The posterior cervical transdural approach for retro-odontoid mass pseudotumor resection: report of three cases and discussion of the current literature

OBJECTIVE

The treatment of a retro-odontoid pseudotumor mass associated with severe spinal cord compression is challenging due to the complex regional anatomy. Here, we present an attractive treatment option involving a single-stage posterior transdural microsurgical resection followed by instrumented cervical reconstruction.

METHODS

We describe three patients presenting with clinical signs of cervical myelopathy and an imaging finding of mucoid and fibrous soft or semi-soft retro-odontoid pseudotumor mass with significant spinal cord compression at the C1/C2 level. Given the severity of the symptoms, surgical decompression was planned and fusion was necessitated by the severe degenerative osteoarthritis seen at the C1/C2 level with signs of instability. Using a standard posterior approach to the spine, a suboccipital decompression by craniectomy and laminectomy of C1, C2 and C3 was performed. The masses were visualized and confirmed with ultrasound imaging, and intraoperative neurosurgical monitoring was applied. The dura was then opened from the level of C0-C2. Exiting C2-C3 nerve roots were identified and protected throughout the procedure, and the dentate ligament was cut to facilitate access. Incision of the anterior dura provided easy access to the lesion for resection without any spinal cord retraction. Multiple intraoperative samples were sent to pathology for tissue diagnosis. The dura was closed with sutures and an overlay of fibrin sealant with collagen matrix sponge. The fusion procedures were performed using a standard occipital cervical plate and screws technique with contoured titanium rods.

CONCLUSIONS

The posterior cervical transdural approach is a safe alternative procedure for mucoid and fibrous soft or semi-soft retro-odontoid pseudotumor mass removal. Preoperative CT scan can evaluate tissue characteristics and distinguish between a soft or ossified mass in front of the spinal cord. Local anatomical conditions facilitate less bleeding and adhesions, together with less spinal cord traction, in the intradural space. Cranio-cervical and suboccipital stabilization can be easily and safely performed with this exposure.

Clinically Feasible Microstructural MRI to Quantify Cervical Spinal Cord Tissue Injury Using DTI, MT, and T2*-Weighted Imaging: Assessment of Normative Data and Reliability

BACKGROUND AND PURPOSE

DTI, magnetization transfer, T2*-weighted imaging, and cross-sectional area can quantify aspects of spinal cord microstructure. However, clinical adoption remains elusive due to complex acquisitions, cumbersome analysis, limited reliability, and wide ranges of normal values. We propose a simple multiparametric protocol with automated analysis and report normative data, analysis of confounding variables, and reliability.

MATERIALS AND METHODS

Forty healthy subjects underwent T2WI, DTI, magnetization transfer, and T2*WI at 3T in <35 minutes using standard hardware and pulse sequences. Cross-sectional area, fractional anisotropy, magnetization transfer ratio, and T2*WI WM/GM signal intensity ratio were calculated. Relationships between MR imaging metrics and age, sex, height, weight, cervical cord length, and rostrocaudal level were analyzed. Test-retest coefficient of variation measured reliability in 24 DTI, 17 magnetization transfer, and 16 T2*WI datasets. DTI with and without cardiac triggering was compared in 10 subjects.

RESULTS

T2*WI WM/GM showed lower intersubject coefficient of variation (3.5%) compared with magnetization transfer ratio (5.8%), fractional anisotropy (6.0%), and cross-sectional area (12.2%). Linear correction of cross-sectional area with cervical cord length, fractional anisotropy with age, and magnetization transfer ratio with age and height led to decreased coefficients of variation (4.8%, 5.4%, and 10.2%, respectively). Acceptable reliability was achieved for all metrics/levels (test-retest coefficient of variation < 5%), with T2*WI WM/GM comparing favorably with fractional anisotropy and magnetization transfer ratio. DTI with and without cardiac triggering showed no significant differences for fractional anisotropy and test-retest coefficient of variation.

CONCLUSIONS

Reliable multiparametric assessment of spinal cord microstructure is possible by using clinically suitable methods. These results establish normalization procedures and pave the way for clinical studies, with the potential for improving diagnostics, objectively monitoring disease progression, and predicting outcomes in spinal pathologies.

