Objective: To determine clinical, surgical and radiological factors associated with tremor reduction after Gamma Knife thalamotomy (GKT) for essential tremor (ET).

Background: GKT is a second-line treatment for ET, and its success rate for significant tremor reduction is around 80%. So far, no factor has been identified to predict the efficacy of GKT.

Method: This retrospective observational cohort study included patients who underwent GKT for ET between February 2015 and January 2021 at Lille University Hospital. Baseline clinical data and pre-therapeutic resting-state functional MRI data were collected. The Essential Tremor Rating Assessment (TETRAS) Total score was calculated at baseline and 1 year after intervention. Biologically equivalent dose (BED) delivered during thalamotomy was estimated for each patient. Analyses of variance (ANOVA) were conducted to evaluate the impact of clinical data and BED values on TETRAS improvement. Correlations between the functional connectivity of structures implicated in the cerebello-thalamo-cortical circuit and TETRAS improvement were performed using multiple regression models.

Results: 20 patients were included in the study. Mean TETRAS improvement after intervention was 35% (F score = 29.39, p-value < 0.0001). Clinical data and BED were not associated with TETRAS improvement. However, weaker functional connectivity between cerebellar lobule III and the pre-central and post-central gyri was significantly associated with stronger TETRAS improvement (p-values = 0.013 and 0.010 respectively).

Conclusion: We identified functional connectivity changes in the the cerebello-thalamo-cortical circuit associated with a better clinical response to GKT. These results reinforce the hypothesis of the involvement of this circuit in the pathogenesis of ET.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/predicting-clinical-response-after-gamma-knife-thalamotomy-in-essential-tremor/