Methylprednisolone in Acute Spinal Cord Injury: A Tarnished Standard

Updated Review: The Steroid Controversy for Management of Spinal Cord Injury

BACKGROUND

Acute spinal cord injury (ASCI) is a devastating event that can have a profound impact on the lives of patients and their families. While no definitive medical treatment exists, the role of methylprednisolone (MP) in the management of ASCI and other spinal cord pathologies has been investigated in depth; however, its use remains contentious. While MP initially showed promise in the efficacy of ASCI treatment, more recent studies have questioned its use citing numerous systemic adverse effects. Pharmacologic treatments in this area are poorly understood due to the scarcity of knowledge surrounding the pathophysiology and heterogeneity of patients presenting with these conditions. Despite these shortcomings and due to the lack of alternative treatment options, MP is still widely used by physicians.

METHODS

We review prior and current literature on the use of MP treatment for ASCI patients with a discussion of novel drug delivery systems that have demonstrated the potential to improve MP's bioavailability at the site of injury while minimizing systemic side effects. In addition, current views on the role of MP and dexamethasone in metastatic spinal cord compression and postoperative infection are reviewed.

RESULTS

While some data support benefits in the use of steroids on spinal cord pathology, extensive research suggests at best limited effects and an unresolvable risk/benefit problem.

CONCLUSIONS

At present, evidence regarding use of dexamethasone for MSCC is contentious, especially regarding dose regiments. Ultimately, further investigation into the use of steroids is required to determine its utility in treating patients with spinal cord pathology.

Neuroinflammation after SCI: Current Insights and Therapeutic Potential of Intravenous Immunoglobulin

Traumatic spinal cord injury (SCI) elicits a complex cascade of cellular and molecular inflammatory events. Although certain aspects of the inflammatory response are essential to wound healing and repair, post-SCI inflammation is, on balance, thought to be detrimental to recovery by causing "bystander damage" and the spread of pathology into spared but vulnerable regions of the spinal cord. Much of the research to date has therefore focused on understanding the inflammatory drivers of secondary tissue loss after SCI, to define therapeutic targets and positively modulate this response. Numerous experimental studies have demonstrated that modulation of the inflammatory response to SCI can indeed lead to significant neuroprotection and improved recovery. However, it is now also recognized that broadscale immunosuppression is not necessarily beneficial and may even carry the risk of contributing to the development of serious adverse events. Immune modulation rather than suppression is therefore now considered a more promising approach to target harmful post-traumatic inflammation following a major neurotraumatic event such as SCI. One promising immunomodulatory agent is intravenous immunoglobulin (IVIG), a plasma product that contains mostly immunoglobulin G (IgG) from thousands of healthy donors. IVIG is currently already widely used to treat a range of autoimmune diseases, but recent studies have found that it also holds great promise for treating acute neurological conditions, including SCI. This review provides an overview of the inflammatory response to SCI, immunomodulatory approaches that are currently in clinical trials, proposed mechanisms of action for IVIG therapy, and the putative relevance of these in the context of neurotraumatic events.

Co-delivery of minocycline and paclitaxel from injectable hydrogel for treatment of spinal cord injury

Spinal cord injury (SCI) induces pathological and inflammatory responses that create an inhibitory environment at the site of trauma, resulting in axonal degeneration and functional disability. Combination therapies targeting multiple aspects of the injury, will likely be more effective than single therapies to facilitate tissue regeneration after SCI. In this study, we designed a dual-delivery system consisting of a neuroprotective drug, minocycline hydrochloride (MH), and a neuroregenerative drug, paclitaxel (PTX), to enhance tissue regeneration in a rat hemisection model of SCI. For this purpose, PTX-encapsulated poly (lactic-co-glycolic acid) PLGA microspheres along with MH were incorporated into the alginate hydrogel. A prolonged and sustained release of MH and PTX from the alginate hydrogel was obtained over eight weeks. The obtained hydrogels loaded with a combination of both drugs or each of them alone, along with the blank hydrogel (devoid of any drugs) were injected into the lesion site after SCI (at the acute phase). Histological assessments showed that the dual-drug treatment reduced inflammation after seven days. Moreover, a decrease in the scar tissue, as well as an increase in neuronal regeneration was observed after 28 days in rats treated with dual-drug delivery system. Over time, a fast and sustained functional improvement was achieved in animals that received dual-drug treatment compared with other experimental groups. This study provides a novel dual-drug delivery system that can be developed to test for a variety of SCI models or neurological disorders.

