Vagus Nerve Stimulation Paired With Upper Extremity Rehabilitation for Chronic Ischemic Stroke: Contribution of Dosage Parameters

Background Vagus nerve stimulation (VNS) combined with rehabilitation is a Food and Drug Administration approved intervention for moderate to severe upper extremity deficits in chronic ischemic stroke patients. Previous studies demonstrated that VNS improves upper extremity motor impairments, using the Fugl Meyer Assessment of Upper Extremity (FMA-UE); however, delineating where these improvements occur, and the role of VNS dosage parameters were not reported. Objective This study explored the relationship between dosing (time over which task repetitions were executed and number of VNS stimulations) and changes within proximal and distal components of the FMA-UE. Methods Participants underwent VNS implantation, with 1 group receiving VNS paired with rehabilitation (Active VNS) and the other group receiving rehabilitation with sham stimulation (Controls). Both groups received 6 weeks of in-clinic therapy followed by a 90-day at-home, self-rehabilitation program. Participants who completed at least 12 of 18 in-clinic sessions were included in the analyses (n = l06). Pearson correlations and analysis of covariance were used to investigate the relationship between dosing and FMA-UE outcome change along with the effect of covariates including baseline severity, time since stroke, age, and paretic side. Results Compared to Controls, active VNS favorably influenced distal function with sustained improvement after the home program. Significant improvements were observed in only distal components (FMdist) at both post day-1 (1.80 points, 95% Cl [0.85, 2.73], P