The combined effects of clonidine and cyproheptadine with interactive training on the modulation of locomotion in spinal cord injured subjects

Biologic Transplantation and Neurotrophin-Induced Neuroplasticity After Traumatic Brain Injury

OBJECTIVE

In this review, we analyze progress in the treatment of traumatic brain injury with neurotrophins, growth factors and cell and tissue neurotransplantation. The primary objective of these therapies is to reduce neurologic deficits associated with the trauma by inducing neuroplasticity. These therapies are restorative and not necessarily neuroprotective.

MAIN OUTCOME MEASURES

An extensive literature on administration of neurotrophics factors and cell and tissue cerebral transplantation is reviewed. The effects of these therapeutic approaches on brain biochemical, molecular, cellular, and tissue responses are summarized.

CONCLUSION

The cumulative data indicate that cell therapy shows substantial promise in the treatment of neural injury.

Spinal cats on the treadmill: changes in load pathways

Treadmill training and clonidine, an alpha-2 noradrenergic agonist, have been shown to improve locomotion after spinal cord injury. We speculate that transmission in load pathways, which are involved in body support during stance, is specifically modified by training. This was evaluated by comparing two groups of spinal cats; one group (n = 11) was trained to walk until full-weight-bearing (3-4 weeks), and the other (shams; n = 7) was not. During an acute experiment, changes in group I pathways, monosynaptic excitation, disynaptic inhibition, and polysynaptic excitation were investigated by measuring the response amplitude in extensor motoneurons before and after clonidine injection. Monosynaptic excitation was not modified by clonidine but was decreased significantly by training. Disynaptic inhibition was significantly decreased by clonidine in both groups, but more significantly in trained cats, and significantly reduced by training after clonidine. Also, clonidine could reverse group IB inhibition into polysynaptic excitation in both groups but more frequently in trained cats. We also investigated whether fictive stepping revealed additional changes. In trained cats, the phase-dependent modulation of all three responses was similar to patterns reported previously, but in shams, modulation of monosynaptic and polysynaptic responses was not. Overall, training appears to decrease monosynaptic excitation and enhance the effects of clonidine in the reduction of disynaptic inhibition and reversal to polysynaptic excitation. Because it is believed that polysynaptic excitatory group I pathways transmit locomotor drive to extensor motoneurons, we suggest that the latter changes would facilitate the recruitment of extensor muscles for recovering weight-bearing during stepping.

Clonus after human spinal cord injury cannot be attributed solely to recurrent muscle-tendon stretch

Clonus, presented behaviorally as rhythmic distal joint oscillation, is a common pathology that occurs secondary to spinal cord injury (SCI) and other neurological disabilities. There are two predominant theories as to the underlying mechanism of clonus. The prevailing one is that clonus results from recurrent activation of stretch reflexes. An alternative hypothesis is that clonus results from the action of a central oscillator. We present evidence that the mechanism underlying clonus in individuals with SCI is not solely related to muscle stretch. We studied electromyography (EMG) of the soleus (SOL), medial gastrocnemius (MG), tibialis anterior (TA), medial and lateral hamstrings, vastus medialis, vastus lateralis, and rectus femoris from subjects with clinically complete and clinically incomplete SCI during stretch-induced ankle clonus, stepping, and non-weight-bearing standing. Clonic EMG of the SOL, MG, and TA occurred synchronously and were not consistently related to muscle-tendon stretch in any of the conditions studied. Further, EMG activity during stretch-induced ankle clonus, stepping, and non-weight-bearing standing had similar burst frequency, burst duration, silent period duration, and coactivation among muscles, indicating that clonic EMG patterns occurred over a wide range of kinematic and kinetic conditions, and thus proprioceptive inputs. These results suggest that the repetitive clonic bursts could not be attributable solely to immediate afferent feedback such as recurrent muscle stretch. However, these results support the theory that the interaction of central mechanisms and peripheral events may be responsible for clonus.

