Subthalamic nucleus stimulation for Parkinson's disease: Current status and future prospects

Abstract

Recent clinical studies have demonstrated that deep brain stimulation (DBS) of the subthalamic nucleus (STN) can afford great benefits to the daily living activities of patients with advanced Parkinson's disease (PD). STN-DBS improves the daily living activity and total motor scores on the Unified Parkinson's Disease Rating Scale at off-medication, through improvement of the tremor, rigidity, akinesia, gait disturbance and postural instability subscores. STN-DBS also attenuates pronounced motor fluctuations due to on-off (wearing off) phenomenon at on-medication, through improved motor symptoms during the off-period and prolonged on-period. The dopa dose can be reduced and dopa-induced dyskinesia can be controlled by STN stimulation. The best indication for STN-DBS is currently considered to be dopa-responsive PD which demonstrates 1) marked motor fluctuations due to the on-off phenomenon, 2) dopa-induced dyskinesia or 3) levodopa-intolerance because of various other side effects. In contrast, STN-DBS may not improve the overall daily living activities at all in patients who have become unresponsive to a large-dose levodopa and continuously immobile. Continued use of large-dose levodopa has been suggested to cause various adverse reactions, including dyskinesia, the on-off phenomenon and mental symptoms. STN-DBS can be employed to decrease the cumulative levodopa dose taken by patients over the course of their illness. It appears possible therefore that early initiation of STN-DBS therapy could well alter the course of symptoms of PD. We consider that STN-DBS in less-advanced PD warrants further clinical investigation.