Backward locomotor treadmill training combined with transcutaneous spinal direct current stimulation in stroke: a randomized pilot feasibility and safety study

Abstract

Walking impairment impacts nearly 66% of stroke survivors and is a rising cause of morbidity worldwide. Despite conventional post-stroke rehabilitative care, the majority of stroke survivors experience continued limitations in their walking speed, temporospatial dynamics and walking capacity. Hence, novel and comprehensive approaches are needed to improve the trajectory of walking recovery in stroke survivors. Herein, we test the safety, feasibility and preliminary efficacy of two approaches for post-stroke walking recovery: backward locomotor treadmill training and transcutaneous spinal direct current stimulation. In this double-blinded study, 30 chronic stroke survivors (>6 months post-stroke) with mild-severe residual walking impairment underwent six 30-min sessions (three sessions/week) of backward locomotor treadmill training, with concurrent anodal (N = 19) or sham transcutaneous spinal direct current stimulation (N = 11) over the thoracolumbar spine, in a 2:1 stratified randomized fashion. The primary outcomes were: per cent participant completion, safety and tolerability of these two approaches. In addition, we collected data on training-related changes in overground walking speed, cadence, stride length (baseline, daily, 24-h post-intervention, 2 weeks post-intervention) and walking capacity (baseline, 24-h post-intervention, 2 weeks post-intervention), as secondary exploratory aims testing the preliminary efficacy of these interventions. Eighty-seven per cent (N = 26) of randomized participants completed the study protocol. The majority of the study attrition involved participants with severe baseline walking impairment. There were no serious adverse events in either the backward locomotor treadmill training or transcutaneous spinal direct current stimulation approaches. Also, both groups experienced a clinically meaningful improvement in walking speed immediately post-intervention that persisted at the 2-week follow-up. However, in contrast to our working hypothesis, anodal-transcutaneous spinal direct current stimulation did not enhance the degree of improvement in walking speed and capacity, relative to backward locomotor treadmill training + sham, in our sample. Backward locomotor treadmill training and transcutaneous spinal direct current stimulation are safe and feasible approaches for walking recovery in chronic stroke survivors. Definitive efficacy studies are needed to validate our findings on backward locomotor treadmill training-related changes in walking performance. The results raise interesting questions about mechanisms of locomotor learning in stroke, and well-powered transcutaneous spinal direct current stimulation dosing studies are needed to understand better its potential role as a neuromodulatory adjunct for walking rehabilitation.

Keywords: backward walking; gait; non-invasive spinal stimulation; post-stroke walking; stroke rehabilitation.

Graphical Abstract

Figure 1

Training schematic. Study participants underwent six (D2–D7), 30-min sessions of non-bodyweight supported BLTT, with concurrent sham or anodal tsDCS, applied over T-11/12 (red rectangle) and cathode electrode placed over the right shoulder (black rectangle).

Figure 2

Flow diagram of the study.

Figure 3

Walking speed and metrics. Mean change in 10MWT speed (A), Cadence (D) and Stride Length (G), during 6 days of BLTT (D2–D7), 24 h, and 2-week follow-up (error bar in SEM). Cumulative training-related changes (D8–D2), for 10MWT (B), Cadence (E), and Stride Length (H), represented as the median and interquartile range. Retention of performance at 2-week follow-up (D9–D8) for 10MWT (C), Cadence (F), represented as the median and interquartile range (I).

Figure 4

Walking capacity. Mean change in the 6-min walk test (6MWT) at screening baseline (D1), 24-h post-BLTT training, and 2-week follow-up (D9) (A), (error bar in SEM). Cumulative training-related change (B), and retention of performance at 2-week follow-up (C) represented as the median and interquartile range.