A Novel MRI Biomarker of Spinal Cord White Matter Injury: T2*-Weighted White Matter to Gray Matter Signal Intensity Ratio

BACKGROUND AND PURPOSE

T2*-weighted imaging provides sharp contrast between spinal cord GM and WM, allowing their segmentation and cross-sectional area measurement. Injured WM demonstrates T2*WI hyperintensity but requires normalization for quantitative use. We introduce T2*WI WM/GM signal-intensity ratio and compare it against cross-sectional area, the DTI metric fractional anisotropy, and magnetization transfer ratio in degenerative cervical myelopathy.

MATERIALS AND METHODS

Fifty-eight patients with degenerative cervical myelopathy and 40 healthy subjects underwent 3T MR imaging, covering C1-C7. Metrics were automatically extracted at maximally compressed and uncompressed rostral/caudal levels. Normalized metrics were compared with t tests, area under the curve, and logistic regression. Relationships with clinical measures were analyzed by using Pearson correlation and multiple linear regression.

RESULTS

The maximally compressed level cross-sectional area demonstrated superior differences (P = 1 × 10^-13), diagnostic accuracy (area under the curve = 0.890), and univariate correlation with the modified Japanese Orthopedic Association score (0.66). T2*WI WM/GM showed strong differences (rostral: P = 8 × 10^-7; maximally compressed level: P = 1 × 10^-11; caudal: P = 1 × 10^-4), correlations (modified Japanese Orthopedic Association score; rostral: -0.52; maximally compressed level: -0.59; caudal: -0.36), and diagnostic accuracy (rostral: 0.775; maximally compressed level: 0.860; caudal: 0.721), outperforming fractional anisotropy and magnetization transfer ratio in most comparisons and cross-sectional area at rostral/caudal levels. Rostral T2*WI WM/GM showed the strongest correlations with focal motor (-0.45) and sensory (-0.49) deficits and was the strongest independent predictor of the modified Japanese Orthopedic Association score (P = .01) and diagnosis (P = .02) in multivariate models (R² = 0.59, P = 8 × 10^-13; area under the curve = 0.954, respectively).

CONCLUSIONS

T2*WI WM/GM shows promise as a novel biomarker of WM injury. It detects damage in compressed and uncompressed regions and contributes substantially to multivariate models for diagnosis and correlation with impairment. Our multiparametric approach overcomes limitations of individual measures, having the potential to improve diagnostics, monitor progression, and predict outcomes.

Riluzole promotes motor and respiratory recovery associated with enhanced neuronal survival and function following high cervical spinal hemisection

Cervical spinal cord injury (SCI) can result in devastating functional deficits that involve the respiratory and hand function. The mammalian spinal cord has limited ability to regenerate and restore meaningful functional recovery following SCI. Riluzole, 2-amino-6-trifluoromethoxybenzothiazole, an anti-glutamatergic drug has been shown to reduce excitotoxicity and confer neuroprotection at the site of injury following experimental SCI. Based on promising preclinical studies, riluzole is currently under Phase III clinical trial for the treatment of SCI (ClinicalTrials.gov: NCT01597518). Riluzole's anti-glutamatergic role has the potential to regulate neuronal function and provide neuroprotection and influence glutamatergic connections distal to the initial injury leading to enhanced functional recovery following SCI. In order to investigate this novel role of riluzole we used a high cervical hemisection model of SCI, which interrupts all descending input to motoneurons innervating the ipsilateral forelimb and diaphragm muscles. Following C2 spinal cord hemisection, animals were placed into one of two groups: one group received riluzole (8 mg/kg) 1 h after injury and every 12 h thereafter for 7 days at 6 mg/kg, while the second group of injured rats received vehicle solution for the same duration of time. A third group of sham injured rats underwent a C2 laminectomy without hemisection and served as uninjured control rats. Interestingly, this study reports a significant loss of motoneurons within the cervical spinal cord caudal to C2 hemisection injury. Disruption of descending input led to a decrease in glutamatergic synapses and motoneurons caudal to the injury while riluzole treatment significantly limited this decline. Functionally, Hoffmann reflex recordings revealed an increase in the excitability of the remaining ipsilateral cervical motoneurons and significant improvements in skilled and unskilled forelimb function and respiratory motor function in the riluzole-treated animals. In conclusion, using a C2 hemisection injury model, this study provides novel evidence of motoneuron loss caudal to the injury and supports riluzole's capacity to promote neuronal preservation and function of neural network caudal to the SCI resulting in early and sustained functional improvements.

