The effects of long-term FES-assisted walking on intrinsic and reflex dynamic stiffness in spastic spinal-cord-injured subjects

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.

Paired associative stimulation on the soleus H-Reflex using motor point and peripheral nerve stimulation

Paired associative stimulation (PAS) has been shown to modulate the corticospinal excitability via spike timing dependent plasticity (STDP). In this study, we aimed to suppress the spinal H-Reflex using PAS. We paired two stimulation modalities, i.e., peripheral nerve stimulation (PNS) and motor point stimulation (MPS). We used PNS to dominantly activate the Ia sensory axon, and we used MPS to dominantly activate the α-motoneuron cell body antidromically. Thus, we applied both PNS and MPS such that the α-motoneuron cell body was activated 5 ms before the activation of the Ia sensory axon ending at the Ia-α motoneuron synapse. If the spinal reflexes can be modulated by STDP, and a combination of MPS and PNS is timed appropriately, then the H-Reflex amplitude will decrease while no change in H-Reflex amplitude is expected for MPS or PNS only. To test this hypothesis, six young healthy participants (5M/1F: 26.8 ± 4.1 yrs) received one of the three following conditions on days separated by at least 24 hr: 1) PAS, 2) MPS only or 3) PNS only. The H-Reflex and M-wave recruitment curves of the soleus were measured immediately prior to, immediately after, 30 min and 60 min after the intervention. The normalized H-Reflex amplitudes were then compared across conditions and times using a two-way ANOVA (3 conditions × 4 times). No main effects of condition or time, or interaction effect were found. These results suggest that relying solely on STDP may be insufficient to inhibit the soleus H-Reflex.

Examining the role of intrinsic and reflexive contributions to ankle joint hyper-resistance treated with botulinum toxin-A

BACKGROUND

Spasticity, i.e. stretch hyperreflexia, increases joint resistance similar to symptoms like hypertonia and contractures. Botulinum neurotoxin-A (BoNT-A) injections are a widely used intervention to reduce spasticity. BoNT-A effects on spasticity are poorly understood, because clinical measures, e.g. modified Ashworth scale (MAS), cannot differentiate between the symptoms affecting joint resistance. This paper distinguishes the contributions of the reflexive and intrinsic pathways to ankle joint hyper-resistance for participants treated with BoNT-A injections. We hypothesized that the overall joint resistance and reflexive contribution decrease 6 weeks after injection, while returning close to baseline after 12 weeks.

METHODS

Nine participants with spasticity after spinal cord injury or after stroke were evaluated across three sessions: 0, 6 and 12 weeks after BoNT-A injection in the calf muscles. Evaluation included clinical measures (MAS, Tardieu Scale) and motorized instrumented assessment using the instrumented spasticity test (SPAT) and parallel-cascade (PC) system identification. Assessments included measures for: (1) overall resistance from MAS and fast velocity SPAT; (2) reflexive resistance contribution from Tardieu Scale, difference between fast and slow velocity SPAT and PC reflexive gain; and (3) intrinsic resistance contribution from slow velocity SPAT and PC intrinsic stiffness/damping.

RESULTS

Individually, the hypothesized BoNT-A effect, the combination of a reduced resistance (week 6) and return towards baseline (week 12), was observed in the MAS (5 participants), fast velocity SPAT (2 participants), Tardieu Scale (2 participants), SPAT (1 participant) and reflexive gain (4 participants). On group-level, the hypothesis was only confirmed for the MAS, which showed a significant resistance reduction at week 6. All instrumented measures were strongly correlated when quantifying the same resistance contribution.

CONCLUSION

At group-level, the expected joint resistance reduction due to BoNT-A injections was only observed in the MAS (overall resistance). This observed reduction could not be attributed to an unambiguous group-level reduction of the reflexive resistance contribution, as no instrumented measure confirmed the hypothesis. Validity of the instrumented measures was supported through a strong association between different assessment methods. Therefore, further quantification of the individual contributions to joint resistance changes using instrumented measures across a large sample size are essential to understand the heterogeneous response to BoNT-A injections.

Neurophysiological validation of simultaneous intrinsic and reflexive joint impedance estimates

BACKGROUND

People with brain or neural injuries, such as cerebral palsy or spinal cord injury, commonly have joint hyper-resistance. Diagnosis and treatment of joint hyper-resistance is challenging due to a mix of tonic and phasic contributions. The parallel-cascade (PC) system identification technique offers a potential solution to disentangle the intrinsic (tonic) and reflexive (phasic) contributions to joint impedance, i.e. resistance. However, a simultaneous neurophysiological validation of both intrinsic and reflexive joint impedances is lacking. This simultaneous validation is important given the mix of tonic and phasic contributions to joint hyper-resistance. Therefore, the main goal of this paper is to perform a group-level neurophysiological validation of the PC system identification technique using electromyography (EMG) measurements.

METHODS

Ten healthy people participated in the study. Perturbations were applied to the ankle joint to elicit reflexes and allow for system identification. Participants completed 20 hold periods of 60 seconds, assumed to have constant joint impedance, with varying magnitudes of intrinsic and reflexive joint impedances across periods. Each hold period provided a paired data point between the PC-based estimates and neurophysiological measures, i.e. between intrinsic stiffness and background EMG, and between reflexive gain and reflex EMG.

RESULTS

The intrinsic paired data points, with all subjects combined, were strongly correlated, with a range of [Formula: see text] in both ankle plantarflexors and dorsiflexors. The reflexive paired data points were moderately correlated, with [Formula: see text] in the ankle plantarflexors only.

CONCLUSION

An agreement with the neurophysiological basis on which PC algorithms are built is necessary to support its clinical application in people with joint hyper-resistance. Our results show this agreement for the PC system identification technique on group-level. Consequently, these results show the validity of the use of the technique for the integrated assessment and training of people with joint hyper-resistance in clinical practice.

Therapeutic Interventions to Improve Mobility with Spinal Cord Injury Related Upper Motor Neuron Syndromes

Mobility is essential for quality of life and social participation. Some individuals with spinal cord injury have sufficient residual lower extremity motor control to walk. Improving walking function incorporates practice and training, and assistive devices or stimulation to augment function and balance. Overground robotic exoskeletons may have the potential to transform upright mobility in the future. Most individuals with spinal cord injury use a wheelchair for at least some of their mobility needs. Wheelchair skills training can open up new possibilities for participation. Regardless of the means of mobility, developing habits that protect joint health are essential for optimal lifelong mobility.

The Effects of Electrical Stimulation Parameters in Managing Spasticity After Spinal Cord Injury: A Systematic Review

Controversial findings about the effects of neuromuscular electrical stimulation and functional electrical stimulation in managing spasticity have been raised after spinal cord injury. A systematic review was conducted to identify the range of the stimulation parameters that may alleviate spasticity. Three independent reviewers searched Medline (PubMed), web of knowledge, Scopus, Cochrane Central, Virtual Health Library, and Physiotherapy Evidence Database until January 2018. Inclusion criteria were applications of neuromuscular electrical stimulation/functional electrical stimulation on the lower limb muscles, stimulation parameters (frequency, pulse duration, and amplitude of current), and measures of spasticity after spinal cord injury. The primary outcome was spasticity as measured by the Modified Ashworth Scale and the secondary outcome was spasticity assessed by other indirect measures. Twenty-three clinical and nonclinical trials were included with 389 subjects. Neuromuscular electrical stimulation/functional electrical stimulation provided reductions in spasticity by 45%-60% with decrease in electromyography activity and increase in range of motion after spinal cord injury. The identified stimulation parameters were frequency of 20-30 Hz, pulse duration of 300-350 μs, and amplitude of the current greater than 100 mA. Neuromuscular electrical stimulation/functional electrical stimulation provides an effective rehabilitation strategy in managing spasticity. However, a recommendation of the stimulation parameters cannot be accurately assumed because of high variability in the methodology, design, and heterogeneity of the included studies.

