Spinal shock revisited: a four-phase model

Reprint of "Drawing breath without the command of effectors: the control of respiration following spinal cord injury"

The maintenance of blood gas and pH homeostasis is essential to life. As such breathing, and the mechanisms which control ventilation, must be tightly regulated yet highly plastic and dynamic. However, injury to the spinal cord prevents the medullary areas which control respiration from connecting to respiratory effectors and feedback mechanisms below the level of the lesion. This trauma typically leads to severe and permanent functional deficits in the respiratory motor system. However, endogenous mechanisms of plasticity occur following spinal cord injury to facilitate respiration and help recover pulmonary ventilation. These mechanisms include the activation of spared or latent pathways, endogenous sprouting or synaptogenesis, and the possible formation of new respiratory control centres. Acting in combination, these processes provide a means to facilitate respiratory support following spinal cord trauma. However, they are by no means sufficient to return pulmonary function to pre-injury levels. A major challenge in the study of spinal cord injury is to understand and enhance the systems of endogenous plasticity which arise to facilitate respiration to mediate effective treatments for pulmonary dysfunction.

Effects of bladder function by early tamsulosin treatment in a spinal cord injury rat model

Objective

To investigate the effects of early tamsulosin treatment on changes in bladder characteristics after a spinal cord injury.

Methods

We divided 45 rats into three groups: the control (CON) group, the spinal cord injury (SCI) group, and the SCI+tamsulosin treatment (SCI+TAM) group. Spinal cord transection was performed in the SCI and SCI+TAM groups. Tamsulosin was injected for 7 days in the SCI+TAM group. Intravesical and intra-abdominal catheters were implanted before cord injury. Basal pressure (BP), maximal vesical pressure (MVP), micturition volume (MV), and voiding interval time (VIT) were measured at 7 days after SCI. The bladder was then removed and used for an in vitro organ bath study and Western blot analysis. The percentage changes in contractility from baseline after acetylcholine alone, pretreatment with a muscarinic 2 (M2) receptor blocker (AQ-RA741), and pretreatment with a M3 receptor blocker (4-DAMP) were compared among the groups. Western blot analyses were performed to determine expression levels of pERK1/2 and rho-kinase.

Results

In cystometry, MVP, BP, MV, and VIT showed changes in the SCI and SCI+TAM groups versus the CON group (p<0.05). In the organ bath study, acetylcholine-induced contractility in the three groups differed significantly (p<0.05). Additionally, acetylcholine-induced contractility with 4-DAMP pretreatment was reduced significantly in the SCI+TAM group versus the SCI group. In Western blotting, pERK1/2 expression was stronger (p<0.05) and rho-kinase expression was weaker in the SCI+TAM group than the SCI group (p<0.05).

Conclusion

These results suggest that the bladder contraction due to acetylcholine after SCI can be decreased by tamsulosin in the acute stage and this involves changes in pERK1/2 and rho-kinase.

Injection of WGA-Alexa 488 into the ipsilateral hemidiaphragm of acutely and chronically C2 hemisected rats reveals activity-dependent synaptic plasticity in the respiratory motor pathways

WGA-Alexa 488 is a fluorescent neuronal tracer that demonstrates transsynaptic transport in the central nervous system. The transsynaptic transport occurs over physiologically active synaptic connections rather than less active or silent connections. Immediately following C2 spinal cord hemisection (C2Hx), when WGA-Alexa 488 is injected into the ipsilateral hemidiaphragm, the tracer diffuses across the midline of the diaphragm and retrogradely labels the phrenic nuclei (PN) bilaterally in the spinal cord. Subsequently, the tracer is transsynaptically transported bilaterally to the rostral Ventral Respiratory Groups (rVRGs) in the medulla over physiologically active connections. No other neurons are labeled in the acute C2Hx model at the level of the phrenic nuclei or in the medulla. However, with a recovery period of at least 7weeks (chronic C2Hx), the pattern of WGA-Alexa 488 labeling is notably changed. In addition to the bilateral PN and rVRG labeling, the chronic C2Hx model reveals fluorescence in the ipsilateral ventral and dorsal spinocerebellar tracts, and the ipsilateral reticulospinal tract. Furthermore, interneurons are labeled bilaterally in laminae VII and VIII of the spinal cord as well as neurons in the motor nuclei bilaterally of the intercostal and forelimb muscles. Moreover, in the chronic C2Hx model, there is bilateral labeling of additional medullary centers including raphe, hypoglossal, spinal trigeminal, parvicellular reticular, gigantocellular reticular, and intermediate reticular nuclei. The selective WGA-Alexa 488 labeling of additional locations in the chronic C2Hx model is presumably due to a hyperactive state of the synaptic pathways and nuclei previously shown to connect with the respiratory centers in a non-injured model. The present study suggests that hyperactivity not only occurs in neuronal centers and pathways caudal to spinal cord injury, but in supraspinal centers as well. The significance of such injury-induced plasticity is that hyperactivity may be a mechanism to re-establish lost function by compensatory routes which were initially physiologically inactive.

Neurogenic lower urinary tract dysfunction: how, when, and with which patients do we use urodynamics?

Neurogenic lower urinary tract dysfunction (NLUTD) affects many patients and requires close monitoring. Initial studies establishing patients at risk for upper tract disease revealed that high detrusor leak point pressures were predictive of upper tract disease. Urodynamics in patients with NLUTD have specific challenges. Initial studies in patients after an acute injury should be delayed until after the spinal shock phase. In children with spinal dysraphism, studies should be done early to established potential risk. The goals are maintaining low bladder pressures, decreasing risk of infection, and maintaining continence.

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

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

Local cooling for traumatic spinal cord injury: outcomes in 20 patients and review of the literature

OBJECT

In this prospective study, the authors offered protocol-selected patients a combination of parenteral steroids, decompression surgery, and localized cooling to preserve viable spinal cord tissue and enhance functional recovery.

METHODS

After acquiring informed consent, the authors offered this regimen with localized deep cord cooling (dural temperature 6°C) to 20 patients with a neurologically complete spinal cord injury to begin within 8 hours of injury. After decompression, the cord was locally cooled through the intact dura using a suspended extradural saddle at the site of injury for up to 4 hours, during which time spinal fusion was performed. Sensation and motor function were evaluated directly after the injury and again over a year later. The patients were evaluated using the 2011 amendment to the American Spinal Injury Association (ASIA) Impairment Scale.

