Background: Deep-brain stimulation is the surgical procedure of choice for patients with advanced Parkinson's disease. The globus pallidus interna and the subthalamic nucleus are accepted targets for this procedure. We compared 24-month outcomes for patients who had undergone bilateral stimulation of the globus pallidus interna (pallidal stimulation) or subthalamic nucleus (subthalamic stimulation). Methods: At seven Veterans Affairs and six university hospitals, we randomly assigned 299 patients with idiopathic Parkinson's disease to undergo either pallidal stimulation (152 patients) or subthalamic stimulation (147 patients). The primary outcome was the change in motor function, as blindly assessed on the Unified Parkinson's Disease Rating Scale, part III (UPDRS-III), while patients were receiving stimulation but not receiving antiparkinsonian medication. Secondary outcomes included selfreported function, quality of life, neurocognitive function, and adverse events. Results: Mean changes in the primary outcome did not differ significantly between the two study groups (P = 0.50). There was also no significant difference in self-reported function. Patients undergoing subthalamic stimulation required a lower dose of dopaminergic agents than did those undergoing pallidal stimulation (P = 0.02). One component of processing speed (visuomotor) declined more after subthalamic stimulation than after pallidal stimulation (P = 0.03). The level of depression worsened after subthalamic stimulation and improved after pallidal stimulation (P = 0.02). Serious adverse events occurred in 51% of patients undergoing pallidal stimulation and in 56% of those undergoing subthalamic stimulation, with no significant between-group differences at 24 months. Conclusions: Patients with Parkinson's disease had similar improvement in motor function after either pallidal or subthalamic stimulation. Nonmotor factors may reasonably be included in the selection of surgical target for deep-brain stimulation.
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