Subthalamic nucleus deep brain stimulation for Parkinson's disease: 8 years of follow-up

Objective: The short-term benefits of bilateral stimulation of the subthalamic nucleus (STN) in patients with advanced Parkinson's disease (PD) are well documented, but long-term benefits are still uncertain. The aim of this study is to evaluate the outcome of 8 years of bilateral STN stimulation to PD patients. Methods: In this study, 31 consecutive PD patients were treated with bilateral STN stimulation. Their functional status was measured using the Activities of Daily Living section of the Unified Parkinson's Disease Rating Scale (UPDRS-ADL) at drug on (with medication) and drug off (without medication) states preoperatively and at 1, 5, and 8 years postoperatively. In addition, Levodopa equivalent doses and stimulation parameters were also assessed. Results: After 8 years of STN stimulation, the UPDRS-ADL scores were improved by 4% at drug off status (P > 0.05) and 22% at drug on status (P < 0.05) compared with baseline; the levodopa daily doses were reduced by 28% (P < 0.05) compared with baseline; the stimulation voltage and pulse width were not changed, but the stimulation frequency was decreased remarkably compared with the 5 years of follow-up. Adverse events were observed in 6 patients, including misplacement of the electrode and skin erosion requiring further surgery. All events were resolved without permanent sequelae. 2 patients died of aspiration pneumonia 6 and 7 years after surgery. Conclusions: The marked improvement in UPDRS-ADL scores were still observed after 8 years of bilateral STN stimulation with medication.