Changes in muscle force following therapeutic electrical stimulation in patients with complete paraplegia

Neuromuscular consequences of spinal cord injury: New mechanistic insights and clinical considerations

The spinal cord facilitates communication between the brain and the body, containing intrinsic systems that work with lower motor neurons (LMNs) to manage movement. Spinal cord injuries (SCIs) can lead to partial paralysis and dysfunctions in muscles below the injury. While traditionally this paralysis has been attributed to disruptions in the corticospinal tract, a growing body of work demonstrates LMN damage is a factor. Motor units, comprising the LMN and the muscle fibers with which they connect, are essential for voluntary movement. Our understanding of their changes post-SCI is still emerging, but the health of motor units is vital, especially when considering innovative SCI treatments like nerve transfer surgery. This review seeks to collate current literature on how SCI impact motor units and explore neuromuscular clinical implications and treatment avenues. SCI reduced motor unit number estimates, and surviving motor units had impaired signal transmission at the neuromuscular junction, force-generating capacity, and excitability, which have the potential to recover chronically, yet the underlaying mechanisms are unclear. Furthermore, electrodiagnostic evaluations can aid in assessing the health lower and upper motor neurons, identify suitable targets for nerve transfer surgeries, and detect patients with time sensitive injuries. Lastly, many electrodiagnostic abnormalities occur in both chronic and acute SCI, yet factors contributing to these abnormalities are unknown. Future studies are required to determine how motor units adapt following SCI and the clinical implications of these adaptations.

Effectiveness of FES-supported leg exercise for promotion of paralysed lower limb muscle and bone health-a systematic review

Leg exercises through standing, cycling and walking with/without FES may be used to preserve lower limb muscle and bone health in persons with physical disability due to SCI. This study sought to examine the effectiveness of leg exercises on bone mineral density and muscle cross-sectional area based on their clinical efficacy in persons with SCI. Several literature databases were searched for potential eligible studies from the earliest return date to January 2022. The primary outcome targeted was the change in muscle mass/volume and bone mineral density as measured by CT, MRI and similar devices. Relevant studies indicated that persons with SCI that undertook FES- and frame-supported leg exercise exhibited better improvement in muscle and bone health preservation in comparison to those who were confined to frame-assisted leg exercise only. However, this observation is only valid for exercise initiated early (i.e., within 3 months after injury) and for ≥30 min/day for ≥ thrice a week and for up to 24 months or as long as desired and/or tolerable. Consequently, apart from the positive psychological effects on the users, leg exercise may reduce fracture rate and its effectiveness may be improved if augmented with FES.

Effects of Repetitive Peripheral Magnetic Stimulation on Shoulder Subluxations Caused by Stroke: A Preliminary Study

OBJECTIVES

Shoulder subluxation is a common problem after stroke. It causes shoulder pain that affects activities of daily living. This study aimed to investigate the effect of repetitive peripheral magnetic stimulation on shoulder subluxation after stroke.

METHODS

We enrolled 12 consecutive patients who, as a result of stroke, suffered shoulder subluxations, measuring at half of a fingerbreadth or more. All subjects underwent conventional rehabilitation, as well as repetitive peripheral magnetic stimulation of their supraspinatus, posterior deltoid, and infraspinatus muscles. We assessed the following parameters: shoulder subluxation, evaluated as the acromio-humeral interval using measurements taken from X-rays; shoulder pain, evaluated using the Numerical Rating Scale; the active range of motion of shoulder abduction; and the motor impairment of the upper extremities, evaluated using the upper extremity of the Fugl-Meyer Assessment scale.

RESULTS

The acromio-humeral interval before treatment was 22.8 ± 5.7 mm (mean ± SD). It significantly decreased to 19.6 ± 7.0 mm (p = 0.004) after treatment. Shoulder pain (p = 0.039), active range of motion of shoulder abduction (p = 0.016), and total (p = 0.005), subscale A (p = 0.005), and subscale C (p = 0.008) Fugl-Meyer Assessment scores also improved significantly after treatment.

CONCLUSIONS

Repetitive peripheral magnetic stimulation effectively reduced shoulder subluxations and shoulder pain caused by stroke and improved voluntary upper-limb movements in stroke patients.

Repetitive Peripheral Magnetic Stimulation for Strengthening of the Suprahyoid Muscles: A Randomized Controlled Trial

OBJECTIVE

Head lift exercise is a widely known form of training in the rehabilitation of patients with dysphagia. This study aimed to compare muscular strength reinforcement training of the suprahyoid muscles using repetitive peripheral magnetic stimulation (rPMS) with head lift exercises in a randomized controlled trial.

