Globus pallidus stimulation in advanced Parkinson's disease

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) has become an accepted therapeutic modality in selected Parkinson's disease (PD) patients with severe levodopa-induced dyskinesias (LID) and on-off motor fluctuations. In comparison to subthalamic nucleus DBS there is a paucity of data on GPi DBS outcomes. We present our experience with a group of 20 PD patients (9 unilateral, 11 bilateral) who underwent GPi stimulation. PD motor symptoms were assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) part III scores and subscores, and dyskinesia using the Abnormal Involuntary Movement Scale (AIMS), UPDRS part IVa, and clinical global impression (CGI). At mean follow-up time of 7 months, bilateral stimulation reduced off-period motor scores by a mean of 46% and on-period motor scores by 18%. Unilateral stimulation reduced off-period motor scores by 18%. Dyskinesia severity was reduced by 76%, which was maintained after a mean follow-up time of 35 months. Antiparkinsonian medication dosage was unchanged. No major adverse effects were seen. Unilateral and bilateral GPi DBS provides lasting benefit in PD patients with severe LID. Beneficial effects on off-period motor symptoms are greater with bilateral stimulation; however, with maintenance of dopaminergic medication, unilateral procedures can also provide important and sustained benefits.