RESULTS

Eighty percent of the 20 patients (12 with cervical and 4 thoracic injuries) with an initial neurologically complete cord injury had some recovery of sensory or motor function. All patients initially had ASIA Grade A impairment. Of 14 patients with quadriplegia, 5 remained ASIA Grade A, 5 improved to ASIA Grade B, 3 to ASIA Grade C, and 1 to ASIA Grade D. The remaining 6 patients had suffered a thoracic spinal cord injury, and of these 2 remained ASIA Grade A, 1 recovered to ASIA Grade B, 2 to ASIA Grade C, and 1 ASIA Grade D. All considered, of 20 patients, 35% remained ASIA Grade A, 30% improved to ASIA Grade B, and 25% to ASIA Grade C. Impairment in 2 (10%) of 20 patients improved to ASIA Grade D. The mean improvement in neurological level of injury in all patients was 1.05, the mean improvement in motor level was 1.7, and the mean improvement in sensory level was 2.8. Two patients recovered the ability to walk, 2 could extend their legs, 5 could sense bladder fullness, and 3 had partial ability to void voluntarily. Four males recovered subnormal ability to have voluntary erection sufficient for limited sexual activity.

CONCLUSIONS

The authors present here results of 20 patients with neurologically complete spinal cord injury treated with a combination of surgical decompression, glucocorticoid administration, and regional hypothermia. These patients experienced a better recovery than might have been expected had traditional forms of treatment been used. The benefit of steroid treatment for cord injury has been debated in the last decade, but the authors feel that research into the effects of cord cooling should be expanded. Given that the optimal neuroprotective temperature after acute trauma has not yet been defined, and may well be below that which is considered safely approachable through systemic cooling, methods that allow for the early attainment of such a temperature locally should be further explored. The results are encouraging enough to suggest the undertaking of controlled clinical trials of treatment using localized spinal cord cooling, where such treatment can be instituted within hours following injury.

Effects of reversible spinalization on individual spinal neurons

Postural limb reflexes (PLRs) represent a substantial component of the postural system responsible for stabilization of dorsal-side-up trunk orientation in quadrupeds. Spinalization causes spinal shock, that is a dramatic reduction of extensor tone and spinal reflexes, including PLRs. The goal of our study was to determine changes in activity of spinal interneurons, in particular those mediating PLRs, that is caused by spinalization. For this purpose, in decerebrate rabbits, activity of individual interneurons from L5 was recorded during stimulation causing PLRs under two conditions: (1) when neurons received supraspinal influences and (2) when these influences were temporarily abolished by a cold block of spike propagation in spinal pathways at T12 ("reversible spinalization"; RS). The effect of RS, that is a dramatic reduction of PLRs, was similar to the effect of surgical spinalization. In the examined population of interneurons (n = 199), activity of 84% of them correlated with PLRs, suggesting that they contribute to PLR generation. RS affected differently individual neurons: the mean frequency decreased in 67% of neurons, increased in 15%, and did not change in 18%. Neurons with different RS effects were differently distributed across the spinal cord: 80% of inactivated neurons were located in the intermediate area and ventral horn, whereas 50% of nonaffected neurons were located in the dorsal horn. We found a group of neurons that were coactivated with extensors during PLRs before RS and exhibited a dramatic (>80%) decrease in their activity during RS. We suggest that these neurons are responsible for reduction of extensor tone and postural reflexes during spinal shock.

Care related and transit neuronal injuries after cervical spine trauma: state of care and practice in Nigeria

Suboptimal care during extraction and transfer after spinal trauma predisposes patients to additional spinal cord injury. This study examines the factors that contribute to care related and transit injuries and suggests steps to improve standard of care in spinal trauma patients in Nigeria. It is a questionnaire-based prospective study of patients admitted with cervical cord injury to two neurosurgical centers in Enugu, Nigeria, between March 2008 and October 2010. Demography, mechanism of injury, mode of extraction from the scene and transportation to first visited hospital, precautions taken during transportation, and treatment received before arriving at the neurosurgical unit were analyzed. There were 53 (77.9%) males, the mean age was 33.9 years, and 23.5% had concomitant head injury. Average delay was 3.5 h between trauma and presentation to initial care and 10.4 days before presentation to definitive care. Only 26.5% presented primarily to tertiary centers with trauma services. About 94.1% were extracted by passersby. None of the patients received cervical spine protection either during extrication or in the course of transportation to initial care, and 35.3% were sitting in a motor vehicle or supported on a motorbike during transport. Of the 43 patients transported lying down, 41.9% were in the back seat of a sedan, and only 11.8% were transported in an ambulance. Neurological dysfunction was first noticed after removal from the scene by 41.2% of patients, while 7.4% noticed it on the way to or during initial care. During subsequent transfer to definitive centers, only 36% had cervical support, although 78% were transported in ambulances. Ignorance of pre-hospital management of cervically injured patients exists in the general population and even among medical personnel and results in preventable injuries. There is need for urgent training, provision of paramedical services, and public enlightenment.

Spasticity

Antispastic medications that are directed to reduce clinical signs of spasticity, such as exaggerated reflexes and muscle tone, do not improve the movement disorder. Medication can even increase weakness which might interfere with functional movements, such as walking. In this chapter we address how spasticity affects mobility and how this should be taken into account in the treatment of spasticity. In clinical practice, signs of exaggerated tendon tap reflexes associated with muscle hypertonia are the consequence of spinal cord injury (SCI). They are generally thought to be responsible for spastic movement disorders. Most antispastic treatments are, therefore, directed at the reduction of reflex activity. In recent years, a discrepancy between spasticity as measured in the clinic and functional spastic movement disorder was noticed, which is primarily due to the different roles of reflexes in passive and active states, respectively. We now know that central motor lesions are associated with loss of supraspinal drive and defective use of afferent input with impaired behavior of short-latency and long-latency reflexes. These changes lead to paresis and maladaptation of the movement pattern. Secondary changes in mechanical muscle fiber, collagen tissue, and tendon properties (e.g., loss of sarcomeres, subclinical contractures) result in spastic muscle tone, which in part compensates for paresis and allows functional movements on a simpler level of organization. Antispastic drugs should primarily be applied in complete SCI. In mobile patients they can accentuate paresis and therefore should be applied with caution.

