Motor and Non-Motor Effects of Low-Intensity Focused Ultrasound (LIFU) as a Neuromodulation Tool in Essential Tremor

This study investigates the motor and non-motor effects of Low-Intensity Focused Ultrasound (LIFU) as a non-invasive neuromodulation technique in patients with essential tremor (ET) and refractory tremor. LIFU is a non-thermal, non-ablative form of transcranial focused ultrasound that modulates neural activity through mechanical mechanisms, including direct effects on neuronal membranes, alterations in membrane excitability, and modulation of synaptic transmission. Unlike high-intensity focused ultrasound (HIFU), which produces tissue ablation, LIFU induces reversible effects with a favorable safety profile, making it a promising candidate for non-invasive neuromodulation in movement disorders. In this randomized, double-blind, sham-controlled, crossover trial, 20 patients with ET and refractory tremor will receive active LIFU targeting the ventral intermediate nucleus (VIM) of the thalamus and sham stimulation in separate sessions, separated by a washout period of at least 12 weeks. Clinical assessments using standardized and validated neurological scales will be performed before and after each session to evaluate changes in motor symptoms, tremor severity, quality of life, and non-motor features. The primary outcome is the change in the Fahn-Tolosa-Marín Tremor Rating Scale (FTMTRS) and the Essential Tremor Rating Assessment Scale (TETRAS©). Secondary outcomes include the Patient Global Impression of Change (PGIC) and monitoring of adverse events. This study is being conducted at the Movement Disorders Center of Hospital das Clínicas, University of São Paulo (HC-FMUSP), São Paulo, Brazil, and has been approved by the institutional ethics committee (CAPPesq; approval number 7.406.027).