Comparison of transcutaneous electrical nerve stimulation (TENS) and functional electrical stimulation (FES) for spasticity in spinal cord injury - A pilot randomized cross-over trial

OBJECTIVE

Spasticity following spinal cord injury (SCI) can impair function and affect quality of life. This study compared the effects of transcutaneous electrical nerve stimulation (TENS) and functional electrical stimulation (FES) on lower limb spasticity in patients with SCI.

DESIGN

Double blind randomized crossover design.

SETTING

Neuro-rehabilitation unit, Manipal University, India.

PARTICIPANTS

Ten participants (age: 39 ± 13.6 years, C1-T11, 1-26 months post SCI) with lower limb spasticity were enrolled in this study.

INTERVENTIONS

Participants were administered electrical stimulation with TENS and FES (duration - 30 minutes) in a cross over manner separated by 24 hours.

OUTCOME MEASURES

Spasticity was measured using modified Ashworth scale (MAS) [for hip abductors, knee extensors and ankle plantar flexors] and spinal cord assessment tool for spastic reflexes (SCATS). Assessments were performed at baseline, immediately, 1 hour, 4 hours, and 24 hours post intervention.

RESULTS

A between group analysis did not show statistically significant differences between FES and TENS (P > 0.05). In the within group analyses, TENS and FES significantly reduced spasticity up to 4 hours in hip adductors and knee extensors (P < 0.01). SCATS values showed significant reductions at 1 hour (P = 0.01) following TENS and 4 hours following FES (P = 0.01).

CONCLUSION

A single session of electrical stimulation with FES and TENS appears to have similar anti-spasticity effects that last for 4 hours. The findings of this preliminary study suggest that both TENS and FES have the potential to be used as therapeutic adjuncts to relieve spasticity in the clinic. In addition, FES may have better effects on patients presenting with spastic reflexes.

Training-Specific Neural Plasticity in Spinal Reflexes after Incomplete Spinal Cord Injury

The neural plasticity of spinal reflexes after two contrasting forms of walking training was determined in individuals with chronic, motor-incomplete spinal cord injury (SCI). Endurance Training involved treadmill walking for as long as possible, and Precision Training involved walking precisely over obstacles and onto targets overground. Twenty participants started either Endurance or Precision Training for 2 months and then crossed over after a 2-month rest period to the other form of training for 2 months. Measures were taken before and after each phase of training and rest. The cutaneomuscular reflex (CMR) during walking was evoked in the soleus (SOL) and tibialis anterior muscles by stimulating the posterior tibial nerve at the ankle. Clonus was estimated from the EMG power in the SOL during unperturbed walking. The inhibitory component of the SOL CMR was enhanced after Endurance but not Precision Training. Clonus did not change after either form of training. Participants with lower reflex excitability tended to be better walkers (i.e., faster walking speeds) prior to training, and the reduction in clonus was significantly correlated with the improvement in walking speed and distance. Thus, reflex excitability responded in a training-specific way, with the reduction in reflex excitability related to improvements in walking function. Trial registration number is NCT01765153.

Functional Electrical Stimulation in Spinal Cord Injury: Clinical Evidence Versus Daily Practice

Functional electrical stimulation (FES) has clinical evidence in the rehabilitation of patients with spinal cord injury as indicated by several studies. Both inpatients and outpatients benefit from the therapeutic effect of the FES. The application areas are multifaceted and can be customized on the need for patients. This is represented by the individuality of the programmability of the stimulators and the variety of stimulation schedules that are based on the knowledge about the effects of FES on structural and functional level. Nevertheless, looking into daily clinical practice, the use of FES is rather poor. Expenditure of time, complexity of technical equipment, and compliance and acceptance of therapists and patients should be taken into account as limiting factors.

Functional Electrical Stimulation as a Safe and Effective Treatment for Equine Epaxial Muscle Spasms: Clinical Evaluations and Histochemical Morphometry of Mitochondria in Muscle Biopsies

Functional Electrical Stimulation (FES) has been used extensively over several decades to reverse muscle atrophy during rehabilitation for spinal cord injury patients. The benefits of the technology are being expanded into other areas, and FES has been recently utilized for injury rehabilitation and performance enhancement in horses. Six retired horses (age from 10 to 17 yrs) that had been previously used mainly for dressage riding were selected for this study. Clinical evaluation found epaxial muscle spasms in all horses with minimal to no pelvic extension when manually palpated. FES treatments were performed on the sacral/lumbar region 3 times per week for a period of 8 weeks, obtaining a total of 22 treatments per horse. The Modified Ashworth Scale for grading muscle spasms found a one grade improvement after approximately four FES treatments, indicating improved functional movement of the sacral/lumbar region, supporting the evidence by clinical palpations that a reduction in epaxial muscle spasms occurred. Skeletal muscle biopsies Pre and Post FES treatments were obtained from the longissimus lumborum muscle. Cryosections were stained with a Hemotoxylin-Eosin (H-E), and nicotinamide adenine dinucleotide tetrazolium reductase reaction (NADH-TR). The eventual size change of the muscle fibers were evaluated by morphometry in the H-E and NADH-TR stained cryosections, while in the NADH-TR slides the histochemical density and distribution of mitochondria were also determined. The main results of the morphometric analyses were: 1) As expected for the type of FES treatment used in this study, only a couple of horses showed significant increases in mean muscle fiber size when Pre- vs Post-FES biopsies were compared; 2) In the older horses, there were sparse (or many in one horse) very atrophic and angulated muscle fibers in both Pre- and Post-FES samples, whose attributes and distribution suggests that they were denervated due to a distal neuropathy; 3) The hypothesis of generalized FES-induced muscle fiber damage during epaxial muscle training is not supported by our data since: 3.1) Denervated muscle fibers were also present in the Pre-FES biopsies and 3.2) Only one horse presented with several long-term denervated muscles fibers Post-FES; 4) Preliminary data indicate an increased density and distribution of mitochondria in Post-FES biopsies, suggesting that the clinical improvements in the FES treated horses may be related to daily increased muscle contraction and perfusion induced by FES training. In conclusion, FES in horses is a safe treatment that provides clinical improvements in equine epaxial muscle spasms.

The effects of exercise with TENS on spasticity, balance, and gait in patients with chronic stroke: a randomized controlled trial

Background

Transcutaneous electrical nerve stimulation (TENS) is a useful modality for pain control. TENS has recently been applied to decrease spasticity. The purpose of this study is to determine whether the addition of TENS to an exercise program reduces spasticity and improves balance and gait in chronic stroke patients.

Material/Methods

This was a single-blinded, multicenter, randomized controlled trial. Thirty-four ambulatory individuals with chronic stroke participated and were randomly allocated to the TENS or Placebo group. The TENS group performed therapeutic exercise with TENS while the placebo (non-stimulation) TENS group performed therapeutic exercise with placebo TENS. Participants in both groups followed the same 30-min exercise regimen 5 times per week for a period of 6 weeks. Spasticity (modified Ashworth scale), static (balance system), and dynamic balance (timed up and go test), and gait ability (gait analyzer) were measured at 1 week before and 1 week after the intervention.

Results

Significant differences were observed between the 2 groups. Spasticity improved by 0.80 points in the TENS group. Anterior-posterior and medial-lateral sway velocity among static balance parameters and dynamic balance showed significant differences between the TENS and Placebo TENS groups (p=.000). Gait speed and cadence were enhanced significantly in the TENS group (p=.000). Step and stride length on the paretic side showed a significant difference in the TENS group (p=.000), while only velocity showed a significant difference in the Placebo TENS group (p=.004).

Conclusions

A combination of therapeutic exercise and TENS may reduce spasticity and improve balance, gait, and functional activity in chronic stroke patients.

Effects of robotic-locomotor training on stretch reflex function and muscular properties in individuals with spinal cord injury

OBJECTIVE

We sought to determine the therapeutic effect of robotic-assisted step training (RAST) on neuromuscular abnormalities associated with spasticity by characterization of their recovery patterns in people with spinal cord injury (SCI).

