Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP Panel: clinical trial inclusion/exclusion criteria and ethics

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the third of four papers. It examines inclusion and exclusion criteria that can influence the design and analysis of clinical trials in SCI, together with confounding variables and ethical considerations. Inclusion and exclusion criteria for clinical trials should consider several factors. Among these are (1) the enrollment of subjects at appropriate stages after SCI, where there is supporting data from animal models or previous human studies; (2) the severity, level, type, or size of the cord injury, which can influence spontaneous recovery rate and likelihood that an experimental treatment will clinically benefit the subject; and (3) the confounding effects of various independent variables such as pre-existing or concomitant medical conditions, other medications, surgical interventions, and rehabilitation regimens. An issue of substantial importance in the design of clinical trials for SCI is the inclusion of blinded assessments and sham surgery controls: every effort should be made to address these major issues prospectively and carefully, if clear and objective information is to be gained from a clinical trial. The highest ethical standards must be respected in the performance of clinical trials, including the adequacy and clarity of informed consent.

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP panel: clinical trial design

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the fourth of four papers. Here, we examine the phases of a clinical trial program, the elements, types, and protocols for valid clinical trial design. The most rigorous and valid SCI clinical trial would be a prospective double-blind randomized control trial utilizing appropriate placebo control subjects. However, in specific situations, it is recognized that other trial procedures may have to be considered. We review the strengths and limitations of the various types of clinical trials with specific reference to SCI. It is imperative that the design and conduct of SCI clinical trials should meet appropriate standards of scientific inquiry to insure that meaningful conclusions about efficacy and safety can be achieved and that the interests of trial subjects are protected. We propose these clinical trials guidelines for use by the SCI clinical research community.

Dynamic role of kallikrein 6 in traumatic spinal cord injury

Kallikrein 6 (K6) is a member of the kallikrein gene family that comprises 15 structurally and functionally related serine proteases. In prior studies we showed that, while this trypsin-like enzyme is preferentially expressed in neurons and oligodendroglia of the adult central nervous system (CNS), it is up-regulated at sites of injury due to expression by infiltrating immune and resident CNS cells. Given this background we hypothesized that K6 is a key contributor to the pathophysiology of traumatic spinal cord injury (SCI), influencing neural repair and regeneration. Examination of K6 expression following contusion injury to the adult rat cord, and in cases of human traumatic SCI, indicated significant elevations at acute and chronic time points, not only at the injury site but also in cord segments above and below. Elevations in K6 were particularly prominent in macrophages, microglia and reactive astrocytes. To determine potential effects of elevated K6 on the regeneration environment, the ability of neurons to adhere to and extend processes on substrata which had been exposed to recombinant K6 was examined. Limited (1 h) or excess (24 h) K6-mediated proteolytic digestion of a growth-facilitatory substrate, laminin, significantly decreased neurite outgrowth. By contrast, similar hydrolysis of a growth-inhibitory substrate, aggrecan, significantly increased neurite extension and cell adherence. These data support the hypothesis that K6 enzymatic cascades mediate events secondary to spinal cord trauma, including dynamic modification of the capacity for axon outgrowth.

Direct decompressive surgery with post-operative radiotherapy (S + RT) versus radiotherapy (RT) alone for the treatment of metastatic epidural spinal cord compression (MESCC): A cost-utility analysis using Ontario health economic data

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Background: For selected patients with MESCC, S + RT has recently been shown to improve patients’ ability to ambulate and reduce opioid and corticosteroid use when compared with RT alone, with a trend towards survival benefit. (Patchell et al Lancet 2005) The economic impact of adopting this intervention has not been assessed previously. Methods: An analytic decision model was constructed based on the results from Patchell et al. (2005) The perspective of the public health care insurer of Ontario was adopted for the analysis. Costing was performed by using Ontario data for the following items: surgery, radiotherapy, hospitalization, home care services, palliative hospice, and medications. Utilities were obtained from the Harvard University Catalogue of preference score (HUC) and the Health Outcomes Data Repository Data - Health Utility list (HODaR). The primary analysis is a cost-utility analysis comparing surgery and radiotherapy (S+RT) with radiotherapy alone (RT). A probabilistic sensitivity analysis with Monte-Carlo simulation was performed. Results: When comparing S+ RT with RT alone, the incremental cost-effectiveness ratio (ICER) is CAD$ 43,796 per QALY gained. The cost-utility of S + RT is CAD$ 509,084 per QALY and that of RT alone is CAD$ 2,381,246 per QALY. S + RT costs approximately CAD$ 33 more when compared with RT alone per ambulatory day gained. The cost of surgery is partially offset by the decreased cost of hospice palliative care since more patients remain ambulatory and stay at home. Monte-Carlo simulation showed that there is a 25% chance that S + RT may dominate RT alone. The results are sensitive but generally robust to changes in assumptions about the costs of surgery, home care and palliative hospice care. Conclusions: S+RT is likely cost-effective when compared with RT alone for the treatment of MESCC in selected patients, and should be considered by health care policy makers.

