Locomotion in patients with spinal cord injuries

The use of a detailed video-based locomotor pattern analysis system to assess the functional reinnervation of denervated hind limb muscles

BACKGROUND

Spinal cord injuries induce a critical loss of motoneurons followed by irreversible locomotor function impairment. Surgical approaches combined with neuroprotective agents effectively rescue the damaged motoneurons and improve locomotor function. Our aim was to develop a reliable method which is able to provide quantifiable and in-depth data on the locomotor recovery during skeletal muscle reinnervation.

NEW METHOD

Sprague-Dawley rats underwent lumbar 4 ventral root avulsion and reimplantation followed by riluzole treatment in order to rescue the injured motoneurons of the damaged pool. Control animals were operated, but received no riluzole treatment. The locomotor pattern of the hind limb was recorded biweekly on a special runway equipped with high resolution and high speed digital cameras producing both lateral and rear views simultaneously. All together 12 parameters of the hind limb movement pattern were evaluated by measuring specific joint angles, footprints and gait parameters in single video frames. Four months after the operation Fast Blue, a fluorescent retrograde tracer was applied to the L4 spinal nerve in order to label the reinnervating motoneurons.

RESULTS

Our results confirmed the sensitivity of our arrangement and established strong relationship between the functional improvement and the morphological reinnervation. Moreover, we developed a correction method to make the system tolerant to the differences in the weight, step duration and step length.

COMPARISON WITH EXISTING METHODS

There are no commercially available cheap, multi-parametric analysing equipment to characterise the gait in its complexity.

CONCLUSIONS

Our system offers a modular, adaptable and expandable analysis on the reinnervation of the limb musculature in rodents.

Balance, gait, and falls in spinal cord injury

This chapter covers balance, gait, and falls in individuals with spinal cord injury (SCI) from a clinical perspective. First, the consequences of an SCI on functioning are explained, including etiology, clinical presentation, classification, and epidemiologic data. Then, the specific aspects of balance disorders, gait disorders, and falls are discussed with respect to motor complete (cSCI) and incomplete (iSCI) SCI. Typically, these activities are affected by impaired afferent and efferent nerves, but not by central nervous processing. Performance of daily life activities in cSCI depends on the ability to control the interaction between the center of mass and the base of support or limits of stability. In iSCI, impaired proprioception and muscle strength are important factors for completing balancing tasks and for walking. Falls are common in patients with SCI. Subsequent sections describe therapy approaches aimed at modifying balance, gait, and the risk for falls by means of therapeutic exercises, assistive devices like robots or functional electric stimulation, and environmental adaptations. The last part covers recent developments and future directions. These encompass interventions for maximizing residual neural function and regeneration of axons, as well as technical solutions like epidural or intraspinal electric stimulation, powered exoskeletons, and brain computer interfaces.

Strategies to augment volitional and reflex function may improve locomotor capacity following incomplete spinal cord injury

Many studies highlight the remarkable plasticity demonstrated by spinal circuits following an incomplete spinal cord injury (SCI). Such plasticity can contribute to improvements in volitional motor recovery, such as walking function, although similar mechanisms underlying this recovery may also contribute to the manifestation of exaggerated responses to afferent input, or spastic behaviors. Rehabilitation interventions directed toward augmenting spinal excitability have shown some initial success in improving locomotor function. However, the potential effects of these strategies on involuntary motor behaviors may be of concern. In this article, we provide a brief review of the mechanisms underlying recovery of volitional function and exaggerated reflexes, and the potential overlap between these changes. We then highlight findings from studies that explore changes in spinal excitability during volitional movement in controlled conditions, as well as altered kinematic and behavioral performance during functional tasks. The initial focus will be directed toward recovery of reflex and volitional behaviors following incomplete SCI, followed by recent work elucidating neurophysiological mechanisms underlying patterns of static and dynamic muscle activation following chronic incomplete SCI during primarily single-joint movements. We will then transition to studies of locomotor function and the role of altered spinal integration following incomplete SCI, including enhanced excitability of specific spinal circuits with physical and pharmacological interventions that can modulate locomotor output. The effects of previous and newly developed strategies will need to focus on changes in both volitional function and involuntary spastic reflexes for the successful translation of effective therapies to the clinical setting.

Effectiveness of Automated Locomotor Training in Patients with Acute Incomplete Spinal Cord Injury: A Randomized, Controlled, Multicenter Trial

The aim of this study was to evaluate whether the effect of longer training times (50 instead of 25 min per day) using a robotic device results in a better outcome of walking ability of subjects with a subacute motor complete (American Spinal Injury Association Impairment Scale [AIS]-B) and incomplete (AIS-C) spinal cord injury. Twenty-one patients were enrolled in the study, whereof 18 completed, on average, 34 trainings in 8 weeks. Longer training times resulted in better locomotor function. The second important result of the study is that a beneficial effect can be achieved by the application of a robotic device for prolonged training sessions without requiring more personal resources. It has to remain open whether even longer training times (more than 50 min) would result in a still better outcome. In any case, the extent of possible recovery in an individual patient is determined by the level and severity of spinal cord damage.

Intermittent Hypoxia and Locomotor Training Enhances Dynamic but Not Standing Balance in Patients With Incomplete Spinal Cord Injury

OBJECTIVE

To test the effect of combined intermittent hypoxia (IH) and body weight-supported treadmill training (BWSTT) on standing and dynamic balance in persons with incomplete spinal cord injury (iSCI).

DESIGN

Randomized, triple-blind, placebo-controlled study.

SETTING

Rehabilitation medical centers.

PARTICIPANTS

Study participants (N=35) with chronic iSCI with American Spinal Injury Association grades C and D (>1y postinjury) were randomly assigned to either IH plus BWSTT (n=18) or continued normoxia (placebo) plus BWSTT protocol (n=17).