METHODS

Twenty-three motor-incomplete SCI subjects received one-hour RAST sessions three times per week for 4 weeks, while an SCI control group received no training. Neuromuscular properties were assessed using ankle perturbations prior to and during the training, and a system-identification technique quantified stretch reflex and intrinsic stiffness magnitude and modulation with joint position. Growth-mixture modeling classified subjects based on similar intrinsic and reflex recovery patterns.

RESULTS

All recovery classes in the RAST group presented significant (p<0.05) reductions in intrinsic and reflex stiffness magnitude and modulation with position; the control group presented no changes over time. Subjects with larger baseline abnormalities exhibited larger reductions, and over longer training periods.

CONCLUSIONS

Our findings demonstrate that RAST can effectively reduce neuromuscular abnormalities, with greater improvements for subjects with higher baseline abnormalities.

SIGNIFICANCE

Our findings suggest, in addition to its primary goal of improving locomotor patterns, RAST can also reduce neuromuscular abnormalities associated with spasticity. These findings also demonstrate that these techniques can be used to characterize neuromuscular recovery patterns in response to various types of interventions.

Recovery of neuronal and network excitability after spinal cord injury and implications for spasticity

The state of areflexia and muscle weakness that immediately follows a spinal cord injury (SCI) is gradually replaced by the recovery of neuronal and network excitability, leading to both improvements in residual motor function and the development of spasticity. In this review we summarize recent animal and human studies that describe how motoneurons and their activation by sensory pathways become hyperexcitable to compensate for the reduction of functional activation of the spinal cord and the eventual impact on the muscle. Specifically, decreases in the inhibitory control of sensory transmission and increases in intrinsic motoneuron excitability are described. We present the idea that replacing lost patterned activation of the spinal cord by activating synaptic inputs via assisted movements, pharmacology or electrical stimulation may help to recover lost spinal inhibition. This may lead to a reduction of uncontrolled activation of the spinal cord and thus, improve its controlled activation by synaptic inputs to ultimately normalize circuit function. Increasing the excitation of the spinal cord with spared descending and/or peripheral inputs by facilitating movement, instead of suppressing it pharmacologically, may provide the best avenue to improve residual motor function and manage spasticity after SCI.

Prediction of gait recovery in spinal cord injured individuals trained with robotic gait orthosis

Background

Motor impairment is a major consequence of spinal cord injury (SCI). Earlier studies have shown that robotic gait orthosis (e.g., Lokomat) can improve an SCI individual’s walking capacity. However, little is known about the differential responses among different individuals with SCI. The present longitudinal study sought to characterize the distinct recovery patterns of gait impairment for SCI subjects receiving Lokomat training, and to identify significant predictors for these patterns.

Methods

Forty SCI subjects with spastic hypertonia at their ankles were randomly allocated to either control or intervention groups. Subjects in the intervention group participated in twelve 1-hour Lokomat trainings over one month, while control subjects received no interventions. Walking capacity was evaluated in terms of walking speed, functional mobility, and endurance four times, i.e. baseline, 1, 2, and 4 weeks after training, using the 10-Meter-Walking, Timed-Up-and-Go, and 6-Minute-Walking tests. Growth Mixture Modeling, an analytical framework for stratifying subjects based on longitudinal changes, was used to classify subjects, based on their gait impairment recovery patterns, and to identify the effects of Lokomat training on these improvements.

Results

Two recovery classes (low and high walking capacity) were identified for each clinical evaluation from both the control and intervention groups. Subjects with initial high walking capacity (i.e. shorter Timed-Up-and-Go time, higher 10-Meter-Walking speed and longer 6-Minute-Walking distance) displayed significant improvements in speed and functional mobility (0.033 m/s/week and–0.41 s/week respectively); however no significant change in endurance was observed. Subjects with low walking capacity exhibited no significant improvement. The membership in these two classes—and thus prediction of the subject’s gait improvement trajectory over time—could be determined by the subject’s maximum voluntary torque at the ankle under both plantar-and dorsi-flexion contractions determined prior to any training.

Conclusion

Our findings demonstrate that subjects responded to Lokomat training non-uniformly, and should potentially be grouped based on their likely recovery patterns using objective criteria. Further, we found that the subject’s ankle torque can predict whether he/she would benefit most from Lokomat training prior to the therapy. These findings are clinically significant as they can help individualize therapeutic programs that maximize patient recovery while minimizing unnecessary efforts and costs.

Therapeutic intraspinal stimulation to generate activity and promote long-term recovery

Neuroprosthetic approaches have tremendous potential for the treatment of injuries to the brain and spinal cord by inducing appropriate neural activity in otherwise disordered circuits. Substantial work has demonstrated that stimulation applied to both the central and peripheral nervous system leads to immediate and in some cases sustained benefits after injury. Here we focus on cervical intraspinal microstimulation (ISMS) as a promising method of activating the spinal cord distal to an injury site, either to directly produce movements or more intriguingly to improve subsequent volitional control of the paretic extremities. Incomplete injuries to the spinal cord are the most commonly observed in human patients, and these injuries spare neural tissue bypassing the lesion that could be influenced by neural devices to promote recovery of function. In fact, recent results have demonstrated that therapeutic ISMS leads to modest but sustained improvements in forelimb function after an incomplete spinal cord injury (SCI). This therapeutic spinal stimulation may promote long-term recovery of function by providing the necessary electrical activity needed for neuron survival, axon growth, and synaptic stability.

Functional electrical stimulation for equine epaxial muscle spasms: retrospective study of 241 clinical cases

A retrospective study of 241 clinical cases, utilising over 1,800 functional electrical stimulation (FES) treatments to alleviate epaxial muscle spasms, showed that almost 80% (191) of the horses had a 1-grade improvement in muscle spasms after 2 FES treatments, based on the Modified Ashworth Scale adapted to horses. In addition, 60% (142) of these horses showed a sustained improvement for a minimum of 2 months.

Robotic-locomotor training as a tool to reduce neuromuscular abnormality in spinal cord injury: the application of system identification and advanced longitudinal modeling

In this study, the effect of the LOKOMAT, a robotic-assisted locomotor training system, on the reduction of neuromuscular abnormalities associated with spasticity was examined, for the first time in the spinal cord injury (SCI) population. Twenty-three individuals with chronic incomplete SCI received 1-hour training sessions in the LOKOMAT three times per week, with up to 45 minutes of training per session; matched control group received no intervention. The neuromuscular properties of the spastic ankle were then evaluated prior to training and after 1, 2, and 4 weeks of training. A parallel-cascade system identification technique was used to determine the reflex and intrinsic stiffness of the ankle joint as a function of ankle position at each time point. The slope of the stiffness vs. joint angle curve, i.e. the modulation of stiffness with joint position, was then calculated and tracked over the four-week period. Growth Mixture Modeling (GMM), an advanced statistical method, was then used to classify subjects into subgroups based on similar trends in recovery pattern of slope over time, and Random Coefficient Regression (RCR) was used to model the recovery patterns within each subgroup. All groups showed significant reductions in both reflex and intrinsic slope over time, but subjects in classes with higher baseline values of the slope showed larger improvements over the four weeks of training. These findings suggest that LOKOMAT training may also be useful for reducing the abnormal modulation of neuromuscular properties that arises as secondary effects after SCI. This can advise clinicians as to which patients can benefit the most from LOKOMAT training prior to beginning the training. Further, this study shows that system identification and GMM/RCR can serve as powerful tools to quantify and track spasticity over time in the SCI population.