Effectiveness of pseudoephedrine as adjunctive therapy for neurogenic shock after acute spinal cord injury: a case series

STUDY OBJECTIVE

To evaluate the effectiveness of pseudoephedrine as adjunctive therapy for neurogenic shock in patients with acute spinal cord injury (SCI).

DESIGN

Case series.

SETTING

Academic medical center.

PATIENTS

Thirty-eight patients admitted to the trauma intensive care unit between September 2005 and October 2012 with an acute SCI and who received more than 1 day of pseudoephedrine for one or more of the following: treatment of bradycardia (heart rate ≤ 50 beats/min), treatment of hypotension (systolic blood pressure < 90 mm Hg), or were receiving intravenous vasopressor support.

MEASUREMENTS AND MAIN RESULTS

The effect of adjunctive pseudoephedrine (PSE) was categorized as a success if vasopressors were discontinued after the initiation of PSE or improvement in the number of episodes of bradycardia was noted after the initiation of PSE as evidenced by decreased use of atropine. The effect of pseudoephedrine was categorized as a failure if it did not meet one of the criteria for success. The effect of pseudoephedrine was categorized as inconclusive if there were confounding factors such as vasopressors being restarted for another indication after initial discontinuation. Pseudoephedrine was successful in 31/38 (82%) patients, failed in 2/38 (5%) patients, and had inconclusive results in 5/38 (13%) patients. The mean ± SD time to successful weaning of intravenous vasopressors was 7 ± 7 days. Daily maximum pseudoephedrine doses ranged from 60-720 mg. Mean ± SD duration of pseudoephedrine therapy was 32 ± 23 days (range 2-135 days), with 64.5% of surviving patients discharged while receiving pseudoephedrine.

CONCLUSION

These data suggest that pseudoephedrine is an effective adjunctive therapy in facilitating the discontinuation of intravenous vasopressors and/or atropine in patients with acute SCI with neurogenic shock, although patients will typically require long durations of therapy.

Training effectiveness when teaching the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) to medical students

STUDY DESIGN

Interventional training sessions.

OBJECTIVES

To examine the effectiveness of training medical students in the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI).

SETTING

A Peking University teaching hospital.

METHODS

A total of 46 medical students were involved in the study. First, they had a 2-h self-study session with the ISNCSCI booklet, followed by a 10-item questionnaire. The booklet was allowed for use as a reference during this assessment. Two days later, the questionnaire was repeated without the use of reference. Students then had a session with case discussion, followed by a final questionnaire.

RESULTS

After the initial self-study session, the mean score (max. 10) on the questionnaire was 7.67 ± 1.49. Two days later, the mean score of the second test was 7.96 ± 1.15. All key points of the ISNCSCI were supplemented during the second session with case presentations. The mean score of the final test increased significantly to 9.61 ± 0.88 (P<0.01) in comparison with the previous tests. The overall correct response rates by students in determining sensory level, motor level and American Spinal Injury Association Impairment Scale of the training case were 89.1%, 84.8% and 91.3%, respectively.

CONCLUSION

The training effectiveness of ISNCSCI through self-study is reliable. The correct answers to key points could remain for at least 2 days without the need to use a reference. However, some specialized knowledge could not be transmitted without more detailed discussions and case presentations. Utilization of cases is a valuable method in training ISNCSCI and can improve the overall training effectiveness.

Shock, diaschisis and von Monakow

The concept of shock apparently emerged in the middle of the 18th century (Whyett) as an occurrence observed experimentally after spinal cord transection, and identified as "shock" phenomenon one century later (Hall). The concept was extended (Brown-Séquard) and it was suggested that brain lesions caused functional rupture in regions distant from the injured one ("action à distance"). The term "diaschisis" (von Monakow), proposed as a new modality of shock, had its concept broadened, underpinned by observations of patients, aiming at distinguishing between symptoms of focal brain lesions and transitory effects they produced, attributable to depression of distant parts of the brain connected to the injured area. Presently, diaschisis is related mainly to cerebrovascular lesions and classified according to the connection fibers involved, as proposed by von Monakow. Depression of metabolism and blood flow in regions anatomically separated, but related by connections with the lesion, allows observing diaschisis with neuroimaging.

Correlations between severity of clinical signs and histopathological changes in 60 dogs with spinal cord injury associated with acute thoracolumbar intervertebral disc disease

The outcome of spinal surgery in dogs with absent voluntary motor function and nociception following intervertebral disc (IVD) herniation is highly variable, which likely attests to differences in the severity of spinal cord damage. This retrospective study evaluated the extent to which neurological signs correlated with histologically detected spinal cord damage in 60 dogs that were euthanased because of thoracolumbar IVD herniation. Clinical neurological grades correlated significantly with the extent of white matter damage (P<0.001). However, loss of nociception also occurred in 6/31 (19%) dogs with relatively mild histological changes. The duration of clinical signs, Schiff-Sherrington posture, loss of reflexes and pain on spinal palpation were not significantly associated with the severity of spinal cord damage. Although clinical-pathological correlation was generally good, some clinical signs frequently thought to indicate severe cord injury did not always correlate with the degree of cord damage, suggesting functional rather than structural impairment in some cases.

Peripheral neuropathy induces cutaneous hypersensitivity in chronically spinalized rats

BACKGROUND/OBJECTIVES

The present study was aimed at the issue of whether peripheral nerve injury-induced chronic pain is maintained by supraspinal structures governing descending facilitation to the spinal dorsal horn, or whether altered peripheral nociceptive mechanisms sustain central hyperexcitability and, in turn, neuropathic pain. We examined this question by determining the contribution of peripheral/spinal mechanisms, isolated from supraspinal influence(s), in cutaneous hypersensitivity in an animal model of peripheral neuropathy.

METHODS

Adult rats were spinalized at T8-T9; 8 days later, peripheral neuropathy was induced by implanting a 2-mm polyethylene cuff around the left sciatic nerve. Hind paw withdrawal responses to mechanical or thermal plantar stimulation were evaluated using von Frey filaments or a heat lamp, respectively.