The effect of noradrenergic drugs on the recovery of walking after spinal cord injury

Clonidine, a noradrenergic agonist has been associated with improved walking in both spinal cat and spinal cord injured (SCI) subjects.

OBJECTIVES

The objective of this brief review is to compare the effects of clonidine on walking capabilities in SCI subjects with functionally complete and incomplete spinal cord injuries.

STUDY DESIGN/METHODS

Both oral administration and intrathecal injection of clonidine were investigated. A motorized treadmill was used and harness support provided in most of the SCI subjects as no walking capabilities could be observed overground. A single subject design was used in these chronic SCI subjects.

SETTING

Canada and France.

RESULTS

In complete SCI subjects while receiving clonidine, none of the subjects was able to initiate independent stepping. In contrast, the greatest effects were found in SCI subjects with injuries that are incomplete but still severely disabling while minimal effects could be observed in the more functional SCI subjects. These effects on walking are observed in measures of walking speed, and electromyographic and kinematic patterns. Regardless of effects on walking, however, a consistent decrease of the flexor reflex amplitude could be observed in all SCI subjects independent of the severity of the lesion.

CONCLUSION

This review demonstrated that clonidine could be a powerful anti-spasmodic drug in addition to improving locomotion in a limited number of SCI subjects. The mechanism, significance and implications of these results will be discussed.

A review of the adaptability and recovery of locomotion after spinal cord injury

Spinal cord injury (SCI) is associated with multiple motor problems leading to the alteration and limited adaptation in the walking and postural behavior. This review addresses recent findings on locomotor and postural adaptations after spinal cord injury. The adaptation of the locomotor behavior to behavioral goals and external constraints constitute important functional prerequisites in the recovery of locomotion after spinal cord injury. Functional prerequisites in locomotion include coping with changes in speed, slope obstacle, weight support, interaction with walking aids, energy consumption and attentional demands. Various treatment approaches such as locomotor training using body weight support (BWS) and functional electrical stimulation (FES) will be discussed, in the context of functional prerequisites necessary in the recovery of locomotion. Understanding locomotor and postural adaptations will lead to a better appreciation of the normal and dysfunctional mechanisms, and culminate eventually in the development of appropriate rehabilitation assessment and treatment strategies.

Using robotics to teach the spinal cord to walk

We have developed a robotic device (e.g. the rat stepper) that can be used to impose programmed forces on the hindlimbs of rats during stepping. In the present paper we describe initial experiments using this robotic device to determine the feasibility of robotically assisted locomotor training in complete spinally transected adult rats. The present results show that using the robots to increase the amount of load during stance by applying a downward force on the ankle improved lift during swing. The trajectory pattern during swing was also improved when the robot arms were programmed to move the ankle in a path that approximated the normal swing trajectory. These results suggest that critical elements for successful training of hindlimb stepping in spinal cord injured rats can be implemented rigorously and evaluated using the rat stepper.

The role of rehabilitation in the recovery of walking in the neurological population

Recent studies demonstrate that neurological patients show great potential for recovery in both the early and late stages following injury. Enhancement of the recovery process could be achieved with new rehabilitation approaches alone or in combination with pharmacological intervention. These new approaches have evolved from fundamental advances in both animal and human studies. To date few randomized clinical trials have addressed the efficacy or effectiveness of these new approaches. In this paper, important quantitative studies will be reviewed and discussed in relation to the important mechanisms of locomotor control and plasticity that take place following lesions of the central nervous system.

Neural plasticity after human spinal cord injury: application of locomotor training to the rehabilitation of walking

Recovery of locomotion has been considered unattainable following a clinically complete or severe incomplete spinal cord injury even after conventional therapy. However, the locomotion of spinal animals can be improved by training that provides complex temporal patterns of sensory information related to stepping that is interpreted by the spinal cord. This review discusses the evidence that suggests human spinal networks can integrate and interpret complex sensory signals to produce functional efferent output and adapt to repetitive training. Locomotor training, a new rehabilitative approach, is based on principles that promote the movement of limbs and trunk to generate sensory information consistent with locomotion to improve the potential for the recovery of walking after neurologic injury.

