Transcutaneous Electrical Spinal Cord Stimulation Research Articles

Case report: Virtual reality-based arm and leg cycling combined with transcutaneous electrical spinal cord stimulation for early treatment of a cervical spinal cord injured patient

Spinal cord injury is a condition affecting the central nervous system, causing different levels of dysfunction below the point of nerve damage. A 50-year-old woman suffered a neck injury as a result of a car accident. After undergoing posterior cervical C3–C6 internal fixation with titanium plates on one side and C7 lamina decompression, the patient, who had been diagnosed with C3–C7 cervical disk herniation and spinal stenosis causing persistent compression of the spinal cord, was transferred to the rehabilitation department. After implementing the combined therapy of Virtual Reality-based arm and leg cycling along with transcutaneous electrical stimulation of the spinal cord, the patients experienced a notable enhancement in both sensory and motor abilities as per the ASIA scores. The patient’s anxiety and depression were reduced as measured by the Hamilton Anxiety and Hamilton Depression Tests. As evaluated by the SCIM-III, the patient’s self-reliance and capacity to carry out everyday tasks showed ongoing enhancement, leading to the restoration of their functionality. Hence, the use of Virtual Reality-based arm and leg cycling along with transcutaneous electrical spinal cord stimulation has potential to positively impact function in patients with spinal cord injury. However, as this is a case report, the small number of patients and the fact that the intervention was initiated early after the injury, we were unable to separate the recovery due to the intervention from the natural recovery that is known to occur in the initial weeks and months after SCI. Therefore, further randomized controlled trials with a large sample size is necessary.

Transcranial Magnetic and Transcutaneous Spinal Cord Electrical Stimulation a Stroke-Patients Walking Correction: Blinded Clinical Randomised Study

INTRODUCTION. The impairment of motor system function due to stroke often leads to patients’ dependence on external assistance. The technique of rhythmic transcranial magnetic stimulation (rTMS) is now widely used in the restoration of impaired central nervous system (CNS) function. In recent years, there has been information about the use of transcutaneous electrical spinal cord stimulation (TSCS) in the correction of motor functions in CNS disorders of various genesis.
 AIM. To evaluate the possibilities of combined use of transcranial magnetic and transcutaneous electrical stimulation of the spinal cord in the correction of locomotor functions in patients after ischemic stroke.
 MATERIALS AND METHODS. The conducted blind clinical randomized study involved patients who had an ischemic stroke. Study participants were randomly divided into control (n = 12) and experimental (n = 9) groups. Patients in the control group received standardized neurorehabilitation techniques. The participants of the experimental group were offered standardized neurorehabilitation techniques combined with rTMS and TSCS. High-frequency rTMS was performed in the projection of the sensory-motor cortex on the side of the lesion, in the area of innervation of the lower limb. During TSCS, a stimulating electrode was placed between Th11–Th12, indifferent electrodes were placed in the region of the iliac crests, and the lumbar enlargement of the spinal cord was stimulated. The dynamics of neurological deficit was assessed using the rehabilitation routing scale, the Rivermead mobility index, the Berg balance scale, and a six-point scale for assessing muscle strength. The excitability of the neural networks of the spinal cord was determined using TSCS at the T11–T12 level, with electromyographic recording of the evoked motor responses of the muscles of the lower extremities.
 RESULTS AND DISCUSSION. The combined use of rTMS and TSCS in the rehabilitation of patients in the acute period after ischemic stroke leads to an increase in the excitability of neuronal networks of the lumbar thickening of the spinal cord, a decrease in the activation thresholds of the RF, BF, TA and GM muscles of the affected limb (by 7.7 ma, 18.3 ma, 24.8 ma and 14.2 ma, respectively). Inclusion of rTMS and TSCS in the rehabilitation course leads to a significant improvement in the rehabilitation routing scale (by 2 points), Rivermead mobility index (by 5.8 points), statokinetic control functions (balance-Berg by 12 points) and an increase in lower limb muscle strength (flexors by 5.1 points, extensors by 6.2 points).
 CONCLUSION. The use of rTMS and TSCS can be used as an additional effect within the framework of rehabilitation measures in the acute period after ischemic stroke.