Impact of psychological characteristics in self-management in individuals with traumatic spinal cord injury

Study design:

Cross-sectional survey.

Objective:

To examine the association between psychological characteristics in self-management and probable depression status in individuals with a traumatic spinal cord injury (SCI).

Setting:

Community-dwelling individuals with traumatic SCI living across Canada.

Methods:

Individuals with SCI were recruited by email via the Rick Hansen Institute as well as an outpatient hospital spinal clinic. Data were collected by self-report using an online survey. Standardized questionnaires were embedded within a larger survey and included the Hospital Anxiety and Depression Scale (HADS), the short version of the Patient Activation Measure (PAM), the Moorong Self-Efficacy Scale (MSES) and the Pearlin-Schooler Mastery Scale (PMS).

Results:

Individuals with probable depression (n=25) had lower self-efficacy (67.9 vs 94.2, P<0.0001), mastery (18.9 vs 22.9, P<0.0001) and patient activation (60.4 vs 71.6, P<0.0001) as well as higher anxiety (9.0 vs 5.5, P<0.0001), compared with their non-depressed counterparts (n=75). A logistic regression determined that lower self-efficacy and mastery scores as well as less time since injury were associated with depression status (P=0.002; P=0.02 and P=0.02, respectively). Individuals with higher anxiety scores were almost 1.5 times more likely to be depressed, while older age was positively associated with depression status (P=0.016 and P=0.024, respectively).

Conclusion:

Interventions for depression in SCI, including a self-management program, should target factors such as self-efficacy and mastery, which could improve secondary medical complications and overall quality of life.

Characterizing the location of spinal and vertebral levels in the human cervical spinal cord

BACKGROUND AND PURPOSE

Advanced MR imaging techniques are critical to understanding the pathophysiology of conditions involving the spinal cord. We provide a novel, quantitative solution to map vertebral and spinal cord levels accounting for anatomic variability within the human spinal cord. For the first time, we report a population distribution of the segmental anatomy of the cervical spinal cord that has direct implications for the interpretation of advanced imaging studies most often conducted across groups of subjects.

MATERIALS AND METHODS

Twenty healthy volunteers underwent a T2-weighted, 3T MRI of the cervical spinal cord. Two experts marked the C3-C8 cervical nerve rootlets, C3-C7 vertebral bodies, and pontomedullary junction. A semiautomated algorithm was used to locate the centerline of the spinal cord and measure rostral-caudal distances from a fixed point in the brain stem, the pontomedullary junction, to each of the spinal rootlets and vertebral bodies. Distances to each location were compared across subjects. Six volunteers had 2 additional scans in neck flexion and extension to measure the effects of patient positioning in the scanner.

RESULTS

We demonstrated that substantial variation exists in the rostral-caudal position of spinal cord segments among individuals and that prior methods of predicting spinal segments are imprecise. We also show that neck flexion or extension has little effect on the relative location of vertebral-versus-spinal levels.

CONCLUSIONS

Accounting for spinal level variation is lacking in existing imaging studies. Future studies should account for this variation for accurate interpretation of the neuroanatomic origin of acquired MR signals.

The current state-of-the-art of spinal cord imaging: applications

A first-ever spinal cord imaging meeting was sponsored by the International Spinal Research Trust and the Wings for Life Foundation with the aim of identifying the current state-of-the-art of spinal cord imaging, the current greatest challenges, and greatest needs for future development. This meeting was attended by a small group of invited experts spanning all aspects of spinal cord imaging from basic research to clinical practice. The greatest current challenges for spinal cord imaging were identified as arising from the imaging environment itself; difficult imaging environment created by the bone surrounding the spinal canal, physiological motion of the cord and adjacent tissues, and small crosssectional dimensions of the spinal cord, exacerbated by metallic implants often present in injured patients. Challenges were also identified as a result of a lack of "critical mass" of researchers taking on the development of spinal cord imaging, affecting both the rate of progress in the field, and the demand for equipment and software to manufacturers to produce the necessary tools. Here we define the current state-of-the-art of spinal cord imaging, discuss the underlying theory and challenges, and present the evidence for the current and potential power of these methods. In two review papers (part I and part II), we propose that the challenges can be overcome with advances in methods, improving availability and effectiveness of methods, and linking existing researchers to create the necessary scientific and clinical network to advance the rate of progress and impact of the research.

