Chronic neuromuscular electrical stimulation of paralyzed hindlimbs in a rodent model

Effect of High-Intensity Focused Electromagnetic Technology in the Treatment of Female Stress Urinary Incontinence

Background: The aim of the study was to assess the effect of high-intensity focused electromagnetic (HIFEM) technology in the treatment of female stress urinary incontinence (SUI). Materials and Methods: 20 women with SUI were delivered a treatment course with HIFEM technology. Patients attended 6 therapies scheduled twice a week. Validated questionnaires were assessed, including the overactive bladder symptoms score (OABSS), urogenital distress inventory-6 (UDI-6), incontinence impact questionnaire-7 (IIQ-7), international consultation on incontinence questionnaire (ICIQ), and valued living questionnaire (VLQ). Some urodynamic parameters, such as maximum flow rate (Qmax), residual urine (RU), and bladder volume at first sensation to void (Vfst). Bladder neck mobility in ultrasound topography was also collected pre- and post-treatment at 1- and 6-month follow-up visits. Results: HIFEM treatment significantly improved SUI symptoms on pad tests from 4.2 ± 5.5 to 0.6 ± 1.3 and patients' self-assessment in the 6-month follow-up. Additionally, the data from urinary-related questionnaires, including OABSS (5.3 ± 3.9 to 3.9 ± 3.6), UDI-6 (35.7 ± 22.3 to 15.2 ± 10.6), IIQ-7 (33.1 ± 28.7 to 14.3 ± 17.2), and ICIQ (9.4 ± 5.0 to 5.4 ± 3.6), all showed a significant reduction. Then, the analysis of the urodynamic study revealed that only maximum urethral closure pressure (MUCP) (46.4 ± 25.2 to 58.1 ± 21.2) and urethral closure angle (UCA) (705.3 ± 302.3 to 990.0 ± 439.6) significantly increased after the six sessions of HIFEM treatment. The urethral and vaginal topography were performed and found that HIFEM mainly worked on pelvic floor muscles (PFM) and enhanced their function and integrity. Conclusions: The results suggest that HIFEM technology is an efficacious therapy for the treatment of SUI.

An Open-Source 3D-Printed Hindlimb Stabilization Apparatus for Reliable Measurement of Stimulation-Evoked Ankle Flexion in Rat

Currently there are numerous methods to evaluate peripheral nerve stimulation interfaces in rats, with stimulation-evoked ankle torque being one of the most prominent. Commercial rat ankle torque measurement systems and custom one-off solutions have been published in the literature. However, commercial systems are proprietary and costly and do not allow for customization. One-off lab-built systems have required specialized machining expertise, and building plans have previously not been made easily accessible. Here, detailed building plans are provided for a low-cost, open-source, and basic ankle torque measurement system from which additional customization can be made. A hindlimb stabilization apparatus was developed to secure and stabilize a rat's hindlimb, while allowing for simultaneous ankle-isometric torque and lower limb muscle electromyography (EMG). The design was composed mainly of adjustable 3D-printed components to accommodate anatomical differences between rat hindlimbs. Additionally, construction and calibration procedures of the rat hindlimb stabilization apparatus were demonstrated in this study. In vivo torque measurements were reliably acquired and corresponded to increasing stimulation amplitudes. Furthermore, implanted leads used for intramuscular EMG recordings complemented torque measurements and were used as an additional functional measurement in evaluating the performance of a peripheral nerve stimulation interface. In conclusion, an open-source and noninvasive platform, made primarily with 3D-printed components, was constructed for reliable data acquisition of evoked motor activity in rat models. The purpose of this apparatus is to provide researchers a versatile system with adjustable components that can be tailored to meet user-defined experimental requirements when evaluating motor function of the rat hindlimbs.