Neurorehabilitation of post-stroke patients using a noninvasive spinal neuroprosthesis

Neurorehabilitation of post-stroke patients with motor impairments is a significant and yet unresolved issue in restorative medicine. We propose a novel approach to rehabilitating such patients using transcutaneous electrical spinal cord stimulation (scTS), which targets the neural locomotor networks of the lumbar enlargement of the human spinal cord [1]. The Spinal Neuroprosthesis device was developed to control stimulation, providing noninvasive and phase-dependent activation of motoneuronal pools of flexors and extensors during a certain phase of the stepping cycle, combined with the activation of neuronal locomotor networks [2]. The aim of this study is to assess the efficacy of Spinal Neuroprosthesis in regulating locomotor functions among post-stroke patients with motor disorders. The study is designed to provide an objective evaluation of the medical device’s effectiveness. The study was conducted at the Russian Research Institute of Neurosurgery named after Prof. A.L. Polenov. The study enrolled 20 patients who had been experiencing severe motor disorders of the lower extremities in the form of hemiparesis. The duration of stroke among these patients ranged from 3 to 12 months. They were divided into two groups: control and experimental. The control group underwent sham (scTS-) stimulation during a motor rehabilitation session, while the experimental group received real scTS, establishing the difference between the groups. The rehabilitation program comprised 15 sessions of stimulation to the spinal cord. The treatment protocol comprised an initial evaluation of patients’ neurological and rehabilitation status and an investigation of spatial-temporal and kinematic parameters of walking. Subsequently, patients participated in rehabilitation sessions, which entailed walking on the treadmill and over-ground stepping with scTS. Finally, patients underwent a follow-up examination that included a re-evaluation of their neurological and rehabilitation status, as well as an investigation of spatial-temporal and kinematic parameters of walking. At the beginning of the program, the distance traveled by patients in the control and experimental groups during a six-minute walk test, according to the study results, did not differ significantly. However, following the treatment, patients in the experimental group demonstrated a substantially lengthier distance covered during the 6-minute test than the control group. Both groups of patients in the 10-meter walk test demonstrated an increase in distance walking speed, although the patients in the experimental group had a greater increase in speed compared to those in the control group. These improvements were more pronounced in patients from the experimental group. The results from neurological scales indicated an increase in muscular strength, improvement in balance functions, and an increase in functional independence in both groups. The findings provide evidence that the Spinal Neuroprosthesis effectively regulates stepping movements and restores locomotor function in patients post-stroke. Clinically significant improvements are observed within two weeks of neuroprosthesis use. Additionally, training increases patients’ exercise tolerance while walking, speed of movement, and functional independence.

Consecutive Transcutaneous and Epidural Spinal Cord Neuromodulation to Modify Clinical Complete Paralysis—the Proof of Concept

ObjectiveTo evaluate the effect of transcutaneous (tSCS) and epidural electrical spinal cord stimulation (EES) in facilitating volitional movements, balance, and nonmotor functions, in this observational study, tSCS and EES were consecutively tested in 2 participants with motor complete spinal cord injury (SCI). Participants and MethodsTwo participants (a 48-year-old woman and a 28-year-old man), both classified as motor complete spinal injury, were enrolled in the study. Both participants went through a unified protocol, such as an initial electrophysiological assessment of neural connectivity, consecutive tSCS and EES combined with 8 wks of motor training with electromyography (EMG) and kinematic evaluation. The study was conducted from May 1, 2019, to December 31, 2021. ResultsIn both participants, tSCS reported a minimal improvement in voluntary movements still essential to start tSCS-enabled rehabilitation. Compared with tSCS, following EES showed immediate improvement in voluntary movements, whereas tSCS was more effective in improving balance and posture. Continuous improvement in nonmotor functions was found during tSCS-enabled and then during EES-enabled motor training. ConclusionResults report a significant difference in the effect of tSCS and EES on the recovery of neurologic functions and support consecutive tSCS and EES applications as a potential therapy for SCI. The proposed approach may help in selecting patients with SCI responsive to neuromodulation. It would also help initiate neuromodulation and rehabilitation therapy early, particularly for motor complete SCI with minimal effect from conventional rehabilitation.

