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

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.

Effect of Cervical Transcutaneous Spinal Cord Stimulation on Sensorimotor Cortical Activity during Upper-Limb Movements in Healthy Individuals

“…The plots only display power values that significantly differed (p < 0.05) from baseline, as determined by a cluster-based permutation test. Each movement type showed significant broadband (8-25 Hz) ERD with particular power suppression in the alpha band (8)(9)(10)(11)(12). Right and bimanual movements tend to show similar patters of ERD regardless of whether tSCS had been applied or not.…”

“…Numerous studies have investigated tSCS modulation at both the cortical and spinal level [7][8][9][10][11][12][13]. Benavides et al, for example, investigated cortical modulation by comparing motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) before and after 20 min of tSCS.…”

Low-Intensity and Short-Duration Continuous Cervical Transcutaneous Spinal Cord Stimulation Intervention Does Not Prime the Corticospinal and Spinal Reflex Pathways in Able-Bodied Subjects

“…In this study, continuous cervical tSCS was delivered at 30 Hz with biphasic rectangular pulses of 400-µs width and stimulation intensities at a level to elicit paresthesias in the upper-limb muscles for a total duration of 10 min while participants remained in the supine position at rest. Many previous studies reporting therapeutic effects of tSCS used stimulation frequencies between 15 and 50 Hz [6,[10][11][12]15,26,28,39,40], while we used 30 Hz in the current study. We also used 400-µs pulse width, which was within the range previously utilized in neuromodulation applications.…”

Trans-Spinal Electrical Stimulation Therapy for Functional Rehabilitation after Spinal Cord Injury: Review

“…tsPCS at greater intensities (>80 mA) activates the trunk musculature which helps to maintain posture [ 18 ] and the duration of stimulation should be no less than 20 min to produce therapeutic effects [ 117 ]. Simultaneously, tsPCS at the L1–L2 sites at 15 Hz enables the extension of the trunk muscles leading to postural stability [ 19 ], while at 30–50 Hz, stimulation for more than 20 min evokes responses and produces a greater possibility of functional improvement for trunk control in SCI [ 47 ]. During tsPCS stimulation, the movement of flexor muscles exhibits an increment during the delivery of a higher frequency (80–100 Hz), whereas a lower frequency (20–30 Hz) increases the extensor group movement [ 18 ].…”

“…To harness the benefits and to avoid the complications of an epidural SCS, a noninvasive spinal cord neuromodulation modality, called transcutaneous SCS, has been developed and investigated recently [ 45 , 46 , 47 , 48 ]. Transcutaneous stimulation can be induced alone or in combination with functional therapy, which leads to an increased motor function in patients with chronic paralysis [ 17 , 49 ].…”