After-effects of peripheral neurostimulation on brain plasticity and ankle function in chronic stroke: The role of afferents recruited

Abstract

This study tested the after-effects of neuromuscular electrical stimulation (NMES), repetitive peripheral magnetic stimulation (rPMS) and muscle tendon vibration (VIB) on brain plasticity and sensorimotor impairments in chronic stroke to investigate whether different results could depend on the nature of afferents recruited by each technique. Fifteen people with chronic stroke participated in five sessions (one per week). Baseline measures were collected in session one, then, each participant received 4 randomly ordered interventions (NMES, rPMS, VIB and a 'control' intervention of exercises). Interventions were applied to the paretic ankle muscles and parameters of application were matched as closely as possible. Standardized clinical measures of the ankle function on the paretic side and transcranial magnetic stimulation (TMS) outcomes of both primary motor cortices (M1) were collected at pre- and post-application of each intervention. The ankle muscle strength was significantly improved by rPMS and VIB (P≤0.02). rPMS influenced M1 excitability (increase in the contralesional hemisphere, P=0.03) and inhibition (decrease in both hemispheres, P≤0.04). The group mean of a few clinical outcomes improved across sessions, i.e. independently of the order of interventions. Some TMS outcomes at baseline could predict the responsiveness to rPMS and VIB. This original study suggests that rPMS and VIB were efficient to drive M1 plasticity and sensorimotor improvements, likely via massive inflows of 'pure' proprioceptive information generated. Usefulness of some TMS outcomes to predict which intervention a patient could be more responsive to should be further tested in future studies.