ANALYSIS OF BRAIN AND MUSCLE ACTIVITY DURING CONTROL OF BRAIN-SPINE NEUROINTERFACE

A brain-spine neurointerface based on the kinesthetic imagination of foot dorsiflexion with additional activation of foot movement by Biokin robotic device (mechanotherapy), and transcutaneous electrical spinal cord stimulation (TESCS) has been developed. Accuracy of classification of EEG-signals during the neurointerface control was on average 68% and significantly increases with the addition of mechanotherapy and TESCS by 9%. The EMG activity of the tibialis anterior (TA) – the muscle, which performs dorsiflexion of the foot, significantly increased during the instruction to imagine movement compared to that during the instruction to be at rest. The addition of mechanotherapy and TESCS during the neurointerface control has a greater effect not on the increase in TA activity when imagining the movement of the ipsilateral foot, but on the decrease in TA activity at rest. The revealed effects are apparently important for the formation of adequate coordination patterns of control signals from the CNS and of muscle activity during the implementation of movements and can be used in the clinical rehabilitation of motor activity using the cortico-spinal neurointerface.

Effects of Single Noninvasive Spinal Cord Stimulation in Patients with Post-Stroke Motor Disorders

Post-stroke gait disorders are often characterized by abnormal kinematic and kinetic patterns, deviations in spatio-temporal features, altered muscle activation and increased power requirements during walking. The investigation is aimed at determining the possibility of using transcutaneous electrical spinal cord stimulation (scTS) to influence the kinematics of walking in stroke patients with hemiparesis in the early and late recovery periods (1–12 months) after stroke. Continuous and phasic stimulation was used during motor training on a treadmill. For stimulation a spinal neuroprosthesis including a multichannel stimulator for scTS (“Cosima”, Russia) with sensors for determining the phases of walking was used. The biomechanical study of the walking function was carried out with the complex “Stadis” (“Neurosoft”, Russia). The study involved 15 patients (age from 33 to 79 years). We analyzed the parameters of stepping movements when walking on the floor without stimulation before and after training on a treadmill using scTS. A comparative analysis of the kinematics of walking before and after training showed an increase in walking speed, the length of the step cycle, an increase in the range of movements in the hip, knee and ankle joints, in 40% patients the height of the paretic foot lift increased by 1–2 cm. The obtained results show that the training with the use of scTS can be considered as a rehabilitation method for correcting walking after a stroke.

Sagittal Spinal Alignment in People with Chronic Spinal Cord Injury and Normal Individual: A Comparison Study Using 3D Ultrasound Imaging.

The aim of this study was to compare the sagittal spinal alignment of people with chronic spinal cord injury (SCI) with normal individuals and to determine whether transcutaneous electrical spinal cord stimulation (TSCS) could cause a change in the thoracic kyphosis (TK) and lumbar lordosis (LL) to re-establish normal sagittal spinal alignment. A case series study was conducted, wherein twelve individuals with SCI and ten neurologically intact subjects were scanned using 3D ultrasonography. In addition, three people with SCI having complete tetraplegia participated further to receive a 12-week treatment (TSCS with task-specific rehabilitation) after evaluation of sagittal spinal profile. Pre- and post-assessments were conducted to evaluate the differences in sagittal spinal alignment. The results showed that the TK and LL values for a person with SCI in a dependent seated posture were greater than those of normal subjects for: standing (by TK: 6.8° ± 1.6°; LL: 21.2° ± 1.9°), sitting straight (by TK: 10.0° ± 4.0°; LL: 1.7° ± 2.6°), and relaxed sitting (by TK: 3.9° ± 0.3°; LL: 7.7° ± 1.4°), respectively, indicating an increased risk for spinal deformity. In addition, TK decreased by 10.3° ± 2.3° after the TSCS treatment, showing a reversible change. These results suggest that the TSCS treatment could be used to restore normal sagittal spinal alignment for individuals with chronic SCI.

A NEW TECHNOLOGY FOR RECOVERY OF LOCOMOTION IN PATIENTS AFTER A STROKE

Neural networks in the spinal cord can generate the walking pattern and control posture in the absence of supraspinal influences. A technology has been created using transcutaneous electrical spinal cord stimulation (tSCS). During walking, tSCS activated spinal locomotor networks, as well as leg flexor/extensor motor pools in the swing/support phases, respectively. It was suggested that the use of this technology in people with locomotion disorders would improve walking. Patients with hemiparesis were studied 3–11 months after a stroke, the duration of the course was 2 weeks. Patients of the main and control groups received standard therapy and rehabilitation using technology; in the control group, sham tESCS was used. After the course in the main group, in contrast to the control group, minimal clinically significant changes in walking parameters were achieved. The developed technology is an effective means of restoring walking in patients with hemiparesis.

