Multisegmental transcutaneous electrical stimulation of the spinal cord (sсTS), affecting spinal neural networks and motor pools of leg muscles, was used to correct treadmill walking in stroke patients. The study involved 15 patients in the recovery period after acute cerebrovascular accidents. A noninvasive spinal neuroprosthesis with a multichannel stimulator and a system for detecting phases of the walking cycle (“Cosima”, Russia) was used to activate motor pools of leg flexor muscles in the transfer phase, activation of motor pools of extensor muscles in the stance phase in combination with continuous activation of spinal locomotor networks. Using of sсTS during walking on a treadmill increased the amplitude of movements in the ankle joint and the stride length on the paresis side, as well as a decreased the asymmetry of both legs in the phases of the gait cycle. The clearance of the paretic leg lift increased in 80 of patients. With a combination of continuous and phase-dependent stimulation, the increase in the range of motion in the joints was maximal compared to phase-dependent or only constant stimulation. The obtained data demonstrate that the proposed algorithm of the sсTS modulates the parameters of walking movements in patients with the consequences of cerebral circulation accidents and can be considered as a promising method of motor rehabilitation.

An Erratum to this paper has been published: https://doi.org/10.1134/S0362119723970029

Исследовалось влияние чрескожной электрической стимуляции спинного мозга на кинематические параметры движений ипсилатеральной и контралатеральной ноги у здоровых испытуемых при ходьбе по беговой дорожке (1.5-1.7 км/ч). Стимулирующие электроды располагались на 2.5 см латеральнее средней линии спинного мозга с правой и левой стороны на уровне L1 и T11 позвонков. Во время фазы опоры применяли стимуляцию на уровне L1 с частотой 15 Гц, затем во время фазы переноса - на уровне T11 с частотой 30 Гц, далее следовала чередующаяся стимуляция L1 и T11. Влияние стимуляции в фазе переноса (T11) было более эффективным, чем в фазе опоры (L1), а наибольшее изменение кинематических параметров наблюдалось при сочетании стимуляции L1 и T11. При ритмической стимуляции с одной стороны в шаге ипсилатеральной ноги увеличивалась амплитуда изменения углов в тазобедренном, коленном и/или голеностопном суставах, длина переноса и высота подъема ноги. В шаге контралатеральной ноги наблюдались схожие, но менее выраженные изменения параметров. Увеличение продолжительности стимуляции в фазе переноса на 10% вызывало изменения кинематических параметров шага ипси- и контралатеральной ноги. Максимальный эффект наблюдался при двусторонней чередующейся стимуляции. Полученные данные показывают, что применение фазозависимой чрескожной электрической стимуляции спинного мозга с учетом естественной синергии может быть инструментом управления кинематическими параметрами движения.

The effect of noninvasive trasnscutaneous spinal cord stimulation (scTS) on walking parameters in patients after a cerebral infarction or ischemic stroke was investigated. It has been shown that after the use of scTS while walking on the floor the speed of movement, the length of the step cycle, the height of the foot elevation and the amplitude of movements in the hip, knee and ankle joints increased, which shows the ability of using scT to correct walking after a stroke. Key words: spinal cord, electrical stimulation, stroke, walking.

The effect of transcutaneous electrical spinal cord stimulation on the kinematic parameters of movement of the ipsilateral and contralateral legs in healthy subjects during treadmill walking at speeds of 1.5 to 1.7 km/h has been studied. The stimulation electrodes were placed 2.5 cm lateral from the right and left sides of the spinal midline at L1 and T11 levels. During the stance phase, stimulation was administered at L1 level at a frequency of 15 Hz; during the swing phase the stimuli was delivered to T11 at a frequency of 30 Hz, followed by alternating stimulation at L1 and T11. The stimulation during the swing phase (T11) was more effective than that during the stance phase (L1); the most impressive changes in kinematic parameters were observed when combined delivery of stimulations to L1 and T11 was performed. With unilateral spinal stimulation, the amplitude of the angles in the hip, knee and/or ankle joints, the length of the transfer, and the height of the leg elevation increased in the ipsilateral leg. Similar but less pronounced changes were observed in the contralateral leg. A 10% increase in the duration of stimulation in the swing phase caused a change in the kinematic stepping parameters both in ipsilateral and contralateral legs. The maximum effect was observed when bilateral alternating stimulation was used. These data show that phasic transcutaneous electrical spinal cord stimulation, using a wide range of natural walking speeds, can be applied to control kinematic movement parameters.

