Deep brain stimulation improves gait velocity in Parkinson's disease: a systematic review and meta-analysis.

In Parkinson's disease (PD), slow gait speed is significantly related to clinical ratings of disease severity, impaired performance of daily activities, as well as increased overall disability. Conducting a meta-analysis on gait speed is an objective and quantitative technique to summarize the effectiveness of DBS and to determine the effect sizes for future studies. We conducted a systematic review and meta-analysis that analyzed the effects of deep brain stimulation (DBS) surgery on gait speed in patients with PD to gain fundamental insight into the nature of therapeutic effectiveness. A random effects model meta-analysis on 27 studies revealed a significant overall standardized mean difference medium effect size equal to 0.60 (SE = 0.06; p < 0.0001; Z = 10.58). Based on our synthesis of the 27 studies, we determined the following: (1) a significant and medium effect size indicating DBS improves gait speed; (2) DBS improved gait speed regardless of whether the patients were tested in the on or off medication state; (3) both bilateral and unilateral DBS led to gait speed improvement; (4) the effects of DBS on gait speed in the data collection sessions after surgery (DBS on vs. off) were comparable with data collection before surgery (before surgery vs. DBS after surgery); and (5) when evaluating the effects of DBS and medication on gait speed suprathreshold doses were comparable to normal dosages of medication and DBS. The current analysis provides objective evidence that both unilateral and bilateral DBS provide a therapeutic benefit on gait speed in persons with PD.