INTERVENTIONS

Participants received either IH (alternating 1.5min 9% inspired O₂ with 1.5min 21% inspired O₂, 15 cycles per day) or continued normoxia (21% O₂) combined with 45 minutes of BWSTT for 5 consecutive days, followed by 3 times per week IH or normoxia plus BWSTT, for 3 additional weeks.

MAIN OUTCOME MEASURES

Standing balance (normalized jerk and root-mean-square [RMS]) and dynamic balance (turning duration, cadence in a turn, and turn-to-sit duration) were assessed before and after IH and normoxia protocol by means of instrumented sway and instrumented timed Up and Go test.

RESULTS

There was no significant difference in standing balance between interventions for both normalized jerk and RMS instrumented sway components (both P>.05). There was a significantly faster cadence (P<.001), turning duration (P<.001), and turn-to-sit duration (P=.001) in subjects receiving IH plus BWSTT, compared with placebo.

CONCLUSIONS

A 4-week protocol of IH combined with locomotor training improves dynamic, but not standing, balance in persons with iSCI.

The motor output of hindlimb innervating segments of the spinal cord is modulated by cholinergic activation of rostrally projecting sacral relay neurons

Cholinergic networks have been shown to be involved in generation and modulation of the locomotor rhythmic pattern produced by the mammalian central pattern generators. Here, we show that changes in the endogenous levels of acetylcholine in the sacral segments of the isolated spinal cord of the neonatal rat modulate the locomotor-related output produced by stimulation of sacrocaudal afferents in muscarinic receptor-dependent mechanisms. Cholinergic components we found on sacral relay neurons with lumbar projections through the ventral and lateral funiculi are suggested to mediate this ascending cholinergic modulation. Our findings, possible mechanisms accounting for them, and their potential implications are discussed.

Effect of combined treadmill training and magnetic stimulation on spasticity and gait impairments after cervical spinal cord injury

Spasticity and gait impairments are two common disabilities after cervical spinal cord injury (C-SCI). In this study, we tested the therapeutic effects of early treadmill locomotor training (Tm) initiated at postoperative (PO) day 8 and continued for 6 weeks with injury site transcranial magnetic stimulation (TMSsc) on spasticity and gait impairments after low C6/7 moderate contusion C-SCI in a rat model. The combined treatment group (Tm+TMSsc) showed the most robust decreases in velocity-dependent ankle torques and triceps surae electromyography burst amplitudes that were time locked to the initial phase of lengthening, as well as the most improvement in limb coordination quantitated using three-dimensional kinematics and CatWalk gait analyses, compared to the control or single-treatment groups. These significant treatment-associated decreases in measures of spasticity and gait impairment were also accompanied by marked treatment-associated up-regulation of dopamine beta-hydroxylase, glutamic acid decarboxylase 67, gamma-aminobutyric acid B receptor, and brain-derived neurotrophic factor in the lumbar spinal cord (SC) segments of the treatment groups, compared to tissues from the C-SCI nontreated animals. We propose that the treatment-induced up-regulation of these systems enhanced the adaptive plasticity in the SC, in part through enhanced expression of pre- and postsynaptic reflex regulatory processes. Further, we propose that locomotor exercise in the setting of C-SCI may decrease aspects of the spontaneous maladaptive segmental and descending plasticity. Accordingly, TMSsc treatment is characterized as an adjuvant stimulation that may further enhance this capacity. These data are the first to suggest that a combination of Tm and TMSsc across the injury site can be an effective treatment modality for C-SCI-induced spasticity and gait impairments and provided a pre-clinical demonstration for feasibility and efficacy of early TMSsc intervention after C-SCI.

Characterization of sacral interneurons that mediate activation of locomotor pattern generators by sacrocaudal afferent input

Identification of the neural pathways involved in retraining the spinal central pattern generators (CPGs) by afferent input in the absence of descending supraspinal control is feasible in isolated rodent spinal cords where the locomotor CPGs are potently activated by sacrocaudal afferent (SCA) input. Here we study the involvement of sacral neurons projecting rostrally through the ventral funiculi (VF) in activation of the CPGs by sensory stimulation. Fluorescent labeling and immunostaining showed that VF neurons are innervated by primary afferents immunoreactive for vesicular glutamate transporters 1 and 2 and by intraspinal neurons. Calcium imaging revealed that 55% of the VF neurons were activated by SCA stimulation. The activity of VF neurons and the sacral and lumbar CPGs was abolished when non-NMDA receptors in the sacral segments were blocked by the antagonist CNQX. When sacral NMDA receptors were blocked by APV, the sacral CPGs were suppressed, VF neurons with nonrhythmic activity were recruited and a moderate-drive locomotor rhythm developed during SCA stimulation. In contrast, when the sacral CPGs were activated by SCA stimulation, rhythmic and nonrhythmic VF neurons were recruited and the locomotor rhythm was most powerful. The activity of 73 and 27% of the rhythmic VF neurons was in-phase with the ipsilateral and contralateral motor output, respectively. Collectively, our studies indicate that sacral VF neurons serve as a major link between SCA and the hindlimb CPGs and that the ability of SCA to induce stepping can be enhanced by the sacral CPGs. The nature of the ascending drive to lumbar CPGs, the identity of subpopulations of VF neurons, and their potential role in activating the locomotor rhythm are discussed.

A novel myoelectric pattern recognition strategy for hand function restoration after incomplete cervical spinal cord injury

This study presents a novel myoelectric pattern recognition strategy towards restoration of hand function after incomplete cervical spinal cord Injury (SCI). High density surface electromyogram (EMG) signals comprised of 57 channels were recorded from the forearm of nine subjects with incomplete cervical SCI while they tried to perform six different hand grasp patterns. A series of pattern recognition algorithms with different EMG feature sets and classifiers were implemented to identify the intended tasks of each SCI subject. High average overall accuracies (> 97%) were achieved in classification of seven different classes (six intended hand grasp patterns plus a hand rest pattern), indicating that substantial motor control information can be extracted from partially paralyzed muscles of SCI subjects. Such information can potentially enable volitional control of assistive devices, thereby facilitating restoration of hand function. Furthermore, it was possible to maintain high levels of classification accuracy with a very limited number of electrodes selected from the high density surface EMG recordings. This demonstrates clinical feasibility and robustness in the concept of using myoelectric pattern recognition techniques toward improved function restoration for individuals with spinal injury.