Epidural Corticosteroids, Lumbar Spinal Drainage, and Selective Hemodynamic Control for the Prevention of Spinal Cord Ischemia in Thoracoabdominal Endovascular Aortic Repair: A New Clinical Protocol

INTRODUCTION

In patients undergoing thoracoabdominal aorta repair, spinal cord ischemia (SCI) remains one of the most common and important complications resulting in transient paraparesis through to permanent flaccid paraplegia. In this manuscript, after a brief introduction to spinal cord ischemia complication and its prevention in thoracoabdominal endovascular aortic repair (TEVAR), we propose a new clinical protocol potentially able to prevent such complication.

METHODS

The proposed protocol suggests the use of high dosages of corticosteroids by epidural route, along with drainage of cerebrospinal fluid and controlled vascular hypertension, to reduce the incidence of SCI in TEVAR. Moreover, we paid particular attention to the control of the hemodynamic parameters to obtain adequate peripheral tissue perfusion (oxygen delivery), including in the spinal cord.

RESULTS

We applied this new protocol in 50 consecutive patients treated with TEVAR for thoracoabdominal aortic aneurysms (TAAs); 47 patients completed the procedure: 27 patients Crawford type I and 20 Crawford type II. Three patients died during surgery because of untreatable aneurysm rupture. The results show that in all patients there were no cases of SCI, after 5 days from TEVAR.

DISCUSSION

To the best of our knowledge, there are no clinical studies on the use of epidural corticosteroids in patients undergoing treatment of aortic syndrome (both in "open surgery" and endovascular aortic repair). This initial study on 50 consecutive patients has shown that the clinical protocol used could be of great interest to prevent one of the worse complications of TEVAR. Its limitations are the low number of patients studied till now, and the non-randomized protocol adopted. Further studies would be necessary.

CONCLUSION

Our experience and the results obtained with this new perioperative protocol with epidural corticosteroid and accurate hemodynamic control have been encouraging and it seems a valid proposal to be explored in future by well-structured prospective, randomized protocols.

IVIg attenuates complement and improves spinal cord injury outcomes in mice

Objective

Traumatic spinal cord injury (SCI) elicits immediate neural cell death, axonal damage, and disruption of the blood–spinal cord barrier, allowing circulating immune cells and blood proteins into the spinal parenchyma. The inflammatory response to SCI involves robust complement system activation, which contributes to secondary injury and impairs neurological recovery. This study aimed to determine whether intravenous immunoglobulin (IVIg), an FDA‐approved treatment for inflammatory conditions, can scavenge complement activation products and improve recovery from contusive SCI.

Methods

We used functional testing, noninvasive imaging, and detailed postmortem analysis to assess whether IVIg therapy is effective in a mouse model of severe contusive SCI.

Results

IVIg therapy at doses of 0.5–2 g/kg improved the functional and histopathological outcomes from SCI, conferring protection against lesion enlargement, demyelination, central canal dilation, and axonal degeneration. The benefits of IVIg were detectable through noninvasive diffusion tensor imaging (DTI), with IVIg treatment counteracting the progressive SCI‐induced increase in radial diffusivity (RD) in white matter. Diffusion indices significantly correlated with the functional performance of individual mice and accurately predicted the degree of myelin preservation. Further experiments revealed that IVIg therapy reduced the presence of complement activation products and phagocytically active macrophages at the lesion site, providing insight as to its mechanisms of action.