Combined use of body weight support, functional electric stimulation, and treadmill training to improve walking ability in individuals with chronic incomplete spinal cord injury

OBJECTIVE

To assess the effect of an intervention combining body weight support (BWS), functional electric stimulation (FES), and treadmill training on overground walking speed (OGWS), treadmill walking speed, speed and distance, and lower extremity motor scores (LEMS).

DESIGN

Before and after comparison.

SETTING

Miami Project to Cure Paralysis.

PARTICIPANTS

Nineteen subjects with American Spinal Injury Association class C injury who were at least 1 year postinjury and had asymmetrical lower extremity function.

INTERVENTION

Subjects trained 1.5 hours per day, 3 days per week, for 3 months. The training consisted of body weight-supported treadmill walking assisted by electric stimulation. Stimulation was applied to common peroneal nerve of the weaker lower extremity (LE) and timed to assist with the swing phase of the step cycle.

MAIN OUTCOME MEASURES

OGWS in the absence of both BWS and FES; LEMS, and treadmill training parameters of speed and distance.

RESULTS

Over the course of training, there was a significant increase in OGWS (from.12 +/- 0.8m/s to .21 +/- .15m/s, p = .0008), treadmill walking speed (from .23 +/- .12m/s to.49 +/- .20m/s, p = .00003), and treadmill walking distance (from 93 +/- 84m to 243 +/- 139m, p = .000001). The median LEMS increased significantly for both the stimulated and nonstimulated leg (from 8 to 11 in the FES-assisted leg, from 15 to 18 in the nonassisted leg, p < .005 for each).

CONCLUSIONS

All subjects showed improvement in OGWS and overall LE strength. Further research is required to delineate the essential elements of these particular training strategies.

Spinal interneurons that receive input from muscle afferents are differentially modulated by dorsolateral descending systems

The possibility that descending systems have differential actions on the spinal interneurons that receive input from muscle afferents was investigated. Prolonged, physiological inputs were generated by stretch of the triceps surae muscles. The resulting firing patterns of 25 lumbosacral interneurons were recorded before and during a reversible cold block of the dorsolateral white matter at the thoracic level in nonparalyzed, decerebrate preparations. The strength of group I muscle afferent input was assessed from the response to sinusoidal tendon vibration, which activated muscle spindle Ia afferents directly and tendon organ Ib afferents via the resulting reflex force. The stretch-evoked responses of interneurons with strong responses to vibration were markedly suppressed by dorsal cold block, whereas the stretch-evoked responses of interneurons with weak vibration input were enhanced. The cells most strongly activated by vibration received their primary input from Ia afferents and all of these cells were inhibited by the cold block. These results suggest that a disruption of the descending system, such as occurs in spinal cord injury, will lead to a suppression of the interneuronal pathways with group Ia input while enhancing excitability within interneuronal pathways transmitting actions from higher threshold afferents. One possible consequence of this suppression would be a decreased activity among the Ia inhibitory interneurons that mediate reciprocal inhibition, resulting in abnormal reciprocal relations between antagonists and promoting anomalous muscle cocontraction.

The role of serotonin in reflex modulation and locomotor rhythm production in the mammalian spinal cord

Over the past 40 years, much has been learned about the role of serotonin in spinal cord reflex modulation and locomotor pattern generation. This review presents an historical overview and current perspective of this literature. The primary focus is on the mammalian nervous system. However, where relevant, major insights provided by lower vertebrate models are presented. Recent studies suggest that serotonin-sensitive locomotor network components are distributed throughout the spinal cord and the supralumbar regions are of particular importance. In addition, different serotonin receptor subtypes appear to have different rostrocaudal distributions within the locomotor network. It is speculated that serotonin may influence pattern generation at the cellular level through modulation of plateau properties, an interplay with N-methyl-D-aspartate receptor actions, and afterhyperpolarization regulation. This review also summarizes the origin and maturation of bulbospinal serotonergic projections, serotonin receptor distribution in the spinal cord, the complex actions of serotonin on segmental neurons and reflex pathways, the potential role of serotonergic systems in promoting spinal cord maturation, and evidence suggesting serotonin may influence functional recovery after spinal cord injury.