Fully implanted battery-free high power platform for chronic spinal and muscular functional electrical stimulation

Electrical stimulation of the neuromuscular system holds promise for both scientific and therapeutic biomedical applications. Supplying and maintaining the power necessary to drive stimulation chronically is a fundamental challenge in these applications, especially when high voltages or currents are required. Wireless systems, in which energy is supplied through near field power transfer, could eliminate complications caused by battery packs or external connections, but currently do not provide the harvested power and voltages required for applications such as muscle stimulation. Here, we introduce a passive resonator optimized power transfer design that overcomes these limitations, enabling voltage compliances of ± 20 V and power over 300 mW at device volumes of 0.2 cm2, thereby improving power transfer 500% over previous systems. We show that this improved performance enables multichannel, biphasic, current-controlled operation at clinically relevant voltage and current ranges with digital control and telemetry in freely behaving animals. Preliminary chronic results indicate that implanted devices remain operational over 6 weeks in both intact and spinal cord injured rats and are capable of producing fine control of spinal and muscle stimulation.

Optimal conditions for graft survival and reinnervation of denervated muscles after embryonic motoneuron transplantation into peripheral nerves undergoing Wallerian degeneration

Motoneuron transplantation into peripheral nerves undergoing Wallerian degeneration may have applications in treating diseases causing muscle paralysis. We investigated whether functional reinnervation of denervated muscle could be achieved by early or delayed transplantation after denervation. Adult rats were assigned to six groups with increasing denervation periods (0, 1, 4, 8, 12, and 24 weeks) before inoculation with culture medium containing (transplantation group) or lacking (surgical control group) dissociated embryonic motoneurons into the peroneal nerve. Electrophysiological and tissue analyses were performed 3 months after transplantation. Reinnervation of denervated muscles significantly increased relative muscle weight in the transplantation group compared with the surgical control group for denervation periods of 1 week (0.042% ± 0.0031% vs. 0.032% ± 0.0020%, respectively; p = 0.009), 4 weeks (0.044% ± 0.0069% vs. 0.026% ± 0.0045%, respectively; p = 0.0023), and 8 weeks (0.044% ± 0.0029% vs. 0.026% ± 0.0008%, respectively; p = 0.0023). The ratios of reinnervated muscle contractile forces to naïve muscle in the 0, 1, 4, 8, and 12 weeks transplantation groups were 3.79%, 18.99%, 8.05%, 6.30%, and 5.80%, respectively, indicating that these forces were sufficient for walking. The optimal implantation time for transplantation of motoneurons into the peripheral nerve was 1 week after nerve transection. However, the neurons transplanted 24 weeks after denervation survived and regenerated axons. These results indicated that there is time for preparing cells for transplantation in regenerative medicine and suggested that our method may be useful for paralysed muscles that are not expected to recover with current treatment.

Restoring Ventilatory Control Using an Adaptive Bioelectronic System

Ventilatory pacing by electrical stimulation of the phrenic nerve or of the diaphragm has been shown to enhance quality of life compared to mechanical ventilation. However, commercially available ventilatory pacing devices require initial manual specification of stimulation parameters and frequent adjustment to achieve and maintain suitable ventilation over long periods of time. Here, we have developed an adaptive, closed-loop, neuromorphic, pattern-shaping controller capable of automatically determining a suitable stimulation pattern and adapting it to maintain a desired breath-volume profile on a breath-by-breath basis. The system adapts the pattern of stimulation parameters based on the error between the measured volume sampled every 40 ms and a desired breath volume profile. In vivo studies in anesthetized male Sprague-Dawley rats without and with spinal cord injury by spinal hemisection at C2 indicated that the controller was capable of automatically adapting stimulation parameters to attain a desired volume profile. Despite diaphragm hemiparesis, the controller was able to achieve a desired volume in the injured animals that did not differ from the tidal volume observed before injury (p = 0.39). Closed-loop adaptive pacing partially mitigated hypoventilation as indicated by reduction of end-tidal CO₂ values during pacing. The closed-loop controller was developed and parametrized in a computational testbed before in vivo assessment. This bioelectronic technology could serve as an individualized and autonomous respiratory pacing approach for support or recovery from ventilatory deficiency.

The efficacy of neuromuscular electrical stimulation with alternating currents in the kilohertz frequency to stimulate gait rhythm in rats following spinal cord injury

Background

Rehabilitation facilitates the reorganization of residual/regenerated neural pathways and is key in improving motor function following spinal cord injury. Neuromuscular electrical stimulation (NMES) has been reported as being clinically effective. Although it can be used after the acute phase post-injury, the optimal stimulation conditions to improve motor function remain unclear. In this paper, we examined the effectiveness of NMES with alternating currents in the kilohertz (kHz) frequency in gait rhythm stimulation therapy.

