Transcutaneous Spinal Cord Stimulation Enhances Quadriceps Motor Evoked Potential in Healthy Participants: A Double-Blind Randomized Controlled Study.

Álvaro Megía-García,Natalia Comino-Suárez,Juan Avendaño-Coy,Julio Gómez-Soriano,Diego Serrano-Muñoz,Julian Taylor

doi:10.3390/jcm9103275

Abstract

Transcutaneous electrical spinal cord stimulation (tSCS) is a non-invasive technique for neuromodulation and has therapeutic potential for motor rehabilitation following spinal cord injury. The main aim of the present study is to quantify the effect of a single session of tSCS on lower limb motor evoked potentials (MEPs) in healthy participants. A double-blind, sham-controlled, randomized, crossover, clinical trial was carried out in 15 participants. Two 10-min sessions of tSCS (active-tSCS and sham-tSCS) were applied at the T11-T12 vertebral level. Quadriceps (Q) and tibialis anterior (TA) muscle MEPs were recorded at baseline, during and after tSCS. Q and TA isometric maximal voluntary contraction was also recorded. A significant increase of the Q-MEP amplitude was observed during active-tSCS (1.96 ± 0.3 mV) when compared from baseline (1.40 ± 0.2 mV; p = 0.01) and when compared to sham-tSCS at the same time-point (1.13 ± 0.3 mV; p = 0.03). No significant modulation was identified for TA-MEP amplitude or for Q and TA isometric maximal voluntary isometric strength. In conclusion, tSCS applied over the T11-T12 vertebral level increased Q-MEP but not TA-MEP compared to sham stimulation. The specific neuromodulatory effect of tSCS on Q-MEP may reflect optimal excitation of this motor response at the interneuronal or motoneuronal level.

Highlights

Transcutaneous electrical spinal cord stimulation is a non-invasive technique designed to generate neuromodulation of the central nervous system at the spinal cord level
During the active Transcutaneous electrical spinal cord stimulation (tSCS) session, a 0.91 intraclass correlation coefficient (ICC) was registered for Q-motor evoked potentials (MEPs) amplitude and a 0.97 ICC for tibialis anterior (TA)-MEP amplitude
Our study observed a significant increase of MEP amplitude in the Q muscle, which is innervated by the L1-L2 spinal level that corresponded to the level of tSCS

Summary

Introduction

Transcutaneous electrical spinal cord stimulation (tSCS) is a non-invasive technique designed to generate neuromodulation of the central nervous system at the spinal cord level. TSCS modulates the excitability of sensorimotor circuits which are affected by epidural stimulation [3]. Both techniques can evoke posterior root muscle (PRM) reflex responses measured at the target muscle [3]. The low PRM reflex threshold response to stimulation, suggests that tSCS activates large-to-medium diameter afferent fibers (Ia, Ib, II) within the sensory dorsal roots [1,3]. The similarity between PRM and Hoffmann reflex responses suggests that tSCS activates proprioceptive Ia afferent fibers [4,5]

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