MATERIALS AND METHODS

Twenty-four healthy adults were randomly assigned to either the magnetic stimulation group (M group) or the head lift exercise group (H group). Both groups underwent training five days a week for two weeks. The primary outcome was the cervical flexor strength, and secondary outcomes were jaw-opening force, tongue pressure, muscle fatigue of the hyoid and laryngeal muscles, displacement of the hyoid bone and opening width of the upper esophageal sphincter (UES) while swallowing 10 mL of liquid, training performance rate, and pain.

RESULTS

No dropouts were reported during the two-week intervention period. Cervical flexor strength significantly increased solely in the M group. Tongue pressure significantly improved in both groups. There were no significant differences in the jaw-opening force, median frequency rate of the anterior belly of the digastric muscle, sternohyoid muscle, sternocleidomastoid muscle, anterior and superior hyoid bone displacement, and UES opening width in both groups.

CONCLUSIONS

Two-week rPMS of the suprahyoid muscles increased the strength of these muscles compared with the head lift exercise during the same period.

Advanced Assessment of the Upper Limb in Tetraplegia: A Three-Tiered Approach to Characterizing Paralysis

Background: More than half of all individuals who sustain a spinal cord injury (SCI) experience some degree of impairment in the upper limb. Functional use of the arm and hand is of paramount importance to these individuals. Fortunately, the number of clinical trials and advanced interventions targeting upper limb function are increasing, generating optimism for improved recovery and restoration after SCI. New interventions for restoring function and improving recovery require more detailed examination of the motor capacities of the upper limb. Objectives: The purpose of this article is to introduce a three-tiered approach to evaluating motor function, with specific attention to the characteristics of weak and fully paralyzed muscles during acute rehabilitation. The three tiers include (1) evaluation of voluntary strength via manual muscle testing, (2) evaluation of lower motor neuron integrity in upper motor neuron-paralyzed muscles using surface electrical stimulation, and (3) evaluation of latent motor responses in paralyzed muscles that exhibit a strong response to electrical stimulation, using surface electromyographic recording electrodes. These characteristics contribute important information that can be utilized to mitigate potential secondary conditions such as contractures and identify effective interventions such as activity-based interventions or reconstructive procedures. Our goal is to encourage frontline clinicians - occupational and physical therapists who are experts in muscle assessment - to consider a more in-depth analysis of paralysis after SCI. Conclusion: Given the rapid advancements in SCI research and clinical interventions, it is critical that methods of evaluation and classification evolve. The success or failure of these interventions may depend on the specific characteristics identified in our three-tiered assessment. Without this assessment, the physiological starting point for each individual is unknown, adding significant variability in the outcomes of these interventions.

Impact of an implanted neuroprosthesis on community ambulation in incomplete SCI

OBJECTIVE

Test the effect of a multi-joint control with implanted electrical stimulation on walking after spinal cord injury (SCI).

DESIGN

Single subject research design with repeated measures.

SETTING

Hospital-based biomechanics laboratory and user assessment of community use.

PARTICIPANTS

Female with C6 AIS C SCI 30 years post injury.

INTERVENTIONS

Lower extremity muscle activation with an implanted pulse generator and gait training.

OUTCOME MEASURES

Walking speed, maximum distance, oxygen consumption, upper extremity (UE) forces, kinematics and self-assessment of technology.

RESULTS

Short distance walking speed at one-year follow up with or without stimulation was not significantly different from baseline. However, average walking speed was significantly faster (0.22 m/s) with stimulation over longer distances than volitional walking (0.12 m/s). In addition, there was a 413% increase in walking distance from 95 m volitionally to 488 m with stimulation while oxygen consumption and maximum upper extremity forces decreased by 22 and 16%, respectively. Stimulation also produced significant (P ≤ 0.001) improvements in peak hip and knee flexion, ankle angle at foot off and at mid-swing.

CONCLUSION

An implanted neuroprosthesis enabled a subject with incomplete SCI to walk longer distances with improved hip and knee flexion and ankle dorsiflexion resulting in decreased oxygen consumption and UE support. Further research is required to determine the robustness, generalizability and functional implications of implanted neuroprostheses for community ambulation after incomplete SCI.

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.

