Objective: To assess tremorography as an objective tool for evaluating response to MR-guided focused ultrasound (MRgFUS) ventral intermediate nucleus (VIM) thalamotomy in essential tremor (ET) and Parkinson’s disease (PD), and to explore its correlation with the Clinical Rating Scale for Tremor (CRST) and Unified Parkinson’s Disease Rating Scale (UPDRS) Part III.

Background: Up to 50% of patients PD and ET become refractory to medications [1,2]. MRgFUS VIM thalamotomy is an effective option for drug-resistant tremor. Tremorography provides quantitative metrics and may serve as a sensitive biomarker of surgical response [3].

Method: The study include 12 patients with drug-resistant ET (median age 75.5 years) and 11 patients with PD (median age 65.4 years) undergoing unilateral MRgFUS VIM thalamotomy.Tremorography was performed preoperatively and repeated 2–5 days postoperatively. Two-channel accelerometry and four-channel surface electromyography (EMG) of bilateral forearm flexors and extensors were recorded at rest, in postural tasks (arms outstretched with pronated, supinated, and in wing position), with 500 g load, and with cognitive load. Paired pre–post comparisons of the peak power at the dominant tremor frequency, based on accelerometry and cross-referenced with EMG activity were performed using the Wilcoxon test (p<0.05). Spearman correlations assessed association between tremor power and clinical scores.

Results: In ET (n=12), median tremor power decreased by 95.3% in the pronated posture (p=0.0005), 98.8% with 500 g load (p=0.016), and 95.8% during cognitive load (p=0.016) [figure1]; peak frequency remained at 4–6 Hz. Baseline CRST Part B correlated with preoperative tremor power in the postural tasks (ρ=0.663, p=0.042 in pronated and ρ=0.669, p=0.040 in supinated posture). In PD (n=11), power decreased by 99.8% at rest (p=0.002), 99.4–99.9% in postural tasks (p=0.010–0.049), 99.2% with load (p=0.027), and 99.3% during cognitive load (p=0.004) [figure2]. Baseline UPDRS Part III correlated with power at rest (ρ=0.975, p=0.033).

Conclusion: Tremorography demonstrated tremor power reductions after MRgFUS VIM in both ET and PD. Correlations with CRST Part B and UPDRS Part III support the construct validity of tremorography as a quantitative measure of tremor severity. These pilot findings warrant confirmation in larger cohorts with standardized follow-up intervals.

Log₁₀-tremor power before/after MRgFUS in ET

Log₁₀-tremor power before/after MRgFUS in PD

References: 1. ​Su D, Cui Y, He C, et al. Projections for prevalence of Parkinson’s disease and its driving factors in 195 countries and territories to 2050: modelling study of Global Burden of Disease Study 2021. BMJ 2025;388:e080952. https://doi.org/10.1136/bmj-2024-080952
2. ​Louis ED, McCreary M. How Common is Essential Tremor? Update on the Worldwide Prevalence of Essential Tremor. Tremor and Other Hyperkinetic Movements 2021;11(1):28. https://doi.org/10.5334/tohm.632

3. ​Vial F, McGurrin P, Osterholt T, et al. Tremoroton, a new free online platform for tremor analysis. Clinical Neurophysiology Practice2020;5:30–34. https://doi.org/10.1016/j.cnp.2019.11.004

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MDS Abstracts - https://www.mdsabstracts.org/abstract/tremorography-as-an-objective-marker-of-the-response-after-mrgfus-vim-in-essential-tremor-and-parkinsons-disease/