Methods

Tests were performed using 20 mature female Fischer rats. Incomplete spinal cord injuries (T9 level) were made with an IH impactor using a force of 150 kdyn, and NMES was administered for 3 days from the 7th day post-injury. The needle electrodes were inserted percutaneously near the motor point of each muscle in conscious rats, and each muscle on the left and right leg was stimulated for 15 min at two frequencies, 75 Hz and 8 kHz, to induce a gait rhythm. Motor function was evaluated using Basso, Beattie, Bresnahan (BBB) scores and three-dimensional (3D) gait analysis. Rats were divided into four groups (5 rats/group), including the NMES treatment 75-Hz group (iSCI-NMES 75 Hz), 8-kHz group (iSCI-NMES 8 kHz), injury control group (iSCI-NT), and normal group (Normal-CT), and were compared.

Results

There was no significant difference in BBB scores among the three groups. In 3D gait analysis, compared with the injury control group, the 8-kHz group showed a significant improvement in synergistic movement of both hindlimbs.

Conclusion

We suggest that kHz stimulation is effective in gait rhythm stimulation using NMES.

Electrical stimulation of transplanted motoneurons improves motor unit formation

Motoneurons die following spinal cord trauma and with neurological disease. Intact axons reinnervate nearby muscle fibers to compensate for the death of motoneurons, but when an entire motoneuron pool dies, there is complete denervation. To reduce denervation atrophy, we have reinnervated muscles in Fisher rats from local transplants of embryonic motoneurons in peripheral nerve. Since growth of axons from embryonic neurons is activity dependent, our aim was to test whether brief electrical stimulation of the neurons immediately after transplantation altered motor unit numbers and muscle properties 10 wk later. All surgical procedures and recordings were done in anesthetized animals. The muscle consequences of motoneuron death were mimicked by unilateral sciatic nerve section. One week later, 200,000 embryonic day 14 and 15 ventral spinal cord cells, purified for motoneurons, were injected into the tibial nerve 10-15 mm from the gastrocnemii muscles as the only neuron source for muscle reinnervation. The cells were stimulated immediately after transplantation for up to 1 h using protocols designed to examine differential effects due to pulse number, stimulation frequency, pattern, and duration. Electrical stimulation that included short rests and lasted for 1 h resulted in higher motor unit counts. Muscles with higher motor unit counts had more reinnervated fibers and were stronger. Denervated muscles had to be stimulated directly to evoke contractions. These results show that brief electrical stimulation of embryonic neurons, in vivo, has long-term effects on motor unit formation and muscle force. This muscle reinnervation provides the opportunity to use patterned electrical stimulation to produce functional movements.

Functional electrical stimulation post-spinal cord injury improves locomotion and increases afferent input into the central nervous system in rats

BACKGROUND

Functional electrical stimulation (FES) has been found to be effective in restoring voluntary functions after spinal cord injury (SCI) and stroke. However, the central nervous system (CNS) changes that occur in as a result of this therapy are largely unknown.

OBJECTIVE

To examine the effects of FES on the restoration of voluntary locomotor function of the CNS in a SCI rat model.

METHODS

SCI rats were instrumented with chronic FES electrodes in the hindlimb muscles and were divided into two groups: (a) FES therapy and (b) sedentary. At day 7 post-SCI, the animals were assessed for locomotion performance by using a Basso, Beattie and Bresnahan (BBB) scale. They were then anesthetized for a terminal in vivo experiment. The lumbar spinal cord and somatosensory cortex were exposed and the instrumented muscles were stimulated electrically. Associated neurovascular responses in the CNS were recorded with an intrinsic optical imaging system.

RESULTS

FES greatly improved locomotion recovery by day 7 post-SCI, as measured by BBB scores (P < 0.05): (a) FES 10 ± 2 and (b) controls 3 ± 1. Furthermore, the FES group showed a significant increase (P < 0.05) of neurovascular activation in the spinal cord and somatosensory cortex when the muscles were stimulated between 1 and 3 motor threshold (MT).