The effects of electrical stimulation on body composition and metabolic profile after spinal cord injury--Part II

Diet and exercise are cornerstones in the management of obesity and associated metabolic complications, including insulin resistance, type 2 diabetes, and disturbances in the lipid profile. However, the role of exercise in managing body composition adaptations and metabolic disorders after spinal cord injury (SCI) is not well established. The current review summarizes evidence about the efficacy of using neuromuscular electrical stimulation or functional electrical stimulation in exercising the paralytic lower extremities to improve body composition and metabolic profile after SCI. There are a number of trials that investigated the effects on muscle cross-sectional area, fat-free mass, and glucose/lipid metabolism. The duration of the intervention in these trials varied from 6 weeks to 24 months. Training frequency ranged from 2 to 5 days/week. Most studies documented significant increases in muscle size but no noticeable changes in adipose tissue. While increases in skeletal muscle size after twice weekly training were greater than those trials that used 3 or 5 days/week, other factors such as differences in the training mode, i.e. resistance versus cycling exercise and pattern of muscle activation may be responsible for this observation. Loading to evoke muscle hypertrophy is a key component in neuromuscular training after SCI. The overall effects on lean mass were modest and did not exceed 10% and the effects of training on trunk or pelvic muscles remain unestablished. Most studies reported improvement in glucose metabolism with the enhancement of insulin sensitivity being the major factor following training. The effect on lipid profile is unclear and warrants further investigation.

A randomized trial of functional electrical stimulation for walking in incomplete spinal cord injury: effects on body composition

OBJECTIVE

To evaluate the effects of functional electrical stimulation (FES)-assisted walking on body composition, compared to a non-FES exercise program in individuals with a spinal cord injury (SCI).

DESIGN

Parallel-group randomized controlled trial.

METHODS

Individuals with chronic (≥ 18 months) incomplete SCI (level C2 to T12, AIS C or D) were recruited and randomized to FES-assisted walking (intervention), or aerobic and resistance training (control) sessions thrice-weekly for 16 weeks. Whole body and leg lean mass and whole body fat mass, measured with dual-energy X-ray absorptiometry, and lower-limb muscle cross-sectional area (CSA) and fat CSA, measured with peripheral computed tomography were assessed at baseline, 4 months, and 12 months. Intention-to-treat analyses using repeated measures general linear models were used to assess between-group differences.

RESULTS

Thirty-four individuals were randomized (17 per group); 27 remained at 12 months. There were no significant main effects of FES-assisted walking on body composition variables in intention-to-treat analyses with group means. There was a significant group-by-time interaction for muscle area from baseline to 12 months (P = 0.04). Intention-to-treat analysis of muscle area change scores between baseline and 12 months revealed a significant difference between groups (mean (SD) muscle area change score 212 (517) mm(s) for FES, -136 (268) mm(s) for control, P = 0.026). There were 13 side effects or adverse events deemed related to study participation (7 intervention, 5 control); most were resolved with modifications to the protocol. One fainting episode resulted in a hospital visit and study withdrawal.

CONCLUSIONS

Thrice-weekly FES-assisted walking exercise over 4 months did not result in a change in body composition in individuals with chronic, motor incomplete C2 to T12 SCI (AIS classification C and D). However, longer-term follow-up revealed that it might maintain muscle area.

The effects of neuromuscular electrical stimulation for dysphagia in opercular syndrome: a case study

A 76-year-old man with opercular syndrome characterized by complete bilateral loss of voluntary control of facial, lingual, pharyngeal and masticatory muscles is presented with focus on the severe dysphagia. Three years earlier the patient had experienced two strokes resulting in opercular syndrome with severe dysphagia. Despite initial logopedic dysphagia treatment, swallowing did not improve. A new treatment for dysphagia, consisting of neuromuscular electrical stimulation was applied on the patient. He returned to oral feeding. Clinical and treatment observations are reported.

Transcutaneous neuromuscular electrical stimulation (VitalStim) curative therapy for severe dysphagia: myth or reality?

OBJECTIVES

VitalStim therapy was approved by the US Food and Drug Administration in 2001 for the treatment of dysphagia through the application of neuromuscular electrical stimulation to cervical swallowing muscles. This approval was based upon submission of data on more than 800 patients who received this therapy collected by the principal developer and patent-holder of the device. The therapy is marketed as successful in restoring long-term swallowing function in 97.5% of dysphagic patients past the point of requiring a feeding tube and as significantly better than existing therapies. More than 2,500 speech-language pathologists have taken the certification course, and thousands of devices have been sold. To date, however, aside from the developer's own studies, there are no peer-reviewed publications supporting these claims. We sought to evaluate the effectiveness of VitalStim therapy in a heterogeneous group of dysphagic patients.

METHODS

We performed a retrospective analysis of 18 patients who received this therapy at an urban tertiary referral center. All patients underwent pretherapy evaluation by speech-language pathologists, including modified barium swallow and/or functional endoscopic evaluation of swallowing and clinical evaluation of swallowing that included assessment of laryngeal elevation, diet tolerance, and swallowing delay, and were then assigned an overall dysphagia severity score. After therapy, all patients underwent the same assessments. Twelve of the 18 also underwent a functional swallowing telephone survey months (range, 1 to 21 months) after their therapy to assess whether the improvement was worthwhile and sustained.

