Functional electrical stimulation after spinal cord injury: current use, therapeutic effects and future directions

Determining grasp selection from arm trajectories via deep learning to enable functional hand movement in tetraplegia

Background

Cervical spinal cord injury severely affects grasping ability of its survivors. Fortunately, many individuals with tetraplegia retain residual arm movements that allow them to reach for objects. We propose a wearable technology that utilizes arm movement trajectory information and deep learning methods to determine grasp selection. Furthermore, we combined this approach with neuromuscular stimulation to determine if self-driven functional hand movement could be enabled in spinal cord injury participants.

Methods

Two cervical SCI participants performed arbitrary and natural reaching movements toward target objects in three-dimensional space, which were recorded using an inertial sensor worn on their wrist. Time series classifiers were trained to recognize the trajectories using either a Dynamic Time Warping (DTW) algorithm or a Long Short-Term Memory (LSTM) recurrent neural network. As an initial proof-of-concept, we demonstrate real-time classification of the arbitrary movements using DTW only (due to its implementation simplicity), which when used in combination with a high density neuromuscular stimulation sleeve with textile electrodes, enabled participants to perform functional grasping.

Results

Participants were able to consistently perform arbitrary two-dimensional and three-dimensional arm movements which could be classified with high accuracy. Furthermore, it was found that natural reaching trajectories for two different target objects (requiring two different grasp types) were distinct and also discriminable with high accuracy. In offline comparisons, LSTM (mean accuracies 99%) performed significantly better than DTW (mean accuracies 86 and 83%) for both arbitrary and natural reaching movements, respectively. Type I and II errors occurred more frequently for DTW (up to 60 and 15%, respectively), whereas it stayed under 5% for LSTM. Also, DTW achieved online accuracy of 79%.

Conclusions

We demonstrate the feasibility of utilizing arm trajectory information to determine grasp selection using a wearable inertial sensor along with DTW and deep learning methods. Importantly, this technology can be successfully used to control neuromuscular stimulation and restore functional independence to individuals living with paralysis.

Trial registration

NCT, NCT03385005. Registered September 26, 2017.

Enhanced Motor Imagery Based Brain- Computer Interface via FES and VR for Lower Limbs

Motor imagery based brain-computer interface (MI-BCI) has been studied for improvement of patients' motor function in neurorehabilitation and motor assistance. However, the difficulties in performing imagery tasks limit its application. To overcome the limitation, an enhanced MI-BCI based on functional electrical stimulation (FES) and virtual reality (VR) is proposed in this study. On one hand, the FES is used to stimulate the subjects' lower limbs before their imagination to make them experience the muscles' contraction and improve their attention on the lower limbs, by which it is supposed that the subjects' motor imagery (MI) abilities can be enhanced. On the other hand, a ball-kicking movement scenario from the first-person perspective is designed to provide visual guidance for performing MI tasks. The combination of FES and VR can be used to reduce the difficulties in performing MI tasks and improve classification accuracy. Finally, the comparison experiments were conducted on twelve healthy subjects to validate the performance of the enhanced MI-BCI. The results show that the classification performance can be improved significantly by using the proposed MI-BCI in terms of the classification accuracy (ACC), the area under the curve (AUC) and the F1 score (paired t-test, ).

"I Felt the Ball"-The Future of Spine Injury Recovery

Spinal cord injury (SCI) has no cure and individuals with SCI become dependent on others for life. After injury, the signals below the lesion are disrupted, but the brain still produces motor commands. Researchers have bypassed this obstacle, which has given rise to the brain-machine interface (BMI). BMI devices are implanted in the brain or spinal cord, where they decode and send signals beyond the injured segment. Experiments were initially conducted on animals, with favorable results. BMIs are classified according to their type, function, signal generation, and so on. Because of invasiveness, their long-term use is questionable, because of infections and complications. The use of an implantable epidural array in patients with chronic SCI showed that participants were able to walk with the help of a stimulator, and after months of training, they were able to walk with the stimulator turned off. Another innovation is a robotic suit for paraplegics and tetraplegics that supports the movement of limbs. The research on stem cells has not shown favorable results. In future, one of these cutting-edge technologies will prevail over the other, but BMI seems to have the upper hand. The future of BMI with fusion of robotics and artificial intelligence is promising for patients with chronic SCI. These modern devices need to be less invasive, biocompatible, easily programmable, portable, and cost-effective. After these hurdles are overcome, the devices may become the mainstay of potential rehabilitation therapy for partial recovery. The time may come when all patients with severe SCI are told "You will walk again."

Movement Caused by Electrical Stimulation of the Lumbosacral Region in Standing Horses

Electrical stimulation is commonly used as a modality for physical therapy in human and veterinary medicine. However, studies measuring the movement generated by electrical stimulation in horses are rare. The present study therefore evaluates the range of movement provoked by a commercially available physical therapy unit (FES310) and contrasts it with the movement generated by manually induced pelvic inclination (back rounding). Ten horses were tested on three measurement days over one week. Electrical stimulation was applied via a back treatment pad (belonging to the FES310 system) containing six electrodes (three on either side of the spine) placed over the lumbosacral region. This system produced a pulsed, biphasic electrical stimulation in a rectangular waveform which was gradually increased to a maximum of 10 volts. Before and after electrical stimulation testing, manual pelvic inclination was achieved by pressure on two points lateral to the root of the tail. Muscle tone and lameness were evaluated before and after treatments. Skinfold thickness, body condition score, and body mass were measured to detect possible confounding factors. Using kinematics, the angle ranges during movement of ten three-dimensional angles of the trunk, the pelvis, and the hind limbs were further analyzed. Movement was produced with manual stimulation in every tested individual on all measurement days and with electrical stimulation on at least one measurement day. The electrical stimulation led to significantly (P < .05) smaller angle ranges which were 15 %-57 % of the median of the manually stimulated movement. Strong positive correlations between angle ranges of the electrically generated movement were found for the hind limbs implicating their involvement in the movement created. Correlations between skinfold thickness, body condition score, and body mass with the angle ranges were weak and not significant. Before and after electrical and manual stimulation, muscle tone and lameness were similar. In the present study, both electrical and manual stimulation were proven to produce significant trunk and hind limb movement. Within this study's electrical stimulation treatment protocol, the movement generated by electrical stimulation was significantly less than the movement caused by manual pelvic inclination. However, electrical stimulation could easily be applied over a longer period and in a higher frequency than it would be possible for manual pelvic inclination. This treatment shows potential for stabilization and or mobilization of the lumbosacral region, although its efficiency as a therapeutic tool and its effect on specific orthopedic problems and is to be evaluated in further research.

Visual Feedback Control of a Rat Ankle Angle Using a Wirelessly Powered Two-Channel Neurostimulator

Peripheral nerve disconnections cause severe muscle atrophy and consequently, paralysis of limbs. Reinnervation of denervated muscle by transplanting motor neurons and applying Functional Electrical Stimulation (FES) onto peripheral nerves is an important procedure for preventing irreversible degeneration of muscle tissues. After the reinnervation of denervated muscles, multiple peripheral nerves should be stimulated independently to control joint motion and reconstruct functional movements of limbs by the FES. In this study, a wirelessly powered two-channel neurostimulator was developed with the purpose of applying selective FES to two peripheral nerves—the peroneal nerve and the tibial nerve in a rat. The neurostimulator was designed in such a way that power could be supplied wirelessly, from a transmitter coil to a receiver coil. The receiver coil was connected, in turn, to the peroneal and tibial nerves in the rat. The receiver circuit had a low pass filter to allow detection of the frequency of the transmitter signal. The stimulation of the nerves was switched according to the frequency of the transmitter signal. Dorsal/plantar flexion of the rat ankle joint was selectively induced by the developed neurostimulator. The rat ankle joint angle was controlled by changing the stimulation electrode and the stimulation current, based on the Proportional Integral (PI) control method using a visual feedback control system. This study was aimed at controlling the leg motion by stimulating the peripheral nerves using the neurostimulator.