Altered patterns of reflex excitability, balance, and locomotion following spinal cord injury and locomotor training

Spasticity is an important problem that complicates daily living in many individuals with spinal cord injury (SCI). While previous studies in human and animals revealed significant improvements in locomotor ability with treadmill locomotor training, it is not known to what extent locomotor training influences spasticity. In addition, it would be of considerable practical interest to know how the more ergonomically feasible cycle training compares with treadmill training as therapy to manage SCI-induced spasticity and to improve locomotor function. Thus the main objective of our present studies was to evaluate the influence of different types of locomotor training on measures of limb spasticity, gait, and reflex components that contribute to locomotion. For these studies, 30 animals received midthoracic SCI using the standard Multicenter Animal Spinal cord Injury Studies (MASCIS) protocol (10 g 2.5 cm weight drop). They were divided randomly into three equal groups: control (contused untrained), contused treadmill trained, and contused cycle trained. Treadmill and cycle training were started on post-injury day 8. Velocity-dependent ankle torque was tested across a wide range of velocities (612-49°/s) to permit quantitation of tonic (low velocity) and dynamic (high velocity) contributions to lower limb spasticity. By post-injury weeks 4 and 6, the untrained group revealed significant velocity-dependent ankle extensor spasticity, compared to pre-surgical control values. At these post-injury time points, spasticity was not observed in either of the two training groups. Instead, a significantly milder form of velocity-dependent spasticity was detected at postcontusion weeks 8-12 in both treadmill and bicycle training groups at the four fastest ankle rotation velocities (350-612°/s). Locomotor training using treadmill or bicycle also produced significant increase in the rate of recovery of limb placement measures (limb axis, base of support, and open field locomotor ability) and reflex rate-depression, a quantitative assessment of neurophysiological processes that regulate segmental reflex excitability, compared with those of untrained injured controls. Light microscopic qualitative studies of spared tissue revealed better preservation of myelin, axons, and collagen morphology in both locomotor trained animals. Both locomotor trained groups revealed decreased lesion volume (rostro-caudal extension) and more spared tissue at the lesion site. These improvements were accompanied by marked upregulation of BDNF, GABA/GABA(b), and monoamines (e.g., norepinephrine and serotonin) which might account for these improved functions. These data are the first to indicate that the therapeutic efficacy of ergonomically practical cycle training is equal to that of the more labor-intensive treadmill training in reducing spasticity and improving locomotion following SCI in an animal model.

Evidence-based therapy for recovery of function after spinal cord injury

Physical rehabilitation for individuals coping with neurological deficits is evolving in response to a paradigm shift in thinking about the injured nervous system and using evidence as a basis for clinical decisions. Functional recovery from paralysis was generally believed to be nearly impossible, based on traditional expert opinion, and the priority was to develop compensation strategies to achieve functional goals in the home and community. Research, which began in animal models of neurological insult and is currently being translated to the clinic, has challenged these assumptions. The nervous system, whether intact or injured, has enormous potential for adaptation and modification, which can be harnessed to facilitate recovery. In this chapter we will briefly outline the history of physical rehabilitation as it concerns the development of strategies aimed at compensation, rather than functional recovery. Then we will discuss how new activity-based therapies are being developed, based on evidence from basic science and clinical evidence. One of these activity-based therapies is locomotor training, a program which relies on the intrinsic, automatic, control of locomotion by "lower" neural centers. A brief description of the program, including the four foundational principles, will be followed by an introduction to the use of robotics in these programs. Finally, we will discuss a second activity-based therapy, functional electrical stimulation (FES), and the future of physical rehabilitation for spinal cord injury and other neurological disorders.

Molecular Mechanisms Underlying Cell Death in Spinal Networks in Relation to Locomotor Activity After Acute Injury in vitro

Understanding the pathophysiological changes triggered by an acute spinal cord injury is a primary goal to prevent and treat chronic disability with a mechanism-based approach. After the primary phase of rapid cell death at the injury site, secondary damage occurs via autodestruction of unscathed tissue through complex cell-death mechanisms that comprise caspase-dependent and caspase-independent pathways. To devise novel neuroprotective strategies to restore locomotion, it is, therefore, necessary to focus on the death mechanisms of neurons and glia within spinal locomotor networks. To this end, the availability of in vitro preparations of the rodent spinal cord capable of expressing locomotor-like oscillatory patterns recorded electrophysiologically from motoneuron pools offers the novel opportunity to correlate locomotor network function with molecular and histological changes long after an acute experimental lesion. Distinct forms of damage to the in vitro spinal cord, namely excitotoxic stimulation or severe metabolic perturbation (with oxidative stress, hypoxia/aglycemia), can be applied with differential outcome in terms of cell types and functional loss. In either case, cell death is a delayed phenomenon developing over several hours. Neurons are more vulnerable to excitotoxicity and more resistant to metabolic perturbation, while the opposite holds true for glia. Neurons mainly die because of hyperactivation of poly(ADP-ribose) polymerase-1 (PARP-1) with subsequent DNA damage and mitochondrial energy collapse. Conversely, glial cells die predominantly by apoptosis. It is likely that early neuroprotection against acute spinal injury may require tailor-made drugs targeted to specific cell-death processes of certain cell types within the locomotor circuitry. Furthermore, comparison of network size and function before and after graded injury provides an estimate of the minimal network membership to express the locomotor program.

