Development of network-based multichannel neuromuscular electrical stimulation system for stroke rehabilitation

A new modular neuroprosthesis suitable for hybrid FES-robot applications and tailored assistance

BACKGROUND

To overcome the application limitations of functional electrical stimulation (FES), such as fatigue or nonlinear muscle response, the combination of neuroprosthetic systems with robotic devices has been evaluated, resulting in hybrid systems that have promising potential. However, current technology shows a lack of flexibility to adapt to the needs of any application, context or individual. The main objective of this study is the development of a new modular neuroprosthetic system suitable for hybrid FES-robot applications to meet these needs.

METHODS

In this study, we conducted an analysis of the requirements for developing hybrid FES-robot systems and reviewed existing literature on similar systems. Building upon these insights, we developed a novel modular neuroprosthetic system tailored for hybrid applications. The system was specifically adapted for gait assistance, and a technological personalization process based on clinical criteria was devised. This process was used to generate different system configurations adjusted to four individuals with spinal cord injury or stroke. The effect of each system configuration on gait kinematic metrics was analyzed by using repeated measures ANOVA or Friedman's test.

RESULTS

A modular NP system has been developed that is distinguished by its flexibility, scalability and personalization capabilities. With excellent connection characteristics, it can be effectively integrated with robotic devices. Its 3D design facilitates fitting both as a stand-alone system and in combination with other robotic devices. In addition, it meets rigorous requirements for safe use by incorporating appropriate safety protocols, and features appropriate battery autonomy, weight and dimensions. Different technological configurations adapted to the needs of each patient were obtained, which demonstrated an impact on the kinematic gait pattern comparable to that of other devices reported in the literature.

CONCLUSIONS

The system met the identified technical requirements, showcasing advancements compared to systems reported in the literature. In addition, it demonstrated its versatility and capacity to be combined with robotic devices forming hybrids, adapting well to the gait application. Moreover, the personalization procedure proved to be useful in obtaining various system configurations tailored to the diverse needs of individuals.

Revolutionizing motor dysfunction treatment: A novel closed-loop electrical stimulator guided by multiple motor tasks with predictive control

Functional electrical stimulation (FES) has been demonstrated as a viable method for addressing motor dysfunction in individuals affected by stroke, spinal cord injury, and other etiologies. By eliciting muscle contractions to facilitate joint movements, FES plays a crucial role in fostering the restoration of motor function compromised nervous system. In response to the challenge of muscle fatigue associated with conventional FES protocols, a novel biofeedback electrical stimulator incorporating multi-motor tasks and predictive control algorithms has been developed to enable adaptive modulation of stimulation parameters. The study initially establishes a Hammerstein model for the stimulated muscle group, representing a time-varying relationship between the stimulation pulse width and the root mean square (RMS) of the surface electromyography (sEMG). An online parameter identification algorithm utilizing recursive least squares is employed to estimate the time-varying parameters of the Hammerstein model. Predictive control is then implemented through feedback corrections based on the comparison between predicted and actual outputs, guided by an optimization objective function. The integration of predictive control and roll optimization enables closed-loop control of muscle stimulation. The motor training tasks of elbow flexion and extension, wrist flexion and extension, and five-finger grasping were selected for experimental validation. The results indicate that the model parameters were accurately identified, with a RMS error of 3.83 % between actual and predicted values. Furthermore, the predictive control algorithm, based on the motor tasks, effectively adjusted the stimulus parameters to ensure that the stimulated muscle groups can achieve the desired sEMG characteristic trajectory. The biofeedback electrical stimulator that was developed has the potential to assist patients experiencing motor dysfunction in achieving the appropriate joint movements. This research provides a foundation for a novel intelligent electrical stimulation model.