Distributed Repetitive Learning Control for Cooperative Cadence Tracking in Functional Electrical Stimulation Cycling

Closed-loop control of functional electrical stimulation coupled with motorized assistance to induce cycling is a rehabilitative strategy that can improve the mobility of people with neurological conditions (NCs). However, robust control methods, which are currently pervasive in the cycling literature, have limited effectiveness due to the use of high stimulation intensity leading to accelerated fatigue during cycling protocols. This paper examines the design of a distributed repetitive learning controller (RLC) that commands an independent learning feedforward term to each of the six stimulated lower-limb muscle groups and an electric motor during the tracking of a periodic cadence trajectory. The switched controller activates lower limb muscles during kinematic efficient regions of the crank cycle and provides motorized assistance only when most needed (i.e., during the portions of the crank cycle where muscles evoke a low torque output). The controller exploits the periodicity of the desired cadence trajectory to learn from previous control inputs for each muscle group and electric motor. A Lyapunov-based stability analysis guarantees asymptotic tracking via an invariance-like corollary for nonsmooth systems. The switched distributed RLC was evaluated in experiments with seven able-bodied individuals and five participants with NCs. A mean root-mean-squared cadence error of 3.58 ± 0.43 revolutions per minute (RPM) (0.07 ± 7.35% average error) and 4.26 ± 0.84 RPM (0.1 ± 8.99% average error) was obtained for the healthy and neurologically impaired populations, respectively.

Adaptive multichannel FES neuroprosthesis with learning control and automatic gait assessment

Background

FES (Functional Electrical Stimulation) neuroprostheses have long been a permanent feature in the rehabilitation and gait support of people who had a stroke or have a Spinal Cord Injury (SCI). Over time the well-known foot switch triggered drop foot neuroprosthesis, was extended to a multichannel full-leg support neuroprosthesis enabling improved support and rehabilitation. However, these neuroprostheses had to be manually tuned and could not adapt to the persons’ individual needs. In recent research, a learning controller was added to the drop foot neuroprosthesis, so that the full stimulation pattern during the swing phase could be adapted by measuring the joint angles of previous steps.

Methods

The aim of this research is to begin developing a learning full-leg supporting neuroprosthesis, which controls the antagonistic muscle pairs for knee flexion and extension, as well as for ankle joint dorsi- and plantarflexion during all gait phases. A method was established that allows a continuous assessment of knee and foot joint angles with every step. This method can warp the physiological joint angles of healthy subjects to match the individual pathological gait of the subject and thus allows a direct comparison of the two. A new kind of Iterative Learning Controller (ILC) is proposed which works independent of the step duration of the individual and uses physiological joint angle reference bands.

Results

In a first test with four people with an incomplete SCI, the results showed that the proposed neuroprosthesis was able to generate individually fitted stimulation patterns for three of the participants. The other participant was more severely affected and had to be excluded due to the resulting false triggering of the gait phase detection. For two of the three remaining participants, a slight improvement in the average foot angles could be observed, for one participant slight improvements in the averaged knee angles. These improvements where in the range of 4^circat the times of peak dorsiflexion, peak plantarflexion, or peak knee flexion.

Conclusions

Direct adaptation to the current gait of the participants could be achieved with the proposed method. The preliminary first test with people with a SCI showed that the neuroprosthesis can generate individual stimulation patterns. The sensitivity to the knee angle reset, timing problems in participants with significant gait fluctuations, and the automatic ILC gain tuning are remaining issues that need be addressed. Subsequently, future studies should compare the improved, long-term rehabilitation effects of the here presented neuroprosthesis, with conventional multichannel FES neuroprostheses.

Development of 3D-printed myoelectric hand orthosis for patients with spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a severe medical condition affecting the hand and locomotor function. New medical technologies, including various wearable devices, as well as rehabilitation treatments are being developed to enhance hand function in patients with SCI. As three-dimensional (3D) printing has the advantage of being able to produce low-cost personalized devices, there is a growing appeal to apply this technology to rehabilitation equipment in conjunction with scientific advances. In this study, we proposed a novel 3D-printed hand orthosis that is controlled by electromyography (EMG) signals. The orthosis was designed to aid the grasping function for patients with cervical SCI. We applied this hand exoskeleton system to individuals with tetraplegia due to SCI and validated its effectiveness.

METHODS

The 3D architecture of the device was designed using computer-aided design software and printed with a polylactic acid filament. The dynamic hand orthosis enhanced the tenodesis grip to provide sufficient grasping function. The root mean square of the EMG signal was used as the input for controlling the device. Ten subjects with hand weakness due to chronic cervical SCI were enrolled in this study, and their hand function was assessed before and after wearing the orthosis. The Toronto Rehabilitation Institute Hand Function Test (TRI-HFT) was used as the primary outcome measure. Furthermore, improvements in functional independence in daily living and device usability were evaluated.

RESULTS

The newly developed orthosis improved hand function of subjects, as determined using the TRI-HFT (p < 0.05). Furthermore, participants obtained immediate functionality on eating after wearing the orthosis. Moreover, most participants were satisfied with the device as determined by the usability test. There were no side effects associated with the experiment.

CONCLUSIONS

The 3D-printed myoelectric hand orthosis was intuitive, easy to use, and showed positive effects in its ability to handle objects encountered in daily life. This study proved that combining simple EMG-based control strategies and 3D printing techniques was feasible and promising in rehabilitation engineering.

TRIAL REGISTRATION

Clinical Research Information Service (CRiS), Republic of Korea. KCT0003995. Registered 2 May 2019 - Retrospectively registered.

Neuromusculoskeletal Modeling-Based Prostheses for Recovery After Spinal Cord Injury

Concurrent stimulation and reinforcement of motor and sensory pathways has been proposed as an effective approach to restoring function after developmental or acquired neurotrauma. This can be achieved by applying multimodal rehabilitation regimens, such as thought-controlled exoskeletons or epidural electrical stimulation to recover motor pattern generation in individuals with spinal cord injury (SCI). However, the human neuromusculoskeletal (NMS) system has often been oversimplified in designing rehabilitative and assistive devices. As a result, the neuromechanics of the muscles is seldom considered when modeling the relationship between electrical stimulation, mechanical assistance from exoskeletons, and final joint movement. A powerful way to enhance current neurorehabilitation is to develop the next generation prostheses incorporating personalized NMS models of patients. This strategy will enable an individual voluntary interfacing with multiple electromechanical rehabilitation devices targeting key afferent and efferent systems for functional improvement. This narrative review discusses how real-time NMS models can be integrated with finite element (FE) of musculoskeletal tissues and interface multiple assistive and robotic devices with individuals with SCI to promote neural restoration. In particular, the utility of NMS models for optimizing muscle stimulation patterns, tracking functional improvement, monitoring safety, and providing augmented feedback during exercise-based rehabilitation are discussed.

