Remote muscle contraction enhances spinal reflexes in multiple lower-limb muscles elicited by transcutaneous spinal cord stimulation

Transcutaneous and epidural electrical spinal cord stimulation techniques are becoming more valuable as electrophysiological and clinical tools. Recently, remarkable recovery of the upper limb sensorimotor function during cervical spinal stimulation was demonstrated. In the present study, we sought to elucidate the neural mechanisms underlying the effects of transcutaneous spinal cord stimulation (tSCS) of the cervical spine. We hypothesized that cervical tSCS can be used to selectively activate the sensory route entering the spinal cord and transsynaptically converge on upper limb motor pools. To test this hypothesis, we applied cervical tSCS using paired stimuli (homosynaptic depression) and during passive muscle stretching of the wrist flexor (presynaptic inhibition via Ia afferents), voluntary hand muscle contraction (descending facilitation of motoneuron pool), and muscle-tendon vibration of the wrist (presynaptic inhibition via afferent occlusion). Our results demonstrate significant inhibition of the second evoked response during paired stimulus delivery, inhibition of responses during passive muscle stretching and muscle-tendon vibration, and facilitation during voluntary muscle contraction, which share similarities with responses evoked during lumbosacral tSCS. These results indicate that the route of the stimulation current transmission passes via afferents in the dorsal roots through the spinal cord to activate the motor pools and potentially interneuronal networks projecting to upper limb muscles. Using a novel stimulation paradigm, our study is the first to present evidence of the sensory neuronal pathway of the cervical tSCS propagation. Overall, our work demonstrates the utility and sensitivity of cervical tSCS to engage the sensory pathway projecting to the upper limbs. NEW & NOTEWORTHY Despite therapeutic effects that have been demonstrated previously using noninvasive cervical spinal stimulation, it has been unclear whether, and to what degree, the stimulation can activate the sensory afferent system. Our study presents evidence that cervical transcutaneous spinal cord stimulation can engage the sensory pathways and transsynaptically converge on motor pools projecting to upper limb muscles, demonstrating the utility and sensitivity of cervical spinal stimulation for electrophysiological assessments and neurorehabilitation.

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Electromyographic investigation of order of participation of trunk and lower limb muscles of patients with total and partial transection of the spinal cord

Bulletin of Experimental Biology and Medicine ◽

10.1007/bf01250874 ◽

1970 ◽

Vol 69 (4) ◽

pp. 389-393 ◽

Cited By ~ 1

Author(s):

T. N. Nesmeyanova ◽

A. N. Trankvillitati

Keyword(s):

Spinal Cord ◽

Lower Limb ◽

Lower Limb Muscles ◽

Limb Muscles ◽

Electromyographic Investigation

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Phase-dependent electromyographic activity of the lower-limb muscles of a patient with clinically complete spinal cord injury during orthotic gait

Experimental Brain Research ◽

10.1007/s002210050387 ◽

1998 ◽

Vol 120 (1) ◽

pp. 139-142 ◽

Cited By ~ 12

Author(s):

Narumi Kojima ◽

Kimitaka Nakazawa ◽

Shin-Ichiroh Yamamoto ◽

Hideo Yano

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Lower Limb ◽

Electromyographic Activity ◽

Lower Limb Muscles ◽

Cord Injury ◽

Limb Muscles ◽

Complete Spinal Cord Injury

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Effects of movement-related afferent inputs on spinal reflexes evoked by transcutaneous spinal cord stimulation during robot-assisted passive stepping

Neuroscience Letters ◽

10.1016/j.neulet.2016.05.047 ◽

2016 ◽

Vol 627 ◽

pp. 100-106 ◽

Cited By ~ 8

Author(s):

Yohei Masugi ◽

Noritaka Kawashima ◽

Daisuke Inoue ◽

Kimitaka Nakazawa

Keyword(s):

Spinal Cord ◽

Spinal Cord Stimulation ◽

Spinal Reflexes ◽

Robot Assisted ◽

Afferent Inputs ◽

Transcutaneous Spinal Cord Stimulation

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Transcutaneous Spinal Cord Stimulation and Motor Rehabilitation in Spinal Cord Injury: A Systematic Review