Mechanisms involved in treadmill walking improvements in Parkinson's disease

Patients with Parkinson's disease (PD) improve gait after treadmill training and while they are walking over the treadmill. However, the mechanisms of these improvements have not been addressed. We designed a treadmill simulator without a belt that could move on a walkway in a constant speed, in order to explore the mechanism underlying treadmill walking improvements in PD. All subjects were tested in three different sessions (treadmill, simulator(assisted) and simulator(not assisted)). In each session, subjects first walked overground and then walked using the treadmill or simulator with the hands over the handrails (simulator(assisted)) or with the hands free (simulator(not assisted)). Step length, cadence, double support time, swing time, support time and the coefficient of variation (CV) of step time and double support time were recorded. Over the treadmill PD patients increased their step length and reduced significantly their cadence and CV of double support time in comparison with overground walking. In the simulator(assisted) condition PD patients reduced significantly the CV of double support time in comparison with overground walking. With the simulator(not assisted) both groups decreased their step length and increased their cadence and CV of double support time, compared with walking overground. These findings suggest that the step length improvement observed in PD patients, walking over a treadmill, is due to the proprioceptive information generated by the belt movement, since no improvement was reported when patients using a treadmill simulator.

Treadmill walking in Parkinson's disease patients: adaptation and generalization effect

We examined the adaptation and generalization effect of one familiarization treadmill walking session on gait in patients with Parkinson's disease (PD) with different degrees of disease severity. Eight moderate PD patients (Hoehn and Yahr stage 2-2.5), eight advanced PD patients (Hoehn and Yahr 3), and eight matched control subjects participated in this study. Subjects first walked overground on a 10-m walkway at a self-selected speed (pretreadmill). They then performed a 20-min treadmill training session, followed by three trials of overground walking (Post1, Post2, Post3). Cadence, step length, speed, and coefficient of variation of stride time (CV) were recorded. During the treadmill session the advanced PD patients significantly decreased their cadence (t = 3.9, P <or= 0.01) and increased their step length (t = 4.27, P <or= 0.01) compared with pretreadmill walking. After the treadmill, all subjects walked overground significantly faster (F = 16.51 P <or= 0.001) and with a larger step length (F = 13.03 P <or= 0.01) than pretreadmill walking. The present study shows a specific adaptation to walk over the treadmill for the advanced PD patients. Moreover, this confirms the potential therapeutic use of the treadmill for PD gait rehabilitation since a single familiarization session lead to an increase in the step length and thus to the improvement of the main gait impairment in PD.

The effects of tone-reducing orthotics on walking of an individual after incomplete spinal cord injury

PURPOSE

Most literature about the efficacy of tone-reducing orthotics pertains to adults and children with central nervous system (CNS) pathology. There is relatively little mention of using this type of orthotic with adults after spinal cord injury (SCI). Therefore, the purpose of this study was to investigate whether tone-reducing orthotics have an effect on gait including electromyographic (EMG) activity, velocity, step length, time in double-limb support, and SCI-Functional Ambulation Inventory (SCI-FAI) scores for an individual with incomplete SCI and spasticity.

METHODS

We used a single case design. The subject was a 25-year-old white male who was 16 months post-injury with a diagnosis of T6 left/T9 right sensory, L3 motor American Spinal Injury Association C incomplete SCI. Five different walking conditions were tested during each of two separate sessions: barefoot, shoes, foot plates, one ankle-foot orthosis (AFO) with a joint, and one with a tone-reducing AFO, and tone-reducing AFOs bilaterally. Surface EMG was used to record electrical activity of four muscle groups bilaterally. Step length, gait velocity, and time in double limb support were calculated for all five walking conditions. Gait parameters were further analyzed with video analysis using the SCI-FAI.

RESULTS

Mean EMG was relatively constant in all muscle groups under all walking conditions with the exception of the gastrocnemius. In this muscle group, EMG activity with the use of tone-reducing orthotics was better modulated than the other conditions. Gait velocity and step length both increased with tone-reducing orthotics, whereas double limb support time decreased, thus improving the corresponding SCI-FAI score accordingly.

CONCLUSION

The subject showed improvement in the control of his lower extremities while wearing bilateral tone-reducing AFOs as evidenced by an increased step length and gait velocity and a decrease in the amount of time spent in double limb support. Electromyographic data were less conclusive, although activity in the left gastrocnemius muscle group was more erratic under alternative walking conditions when compared to the tone-reducing AFOs.

Plasticity of interneuronal networks of the functionally isolated human spinal cord

The loss of walking after human spinal cord injury has been attributed to the dominance of supraspinal over spinal mechanisms. The evidence for central pattern generation in humans is limited due to the inability to conclusively isolate the circuitry from descending and afferent input. However, studying individuals following spinal cord injury with no detectable influence on spinal networks from supraspinal centers can provide insight to their interaction with afferent input. The focus of this article is on the interaction of sensory input with human spinal networks in the generation of locomotor patterns. The functionally isolated human spinal cord has the capacity to generate locomotor patterns with appropriate afferent input. Locomotor Training is a rehabilitative strategy that has evolved from animal and humans studies focused on the neural plasticity of the spinal cord and has been successful for many people with acute and chronic incomplete spinal cord injury. However, even those individuals with clinically complete spinal cord injury that generate appropriate locomotor patterns during stepping with assistance on a treadmill with body weight support cannot sustain overground walking. This suggests that although a significant control of locomotion can occur at the level of spinal interneuronal networks the level of sustainable excitability of these circuits is still compromised. Future studies should focus on approaches to increase the central state of excitability and may include neural repair strategies, pharmacological interventions or epidural stimulation in combination with Locomotor Training.

Disability and determinants of gait performance in tropical spastic paraparesis/HTLV-I associated myelopathy (HAM/TSP)

STUDY DESIGN

Cross-sectional.

OBJECTIVES

The aim of this survey is to describe the disability profile in a group of tropical spastic paraparesis/HTLV-I-associated myelopathy patients, identifying the requirements for community ambulation.

SETTING

Tertiary care unit, Rio de Janeiro, Brazil.