Interpretation

Our findings highlight the potential of using IVIg as an immunomodulatory treatment for SCI, and the value of DTI to assess tissue damage and screen for the efficacy of candidate intervention strategies in preclinical models of SCI, both quantitatively and noninvasively.

Safety and efficacy of corticosteroid use in neurologic trauma

Neurologic trauma, which consists of acute spinal cord injury and traumatic brain injury, is a leading cause of death and disability. In recent years, there have been improvements in the early recognition and prompt resuscitation of patients with neurologic trauma. However, there remain few pharmacologic treatments to reduce its secondary complications. Corticosteroids have been used in patients with neurologic trauma for more than 5 decades. Traditionally, their use has been to improve motor and sensory recovery. However, recently their utility to prevent and manage trauma-related pneumonia has been investigated. Given these new investigations, the purpose of this review article is to provide a comprehensive overview of the history and available scientific evidence surrounding the use of corticosteroids in neurologic trauma and caution against the use of these agents to prevent hospital-acquired pneumonia in this patient population.

MicroRNAs as potential therapeutics for treating spinal cord injury

MicroRNAs are a class of recently discovered, small non-coding RNAs that have been shown to play essential roles in a vast majority of biological processes. Very little is known about the role of microRNAs during spinal cord injury. This review summarizes the changes in expression levels of microRNAs after spinal cord injury. These aberrant changes suggest that microRNAs play an important role in inflammation, oxidative stress, apoptosis, glial scar formation and axonal regeneration. Given their small size and specificity of action, microRNAs could be potential therapeutics for treating spinal cord injury in the future. There are rapidly developing techniques for manipulating microRNA levels in animals; we review different chemical modification and delivery strategies. These may provide platforms for designing efficient microRNA delivery protocols for use in the clinic.

Current therapeutic strategies for inflammation following traumatic spinal cord injury

Damage from spinal cord injury occurs in two phases – the trauma of the initial mechanical insult and a secondary injury to nervous tissue spared by the primary insult. Apart from damage sustained as a result of direct trauma to the spinal cord, the post-traumatic inflammatory response contributes significantly to functional motor deficits exacerbated by the secondary injury. Attenuating the detrimental aspects of the inflammatory response is a promising strategy to potentially ameliorate the secondary injury, and promote significant functional recovery. This review details how the inflammatory component of secondary injury to the spinal cord can be treated currently and in the foreseeable future.

Transplantation of Cerebral Dopamine Neurotrophic Factor Transducted BMSCs in Contusion Spinal Cord Injury of Rats: Promotion of Nerve Regeneration by Alleviating Neuroinflammation

Traumatic spinal cord injury (SCI) causes neuron death and axonal damage resulting in functional motor and sensory loss, showing limited regeneration because of adverse microenvironment such as neuroinflammation and glial scarring. Currently, there is no effective therapy to treat SCI in clinical practice. Bone marrow-derived mesenchymal stem cells (BMSCs) are candidates for cell therapies but its effect is limited by neuroinflammation and adverse microenvironment in the injured spinal cord. In this study, we developed transgenic BMSCs overexpressing cerebral dopamine neurotrophic factor (CDNF), a secretory neurotrophic factor that showed potent effects on neuron protection, anti-inflammation, and sciatic nerve regeneration in previous studies. Our results showed that the transplantation of CDNF-BMSCs suppressed neuroinflammation and decreased the production of proinflammatory cytokines after SCI, resulting in the promotion of locomotor function and nerve regeneration of the injured spinal cord. This study presents a novel promising strategy for the treatment of spinal cord injury.