No significant financial relationships to disclose.

Somatosensory cortical atrophy after spinal cord injury: a voxel-based morphometry study

The authors used voxel-based morphometry to compare sensorimotor cortical gray and white matter volume on structural MR images of a group of 17 individuals with cervical spinal cord injury (SCI) and a group of 17 healthy subjects. SCI subjects had reduced gray matter volume bilaterally in primary somatosensory cortex (p < 0.001). These findings suggest that the somatosensory cortex of the human brain atrophies after SCI.

FAS deficiency reduces apoptosis, spares axons and improves function after spinal cord injury

After spinal cord injury (SCI), apoptosis of neurons and oligodendrocytes is associated with axonal degeneration and loss of neurological function. Recent data have suggested a potential role for FAS death receptor-mediated apoptosis in the pathophysiology of SCI. In this study, we examined the effect of FAS deficiency on SCI in vitro and in vivo. FAS(Lpr/lpr) mutant mice and wildtype background-matched mice were subjected to a T5-6 clip compression SCI, and complementary studies were done in an organotypic slice culture model of SCI. Post-traumatic apoptosis in the spinal cord, which was seen in neurons and oligodendrocytes, was decreased in the FAS-deficient mice both in vivo and in vitro particularly in oligodendrocytes. FAS deficiency was also associated with improved locomotor recovery, axonal sparing and preservation of oligodendrocytes and myelin. However, FAS deficiency did not result in a significant increase in surviving neurons in the spinal cord at 6 weeks after injury, likely reflecting the importance of other cell death mechanisms for neurons. We conclude that inhibition of the FAS pathway may be a clinically attractive neuroprotective strategy directed towards oligodendroglial and axonal preservation in the treatment of SCI and neurotrauma.

Autonomic dysreflexia after spinal cord transection or compression in 129Sv, C57BL, and Wallerian degeneration slow mutant mice

To study plasticity of central autonomic circuits that develops after spinal cord injury (SCI), we have characterized a mouse model of autonomic dysreflexia. Autonomic dysreflexia is a condition in which episodic hypertension occurs after injuries above the midthoracic segments of the spinal cord. As synaptic plasticity may be triggered by axonal degeneration, we investigated whether autonomic dysreflexia is reduced in mice when axonal degeneration is delayed after SCI. We subjected three strains of mice, Wld(S), C57BL, and 129Sv, to either spinal cord transection (SCT) or severe clip-compression injury (CCI). The Wld(S) mouse is a well-characterized mutant that exhibits delayed Wallerian degeneration. The CCI model is an injury paradigm in which significant the axonal degeneration is due to secondary events and therefore delayed relative to the time of the initial injury. We herein demonstrate that the incidence of autonomic dysreflexia is reduced in Wld(S) mice after SCT and in all mice after CCI. To determine if differences in afferent arbor sprouting could explain our observations, we assessed changes in the afferent arbor in each mouse strain after both SCT and CCI. We show that independent of the type of injury, 129Sv mice but not C57BL or Wld(S) mice demonstrated an increased small-diameter CGRP-immunoreactive afferent arbor after SCI. Our work thus suggests a role for Wallerian degeneration in the development of autonomic dysreflexia and demonstrates that the choice of mouse strain and injury model has important consequences to the generalizations that may be drawn from studies of SCI in mice.