Brain Computer Interfaces in Rehabilitation Medicine

One innovation currently influencing physical medicine and rehabilitation is brain-computer interface (BCI) technology. BCI systems used for motor control record neural activity associated with thoughts, perceptions, and motor intent; decode brain signals into commands for output devices; and perform the user's intended action through an output device. BCI systems used for sensory augmentation transduce environmental stimuli into neural signals interpretable by the central nervous system. Both types of systems have potential for reducing disability by facilitating a user's interaction with the environment. Investigational BCI systems are being used in the rehabilitation setting both as neuroprostheses to replace lost function and as potential plasticity-enhancing therapy tools aimed at accelerating neurorecovery. Populations benefitting from motor and somatosensory BCI systems include those with spinal cord injury, motor neuron disease, limb amputation, and stroke. This article discusses the basic components of BCI for rehabilitation, including recording systems and locations, signal processing and translation algorithms, and external devices controlled through BCI commands. An overview of applications in motor and sensory restoration is provided, along with ethical questions and user perspectives regarding BCI technology.

Is Technology for Orthostatic Hypotension Ready for Primetime?

Spinal cord injury (SCI) often results in the devastating loss of motor, sensory, and autonomic function. After SCI, the interruption of descending sympathoexcitatory pathways disrupts supraspinal control of blood pressure (BP). A common clinical consequence of cardiovascular dysfunction after SCI is orthostatic hypotension (OH), a debilitating condition characterized by rapid profound decreases in BP when assuming an upright posture. OH can result in a diverse array of insidious and pernicious health consequences. Acute effects of OH include decreased cardiac filling, cerebral hypoperfusion, and associated presyncopal symptoms such as lightheadedness and dizziness. Over the long term, repetitive exposure to OH is associated with a drastically increased prevalence of heart attack and stroke, which are leading causes of death in those with SCI. Current recommendations for managing BP after SCI primarily include pharmacologic interventions with prolonged time to effect. Because most episodes of OH occur in less than 3 minutes, this delay in action often renders most pharmacologic interventions ineffective. New innovative technologies such as epidural and transcutaneous spinal cord stimulation are being explored to solve this problem. It might be possible to electrically stimulate sympathetic circuitry caudal to the injury and elicit rapid modulation of BP to manage OH. This review describes autonomic control of the cardiovascular system before injury, resulting cardiovascular consequences after SCI such as OH, and the clinical assessment tools for evaluating autonomic dysfunction after SCI. In addition, current approaches for clinically managing OH are outlined, and new promising interventions are described for managing this condition.

EMG Pattern Recognition for Persons with Cervical Spinal Cord Injury

Pattern recognition based myoelectric control has been widely explored in the field of prosthetics, but little work has extended to other patient groups. Individuals with neurological injuries such as spinal cord injury may also benefit from more intuitive control that may facilitate more interactive treatments or improved control of functional electrical stimulation (FES) systems or assistive technologies. This work presents a pilot study with 10 individuals with cervical spinal cord injury between A and C on the American Spinal Injury Association Impairment Scale. Subjects attempted to elicit 10 classes of forearm and hand movements while their electromyogram (EMG) was recorded using a cuff of eight electrodes. Various well-known EMG features were evaluated using a linear discriminant analysis classifier, yielding classification error rates as low as 4.3% ± 3.9 across the 10 classes. Reducing the number of classes to five, those required to control a commercial therapeutic FES device, further reduced the error rates to (2.2% ± 4.4). Results from this study provide evidence supporting continued exploration of EMG pattern recognition techniques for use by high-level spinal cord injured populations as a method of intuitive control over interactive FES systems or assistive devices.

Myoelectric signal from below the level of spinal cord injury as a command source for an implanted upper extremity neuroprosthesis - a case report

Implanted motor neuroprostheses offer significant restoration of function for individuals with spinal cord injury. Providing adequate user control for these devices is a challenge but is crucial for successful performance. Electromyographic (EMG) signals can serve as effective control sources, but the number of above-injury muscles suitable to provide EMG-based control signals is very limited. Previous work has shown the presence of below-injury volitional myoelectric signals even in subjects diagnosed with motor complete spinal cord injury. In this case report, we present a demonstration of a hand grasp neuroprosthesis being controlled by a user with a C6 level, motor complete injury through EMG signals from their toe flexor. These signals were successfully translated into a functional grasp output, which performed similarly to the participant’s usual shoulder position control in a grasp-release functional test. This proof-of-concept demonstrates the potential for below-injury myoelectric activity to serve as a novel form of neuroprosthesis control.

Ventilator-induced diaphragm dysfunction: translational mechanisms lead to therapeutical alternatives in the critically ill

Mechanical ventilation [MV] is a life-saving technique delivered to critically ill patients incapable of adequately ventilating and/or oxygenating due to respiratory or other disease processes. This necessarily invasive support however could potentially result in important iatrogenic complications. Even brief periods of MV may result in diaphragm weakness [i.e., ventilator-induced diaphragm dysfunction [VIDD]], which may be associated with difficulty weaning from the ventilator as well as mortality. This suggests that VIDD could potentially have a major impact on clinical practice through worse clinical outcomes and healthcare resource use. Recent translational investigations have identified that VIDD is mainly characterized by alterations resulting in a major decline of diaphragmatic contractile force together with atrophy of diaphragm muscle fibers. However, the signaling mechanisms responsible for VIDD have not been fully established. In this paper, we summarize the current understanding of the pathophysiological pathways underlying VIDD and highlight the diagnostic approach, as well as novel and experimental therapeutic options.

Garments for functional electrical stimulation: Design and proofs of concept

Introduction

Repeated use of functional electrical stimulation can promote functional recovery in individuals with neurological paralysis. We designed garments able to deliver functional electrical stimulation.

Methods

Shirts and pants containing electrodes knitted with a conductive yarn were produced. Electrodes were moistened with water before use. Stimulation intensity at four thresholds levels (sensory, movement, full range of motion, and maximal), stimulation comfort, and electrical properties of the interface were tested in one able-bodied subject with garment electrodes and size-matched conventional gel electrodes. The pants and shirt were then used to explore usability and design limitations.

Results

Compared to gel electrodes, fabric electrodes had a lower sensory threshold (on forearm muscles) but they had a higher maximal stimulation threshold (for all tested muscles). The stimulation delivery was comfortable when the garment electrodes were recently moistened; however, as the electrodes dried (within 9 to 18 min) stimulation became unpleasant. Inconsistent water content in the fabric electrodes caused inconsistent intensity thresholds and inconsistent voltage necessary to apply a desired stimulation current. Garments’ tightness and impracticality of electrode lead necessitate further design improvement.

Conclusions

Fabric electrodes offer a promising alternative to gel electrodes. Further work involving people with paralysis is required to overcome the identified challenges.

Investigation of different stimulation patterns with doublet pulses to reduce muscle fatigue

Introduction: Functional electrical stimulation is a common technique used in the rehabilitation of individuals with a spinal cord injury to produce functional movement of paralysed muscles. However, it is often associated with rapid muscle fatigue which limits its applications. Methods: The objective of this study is to investigate the effects on the onset of fatigue of different multi-electrode patterns of stimulation via multiple pairs of electrodes using doublet pulses: Synchronous stimulation is compared to asynchronous stimulation patterns which are activated sequentially (AsynS) or randomly (AsynR), mimicking voluntary muscle activation by targeting different motor units. We investigated these three different approaches by applying stimulation to the gastrocnemius muscle repeatedly for 10 min (300 ms stimulation followed by 700 ms of no-stimulation) with 40 Hz effective frequency for all protocols and doublet pulses with an inter-pulse-interval of 6 ms. Eleven able-bodied volunteers (28 ± 3 years old) participated in this study. Ultrasound videos were recorded during stimulation to allow evaluation of changes in muscle morphology. The main fatigue indicators we focused on were the normalised fatigue index, fatigue time interval and pre-post twitch–tetanus ratio. Results: The results demonstrate that asynchronous stimulation with doublet pulses gives a higher normalised fatigue index (0.80 ± 0.08 and 0.87 ± 0.08) for AsynS and AsynR, respectively, than synchronous stimulation (0.62 ± 0.06). Furthermore, a longer fatigue time interval for AsynS (302.2 ± 230.9 s) and AsynR (384.4 ± 279.0 s) compared to synchronous stimulation (68.0 ± 30.5 s) indicates that fatigue occurs later during asynchronous stimulation; however, this was only found to be statistically significant for one of two methods used to calculate the group mean. Although no significant difference was found in pre-post twitch–tetanus ratio, there was a trend towards these effects. Conclusion: In this study, we proposed an asynchronous stimulation pattern for the application of functional electrical stimulation and investigated its suitability for reducing muscle fatigue compared to previous methods. The results show that asynchronous multi-electrode stimulation patterns with doublet pulses may improve fatigue resistance in functional electrical stimulation applications in some conditions.

