STN vs. GPi deep brain stimulation for tremor suppression in Parkinson disease: A systematic review and meta-analysis

Objective: To compare subthalamic nucleus (STN) deep brain stimulation (DBS) with globus pallidus interna (GPi) DBS for tremor suppression in Parkinson disease (PD). Background: DBS is an effective surgical therapy that has been shown to provide significant benefit for motor symptoms in PD. Currently, two main structures targeted to treat motor complications in PD are the STN and GPi. Although some groups traditionally favor STN over GPi for tremor suppression, evidence demonstrating superiority in long-term tremor control is limited. Methods: We performed a systematic review for all randomized trials comparing STN vs GPi DBS in PD that were published before March 2017. Five studies were examined in a random effects model meta-analysis. We conducted moderator variable analysis to determine if there was a treatment effect difference for STN versus GPi. Results: We compared DBS ON versus OFF and found a significant overall standardized difference mean effect: Effect Size = 0.36; 95% CI = 0.316–0.395; P < 0.0001. These findings indicate that DBS reduced tremor symptoms in PD patients with a medium effect size. Moderator variable analysis of STN vs GPI revealed two significant standardized effect sizes: STN effect size = 0.38 and GPi effect size = 0.35. A Z-test showed that effect sizes between the STN and GPi were not significantly different (P = 0.56). Conclusions: DBS is effective in reducing tremor in PD patients regardless of stimulation target. However, the degree of tremor suppression in STN DBS versus GPi DBS was equivalent.