The relationship between maximum tolerance and motor activation during transcutaneous spinal stimulation is unaffected by the carrier frequency or vibration.
TL;DR: The results suggest that, when considering the intensity of stimulation required to obtain spinally evoked motor potentials, neither alternative stimulation paradigm is more effective at reducing discomfort than the conventional, unmodulated pulse configuration.
Abstract: Transcutaneous spinal stimulation (TSS) is a useful tool to modulate spinal sensorimotor circuits and has emerged as a potential treatment for motor disorders in neurologically impaired populations. One major limitation of TSS is the discomfort associated with high levels of stimulation during the experimental procedure. The objective of this study was to examine if the discomfort caused by TSS can be alleviated using different stimulation paradigms in a neurologically intact population. Tolerance to TSS delivered using conventional biphasic balanced rectangular pulses was compared to two alternative stimulation paradigms: a 5 kHz carrier frequency and biphasic balanced rectangular pulses combined with vibrotactile stimulation. In ten healthy participants, tolerance to TSS was examined using both single-pulse (0.2 Hz) and continuous (30 Hz) stimulation protocols. In both the single-pulse and continuous stimulation protocols, participants tolerated significantly higher levels of stimulation with the carrier frequency paradigm compared to the other stimulation paradigms. However, when the maximum tolerable stimulation intensity of each stimulation paradigm was normalized to the intensity required to evoke a lower limb muscle response, there were no statistical differences between the stimulation paradigms. Our results suggest that, when considering the intensity of stimulation required to obtain spinally evoked motor potentials, neither alternative stimulation paradigm is more effective at reducing discomfort than the conventional, unmodulated pulse configuration.
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TL;DR: In this article, a systematic search for studies published until May 2021 was made of the following databases: EMBASE, Medline (Ovid) and Web of Science, and two reviewers independently screened the studies, extracted the data, and evaluated the quality of included trials.
Abstract: Background Transcutaneous spinal cord stimulation (tSCS) is a non-invasive modality in which electrodes can stimulate spinal circuitries and facilitate a motor response. This review aimed to evaluate the methodology of studies using tSCS to generate motor activity in persons with spinal cord injury (SCI) and to appraise the quality of included trials. Methods A systematic search for studies published until May 2021 was made of the following databases: EMBASE, Medline (Ovid) and Web of Science. Two reviewers independently screened the studies, extracted the data, and evaluated the quality of included trials. The electrical characteristics of stimulation were summarised to allow for comparison across studies. In addition, the surface electromyography (EMG) recording methods were evaluated. Results A total of 3753 articles were initially screened, of which 25 met the criteria for inclusion. Studies were divided into those using tSCS for neurophysiological investigations of reflex responses (n = 9) and therapeutic investigations of motor recovery (n = 16). The overall quality of evidence was deemed to be poor-to-fair (10.5 ± 4.9) based on the Downs and Black Quality Checklist criteria. The electrical characteristics were collated to establish the dosage range across stimulation trials. The methods employed by included studies relating to stimulation parameters and outcome measurement varied extensively, although some trends are beginning to appear in relation to electrode configuration and EMG outcomes. Conclusion This review outlines the parameters currently employed for tSCS of the cervicothoracic and thoracolumbar regions to produce motor responses. However, to establish standardised procedures for neurophysiological assessments and therapeutic investigations of tSCS, further high-quality investigations are required, ideally utilizing consistent electrophysiological recording methods, and reporting common characteristics of the electrical stimulation administered.
17 citations
TL;DR: In this article, the safety and efficacy of transcutaneous spinal stimulation to enable upright sitting posture in 8 children with trunk control impairment due to acquired SCI using within-subject repeated measures study design.
Abstract: In children with spinal cord injury (SCI), scoliosis due to trunk muscle paralysis frequently requires surgical treatment. Transcutaneous spinal stimulation enables trunk stability in adults with SCI and may pose a non-invasive preventative therapeutic alternative. This non-randomized, non-blinded pilot clinical trial (NCT03975634) determined the safety and efficacy of transcutaneous spinal stimulation to enable upright sitting posture in 8 children with trunk control impairment due to acquired SCI using within-subject repeated measures study design. Primary safety and efficacy outcomes (pain, hemodynamics stability, skin irritation, trunk kinematics) and secondary outcomes (center of pressure displacement, compliance rate) were assessed within the pre-specified endpoints. One participant did not complete the study due to pain with stimulation on the first day. One episode of autonomic dysreflexia during stimulation was recorded. Following hemodynamic normalization, the participant completed the study. Overall, spinal stimulation was well-tolerated and enabled upright sitting posture in 7 out of the 8 participants. Scoliosis due to trunk muscle paralysis frequently requires surgical treatment in children with spinal cord injury. The authors demonstrate the safety and efficacy of transcutaneous spinal stimulation to enable upright sitting posture in 7/8 children with trunk control impairment in a within-subjects, repeated measures pilot clinical trial.
15 citations
TL;DR: The two most promising noninvasive spinal cord electrical stimulation methods of SCI rehabilitation treatment, namely, trans-spinal direct current stimulation (tsDCS) and trans-Spinal pulsed current stimulating (tsPCS) are summarized.