METHODS

Seventy-two patients were assessed (49 female and 23 male), referred by tertiary care centers, when a clinical protocol was applied.

RESULTS

The sample had an average age of 40 years and an average of 137 months of duration of the disease. The most prevalent aspects of disability found were in gait and sphincter control areas. A total of 72% of the patients were community ambulators and 17% were restricted to wheel chair. Age, strength and low-back pain interfere in activities of daily living (P<0.05). A positive correlation was found between community ambulation and the knee extensors (r=0.80) and ankle plantar flexors (r=0.74). Strength, age, low-back pain, duration of disease, asymmetric onset of the symptoms and spasticity interfered in the ability to walk (P<0.05). A rehabilitation program was proposed focusing on modifiable factors that affect disability level.

CONCLUSION

It was possible to describe the profile of disability in this group of patients, identifying the requirements to the community ambulation.

The effects of body-weight supported treadmill training on cardiovascular regulation in individuals with motor-complete SCI

STUDY DESIGN

Four-month longitudinal within-subject exercise training study.

OBJECTIVE

Although body-weight supported treadmill training (BWSTT) has not shown promise as a means of improving ambulation in individuals with motor-complete spinal cord injury (SCI), it may still improve cardiovascular health and function in this population. The purpose of this study was to (i) investigate the effects of BWSTT on peripheral muscular and elastic artery dimension and function and measures of heart rate variability (HRV) and blood pressure variability (BPV) in individuals with motor-complete SCI, and (ii) to make a preliminary examination of what factors may predict favourable cardiovascular outcomes following BWSTT in this population.

SETTING

Centre for Health Promotion and Rehabilitation, McMaster University, Hamilton, Ontario, Canada.

METHODS

Six individuals (four male, two female; age 37.7+/-15.4 years) with chronic SCI (C4-T12; ASIA A-B; 7.6+/-9.4 years post-injury) were included in the present investigation. Doppler ultrasound was used to determine femoral (exercising; muscular), carotid (elastic) and brachial (non-exercising control; muscular) artery dimension and function before and after 4 months of BWSTT. Continuous heart rate and blood pressure were also recorded before and after 4-months of BWSTT to determine frequency domain measures of HRV and BPV; clinically valuable indices of neurocardiac and neurovascular control, respectively.

RESULTS

Two-way ANOVA (vessel x time) revealed no exercise-induced change in femoral or carotid artery cross-sectional area, blood flow or resistance and no change in carotid artery compliance following the 4 months of BWSTT compared to the non-exercising control brachial artery. However, there was a significant exercise-induced increase in femoral artery compliance. There were no exercise-induced changes in HRV or BPV when all participants were considered together. However, the results suggest that the subgroup of individuals who had a substantial heart rate response to BWSTT (n=3), experienced exercise-training induced changes in HRV reflective of a relative shift toward cardiac vagal predominance and reductions in BPV.

CONCLUSIONS

BWSTT may cause an increase in femoral artery compliance in individuals with motor-complete SCI and therefore, should be encouraged as a means of improving cardiovascular health in this population. BWSTT may also cause modest improvements in measures of HRV and BPV in a select subgroup of individuals who respond to ambulation with moderate to large increases in HR. In the present study, factors associated with a substantial HR response to BWSTT were a propensity to orthostatic intolerance and muscular spasticity.

Influence of passive leg movements on blood circulation on the tilt table in healthy adults

Background

One problem in the mobilization of patients with neurological diseases, such as spinal cord injury, is the circulatory collapse that occurs while changing from supine to vertical position because of the missing venous pump due to paralyzed leg muscles. Therefore, a tilt table with integrated stepping device (tilt stepper) was developed, which allows passive stepping movements for performing locomotion training in an early state of rehabilitation. The aim of this pilot study was to investigate if passive stepping and cycling movements of the legs during tilt table training could stabilize blood circulation and prevent neurally-mediated syncope in healthy young adults.

Methods

In the first experiment, healthy subjects were tested on a traditional tilt table. Subjects who had a syncope or near-syncope in this condition underwent a second trial on the tilt stepper. In the second experiment, a group of healthy subjects was investigated on a traditional tilt table, the second group on the tilt ergometer, a device that allows cycling movements during tilt table training. We used the chi-square test to compare the occurrence of near-syncope/syncope in both groups (tilt table/tilt stepper and tilt table/tilt ergometer) and ANOVA to compare the blood pressure and heart rate between the groups at the four time intervals (supine, at 2 minutes, at 6 minutes and end of head-up tilt).

Results

Separate chi-square tests performed for each experiment showed significant differences in the occurrence of near syncope or syncope based on the device used. Comparison of the two groups (tilt stepper/ tilt table) in experiment one (ANOVA) showed that blood pressure was significantly higher at the end of head-up tilt on the tilt stepper and on the tilt table there was a greater increase in heart rate (2 minutes after head-up tilt). Comparison of the two groups (tilt ergometer/tilt table) in experiment 2 (ANOVA) showed that blood pressure was significantly higher on the tilt ergometer at the end of head-up tilt and on the tilt table the increase in heart rate was significantly larger (at 6 min and end of head-up tilt).

Conclusions

Stabilization of blood circulation and prevention of benign syncope can be achieved by passive leg movement during a tilt table test in healthy adults.

Temporal differences in relative phasing of gait initiation and first step length in patients with cervical and lumbosacral spinal cord injuries

STUDY DESIGN

Comparison group design.

OBJECTIVE

To compare the temporal distance factors during gait initiation between patients with incomplete cervical spinal cord injury, incomplete lumbosacral spinal lesion, and unimpaired control adults.

SETTING

Human performance and movement analysis laboratory, Taiwan.

PARTICIPANTS

Five patients with an incomplete cervical spinal cord injury (Group 1), five patients with an incomplete lumbosacral spinal lesion (Group 2) and nine unimpaired control adults (Group 3).