CONCLUSION

Hind limb rehabilitation with FES is an effective strategy to improve locomotion during the acute phase post-SCI. The results of this study indicate that after FES, the CNS preserves/acquires the capacity to respond to peripheral electrical stimulation.

Joint-specific changes in locomotor complexity in the absence of muscle atrophy following incomplete spinal cord injury

Background

Following incomplete spinal cord injury (iSCI), descending drive is impaired, possibly leading to a decrease in the complexity of gait. To test the hypothesis that iSCI impairs gait coordination and decreases locomotor complexity, we collected 3D joint angle kinematics and muscle parameters of rats with a sham or an incomplete spinal cord injury.

Methods

12 adult, female, Long-Evans rats, 6 sham and 6 mild-moderate T8 iSCI, were tested 4 weeks following injury. The Basso Beattie Bresnahan locomotor score was used to verify injury severity. Animals had reflective markers placed on the bony prominences of their limb joints and were filmed in 3D while walking on a treadmill. Joint angles and segment motion were analyzed quantitatively, and complexity of joint angle trajectory and overall gait were calculated using permutation entropy and principal component analysis, respectively. Following treadmill testing, the animals were euthanized and hindlimb muscles removed. Excised muscles were tested for mass, density, fiber length, pennation angle, and relaxed sarcomere length.

Results

Muscle parameters were similar between groups with no evidence of muscle atrophy. The animals showed overextension of the ankle, which was compensated for by a decreased range of motion at the knee. Left-right coordination was altered, leading to left and right knee movements that are entirely out of phase, with one joint moving while the other is stationary. Movement patterns remained symmetric. Permutation entropy measures indicated changes in complexity on a joint specific basis, with the largest changes at the ankle. No significant difference was seen using principal component analysis. Rats were able to achieve stable weight bearing locomotion at reasonable speeds on the treadmill despite these deficiencies.

Conclusions

Decrease in supraspinal control following iSCI causes a loss of complexity of ankle kinematics. This loss can be entirely due to loss of supraspinal control in the absence of muscle atrophy and may be quantified using permutation entropy. Joint-specific differences in kinematic complexity may be attributed to different sources of motor control. This work indicates the importance of the ankle for rehabilitation interventions following spinal cord injury.

FES control of isometric forces in the rat hindlimb using many muscles

Functional electrical stimulation (FES) attempts to restore motor behaviors to paralyzed limbs by electrically stimulating nerves and/or muscles. This restoration of behavior requires specifying commands to a large number of muscles, each making an independent contribution to the ongoing behavior. Efforts to develop FES systems in humans have generally been limited to preprogrammed, fixed muscle activation patterns. The development and evaluation of more sophisticated FES control strategies is difficult to accomplish in humans, mainly because of the limited access of patients for FES experiments. Here, we developed an in vivo FES test platform using a rat model that is capable of using many muscles for control and that can therefore be used to evaluate potential strategies for developing flexible FES control strategies. We first validated this FES test platform by showing consistent force responses to repeated stimulation, monotonically increasing muscle recruitment with constant force directions, and linear summation of costimulated muscles. These results demonstrate that we are able to differentially control the activation of many muscles, despite the small size of the rat hindlimb. We then demonstrate the utility of this platform to test potential FES control strategies, using it to test our ability to effectively produce open-loop control of isometric forces. We show that we are able to use this preparation to produce a range of endpoint forces flexibly and with good accuracy. We suggest that this platform will aid in FES controller design, development, and evaluation, thus accelerating the development of effective FES applications for the restoration of movement in paralyzed patients.

Development of less invasive neuromuscular electrical stimulation model for motor therapy in rodents

BACKGROUND

Combination therapy is essential for functional repairs of the spinal cord. Rehabilitative therapy can be considered as the key for reorganizing the nervous system after spinal cord regeneration therapy. Functional electrical stimulation has been used as a neuroprosthesis in quadriplegia and can be used for providing rehabilitative therapy to tap the capability for central nervous system reorganization after spinal cord regeneration therapy.