Pharmacological interventions for spasticity following spinal cord injury

BACKGROUND

Spasticity is a major health problem for patients with a spinal cord injury (SCI) that limits patients' mobility and affects independence in activities of daily living and work. Spasticity may also cause pain, loss of range of motion, contractures, sleep disorders and impair ambulation in patients with an incomplete lesion. The effectiveness of available drugs is still uncertain and they may cause adverse effects. Assessing what works in this area is complicated by the lack of valid and reliable measurement tools. The aim of this systematic review is to critically appraise and summarise existing information of the effectiveness of available treatments and to identify areas where further research is needed.

OBJECTIVES

To assess the effectiveness and safety of Baclofen, Dantrolene, Tizanidine and any other drugs for the treatment of long term spasticity in SCI patients as well as the effectiveness and safety of different routes of administration of Baclofen.

SEARCH STRATEGY

We searched the Injuries Group specialised register, the Cochrane Controlled Trials Register, MEDLINE, EMBASE and CINHALH up to 1998. Drug companies and experts active in the area were also contacted.

SELECTION CRITERIA

All parallel and crossover RCTs including spinal cord injury patients complaining of "severe spasticity". Studies where less than 50% of patients had a spinal cord injury were excluded.

DATA COLLECTION AND ANALYSIS

Methodological quality of studies (allocation concealment, blinding, patients characteristics, inclusion and exclusion criteria; interventions; outcomes; lost to follow up) was independently assessed by two investigators. The heterogeneity among studies did not allow quantitative combination of results.

MAIN RESULTS

Nine out of 53 studies met the inclusion criteria. Study design was: 8 cross over, 1 parallel-group trial. Two studies (14 SCI patients), showed a significant effect of intrathecal baclofen in reducing spasticity (Ashworth Score and ADL performances), compared to placebo, without any side effect. The study comparing tizanidine to placebo (118 SCI patients) showed a significant effect of tizanidine in improving Ashworth Score but not in ADL performances. Tizanidine group reported significant rates of adverse effects (drowsiness, xerostomia). For the other drugs (Gabapentine, Clonidine, Diazepam, Amytal and oral Baclofen ) the results do not provide evidence for a clinical significant effectiveness.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to assist clinicians in a rational approach to antispastic treatment for SCI. Further research is urgently needed to improve the scientific basis of patient care.

Tapping into spinal circuits to restore motor function

Motivated by the challenge of improving neuroprosthetic devices, the authors review current knowledge relating to harnessing the potential of spinal neural circuits, such as reflexes and pattern generators. If such spinal interneuronal circuits could be activated, they could provide the coordinated control of many muscles that is so complex to implement with a device that aims to address each participating muscle individually. The authors' goal is to identify candidate spinal circuits and areas of research that might open opportunities to effect control of human limbs through electrical activation of such circuits. David McCrea's discussion of the ways in which hindlimb reflexes in the cat modify motor activity may help in developing optimal strategies for functional neuromuscular stimulation (FNS), by using knowledge of how reflex actions can adapt to different conditions. Michael O'Donovan's discussion of the development of rhythmogenic networks in the chick embryo may provide clues to methods of generating rhythmic activity in the adult spinal cord. Serge Rossignol examines the spinal pattern generator for locomotion in cats, its trigger mechanisms, modulation and adaptation, and suggests how this knowledge can help guide therapeutic approaches in humans. Hugues Barbeau applies the work of Rossignol and others to locomotor training in human subjects who have suffered spinal cord injury (SCI) with incomplete motor function loss (IMFL). Michel Lemay and Warren Grill discuss some of the technical challenges that must be addressed by engineers to implement a neuroprosthesis using electrical stimulation of the spinal cord, particularly the control issues that would have to be resolved.