METHODS

Subjects underwent a three-dimensional gait analysis. The total gait initiation period, reaction time, each relative phasing of gait initiation and the length of the first step were identified by using the kinematic measurement system.

MAIN OUTCOME MEASURES

The total gait initiation period (start of the auditory cue for gait initiation to heel-strike of the first swing leg); each relative phasing of gait initiation indicated that the duration of the preparatory phase (start of auditory cue for gait initiation to heel-off of the first swing leg), the duration of the push-up phase (heel-off to toe-off of the first swing leg), and the duration of the single-stance phase (toe-off to heel-strike of the first swing leg) established by the total gait initiation period; and the length of the first step.

RESULTS

The gait initiation period was greater in Groups 1 and 2 than that of Group 3 (P<0.05). Each relative phasing including the duration of the preparatory phase, the push-up phase, and the swing phase relative to the total gait initiation period, did not differ among Groups 1-3 (P>0.05). The length of the first step, measured while the nonpreferred leg stepped first in Groups 1 and 2, was shorter than that of Group 3 (P<0.05).

CONCLUSIONS

Patients with incomplete cervical spinal cord injuries or lumbosacral spinal lesions took more time in gait initiation than unimpaired control adults. The first step length also reduced in these patients while the nonpreferred leg stepped first, as compared to unimpaired control adults. The data indicated that centrally programmed gait initiation might be preserved in ASIA-D spinal patients who, in this study, executed gait initiation with varying temporal distance strategies to compensate for peripheral impairments, as compared to unimpaired control adults.

Recurrent paraplegia after remyelination of the spinal cord

We have conducted a long-term study of spinal cord morphology and motor function recovery in rats that have undergone lumbar spinal demyelination induced by the B-fragment of cholera toxin (CTB)-saporin. We found that, after the initial demyelination and paraplegia, motor function recovered and was stable for up to 9 months, after which there occurred a slow deterioration of motor function accompanied by loss of motoneurons and loss of spinal white matter. A striking morphological feature was the appearance of large spheroids of calcium in the ventral and dorsal horns and occasionally in the white matter. Motor performance deterioration occurred earlier and was more severe in rats that had been exercised on a treadmill, but the same morphological changes occurred in both exercise- and nonexercise-treated animals. Rats given treadmill exercise starting 3 weeks after toxin injection had a mean motor deficit score of 3.0 (i.e., paraplegia) at perfusion, whereas the nontreadmill-treated rats had a mean score of 1.8 (SD 0.38; n = 6; P <.05). These findings suggest that, in addition to the acute effects of the toxin-induced demyelination from which there is recovery of motor function, there are chronic irreversible effects of the toxin, or the initial demyelination, that cause a slow progressive degeneration of the spinal cord. This model might therefore be useful in studying the long-term effects of spinal insult of the type associated with conditions such as postpolio syndrome.

Short-term effects of functional electrical stimulation on motor-evoked potentials in ankle flexor and extensor muscles

Stimulating sensory afferents can increase corticospinal excitability. Intensive use of a particular part of the body can also induce reorganization of neural circuits (use-dependent plasticity) in the central nervous system (CNS). What happens in the CNS when the nerve stimulation is applied in concert with the use of particular muscle groups? The purpose of this study was to investigate short-term effects of electrical stimulation of the common peroneal (CP) nerve during walking on motor-evoked potentials (MEPs) in the ankle flexors and extensors in healthy subjects. Since the stimulation was applied during the swing phase of the step cycle when the ankle flexors are active, this is referred to as functional electrical stimulation (FES). The following questions were addressed: (1) can FES during walking increase corticospinal excitability more effectively than passively received repetitive nerve stimulation and (2) does walking itself improve the descending connection. FES was delivered using a foot drop stimulator that activates ankle dorsiflexors during the swing phase of the step cycle. MEPs in the tibialis anterior (TA) and soleus muscles were measured before, between, and after periods of walking with or without FES, using transcranial magnetic stimulation. After 30 min of walking with FES, the half-maximum peak-to-peak MEP (MEP(h)) in the TA increased in amplitude and this facilitatory effect lasted for at least 30 min. In contrast, walking had no effects on the TA MEP(h) without FES. The increase in the TA MEP(h) with FES (approximately 40%) was similar to that with repetitive CP nerve stimulation at rest. The soleus MEP(h) was also increased after walking with FES, but not without FES, which differs from the previous observation with CP nerve stimulation at rest. With FES, the TA silent period at MEP(h) was unchanged or slightly decreased, while it increased after walking without FES. Increased cortical excitability accompanied by unchanged cortical inhibition (no changes in the silent period with FES) suggests that FES did not simply increase general excitability of the cortex, but had specific effects on particular cortical neurons.

Epidural spinal-cord stimulation facilitates recovery of functional walking following incomplete spinal-cord injury

We investigated a novel treatment paradigm for developing functional ambulation in wheelchair-dependent individuals with chronic, incomplete spinal-cord injury. By coordinating epidural stimulation of the dorsal structures of the spinal cord with partial weight bearing treadmill therapy, we observed improvement in treadmill and over-ground ambulation in an individual with chronic incomplete tetraplegia. The application of partial weight-bearing therapy alone was not sufficient to achieve functional ambulation over ground, though treadmill ambulation improved significantly. Combining epidural spinal-cord stimulation (ESCS, T10-T12 vertebral levels) with partial weight-bearing therapy resulted in further improvement during treadmill ambulation. Moreover, the combination of therapies facilitated the transfer of the learned gait into over ground ambulation. Performance improvements were elicited by applying continuous, charge-balanced, monophasic pulse trains at a frequency of 40-60 Hz, a pulse duration of 800 micros, and an amplitude determined by the midpoint (50%) between the sensory and motor threshold values. The participant initially reported a reduction in sense of effort for over ground walking from 8/10 to 3/10 (Borg scale), and was able to double his walking speed. After several weeks of over ground training, he reached maximum walking speeds of 0.35 m/s, and was able to ambulate over 325 m. We propose that ESCS facilitated locomotor recovery in this patient by augmenting the use-dependent plasticity created by partial weight bearing therapy. Confirmation of these promising results in a controlled study of groups of spinal-cord-injured subjects is warranted.