OBJECTIVE

To develop a less invasive muscular electrical stimulation model capable of being combined with spinal cord regeneration therapy especially for motor therapy in the acute stage after spinal cord injury.

METHODS

The tibialis anterior and gastrocnemius motor points were identified in intact anesthetized adult female Fischer rats, and stimulation needle electrodes were percutaneously inserted into these points. Threshold currents for visual twitches were obtained upon stimulation using pulses of 75 or 8 kHz for 200 ms. Biphasic pulse widths of 20, 40, 80, 100, 300, and 500 µs per phase were used to determine strength-duration curves. Using these parameters and previously obtained locomotor electromyogram data, stimulations were performed on bilateral joint muscle pairs to produce reciprocal flexion/extension movements of the ankle for 15 minutes while three-dimensional joint kinematics were assessed.

RESULTS

Rhythmic muscular electrical stimulation with needle electrodes was successfully done, but decreased range of motion (ROM) over time. High-frequency and high-amplitude stimulation was also shown to be effective in alleviating decreases in ROM due to muscle fatigue.

CONCLUSIONS

This model will be useful for investigating the ability of rhythmic muscular electrical stimulation therapy to promote motor recovery, in addition to the efficacy of combining treatments with spinal cord regeneration therapy after spinal cord injuries.

Repetetive hindlimb movement using intermittent adaptive neuromuscular electrical stimulation in an incomplete spinal cord injury rodent model

The long-term objective of this work is to understand the mechanisms by which electrical stimulation based movement therapies may harness neural plasticity to accelerate and enhance sensorimotor recovery after incomplete spinal cord injury (iSCI). An adaptive neuromuscular electrical stimulation (aNMES) paradigm was implemented in adult Long Evans rats with thoracic contusion injury (T8 vertebral level, 155+/-2 Kdyne). In lengthy sessions with lightly anesthetized animals, hip flexor and extensor muscles were stimulated using an aNMES control system in order to generate desired hip movements. The aNMES control system, which used a pattern generator/pattern shaper structure, adjusted pulse amplitude to modulate muscle force in order to control hip movement. An intermittent stimulation paradigm was used (5-cycles/set; 20-second rest between sets; 100 sets). In each cycle, hip rotation caused the foot plantar surface to contact a stationary brush for appropriately timed cutaneous input. Sessions were repeated over several days while the animals recovered from injury. Results indicated that aNMES automatically and reliably tracked the desired hip trajectory with low error and maintained range of motion with only gradual increase in stimulation during the long sessions. Intermittent aNMES thus accounted for the numerous factors that can influence the response to NMES: electrode stability, excitability of spinal neural circuitry, non-linear muscle recruitment, fatigue, spinal reflexes due to cutaneous input, and the endogenous recovery of the animals. This novel aNMES application in the iSCI rodent model can thus be used in chronic stimulation studies to investigate the mechanisms of neuroplasticity targeted by NMES-based repetitive movement therapy.

Neuromuscular stimulation therapy after incomplete spinal cord injury promotes recovery of interlimb coordination during locomotion

The mechanisms underlying the effects of neuromuscular electrical stimulation (NMES) induced repetitive limb movement therapy after incomplete spinal cord injury (iSCI) are unknown. This study establishes the capability of using therapeutic NMES in rodents with iSCI and evaluates its ability to promote recovery of interlimb control during locomotion. Ten adult female Long Evans rats received thoracic spinal contusion injuries (T9; 156 +/- 9.52 Kdyne). 7 days post-recovery, 6/10 animals received NMES therapy for 15 min/day for 5 days, via electrodes implanted bilaterally into hip flexors and extensors. Six intact animals served as controls. Motor function was evaluated using the BBB locomotor scale for the first 6 days and on 14th day post-injury. 3D kinematic analysis of treadmill walking was performed on day 14 post-injury. Rodents receiving NMES therapy exhibited improved interlimb coordination in control of the hip joint, which was the specific NMES target. Symmetry indices improved significantly in the therapy group. Additionally, injured rodents receiving therapy more consistently displayed a high percentage of 1:1 coordinated steps, and more consistently achieved proper hindlimb touchdown timing. These results suggest that NMES techniques could provide an effective therapeutic tool for neuromotor treatment following iSCI.