Changes in glial cell white matter AMPA receptor expression after spinal cord injury and relationship to apoptotic cell death

Increasing evidence suggests that AMPA receptors (AMPARs) play a key role in mediating excitotoxic cell damage after acute spinal cord injury (SCI). However, the role of glial AMPARs in posttraumatic white matter injury requires further clarification. In the present study we examined the changes in AMPAR expression after SCI, the cellular distribution of these changes, and their association with apoptosis. Western blots revealed expression of GluR1, 3, and 4, but not GluR2, in spinal cord white matter. Immunohistochemistry was used to examine the distribution of AMPARs in spinal cord white matter. Quantification of AMPAR-expressing cells in spinal cord white matter indicated predominantly GluR3 expression in oligodendrocytes and predominantly GluR4 expression in astrocytes. A clip compression model of SCI was used to examine the changes in AMPAR expression in dorsal column white matter after injury. Quantitative analysis of GluR3 levels of expression indicated a significant decrease at 3 days postinjury compared to uninjured animals, followed by a recovery of expression by 2 weeks. GluR4 subunits followed a similar expression pattern. Gene message expression of GluR3 and GluR4 flip/flop mRNA splice variants exhibited a pattern of expression that correlated with protein expression. GluR3-expressing glia appeared to be more susceptible to apoptosis than GluR4-expressing cells. A large decline in GluR3-expressing oligodendrocytes suggests that this subunit may be associated with the induction of apoptosis in white matter glia, thus contributing to secondary injury mechanisms.

Importance of access to research information among individuals with spinal cord injury: results of an evidenced-based questionnaire

OBJECTIVE

To assess the interests and accessibility of patients with a spinal cord injury (SCI) to information in different areas of SCI.

SETTING

Spinal Program, Toronto Western Hospital, University Health Network.

METHODS

An interest assessment survey and the SF-36 (short form-36) questionnaire were mailed to SCI patients living in the community. The interest assessment examined patients' interest in information in many areas related to SCI, their current knowledge in these areas and the accessibility of different information formats.

RESULTS

Fourteen patients (45%) completed the questionnaires. Regardless of physical or mental health status, all patients expressed a high level of interest in SCI research and clinical trials. An Internet website proved to be the most preferred, accessible and comfortable information format for these patients. Patients expressed a lower interest in support groups and organizations. Results from the SF-36 showed poor social functioning was related to interest in support groups, and poor general health perception was related to interest in occupational and physical therapy.

CONCLUSION

The majority of SCI patients have a high interest in accessing SCI research information. The Internet is a favorable, comfortable and accessible tool for providing this information and will benefit all SCI patients. These results suggest that a significant number of patients with SCI would benefit from an accessible Internet-based information database that is relevant to the SCI patients population.

Attenuation of the electrophysiological function of the corpus callosum after fluid percussion injury in the rat

This study describes a new method used to evaluate axonal physiological dysfunction following fluid percussion induced traumatic brain injury (TBI) that may facilitate the study of the mechanisms and novel therapeutic strategies of posttraumatic diffuse axonal injury (DAI). Stimulated compound action potentials (CAP) were recorded extracellularly in the corpus callosum of superfused brain slices at 3 h, and 1, 3, and 7 days following central fluid percussion injury and demonstrated a temporal pattern of functional deterioration. The maximal CAP amplitude (CAPA) covaried with the intensity of impact 1 day following sham, mild (1.0-1.2 atm), and moderate (1.8-2.0 atm) injury (p < 0.05; 1.11 +/- 0.10, 0.82 +/- 0.11, and 0.49 +/- 0.08 mV, respectively). The CAPA in sham animals were approximately 1.1 mV and did not vary with survival interval (3 h, and 1, 3, and 7 days); however, they were significantly decreased at each time point following moderate injury (p < 0.05; 0.51 +/- 0.11, 0.49 +/- 0.08, 0.46 +/- 0.10, and 0.75 +/- 0.13 mV, respectively). The CAPA at 7 days in the injured group were higher than at 3 h, and 1 and 3 days. H&E and amyloid precursor protein (APP) light microscopic analysis confirmed previously reported trauma-induced axonal injury in the corpus callosum seen after fluid percussion injury. Increased APP expression was confirmed using Western blotting showing significant accumulation at 1 day (IOD 913.0 +/- 252.7; n = 3; p = 0.05), 3 days (IOD 753.1 +/- 159.1; n = 3; p = 0.03), and at 7 days (IOD 1093.8 = 105.0; n = 3; p = 0.001) compared to shams (IOD 217.6 +/- 20.4; n = 3). Thus, we report the characterization of white matter axonal dysfunction in the corpus callosum following TBI. This novel method was easily applied, and the results were consistent and reproducible. The electrophysiological changes were sensitive to the early effects of impact intensity, as well as to delayed changes occurring several days following injury. They also indicated a greater degree of attenuation than predicted by APP expression changes alone.