RESULTS

Spinalized rats without cuff implantation exhibited a moderate decrease in mechanical withdrawal threshold on ~day 10 (P < 0.05) and in thermal withdrawal threshold on ~day 18 (P < 0.05). However, cuff-implanted spinalized rats developed a more rapid and significant decrease in mechanical (~day 4; P < 0.001) and thermal (~day 10; P < 0.05) withdrawal thresholds that remained significantly decreased through the duration of the study.

CONCLUSIONS

Our findings demonstrate an aberrant peripheral/spinal mechanism that induces and maintains thermal and to a greater degree tactile cutaneous hypersensitivity in the cuff model of neuropathic pain, and raise the prospect that altered peripheral/spinal nociceptive mechanisms in humans with peripheral neuropathy may have a pathologically relevant role in both inducing and sustaining neuropathic pain.

Characterization of the spectrum of hemodynamic profiles in trauma patients with acute neurogenic shock

OBJECTIVE

Neurogenic shock considered a distributive type of shock secondary to loss of sympathetic outflow to the peripheral vasculature. In this study, we examine the hemodynamic profiles of a series of trauma patients with a diagnosis of neurogenic shock.

METHODS

Hemodynamic data were collected on a series of trauma patients determined to have spinal cord injuries with neurogenic shock. A well-established integrated computer model of human physiology was used to analyze and categorize the hemodynamic profiles from a system analysis perspective. A differentiation between these categories was presented as the percent of total patients.

RESULTS

Of the 9 patients with traumatic neurogenic shock, the etiology of shock was decrease in peripheral vascular resistance (PVR) in 3 (33%; 95% confidence interval, 12%-65%), loss of vascular capacitance in 2 (22%; 6%-55%) and mixed peripheral resistance and capacitance responsible in 3 (33%; 12%-65%), and purely cardiac in 1 (11%; 3%-48%). The markers of sympathetic outflow had no correlation to any of the elements in the patients' hemodynamic profiles.

CONCLUSIONS

Results from this study suggest that hypotension of neurogenic shock can have multiple mechanistic etiologies and represents a spectrum of hemodynamic profiles. This understanding is important for the treatment decisions in managing these patients.

Lower motor neuron findings after upper motor neuron injury: insights from postoperative supplementary motor area syndrome

Hypertonia and hyperreflexia are classically described responses to upper motor neuron injury. However, acute hypotonia and areflexia with motor deficit are hallmark findings after many central nervous system insults such as acute stroke and spinal shock. Historic theories to explain these contradictory findings have implicated a number of potential mechanisms mostly relying on the loss of descending corticospinal input as the underlying etiology. Unfortunately, these simple descriptions consistently fail to adequately explain the pathophysiology and connectivity leading to acute hyporeflexia and delayed hyperreflexia that result from such insult. This article highlights the common observation of acute hyporeflexia after central nervous system insults and explores the underlying anatomy and physiology. Further, evidence for the underlying connectivity is presented and implicates the dominant role of supraspinal inhibitory influence originating in the supplementary motor area descending through the corticospinal tracts. Unlike traditional explanations, this theory more adequately explains the findings of postoperative supplementary motor area syndrome in which hyporeflexia motor deficit is observed acutely in the face of intact primary motor cortex connections to the spinal cord. Further, the proposed connectivity can be generalized to help explain other insults including stroke, atonic seizures, and spinal shock.

Neuro-immune interactions of neural stem cell transplants: from animal disease models to human trials

Stem cell technology is a promising branch of regenerative medicine that is aimed at developing new approaches for the treatment of severely debilitating human diseases, including those affecting the central nervous system (CNS). Despite the increasing understanding of the mechanisms governing their biology, the application of stem cell therapeutics remains challenging. The initial idea that stem cell transplants work in vivo via the replacement of endogenous cells lost or damaged owing to disease has been challenged by accumulating evidence of their therapeutic plasticity. This new concept covers the remarkable immune regulatory and tissue trophic effects that transplanted stem cells exert at the level of the neural microenvironment to promote tissue healing via combination of immune modulatory and tissue protective actions, while retaining predominantly undifferentiated features. Among a number of promising candidate stem cell sources, neural stem/precursor cells (NPCs) are under extensive investigation with regard to their therapeutic plasticity after transplantation. The significant impact in vivo of experimental NPC therapies in animal models of inflammatory CNS diseases has raised great expectations that these stem cells, or the manipulation of the mechanisms behind their therapeutic impact, could soon be translated to human studies. This review aims to provide an update on the most recent evidence of therapeutically-relevant neuro-immune interactions following NPC transplants in animal models of multiple sclerosis, cerebral stroke and traumas of the spinal cord, and consideration of the forthcoming challenges related to the early translation of some of these exciting experimental outcomes into clinical medicines.

Exercise pressor reflex function following acute hemi-section of the spinal cord in cats

Cardiovascular disease is a leading cause of morbidity and mortality in patients post spinal cord injury (SCI). The prescription of exercise as a therapeutic modality for disease prevention in this population is promising. It is logical to suggest that the sooner an exercise program can begin the more benefit the patient will receive from the therapy. However, the time point after injury at which the requisite circulatory responses needed to support exercise are viable remains largely unknown. The skeletal muscle exercise pressor reflex (EPR) significantly contributes to cardiovascular control during exercise in healthy individuals. Experiments in patients with a chronic lateral hemi-section of the spinal cord (Brown-Séquard syndrome) suggest that the EPR, although blunted, is operational when examined months to years post injury. However, whether this critically important reflex remains functional immediately after lateral SCI or, in contrast, experiences a period of reduced capacity due to spinal shock has not been established. This study was designed to assess EPR function after acute lateral transection of the spinal cord. The EPR was selectively activated in seven decerebrate cats via electrically stimulated static contraction of the triceps surae muscles of each hindlimb before and after lateral hemi-section of the T₁₃–L₂ region of the spinal cord. Compared to responses prior to injury, increases in mean arterial pressure (MAP) were significantly decreased when contracting the hindlimb either ipsilateral to the lesion (MAP = 17 ± 3 mmHg before and 9 ± 2 mmHg after) or contralateral to the lesion (MAP = 22 ± 5 mmHg before and 12 ± 4 mmHg after). The heart rate (HR) response to stimulation of the EPR was largely unaffected by induction of acute SCI. The findings suggest that the EPR maintains the ability to importantly contribute to cardiovascular regulation during exercise immediately following a Brown-Séquard-like injury.