The effect of using variable frequency trains during functional electrical stimulation cycling

Objectives.  This paper describes an experimental investigation of variable frequency stimulation patterns as a means of increasing torque production and, hence, performance in cycling induced by functional electrical stimulation. Materials and Methods.  Experiments were conducted on six able-bodied subjects stimulating both quadriceps during isokinetic trials. Constant-frequency trains (CFT) with 50-msec interpulse intervals and four catchlike-inducing trains (CIT) were tested. The CITs had an initial, brief, high-frequency burst of two pulses at the onset of or within a subtetanic low-frequency stimulation train. Each stimulation train consisted of the same number of pulses. The active torques produced by each train were compared. Parametric main effect ANOVA tests were performed on the active torque-time integral (TTI), on the active torque peaks and on the time needed to reach those peaks (T2P). Results.  The electrical stimulation of the quadriceps produced active torques with mean peak values in the range of 1.6-3.5 Nm and a standard error below 0.2 Nm. CITs produced a significant increase of TTI and torque peaks compared with CFTs in all the experimental conditions. In particular, during the postfatigue trials, the CITs with the doublet placed in the middle of the train produced TTIs and torque peaks about 61% and 28% larger than the CFT pattern, respectively. In addition, the CITs showed the lowest reduction of the performance between prefatigue and postfatigue conditions. Conclusions.  The use of CITs improves the functional electrical stimulation cycling performance compared with CFT stimulation. This application might have a relevant clinical importance for individuals with stroke where the residual sensation is still present and thus the maximization of the performance without an excessive increase of the stimulation intensity is advisable. Therefore, exercise intensity can be increased yielding a better muscle strength and endurance that may be beneficially for later gait training in individuals with stroke.

Stance controlled knee flexion improves stimulation driven walking after spinal cord injury

Background

Functional neuromuscular stimulation (FNS) restores walking function after paralysis from spinal cord injury via electrical activation of muscles in a coordinated fashion. Combining FNS with a controllable orthosis to create a hybrid neuroprosthesis (HNP) has the potential to extend walking distance and time by mechanically locking the knee joint during stance to allow knee extensor muscle to rest with stimulation turned off. Recent efforts have focused on creating advanced HNPs which couple joint motion (e.g., hip and knee or knee and ankle) to improve joint coordination during swing phase while maintaining a stiff-leg during stance phase.

Methods

The goal of this study was to investigate the effects of incorporating stance controlled knee flexion during loading response and pre-swing phases on restored gait. Knee control in the HNP was achieved by a specially designed variable impedance knee mechanism (VIKM). One subject with a T7 level spinal cord injury was enrolled and served as his own control in examining two techniques to restore level over-ground walking: FNS-only (which retained a stiff knee during stance) and VIKM-HNP (which allowed controlled knee motion during stance). The stimulation pattern driving the walking motion remained the same for both techniques; the only difference was that knee extensor stimulation was constant during stance with FNS-only and modulated together with the VIKM to control knee motion during stance with VIKM-HNP.

Results

Stance phase knee angle was more natural during VIKM-HNP gait while knee hyperextension persisted during stiff-legged FNS-only walking. During loading response phase, vertical ground reaction force was less impulsive and instantaneous gait speed was increased with VIKM-HNP, suggesting that knee flexion assisted in weight transfer to the leading limb. Enhanced knee flexion during pre-swing phase also aided flexion during swing, especially when response to stimulation was compromised.

Conclusions

These results show the potential advantages of incorporating stance controlled knee flexion into a hybrid neuroprosthesis for walking. The addition of such control to FNS driven walking could also enable non-level walking tasks such as uneven terrain, slope navigation and stair descent where controlled knee flexion during weight bearing is critical.

Therapeutic intraspinal microstimulation improves forelimb function after cervical contusion injury

OBJECTIVE

Intraspinal microstimulation (ISMS) is a promising method for activating the spinal cord distal to an injury. The objectives of this study were to examine the ability of chronically implanted stimulating wires within the cervical spinal cord to (1) directly produce forelimb movements, and (2) assess whether ISMS stimulation could improve subsequent volitional control of paretic extremities following injury.

APPROACH

We developed a technique for implanting intraspinal stimulating electrodes within the cervical spinal cord segments C6-T1 of Long-Evans rats. Beginning 4 weeks after a severe cervical contusion injury at C4-C5, animals in the treatment condition received therapeutic ISMS 7 hours/day, 5 days/week for the following 12 weeks.

MAIN RESULTS

Over 12 weeks of therapeutic ISMS, stimulus-evoked forelimb movements were relatively stable. We also explored whether therapeutic ISMS promoted recovery of forelimb reaching movements. Animals receiving daily therapeutic ISMS performed significantly better than unstimulated animals during behavioural tests conducted without stimulation. Quantitative video analysis of forelimb movements showed that stimulated animals performed better in the movements reinforced by stimulation, including extending the elbow to advance the forelimb and opening the digits. While threshold current to elicit forelimb movement gradually increased over time, no differences were observed between chronically stimulated and unstimulated electrodes suggesting that no additional tissue damage was produced by the electrical stimulation.

SIGNIFICANCE

The results indicate that therapeutic intraspinal stimulation delivered via chronic microwire implants within the cervical spinal cord confers benefits extending beyond the period of stimulation, suggesting future strategies for neural devices to promote sustained recovery after injury.

Repetitive common peroneal nerve stimulation increases ankle dorsiflexor motor evoked potentials in incomplete spinal cord lesions

Plasticity of corticospinal tract (CST) activity likely plays a key role in motor function recovery after central nervous system (CNS) lesions. In non-injured adults, 30 min of repetitive common peroneal nerve stimulation (rCPnS) increases CST excitability by 40-50% and the effect persists for at least 30 min. The present study evaluated with transcranial magnetic stimulation (TMS) the changes in CST excitability after 30 min of rCPnS in people with foot drop due to incomplete SCI. Suprathreshold rCPnS (25 Hz, alternating 1 s on 1 s off stimulation cycle) was given for two 15-min periods, while the subject sat at rest with ankle and knee joints fixed. Before, between, and after the periods of stimulation, the tibialis anterior (TA) motor evoked potentials (MEPs) to TMS were measured at a TMS intensity that originally produced a half-maximum MEP (typically 10-20% above threshold) while the sitting subject provided 25-30% maximum voluntary TA contraction. In 10 subjects with SCI, the peak-to-peak TA MEP increased by 14 ± 3% after rCPnS and the peak increase (+21 ± 7%) occurred 15 min after the cessation of rCPnS. The TA H-reflex, measured in separate experiments in 7 subjects, did not increase after rCPnS. The results indicate that rCPnS can increase CST excitability for the TA in people with incomplete SCI, although its effects appear smaller and shorter lasting than those found in non-injured control subjects. Such short-term plasticity in the CST excitability induced by rCPnS may contribute to long-term therapeutic effects of functional electrical stimulation previously reported in people with CNS lesions.

Mimicking muscle activity with electrical stimulation

Functional electrical stimulation is a rehabilitation technology that can restore some degree of motor function in individuals who have sustained a spinal cord injury or stroke. One way to identify the spatio-temporal patterns of muscle stimulation needed to elicit complex upper limb movements is to use electromyographic (EMG) activity recorded from able-bodied subjects as a template for electrical stimulation. However, this requires a transfer function to convert the recorded (or predicted) EMG signals into an appropriate pattern of electrical stimulation. Here we develop a generalized transfer function that maps EMG activity into a stimulation pattern that modulates muscle output by varying both the pulse frequency and the pulse amplitude. We show that the stimulation patterns produced by this transfer function mimic the active state measured by EMG insofar as they reproduce with good fidelity the complex patterns of joint torque and joint displacement.

Quantification of the effects of an alpha-2 adrenergic agonist on reflex properties in spinal cord injury using a system identification technique

Background

Despite numerous investigations, the impact of tizanidine, an anti-spastic medication, on changes in reflex and muscle mechanical properties in spasticity remains unclear. This study was designed to help us understand the mechanisms of action of tizanidine on spasticity in spinal cord injured subjects with incomplete injury, by quantifying the effects of a single dose of tizanidine on ankle muscle intrinsic and reflex components.

