Background MRI-guided focused ultrasound (MRgFUS) thalamotomy is a promising non-invasive treatment option for medication-resistant essential tremor. However, it has been associated with variable efficacy and a relatively high incidence of adverse effects.
Objectives To assess the evolution of radiological findings after MRgFUS thalamotomy and to evaluate their significance for clinical outcomes.
Methods Ninety-four patients who underwent MRgFUS between 2012 and 2017 were retrospectively evaluated. Lesion characteristics were assessed on routine MRI sequences, as well as with tractography. Relationships between imaging appearance, extent of white matter tract lesioning (59/94, on a 4-point scale) and clinical outcome were investigated. Recurrence was defined as >33% loss of tremor suppression at 3 months relative to day 7.
Results Acute lesions demonstrated blood products, surrounding oedema and peripheral diffusion restriction. The extent of dentatorubrothalamic tract (DRTT) lesioning was significantly associated with clinical improvement at 1 year (t=4.32, p=0.001). Lesion size decreased over time (180.8±91.5 mm3 at day 1 vs 19.5±19.3 mm3 at 1-year post-treatment). Higher post-treatment oedema (t=3.59, p<0.001) was associated with larger lesions at 3 months. Patients with larger lesions at day 1 demonstrated reduced rates of tremor recurrence (t=2.67, p=0.019); however, lesions over 170 mm3 trended towards greater incidence of adverse effects (sensitivity=0.60, specificity=0.63). Lesion encroachment on the medial lemniscus (Sn=1.00, Sp=0.32) and pyramidal tract (Sn=1.00, Sp=0.12) were also associated with increased adverse effects incidence.
Conclusion Lesion size at day 1 predicts symptom recurrence, with fewer recurrences seen with larger lesions. Greater DRTT lesioning is associated with treatment efficacy. These findings may have implications for lesion targeting and extent.
Trial registration number NCT02252380.
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Contributors ANK: conception, organisation and execution of the project; design and review of the statistical analysis; and writing of the first draft and revisions. GJBE: organisation and execution of the project, design and review of the statistical analysis, and revision of the drafts. AB: conception, organisation and execution of the project; design and review of the statistical analysis, and revision of the drafts. JG: design, execution and review of the statistical analysis; and revision of drafts. AP, PC, JZ and CC: project execution and review of the manuscript. MLS, AF, RM, WK, MH and AML: project supervision, organisation and review of manuscript.
Funding This work was also supported by the RR Tasker Chair in Functional Neurosurgery at University Health Network and a Tier 1 Canada Research Chair in Neuroscience.
Competing interests AML is a consultant for Insightec and reports personal fees from Medtronic, St Jude, Boston Scientific and Functional Neuromodulation during the conduct of the study; grants from GJBE Healthcare, outside the submitted work. AF reports grants, personal fees and non-financial support from Abbvie; grants, personal fees and non-financial support from Medtronic; grants and personal fees from Boston Scientific; personal fees from Sunovion; personal fees from Chiesi Farmaceutici; personal fees from UCB; and grants and personal fees from Ipsen, outside the submitted work.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Data supporting this study are available upon reasonable request.
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