Transverse myelitis

Transverse myelitis (TM) includes a pathobiologically heterogeneous syndrome characterized by acute or subacute spinal cord dysfunction resulting in paresis, a sensory level, and autonomic (bladder, bowel, and sexual) impairment below the level of the lesion. Etiologies for TM can be broadly classified as parainfectious, paraneoplastic, drug/toxin-induced, systemic autoimmune disorders, and acquired demyelinating diseases. We discuss the clinical evaluation, workup, and acute and long-term management of patients with TM. Additionally, we briefly discuss various disease entities that may cause TM and their salient distinguishing features, as well as disorders that may mimic TM.

Discharge rates and discharge variability of muscle spindle afferents in human chronic spinal cord injury

OBJECTIVES

To test the hypothesis that the firing rates and discharge variability of human muscle spindles are not affected by spinal cord injury.

METHODS

Tungsten microelectrodes were inserted into muscle fascicles of the peroneal nerve in six individuals with complete paralysis of the lower limbs following spinal cord injury: 12 afferents were spontaneously active at rest and 7 were recruited during passive muscle stretch. For comparison, recordings were made from 17 spontaneously active and 9 stretch-recruited afferents in 12 intact subjects.

RESULTS

Firing rates for the spontaneously active muscle spindles were not significantly different between the spinal (9.8 ± 1.6 Hz) and intact (10.2 ± 1.3 Hz) subjects; the same was true for the stretch-recruited afferents - static firing rates, measured over the final 1s of a ramp-and-hold stretch, were not different between the spinal and intact groups (13.1 ± 3.1% vs 10.0 ± 2.5 Hz). There were also no differences in discharge variability between the spinal and intact subjects, either for the spontaneously active spindles (8.1 ± 2.0% vs 5.7 ± 0.9%) or for the stretch-activated spindles, calculated over the final 1s of static stretch (19.7 ± 5.6% vs 17.0 ± 1.9%). In addition, the responses to stretch imposed manually by the experimenter provided no evidence for an increase in the dynamic response to stretch in the patients.

CONCLUSIONS

The static stretch sensitivity of human muscle spindles is not affected by chronic spinal cord injury, suggesting that there is no difference in static (and possibly dynamic) fusimotor drive to paralyzed muscles in chronic spinal cord injury.

SIGNIFICANCE

This study provides no evidence for an increase in fusimotor drive as a mechanism for the spasticity associated with chronic spinal injury, though further studies using controlled stretch would be required before it can be concluded that dynamic fusimotor drive is "normal" in these patients.

Recovery of inspiratory intercostal muscle activity following high cervical hemisection

Anatomical and neurophysiological evidence indicates that thoracic interneurons can serve a commissural function and activate contralateral motoneurons. Accordingly, we hypothesized that respiratory-related intercostal (IC) muscle electromyogram (EMG) activity would be only modestly impaired by a unilateral cervical spinal cord injury. Inspiratory tidal volume (VT) was recorded using pneumotachography and EMG activity was recorded bilaterally from the 1st to 2nd intercostal space in anesthetized, spontaneously breathing rats. Studies were conducted at 1-3 days, 2 wks or 8 wks following C2 spinal cord hemisection (C2HS). Data were collected during baseline breathing and a brief respiratory challenge (7% CO(2)). A substantial reduction in inspiratory intercostal EMG bursting ipsilateral to the lesion was observed at 1-3 days post-C2HS. However, a time-dependent return of activity occurred such that by 2 wks post-injury inspiratory intercostal EMG bursts ipsilateral to the lesion were similar to age-matched, uninjured controls. The increases in ipsilateral intercostal EMG activity occurred in parallel with increases in VT following the injury (R=0.55; P<0.001). We conclude that plasticity occurring within a "crossed-intercostal" circuitry enables a robust, spontaneous recovery of ipsilateral intercostal activity following C2HS in rats.

Early versus delayed decompression for traumatic cervical spinal cord injury: results of the Surgical Timing in Acute Spinal Cord Injury Study (STASCIS)

BACKGROUND

There is convincing preclinical evidence that early decompression in the setting of spinal cord injury (SCI) improves neurologic outcomes. However, the effect of early surgical decompression in patients with acute SCI remains uncertain. Our objective was to evaluate the relative effectiveness of early (<24 hours after injury) versus late (≥ 24 hours after injury) decompressive surgery after traumatic cervical SCI.

METHODS

We performed a multicenter, international, prospective cohort study (Surgical Timing In Acute Spinal Cord Injury Study: STASCIS) in adults aged 16-80 with cervical SCI. Enrolment occurred between 2002 and 2009 at 6 North American centers. The primary outcome was ordinal change in ASIA Impairment Scale (AIS) grade at 6 months follow-up. Secondary outcomes included assessments of complications rates and mortality.

FINDINGS

A total of 313 patients with acute cervical SCI were enrolled. Of these, 182 underwent early surgery, at a mean of 14.2(± 5.4) hours, with the remaining 131 having late surgery, at a mean of 48.3(± 29.3) hours. Of the 222 patients with follow-up available at 6 months post injury, 19.8% of patients undergoing early surgery showed a ≥ 2 grade improvement in AIS compared to 8.8% in the late decompression group (OR = 2.57, 95% CI:1.11,5.97). In the multivariate analysis, adjusted for preoperative neurological status and steroid administration, the odds of at least a 2 grade AIS improvement were 2.8 times higher amongst those who underwent early surgery as compared to those who underwent late surgery (OR = 2.83, 95% CI:1.10,7.28). During the 30 day post injury period, there was 1 mortality in both of the surgical groups. Complications occurred in 24.2% of early surgery patients and 30.5% of late surgery patients (p = 0.21).

CONCLUSION

Decompression prior to 24 hours after SCI can be performed safely and is associated with improved neurologic outcome, defined as at least a 2 grade AIS improvement at 6 months follow-up.