Adaptation in the motor cortex following cervical spinal cord injury

BACKGROUND

The nature of the adaptive changes that occur in the cerebral cortex following injury to the cervical spinal cord are largely unknown.

OBJECTIVE

To investigate these adaptive changes by examining the relationship between the motor cortical representation of the paretic right upper extremity compared with that of the tongue. The tongue was selected because the spinal cord injury (SCI) does not affect its movement and the cortical representation of the tongue is adjacent to that of the paretic upper extremity.

METHODS

FMRI was used to map cortical representations associated with simple motor tasks of the right upper extremity and tongue in 14 control subjects and 9 patients with remote (>5.5 months) cervical SCI.

RESULTS

The mean value for the site of maximum cortical activation during upper limb movement was identical between the two groups. The site of maximum left hemispheric cortical activation during tongue movement was 12.8 mm (p < 0.01) medial and superior to that of control subjects, indicating the presence of a shift in cortical activation.

CONCLUSION

The findings indicate that the adult motor cortex does indeed adapt following cervical SCI. The nature of the adaptation and the underlying biological mechanisms responsible for this change require further investigation.

The role and timing of decompression in acute spinal cord injury: what do we know? What should we do?

The management of acute spinal cord injury has traditionally concentrated on preventative measures as well as, for the better part of the previous century, conservative care. Pharmacologic interventions, in particular intravenous methylprednisolone therapy, have shown modest improvements in clinical trials and are still undergoing evaluation. More recent interest has focused on the role of surgical reduction and decompression, particularly "early" surgery. A review of the current evidence available in the literature suggests that there is no standard of care regarding the role and timing of surgical decompression. There are insufficient data to support overall treatment standards or guidelines for this topic. There are, however, Class II data indicating that early surgery (<24 hours) may be done safely after acute SCI. Furthermore, there are Class III data to suggest a role for urgent decompression in the setting of 1) bilateral facet dislocation and 2) incomplete spinal cord injury with a neurologically deteriorating patient. Whereas there is biologic evidence from experimental studies in animals that early decompression may improve neurologic recovery after SCI, the relevant time frame in humans remains unclear. To date, the role of decompression in patients with SCI is only supported by Class III and limited Class II evidence and accordingly can be considered only a practice option. Accordingly, there is a strong rationale to undertake prospective, controlled trials to evaluate the role and timing of decompression in acute SCI.

Epidemiology, demographics, and pathophysiology of acute spinal cord injury

Spinal cord injury occurs through various countries throughout the world with an annual incidence of 15 to 40 cases per million, with the causes of these injuries ranging from motor vehicle accidents and community violence to recreational activities and workplace-related injuries. Survival has improved along with a greater appreciation of patterns of presentation, survival, and complications. Despite much work having been done, the only treatment to date known to ameliorate neurologic dysfunction that occurs at or below the level of neurologic injury has been intravenous methylprednisolone therapy. Much research over the past 30 to 40 years has focused on elucidating the mechanisms of spinal cord injury, with the complex pathophysiologic processes slowly being unraveled. With a greater understanding of both primary and secondary mechanisms of injury, the roles of calcium, free radicals, sodium, excitatory amino acids, vascular mediators, and apoptosis have been elucidated. This review examines the epidemiology, demographics, and pathophysiology of acute spinal cord injury.

Mechanisms of axonal dysfunction after spinal cord injury: with an emphasis on the role of voltage-gated potassium channels

Dysfunction of surviving axons which traverse the site of spinal cord injury (SCI) appears to contribute to posttraumatic neurological deficits, though the underlying mechanisms remain unclear. Although demyelination of injured but surviving axons following trauma appear to be a major contributor of axonal conduction deficits, altered activity of ion channels may also play an important role. It has been theorized that exposure of K+ channels as a result of demyelination would result in a reduced safety factor of action potential propagation across the demyelinated region of the axon. This theory and electrophysiological studies using K+ channel blockers on animal nerve preparations prompted the investigation of 4-aminopyridine (4-AP), a blocker of rapidly activating voltage-gated K+ channels, as a therapeutic agent in both multiple sclerosis and spinal cord injured patients. Several preliminary clinical trials have already demonstrated therapeutic benefit of 4-AP in both multiple sclerosis and spinal cord injured patients. In this review, we shall give a comprehensive summary of the mechanisms of axonal dysfunction following SCI and how axonal dysfunction may have resulted due to specific pathological changes following trauma including the ultrastructural and molecular changes that occur to myelinated axons. The pathology of spinal cord injury is very complex and many different mechanisms may contribute to axonal conduction deficits and the associated sensory and motor loss.