A novel method for locomotion training

This article describes a novel therapeutic system for locomotion training and learning for patients with a wide range of neurological and musculoskeletal disorders. The technique embraces the notion that locomotion therapy should be goal oriented and task specific. The task specificity includes a partial weight-bearing device that permits the posture/equilibrium, movement, and weight-bearing components of gait function to operate concurrently, even in patients with serious deficits. In addition, it allows interaction with therapists and others to facilitate locomotion control, particularly during the early stages of gait therapy. Neurobiological bases for this technique and early clinical results are discussed, and two case studies of patients with traumatic brain injury (TBI) are presented. Although well-designed efficacy studies are needed, clearly this therapeutic approach to locomotor disorders among TBI patients meets the various criteria for recovery of gait function established in this article.

Walking after spinal cord injury: evaluation, treatment, and functional recovery

OBJECTIVE

To present some recent developments and concepts emerging from both animal and human studies aimed at enhancing recovery of walking after spinal cord injury (SCI).

DATA SOURCES

Researchers in the field of restoration of walking after SCI, as well as references extracted from searches in the Medline computerized database.

STUDY SELECTION

Studies that reported outcome measures of walking for spinal cord injured persons with an incomplete motor function loss or cats with either a complete or incomplete spinal section.

DATA EXTRACTION

Data were extracted and validity was assessed by the authors.

DATA SYNTHESIS

This review shows that a multitude of interventions--mechanical, electrical, or pharmacologic--can increase the walking abilities of persons with SCI who have incomplete motor function loss.

CONCLUSIONS

A comprehensive evaluation of walking behavior requires tasks involving the different control variables. This comprehensive evaluation can be used to characterize the process of recovery of walking as well as the effectiveness of various treatments.

Does neurorehabilitation play a role in the recovery of walking in neurological populations?

This review demonstrates that neurorehabilitation approaches, based on recent neuroscience findings, can enhance locomotor recovery after a spinal cord injury or stroke. Findings are presented from more than 20 clinical studies conducted by numerous research groups on the effect of locomotor training using either body weight support (BWS), functional electrical stimulation (FES), pharmacological approaches or a combination of them. Among the approaches, only BWS-assisted locomotor training has been demonstrated to have a greater effect than conventional or locomotor training alone. However, when study results were combined and weighted for the number of subjects, the results indicated that there is a gradient of effects from small changes with the immediate application of FES or BWS to larger changes when locomotor training is combined with FES or BWS or pharmacological approaches. The findings of these studies suggest that these neurorehabilitation approaches do play a role in the recovery of walking in subjects with spinal cord injury or stroke. Several factors contribute to the potential for recovery including the site, etiology, and chronicity of the injury, as well as the type, duration, and specificity of the intervention and whether interventions are combined. Furthermore, how these neurorehabilitation approaches may take advantage of the plasticity process following neurological lesion is also discussed.

Effects of intrathecal alpha1- and alpha2-noradrenergic agonists and norepinephrine on locomotion in chronic spinal cats

