Effectiveness and safety of subthalamic nucleus deep brain stimulation in isolated generalised or segmental dystonia (SUNDYS trial): a study protocol.

Introduction: Dystonia, a rare neurologic disorder causing involuntary muscle contractions, significantly impacts quality of life. While deep brain stimulation (DBS) of the globus pallidal internus (GPi) is an established treatment, limitations have led to exploring the Subthalamic nucleus (STN) as an alternative. Previous studies suggest STN DBS is effective, but evidence is limited due to uncontrolled designs. The multicentre, randomised, double-blind, sham-controlled trial aims to determine the effectiveness and safety of STN DBS. The study will enrol 38 patients with isolated segmental or generalised dystonia. Following lead implantation, participants will be randomly assigned to active or sham STN DBS for 6 months. The primary outcome measures the proportion of patients with ≥30% improvement in movement score on the BFMDRS. Secondary outcomes include safety, tolerability, and impact on quality of life, mental, motor, and cognitive status at multiple intervals. Results will be analyzed using logistic regression and other statistical models. The study will follow the Helsinki Declaration and has received ethical approval from five centres. Findings will be disseminated through peer-reviewed journals and conferences.

Trial registration number: NCT04650958.