Impact of deep brain stimulation on gait in Parkinson disease: A kinematic study

Background: The effect of Deep Brain Stimulation (DBS) on gait in Parkinson's Disease (PD) is poorly understood. Kinematic studies utilizing quantitative gait outcomes such as speed, cadence, and stride length have shown mixed results and were done mostly before and after acute DBS discontinuation.Objective: To examine longitudinal changes in kinematic gait outcomes before and after DBS surgery.Method: We retrospectively assessed changes in quantitative gait outcomes via motion capture in 22 PD patients before and after subthalamic (STN) or globus pallidus internus (GPi) DBS, in on medication state. Associations between gait outcomes and clinical variables were also assessed.Result: Gait speed reduced from 110.7 +/- 21.3 cm/s before surgery to 93.6 +/- 24.9 after surgery (7.7 +/- 2.9 months post-surgery, duration between assessments was 15.0 +/- 3.8 months). Cadence, step length, stride length, and single support time reduced, while total support time, and initial double support time increased. Despite this, there was overall improvement in the Movement Disorder Society-Unified Parkinson Disease Rating Scale-Part III score "on medication/on stimulation" score (from 19.8 +/- 10.7-13.9 +/- 8.6). Change of gait speed was not related to changes in levodopa dosage, disease duration, unilateral vs bilateral stimulation, or target nucleus.Conclusion: Quantitative gait outcomes in on medication state worsened after chronic DBS therapy despite improvement in other clinical outcomes. Whether these changes reflect the effects of DBS as opposed to ongoing disease progression is unknown.