Non-invasive, Brain-controlled Functional Electrical Stimulation for Locomotion Rehabilitation in Individuals with Paraplegia

Spinal cord injury (SCI) impairs the flow of sensory and motor signals between the brain and the areas of the body located below the lesion level. Here, we describe a neurorehabilitation setup combining several approaches that were shown to have a positive effect in patients with SCI: gait training by means of non-invasive, surface functional electrical stimulation (sFES) of the lower-limbs, proprioceptive and tactile feedback, balance control through overground walking and cue-based decoding of cortical motor commands using a brain-machine interface (BMI). The central component of this new approach was the development of a novel muscle stimulation paradigm for step generation using 16 sFES channels taking all sub-phases of physiological gait into account. We also developed a new BMI protocol to identify left and right leg motor imagery that was used to trigger an sFES-generated step movement. Our system was tested and validated with two patients with chronic paraplegia. These patients were able to walk safely with 65-70% body weight support, accumulating a total of 4,580 steps with this setup. We observed cardiovascular improvements and less dependency on walking assistance, but also partial neurological recovery in both patients, with substantial rates of motor improvement for one of them.

Nanocapsules for Programmed Neurotransmitter Release: Toward Artificial Extracellular Synaptic Vesicles

Nanocapsules present a promising platform for delivering chemicals and biomolecules to a site of action in a living organism. Because the biological action of the encapsulated molecules is blocked until they are released from the nanocapsules, the encapsulation structure enables triggering of the topical and timely action of the molecules at the target site. A similar mechanism seems promising for the spatiotemporal control of signal transduction triggered by the release of signal molecules in neuronal, metabolic, and immune systems. From this perspective, nanocapsules can be regarded as practical tools to apply signal molecules such as neurotransmitters to intervene in signal transduction. However, spatiotemporal control of the payload release from nanocapsules persists as a key technical issue. Stimulus-responsive nanocapsules that release payloads in response to external input of physical stimuli are promising platforms to enable programmed payload release. These programmable nanocapsules encapsulating neurotransmitters are expected to lead to new insights and perspectives related to artificial extracellular synaptic vesicles that might provide an experimental and therapeutic strategy for neuromodulation and nervous system disorders.

Intermittent injection of Methylprednisolone Sodium Succinate in the treatment of Cervical Spinal Cord injury complicated with incomplete paraplegia

OBJECTIVE

To evaluate the clinical efficacy and safety of intermittent injection of methylprednisolone sodium succinate in the treatment of cervical spinal cord injury complicated with incomplete paraplegia.

METHODS

Seventy-eight patients with cervical spinal cord injury complicated with incomplete paraplegia who were admitted between August 2016 and December 2017 were enrolled and grouped into an observation group and a control group using random number table, 39 in each group. Patients in the control group were given vertebral body decompression and bone grafting and internal fixation according to the severity of spinal cord compression, while patients in the observation group were treated by methylprednisolone sodium succinate in addition to the same treatment as the control group. The clinical efficacy and medicine associated adverse reactions were compared between the two groups.

RESULTS

The cure rate of the observation group was significantly higher than that of the control group (46.2% (18/39) vs. 20.5% (8/39)). After the treatment, the Japanese Orthopaedic Association (JOA) score and American Spinal Cord Injury Association (ASIA) score of the two groups after treatment were significantly higher compared to before treatment, and the scores of the observation group were much higher than those of the control group (P<0.05). The incidence of adverse reactions of the observation and control groups was 15.4% and 17.9% respectively, and the difference was not statistically significant (P>0.05).

CONCLUSION

Intermittent injection of methylprednisolone sodium succinate has definite efficacy in treating cervical spinal cord injury complicated with incomplete paraplegia, with a low incidence of adverse reactions; hence it is worth promotion.

User-centered practicability analysis of two identification strategies in electrode arrays for FES induced hand motion in early stroke rehabilitation

BACKGROUND

Surface electrode arrays have become popular in the application of functional electrical stimulation (FES) on the forearm. Arrays consist of multiple, small elements, which can be activated separately or in groups, forming virtual electrodes (VEs). As technology progress yields rising numbers of possible elements, an effective search strategy for suitable VEs in electrode arrays is of increasing importance. Current methods can be time-consuming, lack user integration, and miss an evaluation regarding clinical acceptance and practicability.

METHODS

Two array identification procedures with different levels of user integration-a semi-automatic and a fully automatic approach-are evaluated. The semi-automatic method allows health professionals to continuously modify VEs via a touchscreen while the stimulation intensities are automatically controlled to maintain sufficient wrist extension. The automatic approach evaluates stimulation responses of various VEs for different intensities using a cost function and joint-angles recordings. Both procedures are compared in a clinical setup with five sub-acute stroke patients with moderate hand disabilities. The task was to find suitable VEs in two arrays with 59 elements in total to generate hand opening and closing for a grasp-and-release task. Practicability and acceptance by patients and health professionals were investigated using questionnaires and interviews.

RESULTS

Both identification methods yield suitable VEs for hand opening and closing in patients who could tolerate the stimulation. However, the resulting VEs differed for both approaches. The average time for a complete search was 25% faster for the semi-automatic approach (semi-automatic: 7.3min, automatic: 10.5min). User acceptance was high for both methods, while no clear preference could be identified.

CONCLUSIONS

The semi-automatic approach should be preferred as the search strategy in arrays on the forearm. The observed faster search duration will further reduce when applying the system repeatedly on a patient as only small position adjustments for VEs are required. However, the setup time will significantly increase for generation of various grasp types and adaptation to different arm postures. We recommend different levels of user integration in FES systems such that the search strategy can be chosen based on the users' preferences and application scenario.

Muscle Fatigue Post-stroke Elicited From Kilohertz-Frequency Subthreshold Nerve Stimulation

Purpose: Rapid muscle fatigue limits clinical applications of functional electrical stimulation (FES) for individuals with motor impairments. This study aimed to characterize the sustainability of muscle force elicited with a novel transcutaneous nerve stimulation technique.

Method: A hemiplegic chronic stroke survivor was recruited in this case study. Clustered subthreshold pulses of 60-μs with kilohertz (12.5 kHz) carrier frequency (high-frequency mode, HF) were delivered transcutaneously to the proximal segment of the median/ulnar nerve bundles to evaluate the finger flexor muscle fatigue on both sides of the stroke survivor. Conventional nerve stimulation technique with 600-μs pulses at 30 Hz (low-frequency mode, LF) served as the control condition. Fatigue was evoked by intermittently delivering 3-s stimulation trains with 1-s resting. For fair comparison, initial contraction forces (approximately 30% of the maximal voluntary contraction) were matched between the HF and LF modes. Muscle fatigue was evaluated through elicited finger flexion forces (amplitude and fluctuation) and muscle activation patterns quantified by high-density electromyography (EMG).