Noradrenergic drugs, acting on alpha adrenoceptors, have been found to play an important role in the initiation and modulation of locomotor pattern in adult cats after spinal cord transection. There are at least two subtypes of alpha adrenoceptors, alpha1 and alpha2 adrenoceptors. The aim of this study was to investigate the effects of selective alpha1 and alpha2 agonists in the initiation and modulation of locomotion in adult chronic cats in the early and late stages after complete transection at T13. Five cats, chronically implanted with an intrathecal cannula and electromyographic (EMG) electrodes were used in this study. Noradrenergic drugs including alpha2 agonists (clonidine, tizanidine, and oxymetazoline) and an antagonist, yohimbine, one alpha1 agonist (methoxamine), and a blocker, prazosin, as well as norepinephrine were injected intrathecally. EMG activity synchronized to video images of the hindlimbs were recorded before and after each drug injection. The results show differential effects of alpha1 and alpha2 agonists in the initiation of locomotion in early spinal cats (i.e., in the first week or so when there is no spontaneous locomotion) and in the modulation of locomotion and cutaneous reflexes in the late-spinal cats (i.e., when cats have recovered spontaneous locomotion). In early spinal cats, all three alpha2 agonists were found to initiate locomotion, although their action had a different time course. The alpha1 agonist methoxamine induced bouts of nice locomotor activity in three spinal cats some hours after injection but only induced sustained locomotion in one cat in which the effects were blocked by the alpha1 antagonist prazosin. In late spinal cats, although alpha2 agonists markedly increased the cycle duration and flexor muscle burst duration and decreased the weight support or extensor activity (effects blocked by an alpha2 antagonist, yohimbine), alpha1 agonist increased the weight support and primarily the extensor activity of the hindlimbs without markedly changing the timing of the step cycle. Although alpha2 agonists, especially clonidine, markedly reduced the cutaneous excitability and augmented the foot drag, the alpha1 agonist was found to increase the cutaneous reflex excitability. This is in line with previously reported differential effects of activation of the two receptors on motoneuron excitability and reflex transmission. Noradrenaline, the neurotransmitter itself, increased the cycle duration and at the same time retained the cutaneous excitability, thus exerting both alpha1 and alpha2 effects. This work therefore suggests that different subclasses of noradrenergic drugs could be used to more specifically target aspects of locomotor deficits in patients after spinal injury or diseases.

A new approach to retrain gait in stroke patients through body weight support and treadmill stimulation

BACKGROUND AND PURPOSE

A new gait training strategy for patients with stroke proposes to support a percentage of the patient's body weight while retraining gait on a treadmill. This research project intended to compare the effects of gait training with body weight support (BWS) and with no body weight support (no-BWS) on clinical outcome measures for patients with stroke.

METHODS

One hundred subjects with stroke were randomized to receive one of two treatments while walking on a treadmill: 50 subjects were trained to walk with up to 40% of their body weight supported by a BWS system with overhead harness (BWS group), and the other 50 subjects were trained to walk bearing full weight on their lower extremities (no-BWS group). Treatment outcomes were assessed on the basis of functional balance, motor recovery, overground walking speed, and overground walking endurance.

RESULTS

After a 6-week training period, the BWS group scored significantly higher than the no-BWS group for functional balance (P = 0.001), motor recovery (P = 0.001), overground walking speed (P = 0.029), and overground w alking endurance (P = 0.018). The follow-up evaluation, 3 months after training, revealed that the BWS group continues to have significantly higher scores for overground walking speed (P = 0.006) and motor recovery (P = 0.039).

CONCLUSIONS

Retraining gait in patients with stroke while a percentage of their body weight was supported resulted in better walking abilities than gait training while the patients were bearing their full weight. This novel gait training strategy provides a dynamic and integrative approach for the treatment of gait dysfunction after stroke.

Locomotor capacity and recovery of spinal cord function in paraplegic patients: a clinical and electrophysiological evaluation

Recent studies have shown that a locomotor pattern can be induced and trained into paraplegic patients under conditions of body unloading using a moving treadmill. The present study investigated the behaviour of the locomotor pattern and also the relationship of its development to the spontaneous recovery of spinal cord function assessed by clinical and electrophysiological (tibial nerve somatosensory evoked potentials and motor evoked potentials) examinations. The earliest time that spinal locomotor activity could be induced was when signs of spinal shock had disappeared. This activity was distinct from spinal stretch reflex activity. In complete and incomplete paraplegic patients an increase of gastrocnemius electromyographic activity occurred during the stance phase of a step cycle with daily locomotor training over the whole training period of 12 weeks. This was coincident with a significant decrease in body unloading. In contrast to this, neither clinical nor electrophysiological examination scores improved after the onset of training in both patient groups. Only in incomplete paraplegic patients was there an insignificant increase in sensory and motor scores obtained in the neurological examination during the time period before onset of training. An improvement of locomotor function by training was also seen in patients with paraplegia due to a cauda lesion. Therefore, in patients with a spinal cord lesion training effects on muscles and tendons are present in addition to those on the spinal locomotor centres. The findings of this study may be relevant for future clinical treatment of paraplegic patients.

