Deep brain stimulation (DBS) targeting the subthalamic nucleus (STN) or the globus pallidus pars interior (GPi) represents one of the major therapeutic breakthroughs in the treatment of Parkinson's disease (PD). Despite the complexity of the procedure, the need to integrate a team of neurologists, neurosurgeons, neurophysiologists, and research nurses, and its high cost, DBS is now routinely used at PD centers around the world and it has benefited several thousands of patients. DBS of both the STN and the GPi has been shown to be effective for the treatment of levodopainduced motor complications 1 and is superior to best medical management. 2,3 These benefits have been confirmed in randomized, controlled, double-blind trials. 3,4 For patients who suffer intolerable motor complications, the introduction of DBS has represented a ''therapeutic miracle.'' However, serious side effects may be associated with the procedure, the indwelling DBS system, and the stimulation itself. In addition to the risk of a devastating intracerebral hemorrhage (about 1%), hardware problems due to fracture, infection, or lead displacement can necessitate removal of the electrodes in as many as 2% of patients. 5 Further, the clinical effects of DBS in PD patients are comparable to what can be achieved with continuous infusion of L-dopa and apomorphine. 6 Indeed, no study has demonstrated that DBS provides anti-parkinsonian benefits that are superior to what can be achieved with L-dopa. On the other hand, DBS provides continuous 24-hour benefit, with maintenance of efficacy during the night, no evidence of tolerance, and a reduction in side effects associated with the use of high-dose dopaminergic medications.
Medical therapy for PD is limited by disease progression and the development of features such as falling, freezing, and dementia. Accordingly, long-term follow-up studies of DBS procedures, to evaluate the quality and duration of benefits and the propensity to develop cumulative disability, are crucial to fully appreciate the risk or benefit of the procedure, and to appropriately counsel patients and their families.