Result: Compared with those from the LF stimuli, the elicited forces declined more slowly, and the force plateau was higher under the HF stimulation for both the affected and contralateral sides, resulting in a more sustainable force output at higher levels. Meanwhile, the force fluctuation under the HF stimulation increased more slowly, and, thus, was smaller after successive stimulation trains compared with the LF stimuli, indicating a less synchronized activation of muscle fibers. The efficiency of the muscle activation, measured as the force-EMG ratio, was also higher in the HF stimulation mode.

Conclusion: Our results indicated that the HF nerve stimulation technique can reduce muscle fatigue in stroke survivors by maintaining a higher efficiency of muscle activations compared with the LF stimulation. The technique can help improve the performance of neurorehabilitation methods based on electrical stimulation, and facilitate the utility of FES in clinical populations.

FES Coupled With A Powered Exoskeleton For Cooperative Muscle Contribution In Persons With Paraplegia

This paper describes the effects of a novel functional electrical stimulation (FES) system which has been integrated in a powered exoskeleton to provide up to 10 channels of stimulation to users with paraplegia via surface electrodes. Experimental data collected from three users with spinal cord injury (SCI) indicate the system reduced the exoskeleton motor torques necessary to perform sit-to-stand transitions in the exoskeleton. All subjects exhibited reduced muscle spasticity immediately after walking in the exoskeleton with FES. Additionally, one subject with stretch-reflex spasms exhibited increased joint excursion and reduced exoskeleton motor torques required to achieve over-ground gait when FES was incorporated.

Neurotransmitter-Loaded Nanocapsule Triggers On-Demand Muscle Relaxation in Living Organism

This paper reports the on-demand artificial muscle relaxation using a thermosensitive liposome encapsulating γ-aminobutyric acid (GABA) inhibitory neurotransmitter. Muscle relaxation is not feasible in principle, although muscle contraction can be easily induced by electrical stimulation. Herein, thermosensitive liposomes (phase transition temperature = 40 °C) were synthesized to encapsulate GABA and were injected into a leg of a living beetle. The leg was wrapped around by a Ni-Cr wire heater integrated with a thermocouple to enable the feedback control and to manipulate the leg temperature. The injected leg was temporarily immobilized by heating it up to 45 °C. The leg did not swing even by electrically stimulating the leg muscle. Subsequently, the leg recovered to swing. The result indicates that GABA was released from liposomes and fed to the leg muscle, enabling temporal muscle relaxation.

Anatomical Feasibility of Extradural Transferring S2 and S3 Ventral Roots to S1 Ventral Root for Restoring Neurogenic Bladder in Spinal Cord Injury

STUDY DESIGN

Anatomic study in six formalin-fixed cadavers.

OBJECTIVE

To determine the anatomical feasibility of transferring the S2 and S3 ventral roots (VRs) to S1 VR as a method for restoring bladder dysfunction in spinal cord injury.

SUMMARY OF BACKGROUND DATA

A large quantity of researches of neuroanastomosis methods have been used for treating the bladder dysfunction in spinal cord injury. However, some limitations retard the development of those studies.

METHODS

In this study, six formalin-fixed cadavers (four males, two females) were dissected. The feasibility of exposing the S1, S2, and S3 extradural nerve roots by the limited laminectomy, isolating the VR and dorsal roots from each extradural nerve root and transferring the S2,S3 VRs to the S1 VR were assessed. The pertinent distances and the nerve cross-sectional areas in each specimen were measured. The morphology of each nerve root was observed by hematoxylin-eosin staining.

RESULTS

The limited laminectomy was performed to expose the S1 to S3 extradural nerve roots. The VRs could be isolated from each extradural nerve root at the location of the dorsal root ganglion and the hematoxylin-eosin staining showed that there were some connective tissues separating the VRs from the corresponding dorsal root ganglion. The S2 and S3 VRs have sufficient lengths to be transferred to S1 VR without grafting. The mean cross-sectional area of the S1 VR was 2.60 ± 0.17 mm, and that was 1.02 ± 0.32 mm and 0.51 ± 0.21 mm of the S2 and S3 VRs, respectively.

CONCLUSION

This study demonstrated that use of the S2 and S3 VRs for extradural transfer to S1 VR for restoring bladder dysfunction is surgically feasible.

LEVEL OF EVIDENCE

5.

Holding Static Arm Configurations With Functional Electrical Stimulation: A Case Study

Functional electrical stimulation (FES) is a promising solution for restoring functional motion to individuals with paralysis, but the potential for achieving any desired full-arm reaching motion has not been realized. We present a combined feedforward-feedback controller capable of automatically calculating and applying the necessary muscle stimulations to hold the wrist of an individual with high tetraplegia in a desired static position. We used the controller to hold a complete arm configuration to maintain a series of static wrist positions. The average distance to the target wrist position, or accuracy, was 2.9 cm. The precision is defined as the radius of the 95% confidence ellipsoid for the final positions of a set of trials with the same muscle stimulations and starting position. The average precision was 3.7 cm. The control architecture used in this study to hold static positions has the potential to control arbitrary reaching motions.

Mobile Game Induces Active Engagement on Neuromuscular Electrical Stimulation Training in Patients with Stroke

This study aimed to investigate the effectiveness of the mobile game-based neuromuscular electrical stimulation (MG-NMES) with assessing usability issues, such as attention and curiosity, and intrinsically interesting issues, which is necessary for successful poststroke rehabilitation. With the conventional NMES (C-NMES) system, the subjects underwent active repetitive cyclic NMES training. For assessment of usability issues, 20 hemiplegic stroke subjects were randomly divided into two groups. The subjects in the MG-NMES group (n = 9) and C-NMES group (n = 11) underwent 20 minutes of training each day for 5 days. We assessed the subjects' attention, curiosity, and intrinsically interesting issues; and using questionnaires they answered questions regarding their expectations of the training outcome after each training session. We found that the subjects in the MG-NMES group maintained their attention and interest for the 5 days, and their curiosity and expectation of a positive training outcome gradually increased as the training proceeded. In contrast, the C-NMES group reported no change in their attention or curiosity, but it was lower than the subjects in the MG-NMES group. In addition, their interest gradually decreased, which may have reduced their expectations of a positive outcome as the sessions progressed. There were no side effects during the training sessions in either group. The MG-NMES training paradigm developed is a new, readily available, and highly motivating MG-NMES training system. Based on the usability test, the reported advantages of the system were improved attention and flow experience during NMES training.

