Effect of high‐frequency subthalamic neurostimulation on gait and freezing of gait in Parkinson's disease: a systematic review and meta‐analysis

The aim of this meta‐analysis was to summarize the short‐ and long‐term effects of bilateral deep brain stimulation of the subthalamic nucleus ( STN ‐ DBS ) on gait and freezing of gait ( FOG ) in Parkinson's disease and to detect predictors of post‐stimulation outcome. A comprehensive review of the literature was conducted up to October 2015 using Medline Ovid databases for studies analyzing the effect of bilateral STN ‐ DBS on FOG and/or gait. Sixteen studies with available data for the gait item (no. 29) of the Unified Parkinson's Disease Rating Scale ( UPDRS ) and six studies with the FOG item (no. 14) were included. Data were summarized for the following follow‐up periods: 6–15, 24–48 and >48 months. For the medication (Med)‐Off/stimulation(Stim)‐On condition compared with baseline Med‐Off, STN ‐ DBS significantly improved gait on average from 2.43 to 0.96, 2.53 to 1.31 and 2.56 to 1.40 points at 6–15, 24–48 and >48 months, respectively ( P < 0.05). Pre‐operative levodopa responsiveness of UPDRS ‐ III and Med‐Off severity of gait were the predictors of this beneficial effect. STN‐DBS significantly improved FOG for the Med‐Off/Stim‐On condition compared with baseline on average from 2.26 to 0.82, 2.43 to 1.13 and 2.48 to 1.38 points at 6–15, 24–48 and >48 months, respectively ( P < 0.05). There was no significant effect in the Med‐On/Stim‐On condition. This meta‐analysis showed a robust improvement of gait and FOG by STN ‐ DBS for more than 4 years in the Med‐Off/Stim‐On condition. No beneficial effect was found for the On state of medication. Pre‐operative levodopa responsiveness of global motor performance ( UPDRS ‐ III ) is the strongest predictor of the effect of deep brain stimulation on gait.