Autonomic dysreflexia and primary afferent sprouting after clip-compression injury of the rat spinal cord

Spinal cord injury leads to many forms of autonomic dysfunction including autonomic dysreflexia, a condition involving recurrent episodes of paroxysmal hypertension and associated bradycardia. This hypertension may reach intensities that are life-threatening. We investigated autonomic dysreflexia and the sprouting of central processes of primary afferent neurons (a potential mechanism for autonomic dysreflexia) in a clinically-relevant calibrated clip-compression model of spinal cord injury in the rat. Autonomic dysreflexia was induced by colon distension in the conscious rats 2 weeks after severe (50-g) clip compression injury of the spinal cord at the 4th thoracic segment. The central arbor of small-diameter primary afferent fibers in laminae III-VII of the spinal cord dorsal horn was also assessed at 2 weeks after cord injury by quantitative morphometry, using calcitonin gene-related peptide as a marker. In response to colon distension, arterial pressure increased by 41 +/- 3 mmHg from a resting value of 109 +/- 4 mmHg, and heart rate decreased by 124 +/- 13 beats/min from a value of 515 +/- 16 beats/min (n = 7). Minimal locomotor function was recovered by these rats: by 2 weeks after injury they attained scores of only 3.1 +/- 1.3 on the Basso, Beattie and Bresnahan scale. Histopathology of the clip-compression lesion site in the cord consisted of extensive central necrosis extending several segments rostral and caudal to the lesion. Quantitative measures of the small-diameter afferent arbors revealed significant increases in area ranging from 20-27% in thoracolumbar segments caudal to the injury (n = 5) in comparison to sham-injured rats (n = 6). A second study was done to assess the impact of severity of injury on the relationship between the size of the primary afferent arbors and autonomic dysreflexia. At 2 weeks after milder (20-g) clip injury at T4, rats exhibited responses to colon distension that were not those associated with autonomic dysreflexia (n = 5). Arterial pressure increased by only 16 +/- 3 mmHg and heart rate tended to increase (+19 +/- 12 beats/min). These rats attained a locomotor score of 7.1 +/- 0.4 by 2 weeks. The lesions at the injury site also contained necrosis and mild cavitation within the gray matter. No change in the small-diameter afferent arbor was detected at 2 weeks after the 20-g clip injury at T4 (n = 6 rats). These findings suggest that after severe but not mild clip compression injury of the spinal cord, sprouting of the afferent component of the spinal reflex are contributes to the development of autonomic dysreflexia. Neither dysreflexia, nor changes in the afferent arbor size occurred after mild cord injury. This clinically relevant clip compression cord injury model, studied more frequently for locomotor function, is excellent for investigating mechanisms for the development of autonomic dysreflexia and strategies for its prevention.

Changes in axonal physiology and morphology after chronic compressive injury of the rat thoracic spinal cord