Methods

A series of perturbations was applied to the spastic ankle joint of twenty-one spinal cord injured subjects, and the resulting torques were recorded. A parallel-cascade system identification method was used to separate intrinsic and reflex torques, and to identify the contribution of these components to dynamic ankle stiffness at different ankle positions, while subjects remained relaxed.

Results

Following administration of a single oral dose of Tizanidine, stretch evoked joint torque at the ankle decreased significantly (p < 0.001) The peak-torque was reduced between 15% and 60% among the spinal cord injured subjects, and the average reduction was 25%. Using systems identification techniques, we found that this reduced torque could be attributed largely to a reduced reflex response, without measurable change in the muscle contribution. Reflex stiffness decreased significantly across a range of joint angles (p < 0.001) after using tizanidine. In contrast, there were no significant changes in intrinsic muscle stiffness after the administration of tizanidine.

Conclusions

Our findings demonstrate that tizanidine acts to reduce reflex mechanical responses substantially, without inducing comparable changes in intrinsic muscle properties in individuals with spinal cord injury. Thus, the pre-post difference in joint mechanical properties can be attributed to reflex changes alone. From a practical standpoint, use of a single "test" dose of Tizanidine may help clinicians decide whether the drug can helpful in controlling symptoms in particular subjects.

Predication of reflex recovery after stroke using quantitative assessments of motor impairment at 1 month

The objective of this study was to characterize the time-course of changes reflex stiffness after stroke, and to use the Fugl-Meyer Assessment (FMA) at 1 month to predict the ensuing recovery patterns over 1 year. We quantified the modulation of reflex stiffness as a function of elbow joint angles at 1, 2, 3, 6, and 12 months after stroke, using a parallel cascade system identification technique. We then used the "growth mixture" and logistic regression models to characterize recovery patterns over 1 year and to predict these patterns, based on the FMA score at 1 month. We observed two major distinct recovery classes for the relationship between reflex stiffness and elbow angle. The FMA at 1 month was a significant predictor of reflex stiffness as a function of elbow angle at different time points in the first year. The logistical regression class membership may enable us to accurately predict reflex behavior during the first year, information of great potential value for planning targeted therapeutic interventions. Finally, the findings suggest that abnormal reflex function could contribute to functional motor impairment.

Spinal reflexes in ankle flexor and extensor muscles after chronic central nervous system lesions and functional electrical stimulation

OBJECTIVE

Spinal reciprocal inhibitory and excitatory reflexes of ankle extensor and flexor muscles were investigated in ambulatory participants with chronic central nervous system (CNS) lesions causing foot drop as a function of time after lesion and stimulator use.

METHODS

Thirty-nine participants with progressive (eg, secondary progressive MS) and 36 with generally nonprogressive (eg, stroke) conditions were studied. The tibialis anterior (TA) and soleus maximum H-reflex/M-wave (Hmax/Mmax) ratios and maximum voluntary contractions (MVC) were measured and compared with those in age-matched control participants. Reciprocal inhibition was measured as a depression of the ongoing electromyographic (EMG) activity produced by antagonist muscle-nerve stimulation.

RESULTS

Participants with CNS lesions had significantly higher soleus Hmax/Mmax ratios than control participants, and reduced voluntary modulation of the reflexes occurred in both muscles. Reciprocal inhibition of soleus from common peroneal (CP) nerve stimulation was not significantly different from controls in either group. Inhibition of the TA by tibial nerve stimulation decreased and was eventually replaced by excitation in participants with nonprogressive disorders. No significant change occurred in progressive disorders. Use of a foot drop stimulator increased the TA, but not the soleus MVC overall. H-reflexes only showed small changes. Reciprocal inhibition of the TA increased considerably, while that of the soleus muscle decreased toward control values.

CONCLUSIONS

Disorders that produce foot drop also produce reflex changes, some of which only develop over a period of years or even decades. Regular use of a foot drop stimulator strengthens voluntary pathways and changes some reflexes toward control values. Thus, stimulators may provide multiple benefits to people with foot drop.

The relation between Ashworth scores and neuromechanical measurements of spasticity following stroke

Background

Spasticity is a common impairment that follows stroke, and it results typically in functional loss. For this reason, accurate quantification of spasticity has both diagnostic and therapeutic significance. The most widely used clinical assessment of spasticity is the modified Ashworth scale (MAS), an ordinal scale, but its validity, reliability and sensitivity have often been challenged. The present study addresses this deficit by examining whether quantitative measures of neural and muscular components of spasticity are valid, and whether they are strongly correlated with the MAS.

Methods

We applied abrupt small amplitude joint stretches and Pseudorandom Binary Sequence (PRBS) perturbations to both paretic and non-paretic elbow and ankle joints of stroke survivors. Using advanced system identification techniques, we quantified the dynamic stiffness of these joints, and separated its muscular (intrinsic) and reflex components. The correlations between these quantitative measures and the MAS were investigated.

Results

We showed that our system identification technique is valid in characterizing the intrinsic and reflex stiffness and predicting the overall net torque. Conversely, our results reveal that there is no significant correlation between muscular and reflex torque/stiffness and the MAS magnitude. We also demonstrate that the slope and intercept of reflex and intrinsic stiffnesses plotted against the joint angle are not correlated with the MAS.

Conclusion

Lack of significant correlation between our quantitative measures of stroke effects on spastic joints and the clinical assessment of muscle tone, as reflected in the MAS suggests that the MAS does not provide reliable information about the origins of the torque change associated with spasticity, or about its contributing components.

Modulation in spinal circuits and corticospinal connections following nerve stimulation and operant conditioning

Neural plasticity occurs throughout adult life. In healthy individuals, different spinal pathways are differently modulated during different daily activities. Drastic changes to nervous system activity and connections caused by injuries or diseases alter spinal reflexes, and this is often related to disturbed motor functions. In both health and disease, spinal reflexes are subject to substantial modifications. Plasticity in supraspinal descending connections is even more remarkable; corticospinal connectivity has been shown to be extremely plastic. In this session, we describe two approaches for possibly improving recovery after central nervous system (CNS) lesions. They are very different, but both involve repetitive nerve stimulation and CNS plasticity. The first approach is functional electrical stimulation (FES) of the common peroneal nerve, which has been used to treat foot drop in patients with CNS lesions. The second approach is operant conditioning of a spinal reflex. Spinal reflex operant conditioning studies in animal models have shown plastic changes in spinal cord neurons associated with this form of learning and improved locomotor function in incomplete spinal cord injured rats. Thus, reflex conditioning might be a robust approach to inducing plasticity at spinal and supraspinal levels. As a first step in establishing this approach and characterizing its effects in the human adult CNS, we are currently investigating the extent and time course of operant conditioning of the soleus H-reflex in healthy subjects. In results to date, all subjects (n=5) have changed reflex size in the correct direction to various degree (16-36%) over 2-3 months of conditioning, indicating possibility that H-reflex conditioning can occur in humans. At the same time, the substantial inter-subject variation in the time course and extent of conditioning suggest that additional data are needed to establish its principal features. We hope that studying modulation and modification o- f the CNS by different approaches will help us further understand the plasticity of the human adult nervous system.

Mechanical abnormalities of the spastic ankle in chronic stroke subjects

We examined the intrinsic and reflex contributions to ankle stiffness in people with chronic stroke and healthy subjects using the parallel system identification technique. Modulation of intrinsic and reflex stiffness was characterized by applying pseudorandom binary sequence (PRBS) perturbations to the ankle at different initial ankle joint over the entire range of motion (ROM). The experiments were performed for both paretic (stroke) and contralateral (control) side. Healthy (normal) subjects were used a secondary control. Reflex stiffness gain significantly increased in stroke than in control side at most positions. Intrinsic stiffness gain also increased significantly at dorsiflexing positions. These changes were position dependent. Thus, the abnormalities in intrinsic stiffness gain increased continuously from middle plantarflexion to full dorsiflexion while the major increase in reflex stiffness happened at the middle ROM. No significant changes were found in other intrinsic and reflex stiffness parameters. As compared to the normal ankle, the reflex stiffness gain of the control side was significantly larger, indicating that the control side is not normal. These findings demonstrate that both intrinsic and reflex stiffness contribute significantly to the mechanical abnormality associated with spastic ankle in hemiplegic stroke subjects. The results also suggest that the contralateral limb may not be used as a suitable control.