Ten common questions (and their answers) on medical futility

The term medical futility is frequently used when discussing complex clinical scenarios and throughout the medical, legal, and ethics literature. However, we propose that health care professionals and others often use this term inaccurately and imprecisely, without fully appreciating the powerful, often visceral, response that the term can evoke. This article introduces and answers 10 common questions regarding medical futility in an effort to define, clarify, and explore the implications of the term. We discuss multiple domains related to futility, including the biological, ethical, legal, societal, and financial considerations that have a bearing on definitions and actions. Finally, we encourage empathetic communication among clinicians, patients, and families and emphasize how dialogue that seeks an understanding of multiple points of view is critically important in preventing or attenuating conflict among the involved parties.

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

OBJECT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Anesthetic considerations in acute spinal cord trauma

Patients with actual or potential spinal cord injury (SCI) are frequently seen at adult trauma centers, and a large number of these patients require operative intervention. All polytrauma patients should be assumed to have an SCI until proven otherwise. Pre-hospital providers should take adequate measures to immobilize the spine for all trauma patients at the site of the accident. Stabilization of the spine facilitates the treatment of other major injuries both in and outside the hospital. The presiding goal of perioperative management is to prevent iatrogenic deterioration of existing injury and limit the development of secondary injury whilst providing overall organ support, which may be adversely affected by the injury. This review article explores the anesthetic implications of the patient with acute SCI. A comprehensive literature search of Medline, Embase, Cochrane database of systematic reviews, conference proceedings and internet sites for relevant literature was performed. Reference lists of relevant published articles were also examined. Searches were carried out in October 2010 and there were no restrictions by study design or country of origin. Publication date of included studies was limited to 1990–2010.

The current role of steroids in acute spinal cord injury

BACKGROUND

Acute spinal cord injury (ASCI) is a catastrophic event that can profoundly affect the trajectory of a patient's life. Debate continues over the pharmacologic management of ASCI, specifically, the widespread but controversial use of the steroid methylprednisolone (MP). Treatment efforts are impeded because of limitations in understanding of the pathobiology of ASCI and the difficulty in proving the efficacy of therapies.

METHODS

This review presents the pathophysiology of ASCI and the laboratory and clinical findings on the use of MP.

RESULTS

The use of MP remains a contentious issue in part because of the catastrophic nature of ASCI, the paucity of treatment options, and the legal ramifications. Although historical data on the use of MP in ASCI have been challenged, more recent studies have been used both to support and to oppose treatment of ASCI with steroids.

CONCLUSIONS

ASCI is a devastating event with a complex aftermath of secondary damaging processes that worsen the initial injury. Although the results of NASCIS (National Acute Spinal Cord Injury Study) II and III trials led to the widespread adoption of a high-dose MP regimen for patients treated within 8 hours of injury, subsequent studies have called into question the validity of NASCIS conclusions. Further evidence of the ineffectiveness of the MP protocol has led to declining confidence in the treatment over the last decade. At the present time, high-dose MP cannot be recommended as a standard of care, but it remains an option until supplanted by future evidence-based therapies.

Combination therapies

Spinal cord injury (SCI) has multiple consequences, ranging from molecular imbalances to glial scar formation to functional impairments. It is logical to think that a combination of single treatments implemented in the right order and at the right time will be required to repair the spinal cord. However, the single treatments that compose the combination therapy will need to be chosen with caution as many have multiple outcomes that may or may not be synergistic. Single treatments may also elicit unwanted side-effects and/or effects that would decrease the repair potential of other components and/or the entire combination therapy. In this chapter a number of single treatments are discussed with respect to their multiplicity of action. These include strategies to boost growth and survival (such as neurotrophins and cyclic AMP) and strategies to reduce inhibitory factors (such as antimyelin-associated growth inhibitors and digestion of glial scar-associated inhibitors). We also present an overview of combination therapies that have successfully or unsuccessfully been tested in the laboratory using animal models. To effectively design a combination therapy a number of considerations need to be made such as the nature and timing of the treatments and the method for delivery. This chapter discusses these issues as well as considerations related to chronic SCI and the logistics of bringing combination therapies to the clinic.