Trunk Stability Enabled by Noninvasive Spinal Electrical Stimulation after Spinal Cord Injury

Electrical neuromodulation of spinal networks improves the control of movement of the paralyzed limbs after spinal cord injury (SCI). However, the potential of noninvasive spinal stimulation to facilitate postural trunk control during sitting in humans with SCI has not been investigated. We hypothesized that transcutaneous electrical stimulation of the lumbosacral enlargement can improve trunk posture. Eight participants with non-progressive SCI at C3-T9, American Spinal Injury Association Impairment Scale (AIS) A or C, performed different motor tasks during sitting. Electromyography of the trunk muscles, three-dimensional kinematics, and force plate data were acquired. Spinal stimulation improved trunk control during sitting in all tested individuals. Stimulation resulted in elevated activity of the erector spinae, rectus abdominis, and external obliques, contributing to improved trunk control, more natural anterior pelvic tilt and lordotic curve, and greater multi-directional seated stability. During spinal stimulation, the center of pressure (COP) displacements decreased to 1.36 ± 0.98 mm compared with 4.74 ± 5.41 mm without stimulation (p = 0.0156) in quiet sitting, and the limits of stable displacement increased by 46.92 ± 35.66% (p = 0.0156), 36.92 ± 30.48% (p = 0.0156), 54.67 ± 77.99% (p = 0.0234), and 22.70 ± 26.09% (p = 0.0391) in the forward, backward, right, and left directions, respectively. During self-initiated perturbations, the correlation between anteroposterior arm velocity and the COP displacement decreased from r = 0.5821 (p = 0.0007) without to r = 0.5115 (p = 0.0039) with stimulation, indicating improved trunk stability. These data demonstrate that the spinal networks can be modulated transcutaneously with tonic electrical spinal stimulation to physiological states sufficient to generate a more stable, erect sitting posture after chronic paralysis.

Evaluation of high-density, multi-contact nerve cuffs for activation of grasp muscles in monkeys

OBJECTIVE

The objective of this work was to evaluate whether nerve cuffs can selectively activate hand muscles for functional electrical stimulation (FES). FES typically involves identifying and implanting electrodes in many individual muscles, but nerve cuffs only require implantation at a single site around the nerve. This method is surgically more attractive. Nerve cuffs may also more effectively stimulate intrinsic hand muscles, which are difficult to implant and stimulate without spillover to adjacent muscles.

APPROACH

To evaluate its ability to selectively activate muscles, we implanted and tested the flat interface nerve electrode (FINE), which is designed to selectively stimulate peripheral nerves that innervate multiple muscles (Tyler and Durand 2002 IEEE Trans. Neural Syst. Rehabil. Eng. 10 294-303). We implanted FINEs on the nerves and bipolar intramuscular wires for recording compound muscle action potentials (CMAPs) from up to 20 muscles in each arm of six monkeys. We then collected recruitment curves while the animals were anesthetized.

MAIN RESULT

A single FINE implanted on an upper extremity nerve in the monkey can selectively activate muscles or small groups of muscles to produce multiple, independent hand functions.

SIGNIFICANCE

FINE cuffs can serve as a viable supplement to intramuscular electrodes in FES systems, where they can better activate intrinsic and extrinsic muscles with lower currents and less extensive surgery.

Nanogenerator for Biomedical Applications

In the past 10 years, the development of nanogenerators (NG) has enabled different systems to operate without external power supply. NG have the ability to harvest the mechanical energies in different forms. Human body motions and activities can also serve as the energy source to drive NG and enable self-powered healthcare system. In this review, a summary of several major actual applications of NG in the biomedical fields is made including the circulatory system, the neural system, cell modulation, microbe disinfection, and biodegradable electronics. Nevertheless, there are still many challenges for NG to be actually adopted in clinical applications, including the miniaturization, duration, encapsulation, and output performance. It is also very important to further combine the NG development more precisely with the medical principles. In future, NG can serve as highly promising complementary or even alternative power suppliers to traditional batteries for the healthcare electronics.

Evaluating an open-loop functional electrical stimulation controller for holding the shoulder and elbow configuration of a paralyzed arm

Functional electrical stimulation (FES) is a promising solution for restoring functional motion to individuals with paralysis, but the potential for achieving full-arm reaching motions with FES for various desired tasks has not been realized. We present an open-loop controller capable of calculating and applying the necessary muscle stimulations to hold the wrist of an individual with high tetraplegia at any desired position. We used the controller to hold the wrist at a series of static positions. The controller was capable of discriminating between different wrist positions. The average distance to the target wrist position, or accuracy, was 7.7 cm. The average radius of the 95% confidence ellipsoid for a set of trials with the same muscle stimulations, or precision, was 6.7 cm. Adding feedback or online model updates will likely improve the accuracy for tasks requiring finer control. The controller is a good first step to controlling full-arm motions with FES.

Lower extremity robotic exoskeleton training: Case studies for complete spinal cord injury walking

BACKGROUND

Recent advances in exoskeleton technology has made lower extremity powered exoskeletons (LEPE) a viable treatment tool to restore upright walking mobility to persons with spinal cord injury (SCI).

OBJECTIVE

Evaluate ARKE exoskeleton training within a rehabilitation centre environment.

METHODS

Case studies are presented for two male participants, age 41 and 30, motor complete SCI at T6 (N01) and T12 (N02), respectively, as they progress from new LEPE users to independent walking. The ARKE 2.0 LEPE (Bionik Laboratories Inc., Toronto, Canada) was used for all training (hip and knee powered, forearm crutches, control tablet). Data were collected on session times, activity metrics from ARKE system logs, and qualitative questionnaire feedback.

RESULTS AND CONCLUSION

N01 required 18, 30-minute training sessions to achieve independent walking. N01 walked independently within the 12 session target. Foot strikes were frequently before the end of the programmed swing phase, which were handled by the ARKE control system. Subjective ratings of LEPE learning, comfort, pain, fatigue, and overall experience were high for sitting-standing and moderate to high for walking. This reflected the complexity of learning to safely walk. Qualitative feedback supported the continuation of LEPE use in rehabilitation settings based on end-user desire for upright mobility.

EMG-triggered stimulation post spinal cord injury: A case report

BACKGROUND

Mechanical injury in patients with spinal cord injury (SCI) rarely transects the cord completely, even when the injury is classified as complete. These patients can show sub-clinical evidence of spared motor connections, which might be amenable to targeted rehabilitation. Neurophysiological evaluations can complement the clinical evaluation by providing objective data about conduction across the SCI site.

CASE DESCRIPTION

A twenty-four year old patient with SCI was admitted to a rehabilitation centre 49 days post traumatic SCI. His injury was categorized as motor and sensory complete (AIS A) with a neurological level of C4. The strength of his triceps bilaterally was recorded 0/5 repeatedly by his therapists during the five-month period post-injury. As a result, no training was provided for these muscles during the rehabilitation program. Neurophysiological Assessment: Motor evoked potentials (MEPs) were recorded from his left triceps with transcranial magnetic stimulation (TMS) which confirmed the existence of spared corticospinal connections to this muscle post-injury.

INTERVENTION

He completed a series of active-assisted exercises with an EMG-triggered neuromuscular stimulation (NMS) device for his left triceps comprising 20-minutes elbow extension (15 trials), three times per day for 4 weeks.

OUTCOME

The strength of his left triceps gradually improved to 2/5.

DISCUSSION

Neurophysiological evaluation can be useful in identifying residual function below the level of injury, which can, in turn, be enhanced through appropriate rehabilitation strategies.

Therapeutic Angiogenesis via Solar Cell-Facilitated Electrical Stimulation

Cell therapy has been suggested as a treatment modality for ischemic diseases, but the poor survival and engraftment of implanted cells limit its therapeutic efficacy. To overcome such limitation, we used electrical stimulation (ES) derived from a wearable solar cell for inducing angiogenesis in ischemic tissue. ES enhanced the secretion of angiogenic growth factors and the migration of mesenchymal stem cells (MSCs), myoblasts, endothelial progenitor cells, and endothelial cells in vitro. In a mouse ischemic hindlimb model, ES generated by a solar cell and applied to the ischemic region promoted migration of MSCs toward the ischemic site and upregulated expression of angiogenic paracrine factors (vascular endothelial, basic fibroblast, and hepatocyte growth factors; and stromal cell-derived factor-1α). Importantly, solar cell-generated ES promoted the formation of capillaries and arterioles at the ischemic region, attenuated muscle necrosis and fibrosis, and eventually prevented loss of the ischemic limb. Solar cell ES therapy showed higher angiogenic efficacy than conventional MSC therapy. This study shows the feasibility of using solar cell ES as a novel treatment for therapeutic angiogenesis.