Effects of programmed flexor-extensor alternating electrical acupoint stimulation on upper limb motor functional reconstruction after stroke: study protocol for a double-blind, randomized controlled trial

BACKGROUND

Stroke's prevalence and morbidity are increasing (Guano, et al. Neuro 89:53-61, 2017), and limb motor dysfunction is left in most patients (Gittler, et al. JAMA 319:820-821, 2018). Particularly, the rehabilitation of upper limbs is more difficult and time-consuming (Borges, et al. The Cochrane database of systematic reviews 10:CD011887, 2018).

METHODS

A double-blind randomized controlled trial (RCT) will be conducted to investigate whether a new functional electrical stimulation (FES) combined with acupoint therapy is more effective in the rehabilitation of upper limb motor dysfunction after stroke. Patients who meet the inclusion criteria will be randomly divided into two groups: programmed flexor-extensor alternating electrical acupoint stimulation group (PES group) and conventional flexor-extensor alternating electrical acupoint stimulation group (CES group), which will be treated for 3 weeks. The primary outcome measures are electroencephalogram (EEG) and surface electromyogram (sEMG). The secondary outcome variables include MBI (modified Barthel index), China Stroke Scale (CSS), FMA-U (Fugl-Meyer assessment upper limb), MMT (manual muscle testing), and Brunnstrom.

DISCUSSION

The results of this study are expected to verify the efficacy of PES therapy in the rehabilitation of upper limb motor function after stroke. This may promote the widespread use of the therapy in hospitals, communities, and homes for early and continuous treatment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05333497. Registered on April 11, 2022.

STIMGRASP: A Home-Based Functional Electrical Stimulator for Grasp Restoration in Daily Activities

Thousands of people currently suffer from motor limitations caused by SCI and strokes, which impose personal and social challenges. These individuals may have a satisfactory recovery by applying functional electrical stimulation that enables the artificial restoration of grasping after a muscular conditioning period. This paper presents the STIMGRASP, a home-based functional electrical stimulator to be used as an assistive technology for users with tetraplegia or hemiplegia. The STIMGRASP is a microcontrolled stimulator with eight multiplexed and independent symmetric biphasic constant current output channels with USB and Bluetooth communication. The system generates pulses with frequency, width, and maximum amplitude set at 20 Hz, 300 µs/phase, and 40 mA (load of 1 kΩ), respectively. It is powered by a rechargeable lithium-ion battery of 3100 mAh, allowing more than 10 h of continuous use. The development of this system focused on portability, usability, and wearability, resulting in portable hardware with user-friendly mobile app control and an orthosis with electrodes, allowing the user to carry out muscle activation sequences for four grasp modes to use for achieving daily activities.

A Pilot Study of Synergy-Based FES for Upper-Extremity Poststroke Rehabilitation

A previous study indicated that synergy-based functional electrical stimulation (FES) may improve instantaneous upper-limb motor performance for stroke survivors. However, it remains unclear whether the improvements will sustain over time to achieve functional gains associated with a task-oriented training (TOT). This pilot study was designed to investigate whether there is any promising sign of functional benefits. A TOT protocol with repeated forward and lateral reaching movements assisted by synergy-based FES was conducted in 16 patients (9 FES, 7 Sham) with post-stroke hemiparesis. FES stimuli were applied to 7 upper-extremity muscles of elbow and shoulder during patient movements. Envelopes of stimuli were individualized by re-composing the muscle synergies extracted from a healthy subject. After a five-day training for one hour each day, synergy-based FES induced higher increases in Fugl-Meyer scores (6.67±5.20) than did the Sham (2.00±2.38, p<0.05). Peak velocity of forward reaching movements increased with a slope 73% steeper in FES group than Sham. In lateral reaching movements, the change in synergy similarity correlated with the change in elbow flexion for the FES group, but not the Sham group. Our results indicate that synergy-based FES therapy induced clinically traceable signs of improvements in poststroke motor performance. The muscle activation in patients also showed promising sign of alteration by FES. Results suggest that a larger scale clinical trial of synergy-based FES may be feasible towards an individualized therapeutic regimen.

