• Kazuaki Yamamoto, Can Sarica, Gavin J B Elias, Alexandre Boutet, Jurgen Germann, Aaron Loh, Suresh E Joel, Luca Bigioni, Dave Gwun, Robert Gramer, Stanley Xiangyu Li, Ajmal Zemmar, Artur Vetkas, Musleh Algarni, Gabriel Devenyi, Mallar Chakravarty, Kullervo Hynynen, Nadia Scantlebury, Michael L Schwartz, Andres M Lozano, and Alfonso Fasano.
• Division of Neurosurgery, Toronto Western Hospital, Toronto, Ontario, Canada.
• J. Neurol. Neurosurg. Psychiatr. 2022 Aug 22.

BackgroundMR-guided focused ultrasound (MRgFUS) thalamotomy has been shown to be a safe and effective treatment for essential tremor (ET).ObjectiveTo investigate the effects of MRgFUS in patients with ET with an emphasis on ipsilateral-hand and axial tremor subscores.MethodsTremor scores and adverse effects of 100 patients treated between 2012 and 2018 were assessed at 1 week, 3, 12, and 24 months. A subgroup analysis of ipsilateral-hand tremor responders (defined as patients with ≥30% improvement at any time point) and non-responders was performed. Correlations and predictive factors for improvement were analysed. Weighted probabilistic maps of improvement were generated.ResultsSignificant improvement in axial, contralateral-hand and total tremor scores was observed at all study visits from baseline (p<0.0001). There was no significant improvement in ipsilateral subscores. A subset of patients (n=20) exhibited group-level ipsilateral-hand improvement that remained significant through all follow-ups (p<0.001). Multivariate regression analysis revealed that higher baseline scores predict better improvement in ipsilateral-hand and axial tremor. Probabilistic maps demonstrated that the lesion hotspot for axial improvement was situated more medially than that for contralateral improvement.ConclusionMRgFUS significantly improved axial, contralateral-hand and total tremor scores. In a subset of patients, a consistent group-level treatment effect was observed for ipsilateral-hand tremor. While ipsilateral improvement seemed to be less directly related to lesion location, a spatial relationship between lesion location and axial and contralateral improvement was observed that proved consistent with the somatotopic organisation of the ventral intermediate nucleus.Trial Registration NumbersNCT01932463, NCT01827904, and NCT02252380.© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.

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