Muscle and reflex changes with varying joint angle in hemiparetic stroke

Background

Despite intensive investigation, the origins of the neuromuscular abnormalities associated with spasticity are not well understood. In particular, the mechanical properties induced by stretch reflex activity have been especially difficult to study because of a lack of accurate tools separating reflex torque from torque generated by musculo-tendinous structures. The present study addresses this deficit by characterizing the contribution of neural and muscular components to the abnormally high stiffness of the spastic joint.

Methods

Using system identification techniques, we characterized the neuromuscular abnormalities associated with spasticity of ankle muscles in chronic hemiparetic stroke survivors. In particular, we systematically tracked changes in muscle mechanical properties and in stretch reflex activity during changes in ankle joint angle. Modulation of mechanical properties was assessed by applying perturbations at different initial angles, over the entire range of motion (ROM). Experiments were performed on both paretic and non-paretic sides of stroke survivors, and in healthy controls.

Results

Both reflex and intrinsic muscle stiffnesses were significantly greater in the spastic/paretic ankle than on the non-paretic side, and these changes were strongly position dependent. The major reflex contributions were observed over the central portion of the angular range, while the intrinsic contributions were most pronounced with the ankle in the dorsiflexed position.

Conclusion

In spastic ankle muscles, the abnormalities in intrinsic and reflex components of joint torque varied systematically with changing position over the full angular range of motion, indicating that clinical perceptions of increased tone may have quite different origins depending upon the angle where the tests are initiated.

Furthermore, reflex stiffness was considerably larger in the non-paretic limb of stroke patients than in healthy control subjects, suggesting that the non-paretic limb may not be a suitable control for studying neuromuscular properties of the ankle joint.

Our findings will help elucidate the origins of the neuromuscular abnormalities associated with stroke-induced spasticity.

Clinical factors that affect walking level and performance in chronic spinal cord lesion patients

STUDY DESIGN

Observational Study.

OBJECTIVE

To evaluate the effects of neurologic and non-neurologic factors on walking level and performance in chronic spinal cord lesion (SCL) patients.

SUMMARY OF BACKGROUND DATA

Walking is one of the primary goals of patients after a SCL. Several studies have demonstrated that different neurologic and non-neurologic factors can affect walking level and performance. However, in SCL age and muscle strength have always been considered the major determinants of walking.

METHODS

Sixty-five patients with chronic SCL were included. Their demographic, neurologic status (ASIA standards), balance, and spasticity were recorded. Pearson and Spearman correlations were adopted to quantify the association between patients' characteristics and walking ability. The relationship between functional walking measures, Timed Up and Go, Six Minutes Walking Test (SMWT), Ten Meters Walking Test, and Walking Index for Spinal Cord Injury, and demographic and neurologic factors were measured by regression analyses.

RESULTS

Strength, balance, spasticity, and age were strictly correlated with walking level and walking performance. They also were the best predictors of walking features.

CONCLUSION

Results confirm the recognized importance of age and upper and lower extremity strengths for walking after a SCL. They also highlight the role of 2 other factors, i.e., balance and spasticity, seldom considered as thoroughly in SCL.

Prediction of upper limb muscle activity from motor cortical discharge during reaching

Movement representation by the motor cortex (M1) has been a theoretical interest for many years, but in the past several years it has become a more practical question, with the advent of the brain-machine interface. An increasing number of groups have demonstrated the ability to predict a variety of kinematic signals on the basis of M1 recordings and to use these predictions to control the movement of a cursor or robotic limb. We, on the other hand, have undertaken the prediction of myoelectric (EMG) signals recorded from various muscles of the arm and hand during button pressing and prehension movements. We have shown that these signals can be predicted with accuracy that is similar to that of kinematic signals, despite their stochastic nature and greater bandwidth. The predictions were made using a subset of 12 or 16 neural signals selected in the order of each signal's unique, output-related information content. The accuracy of the resultant predictions remained stable through a typical experimental session. Accuracy remained above 80% of its initial level for most muscles even across periods as long as two weeks. We are exploring the use of these predictions as control signals for neuromuscular electrical stimulation in quadriplegic patients.

Comparison of neuromuscular abnormalities between upper and lower extremities in hemiparetic stroke

We studied the neuromuscular mechanical properties of the elbow and ankle joints in chronic, hemiparetic stroke patients and healthy subjects. System identification techniques were used to characterize the mechanical abnormalities of these joints and to identify the contribution of intrinsic and reflex stiffness to these abnormalities. Modulation of intrinsic and reflex stiffness with the joint angle was studied by applying PRBS perturbations to the joint at different joint angles. The experiments were performed for both spastic (stroke) and contralateral (control) sides of stroke patients and one side of healthy (normal) subjects. We found reflex stiffness gain (GR) was significantly larger in the stroke than the control side for both elbow and ankle joints. GR was also strongly position dependent in both joints. However, the modulation of GR with position was slightly different in two joints. GR was also larger in the control than the normal joints but the differences were significant only for the ankle joint. Intrinsic stiffness gain (K) was also significantly larger in the stroke than the control joint at elbow extended positions and at ankle dorsiflexed positions. Modulation of K with the ankle angle was similar for stroke, control and normal groups. In contrast, the position dependency of the elbow was different. K was larger in the control than normal ankle whereas it was lower in the control than normal elbow. However, the differences were not significant for any joint. The findings demonstrate that both reflex and intrinsic stiffness gain increase abnormally in both upper and lower extremities. However, the major contribution of intrinsic and reflex stiffness to the abnormalities is at the end of ROM and at the middle ROM, respectively. The results also demonstrate that the neuromuscular properties of the contralateral limb are not normal suggesting that it may not be used as a suitable control at least for the ankle study.

Benefits of FES gait in a spinal cord injured population

STUDY DESIGN

Review.

OBJECTIVES

This review article investigated the objective evidence of benefits derived from functional electrical stimulation (FES)-assisted gait for people with spinal cord injury (SCI). Both FES and gait have been proposed to promote not only augmented health and fitness, but specific ambulatory outcomes for individuals with neurological disabilities. However, due to small sample sizes and the lack of functionality of the intervention, it has not been widely used in clinical practice. This review assessed whether there is sufficient evidence to encourage a more widespread deployment of FES gait within the rehabilitation community.

METHODS

Hand searches and online data collection were performed in Medline and Science Direct. Specific search terms used included SCI/paralysis/paraplegia and tetraplegia with electrical stimulation/FES, gait and walking.

RESULTS

The searches generated 532 papers. Of these papers, 496 were excluded and 36 papers were included in the review. Many reported benefits were not carefully investigated, and small sample sizes or different methodologies resulted in insufficient evidence to draw definitive conclusions.

CONCLUSIONS

FES gait can enhance gait, muscle strength and cardiorespiratory fitness for people with SCI. However, these benefits are dependent on the nature of the injury and further research is required to generalize these results to the widespread population of SCI individuals. Proof of the functionality and further evidence of the benefits of FES gait will assist in FES gait gaining clinical acceptance.