Combined Transcutaneous Electrical Spinal Cord Stimulation and Task-Specific Rehabilitation Improves Trunk and Sitting Functions in People with Chronic Tetraplegia.

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.

A New Technology for Recovery of Locomotion in Patients after a Stroke

Neural networks in the spinal cord can generate the walking pattern and control posture in the absence of supraspinal influences. A technology using transcutaneous electrical spinal cord stimulation (tSCS) was created. During walking, tSCS activated spinal locomotor networks, as well as leg flexor/extensor motor pools in the swing/stance phases, respectively. It was assumed that the use of this technology in subjects with locomotion disorders would improve walking. Patients with hemiparesis were studied 3-11 months after stroke, the duration of the course was 2 weeks. Patients of the main and control groups received standard therapy and rehabilitation using the technology; in the control group, sham tSCS was used. After the course, minimal clinically important differences in walking parameters were achieved in the main group, in contrast to the control group. The developed technology is an effective means of restoring walking in patients with hemiparesis.

Regulation of Human Respiration by Electrical Stimulation.

The review addresses modern methods of electrical stimulation used to regulate the function of external respiration in humans. The methods include abdominal functional stimulation of respiratory muscles, diaphragmatic stimulation, phrenic nerve stimulation, epidural and transcutaneous spinal cord stimulation. The physiological rationale of their application is described along with the examples of their use in clinical practice, including stimulation parameters and electrode placement diagrams for each of the methods. We analyze the effectiveness of each of the methods in patients with respiratory muscle paresis and the features of their use depending on the level of spinal cord injury. Special attention is paid to the method of epidural spinal cord stimulation because this technique is widely used in electrophysiological studies on animal models, providing deeper insight into the spinal levels of the functional control of external respiration. The review substantiates the great potential of using the method of transcutaneous electrical spinal cord stimulation both in fundamental studies of external respiration and in clinical practice.

O106 / #796 FEASIBILITY OF TRANSCUTANEOUS SPINAL CORD STIMULATION COMBINED WITH ROBOTIC-ASSISTED GAIT TRAINING (LOKOMAT) FOR GAIT REHABILITATION FOLLOWING INCOMPLETE SPINAL CORD INJURY. A CASE SERIES STUDY: TRACK 3: RESTORATIVE THERAPIES / NONINVASIVE STIMULATION / NEUROSTIMULATION FOR HEAD AND FACE PAIN

Transcutaneous electrical spinal cord stimulation (tSCS) is a non-invasive technique for neuromodulation with therapeutic potential for motor rehabilitation following spinal cord injury (SCI). The aim of the present study was to analyze the feasibility of a program of 20 sessions of 30-Hz tSCS combined with robotic-assisted gait training in incomplete SCI. The results of the present work partially belong to a randomized clinical trial that is in progress.

Minimal handgrip force is needed for transcutaneous electrical stimulation to improve hand functions of patients with severe spinal cord injury

Spinal cord stimulation enhanced restoration of motor function following spinal cord injury (SCI) in unblinded studies. To determine whether training combined with transcutaneous electrical spinal cord stimulation (tSCS), with or without systemic serotonergic treatment with buspirone (busp), could improve hand function in individuals with severe hand paralysis following SCI, we assessed ten subjects in a double-blind, sham-controlled, crossover study. All treatments—busp, tSCS, and the busp plus tSCS—reduced muscle tone and spasm frequency. Buspirone did not have any discernible impact on grip force or manual dexterity when administered alone or in combination with tSCS. In contrast, grip force, sinusoidal force generation and grip-release rate improved significantly after 6 weeks of tSCS in 5 out of 10 subjects who had residual grip force within the range of 0.1–1.5 N at the baseline evaluation. Improved hand function was sustained in subjects with residual grip force 2–5 months after the tSCS and buspirone treatment. We conclude that tSCS combined with training improves hand strength and manual dexterity in subjects with SCI who have residual grip strength greater than 0.1 N. Buspirone did not significantly improve the hand function nor add to the effect of stimulation.