Early locomotor training with clonidine in spinal cats

Clonidine, a noradrenergic alpha-2 agonist, can initiate locomotion early after spinalization in cats. Because this effect lasts 4-6 h, we have injected clonidine daily, intraperitoneally or intrathecally, and intensively trained five spinal cats to perform hindlimb walking on a treadmill starting at day 3 and continuing until 10 days posttransection. Each day, clonidine was injected to induce locomotor activity and cats were trained to walk with as much weight support as possible and at different speeds during multiple (1-5) locomotor training sessions, each lasting from 10 to 20 min, until the effects of clonidine wore off. Electromyographic (EMG) activity synchronized to video images of the hindlimbs were recorded before and after each clonidine injection. The results showed, first, a day-to-day change of the locomotor pattern induced by clonidine from the 3rd to the 11th day including an increase in the duration of the step cycle, an increase in the duration of extensor EMG activity, and an increase in total angular excursion of the hip, knee, and ankle joints. Second, after 6-11 days of this regimen, there was an emergence of a coordinated locomotor pattern with weight support of the hindquarters that was visible even before that day's clonidine injection. The results suggested that daily injection of clonidine followed by early and daily interactive locomotor training can enhance the recovery of locomotion in spinal cats.

Gait analysis of spinal cord injured subjects: effects of injury level and spasticity

OBJECTIVE

To identify abnormalities in the gait of spinal cord injured (SCI) subjects, particularly in relation to injury level and spasticity.

DESIGN

Case-control study comparing the gait of SCI individuals with matched controls. Video-motion analysis was used to collect data on temporal and kinematic variables. Spasticity was assessed using the Ashworth score and pendulum test. Data regarding age, height, weight, mechanism, and level of injury were also collected.

SETTING

Spinal cord injury clinic of a tertiary care hospital.

PARTICIPANTS

Twenty-seven SCI individuals volunteered to participate in the study. All had retained walking ability (Frankel D) and could ambulate independently for a minimum of 10m with or without walking aids. Individuals with cauda equina injuries were excluded from the study. Age, gender, etiology of injury, and interval since injury were not used as exclusion criteria. Ten age-, sex-, and anthropomorphically matched controls were also recruited.

RESULTS

Subjects with thoracic injures demonstrated reduced cadence, forward velocity, and knee angular velocity, whereas lumbar injuries resulted in reduced stride length and ankle velocities. These differences were statistically significant (p < .05). Gait in individuals with cervical injuries was not significantly different.

CONCLUSIONS

Kinematic gait analysis is a sensitive means of quantifying gait abnormalities. Spasticity and injury level determine the pattern of abnormality in gait after spinal cord injury.

A treadmill apparatus and harness support for evaluation and rehabilitation of gait

This report describes a treadmill apparatus for the evaluation and rehabilitation of gait in disabled persons. The apparatus incorporates a body weight support system as well as mechanisms to change certain conditions: treadmill belt speed, upward-downward and lateral slopes, and provision of obstacles. The apparatus enables elements of a treadmill walking pattern to be visible in persons for whom gait evaluation or rehabilitation may not otherwise be possible. It also allows for exploration of factors that limit the adaptability of gait in person after disease or injury by changing the mechanical demand of the locomotor task.

Pharmacology of locomotion: an account of studies in spinal cats and spinal cord injured subjects

This paper summarizes a research approach which started with experiments in cats and eventually led to the successful use of drugs in spinal cord injured (SCI) patients to improve their walking. In such a short paper, it is impossible to cover the details of this approach but we will establish important landmarks and give a bibliography to guide further reading.