Neuromuscular abnormalities associated with spasticity of upper extremity muscles in hemiparetic stroke

Our objective was to assess the mechanical changes associated with spasticity in elbow muscles of chronic hemiparetic stroke survivors and to compare these changes with those recorded in the ankle muscles of a similar cohort. We first characterized elbow dynamic stiffness by applying pseudorandom binary positional perturbations to the joints at different initial angles, over the entire range of motion, with subjects relaxed. We separated this stiffness into intrinsic and reflex components using a novel parallel cascade system identification technique. In addition, for controls, we studied the nonparetic limbs of stroke survivors and limbs of age-matched healthy subjects as primary and secondary controls. We found that both reflex and intrinsic stiffnesses were significantly larger in the stroke than in the nonparetic elbow muscles, and the differences increased as the elbow was extended. Reflex stiffness increased monotonically with the elbow angle in both paretic and nonparetic sides. In contrast, the modulation of intrinsic stiffness with elbow position was different in nonparetic limbs; intrinsic stiffness decreased sharply from full- to mid-flexion in both sides, then it increased continuously with the elbow extension in the paretic side. It remained invariant in the nonparetic side. Surprisingly, reflex stiffness was larger in the nonparetic than in the normal control arm, yet intrinsic stiffness was smaller in the nonparetic arm. Finally, we compare the angular dependence of paretic elbow and ankle muscles and show that the modulation of reflex stiffness with position was strikingly different.

Electromyographic signal-activated functional electrical stimulation of abdominal muscles: the effect on pulmonary function in patients with tetraplegia

BACKGROUND

Paralysis of abdominal muscles is the main cause of respiratory dysfunctions in patients with lower cervical spinal cord lesion. Activation of the abdominal muscles using functional electrical stimulation (FES) improved respiratory function in these patients. But application of FES frequently requires a caregiver, and it may not be well synchronized with the patient's respiratory activity.

OBJECTIVE

To perform preliminary examination of electromyographic (EMG)-activated FES for caregiver-independent and synchronized cough and expiration induction in tetraplegia.

DESIGN

Self-controlled study.

SETTING

Loewenstein Rehabilitation Center, Raanana, Israel.

SUBJECTS

A total of 10 male patients with complete or almost complete tetraplegia.

MAIN OUTCOME MEASURES

Peak expiratory flow (PEF), forced vital capacity (FVC), and maximal voluntary ventilation (MVV).

METHODS

The outcome measures were examined with the abdominal muscles unassisted or assisted by various methods. These included manual assistance or application of FES, activated by a caregiver, by the patient, or by EMG signals elicited from the patient's muscle.

RESULTS

Manual assistance improved the mean PEF value by 36.7% (P<0.01) and the mean FVC value by 15.4% (P=0.01). FES did not significantly change most measurements, and patient-activated FES even reduced PEF (P<0.05). But following EMG-activated FES PEF and FVC values were higher than those following patient-activated FES (P<0.05 for PEF; P<0.01 for FVC), and their mean values were higher by 15.8 and 18.9%, respectively.

CONCLUSIONS

Abdominal FES failed to improve respiratory function in this study, but applying FES to abdominal muscles by EMG from the patient's muscle may promote caregiver-free respiration and coughing in persons with cervical SCL.

Modeling and Control Considerations for Powered Lower-Limb Orthoses: A Design Study for Assisted STS

Lower-limb orthotic devices may be used to aid or restore mobility to the impaired user. Powered orthoses, in particular, hold great potential in improving the quality of life for individuals with locomotor difficulties because active control of an orthosis can aid limb movement in common tasks that may even be impossible if unaided. However, these devices have primarily remained the products of research labs with the number of effective commercial applications for the laity being nearly nonexistent. This paper provides an overview of the current status of powered orthoses and goes on to discuss key issues in modeling and control of powered orthoses so that designers can have a unified framework in developing user-oriented devices. Key concepts are demonstrated for a powered knee-orthosis intended for assisting the sit-to-stand task, and both pneumatic muscle and dc motor actuators are considered in this conceptual design study. In the final analysis, we conclude that the ability to provide sit-to-stand assistance is profoundly dependent on the type of control signal employed to control the actuator from the user–orthosis interface.

Training-induced adaptive plasticity in human somatosensory reflex pathways

This paper reviews evidence supporting adaptive plasticity in muscle and cutaneous afferent reflex pathways induced by training and rehabilitative interventions. The perspective is advanced that the behavioral and functional relevance of any intervention and the reflex pathway under study should be considered when evaluating both adaptation and transfer. A cornerstone of this concept can be found in acute task-dependent reflex modulation. Because the nervous system allows the expression of a given reflex according to the motor task, an attempt to evaluate the training adaptation should also be evoked under the same conditions as training bearing in mind the functional role of the pathway under study. Within this framework, considerable evidence supports extensive adaptive plasticity in human muscle afferent pathways in the form of operant conditioning, strength training, skill training, and locomotor training or retraining. Directly comparable evidence for chronic adaptation in cutaneous reflex pathways is lacking. However, activity-dependent plasticity in cutaneous pathways is documented particularly in approaches to neurological rehabilitation. Overall, the adaptive range for human muscle afferent reflexes appears bidirectional (that is, increased or reduced amplitudes) and on the order of 25-50%. The adaptive range for cutaneous pathways is currently uncertain.

Physical Determinants, Emerging Concepts, and Training Approaches in Gait of Individuals with Spinal Cord Injury

The aim of this review is to examine the physical determinants for functional walking as well as the efficacy of gait rehabilitation after spinal cord injury (SCI) in humans. The results indicate several important physical determinants in gait. Examples are provided of different interventions that produce beneficial effects on outcome measures of gait such as gait speed, stride length, walking endurance, motor recovery, and gait quality. These findings need to be considered in current SCI rehabilitation practices, but the efficacy of certain interventions remains unclear. Well-designed clinical trials are needed to provide evidence of the role of physical determinants in the development of new concepts and principles in locomotor recovery after SCI. This review focuses on relevant literature, and informs rehabilitation specialists and basic scientists about the physical determinants and factors to consider for optimization of gait training in individuals with incomplete SCI.

Spasticity after spinal cord injury

Symptoms of spasticity are often experienced by individuals with spinal cord injury (SCI) following a period of spinal shock and, in many cases, these symptoms negatively affect quality of life. Despite its prevalence, spasticity as a syndrome in the SCI population is not always managed effectively. This is likely due to the fact that the syndrome can have various presentations, each with their own specific etiology. This overview summarizes the symptoms and pathophysiology of the various presentations of spasticity in the SCI population and discusses the currently accepted management techniques. There is a need for a better understanding of the syndrome of spasticity as well as the development of a valid and reliable assessment tool.

Comparison of Electric Stimulation Methods for Reduction of Triceps Surae Spasticity in Spinal Cord Injury

OBJECTIVES

To compare the effect of 3 methods of electric stimulation to reduce spasticity of the triceps surae in patients with complete spinal cord injury (SCI) and to investigate the carryover effect.

DESIGN

Placebo-controlled study with repeated measurements after the interventions.

SETTING

Research department affiliated with a rehabilitation hospital in the Netherlands.

PARTICIPANTS

Ten patients with a complete SCI were recruited from the outpatient population of the rehabilitation hospital. All subjects had American Spinal Injury Association grade A impairment scores, except for one, who had grade C. The patients had no voluntary triceps surae contractibility.

INTERVENTIONS

Forty-five minutes of cyclic electric stimulation of the agonist, antagonist, or dermatome of the triceps surae or a placebo approach.

MAIN OUTCOME MEASURES

Outcome measures were the Modified Ashworth Scale (MAS), clonus score, and the H-reflex and M wave (H/M) ratio. The electromyographic response to a stretch of the soleus over the whole range of motion was also determined. The magnitude and ankle angle at which the electromyographic response started were calculated.

RESULTS

Stimulation of the agonist provided a significant reduction in the MAS compared with the placebo approach (P<.001). There was no significant change in the H/M ratio or the electromyographic response amplitude after any of the stimulation methods, whereas stimulation of the antagonist muscle resulted in a significant reduction in the ankle angle at which the electromyographic response started, compared with the placebo approach (P<.037).

CONCLUSIONS

Triceps surae stimulation reduces the MAS for that specific muscle, whereas the angle at which the reflex starts changes after antagonist stimulation.