The spinal cord is rarely transected after spinal cord injury. Dysfunction of surviving axons, which traverse the site of spinal cord injury, appears to contribute to post-traumatic neurological deficits, although the underlying mechanisms remain unclear. The subpial rim frequently contains thinly myelinated axons which appear to conduct signals abnormally, although it is uncertain whether this truly reflects maladaptive alterations in conduction properties of injured axons during the chronic phase of spinal cord injury or whether this is merely the result of the selective survival of a subpopulation of axons. In the present study, we examined the changes in axonal conduction properties after chronic clip compression injury of the rat thoracic spinal cord, using the sucrose gap technique and quantitatively examined changes in the morphological and ultrastructural features of injured axonal fibers in order to clarify these issues. Chronically injured dorsal columns had a markedly reduced compound action potential amplitude (8.3% of control) and exhibited significantly reduced excitability. Other dysfunctional conduction properties of injured axons included a slower population conduction velocity, a longer refractory period and a greater degree of high-frequency conduction block at 200 Hz. Light microscopic and ultrastructural analysis showed numerous axons with abnormally thin myelin sheaths as well as unmyelinated axons in the injured spinal cord. The ventral column showed a reduced median axonal diameter and the lateral and dorsal columns showed increased median diameters, with evidence of abnormally large swollen axons. Plots of axonal diameter versus myelination ratio showed that post-injury, dorsal column axons of all diameters had thinner myelin sheaths. Noninjured dorsal column axons had a median myelination ratio (1.56) which was within the optimal range (1.43-1.67) for axonal conduction, whereas injured dorsal column axons had a median myelination ratio (1.33) below the optimal value. These data suggest that maladaptive alterations occur postinjury to myelin sheath thickness which reduce the efficiency of axonal signal transmission.In conclusion, chronically injured dorsal column axons show physiological evidence of dysfunction and morphological changes in axonal diameter and reduced myelination ratio. These maladaptive alterations to injured axons, including decrease in myelin thickness and the appearance of axonal swellings, contribute to the decreased excitability of chronically injured axons. These results further clarify the mechanisms underlying neurological dysfunction after chronic neurotrauma and have significant implications regarding approaches to augment neural repair and regeneration.

Oligodendroglial apoptosis occurs along degenerating axons and is associated with FAS and p75 expression following spinal cord injury in the rat

Apoptosis or programmed cell death has been reported after CNS trauma. However, the significance of this mechanism in the pathophysiology of spinal cord injury, in particular at the cervical level, requires further investigation. In the present study, we used the extradural clip compression model in the rat to examine the cellular distribution of apoptosis following cervical spinal cord injury, the relationship between glial apoptosis and post-traumatic axonal degeneration and the possible role of apo[apoptosis]-1, CD95 (FAS) and p75 in initiating post-traumatic glial apoptosis. In situ terminal-deoxy-transferase mediated dUTP nick end labeling revealed apoptotic cells, largely oligodendrocytes as identified by cell specific markers, in grey and white matter following spinal cord injury. Apoptotic cell death was confirmed using electron microscopy and by the demonstration of DNA laddering on agarose gel electrophoresis. Beta-amyloid precursor protein was used as a molecular marker of axonal degeneration on western blots and immunohistochemistry. Degeneration of axons was temporally and spatially co-localized with glial apoptosis. FAS and p75 protein expression was seen in astrocytes, oligodendrocytes and microglia, and was also seen in some apoptotic glia after cord injury. Both FAS and p75 increased in expression in a temporal course, which mirrored the development of cellular apoptosis. The downstream caspases 3 and 8, which are linked to FAS and p75, demonstrated activation at times of maximal apoptosis, while FLIP-L an inhibitor of caspase 8, decreased at times of maximal apoptosis. We conclude that axonal degeneration after traumatic spinal cord injury is associated with glial, in particular oligodendroglial, apoptosis. Activation of the FAS and p75 death receptor pathways may be involved in initiating this process.

Evaluation of the neuroprotective effects of sodium channel blockers after spinal cord injury: improved behavioral and neuroanatomical recovery with riluzole

OBJECT

Persistent activation of voltage-sensitive Na+ channels is associated with cellular toxicity and may contribute to the degeneration of neural tissue following traumatic brain and spinal cord injury (SCI). Pharmacological blockade of these channels can attenuate secondary pathophysiology and reduce functional deficits acutely.

METHODS

To determine the therapeutic effects of Na+ channel blockers on long-term tissue sparing and functional neurological recovery after traumatic SCI, the authors injected Wistar rats intraperitoneally with riluzole (5 mg/kg), phenytoin (30 mg/kg), CNS5546A, a novel Na+ channel blocker (15 mg/kg), or vehicle (2-HP3CD; 5 mg/kg) 15 minutes after induction of compressive SCI at C7-T1. Functional neurological recovery of coordinated hindlimb function and strength, assessed 1 week postinjury and weekly thereafter for 6 weeks, was significantly enhanced in animals treated with riluzole compared with the other treatment groups. Seven weeks postinjury the preservation of residual tissue and integrity of descending axons were determined with digital morphometrical and fluorescent histochemical analysis. All three Na+ channel blockers significantly enhanced residual tissue area at the injury epicenter compared with control. Riluzole significantly reduced tissue loss in rostrocaudal regions surrounding the epicenter, with overall sparing of gray matter and selective sparing of white matter. Also, counts of red nuclei neurons retrogradely labeled with fluorogold introduced caudal to the injury site were significantly increased in the riluzole group.