Automated functional electrical stimulation training system for upper-limb function recovery in poststroke patients

BACKGROUND

This paper describes the design and test of an automated functional electrical stimulation (FES) system for poststroke rehabilitation training. The aim of automated FES is to synchronize electrically induced movements to assist residual movements of patients.

METHODS

In the design of the FES system, an accelerometry module detected movement initiation and movement performed by post-stroke patients. The desired movement was displayed in visual game module. Synergy-based FES patterns were formulated using a normal pattern of muscle synergies from a healthy subject. Experiment 1 evaluated how different levels of trigger threshold or timing affected the variability of compound movements for forward reaching (FR) and lateral reaching (LR). Experiment 2 explored the effect of FES duration on compound movements.

RESULTS

Synchronizing FES-assisted movements with residual voluntary movements produced more consistent compound movements. Matching the duration of synergy-based FES to that of patients could assist slower movements of patients with reduced RMS errors.

CONCLUSIONS

Evidence indicated that synchronization and matching duration with residual voluntary movements of patients could improve the consistency of FES assisted movements. Automated FES training can reduce the burden of therapists to monitor the training process, which may encourage patients to complete the training.

Customization of Synergy-Based FES for Post-Stroke Rehabilitation of Upper-Limb Motor Functions

Functional Electrical Stimulation (FES) provides a promising technology for rehabilitation of upper-limb motor functions following stroke. It enables activation of individual muscles to assist restoration of impaired muscle synergies toward normal patterns. However, there lacks a systematic approach to optimize the FES stimulation patterns delivered to patients with stroke. Our preliminary work demonstrated that it is feasible to use muscle synergy patterns to guide the generation of FES patterns. Here, we present the methodology of customizing synergy-based FES using parameterized formulae with three strategies: weight-sensitive, variability-sensitive, and duration-sensitive. Each of them is comprised of two parameter sets, which represent different directions of parameter search. Two patients with ischemic stroke were recruited to participate in the preliminary test of these strategies. Preliminary results indicate that all strategies could increase the peak velocity in reaching movements, but only the "variability-sensitive" strategy restrained unwanted shoulder excursions. This pilot study demonstrates the feasibility to explore in the parameter space the directions, along which the clinical benefit of synergy-based FES can be tracked and continuously optimized.

The use of functional electrical stimulation to improve upper limb function in children with hemiplegic cerebral palsy: A feasibility study

Background

Grasping and manipulating objects are common problems for children with hemiplegic cerebral palsy. Multichannel-functional electrical stimulation may help facilitate upper limb movements and improve function.

Objective

To evaluate the feasibility of multichannel-functional electrical stimulation to improve grasp and upper limb function in children with hemiplegic cerebral palsy to inform the development of a clinical trial.

Methods

A prospective pre-/post-test/follow-up (six months) design with three children, aged 6–13 years, was used. Multichannel-functional electrical stimulation (mFES) was applied to the hemiplegic upper limb for up to 48 sessions over 16 weeks. Feasibility indicators included recruitment of participants and adherence rates, safety, and discomfort/pain. Effectiveness was assessed using the grasp domain of the Quality of Upper Extremity Skills Test, and other secondary clinical outcome measures with “success” criteria set a priori.

Results

Participant recruitment target was not met but adherence was high, and multichannel-functional electrical stimulation was found to be safe and comfortable. Of the three participants, two improved in grasp at post-test, whereas one child’s ability deteriorated. Only one child met success criteria on most outcomes at post-test.

Conclusions

Feasibility indicators met success criteria, except for participant recruitment. Treatment effectiveness was mixed. A future case comparison investigation with a larger but more selected sample is suggested.