Transcutaneous electrical spinal cord stimulation (SсТS) wascarried out in different phases of the stepping cycle in order tocontrol the kinematic parameters of the step in healthy subjects walkingon a treadmill. ScTS during the swing phase at the T11–T12 levelactivated the flexor motor pools and caused a change in the motionamplitude in the hip, knee and ankle joints, as well as increasedthe height of leg elevation. ScTS at the stance phase at the L1–L2level, addressed to the extensor motor pools, did not affect thekinematics of stepping movements. A shift in the start of T11–T12stimulation to 100–150 ms before the initiation of the swing phaseor its prolongation by 100 ms after the end of the swing phase causedsignificant changes in the kinematics of stepping movements. Essentialfor the start of stimulation is the moment of pushing the leg offthe support a little earlier than beginning of the swing phase .Prolongation of the stimulation period in the swing phase allowsto increase ankle join flexion The choice of the optimal algorithmof phase-dependent ScTS for the activation of flexor and extensormotor pools during the stepping cycle increases the efficiency ofstimulation in motor function rehabilitation techniques.

Transcutaneous electrical stimulation of the spinal cord (ScTS) was carried out in different phases of the stepping cycle in order to control the kinematic parameters of the step in healthy subjects walking on a treadmill. ScTS at the T11-T12 level during swing phase activated the flexor motor pools and caused change of the motion amplitude in hip, knee, and ankle joints as well as increased the height of the leg elevation. Stimulation at the L1-L2 level at the stance phase, addressed to the extensor motor pools, did not affect the kinematics of stepping movements. Shift in the beginning of T11-T12 stimulation to 100-150 ms before the initiation of the swing phase or its prolongation by 100 ms after the end of it caused significant changes in the kinematics of the movements. Essential for the start of stimulation is the moment of pushing the foot off the support a little earlier the transfer phase. Prolongation the stimulation period in transfer phase allows to increase ankle joint flexion. The choice of the optimal algorithm of the phase-dependent ScTS for activation of the flexor and extensor motor pools during the stepping cycle increases the efficiency of stimulation in motor functions rehabilitation techniques.

We have studied the reaction of the respiratory system to transcutaneous spinal cord stimulation inducing stepping movements of large and small amplitudes. We have shown that the small amplitude of the generated stepping movements was associated with a reduction of the tidal volume, and generated movements with a large amplitude resulted in the elevation of the expiratory flow. We have compared the reactions of the respiratory system during stepping movements induced by spinal cord stimulation and by voluntary efforts. It has been found that, during stepping movements induced by the spinal cord stimulation, lung ventilation increased through reduction of the inspiration and expiration times, while the expiratory flow increased. During voluntary stepping movements, the inspiration time decreased, while the inspiratory and expiratory flows increased. These effects can ensue from tonic activation of abdominal muscles, as well as from the summation of the effects of spinal stimulation and working hyperpnoea.

The effects of transcutaneous electrical stimulation of the spinal cord on the kinematic and electromyographic characteristics of motor responses in the arms and legs muscles in healthy subjects have been studied. The subjects placed in the biomechanical simulator in a supine position and performed voluntary rhythmic leg movements displacing the carriage of the simulator's walking device, voluntary arm movements, moving the simulator levers or performed simultaneous arm and leg movements. During the rest, the sequential stimulation at the level of Th12-L1, L1-L2 and C5-C6 vertebrae did not elicit leg movements in most subjects, however, the arm movements in combination with stimulation of the spinal cord initiated fluctuations in the joints of the legs (amplitude up to 10 angle degrees). The stimulation in combination with arm movements facilitated voluntary leg movements and increased the integral characteristic of electromyographic activity. The most pronounced changes in the amplitude of movements of the hip joint were revealed. Effects of multisegmental spinal cord stimulation in regulation of interlimb synergy were examined. The results can be used to develop the approach for neurorehabilitation of patients with impaired motor functions.

Effects of transcutaneous electrical spinal cord stimulation (tESCS) on the parameters of stepping movements in healthy subjects were investigated during two kinds of activity: walking on a moving treadmill belt (active treadmill) as well as pushing the treadmill belt by effort of the legs (passive treadmill). It was found that the total interference electromyogram (EMG) activity during stepping performance on a passive treadmill was 1.5–2 times higher than during stepping on an active treadmill. In addition, the amplitude of angular displacement of the hip joint and ankle was 2.5 times and 1.7 times higher, respectively, during passive vs. active treadmill, while the duration of stepping cycle decreased by 19%. Although the muscles were exposed to different load and the parameters of motion on the active and passive treadmill were different, tESCS caused an increase in the total EMG activity in 96% of cases both on the active and on the passive treadmill. In both cases, the stepping cycle period decreased by 4–43% in all subjects. These results suggest that tESCS can affect voluntary stepping patterns under conditions of different afferent control.