The current state-of-the-art of spinal cord imaging: methods

A first-ever spinal cord imaging meeting was sponsored by the International Spinal Research Trust and the Wings for Life Foundation with the aim of identifying the current state-of-the-art of spinal cord imaging, the current greatest challenges, and greatest needs for future development. This meeting was attended by a small group of invited experts spanning all aspects of spinal cord imaging from basic research to clinical practice. The greatest current challenges for spinal cord imaging were identified as arising from the imaging environment itself; difficult imaging environment created by the bone surrounding the spinal canal, physiological motion of the cord and adjacent tissues, and small cross-sectional dimensions of the spinal cord, exacerbated by metallic implants often present in injured patients. Challenges were also identified as a result of a lack of "critical mass" of researchers taking on the development of spinal cord imaging, affecting both the rate of progress in the field, and the demand for equipment and software to manufacturers to produce the necessary tools. Here we define the current state-of-the-art of spinal cord imaging, discuss the underlying theory and challenges, and present the evidence for the current and potential power of these methods. In two review papers (part I and part II), we propose that the challenges can be overcome with advances in methods, improving availability and effectiveness of methods, and linking existing researchers to create the necessary scientific and clinical network to advance the rate of progress and impact of the research.

The immunological response to spinal cord injury: helpful or harmful?

The role of the immune response in spinal cord injury has become a frequent object of debate. Evidence exists to suggest that autoimmunity following neurotrauma can be either beneficial or detrimental to recovery. The following commentary examines the recent findings indicating that mice lacking mature B- and T-lymphocytes have improved behavioral and histological outcomes following thoracic spinal cord injury. These data, presented in the October issue of Experimental Neurology are discussed within the context of previous findings and differing viewpoints in the field of neuroimmunology. Limitations on the translation of immune modulation therapeutics, and clinical perspectives on their future potential are also examined.

Surgical treatment for acute spinal cord injury study pilot study #2: evaluation of protocol for decompressive surgery within 8 hours of injury

Acute spinal cord injury (SCI) is a major public health problem for which there is still only limited treatment available. The National Acute Spinal Cord Injury Study-2 (NASCIS-2) and -3 clinical trials demonstrated that the use of acute pharmacotherapy with methylprednisolone can attenuate the secondary injury cascade if administered within 8 hours of acute SCI. However, no trial has been performed to examine whether acute surgical decompressive procedures within this critical 8-hour time window can improve patients' neurological outcome. The purpose of the current prospective Surgical Treatment for Acute Spinal Cord Injury Study (STASCIS) pilot study was to determine the feasibility of obtaining a radiological diagnosis of spinal canal compromise of 25% or more and to perform spinal cord (C3-T1) decompressive procedures by 8 hours postinjury. One of the following three decompressive methods was used: 1) traction alone; 2) traction and surgery; or 3) surgery alone. Twenty-six patients from eight North American centers were entered into the study between 1996 and 1997. Significant difficulties were encountered in many centers in performing immediate magnetic resonance imaging examination in patients with acute SCI. Fewer than 10% of acute cervical SCI patients could be enrolled into this protocol mainly because the combination of the required time for rescue, resuscitation, transport, imaging study, and surgical preparation exceeded the 8-hour injury-to-decompressive surgery window. Eleven patients underwent decompressive procedures initially by being placed in traction at a mean time of 10.9 hours postinjury. Those patients not undergoing this procedure underwent decompressive surgery at a mean time of 40.1 hours. However, the surgical decompressive procedure was completed within 12 hours in seven patients. As a result of these findings, several major changes have been made to the STASCIS protocol for early decompressive therapy.

Management strategies to optimize clinical outcomes after acute traumatic spinal cord injury: integration of medical and surgical approaches

Although spinal cord injury (SCI) is approximately one-tenth as common as traumatic brain injury, its effects, at both a personal and societal level, are particularly devastating. At present, there is no single therapy that has demonstrated a uniform ability to improve neurological outcomes for SCI patients at long-term follow-up. In spite of this, the last 30 years have borne witness to numerous incremental advances within the field of spinal trauma including the incorporation of standardized neurological assessment tools, the completion of several large therapeutic efficacy trials and the development of modern day surgical classification systems. In this article we review the current evidence surrounding the medical and surgical management of SCI, as well as identify areas where future research is needed.

