Selectivity and excitability of upper-limb muscle activation during cervical transcutaneous spinal cord stimulation in humans

2021 ◽  
Author(s):  
Roberto M. de Freitas ◽  
Atsushi Sasaki ◽  
Dimitry G. Sayenko ◽  
Yohei Masugi ◽  
Taishin Nomura ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Upper Limb ◽  
Spinal Cord Stimulation ◽  
Muscle Activation ◽  
Anterior Neck ◽  
Hand Muscles ◽  
Ia Afferents ◽  
Arm Muscles ◽  
Muscle Responses ◽  
Transcutaneous Spinal Cord Stimulation

Cervical transcutaneous spinal cord stimulation (tSCS) efficacy for rehabilitation of upper-limb motor function was suggested to depend on recruitment of Ia afferents. However, selectivity and excitability of motor activation with different electrode configurations remains unclear. In this study, activation of upper-limb motor pools was examined with different cathode and anode configurations during cervical tSCS in 10 able-bodied individuals. Muscle responses were measured from six upper-limb muscles simultaneously. First, post-activation depression was confirmed with tSCS paired pulses (50 ms interval) for each cathode configuration (C6, C7, and T1 vertebral levels), with anode on the anterior neck. Selectivity and excitability of activation of the upper-limb motor pools were examined by comparing the recruitment curves (10-100 mA) of first evoked responses across muscles and cathode configurations. Our results showed that hand muscles were preferentially activated when the cathode was placed over T1 compared to the other vertebral levels, while there was no selectivity for proximal arm muscles. Furthermore, higher stimulation intensities were required to activate distal hand muscles than proximal arm muscles, suggesting different excitability thresholds between muscles. In a separate protocol, responses were compared between anode configurations (anterior neck, shoulders, iliac crests, and back), with one selected cathode configuration. The level of discomfort was also assessed. Largest muscle responses were elicited with the anode configuration over the anterior neck, while there were no differences in the discomfort. Our results therefore inform methodological considerations for electrode configuration to help optimize recruitment of Ia afferents during cervical tSCS.

scholarly journals On the reflex mechanisms of cervical transcutaneous spinal cord stimulation in human subjects

2019 ◽  
Vol 121 (5) ◽  
pp. 1672-1679 ◽  
Author(s):  
Matija Milosevic ◽  
Yohei Masugi ◽  
Atsushi Sasaki ◽  
Dimitry G. Sayenko ◽  
Kimitaka Nakazawa
Keyword(s):  
Spinal Cord ◽  
Muscle Contraction ◽  
Upper Limb ◽  
Spinal Cord Stimulation ◽  
Presynaptic Inhibition ◽  
Tendon Vibration ◽  
Muscle Stretching ◽  
Muscle Tendon Vibration ◽  
Passive Muscle ◽  
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.

scholarly journals 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

2021 ◽  
Vol 10 (16) ◽  
pp. 3633
Author(s):  
Atsushi Sasaki ◽  
Roberto M. de Freitas ◽  
Dimitry G. Sayenko ◽  
Yohei Masugi ◽  
Taishin Nomura ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Short Duration ◽  
Upper Limb ◽  
Spinal Cord Stimulation ◽  
Spinal Reflex ◽  
Therapeutic Effects ◽  
Low Intensity ◽  
Reflex Excitability ◽  
Cord Injury ◽  
Transcutaneous Spinal Cord Stimulation

Cervical transcutaneous spinal cord stimulation (tSCS) has been utilized in applications for improving upper-limb sensory and motor function in patients with spinal cord injury. Although therapeutic effects of continuous cervical tSCS interventions have been reported, neurophysiological mechanisms remain largely unexplored. Specifically, it is not clear whether sub-threshold intensity and 10-min duration continuous cervical tSCS intervention can affect the central nervous system excitability. Therefore, the purpose of this study was to investigate effects of sub-motor-threshold 10-min continuous cervical tSCS applied at rest on the corticospinal and spinal reflex circuit in ten able-bodied individuals. Neurophysiological assessments were conducted to investigate (1) corticospinal excitability via transcranial magnetic stimulation applied on the primary motor cortex to evoke motor-evoked potentials (MEPs) and (2) spinal reflex excitability via single-pulse tSCS applied at the cervical level to evoke posterior root muscle (PRM) reflexes. Measurements were recorded from multiple upper-limb muscles before, during, and after the intervention. Our results showed that low-intensity and short-duration continuous cervical tSCS intervention applied at rest did not significantly affect corticospinal and spinal reflex excitability. The stimulation duration and/or intensity, as well as other stimulating parameters selection, may therefore be critical for inducing neuromodulatory effects during cervical tSCS.

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

2019 ◽  
Vol 34 (1) ◽  
pp. 3-12 ◽  
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.

scholarly journals Successful application of burst spinal cord stimulation for refractory upper limb pain: a case series

2021 ◽  
Vol 49 (3) ◽  
pp. 030006052110040
Author(s):  
Kuen Su Lee ◽  
Yoo Kyung Jang ◽  
Gene Hyun Park ◽  
In Jae Jun ◽  
Jae Chul Koh
Keyword(s):  
Spinal Cord ◽  
Upper Limb ◽  
Spinal Cord Stimulation ◽  
Therapeutic Potential ◽  
Case Series ◽  
Limb Amputation ◽  
Intractable Pain ◽  
Limb Pain ◽  
Cord Injury ◽  
Upper Limb Pain

Spinal cord stimulation (SCS) has been used to treat sustained pain that is intractable despite various types of treatment. However, conventional tonic waveform SCS has not shown promising outcomes for spinal cord injury (SCI) or postamputation pain. The pain signal mechanisms of burst waveforms are different to those of conventional tonic waveforms, but few reports have presented the therapeutic potential of burst waveforms for the abovementioned indications. This current case report describes two patients with refractory upper limb pain after SCI and upper limb amputation that were treated with burst waveform SCS. While the patients could not obtain sufficient therapeutic effect with conventional tonic waveforms, the burst waveforms provided better pain reduction with less discomfort. However, further studies are necessary to better clarify the mechanisms and efficacy of burst waveform SCS in patients with intractable pain.

Treatment of reflex sympathetic dystrophy (R.S.D.) of the upper limb by means of spinal cord stimulation (S.C.S.)

Pain ◽  
1990 ◽  
Vol 41 ◽  
pp. S78 ◽  
Author(s):  
J. Pallaces ◽  
M.J. Pallares ◽  
P. Fenollosa ◽  
V. Chover ◽  
T. Santonja ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Upper Limb ◽  
Spinal Cord Stimulation ◽  
Reflex Sympathetic Dystrophy
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