Stimulation of the subthalamic nucleus compared with the globus pallidus internus in patients with Parkinson disease

Abstract

Object. The authors compared the effects of deep brain stimulation (DBS) in the globus pallidus internus (GPi) with those in the subthalamic nucleus (STN) in patients with Parkinson disease (PD) in whom electrodes had been bilaterally implanted in both targets. Methods. Eight of 14 patients with advanced PD in whom electrodes had been implanted bilaterally in both the GPi and STN for DBS were selected on the basis of optimal DBS effects and were studied 2 months postsurgery in offand on-stimulus conditions and after at least 1 month of pharmacological withdrawal. Subcutaneous administration of an apomorphine test dose (0.04 mg/kg) was also performed in both conditions. Compared with the off status, the results showed less reduction in the Unified PD Rating Scale Section III scores during DBS in the GPi (43.1%) than during DBS of the STN (54.5%) or DBS of both the STN and GPi (57.1%). The difference between the effects of DBS in the GPi compared with that in the STN or simultaneous DBS was statistically significant (p < 0.01). In contrast, no statistical difference was found between DBS in the STN and simultaneous DBS in the STN and GPi (p < 0.9). The improvement induced by adding apomorphine administration to DBS was similar in all three stimulus modalities. The abnormal involuntary movements (AIMs) induced by apomorphine were almost abolished by DBS of the GPi, but were not affected by stimulation of the STN. The simultaneous stimulation of STN and GPi produced both antiparkinsonian and anti-AIM effects. Conclusions. The improvement of parkinsonian symptoms during stimulation of the GPi, STN, and both nuclei simultaneously may indicate a similar DBS mechanism for both nuclei in inducing antiparkinsonian effects, although STN is more effective. The antidyskinetic effects produced only by DBS of the GPi, with or without STN, may indicate different mechanisms for the antidyskinetic and antiparkinsonian activity related to DBS of the GPi or an additional mechanism in the GPi. These findings indicate that implantation of double electrodes for DBS should not be proposed as a routine procedure, but could be considered as a possible subsequent choice if electrode implantation for DBS of the STN does not control AIMs.