Critical care of traumatic spinal cord injury

Approximately 11 000 people suffer traumatic spinal cord injury (TSCI) in the United States, each year. TSCI incidences vary from 13.1 to 52.2 per million people and the mortality rates ranged from 3.1 to 17.5 per million people. This review examines the critical care of TSCI. The discussion will focus on primary and secondary mechanisms of injury, spine stabilization and immobilization, surgery, intensive care management, airway and respiratory management, cardiovascular complication management, venous thromboembolism, nutrition and glucose control, infection management, pressure ulcers and early rehabilitation, pharmacologic cord protection, and evolving treatment options including the use of pluripotent stem cells and hypothermia.

Clinical and experimental advances in regeneration of spinal cord injury

Spinal cord injury (SCI) is one of the major disabilities dealt with in clinical rehabilitation settings and is multifactorial in that the patients suffer from motor and sensory impairments as well as many other complications throughout their lifetimes. Many clinical trials have been documented during the last two decades to restore damaged spinal cords. However, only a few pharmacological therapies used in clinical settings which still have only limited effects on the regeneration, recovery speed, or retraining of the spinal cord. In this paper, we will introduce recent clinical trials, which performed pharmacological treatments and cell transplantations for patients with SCI, and evaluate recent in vivo studies for the regeneration of injured spinal cord, including stem-cell transplantation, application of neurotrophic factors and suppressor of inhibiting factors, development of biomaterial scaffolds and delivery systems, rehabilitation, and the combinations of these therapies to evaluate what can be appropriately applied in the future to the patients with SCI.

Neuroprotective efficacy of estrogen in experimental spinal cord injury in rats

Spinal cord injury (SCI) leads to neurological deficits and motor dysfunction. Methylprednisolone, the only drug used for treating SCI, renders limited neuroprotection and remains controversial. Estrogen is one of the most potent multiactive neuroprotective agents and it is currently under investigation in our laboratory for its efficacy in SCI. The present review briefly summarizes our earlier findings on the therapeutic potential of pharmacological/supraphysiological levels of estrogen in SCI and outlines our ongoing research, highlighting the efficacy of physiological levels of estrogen against neuronal injury, axonal degeneration, and gliosis and also the molecular mechanisms of such neuroprotection in experimental SCI. Furthermore, our ongoing studies designed to explore the different translational potential of estrogen therapy suggest that this multiactive steroid may act as an adjunct therapy to promote angiogenesis, thus enhancing the functional recovery following chronic SCI. Taken together, these studies confirm that estrogen is a potential therapeutic agent for treating SCI.

Physiological low dose of estrogen-protected neurons in experimental spinal cord injury

A protective role for estrogen against neurodegeneration and neurotrauma has received enormous attention in recent years, unraveling multiple facets and thus establishing this steroid as a multiactive neuroprotectant. The present study briefly reports our findings on the neuroprotective efficacy of physiologically relevant low doses of estrogen in experimental spinal cord injury (SCI) in rats. The current finding further corroborates our earlier results on efficacy of pharmacological/supraphysiological levels of estrogen in SCI and adds to the significance of conducting preclinical studies on estrogen efficacy in SCI.