Long-Term Performance and User Satisfaction With Implanted Neuroprostheses for Upright Mobility After Paraplegia: 2- to 14-Year Follow-Up

OBJECTIVE

To quantify the long-term (>2y) effects of lower extremity (LE) neuroprostheses (NPs) for standing, transfers, stepping, and seated stability after spinal cord injury.

DESIGN

Single-subject design case series with participants acting as their own concurrent controls, including retrospective data review.

SETTING

Hospital-based clinical biomechanics laboratory with experienced (>20y in the field) research biomedical engineers, a physical therapist, and medical monitoring review.

PARTICIPANTS

Long-term (6.2±2.7y) at-home users (N=22; 19 men, 3 women) of implanted NPs for trunk and LE function with chronic (14.4±7.1y) spinal cord injury resulting in full or partial paralysis.

INTERVENTIONS

Technical and clinical performance measurements, along with user satisfaction surveys.

MAIN OUTCOME MEASURES

Knee extension moment, maximum standing time, body weight supported by lower extremities, 3 functional standing tasks, 2 satisfaction surveys, NP usage, and stability of implanted components.

RESULTS

Stimulated knee extension strength and functional capabilities were maintained, with 94% of implant recipients reporting being very or moderately satisfied with their system. More than half (60%) of the participants were still using their implanted NPs for exercise and function for >10min/d on nearly half or more of the days monitored; however, maximum standing times and percentage body weight through LEs decreased slightly over the follow-up interval. Stimulus thresholds were uniformly stable. Six-year survival rates for the first-generation implanted pulse generator (IPG) and epimysial electrodes were close to 90%, whereas those for the second-generation IPG along with the intramuscular and nerve cuff electrodes were >98%.

CONCLUSIONS

Objective and subjective measures of the technical and clinical performances of implanted LE NPs generally remained consistent for 22 participants after an average of 6 years of unsupervised use at home. These findings suggest that implanted LE NPs can provide lasting benefits that recipients value.

Electrical Neuromodulation of the Respiratory System After Spinal Cord Injury

Spinal cord injury (SCI) is a complex and devastating condition characterized by disruption of descending, ascending, and intrinsic spinal circuitry resulting in chronic neurologic deficits. In addition to limb and trunk sensorimotor deficits, SCI can impair autonomic neurocircuitry such as the motor networks that support respiration and cough. High cervical SCI can cause complete respiratory paralysis, and even lower cervical or thoracic lesions commonly result in partial respiratory impairment. Although electrophrenic respiration can restore ventilator-independent breathing in select candidates, only a small subset of affected individuals can benefit from this technology at this moment. Over the past decades, spinal cord stimulation has shown promise for augmentation and recovery of neurologic function including motor control, cough, and breathing. The present review discusses the challenges and potentials of spinal cord stimulation for restoring respiratory function by overcoming some of the limitations of conventional respiratory functional electrical stimulation systems.

The effects of paranodal myelin damage on action potential depend on axonal structure

Biophysical computational models of axons provide an important tool for quantifying the effects of injury and disease on signal conduction characteristics. Several studies have used generic models to study the average behavior of healthy and injured axons; however, few studies have included the effects of normal structural variation on the simulated axon's response to injury. The effects of variations in physiological characteristics on axonal function were mapped by altering the structure of the nodal, paranodal, and juxtaparanodal regions across reported values in three different caliber axons (1, 2, and 5.7 μm). Myelin detachment and retraction were simulated to quantify the effects of each injury mechanism on signal conduction. Conduction velocity was most affected by axonal fiber diameter (89%), while membrane potential amplitude was most affected by nodal length (86%) in healthy axons. Postinjury axonal functionality was most affected by myelin detachment in the paranodal and juxtaparanodal regions when retraction and detachment were modeled simultaneously. The efficacy of simulated potassium channel blockers on restoring membrane potential and velocity varied with axonal caliber and injury type. The structural characteristics of axons affect their functional response to myelin retraction and detachment and their subsequent response to potassium channel blocker treatment.

The Effect of Electrical Stimulation of the Calf Muscle on Leg Fluid Accumulation over a Long Period of Sitting

Leg fluid accumulation during sedentary behaviours such as sitting can lead to leg edema and associated adverse health consequences. This study investigates the use calf muscle electrical stimulation (ES) to reduce seated leg fluid accumulation. Thirteen non-obese, normotensive men (mean age 51 yr.) with sleep apnea were enrolled in the study. Participants first lay supine for 30 minutes to equalize fluid distribution and then sat for 150 minutes. While seated, participants received either active or sham ES of the calf muscles, according to random assignment. Participants returned one-week later to cross over to the other study condition. Leg fluid was measured continuously while sitting using the bioelectrical impedance method. Fluid accumulation in the leg was reduced by more than 40% using active ES, compared to sham ES (∆ = 51.9 ± 8.8 ml vs. ∆ = 91.5 ± 8.9 ml, P < 0.001). In summary, calf muscle ES is an effective method for reducing accumulation of fluid during long sedentary periods and has potential use as a device for preventing leg edema to treat associated health consequences in at-risk groups and settings.

A Clinical Framework for Functional Recovery in a Person With Chronic Traumatic Brain Injury: A Case Study

BACKGROUND AND PURPOSE

This case study describes a task-specific training program for gait walking and functional recovery in a young man with severe chronic traumatic brain injury.

CASE DESCRIPTION

The individual was a 26-year-old man 4 years post-traumatic brain injury with severe motor impairments who had not walked outside of therapy since his injury. He had received extensive gait training prior to initiation of services. His goal was to recover the ability to walk.

INTERVENTION

The primary focus of the interventions was the restoration of walking. A variety of interventions were used, including locomotor treadmill training, electrical stimulation, orthoses, and specialized assistive devices. A total of 79 treatments were delivered over a period of 62 weeks.

OUTCOMES

At the conclusion of therapy, the client was able to walk independently with a gait trainer for approximately 1km (over 3000 ft) and walked in the community with the assistance of his mother using a rocker bottom crutch for distances of 100m (330 ft).

DISCUSSION

Specific interventions were intentionally selected in the development of the treatment plan. The program emphasized structured practice of the salient task, that is, walking, with adequate intensity and frequency. Given the chronicity of this individual's injury, the magnitude of his functional improvements was unexpected.Video Abstract available for additional insights from the Authors (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A175).

Characterization of Volitional Electromyographic Signals in the Lower Extremity After Motor Complete Spinal Cord Injury

BACKGROUND

Previous studies have demonstrated the presence of intact axons across a spinal cord lesion, even in those clinically diagnosed with complete spinal cord injury (SCI). These axons may allow volitional motor signals to be transmitted through the injury, even in the absence of visible muscle contraction.

OBJECTIVE

To demonstrate the presence of volitional electromyographic (EMG) activity below the lesion in motor complete SCI and to characterize this activity to determine its value for potential use as a neuroprosthetic command source.

METHODS

Twenty-four subjects with complete (AIS A or B), chronic, cervical SCI were tested for the presence of volitional below-injury EMG activity. Surface electrodes recorded from 8 to 12 locations of each lower limb, while participants were asked to attempt specific movements of the lower extremity in response to visual and audio cues. EMG trials were ranked through visual inspection, and were scored using an amplitude threshold algorithm to identify channels of interest with volitional motor unit activity.