The Effect of Transcutaneous Electrical Spinal Cord Stimulation on the Functional Activity of Spinal Inhibition in the System of Synergistic Muscles of the Lower Leg in Humans

The Effect of Transcutaneous Electrical Spinal Cord Stimulation on the Functional Activity of Spinal Inhibition in the System of Synergistic Muscles of the Lower Leg in Humans

EEG Monitoring Is Feasible and Reliable during Simultaneous Transcutaneous Electrical Spinal Cord Stimulation.

Transcutaneous electrical spinal cord stimulation (tSCS) is a non-invasive neuromodulatory technique that has in recent years been linked to improved volitional limb control in spinal-cord injured individuals. Although the technique is growing in popularity there is still uncertainty regarding the neural mechanisms underpinning sensory and motor recovery. Brain monitoring techniques such as electroencephalography (EEG) may provide further insights to the changes in coritcospinal excitability that have already been demonstrated using other techniques. It is unknown, however, whether intelligible EEG can be extracted while tSCS is being applied, owing to substantial high-amplitude artifacts associated with stimulation-based therapies. Here, for the first time, we characterise the artifacts that manifest in EEG when recorded simultaneously with tSCS. We recorded multi-channel EEG from 21 healthy volunteers as they took part in a resting state and movement task across two sessions: One with tSCS delivered to the cervical region of the neck, and one without tSCS. An offline analysis in the time and frequency domain showed that tSCS manifested as narrow, high-amplitude peaks with a spectral density contained at the stimulation frequency. We quantified the altered signals with descriptive statistics—kurtosis, root-mean-square, complexity, and zero crossings—and applied artifact-suppression techniques—superposition of moving averages, adaptive, median, and notch filtering—to explore whether the effects of tSCS could be suppressed. We found that the superposition of moving averages filter was the most successful technique at returning contaminated EEG to levels statistically similar to that of normal EEG. In the frequency domain, however, notch filtering was more effective at reducing the spectral power contribution of stimulation from frontal and central electrodes. An adaptive filter was more appropriate for channels closer to the stimulation site. Lastly, we found that tSCS posed no detriment the binary classification of upper-limb movements from sensorimotor rhythms, and that adaptive filtering resulted in poorer classification performance. Overall, we showed that, depending on the analysis, EEG monitoring during transcutaneous electrical spinal cord stimulation is feasible. This study supports future investigations using EEG to study the activity of the sensorimotor cortex during tSCS, and potentially paves the way to brain–computer interfaces operating in the presence of spinal stimulation.

Functional Neurorehabilitation in Dogs with an Incomplete Recovery 3 Months following Intervertebral Disc Surgery: A Case Series

Simple SummaryA non-invasive neurorehabilitation multimodal protocol (NRMP) may be applicable to chronic T3-L3 dogs 3 months after undergoing surgery for acute Intervertebral Disc Disease (IVDD) Hansen type I; this protocol has been shown to be safe, feasible, and potentially effective at improving ambulation in both open field score (OFS) 0 and OFS 1 dogs. The specific sample population criteria limit the number of dogs included, mainly due to owners withdrawing over time. Thus, the present case series study aimed to demonstrate that an NRMP could contribute to a functional treatment possibly based on synaptic and anatomic reorganization of the spinal cord.This case series study aimed to evaluate the safety, feasibility, and positive outcome of the neurorehabilitation multimodal protocol (NRMP) in 16 chronic post-surgical IVDD Hansen type I dogs, with OFS 0/DPP− (n = 9) and OFS 1/DPP+ (n = 7). All were enrolled in the NRMP for a maximum of 90 days and were clinically discharged after achieving ambulation. The NRMP was based on locomotor training, functional electrical stimulation, transcutaneous electrical spinal cord stimulation, and 4-aminopyridine (4-AP) pharmacological management. In the Deep Pain Perception (DPP)+ dogs, 100% recovered ambulation within a mean period of 47 days, reaching OFS ≥11, which suggests that a longer period of time is needed for recovery. At follow-up, all dogs presented a positive evolution with voluntary micturition. Of the DPP− dogs admitted, all achieved a flexion/extension locomotor pattern within 30 days, and after starting the 4-AP, two dogs were discharged at outcome day 45, with 78% obtaining Spinal Reflex Locomotion (SRL) and automatic micturition within a mean period of 62 days. At follow-up, all dogs maintained their neurological status. After the NRMP, ambulatory status was achieved in 88% (14/16) of dogs, without concurrent events. Thus, an NRMP may be an important therapeutic option to reduce the need for euthanasia in the clinical setting.