Recovery from spinal cord injury--underlying mechanisms and efficacy of rehabilitation

Patients with an acute complete spinal cord injury (SCI) present a syndrome called "spinal shock". During spinal shock the loss of tendon reflexes and flaccid muscle tone is associated with a low persistence of F-waves and loss of flexor reflexes while H-reflexes are well elicitable. When clinical signs of spasticity become established, the electrophysiological parameters show little change. The divergent course of clinical signs of spasticity in their possible neuronal correlates indicate the occurrence of non-neuronal changes contributing to spasticity. - When signs of spinal shock had disappeared in patients with incomplete and complete paraplegia a locomotor pattern can be induced and trained under conditions of body unlaoding using a moving treadmill. In complete and incomplete paraplegic patients an increase of gastrocnemius electromyographic activity occurs during the stance phase of a step cycle with a daily locomotor training, coincident with a significant decrease of body unloading. In contrast to this, neither clinical nor electrophysiological examination scores improve. The locomotor pattern depends on the level of lesion: the higher the level of spinal cord lesion the more 'normal' is the locomotor pattern. This suggests that neuronal circuits underlying 'locomotor pattern generation' in man is not restricted to any specific level of the spinal cord, but extends from thoraco-lumbal to cervical levels.

[Reha-Stepper locomotion therapy in early rehabilitation of paraplegic patients]

Treadmill training with partial body weight support was shown to significantly improve the constitution and gait capacity of incomplete spinal cord injured (SCI) persons. The main requirement for application of this therapy is a sufficient capacity of the cardiovascular system. Most of the SCI patients do not comply with this requirement in the first few weeks after spinal cord injury, where spinal reflexes are frequently missing (spinal shock). To offer SCI patients a locomotion therapy at this early stage of rehabilitation we developed a novel, active tilt-table, the Reha-Stepper, that moves the lower limbs in an almost physiological manner in terms of kinematic and kinetic parameters. The tilt of the device can be continuously increased from horizontal to almost upright position adapted to the status of the patient.

Treadmill ambulation with partial body weight support for the treatment of low back and leg pain

STUDY DESIGN

A single-subject experimental design using an A-B-A treatment protocol.

OBJECTIVE

To determine whether walking on a treadmill with partial body weight support (PBWS) would be an effective adjunct treatment method to standard care for decreasing pain and increasing function in patients suffering from low back and leg pain.

BACKGROUND

Mechanical low back pain (LBP) is commonly aggravated by activities that increase axial loading in the spine, such as sitting, standing, and walking. Patients with mechanical LBP usually describe relief with positions that unload the spine. One traction technique now being used in clinics to unload the spine is the PBWS system. The use of endurance exercise has also been found to be a consistent predictor of better outcomes in patients with LBP. Thus treatment that combines spinal unloading using PBWS and endurance exercise may be an effective intervention for patients with low back and leg pain.

METHODS AND MEASURES

Eleven subjects participated in this study using an A-B-A design. Phase A was defined as the baseline condition and phase B was intervention with PBWS provided by a mechanical unloading system. The Roland-Morris Questionnaire (RMQ) and Visual Analog Scale (VAS) were utilized to collect data on functional status and perceived pain, respectively. Visual Analysis and 2 standard deviation band method (2SDBM) were used to analyze the data.

RESULTS

Pain scores between baseline and PBWS treatment phases were significantly improved for 3 out of the 6 subjects who completed the study. RMQ baseline and treatment scores revealed that 5 out of 6 subjects had significant functional improvements in the PBWS treatment phase.

CONCLUSION

The results suggest that ambulation with PBWS combined with the standard level of care for this population holds sufficient promise for pain relief and functional improvement to justify testing its efficacy in larger groups of subjects with these complaints.

Spinal cord injury medicine. 3. Rehabilitation outcomes

This self-directed learning module highlights rehabilitation outcomes in spinal cord injury (SCI). It is part of the chapter on SCI medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article focuses on the multiple concerns for functional recovery after SCI, chiefly, the potential for ambulation, upper-extremity recovery, options for functional neuromuscular stimulation (FNS), sexual activity, and optimal outcome after a metastatic lesion. Motor incomplete patients have a better prognosis for ambulation than persons with sensory incomplete injury. Positive predictors for ambulation, including pinprick and lower-extremity motor scores greater than 20, are discussed. Meaningful recovery can occur in the upper extremities for at least 1 year. FNS options have been developed to promote functional control of the upper extremities for persons with tetraplegia, phrenic pacing, and bladder continence. A critical component of an individual's expression of self is his/her sexuality; sexual function after SCI is described in detail, including options for treatment of erectile dysfunction and various birth control methods for women. Expectations for an appropriate rehabilitation stay for a person with metastatic SCI differ for an individual with traumatic SCI. Differences may include changing routine pathways and timelines to focus on patient-centered quality of life for transition to home.

OVERALL ARTICLE OBJECTIVE

To identify potential outcomes in ambulation, upper-extremity function, FNS, and sexual function after SCI and after metastatic cancer.

Driven gait orthosis for improvement of locomotor training in paraplegic patients

DESIGN

Single cases.

OBJECTIVE

To compare the effects of manually assisted locomotor training in paraplegic patients with the automated training by a driven gait orthosis.

SETTING

ParaCare, University Hospital Balgrist in Zurich, Switzerland.

METHODS

Treadmill training with manual assistance and by a driven gait orthosis was applied to two spinal cord injured patients. The first patient had an incomplete lesion at C3, the second a complete lesion at C5. They were selected by convenience sample. The EMG activity of the leg muscles rectus femoris, biceps femoris, gastrocnemius medials (GM) and tibialis anterior (TA) was visually compared for the two training methods. GM and TA activity was also quantified by calculating the variation ratio between the EMG of the patients and a set of healthy subjects.

