Bilateral subthalamic nucleus stimulation in advanced Parkinson's disease

Objective. To assess the long-term efficacy and safety of chronic bilateral stimulation of the subthalamic nucleus (STN) in patients with advanced Parkinson's disease (PD). Methods. 36 consecutive patients with idiopathic Parkinson's disease treated with bilateral stimulation of the STN were studied. Parkinsonian status was assessed preoperatively and at 1 and 3 years postoperatively using the Unified Parkinson's Disease Rating Scale (UPDRS) and neuropsychological evaluation in on and off-medication / on and off stimulation conditions. Results. At 3 years follow-up, STN stimulation reduced the UPDRS motor score by 54.2 % compared to baseline in the off-medication conditions. Tremor, rigidity, bradykinesia, postural stability, and gait improved by 72.2 %, 62.4 %, 56.8 %, 40.5 % and 45.3 %, respectively. UPDRS part II scores were reduced by 41.4 %. The overall dopaminergic drugs dose was reduced by 48.6 % after surgery and four patients were no longer taking antiparkinsonian medication at three years. However, axial dopa-unresponsive signs worsened in some patients. The most frequent transient adverse event consisted in mood disorders in 23 patients. Conclusions. Our data demonstrate that: 1) bilateral STN stimulation is relatively safe, improves the motor symptoms and drug-related motor complications of PD, and reduces the daily dosage of medication; 2) this benefit is sustained over time despite the occurrence of axial doparesistant signs in some patients.