Fetal cell grafts into resection and contusion/compression injuries of the rat and cat spinal cord

This article reviews recent findings concerning the feasibility, basic neurobiology, and potential functional benefits of fetal CNS tissue grafts into acute and chronic lesions of the adult spinal cord. In the rat, neuro-anatomical observations suggest that transplants into resection cavities establish neuritic projections that could functionally reunite separated rostral and caudal segments of the host spinal cord. Furthermore, some complementary electrophysiological evidence has been obtained for synaptic connectivity between host and graft neurons. In these studies, extracellular single-unit activity was evoked in fetal spinal cord (FSC) transplants by stimulating host dorsal roots that had been juxtaposed to donor tissue at the time of transplantation. In other investigations, we examined whether grafts could also establish axonal projections to appropriate areas of gray matter in the chronically injured spinal cord. For this purpose, fetal serotoninergic (5-HT) neurons were injected caudal to complete spinal cord transections that had been made 1-3 months earlier. Immunocytochemistry revealed that these cells projected their axons into gray matter regions normally innervated by bulbospinal 5-HT neurons. To investigate transplantation in a more clinically relevant lesion model, a third group of experiments involved injection of dissociated cell suspensions into acute [less than 24 h postinjury (p.i.)]), subchronic (7-10 days p.i), and chronic (greater than or equal to one month, p.i.) contusion lesions. Such grafts routinely filled areas that otherwise would have been regions of cavitation extending rostral-caudal distances of approximately 7 mm. FSC transplants in such injuries also appeared to influence some aspects of motoneuron excitability and hindlimb locomotion. More recent studies of the cat spinal cord have extended these findings in the rat by showing long-term survival (greater than 2 years) of fetal CNS allografts in recipients with either subtotal transection or compression lesions. Preliminary studies of connectivity have also shown host-graft projection patterns similar to those seen in the rat. Behavioral analyses are currently underway to examine the effects of fetal grafts in cats with chronic postcompression lesions. These observations in the rat and cat are discussed in the general context of basic biological and clinical issues relevant to the long-term objective of promoting functional improvement in the damaged spinal cord.

H-reflex modulation during walking in spastic paretic subjects

Hoffman (H) reflexes were elicited from the soleus muscle during treadmill walking in 21 spastic paretic patients. The soleus and tibialis anterior muscles were reciprocally activated during walking in most patients, much like that observed in healthy individuals. The pattern of H-reflex modulation varied considerably between patients, from being relatively normal in some patients to a complete absence of modulation in others. The most common pattern observed was a lack of H-reflex modulation through the stance phase and slight depression of the reflex in the swing phase, considerably less modulation than that of normal subjects under comparable walking conditions. The high reflex amplitudes during periods of the step cycle such as early stance seems to be related to the stretch-induced large electromyogram bursts in the soleus in some subjects. The abnormally active reflexes appear to contribute to the clonus encountered during walking in these patients. In three patients who were able to walk for extended periods, the effect of stimulus intensity was examined. Two of these patients showed a greater degree of reflex modulation at lower stimulus intensities, suggesting that the lack of modulation observed at higher stimulus intensities is a result of saturation of the reflex loop. In six other patients, however, no reflex modulation could be demonstrated even at very low stimulus intensities.

A physiological basis for the development of rehabilitative strategies for spinally injured patients

After a decade of studies using animal models, there is sufficient information to encourage a reassessment of the potential for recovery of motor function following spinal cord injury in humans. This review focuses on the response of the lumbosacral motor system following spinal cord injury and the effects of rehabilitative strategies such as weight support, loading, and administration of specific pharmacological agonists and antagonists on the maintenance and/or recovery of motor function. Based on clinical experience and review of related studies, the authors suggest a list of eight strategies for the improvement of rehabilitative protocols.