The Rick Hansen Spinal Cord Injury Registry (RHSCIR): a national patient-registry

STUDY DESIGN

Development of a prospective patient registry.

OBJECTIVE

To develop a patient registry for persons with traumatic spinal cord injuries (SCI), which can be used to answer research questions and improve patient outcomes.

SETTING

Nine provinces in Canada.

METHODS

The Rick Hansen Spinal Cord Injury Registry (RHSCIR) is part of the Translational Research Program of the Rick Hansen Institute. The launch of RHSCIR in 2004 heralded the initiation of the first nation-wide SCI patient registry within Canada. Currently, RHSCIR is being implemented in 14 cities located in 9 provinces, and there are over 1500 individuals who have sustained an acute traumatic SCI registered to date. Data are captured from the pre-hospital, acute and rehabilitation phases of care, and participants are followed in the community at 1, 2, 5 and then every 5 years post-injury.

RESULTS

During the development of RHSCIR, there were many challenges that were overcome in selecting data elements, establishing the governance structure, and creating a patient privacy and confidentiality framework across multiple provincial jurisdictions. The benefits of implementing a national registry are now being realized. The collection of an internationally standardized set of clinical information is helping inform clinicians of beneficial interventions and encouraging a shift towards evidence-based practices. Furthermore, through RHSCIR, a network is forming amongst SCI clinicians and researchers, which is fostering new collaborations and the launch of multi-center clinical trials.

CONCLUSIONS

For networks that are establishing SCI registries, the experiences and lessons learned in the development of RHSCIR may provide useful insights and guidance.

Myxopapillary ependymoma: correlation of clinical and imaging features with surgical resectability in a series with long-term follow-up

STUDY DESIGN

Retrospective case series.

OBJECTIVES

The objective of this study is to identify imaging and intraoperative characteristics that may predict surgical resection for myxopapillary ependymoma (MPE). The diffuse involvement in the conus-filum region makes complete resection challenging. The preoperative characteristics that may estimate the extent of resection has not been reported.

SETTING

Toronto, Canada.

METHODS

All MPE cases between 1972 and 2005 at a single institution were identified and reexamined by a neuropathologist. Neurological outcomes (Frankel scale), clinical features, operative findings, pre and postoperative imaging results were reviewed.

RESULTS

A total of 18 operations were performed on 15 MPE patients (8 females/7 males; age range: 18-71 years). Median postoperative follow-up was 56 months. Three patients (17%) developed tumor regrowth requiring reoperations. Preoperative magnetic resonance imaging (MRI; in 14/18 procedures) determined that tumors involved the conus in 70% of cases, which was significantly associated with intraoperative findings (P=0.02). Complete microsurgical resection was accomplished in 4 out of 7 cases where conus was not involved, but in only 1 out of 10 cases with conus involvement (P=0.056). The degree of conus involvement in one case was unclear. None of patients with total surgical resection developed recurrence. All patients survived at long-term follow-up.

CONCLUSION

Our series is the first to correlate MPE involvement to conus medullaris on preoperative MRI with intraoperative findings, and examine its significance on surgical resectability. This information could guide clinicians in preoperative planning and advising patients on treatment options and potential risks/benefits. MRI is very sensitive (100%) and moderately specific (67%) in detecting direct anatomical contact between conus and MPE tumors.

Management of anticoagulation following central nervous system hemorrhage in patients with high thromboembolic risk

SUMMARY BACKGROUND

Patients who present with central nervous system (CNS) hemorrhage while on anticoagulation (AC) for thromboembolic (TE) risk factors are a challenge to manage.

OBJECTIVE

We sought to inform decisions surrounding the timing and intensity of AC resumption by performing a systematic review.

METHODS

Three reviewers screened publications from Medline and EMBASE and extracted data. Hemorrhagic and TE adverse events that occurred subsequent to the index hemorrhage were recorded, as was their timing relative to presentation and covariates that might influence their occurrence.

