Bilateral Deep Brain Stimulation of the Subthalamic Nucleus or Globus Pallidus Internus Improves Gait Impairment in Parkinson's Disease
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Background and objectives: The effect of deep brain stimulation (DBS) on gait in patients with Parkinson's disease (PD) is variable but prospective, long-term studies-especially including globus pallidus interna (GPi) stimulation-remain sparse. We tested the hypothesis that subthalamic nucleus (STN) and GPi DBS exert acute and chronic effects on gait in patients with PD. Methods: Gait kinematics were collected prospectively on patients with PD with bilateral or unilateral STN or GPi DBS, at baseline before initial DBS activation (n=104), acutely after activation (n=102), and chronically at 1-month (n=75) and 12-months (n=82). Gait speed was the main outcome measure. Kinematic measures of pace, rhythm, and variability and clinical scales were secondary outcome measures. Results: The average gait speed at baseline in levodopa off state was abnormally slow (80.6 cm/s). DBS activation acutely increased gait speed (97.4 cm/s, p < 0.001) which was maintained at 1- (93.0 cm/s, p < 0.001) and 12-month follow up (91.2 cm/s, p < 0.001). Acute changes during initial programming predicted chronic gait outcomes. When DBS targets were analyzed separately, only patients receiving bilateral STN or GPi DBS improved gait speed along with kinematic measures of pace, rhythm, and variability. Preoperative levodopa response of the MDS-UPDRS axial sub-score correlated with gait speed response to DBS while the total score did not. Discussion: Patients who received either bilateral STN or GPi DBS improved gait kinematic in levodopa off state at 1 year so both targets may be considered for treatment of gait dysfunction, unlike unilateral implantations which resulted in no change. Acute effects of STN or GPi DBS on gait speed should be considered when programming patients as they predict chronic outcomes. When determining DBS candidacy, the degree of axial symptom improvement with levodopa should be considered.
