Long-term results of bilateral pallidal stimulation in Parkinson's disease.

We followed up 11 patients for up to 5 years after bilateral pallidal deep brain stimulation for advanced Parkinson's disease. Dyskinesias remained significantly reduced until the last assessment. The initial improvement of off-period motor symptoms and fluctuations, however, was not sustained and gradually declined. Beneficial effects of pallidal deep brain stimulation on activities of daily living in the on- and off-period were lost after the first year. Replacement of pallidal electrodes into the subthalamic nucleus in four patients could restore the initial benefit of deep brain stimulation and allowed a significant reduction of dopaminergic drug therapy.