Neurorehabilitation and Neural Repair ◽

10.1177/1545968319893298 ◽

2019 ◽

Vol 34 (1) ◽

pp. 3-12 ◽

Cited By ~ 4

Author(s):

Alvaro Megía García ◽

Diego Serrano-Muñoz ◽

Julian Taylor ◽

Juan Avendaño-Coy ◽

Julio Gómez-Soriano

Keyword(s):

Systematic Review ◽

Spinal Cord ◽

Spinal Cord Injury ◽

Electrical Stimulation ◽

Lower Limb ◽

Spinal Cord Stimulation ◽

Voluntary Movement ◽

Muscle Activation ◽

Cord Injury ◽

Transcutaneous Spinal Cord Stimulation

Background. Epidural spinal electrical stimulation at the lumbar spinal level evokes rhythmic muscle activation of lower-limb antagonists, attributed to the central pattern generator. However, the efficacy of noninvasive spinal stimulation for the activation of lower-limb muscles is not yet clear. This review aimed to analyze the feasibility and efficacy of noninvasive transcutaneous spinal cord stimulation (tSCS) on motor function in individuals with spinal cord injury. Methods. A search for tSCS studies was made of the following databases: PubMed; Cochrane Registry; and Physiotherapy Evidence Database (PEDro). In addition, an inverse manual search of the references cited by the identified articles was carried out. The keywords transcutaneous, non-invasive, electrical stimulation, spinal cord stimulation [Mesh term], and spinal cord injury were used. Results. A total of 352 articles were initially screened, of which 13 studies met the inclusion criteria for systematic review. The total participant sample comprised 55 persons with spinal cord injury. All studies with tSCS provided evidence of induced muscle activation in the lower and upper limbs, and applied stimulation at the level of the T11-T12 and C4-C7 interspinous space, respectively. All studies reported an increase in motor response measured by recording surface electromyography, voluntary movement, muscle strength, or function. Conclusions. Although this review highlights tSCS as a feasible therapeutic neuromodulatory strategy to enhance voluntary movement, muscle strength, and function in patients with chronic spinal cord injury, the clinical impact and efficacy of electrode location and current intensity need to be characterized in statistically powered and controlled clinical trials.

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Spasms after spinal cord injury show low-frequency intermuscular coherence

Journal of Neurophysiology ◽

10.1152/jn.00112.2018 ◽

2018 ◽

Vol 120 (4) ◽

pp. 1765-1771

Author(s):

Stefane A. Aguiar ◽

Stuart N. Baker ◽

Katie Gant ◽

Jorge Bohorquez ◽

Christine K. Thomas

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Lower Limb ◽

Low Frequency ◽

Low Frequencies ◽

First Report ◽

Lower Limb Muscles ◽

Cord Injury ◽

Limb Muscles ◽

Intermuscular Coherence

Intermuscular coherence allows the investigation of common input to muscle groups. Although beta-band (15–30 Hz) intermuscular coherence is well understood as originating from the cortex, the source of intermuscular coherence at lower frequencies is still unclear. We used a wearable device that recorded electromyographic (EMG) signals during a 24-h period in four lower limb muscles of seven spinal cord injury patients (American Spinal Cord Injury Association impairment scale: A, 6 subjects; B, 1 subject) while they went about their normal daily life activities. We detected natural spasms occurring during these long-lasting recordings and calculated intermuscular coherence between all six possible combinations of muscle pairs. There was significant intermuscular coherence at low frequencies, between 2 and 13 Hz. The most likely source for this was the spinal cord and its peripheral feedback loops, because the spinal lesions in these patients had interrupted connections to supraspinal structures. This is the first report to demonstrate that the spinal cord is capable of producing low-frequency intermuscular coherence with severely reduced or abolished descending drive. NEW & NOTEWORTHY This is the first report to demonstrate that intermuscular coherence between lower limb muscles at low frequencies can be produced by the spinal cord with severely reduced or abolished descending drive.

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