RESULTS

Data were extracted from 63 publications detailing 492 patients; 7.7% of patients experienced hemorrhagic complications and 6.1% experienced TE complications. Hemorrhagic complications were more common within 72 h of presentation while TE complications were more common thereafter. Patients restarted on AC after 72 h were significantly more likely to have a TE complication (P = 0.006) and those restarted before 72 h were more likely to hemorrhage (P = 0.0727). Factors associated with re-hemorrhage included younger age, traumatic cause, subdural hematomas and failure to reverse AC. TE complications were more common in younger patients and those with spinal hemorrhage, multiple hemorrhages, and non-traumatic causes of the index hemorrhage. Re-initiation of AC at a lower intensity also significantly increased the risk of TE complications.

INTERPRETATION

Our results suggest that it may be prudent to re-initiate AC earlier than previously thought, with the timing and intensity modified based on predictors of TE and hemorrhagic complications. These findings must be explored in a prospective study because of limitations inherent to the analyzed studies.

Neural stem cells in regenerative medicine: bridging the gap

Repair of the chronically injured spinal presents with multiple challenges, including neuronal/axonal loss and demyelination as a result of primary injury (usually a physical insult), as well as secondary damage, which includes ischemia, inflammation, oxidative injury and glutamatergic toxicity. These processes cause neuronal loss, axonal disruption and lead to a cystic degeneration and an inhibitory astroglial scar. A promising therapeutic intervention for SCI is the use of neural stem cells. Cell replacement strategies using neural precursor cells (NPCs) and oligodendroglial precursor cells (OPCs) have been shown to replace lost/damaged cells, secrete trophic factors, regulate gliosis and scar formation, reduce cystic cavity size and axonal dieback, as well as to enhance plasticity, axonal elongation and neuroprotection. These progenitor cells can be obtained through a variety of sources, including adult neural tissue, embryonic blastocysts and adult somatic cells via induced pluripotent stem cell (iPSC) technology. The use of stem cell technology - especially autologous cell transplantation strategies - in regenerative therapy for SCI holds much promise; these therapies show high potential for clinical translation and for future disease treatment.

Optimal treatment for severe neurogenic bowel dysfunction after chronic spinal cord injury: a decision analysis

BACKGROUND

When conservative management fails in patients with chronic spinal cord injury (SCI) and neurogenic bowel dysfunction, clinicians have to choose from a variety of treatment options which include colostomy, ileostomy, Malone anterograde continence enema (MACE) and sacral anterior root stimulator (SARS) implantation. This study employed a decision analysis to examine the optimal treatment for bowel management of young individuals with chronic refractory constipation in the setting of chronic SCI.

METHODS

A decision analysis was created to compare the four surgical strategies using baseline analysis, one-way and two-way sensitivity analyses, 'worst scenario' and 'best scenario' sensitivity analyses, and probabilistic sensitivity analyses. Quality-adjusted life expectancy (QALE) was the primary outcome.

RESULTS

The baseline analysis indicated that patients who underwent the MACE procedure had the highest QALE value compared with the other interventions. Sensitivity analyses showed that these results were robust.

CONCLUSION

The MACE procedure may provide the best long-term outcome in terms of the probability of improving bowel function, reducing complication rates and the incidence of autonomic dysreflexia, and being congruent with patients' preferences. The analysis was sensitive to changes in assumptions about quality of life/utility, and thus the results could change if more specific estimates of utility became available.

The p75 neurotrophin receptor is essential for neuronal cell survival and improvement of functional recovery after spinal cord injury

