of unilateral MRgFUS thalamotomy for the treatment of DT, who appear to have a similar expected outcomes to patients diagnosed with ET. Patients with PDT should be warned about the risks of treatment failure and the ongoing use of this procedure in these patients should occur under a research framework.

References: 1. Halpern CH, Santini V, Lipsman N, et al. Three-year follow-up of prospective trial of focused ultrasound thalamotomy for essential tremor. Neurology. 2019;93:e2284–e2293.
2. Lak AM, Segar DJ, McDannold N, White PJ, Cosgrove GR. Magnetic Resonance Image Guided Focused Ultrasound Thalamotomy. A Single Center Experience With 160 Procedures. Front Neurol. 2022;13:743649.
3. Miller WK, Becker KN, Caras AJ, et al. Magnetic resonance-guided focused ultrasound treatment for essential tremor shows sustained efficacy: a meta-analysis. Neurosurg Rev. 2022;45:533–544.
4. YAMAMOTO K, ITO H, FUKUTAKE S, et al. Focused Ultrasound Thalamotomy for Tremor-dominant Parkinson’s Disease: A Prospective 1-year Follow-up Study. Neurol Med Chir (Tokyo). 2021;61:414–421.
5. Bond AE, Shah BB, Huss DS, et al. Safety and Efficacy of Focused Ultrasound Thalamotomy for Patients With Medication-Refractory, Tremor-Dominant Parkinson Disease: A Randomized Clinical Trial. JAMA Neurology. 2017;74:1412–1418.
6. Fasano A, Llinas M, Munhoz RP, Hlasny E, Kucharczyk W, Lozano AM. MRI-guided focused ultrasound thalamotomy in non-ET tremor syndromes. Neurology. 2017;89:771–775.
7. Bhatia KP, Bain P, Bajaj N, et al. Consensus Statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society: IPMDS Task Force on Tremor Consensus Statement. Mov Disord. 2018;33:75–87.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/outcomes-of-focused-ultrasound-thalamotomy-in-tremor-syndromes/