RESULTS

No significant difference between the two training methods was found according to the leg muscle EMG activity.

CONCLUSION

Neuronal centers in the spinal cord become activated in a similar way by the manually assisted and the automated locomotor training. With the driven gait orthosis training sessions can be prolonged and workload of therapists can be reduced, and therefore, the automated training represents an alternative to the conventional therapy.

Low frequency depression of H-reflexes in humans with acute and chronic spinal-cord injury

We measured low-frequency depression of soleus H-reflexes in individuals with acute (n=5) and chronic (n=7) spinal-cord injury and in able-bodied controls (n=7). In one acute subject, we monitored longitudinal changes in low-frequency depression of H-reflexes over 44 weeks and examined the relationship between H-reflex depression and soleus-muscle fatigue properties. Soleus H-reflexes were elicited at 0.1, 0.2, 1, 5, and 10 Hz. The mean peak-to-peak amplitude of ten reflexes at each frequency was calculated, and values obtained at each frequency were normalized to 0.1 Hz. H-reflex amplitude decreased with increasing stimulation frequency in all three groups, but H-reflex suppression was significantly larger in the able-bodied and acute groups than in the chronic group. The acute subject who was monitored longitudinally displayed reduced low-frequency depression with increasing time post injury. At 44 weeks post injury, the acute subject's H-reflex depression was similar to that of chronic subjects, and his soleus fatigue index (assessed with a modified Burke fatigue protocol) dropped substantially, consistent with transformation to faster muscle. There was a significant inverse correlation over the 44 weeks between the fatigue index and the mean normalized H-reflex amplitude at 1, 5, and 10 Hz. We conclude that: (1) the chronically paralyzed soleus muscle displays impaired low-frequency depression of H-reflexes, (2) attenuation of rate-sensitive depression in humans with spinal-cord injury occurs gradually, and (3) changes in H-reflex excitability are generally correlated with adaptation of the neuromuscular system. Possible mechanisms underlying changes in low-frequency depression and their association with neuromuscular adaptation are discussed.

Safety and efficacy of 4-aminopyridine in humans with spinal cord injury: a long-term, controlled trial

STUDY OBJECTIVE

To determine the effects of the long-term administration of 4-aminopyridine (4-AP) on sensorimotor function in humans with long-standing spinal cord injury (SCI).

DESIGN

Randomized, open-label, active-treatment control, dosage-blinded study.

SETTING

University-affiliated, tertiary-level care, Department of Veterans Affairs Medical Center.

PATIENTS

Twenty-one healthy men and women outpatients suffering from traumatic SCI (14 tetraplegic, 7 paraplegic) for 2 years or more.

INTERVENTIONS

Dosages of an immediate-release formulation of 4-AP were titrated. At 3 months, 16 subjects were receiving 4-AP 30 mg/day (high dose); 5 subjects were receiving 4-AP 6 mg/day (low dose) and served as an active-treatment control group.

MEASUREMENTS AND MAIN RESULTS

Composite motor and sensory scores had statistically significant increases at 3 months. Maximal expiratory pressure, maximal inspiratory pressure, forced vital capacity, and forced expiratory volume in 1 second showed clinically meaningful and/or statistically significant increases among patients receiving 4-AP 30 mg/day. These subjects also had significant decreases in spasticity (modified Ashworth Scale). Serial biochemical profiles and electroencephalographs were unchanged from baseline, and no clinically significant drug toxicity was encountered.

CONCLUSIONS

Long-term oral administration of immediate-release 4-AP was associated with improvement in and recovery of sensory and motor function, enhanced pulmonary function, and diminished spasticity in patients with long-standing SCI. 4-Aminopyridine appears to be safe and relatively free from toxicity when administered orally over 3 months. Each patient who received immediate-release 4-AP 30 mg/day showed a response in one or more of the outcome measures.

Incomplete spinal cord injury: neuronal mechanisms of motor recovery and hyperreflexia

OBJECTIVE

To understand neuronal mechanisms of motor recovery and hyperreflexia after incomplete spinal cord injury (SCI), and their role in rehabilitation.

DESIGN

Reviewed and compared clinical, neurophysiologic, and neuropathologic data from human SCI patients with behavioral, neurophysiologic, and neuroanatomic data from animals to postulate underlying neuronal mechanisms.

OUTCOME

A postulation that two neuronal mechanisms-receptor up-regulation and synapse growth-act sequentially, to explain the gradual appearance of motor recovery after incomplete SCI. These same mechanisms may also act in spinal reflex pathways to mediate hyperreflexia caudal to SCI.

RESULTS

After incomplete SCI, walking ability and hyperreflexia often develop. Initially, cord neurons are hyperpolarized and less excitable because of loss of normal descending facilitation; this is spinal shock. Then, gradually, voluntary movement recovers and hyperreflexia develops. Early (hours to days), these changes develop simultaneously, suggesting a common postsynaptic mechanism-likely, an increase in postsynaptic receptor excitability, possibly receptor up-regulation. Late (weeks to months), recovery and reflex changes occur at a slow rate, are no longer simultaneous, and are long-lasting, which suggests a presynaptic mechanism, such as local synapse growth in spared descending pathways and in reflex pathways. This presumed synapse growth is seemingly enhanced by active use of the growing pathway. Also, developing hyperreflexia appears to limit motor recovery.

CONCLUSIONS

These observations suggest that rehabilitation for incomplete SCI should (1) increase activity in spared descending motor pathways, (2) initially use reflex facilitation or central nervous system stimulants to assist spared descending inputs in depolarizing cord neurons, and (3) later minimize reflex input, when spared descending inputs can depolarize cord neurons without reflex facilitation. Better understanding of neuronal mechanisms that underlie motor recovery after incomplete SCI promises better outcomes from rehabilitation.