The changing landscape of spinal cord injury

In the past quarter century, spinal cord injury medicine has welcomed the proliferation of new medications and technologies that improve the survival and quality of life for people with spinal cord injury, but also endured the failure of strategies we hoped would salvage the cord in the acute phase. Surgical decompression and spinal stabilization should be pursued whenever indicated and feasible; however, there is no compelling evidence that early decompression facilitates neurological improvement. Methylprednisolone, the subject of over two decades of trials, has proven to be of marginal benefit in improving functional outcome. Recent advances in the management of the respiratory, cardiovascular, autonomic, endocrine, skeletal and integumentary systems have not only changed morbidity and survival of spinal cord injury patients but also improved quality of life. Progress has been made in the early diagnosis and effective treatment of cardiac arrhythmias, neurogenic shock, autonomic dysreflexia and orthostatic hypotension. Aggressive respiratory care for high cervical level of injury patients should include an option for phrenic nerve pacing as it is a viable rehabilitative strategy for appropriately selected patients. Pressure ulcers remain a significant psychological, financial, and functional burden for many people with SCI and for healthcare providers. This area will continue to require further work on early prevention and education. Despite extensive scientific and clinical data on neurogenic osteoporosis, there is no consensus regarding the best pharmacotherapeutic agents, dosing regimens, or rehabilitative strategies for prevention and treatment of bone loss. This chapter will focus on the advances.

Diagnosis and prognosis of traumatic spinal cord injury

Despite promising advances in basic spinal cord repair research, no effective therapy resulting in major neurological or functional recovery after traumatic spinal cord injury (tSCI) is available to date. The neurological examination according to the International Standards for Neurological and Functional Classification of Spinal Cord Injury Patients (International Standards) has become the cornerstone in the assessment of the severity and level of the injury. Based on parameters from the International Standards, physicians are able to inform patients about the predicted long-term outcomes, including the ability to walk, with high accuracy. In those patients who cannot participate in a reliable physical neurological examination, magnetic resonance imaging and electrophysiological examinations may provide useful diagnostic and prognostic information. As clinical research on this topic continues, the prognostic value of the reviewed diagnostic assessments will become more accurate in the near future. These advances will provide useful information for physicians to counsel tSCI patients and their families during the catastrophic initial phase after the injury.

Comprehensive locomotor outcomes correlate to hyperacute diffusion tensor measures after spinal cord injury in the adult rat

In adult rats, locomotor deficits following a contusive thoracic spinal cord injury (SCI) are caused primarily by white matter loss/dysfunction at the epicenter. This loss/dysfunction decreases descending input from the brain and cervical spinal cord, and decreases ascending signals in long propriospinal, spinocerebellar and somatosensory pathways, among many others. Predicting the long-term functional consequences of a contusive injury acutely, without knowledge of the injury severity is difficult due to the temporary flaccid paralysis and loss of reflexes that accompany spinal shock. It is now well known that recovery of high quality hindlimb stepping requires only 12-15% spared white matter at the epicenter, but that forelimb-hindlimb coordination and precision stepping (grid or horizontal ladder) require substantially more trans-contusion communication. In order to translate our understanding of the neural substrates for functional recovery in the rat to the clinical arena, common outcome measures and imaging modalities are required. In the current study we furthered the exploration of one of these approaches, diffusion tensor magnetic resonance imaging (DTI), a technique now used commonly to image the brain in clinical research but rarely used diagnostically or prognostically for spinal cord injury. In the adult rat model of SCI, we found that hyperacute (<3h post-injury) DTI of the lateral and ventral white matter at the injury epicenter was predictive of both electrophysiological and behavioral (locomotor) recovery at 4 weeks post-injury, despite the presence of flaccid paralysis/spinal shock. Regions of white matter with a minimum axial diffusivity of 1.5 μm(2)/ms at 3h were able to conduct action potentials at 4 weeks, and axial diffusivity within the lateral funiculus was highly predictive of locomotor function at 4 weeks. These observations suggest that acute DTI should be useful to provide functional predictions for spared white matter following contusive spinal cord injuries clinically.

A literature review of the pathophysiology and onset of post-stroke spasticity

BACKGROUND

Spasticity occurs after stroke and gives rise to substantial burden for patients and caregivers. Although it has been studied for many years, its definition continues to undergo reconsideration and revision. This partly reflects the diversity of its manifestations and that its pathophysiology, although well studied, is still debated.

METHODS

A literature review was carried out to define the pathophysiology and risk factors for onset of post-stroke spasticity.

RESULTS

It is clear that an acquired brain injury, including stroke, results in an imbalance of inhibitory and excitatory impulses that leads to upper motor neuron symptoms and that the location and extent of the lesions result in differing symptoms and degrees of spastic severity. The onset of spasticity is highly variable and may occur shortly or more than 1 year after stroke. The current understanding of spasticity onset is complicated by the role of contractures, which have been assumed to arise out of spasticity but may have a role in its cause. Other possibly predictive factors for the risk of post-stroke spasticity have been identified, including early arm and leg weakness, left-sided weakness, early reduction in activities of daily living, and a history of smoking.

CONCLUSIONS

Further understanding of spasticity risk factors is necessary for the development and integration of early interventions and preventive measures to reduce spasticity onset and severity.

The animal model of spinal cord injury as an experimental pain model

Pain, which remains largely unsolved, is one of the most crucial problems for spinal cord injury patients. Due to sensory problems, as well as motor dysfunctions, spinal cord injury research has proven to be complex and difficult. Furthermore, many types of pain are associated with spinal cord injury, such as neuropathic, visceral, and musculoskeletal pain. Many animal models of spinal cord injury exist to emulate clinical situations, which could help to determine common mechanisms of pathology. However, results can be easily misunderstood and falsely interpreted. Therefore, it is important to fully understand the symptoms of human spinal cord injury, as well as the various spinal cord injury models and the possible pathologies. The present paper summarizes results from animal models of spinal cord injury, as well as the most effective use of these models.