Development of a closed-loop system for tremor suppression in patients with Parkinson's disease

More than 70% of patients suffering Parkinson's disease (PD) exhibit resting tremor in their extremities, hampering their ability to perform daily activities. Based on our earlier studies on corticospinal transmission of tremor signals [10,11], we hypothesize that cutaneous afferents evoked by surface stimulation can produce an inhibitory effect on propriospinal neurons (PN), which in turn will suppress tremor signals passing through the PN. This paper presents the development of a closed-loop system for tremor suppression by transcutaneous electrical nerve stimulation (TENS) of sensory fibers beneath the skin. The closed-loop system senses EMGs of forearm muscles, and detects rhythmic bursting in the EMG signal. When a tremor is detected by the system, a command signal triggers a stimulator to output a train of bi-phasic, current regulated pulses to a pair of surface electrodes. The stimulation electrode is placed on the dorsal hand skin near the metacarpophalangeal joint of index finger, which is innervated by the superficial radial nerve that projects an inhibitory afferent to PNs of forearm muscles. We tested the closed-loop system in 3 normal subjects to verify the algorithm and in 2 tremor dominated PD subjects for feasibility of tremor detecting and suppression. Preliminary results indicate that the closed-loop system can detect tremor in all subjects, and tremor in PD patients was suppressed significantly by electrical stimulation of cutaneous afferents.

Analysis of muscle synergy for evaluation of task-specific performance in stroke patients

Muscle synergy represents a central neural module that organizes and activates a group of muscles when performing a certain task. However, whether muscle synergy is a good physiological indicator of motor ability in task performance for patients suffering stroke is not clear. The purpose of this study is to understand how information of task-specific muscle synergy in healthy subjects and patients post stroke can be used to evaluate their motor ability, and further to assist motor rehabilitation for stroke patients. Electromyography (EMG) signals and movement kinematics in reaching tasks were recorded in 5 healthy subjects and 4 stroke patients. Muscle synergies were extracted from EMGs and compared cross healthy and stroke subjects. Normal synergies displayed a characteristic pattern common in healthy subjects. But pathological synergies in stroke subjects lacked the characteristics of normal synergy without a common component, implicating varying extent of damage to the motor module due to lesion in cerebral circuits. Further analysis in stroke subjects showed that pathological patterns of synergy in stroke subjects corresponded to the abnormality in their movement control compared with healthy subjects. Data showed that task-specific muscle synergy did reveal a positive correlation to the ability of neural control of tasks. It was further observed that task-specific synergy was changed towards the normal pattern after intervention with functional electrical stimulation in patients post stroke.

Evaluation of Functional Correlation of Task-Specific Muscle Synergies with Motor Performance in Patients Poststroke

The central nervous system produces movements by activating specifically programmed muscle synergies that are also altered with injuries in the brain, such as stroke. In this study, we hypothesize that there exists a positive correlation between task-specific muscle synergy and motor functions at joint and task levels in patients following stroke. The purpose here is to define and evaluate neurophysiological metrics based on task-specific muscle synergy for assessing motor functions in patients. A patient group of 10 subjects suffering from stroke and a control group of nine age-matched healthy subjects were recruited to participate in this study. Electromyography (EMG) signals and movement kinematics were recorded in patients and control subjects while performing arm reaching tasks. Muscle synergies of individual patients were extracted off-line from EMG records of each patient, and a baseline pattern of muscle synergy was obtained from the pooled EMG data of all nine control subjects. Peak velocities and movement durations of each reaching movement were computed from measured kinematics. Similarity indices of matching components to those of the baseline synergy were defined by synergy vectors and time profiles, respectively, as well as by a combined similarity of vector and time profile. Results showed that pathological synergies of patients were altered from the characteristics of baseline synergy with missing components, or varied vector patterns and time profiles. The kinematic performance measured by peak velocities and movement durations was significantly poorer for the patient group than the control group. In patients, all three similarity indices were found to correlate significantly to the kinematics of movements for the reaching tasks. The correlation to the Fugl-Meyer score of arm was the highest with the vector index, the lowest with the time profile index, and in between with the combined index. These findings illustrate that the analysis of task-specific muscle synergy can provide valuable insights into motor deficits for patients following stroke, and the task-specific similarity indices are useful neurophysiological metrics to predict the function of neuromuscular control at the joint and task levels for patients.