RESULTS

Eleven of the 18 patients (61%) demonstrated some improvement in their swallowing. Six of the 18 patients (33%) were improved enough to no longer require a feeding tube. However, of the 5 patients categorized as having "severe dysphagia" before therapy, only 2 showed any improvement, and these patients still required a feeding tube for adequate nutrition. Telephone surveys did confirm that those who improved with their therapy seemed to maintain their progress and that most patients were satisfied with their therapy.

CONCLUSIONS

VitalStim therapy seems to help those with mild to moderate dysphagia. However, the patients with the most severe dysphagia in our study did not gain independence from their feeding tubes. The authors conclude that VitalStim therapy clearly has a place in the management of dysphagia, but that the most severely afflicted are unlikely to gain dramatic improvement.

Bone loss and muscle atrophy in spinal cord injury: epidemiology, fracture prediction, and rehabilitation strategies

Individuals with spinal cord injury (SCI) often experience bone loss and muscle atrophy. Muscle atrophy can result in reduced metabolic rate and increase the risk of metabolic disorders. Sublesional osteoporosis predisposes individuals with SCI to an increased risk of low-trauma fracture. Fractures in people with SCI have been reported during transfers from bed to chair, and while being turned in bed. The bone loss and muscle atrophy that occur after SCI are substantial and may be influenced by factors such as completeness of injury or time postinjury. A number of interventions, including standing, electrically stimulated cycling or resistance training, and walking exercises have been explored with the aim of reducing bone loss and/or increasing bone mass and muscle mass in individuals with SCI. Exercise with electrical stimulation appears to increase muscle mass and/or prevent atrophy, but studies investigating its effect on bone are conflicting. Several methodological limitations in exercise studies with individuals with SCI to date limit our ability to confirm the utility of exercise for improving skeletal status. The impact of standing or walking exercises on muscle and bone has not been well established. Future research should carefully consider the study design, skeletal measurement sites, and the measurement techniques used in order to facilitate sound conclusions.

The effects of therapeutic electric stimulation on acute muscle atrophy in rats after spinal cord injury

OBJECTIVE

To evaluate the effects of electric stimulation in preventing acute muscle atrophy after spinal cord transection in rats.

DESIGN

A randomized experimental design.

SETTING

Animal facilities for experimental medicine.

ANIMALS

Fifty-six adult male Wistar rats assigned to control, low-frequency, and high-frequency groups.

INTERVENTIONS

The rats were implanted with a percutaneous intramuscular electrode in the vicinity of the peroneal nerve; then the spinal cord was transected in a T9 level. The stimulation frequency was low (20Hz) or high (100Hz). The stimulation cycle was 4 seconds of stimulation every 8 seconds.

MAIN OUTCOME MEASUREMENTS

The lesser fiber diameters from type 1, 2A, and 2B muscle fibers were measured. In another assessment, maximal contraction force was measured. The muscle force produced at 20 and 100Hz was expressed as increasing values in tetanic force.

RESULTS

Comparison between nonstimulated and stimulated tibialis anterior muscles found that atrophy of type 1 fibers (p < .01) and type 2B fibers (p < .05) at both stimulated levels and of type 2A fibers at 100-Hz level (p < .05) was prevented by therapeutic electric stimulation (TES). There were significant differences in the size of muscle fiber diameter between nonstimulated and stimulated muscles at 100Hz in type 2A and, markedly, in type 2B. The increasing value of muscle force was significantly greater at 100Hz than at 20Hz (p < .05). No significant histologic differences were observed between high- and low-frequency stimulated fibers of any of the 3 muscle types.

CONCLUSIONS

Acute atrophy of muscle fibers was more effectively prevented by high-frequency stimulation (100Hz) than by no stimulation or low-frequency stimulation (20Hz). The increasing value of muscle force was significantly greater at high-frequency than low-frequency stimulation, suggesting that the clinical application of high-frequency stimulation in acute spinal cord injury should be studied.

