Objective: To assess the long-term efficacy and safety of Vim-FUS in ET patients treated at our centre.

Background: Vim-FUS has emerged as an effective therapeutic alternative for medication-refractory ET, yet long-term data from large cohorts remain limited.

Method: Prospective longitudinal study including ET patients undergoing unilateral Vim-FUS between 2018 and 2024, with a minimum follow-up of 12 months. Efficacy was assessed using the Clinical Rating Scale for Tremor (CRST) at predefined time points (baseline; 1, 3, 6, 12, 24, 36, 48, and 60 months). The efficacy of tremor improvement was assessed using parts A and B of the CRST on the treated side. Axial tremor was assessed as the sum of facial, lingual, voice, and head ítems of CRST A. CRST part C was used to assess the impact of functional disability due to tremor. Longitudinal changes were analysed using a linear mixed-effects model. Adverse events were recorded and classified according to severity.

Results: Among 229 ET patients undergoing Vim-FUS at our centre, 89 had >12 months of post-treatment follow-up (mean age 70.0±10.9 years, disease evolution 25.8±17.1 years), with 86 had a 1-month evaluation, 74 at 3 months, 79 at 6 months, 54 at 12 months, 24 at 24 months, 12 at 36 months, 11 at 48 months, and 13 at 60 months.

At each evaluation time point, the CRST A+B, CRST A, and CRST B scores showed significant improvement on the treated side when compared with baseline (p<0.0001). The sum of axial tremor items improved by 41.5% at 12 months (from 1.9 [1.5-2.4] to 1.1 [0.6-1.7], p<0.001), and by 48.2% at 24 months (p=0.014), losing statistical significant differences from the 36-month visit onwards (from 1.9 [1.5-2.4] to 1.3 [0.5–2.1], p=0.34 at 60 months). CRST C showed a significant improvement at all visits compared with baseline (p<0.001 for all visits; from 16.8 [15.7–17.9] to 5.4 [3.1–7.8] at 60 months).

At 12 months, a total of 24 adverse events, all mild, were registered in 33% of patients (6 disarthria, 1 dismetria, 6 imbalance, 9 sensory disturbances, 2 dysgeusia). Among the 13 patients available for the 60-month visit, 4 patients presented adverse events, stable in severity during follow-up: 1 moderate ataxia and the remaining mild (3 disarthria, 2 limb paresis, 1 sensory disturbances, 1 imbalance).

Conclusion: Our findings confirm that Vim-FUS provides a sustained tremor improvement for up to 5 years in ET patients with a reasonable risk-benefit balance.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/long-term-5-year-follow-up-of-unilateral-fus-thalamotomy-for-essential-tremor/