Does Subthalamic Deep Brain Stimulation Impact Asymmetry and Dyscoordination of Gait in Parkinson’s Disease?

Background Subthalamic deep brain stimulation is an effective treatment for selected Parkinson’s disease patients. Axial deficits including postural stability and gait characteristics are often altered after surgery, but quantitative gait-related therapeutic effects are poorly described. Objective The goal of this study was to systematically investigate modifications in asymmetry and dyscoordination of gait six-months post-operatively in patients with Parkinson’s disease, and compare the outcomes with preoperative baseline and to asymptomatic controls. Methods Thirty-two patients with Parkinson’s disease (19 with postural instability and gait disorder type, 13 with tremor-dominant disease) and 51 asymptomatic controls participated. Parkinson patients were tested prior to the surgery in both OFF and ON medication states, and six months post-operatively in the ON stimulation condition. Clinical outcome parameters and medication were compared to preoperative conditions. Asymmetry ratios, phase coordination index, and walking speed were assessed. Results Patients’ clinical outcomes as assessed by standard clinical parameters at six-months improved significantly, and levodopa-equivalent daily dosages were significantly decreased. STN-DBS increased step time asymmetry (hedges’ g effect sizes [confidence intervals] between pre- and post-surgery: 0.27 [-0.13,0.73]) and phase coordination index (0.29 [-0.08,0.67]). These effects were higher in the Postural Instability and Gait Disorder subgroup than the Tremor Dominant (step time asymmetry: 0.38 [-0.06,0.90] vs. 0.09 [-0.83,1.0] and phase coordination index: 0.39 [-0.04,0.84] vs. 0.13 [-0.76,0.96]). Conclusion This study provides objective evidence of how subthalamic deep brain stimulation increases asymmetry and dyscoordination of gait in patients with Parkinson’s disease, and suggests motor subtypes-associated differences in the treatment response.