Aquaporins in spinal cord injury: the janus face of aquaporin 4

Although malfunction of spinal cord water channels (aquaporins, AQP) likely contributes to severe disturbances in ion/water homeostasis after spinal cord injury (SCI), their roles are still poorly understood. Here we report and discuss the potential significance of changes in the AQP4 expression in human SCI that generates glial fibrillary acidic protein (GFAP)-labeled astrocytes devoid of AQP4, and GFAP-labeled astroglia that overexpress AQP4. We used a rat model of contusion SCI to study observed changes in human SCI. AQP4-negative astrocytes are likely generated during the process of SCI-induced replacement of lost astrocytes, but their origin and role in SCI remains to be investigated. We found that AQP4-overexpression is likely triggered by hypoxia. Our transcriptional profiling of injured rat cords suggests that elevated AQP4-mediated water influx accompanies increased uptake of chloride and potassium ions which represents a protective astrocytic reaction to hypoxia. However, unbalanced water intake also results in astrocytic swelling that can contribute to motor impairment, but likely only in milder injuries. In severe rat SCI, a low abundance of AQP4-overexpressing astrocytes was found during the motor recovery phase. Our results suggest that severe rat contusion SCI is a better model to analyze AQP4 functions after SCI. We found that AQP4 increases in the chronic post-injury phase are associated with the development of pain-like behavior in SCI rats, while possible mechanisms underlying pain development may involve astrocytic swelling-induced glutamate release. In contrast, the formation and size of fluid-filled cavities occurring later after SCI does not appear to be affected by the extent of increased AQP4 levels. Therefore, the effect of therapeutic interventions targeting AQP4 will depend not only on the time interval after SCI or animal models, but also on the balance between protective role of increased AQP4 in hypoxia and deleterious effects of ongoing astrocytic swelling.

Thoracic spine injury after a high-speed motor vehicle crash

In late October, a hospital-based flight team was activated at 9:30 pm for an approximately 30-year-old man involved in a high-speed motor vehicle crash into a tree. Per emergency medical services (EMS) documentation, flight service was requested for advanced airway management and rapid transport of the patient to a Level 1 trauma center. Ground transport was estimated at 60+ minutes, whereas actual flight time was less than 15 minutes. On the crew's arrival at the designated landing zone, they were escorted to an ambulance where a 100-kg man was immobilized on a stretcher. Because the landing area was at a remote location, the flight team did not witness the scene; however, the ground paramedic reported that the patient was the single-occupant driver of a small sedan. Given the extent of damage to the front and passenger side of the vehicle, it was determined that the patient was driving at a high rate of speed when he struck the tree. He required approximately 20 to 25 minutes of extrication. An empty bottle of zolpidem (Ambien) was found on the floor of the vehicle; the 30-day prescription had been filled approximately a week before the accident occurred.

Management of the unstable cervical spine: elective versus emergent cases

PURPOSE OF REVIEW

The present review focuses on similarities and discrepancies in the management of emergent and elective unstable cervical spine (C-spine) patients.

RECENT FINDINGS

During mobilization, lifting is superior to rolling in limiting spine movements. Before prone position surgery, the transfer of the patient on a rotating table is preferable to rolling. In trauma patients, helical computed tomography (CT) with sagittal reconstruction is the first choice for clearing the C-spine. In those patients, airway compromise may be related to hidden cervical edema or hematoma. Several devices can be of help in performing safe tracheal intubation in patients with limited neck movements, but awake fiberoptic intubation remains the safest procedure. The muscle relaxant antagonist sugammadex can improve safety for rapid sequence induction. It can rapidly reverse profound steroid-based neuromuscular blockade and allows avoidance of succinylcholine in this indication. Propofol anesthesia better prevents coughing upon emergence than inhaled anesthesia. Neuroprotection in cord-damaged patients is disappointing, and the controversy on the efficacy of high-dose methylprednisolone is not closed. Nevertheless, maintenance of homeostasis remains the cornerstone of neuroprotection.

SUMMARY

Subtle details differentiate the management of emergent and elective unstable C-spine patients. In both situations, the presence or the absence of a neurological insult governs the therapeutic strategy.