Implanted functional electrical stimulation system for mobility in paraplegia: a follow-up case report

A 16-channel functional electrical stimulation (FES) system has been implanted in a person with T10 paraplegia for over a year. The system consists of two eight-channel radio frequency controlled receiver-stimulators delivering stimuli through a network of 14 epimysial and two intramuscular electrodes. Using this system and a walker for support, the subject was able to stand up for 8 min and walk regularly for 20 m. The standing duration was limited by arm fatigue since upper extremities supported an average of 25% of body weight. This was due to suboptimal hip extension and some undesired recruitment of rectus femoris and sartorius with stimulation of quadriceps electrodes. The left quadriceps exhibited rapid fatigue that limited walking distance and duration. The metabolic energy requirements were well within the aerobic limits of the sedentary paraplegic population. At one-year follow-up evaluation all electrodes are functional except one intramuscular electrode. The implant caused no adverse physiological effects and the individual reported health benefits such as increased energy and overall fitness as a result of the FES system use. With further improvements in muscle response through innovative surgical techniques, the 16-channel implanted FES system can be a viable addition to exercise and mobility function in persons with paraplegia.

Hybrid functional electrical stimulation for energy-efficient restoration of standing-up motion

OBJECTIVE

To find the most energy-efficient standing-up motion for quadriceps and to restore that motion in a person with complete paraplegia by using hybrid functional electrical stimulation.

DESIGN

Nonrandomized control trial.

SETTING

A referral center and institutional practice providing outpatient care.

PARTICIPANTS

Twenty-nine volunteer samples were used to collect normal data. One patient with complete paraplegia received treatment for the restoration of standing-up motion.

MAIN OUTCOME MEASUREMENTS

Joint angles and ground reaction forces were investigated during the standing-up motion with arms crossed in front of the chest with an ankle-foot orthosis set at various angles. The electromyogram (EMG) was performed during the standing-up motion with and without the orthosis. The energy costs of quadriceps during the standing-up motion were calculated using a mathematical model. Standing-up motion in a person with complete paraplegia was restored and then analyzed by measuring the vertical ground reaction force and the hip and knee angles.

RESULTS

Quadriceps energy cost was lowest (p < .05) in subjects wearing the ankle-foot orthosis set at neutral with a flat sole line. In the integrated EMG the peak value of rectus femoris contraction was larger with the orthosis than without it (p < .05). A patient with complete paraplegia was able to stand up smoothly from a wheelchair based on stimulation patterns obtained from healthy subjects.

CONCLUSIONS

Energy-efficient standing-up motion in a patient with complete paraplegia was restored when the patient used an ankle-foot orthosis set at neutral with a flat sole line.

Electrophysiologic evaluation of denervated muscles in incomplete paraplegia using macro electromyography

OBJECTIVE

To evaluate denervated muscles in persons with incomplete paraplegia due to thoracolumbar spinal injury (TLSI) using macro electromyography in determining indications for functional electrical stimulation (FES).

DESIGN

A randomized clinical trial and a criterion standard.

SETTING

A department of orthopedic surgery in a university hospital.

PATIENTS AND OTHER PARTICIPANTS

Eighteen patients with incomplete paraplegia, including 11 with TSLI, and 50 healthy adults.

INTERVENTION

Area and amplitude of macro motor unit potential (macro MUP) were measured at the tibialis anterior, the vastus lateralis, and the vastus medialis. The normal limits of macro MUP parameters were defined based on values from healthy subjects. Abnormal denervated muscles were detected by macro EMG and conventional EMG in paralytic patients. The correlation between macro MUP parameter values and muscle forces of the tibialis anterior and quadriceps femoris induced by electrical stimulation was analyzed.

MAIN OUTCOME MEASURES

The number of abnormal muscles, parameter values, and muscle force induced by electrical stimulation.

RESULTS

Abnormal muscles were found only in the TLSI patients and 13 abnormal muscles were detected by macro EMG only. The abnormal muscles defined by macro EMG showed insufficient contraction induced by electrical stimulation. The increase of parameter value negatively correlated with the muscle force (tibialis anterior area r=-.797, amplitude r=-.866; quadriceps area r=-.866, amplitude r=-.893; p < .001).

CONCLUSIONS

These results suggest that macro EMG is useful in detecting denervated muscles, in determining indications for FES, and in predicting FES effects before implantation of electrodes.

An electrical knee lock system for functional electrical stimulation

An electrical knee lock system that can be combined with functional electrical stimulation was designed for paraplegic patients. This knee system unlocks the knee electrically and allows knee flexion during the swing phase of the gait. When the knee is extended by electrical stimulation of the knee extensors, the knee is automatically locked by the weight of the locking bar, and the stimulation of the knee extensors is stopped. Since the knee extensors are stimulated for only a short period, muscle fatigue of the knee extensors seldom occurs. We applied this system to a T8 completely paraplegic patient. Standing-up, standing, walking, and sitting-down motions were all restored by our hybrid system. No electrical stimulation was necessary during standing, and the knee extensors were stimulated during only a small percentage of the 1-gait cycle.