Changes in the blood flow in the skin of the plantar surface of the hallux were investigated by laser Doppler flowmetry in eight healthy subjects during transcutaneous electrical spinal cord stimulation (tESCS) with the pulse parameters used to activate locomotion. Continuous tESCS in the area of C5–C6 vertebrae did not cause significant changes in the blood flow, while electrical stimulation at T 12 – T 1 and L 1 – L 2 levels resulted in an increase in skin perfusion by 22–27%. Wavelet analysis of microcirculatory fluctuations showed that tESCS induced flaxomotions in the range of sensory peptidergic fibers and enhanced the amplitude of fluctuations of microcirculation in the endothelium-dependent range. These results suggest that tESCS stimulates microcirculation in the skin mainly due to antidromic stimulation of sensory peptidergic nerve fibers, which promotes activity of microvascular endothelium, vasodilator secretion, a decrease in vascular resistance, and an increase in microcirculation.

Cerebral palsy (CP) considerably impairs the ability to maintain upright stance. The effects of locomotor training and functional electrical stimulation (FES) on postural control were determined in 27 children aged 6–12 years with severe CP. The severity level of the clinical manifestations of CP was classified as 3 according to the Gross Motor Function Classification System (GMFCS). All patients participated in 15 30-min mechanical therapy sessions using robot-assisted passive stepping. In 12 out of 27 children, the locomotion therapy was accompanied by FES. Stabilometry and plantography tests were performed in 23 healthy age-matched children. Postural control in children with CP differed from the stabilograms of healthy children in a forward shift of the center of pressure (COP) projection; higher values of the COP trajectory area and length, the mean amplitude of the COP oscillations, and the absence of COP response to the eyes closed condition. After treatment, the posturographic characteristics tended to normalize in relation to the values obtained in neurologically intact children. The improvement was observed in 43% of children without FES and in 75% of children in the group with FES. Analysis of plantograms revealed normalization of footprints in children who received FES. Thus, it was demonstrated that FES combined with locomotor training resulted in the improvement in vertical posture control in children with severe CP.

The mechanism of interactions between receptor activation in the musculoskeletal system and stimulation of the spinal cord in the regulation of locomotor behavior was studied in healthy subjects. Afferent stimulation was tested for effect on the patterns of stepping movements induced by percutaneous stimulation of the spinal cord. A combination of percutaneous spinal cord stimulation and vibratory stimulation was shown to increase the amplitude of leg movements. It was demonstrated that vibratory stimulation of limb muscles at a frequency of less than 30 Hz can be used to control involuntary movements elicited by noninvasive stimulation of the spinal cord.

It was shown that the epidural and the electromagnetic tonic stimulation with frequency 5 Hz applied to the lumbal as well as to the cervical region of the spinal cord enabled stepping on a moving treadmill belt in decerebrated cats. It was found that there were differences in initiation of the stepping movements during epidural and electromagnetic stimulation depending on the region of spinal cord stimulation. Stimulation at frequency of 0.3 Hz induced single reflex responses in the anterior and posterior limbs. On the basis of analysis of the response structure it was concluded that the locomotor ability during epidural and electromagnetic stimulation depended on the degree of polysynaptic pathways activation. The hypothesis about stepping pattern generator activation through the dorsal roots during epidural stimulation and more direct activation of neuronal locomotor networks in the case of electromagnetic spinal cord stimulation is discussed.

A new tool for locomotor circuitry activation in the non-injured human by transcutaneous electrical spinal cord stimulation (tSCS) has been described. We show that continuous tSCS over T11-T12 vertebrae at 5-40 Hz induced involuntary locomotor-like stepping movements in subjects with their legs in a gravity-independent position. The increase of frequency of tSCS from 5 to 30 Hz augmented the amplitude of evoked stepping movements. The duration of cycle period did not depend on frequency of tSCS. During tSCS the hip, knee and ankle joints were involved in the stepping performance. It has been suggested that tSCS activates the locomotor circuitry through the dorsal roots. It appears that tSCS can be used as a non-invasive method in rehabilitation of spinal pathology.