Essential Tremor (ET)

Deep brain stimulation (DBS) of the thalamus is an effective treatment for medically refractory essential tremor (ET). DBS involves delivering continuous stimulation to the brain through electrodes permanently implanted in the thalamus. Despite proven effectiveness, the long-term benefit of DBS can wane over time (habituation) and side effects, including paresthesia and dysarthria, often limit the amplitude of the stimulation, resulting in suboptimal control of tremor. In clinical practice, many groups advise patients to switch their devices off at night to avoid habituation and reduce side effects. However, manually turning off the device at night can result in uncontrolled tremor when the patient moves at night. This study aims to develop an algorithm that automatically turns off stimulation when a patient is asleep, based on circadian brain signals. Turning off stimulation could potentially improve the therapy by limiting adverse effects, increasing efficacy, reducing the risk of habituation, and prolonging battery life. This study will evaluate the feasibility, safety, and tolerability of circadian adaptive DBS.

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).