Long-term outcomes of bilateral subthalamic nucleus stimulation in patients with advanced Parkinson's disease

Background: In patients with advanced Parkinson's disease (PD), deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been shown to improve motor function and decrease medication requirements in the short term. However, the long-term benefits of DBS are not yet established. Objective: It was the aim of this study to evaluate long-term outcomes of patients with PD treated with bilateral DBS of the STN. Design and Methods: Thirty-three subjects who had bilateral STN DBS were followed prospectively after surgery. We evaluated subjects, using the Unified Parkinson's Disease Rating Scale (UPDRS), preoperatively, 12 months after surgery and at a long-term follow-up visit. Ratings were performed on and off dopaminergic medications. We compared postoperative UPDRS scores, dyskinesia ratings and medication dosages with preoperative values. Results: Twenty-seven subjects had evaluations beyond 18 months (median 33.7 months). Total UPDRS scores in the 'medication-off' state were improved by 37% (p < 0.001) at 12 months and 17.7% (p = 0.0051) at the long-term evaluation. Medication-off state UPDRS part III scores were significantly improved at both 1 year and at the last evaluation (37.6 and 29.3%; p < 0.001). Dopaminergic medication requirements were decreased by 35.3% (p < 0.001) during the first postoperative year and remained below preoperative levels at the long-term evaluation. Average duration of 'off' time remained decreased by about 40% at both 1 year and at the time of last evaluation. Subjects had a sustained reduction in dyskinesia severity (88.6% at 1 year and 68.8% at last evaluation). Conclusions: In this cohort of subjects with advanced PD, bilateral STN stimulation improved 'off' medication motor function, reduced time spent in the medication-off state and reduced medication requirements for up to 4 years after surgery. We conclude that STN DBS is an effective long-term therapy for selected patients with advanced PD.