CONCLUSIONS

Systemic Na+ channel blockers, in particular riluzole, can confer significant neuroprotection after in vivo SCI and result in behavioral recovery and sparing of both gray and white matter.

Role of L- and N-type calcium channels in the pathophysiology of traumatic spinal cord white matter injury

Recent work has suggested a potential role for voltage-gated Ca(2+) channels in the pathophysiology of anoxic central nervous system white matter injury. To examine the relevance of these findings to neurotrauma, we conducted electrophysiological studies with inorganic Ca(2+) channels blockers and L- and N-subtype-specific calcium channel antagonists in an in vitro model of spinal cord injury. Confocal immunohistochemistry was used to examine for localization of L- and N-type calcium channels in spinal cord white matter tracts. A 30-mm length of dorsal column was isolated from the spinal cord of adult rats, pinned in an in vitro recording chamber and injured with a modified clip (2g closing force) for 15s. The functional integrity of the dorsal column was monitored electrophysiologically by quantitatively measuring the compound action potential at two points with glass microelectrodes. The compound action potential decreased to 71.4+/-2.0% of control (P<0. 05) after spinal cord injury. Removal of extracellular Ca(2+) promoted significantly greater recovery of compound action potential amplitude (86.3+/-7.6% of control; P< 0.05) after injury. Partial blockade of voltage-gated Ca(2+) channels with cobalt (20 microM) or cadmium (200 microM) conferred improvement in compound action potential amplitude. Application of the L-type Ca(2+) channel blockers diltiazem (50 microM) or verapamil (90 microM), and the N-type antagonist omega-conotoxin GVIA (1 microM), significantly enhanced the recovery of compound action potential amplitude postinjury. Co-application of the L-type antagonist diltiazem with the N-type blocker omega-conotoxin GVIA showed significantly greater (P<0.05) improvement in compound action potential amplitude than application of either drug alone. Confocal immunohistochemistry with double labelling for glial fibrillary acidic protein, GalC and NF200 demonstrated L- and N-type Ca(2+) channels on astrocytes and oligodendrocytes, but not axons, in spinal cord white matter. In conclusion, the injurious effects of Ca(2+) in traumatic central nervous system white matter injury appear to be partially mediated by voltage-gated Ca(2+) channels. The presence of L- and N-type Ca(2+) channels on periaxonal astrocytes and oligodendrocytes suggests a role for these cells in post-traumatic axonal conduction failure.

Role of C-afferent fibres in the mechanism of action of sacral nerve root neuromodulation in chronic spinal cord injury

OBJECTIVE

To determine whether sacral root neuro-modulation (a promising therapeutic modality in patients with refractory voiding and storage problems) has its effect through the blockade of C-afferent fibres that form the afferent limb of a pathological reflex arc responsible for the dysfunction of bladder storage.

MATERIALS AND METHODS

The study comprised 39 female Sprague Dawley rats divided into three equal groups: normal controls (group 1); spinally transected at T10 (group 2); spinally transected and electrically stimulated bilaterally at S1 for 6 h daily (group 3). Three weeks after transection the rats were assessed using urodynamics; substance P, neurokinin A and calcitonin gene-related peptide (CGRP) were extracted from the dorsal root ganglia (DRG) of the L5 and L6 roots and quantified by radioimmunoassay.

RESULTS

Spinally transected rats developed urinary bladder hyper-reflexia after 3 weeks. This was associated with a significant increase in the neuropeptide content of the DRG of L6. Electrostimulation of S1 significantly decreased the neuropeptide content of L6. In contrast, transection and S1 neurostimulation did not affect the neuropeptide content of the L5 DRG, except for CGRP, which increased after spinal transection and decreased with neurostimulation.

CONCLUSIONS

In spinally transected rats, sacral root neurostimulation abolished bladder hyper-reflexia and attenuated the rise in neuropeptide content of the L6 DRG. These results suggest that the blockade of C-afferent fibre activity is one of the mechanisms of action of sacral root neuromodulation.