RESULTS

Significant below-injury muscle activity was identified through visual inspection in 16 of 24 participants, and visual inspection rankings were well correlated to the algorithm scoring.

CONCLUSIONS

The surface EMG protocol utilized here is relatively simple and noninvasive, ideal for a clinical screening tool. The majority of subjects tested were able to produce a volitional EMG signal below their injury level, and the algorithm developed allows automatic identification of signals of interest. The presence of this volitional activity in the lower extremity could provide an innovative new command signal source for implanted neuroprostheses or other assistive technology.

Training an Actor-Critic Reinforcement Learning Controller for Arm Movement Using Human-Generated Rewards

Functional Electrical Stimulation (FES) employs neuroprostheses to apply electrical current to the nerves and muscles of individuals paralyzed by spinal cord injury to restore voluntary movement. Neuroprosthesis controllers calculate stimulation patterns to produce desired actions. To date, no existing controller is able to efficiently adapt its control strategy to the wide range of possible physiological arm characteristics, reaching movements, and user preferences that vary over time. Reinforcement learning (RL) is a control strategy that can incorporate human reward signals as inputs to allow human users to shape controller behavior. In this paper, ten neurologically intact human participants assigned subjective numerical rewards to train RL controllers, evaluating animations of goal-oriented reaching tasks performed using a planar musculoskeletal human arm simulation. The RL controller learning achieved using human trainers was compared with learning accomplished using human-like rewards generated by an algorithm; metrics included success at reaching the specified target; time required to reach the target; and target overshoot. Both sets of controllers learned efficiently and with minimal differences, significantly outperforming standard controllers. Reward positivity and consistency were found to be unrelated to learning success. These results suggest that human rewards can be used effectively to train RL-based FES controllers.

Traumatic spinal cord injury

Traumatic spinal cord injury (SCI) has devastating consequences for the physical, social and vocational well-being of patients. The demographic of SCIs is shifting such that an increasing proportion of older individuals are being affected. Pathophysiologically, the initial mechanical trauma (the primary injury) permeabilizes neurons and glia and initiates a secondary injury cascade that leads to progressive cell death and spinal cord damage over the subsequent weeks. Over time, the lesion remodels and is composed of cystic cavitations and a glial scar, both of which potently inhibit regeneration. Several animal models and complementary behavioural tests of SCI have been developed to mimic this pathological process and form the basis for the development of preclinical and translational neuroprotective and neuroregenerative strategies. Diagnosis requires a thorough patient history, standardized neurological physical examination and radiographic imaging of the spinal cord. Following diagnosis, several interventions need to be rapidly applied, including haemodynamic monitoring in the intensive care unit, early surgical decompression, blood pressure augmentation and, potentially, the administration of methylprednisolone. Managing the complications of SCI, such as bowel and bladder dysfunction, the formation of pressure sores and infections, is key to address all facets of the patient's injury experience.

Review of Epidural Spinal Cord Stimulation for Augmenting Cough after Spinal Cord Injury

Spinal cord injury (SCI) remains a debilitating condition for which there is no cure. In addition to loss of somatic sensorimotor functions, SCI is also commonly associated with impairment of autonomic function. Importantly, cough dysfunction due to paralysis of expiratory muscles in combination with respiratory insufficiency can render affected individuals vulnerable to respiratory morbidity. Failure to clear sputum can aggravate both risk for and severity of respiratory infections, accounting for frequent hospitalizations and even mortality. Recently, epidural stimulation of the lower thoracic spinal cord has been investigated as novel means for restoring cough by evoking expiratory muscle contraction to generate large positive airway pressures and expulsive air flow. This review article discusses available preclinical and clinical evidence, current challenges and clinical potential of lower thoracic spinal cord stimulation (SCS) for restoring cough in individuals with SCI.

Mobile interface for neuroprosthesis control aiming tetraplegic users

This article proposes the development of a mobile interface for controlling a Neuroprosthesis, designed to restore grasp patterns, aiming tetraplegics users at C5 and C6 levels. Human Computer Interface paradigms and usability concepts guide its planning and development to garantee the quality of user's interaction with the system and thus, the sucess and controlability of the neuroprostheses. The number of screens and menus were optimized, thus the user may feel the interface as more intuitive, leading to fast learning and increasing the trust on it.

Application of a paraplegic gait orthosis in thoracolumbar spinal cord injury

Paraplegic gait orthosis has been shown to help paraplegic patients stand and walk, although this method cannot be individualized for patients with different spinal cord injuries and functional recovery of the lower extremities. There is, however, a great need to develop individualized paraplegic orthosis to improve overall quality of life for paraplegic patients. In the present study, 36 spinal cord (below T4) injury patients were equally and randomly divided into control and observation groups. The control group received systematic rehabilitation training, including maintenance of joint range of motion, residual muscle strength training, standing training, balance training, and functional electrical stimulation. The observation group received an individualized paraplegic locomotion brace and functional training according to the various spinal cord injury levels and muscle strength based on comprehensive systematic rehabilitation training. After 3 months of rehabilitation training, the observation group achieved therapeutic locomotion in 8 cases, family-based locomotion in 7 cases, and community-based locomotion in 3 cases. However, locomotion was not achieved in any of the control group patients. These findings suggest that individualized paraplegic braces significantly improve activity of daily living and locomotion in patients with thoracolumbar spinal cord injury.

Fatigue reduction during aggregated and distributed sequential stimulation

INTRODUCTION

Transcutaneous neuromuscular electrical stimulation (NMES) can generate muscle contractions for rehabilitation and exercise. However, NMES-evoked contractions are limited by fatigue when they are delivered "conventionally" (CONV) using a single active electrode. Researchers have developed "sequential" (SEQ) stimulation, involving rotation of pulses between multiple "aggregated" (AGGR-SEQ) or "distributed" (DISTR-SEQ) active electrodes, to reduce fatigue (torque-decline) by reducing motor unit discharge rates. The primary objective was to compare fatigue-related outcomes, "potentiation," "variability," and "efficiency" between CONV, AGGR-SEQ, and DISTR-SEQ stimulation of knee extensors in healthy participants.

METHODS

Torque and current were recorded during testing with fatiguing trains using each NMES type under isometric and isokinetic (180°/s) conditions.

RESULTS

Compared with CONV stimulation, SEQ techniques reduced fatigue-related outcomes, increased potentiation, did not affect variability, and reduced efficiency.

CONCLUSIONS

SEQ techniques hold promise for reducing fatigue during NMES-based rehabilitation and exercise; however, optimization is required to improve efficiency. Muscle Nerve 56: 271-281, 2017.

Semiparametric Identification of Human Arm Dynamics for Flexible Control of a Functional Electrical Stimulation Neuroprosthesis

We present a method to identify the dynamics of a human arm controlled by an implanted functional electrical stimulation neuroprosthesis. The method uses Gaussian process regression to predict shoulder and elbow torques given the shoulder and elbow joint positions and velocities and the electrical stimulation inputs to muscles. We compare the accuracy of torque predictions of nonparametric, semiparametric, and parametric model types. The most accurate of the three model types is a semiparametric Gaussian process model that combines the flexibility of a black box function approximator with the generalization power of a parameterized model. The semiparametric model predicted torques during stimulation of multiple muscles with errors less than 20% of the total muscle torque and passive torque needed to drive the arm. The identified model allows us to define an arbitrary reaching trajectory and approximately determine the muscle stimulations required to drive the arm along that trajectory.