Objective: To identify the effect on somatosensory pathway and balance control after unilateral MRgFUS Vim thalamotomy in patients with essential tremor.

Background: Essential tremor (ET) is one of the most common movement disorders worldwide. The prevalence of ET is estimated to be 1 percent in overall and 5 percent in people with age more than 65, without significant gender difference [1,2]. Recently, magnetic resonance guided focused ultrasound (MRgFUS) become a novel treatment strategy which targeting the ventral intermediate nucleus (Vim) of thalamus [3]. Its high efficacy and less adverse events make it popular in the world today. However, damage on thalamus rising our concern in destruction of somatosensory pathway and balance control [4], which had already been established to be associated with thalamus pathway. Since MRgFUS thalamotomy had been widely performed today, the safety issue regarding its effect on somatosensory pathway and balance control is crucial and need to be studied.

Method: From June 2019 to December 2019, 8 patients with essential tremor eligible for MRgFUS thalamotomy were included. Pre-intervention evaluation with clinical rating score of tremor (CRST), somatosensory evoked potential (SSEP), and posturography were performed 1 day before treatment. After the intervention, CRST, SSEP and posturography were evaluated again at 3 months later. The changes in CRST score were used to evaluate the efficacy of treatment. The alteration in somatosensory conduction time via SSEP were used to define the effect on somatosensory pathway. The disability on posturography were used to identify the effect on balance control.

Results: In 8 patients receiving MRgFUS thalamotomy, CRST score improved immediately after the intervention from 40-70%, respectively. 6 of 8 patients completed the post-intervention survey after 3 months later (table 1, 2). Tremor reduction persisted in all these 6 patients without significant recurrence. SSEP did not show significant central conduction time prolong and posturography did not show significant deterioration in overall stability index, as compare to the pre-intervention test. There was also no self-report of paresthesia or imbalance by all participants and their families.

Conclusion: Unilateral MRgFUS Vim thalamotomy is effective in tremor reduction with minimal effect on somatosensory pathway and balance control.

References: 1. Louis ED, Broussolle E, Goetz CG, Krack P, Kaufmann P, Mazzoni P. Historical underpinnings of the term essential tremor in the late 19th century. Neurology 2008;71:856-9. doi:10.1212/01.wnl. 0000325564.38165.d1 2. Louis ED, Ferreira JJ. How common is the most common adult movement disorder? Update on the worldwide prevalence of essential tremor. Mov Disord 2010;25:534-41. doi:10.1002/mds.22838 3. Elias, W.J.; Lipsman, N.; Ondo, W.G.; Ghanouni, P.; Kim, Y.G.; Lee, W.; Schwartz, M.; Hynynen, K.; Lozano, A.M.; Shah, B.B.; et al. A Randomized Trial of Focused Ultrasound Thalamotomy for Essential Tremor. N. Engl. J. Med. 2016, 375, 730–739. 4. Mohammed, N.; Patra, D.; Nanda, A. Erratum. A meta-analysis of outcomes and complications of magnetic resonance–guided focused ultrasound in the treatment of essential tremor. Neurosurgical Focus 2018, 45, E16.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effect-on-somatosensory-pathway-and-balance-control-after-unilateral-mrgfus-vim-thalamotomy-in-patients-with-essential-tremor/