Therapeutic potential of melatonin in traumatic central nervous system injury

A vast literature extolling the benefits of melatonin has accumulated during the past four decades. Melatonin was previously considered of importance to seasonal reproduction and circadian rhythmicity. Currently, it appears to be a versatile anti-oxidative and anti-nitrosative agent, a molecule with immunomodulatory actions and profound oncostatic activity, and also to play a role as a potent neuroprotectant. Nowadays, melatonin is sold as a dietary supplement with differential availability as an over-the-counter aid in different countries. There is a widespread agreement that melatonin is nontoxic and safe considering its frequent, long-term usage by humans at both physiological and pharmacological doses with no reported side effects. Endeavors toward a designated drug status for melatonin may be enormously rewarding in clinics for treatment of several forms of neurotrauma where effective pharmacological intervention has not yet been attained. This mini review consolidates the data regarding the efficacy of melatonin as an unique neuroprotective agent in traumatic central nervous system (CNS) injuries. Well-documented actions of melatonin in combating traumatic CNS damage are compiled from various clinical and experimental studies. Research on traumatic brain injury and ischemia/reperfusion are briefly outlined here as they have been recently reviewed elsewhere, whereas the studies on different animal models of the experimental spinal cord injury have been extensively covered in this mini review for the first time.

Aquaporin-4 in brain and spinal cord oedema

Brain oedema is a major clinical problem produced by CNS diseases (e.g. stroke, brain tumour, brain abscess) and systemic diseases that secondarily affect the CNS (e.g. hyponatraemia, liver failure). The swollen brain is compressed against the surrounding dura and skull, which causes the intracranial pressure to rise, leading to brain ischaemia, herniation, and ultimately death. A water channel protein, aquaporin-4 (AQP4), is found in astrocyte foot processes (blood-brain border), the glia limitans (subarachnoid cerebrospinal fluid-brain border) and ependyma (ventricular cerebrospinal fluid-brain border). Experiments using mice lacking AQP4 or alpha syntrophin (which secondarily downregulate AQP4) showed that AQP4 facilitates oedema formation in diseases causing cytotoxic (cell swelling) oedema such as cerebral ischaemia, hyponatraemia and meningitis. In contrast, AQP4 facilitates oedema elimination in diseases causing vasogenic (vessel leak) oedema and therefore AQP4 deletion aggravates brain oedema produced by brain tumour and brain abscess. AQP4 is also important in spinal cord oedema. AQP4 deletion was associated with less cord oedema and improved outcome after compression spinal cord injury in mice. Here we consider the possible routes of oedema formation and elimination in the injured cord and speculate about the role of AQP4. Finally we discuss the role of AQP4 in neuromyelitis optica (NMO), an inflammatory demyelinating disease that produces oedema in the spinal cord and optic nerves. NMO patients have circulating AQP4 IgG autoantibody, which is now used for diagnosing NMO. We speculate how NMO-IgG might produce CNS inflammation, demyelination and oedema. Since AQP4 plays a key role in the pathogenesis of CNS oedema, we conclude that AQP4 inhibitors and activators may reduce CNS oedema in many diseases.

An injectable drug delivery platform for sustained combination therapy

We report the development of a series of physical hydrogel blends composed of hyaluronan (HA) and methyl cellulose (MC) designed for independent delivery of one or more drugs, from 1 to 28 days, for ultimate application in spinal cord injury repair strategies. To achieve a diversity of release profiles we exploit the combination of fast diffusion-controlled release of dissolved solutes from the HAMC itself and slow drug release from poly(lactide-co-glycolide) particles dispersed within the gel. Delivery from the composite hydrogels was demonstrated using the neuroprotective molecules NBQX and FGF-2, which were released for 1 and 4 days, respectively; the neuroregenerative molecules dbcAMP and EGF, and proteins alpha-chymotrypsin and IgG, which were released for 28 days. alpha-chymotrypsin and IgG were selected as model proteins for the clinically relevant neurotrophin-3 and anti-NogoA. Particle loaded hydrogels were significantly more stable than HAMC alone and drug release was longer and more linear than from particles alone. The composite hydrogels are minimally swelling and injectable through a 30 gauge/200 microm inner diameter needle at particle loads up to 15 wt.% and particle diameters up to 15 microm.