Effects of Phase Shifts of Transcutaneous Electrical Spinal Cord Stimulation on the Kinematic Characteristics of Stepping Movements in Humans

Effects of Phase Shifts of Transcutaneous Electrical Spinal Cord Stimulation on the Kinematic Characteristics of Stepping Movements in Humans

Transcutaneous Electrical Spinal Cord Stimulation to Promote Recovery in Chronic Spinal Cord Injury.

Objective:To evaluate the impact of using transcutaneous electrical spinal cord stimulation (TSCS) on upper and lower extremity function in individuals with chronic spinal cord injury (SCI).Design:Prospective case series.Setting:SCI specific rehabilitation hospital.Participants:A convenience sample (N = 7) of individuals with tetraplegia who had previously been discharged from outpatient therapy due to a plateau in progress.Interventions:Individuals participated in 60 min of upper extremity (UE) functional task-specific practice (FTP) in combination with TSCS and 60 min of locomotor training in combination with TSCS 5x/week.Main Outcome Measures:The primary outcome for this analysis was the Capabilities of Upper Extremity Test (CUE-T). Secondary outcomes include UE motor score (UEMS), LE motor score (LEMS), sensation (light touch and pin prick), Nine-Hole Peg Test, 10 meter walk test, 6 min walk test, and 5 min stand test.Results:Seven individuals (four motor complete; three motor incomplete) completed 20–80 sessions UE and LE training augmented with TSCS and without any serious adverse events. Improvements were reported on the CUE-T in all seven individuals. Two individuals improved their ASIA impairment scale (AIS) classification (B to C; C to D) and two individuals improved their neurologic level of injury by one level (C4–C5; C5–C6). Sensation improved in five individuals and all four who started out with motor complete SCIs were able to voluntarily activate their LEs on command in the presence of stimulation.Conclusion:Individuals with chronic SCI who had previously demonstrated a plateau in function after an intensive outpatient therapy program were able to improve in a variety of UE and LE outcomes in response to TSCS without any adverse events. This was a small pilot study and future fully powered studies with comparative interventions need to be completed to assess efficacy.

Immediate Effects of Transcutaneous Spinal Cord Stimulation on Motor Function in Chronic, Sensorimotor Incomplete Spinal Cord Injury.

Deficient ankle control after incomplete spinal cord injury (iSCI) often accentuates walking impairments. Transcutaneous electrical spinal cord stimulation (tSCS) has been shown to augment locomotor activity after iSCI, presumably due to modulation of spinal excitability. However, the effects of possible excitability modulations induced by tSCS on ankle control have not yet been assessed. This study investigated the immediate (i.e., without training) effects during single-sessions of tonic tSCS on ankle control, spinal excitability, and locomotion in ten individuals with chronic, sensorimotor iSCI (American Spinal Injury Association Impairment Scale D). Participants performed rhythmic ankle movements (dorsi- and plantar flexion) at a given rate, and irregular ankle movements following a predetermined trajectory with and without tonic tSCS at 15 Hz, 30 Hz, and 50 Hz. In a subgroup of eight participants, the effects of tSCS on assisted over-ground walking were studied. Furthermore, the activity of a polysynaptic spinal reflex, associated with spinal locomotor networks, was investigated to study the effect of the stimulation on the dedicated spinal circuitry associated with locomotor function. Tonic tSCS at 30 Hz immediately improved maximum dorsiflexion by +4.6° ± 0.9° in the more affected lower limb during the rhythmic ankle movement task, resulting in an increase of +2.9° ± 0.9° in active range of motion. Coordination of ankle movements, assessed by the ability to perform rhythmic ankle movements at a given target rate and to perform irregular movements according to a trajectory, was unchanged during stimulation. tSCS at 30 Hz modulated spinal reflex activity, reflected by a significant suppression of pathological activity specific to SCI in the assessed polysynaptic spinal reflex. During walking, there was no statistical group effect of tSCS. In the subgroup of eight assessed participants, the three with the lowest as well as the one with the highest walking function scores showed positive stimulation effects, including increased maximum walking speed, or more continuous and faster stepping at a self-selected speed. Future studies need to investigate if multiple applications and individual optimization of the stimulation parameters can increase the effects of tSCS, and if the technique can improve the outcome of locomotor rehabilitation after iSCI.

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

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.