Objective: To perform a literature overview of the clinical effectiveness and safety of staged-bilateral MR-guided focused ultrasound (MRgFUS)  in essential tremor.

Background: In the brain, MRgFUS offers incisionless energy delivery with real-time imaging, temperature feedback[1] and clinical testing before definitive treatment[2]. The uptake and evidence around MRgFUS has been growing since its introduction[3]. Recently, staged-bilateral treatment received FDA and CE approval[4,5]. Systematic literature reviews (SLR) for this approach have not been performed.

Method: In accordance with the PRISMA guidelines[6,7], a SLR search was performed to identify relevant primary studies on the clinical effectiveness and safety of staged-bilateral MRgFUS. The inclusion and exclusion criteria applied for the SLR are presented in Table 1. Searches were performed in Medline and Medline In-Process.

Results: The SLR yielded inclusion of 4 studies(n=35) as provided in Table 2 with the PRISMA diagram in Fig 1. When available, studies demonstrated statistically significant reductions in Total CRST, Part C and QUEST. From pre-MRgFUS1 to post-MRgFUS2, reported Total CRST and CRST Part C improvement ranged from 66% to 71% and from 81% to 85%, respectively. Among studies reporting on QUEST; one showed a mean improvement of 19.7; 95% CI, 8.0–31.4 (3), while another reported improvement on all QUEST domains; Finance (P=0.043), hobbies/leisure (P=0.007), physical (P = 0.001) and psychosocial (P = 0.002). No severe adverse events were reported. Mild adverse event due to staged-bilateral MRgFUS were reported in all the studies, it mainly included gait impairment, sensory disturbances and dysgeusia. Most were transient. In one study, the SARA’s gait LS-mean scores worsened by a small magnitude (P = 0.03), while stance LS-mean scores were stable (P = 0.39). In one study, all treated subjects (n=10) determined that the benefits of the procedure outweighed the downsides and would elect to undergo the treatment again. Another reported a mean level of satisfaction of 74 on a 100 VAS. Satisfaction level was set at ≥60.

Conclusion: Four studies published across the globe demonstrated the safety and efficacy of staged-bilateral MRgFUS. The approval yields an opportunity to further investigate the added value of treating the second side, comparison with best medical treatment should be granted.

Table 1

Table 2

Figure 1

References: [1] Meng, Y. et al. Technical Principles and Clinical Workflow of Transcranial MR-Guided Focused Ultrasound. Stereot Funct Neuros 99, 329–342 (2021).
[2] Sammartino, F., Snell, J., Eames, M. & Krishna, V. Thermal Neuromodulation With Focused Ultrasound: Implications for the Technique of Subthreshold Testing. Neurosurgery 89, 610–616 (2021).
[3] Iorio-Morin, C., Hodaie, M. & Lozano, A. M. Iorio-Morin,Lozano. 2021. [J Neurol Neurosurg Psychiaty]. Adoption of FUS thalamotomy for ET_why so much fuss about FUS.pdf. J Neurology Neurosurg Psychiatry 92, 549–554 (2021).
[4] ExAblate® Model 4000 Type 1. Information for Prescribers. https://www.accessdata.fda.gov/cdrh_docs/pdf15/p150038c.pdf
[5] Data on file at Insightec.
[6] Shekelle PG, Maglione MA, Luoto J, et al. Global Health Evidence Evaluation Framework [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2013 Jan. Table B.9, NHMRC Evidence Hierarchy: designations of ‘levels of evidence’ according to type of research question (including explanatory notes) Available from: https://www.ncbi.nlm.nih.gov/books/NBK121300/table/appb.t21/
[7] Moher D, Liberati A, Tetzlaff J, Altman DG; PRISMA Group. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Med. 2009 Jul 21;6(7):e1000097.

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