Short-term effects of functional electrical stimulation on spinal excitatory and inhibitory reflexes in ankle extensor and flexor muscles

The purpose of this study was to investigate short-term effects of walking with functional electrical stimulation (FES) on inhibitory and excitatory spinal reflexes in healthy subjects. The FES was applied to the common peroneal (CP) nerve during the swing phase of the step cycle when the ankle flexors are active. We have previously shown that corticospinal excitability for the tibialis anterior (TA) muscle increased after 30 min of FES-assisted walking. An increase of corticospinal excitability could be due to the changes in spinal and/or cortical excitability. Thus, we wished to examine whether a short-term application of FES would increase spinal motoneuronal excitability. Changes could also result from effects on inhibitory as well as excitatory pathways, but to our knowledge no studies have investigated short-term effects of FES on spinal inhibitory pathways. Therefore, we measured reciprocal and presynaptic inhibition, as well as reflex excitability, before and after FES-assisted walking. As controls, effects of FES-like stimulation at rest and walking without stimulation were tested in separate sessions. The TA H-reflex amplitude did not increase after FES in any of the conditions tested, so we have no evidence that FES increases spinal excitability for the TA. The soleus H-reflex decreased slightly (10%) after FES-assisted walking, and remained decreased for at least 30 min. However, the control experiment indicated that this decrease was associated with walking and not with stimulation. Thirty minutes of FES did not produce any significant effects on spinal inhibitory pathways examined in the present study. In conclusion, the soleus H-reflex showed a small but consistent decrease and no spinal circuits examined showed an increase, as was observed in the corticospinal excitability. Thus, we suggest that a short-term application of FES increases the excitability of the cortex or its connections to the spinal cord more effectively than that of spinal pathways.

Targeting recovery: priorities of the spinal cord-injured population

In the United States alone, there are more than 200,000 individuals living with a chronic spinal cord injury (SCI). Healthcare for these individuals creates a significant economic burden for the country, not to mention the physiological, psychological, and social suffering these people endure everyday. Regaining partial function can lead to greater independence, thereby improving quality of life. To ascertain what functions are most important to the SCI population, in regard to enhancing quality of life, a novel survey was performed in which subjects were asked to rank seven functions in order of importance to their quality of life. The survey was distributed via email, postal mail, the internet, interview, and word of mouth to the SCI community at large. A total of 681 responses were completed. Regaining arm and hand function was most important to quadriplegics, while regaining sexual function was the highest priority for paraplegics. Improving bladder and bowel function was of shared importance to both injury groups. A longitudinal analysis revealed only slight differences between individuals injured <3 years compared to those injured >3 years. The majority of participants indicated that exercise was important to functional recovery, yet more than half either did not have access to exercise or did not have access to a trained therapist to oversee that exercise. In order to improve the relevance of research in this area, the concerns of the SCI population must be better known and taken into account. This approach is consistent with and emphasized by the new NIH roadmap to discovery.

Functional electrical stimulation using microstimulators to correct foot drop: a case study

This paper presents a case study that tested the feasibility and efficacy of using injectable microstimulators (BIONs®) in a functional electrical stimulation (FES) device to correct foot drop. Compared with surface stimulation of the common peroneal nerve, stimulation with BIONs provides more selective activation of specific muscles. For example, stimulation of the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles with BIONs produces ankle flexion without excessive inversion or eversion of the foot (i.e., balanced flexion). Efficacy was assessed using a 3-dimensional motion analysis of the ankle and foot trajectories during walking with and without stimulation. Without stimulation, the toe on the affected leg drags across the ground. BION stimulation of the TA muscle and deep peroneal nerve (which innervates TA and EDL) elevates the foot such that the toe clears the ground by 3 cm, which is equivalent to the toe clearance in the less affected leg. The physiological cost index (PCI) measured effort during walking. The PCI equals the change in heart rate (from rest to activity) divided by the walking speed; units are beats per metre. The PCI is high without stimulation (2.29 ± 0.37, mean ± SD) and greatly reduced with surface (1.29 ± 0.10) and BIONic stimulation (1.46 ± 0.24). Also, walking speed increased from 9.4 ± 0.4 m/min without stimulation to 19.6 ± 2.0 m/min with surface and 17.8 ± 0.7 m/min with BIONic stimulation. These results suggest that FES delivered by a BION is an alternative to surface stimulation and provides selective control of muscle activation.Key words: FES, BION, foot drop, stroke, spinal cord injury.

Spinal cord injury: promising interventions and realistic goals

Long regarded as impossible, spinal cord repair is approaching the realm of reality as efforts to bridge the gap between bench and bedside point to novel approaches to treatment. It is important to recognize that the research playing field is rapidly changing and that new mechanisms of resource development are required to effectively make the transition from basic science discoveries to effective clinical treatments. This article reviews recent laboratory studies and phase 1 clinical trials in neural and nonneural cell transplantation, stressing that the transition from basic science to clinical applications requires a parallel rather than serial approach, with continuous, two-way feedback to most efficiently translate basic science findings, through evaluation and optimization, to clinical treatments. An example of mobilizing endogenous stem cells for repair is reviewed, with emphasis on the rapid application of basic science to clinical therapy. Successful and efficient transition from basic science to clinical applications requires (1) a parallel rather than a serial approach; (2) development of centers that integrate three spheres of science, translational, transitional, and clinical trials; and (3) development of novel resources to fund the most critically limited step of transitional to clinical trials.

Treadmill walking in incomplete spinal-cord-injured subjects: 2. Factors limiting the maximal speed

STUDY DESIGN/METHODS

Five SCI subjects referred to the laboratory and a convenience sample of five normal volunteer individuals was selected. Stride length and frequency were measured at different walking speeds under three different conditions: preferred, highest possible and lowest possible stepping frequencies.

OBJECTIVE

To determine which factors are limiting the maximal walking speed in spinal-cord-injured (SCI) individuals.

SETTING

University-Based Human Gait Laboratory, Montreal, Canada.

RESULTS

It is shown that maximal stride frequency was the predominant limiting factor of the maximal treadmill-walking speed in SCI subjects. These results were explained in the light of the forced hybrid mass-spring pendulum model. At all speeds, SCI subjects spent longer time in stance, swing and double support phases. The relative time spent in single support is greater at higher walking speed and the difficulty to reduce double support time is a limiting factor.

CONCLUSIONS

A better understanding of the factors limiting the maximal speed in SCI subjects should help developing rehabilitation interventions oriented towards increasing the control and the capacity of walking. Rehabilitation strategies should put the emphasis on improving the capacity to produce rapid alternate rhythmical stepping movements of the lower limbs.

SPONSORSHIP

Neuroscience Network of the Canadian Centre of Excellence.

The effect of locomotor training combined with functional electrical stimulation in chronic spinal cord injured subjects: walking and reflex studies

With the new developments in traumatology medicine, the majority of spinal cord injuries sustained are clinically incomplete and the proportion is likely to continue to rise. Thus, it is necessary to continue to develop new treatment and rehabilitation strategies and understand the factors that can enhance recovery of walking following spinal cord injury (SCI). One new development is the use of functional electrical stimulation (FES) device to assist locomotion. The objective of this review is to present findings from some recent studies on the effect of long-term locomotor training with FES in subjects with SCI. Promising results are shown in all outcome measures of walking, such as functional mobility, speed, spatio-temporal parameters, and the physiological cost of walking. Furthermore, the change in the walking behavior could be associated with plasticity in the CNS organization, as seen by the modification of the stretch reflex and changes in the corticospinal projection to muscles of the lower leg. In conclusion, recovery of walking is an increasing possibility for a large number of people with SCI. New modalities of treatment have become available for this population but most still need to be evaluated for their efficacy. This review has focused on FES assisted walking as a therapeutic modality in subjects with chronic SCI, but it is envisaged that the care and recovery of SCI in the early phase of recovery could also be improved.