The role of propriospinal interneurons in recovery from spinal cord injury

Over one hundred years ago, Sir Charles Sherrington described a population of spinal cord interneurons (INs) that connect multiple spinal cord segments and participate in complex or 'long' motor reflexes. These neurons were subsequently termed propriospinal neurons (PNs) and are known to play a crucial role in motor control and sensory processing. Recent work has shown that PNs may also be an important substrate for recovery from spinal cord injury (SCI) as they contribute to plastic reorganisation of spinal circuits. The location, inter-segmental projection pattern and sheer number of PNs mean that after SCI, a significant number of them are capable of 'bridging' an incomplete spinal cord lesion. When these properties are combined with the capacity of PNs to activate and coordinate locomotor central pattern generators (CPGs), it is clear they are ideally placed to assist locomotor recovery. Here we summarise the anatomy, organisation and function of PNs in the uninjured spinal cord, briefly outline the pathophysiology of SCI, describe how PNs contribute to recovery of motor function, and finally, we discuss the mechanisms that underlie PN plasticity. We propose there are two major challenges for PN research. The first is to learn more about ways we can promote PN plasticity and manipulate the 'hostile' micro-environment that limits regeneration in the damaged spinal cord. The second is to study the cellular/intrinsic properties of PNs to better understand their function in both the normal and injured spinal cord. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.

Effect of repeatedly given CDP-choline on cardiovascular and tissue injury in spinal shock conditions: investigation of the acute phase

OBJECTIVES

The protective effect of CDP-choline in spinal cord transection and the mediation of its cardiovascular effects were investigated.

METHODS

Spinal cords of rats were transected at the T1-T2 levels. CDP-choline (250 mg/kg; intravenous) was administered 2 h and/or 24 h after the injury.

KEY FINDINGS

Spinal cord transection caused severe tissue damage, decreased mean arterial pressure, heart rate, plasma adrenaline, and noradrenaline but increased plasma vasopressin levels. Repeated CDP-choline treatment attenuated the degree of tissue injury. Administration of CDP-choline at 2 h after transection transiently increased blood pressure and decreased heart rate, while it produced a small decrease in blood pressure and heart rate when it was given at 24 h. Plasma adrenaline levels were higher in the group where CDP-choline was given repeatedly. Plasma noradrenaline and vasopressin levels did not change additionally after CDP-choline injections in all groups. In order to determine if CDP-choline attenuates the oxidative injury induced by transection, we measured blood superoxide dismutase, glutathione peroxidase activity and malondialdehyde levels. Repeated CDP-choline administration decreased blood superoxide dismutase and glutathione peroxidase activity without any effect on malondialdehyde levels.

CONCLUSIONS

Data indicate that repeated intravenous CDP-choline treatment prevents tissue damage in spinal shock conditions in the acute phase. The cardiovascular effects of the drug do not seem to be responsible for this protection but the drug-induced attenuation of the oxidative stress may play a role.

Quadriplegia recovery after hemi-section and transplant model of spinal cord at the level of C5 and C6

A spinal cord hemi-section with a homologous transplant of medullar tissue at the level of C5-C6 and preservation of the anterior spinal artery was used to evaluate the histological characteristics such as quantity and quality of axons, myelin index and blood vessels after quadriplegia recovery. Vascular changes after spinal injury results in severe endothelial damage, axonal edema, neuronal necrosis and demyelinization as well as cysts and infarction. Preservation of the anterior spinal artery has demonstrated clinical recuperation; therefore, in addition to the lesion we included a homologous transplant to visualize changes at a cellular level. Two groups of dogs (hemi-section and transplant) went through a traumatic spinal cord hemi-section of 50% at the level of C5-C6. The transplant group formed by animals which simultaneously had 4 mm of spinal cord removed and the equal amount substituted from a donor animal at the level of C5-C6 corresponding to the half right side; both preserving the anterior spinal artery. Histological evaluation of all groups took place at days 3 (acute) and 28 (chronic) post-operation. Changes of degeneration and axonal regeneration were found in the hemi-section and transplant groups at acute and chronic time, as well as same quadriplegia recovery at chronic time in the hemi-section and transplant groups which closely related to mechanisms which participate in regeneration and functional recuperation due to the preservation of the anterior spinal artery and presence of new blood vessels.

Functional evaluation of paraplegic monkeys (Macaca mulatta) over fourteen months post-lesion

We report on the neurological and neurophysiological findings obtained from two adult Macaca mulatta sustaining complete spinal cord transections at T8-T9. We performed periodic neurological exams, recorded motor evoked potentials (MEPs) following transcranial magnetic stimulation (TMS), and recorded electromyograms (EMGs) during the execution of a lower limb motor test. The main observations were: (1) the spinal shock period lasted less than a week; tendon, cutaneous and withdrawal reflexes were uneven in range and occurrence, and Babinski's sign was not observed; (2) a protracted functional lesion in the tibial and common peroneal nerves appeared bilaterally early in the post-lesional period; (3) MEPs were elicited by TMS in the quadriceps muscle of both monkeys; they were recorded as early as the 5th week after lesion in one of the monkeys, and they persisted throughout the post-lesional period in both monkeys; and (4) motor unit action potentials in the quadriceps muscle recorded by EMG were simultaneous with attempts to perform intentional lower limb movements from post-lesion month 11 to 13.5 in both monkeys. The last two sets of observations argue in favor of a partial cortico-spinal functional gain and suggest that spinal cord regeneration can occur after complete spinal cord injury in primates.

Diffusion tensor imaging at 3 hours after traumatic spinal cord injury predicts long-term locomotor recovery

Accurate diagnosis of spinal cord injury (SCI) severity must be achieved before highly aggressive experimental therapies can be tested responsibly in the early phases after trauma. These studies demonstrate for the first time that axial diffusivity (lambda||), derived from diffusion tensor imaging (DTI) within 3 h after SCI, accurately predicts long-term locomotor behavioral recovery in mice. Female C57BL/6 mice underwent sham laminectomy or graded contusive spinal cord injuries at the T9 vertebral level (5 groups, n = 8 for each group). In-vivo DTI examinations were performed immediately after SCI. Longitudinal measurements of hindlimb locomotor recovery were obtained using the Basso mouse scale (BMS). Injured and spared regions of ventrolateral white matter (VLWM) were reliably separated in the hyperacute phase by threshold segmentation. Measurements of lambda|| were compared with histology in the hyperacute phase and 14 days after injury. The spared normal VLWM determined by hyperacute lambda|| and 14-day histology correlated well (r = 0.95). A strong correlation between hindlimb locomotor function recovery and lambda||-determined spared normal VLWM was also observed. The odds of significant locomotor recovery increased by 18% with each 1% increase in normal VLWM measured in the hyperacute phase (odds ratio = 1.18, p = 0.037). The capability of measuring subclinical changes in spinal cord physiology and murine genetic advantages offer an early window into the basic mechanisms of SCI that was not previously possible. Although significant obstacles must still be overcome to derive similar data in human patients, the path to clinical translation is foreseeable and achievable.

