Fifteen‐Year Outcomes of Bilateral Pallidal Stimulation in Isolated Generalized Dystonia: Characterization of Therapeutic Response and Emergence of Parkinsonism

Background Bilateral pallidal deep brain stimulation ( GPi ‐ DBS ) is effective for dystonia. Long‐term evolution of therapeutic benefit and emergence of parkinsonism have not been systematically characterized. Objectives To assess 15‐year dystonia outcomes and characterize parkinsonism after bilateral GPi ‐ DBS . Methods Dystonia severity and disability were evaluated at baseline,1, 3, and 15 years postoperatively with the Burke–Fahn–Marsden Dystonia Rating Scale (BFMDRS). Parkinsonism was assessed at last visit using the Movement Disorder Society‐Unified Parkinson's Disease Rating Scale‐Part III and freezing of gait (FoG) questionnaire. Results Of 17 patients reassessed at 15 years, 41% maintained clinical benefit. Parkinsonism was observed in 94%, predominantly axial, with self‐reported FoG in 67%. Higher baseline BFMDRS‐Motor scores predicted last follow‐up axial parkinsonism ( R = 0.800, P < 0.001). Conclusions Over 15 years, interindividual therapeutic benefit diverged while axial parkinsonism emerged in nearly all patients. These findings highlight the need for systematic long‐term monitoring extending beyond dystonia control after GPi‐DBS.