Abstract: Spinal cord injury (SCI) is one of the most debilitating injuries in the world. Complications after SCI, such as respiratory issues, bowel/bladder incontinency, pressure ulcers, autonomic dysreflexia, spasticity, pain, etc., lead to immense suffering, a remarkable reduction in life expectancy, and even premature death. Traditional rehabilitations for people with SCI are often insignificant or ineffective due to the severity and complexity of the injury. However, the recent development of noninvasive electrical neuromodulation treatments to the spinal cord have shed a ray of hope for these individuals to regain some of their lost functions, a reduction in secondary complications, and an improvement in their life quality. For this review, 250 articles were screened and about 150 were included to summarize the two most promising noninvasive spinal cord electrical stimulation methods of SCI rehabilitation treatment, namely, trans-spinal direct current stimulation (tsDCS) and trans-spinal pulsed current stimulation (tsPCS). Both treatments have demonstrated good success in not only improving the sensorimotor function, but also autonomic functions. Due to the noninvasive nature and lower costs of these treatments, in the coming years, we expect these treatments to be integrated into regular rehabilitation therapies worldwide.
11 citations
TL;DR: In this article , the effects of transcutaneous electrical spinal cord stimulation (TSCS) and conventional task-specific rehabilitation (TSR) on trunk control and sitting stability in people with chronic tetraplegia secondary to a spinal cord injury (SCI) were examined.
Abstract: The aim of this study was to examine the effects of transcutaneous electrical spinal cord stimulation (TSCS) and conventional task-specific rehabilitation (TSR) on trunk control and sitting stability in people with chronic tetraplegia secondary to a spinal cord injury (SCI). Five individuals with complete cervical (C4–C7) cord injury participated in 24-week therapy that combined TSCS and TSR in the first 12 weeks, followed by TSR alone for another 12 weeks. The TSCS was delivered simultaneously at T11 and L1 spinal levels, at a frequency ranging from 20–30 Hz with 0.1–1.0 ms. pulse width biphasically. Although the neurological prognosis did not manifest after either treatment, the results show that there were significant increases in forward reach distance (10.3 ± 4.5 cm), right lateral reach distance (3.7 ± 1.8 cm), and left lateral reach distance (3.0 ± 0.9 cm) after the combinational treatment (TSCS+TSR). The stimulation also significantly improved the participants’ trunk control and function in sitting. Additionally, the trunk range of motion and the electromyographic response of the trunk muscles were significantly elevated after TSCS+TSR. The TSCS+TSR intervention improved independent trunk control with significantly increased static and dynamic sitting balance, which were maintained throughout the TSR period and the follow-up period, indicating long-term sustainable recovery.
6 citations
01 Jan 2015
TL;DR: In this article, the authors observed selective activation of proximal and distal motor pools during epidural spinal stimulation in leg muscles during transcutaneous and epidural electrical spinal cord stimulation.
Abstract: Transcutaneous and epidural electrical spinal cord stimulation techniques are becoming more valuable as electrophysiological and clinical tools. Recently, we observed selective activation of proximal and distal motor pools during epidural spinal stimulation. In the present study, we hypothesized that the characteristics of recruitment curves obtained from leg muscles will reflect a relative preferential activation of proximal and distal motor pools based on their arrangement along the lumbosacral enlargement. The purpose was to describe the electrophysiological responses to transcutaneous stimulation in leg muscles innervated by motoneurons from different segmental levels. Stimulation delivered along the rostrocaudal axis of the lumbosacral enlargement in the supine position resulted in a selective topographical recruitment of proximal and distal leg muscles, as described by threshold intensity, slope of the recruitment curves, and plateau point intensity and magnitude. Relatively selective recruitment of proximal and distal motor pools can be titrated by optimizing the site and intensity level of stimulation to excite a given combination of motor pools. The slope of the recruitment of particular muscles allows characterization of the properties of afferents projecting to specific motoneuron pools, as well as to the type and size of the motoneurons. The location and intensity of transcutaneous spinal electrical stimulation are critical to target particular neural structures across different motor pools in investigation of specific neuromodulatory effects. Finally, the asymmetry in bilateral evoked potentials is inevitable and can be attributed to both anatomical and functional peculiarities of individual muscles or muscle groups.
6 citations
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7,479 citations
"The relationship between maximum to..." refers background in this paper
...…either primary afferent depolarization of large cutaneous fibers (see Whitehorn & Burgess, 1973 and Rudomin & Schmidt, 1999 for review), or the activation of inhibitory interneurons (see Gate Control Theory by Melzack & Wall (1965); see also Hollins, McDermott, & Harper (2014) for a review)....
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...This was demonstrated for pain associated with radiant heat, itch, and electrical stimulation (Higgins et al., 1971; Melzack & Schecter, 1965; Melzack & Wall, 1965; Sullivan, 1968)....
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TL;DR: Intaspinal terminals of sensory fibers are not hard-wired conductors of the information generated in their peripheral sensory receptors, but dynamic systems that convey information that can be selectively addressed by central mechanisms to specific neuronal targets.