The mechanisms initiating post-spinal cord injury (SCI) apoptotic cell death remain incompletely understood. The p75 neurotrophin receptor (p75(NTR)) has been shown to exert both pro-survival and pro-apoptotic effects on neural cells in vitro. While a previous study had shown that there is decreased oligodendrocyte apoptosis distal to a clean partial transection injury of the cord in mice with nonfunctional p75(NTR), most human spinal cord injuries do not involve partial transections but are rather due to compression/contusion injuries with significant perilesional ischemia. Therefore, we sought to examine the role of the p75(NTR) in a clinically relevant clip compression model of SCI in p75 null mice with an exon III mutation. Mice with a functional p75(NTR) had increased caspase-9 activation at 3 days after SCI in comparison to the functionally deficient p75(NTR) mice. However, at 7 days following SCI there was no difference in the activation of the effector caspases (caspase-3 and caspase-6) at the spinal cord lesion. Moreover, at 7 days after injury, there was increased terminal deoxynucleotidyl transferase-mediated dUTP nick-end (TUNEL) positive cell death at the injury site in the functionally deficient p75(NTR) mice. Using double labeling with TUNEL and cell specific markers we showed that the absence of p75(NTR) function increased the extent of neuronal but not oligodendroglial cell death at the injury site. This selective loss of neuronal cells after SCI was confirmed with a decrease in levels of microtubule-associated protein 2 in the p75 null mice. Furthermore, the wild-type animals had dramatically improved survival and enhanced locomotor recovery at 8 weeks after SCI when compared with the p75(NTR) null mice. Also at 8 weeks, there were significantly more neurons present at the injury site of wild-type mice when compared with p75 null mice. We conclude that the p75(NTR) receptor is integral to neuronal cell survival and endogenous reparative mechanisms after compressive/contusive SCI.

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP panel: spontaneous recovery after spinal cord injury and statistical power needed for therapeutic clinical trials

The International Campaign for Cures of Spinal Cord Injury Paralysis (ICCP) supported an international panel tasked with reviewing the methodology for clinical trials in spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the first of four papers. Here, we examine the spontaneous rate of recovery after SCI and resulting consequences for achieving statistically significant results in clinical trials. We have reanalysed data from the Sygen trial to provide some of this information. Almost all people living with SCI show some recovery of motor function below the initial spinal injury level. While the spontaneous recovery of motor function in patients with motor-complete SCI is fairly limited and predictable, recovery in incomplete SCI patients (American spinal injury Association impairment scale (AIS) C and AIS D) is both more substantial and highly variable. With motor complete lesions (AIS A/AIS B) the majority of functional return is within the zone of partial preservation, and may be sufficient to reclassify the injury level to a lower spinal level. The vast majority of recovery occurs in the first 3 months, but a small amount can persist for up to 18 months or longer. Some sensory recovery occurs after SCI, on roughly the same time course as motor recovery. Based on previous data of the magnitude of spontaneous recovery after SCI, as measured by changes in ASIA motor scores, power calculations suggest that the number of subjects required to achieve a significant result from a trial declines considerably as the start of the study is delayed after SCI. Trials of treatments that are most efficacious when given soon after injury will therefore, require larger patient numbers than trials of treatments that are effective at later time points. As AIS B patients show greater spontaneous recovery than AIS A patients, the number of AIS A patients requiring to be enrolled into a trial is lower. This factor will have to be balanced against the possibility that some treatments will be more effective in incomplete patients. Trials involving motor incomplete SCI patients, or trials where an accurate assessment of AIS grade cannot be made before the start of the trial, will require large subject numbers and/or better objective assessment methods.

Guidelines for the conduct of clinical trials for spinal cord injury (SCI) as developed by the ICCP panel: clinical trial outcome measures

An international panel reviewed the methodology for clinical trials of spinal cord injury (SCI), and provided recommendations for the valid conduct of future trials. This is the second of four papers. It examines clinical trial end points that have been used previously, reviews alternative outcome tools and identifies unmet needs for demonstrating the efficacy of an experimental intervention after SCI. The panel focused on outcome measures that are relevant to clinical trials of experimental cell-based and pharmaceutical drug treatments. Outcome measures are of three main classes: (1) those that provide an anatomical or neurological assessment for the connectivity of the spinal cord, (2) those that categorize a subject's functional ability to engage in activities of daily living, and (3) those that measure an individual's quality of life (QoL). The American Spinal Injury Association impairment scale forms the standard basis for measuring neurologic outcomes. Various electrophysiological measures and imaging tools are in development, which may provide more precise information on functional changes following treatment and/or the therapeutic action of experimental agents. When compared to appropriate controls, an improved functional outcome, in response to an experimental treatment, is the necessary goal of a clinical trial program. Several new functional outcome tools are being developed for measuring an individual's ability to engage in activities of daily living. Such clinical end points will need to be incorporated into Phase 2 and Phase 3 trials. QoL measures often do not correlate tightly with the above outcome tools, but may need to form part of Phase 3 trial measures.

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.