Spinal cord injury from spontaneous epidural hematoma: report of 2 cases

Two cases of acute spinal cord injury resulting from spontaneous spinal epidural hematoma are reported, both of which had a cavernous vascular malformation origin. Both spontaneous spinal epidural hematoma and intramedullary cavernous malformation are rare in children. In the pediatric emergency setting, spontaneous epidural hematoma should be considered as part of the differential diagnosis for acute extremity weakness and paresthesia. Immediate magnetic resonance imaging of the brain and spine as well as prompt neurosurgical consult is recommended for the best chance of improved outcome.

Characterization of graded multicenter animal spinal cord injury study contusion spinal cord injury using somatosensory-evoked potentials

STUDY DESIGN

Electrophysiological analysis using somatosensory-evoked potentials (SEPs) and behavioral assessment using Basso, Beattie, Bresnahan (BBB) scale were compared over time for graded Multicenter Animal Spinal Cord Injury Study (MASCIS) contusion spinal cord injury (SCI).

OBJECTIVE

To study the SEP responses across different contusion injury severities and to compare them with BBB scores.

SUMMARY OF BACKGROUND DATA

For any SCI therapy evaluation, it is important to accurately and objectively standardize the injury model. The graded MASCIS contusion injuries on dorsal spine have been standardized using BBB, which is subjective and prone to human errors. Furthermore, dorsal pathway disruption does not always produce locomotor deficits. SEP monitoring provides an advantage of providing a reliable and objective assessment of the functional integrity of dorsal sensory pathways.

METHODS

Four groups of Fischer rats received contusion at T8 using New York University (NYU)-MASCIS impactor from impact heights of 6.25 mm (mild), 12.5 mm (moderate), 25 mm (severe), or 50 mm (very severe). The control group underwent laminectomy only. SEP and BBB recordings were performed once before injury, and then weekly for up to 7 weeks.

RESULTS

Graded levels of injury produced concomitant attenuations in hindlimb SEP amplitudes. Following injury, 25 and 50 mm groups together differed significantly from 12.5 and 6.25 mm groups (P < 0.01). From week 5, differences between 12.5 and 6.25 mm groups also became apparent (P < 0.01), which showed significant electrophysiological improvement. However, no significant differences were observed between 25 and 50 mm groups, which showed negligible electrophysiological recovery. Although comparable differences between different groups were also detected by BBB after injury (P < 0.001), BBB was less sensitive in detecting any improvement in 6.25 and 12.5 mm groups.

CONCLUSION

SEP amplitudes and BBB scores decrease corresponding to increase in injury severity, however, these show different temporal patterns of recovery. These results demonstrate the utility of SEPs in conjunction with BBB, to monitor therapeutic interventions in SCI research.

The acute respiratory management of cervical spinal cord injury in the first 6 weeks after injury: a systematic review

STUDY DESIGN

Systematic review.

OBJECTIVES

Identify, evaluate, and synthesize evidence regarding the effectiveness of various treatment strategies for the respiratory management of acute tetraplegia.

SETTING

Melbourne, Australia.

METHODS

A search of multiple electronic databases (Medline, Cinahl, EMBASE, Cochrane Library, Web of Science, http://www.guideline.gov and http://www.icord.org/scire) was undertaken accompanied by the reference lists of all relevant articles identified. Methodological quality was assessed using the Newcastle-Ottawa Scale and the PEDro Scale. Descriptive analysis was performed.

RESULTS

Twenty-one studies including 1263 patients were identified. The majority of the studies were case series (n = 13). A variety of interventions were used for the management of respiratory complications. Mortality (ARR = 0.4, 95% confidence interval (CI) 0.18, 0.61), the incidence of respiratory complications (ARR = 0.36, 95% CI (0.08, 0.58)), and requirement for a tracheostomy (ARR = 0.18, 95% CI (-0.05, 0.4)) were significantly reduced by using a respiratory protocol. A clinical pathway reduced duration of mechanical ventilation by 6 days 95% CI (-0.56, 12.56), intensive care unit length of stay by 6.8 days 95% CI (0.17-13.77) and costs. Intubation, mechanical ventilation, and tracheostomy are the mainstay of respiratory management for complete injuries above the level of C5.

CONCLUSION

This review showed a clinical pathway with a structured respiratory protocol that includes a combination of treatment techniques provided regularly is effective in reducing respiratory complications and cost. The overall study quality was moderate and further studies using specific interventions that target respiratory complications are associated with specific regions of the cervical spine using more methodologically rigorous designs are required.

Excitability changes in the sciatic nerve and triceps surae muscle after spinal cord injury in mice

BACKGROUND

From the onset to the chronic phase of spinal cord injury (SCI), peripheral axons and muscles are subjected to abnormal states of activity. This starts with very intense spasms during the first instant of SCI, through a no activity flaccidity phase, to a chronic hyperactivity phase. It remains unclear how the nature of this sequence may affect the peripheral axons and muscles.

METHODS

We set out to investigate the changes in excitability of the sciatic nerve and to characterize the properties of muscle contractility after contusive injury of the mouse thoracic spinal cord.

RESULTS

The following changes were observed in animals after SCI: 1) The sciatic nerve compound action potential was of higher amplitudes and lower threshold, with the longer strength-duration time constant and faster conduction velocity; 2) The latency of the onset of muscle contraction of the triceps surae muscle was significantly shorter in animals with SCI; 3) The muscle twitches expressed slower rising and falling slopes, which were accompanied by prolonged contraction duration in SCI animals compared to controls.

CONCLUSION

These findings suggest that in peripheral nerves SCI promotes hyperexcitability, which might contribute to mechanisms of spastic syndrome.