Abstract: The present review examines the experimental evidence supporting the existence of central mechanisms able to modulate the synaptic effectiveness of sensory fibers ending in the spinal cord of vertebrates. The first section covers work on the mode of operation and the synaptic mechanisms of presynaptic inhibition, in particular of the presynaptic control involving axo-axonic synapses made by GABAergic interneurons with the terminal arborizations of the afferent fibers. This includes reviewing of the ionic mechanisms involved in the generation of primary afferent depolarization (PAD) by GABAergic synapses, the ultrastructural basis underlying the generation of PAD, the relationship between PAD and presynaptic inhibition, the conduction of action potentials in the terminal arborizations of the afferent fibers, and the modeling of the presynaptic inhibitory synapse. The second section of the review deals with the functional organization of presynaptic inhibition. This includes the segmental and descending presynaptic control of the synaptic effectiveness of group-I and group-II muscle afferents, the evidence dealing with the local character of PAD as well as the differential inhibition of PAD in selected collaterals of individual muscle-spindle afferents by cutaneous and descending inputs. This section also examines observations on the presynaptic modulation of large cutaneous afferents, including the modulation of the synaptic effectiveness of thin myelinated and unmyelinated cutaneous fibers and of visceral afferents, as well as the presynaptic control of the synaptic actions of interneurons and descending tract neurons. The third section deals with the changes in PAD occurring during sleep and fictive locomotion in higher vertebrates and with the changes of presynaptic inhibition in humans during the execution of a variety of voluntary movements. In the final section, we examine the non-synaptic presynaptic modulation of transmitter release, including the possibility that the intraspinal endings of primary afferents also release colocalized peptides in a similar way as in the periphery. The outcome of the studies presently reviewed is that intraspinal terminals of sensory fibers are not hard-wired conductors of the information generated in their peripheral sensory receptors, but dynamic systems that convey information that can be selectively addressed by central mechanisms to specific neuronal targets. This central control of information flow in peripheral afferents appears to play an important role in the generation of integrated movements and processing of sensory information, including nociceptive information.
699 citations
"The relationship between maximum to..." refers background in this paper
...…by small Aδ or C-fibers can be reduced through either primary afferent depolarization of large cutaneous fibers (see Whitehorn & Burgess, 1973 and Rudomin & Schmidt, 1999 for review), or the activation of inhibitory interneurons (see Gate Control Theory by Melzack & Wall (1965); see also…...
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TL;DR: Weiss's formula, which relates threshold charge to stimulus duration, provided an accurate fit for the experimental data, and the study validated that, using it, relatively few experimental measurements were required to calculate the time constant.
Abstract: The strength—duration time constant (τSD) is a property of nodal membrane and, while it depends on a number of factors, its measurement may shed light on axonal properties when taken in conjunction with measurements of axonal excitability. For example, τSD increases with demyelination as the exposed membrane is enlarged by inclusion of paranodal and internodal membrane, it decreases with hyperpolarization and it increases with depolarization. The present study was undertaken in 20 normal volunteers to compare strength—duration curves for compound sensory and muscle action potentials, to determine the most appropriate curve fitting equation for the data, and to examine the reproducibility of the calculated time constant on different days, for potentials of different amplitude and at different sites along the nerve. Using a computerized threshold-tracking system, stimulus intensity was adjusted to produce
an antidromic compound sensory action potential (CSAP) or an orthodromic muscle action potential of 30% of maximum. Stimulus duration was increased every minute in 20 μs steps from 20 μs to 1 ms. The time constant for compound sensory potentials (665±182 μs) was longer than that for compound EMG potentials (459±126 μs). Weiss's formula, which relates threshold charge to stimulus duration, provided an accurate fit for the experimental data, and the study validated that, using it, relatively few experimental measurements were required to calculate the time constant. In repeated studies on the same subject, time constants usually differed by <400 μs for sensory axons and <250 μs for motor axons. They were identical at different sites along the nerve and did not alter with the size of the compound action potential. These characteristics suggest that the determinations of strength-duration time constant could be suitable for clinical usage.
332 citations
TL;DR: In most patients the best pain reducing effect was obtained when the vibratory stimulation was applied with moderate pressure, and the bestpain reducing site was found to be either the area of pain, the affected muscle or tendon, the antagonistic muscle or a trigger point outside the painful area.
Abstract: Summary In the present study 366 patients suffering acute or chronic musculoskeletal pain of different origin were given vibratory stimulation for the pain. Many of the patients had previously had treatments of various kinds without satisfactory relief. The effect of vibratory stimulation was assessed during and after stimulation using a graphic rating scale. Sixty-nine per cent of the patients reported a reduction of pain during vibratory stimulation. The best pain reducing site was found to be either the area of pain, the affected muscle or tendon, the antagonistic muscle or a trigger point outside the painful area. In most patients the best pain reducing effect was obtained when the vibratory stimulation was applied with moderate pressure. To obtain a maximal duration of pain relief the stimulation had to be applied for about 25-45 min.
207 citations