Dystonia before and after Unilateral High Intensity Focused Ultrasound Thalamotomy in Essential and Dystonic Tremor

BACKGROUND: Dystonia after focal thalamic lesions including from high-intensity focused ultrasound (HiFU) ablation have been reported. The risk remains uncertain and is increasingly relevant given the exponential rise in thalamic interventions for tremor over the last decade. OBJECTIVES: To evaluate the frequency and magnitude of dystonia before and after thalamic HiFU ablation in individuals with essential and dystonic tremor. METHOD: A blinded video-based analysis was performed using standardized dystonia and tremor rating scales at baseline and two follow-up intervals. Generalized linear mixed models assessed longitudinal change. RESULTS: Thirty individuals met the inclusion/exclusion criteria. Whole body and treated limb dystonia severity did not significantly change over time. One individual developed clinically significant dystonia after treatment yielding an estimated risk of approximately 1-2%. CONCLUSION: Dystonic features were identified in all individuals at baseline, including those diagnosed with essential tremor. Thalamic HiFU ablation was not associated with progression of dystonia severity during follow-up.