Effect of 4-aminopyridine and single-dose methylprednisolone on functional recovery after a chronic spinal cord injury

Ion channel blockers and spinal cord injury

The activation of a delayed secondary cascade of unsatisfactory cellular and molecular responses after a primary mechanical insult to the spinal cord causes the progressive degeneration of this structure. Disturbance of ionic homeostasis is part of the secondary injury process and plays an integral role in the early stage of spinal cord injury (SCI). The secondary pathology of SCI is complex and involves disturbance of the homeostasis of K(+) , Na(+) , and Ca(2+) . The effect of ion channel blockers on chronic SCI has also been proved. In this Mini-Review, we provide a comprehensive summary of the effects of ion channel blockers on the natural responses after SCI. Combination therapy is based on the roles of ions and disturbance of their homeostasis in SCI. The effects of ion channel blockers suggest that they have potential in the treatment of SCI, although the complexity of their effects shows that further knowledge is needed before they can be applied clinically.

Animal studies in spinal cord injury: a systematic review of methylprednisolone

The objective of this study was to examine whether animal studies can reliably be used to determine the usefulness of methylprednisolone (MP) and other treatments for acute spinal cord injury (SCI) in humans. This was achieved by performing a systematic review of animal studies on the effects of MP administration on the functional outcome of acute SCI. Data were extracted from the published articles relating to: outcome; MP dosing regimen; species/strain; number of animals; methodological quality; type of injury induction; use of anaesthesia; functional scale used; and duration of follow-up. Subgroup analyses were performed, based on species or strain, injury method, MP dosing regimen, functional outcome measured, and methodological quality. Sixty-two studies were included, which involved a wide variety of animal species and strains. Overall, beneficial effects of MP administration were obtained in 34% of the studies, no effects in 58%, and mixed results in 8%. The results were inconsistent both among and within species, even when attempts were made to detect any patterns in the results through subgroup analyses. The results of this study demonstrate the barriers to the accurate prediction from animal studies of the effectiveness of MP in the treatment of acute SCI in humans. This underscores the need for the development and implementation of validated testing methods.

Molecular targets in spinal cord injury

The spinal cord can be compared to a highway connecting the brain with the different body levels lying underneath, with the axons being the ultimate carriers of the electrical impulse. After spinal cord injury (SCI), many cells are lost because of the injury. To reconstitute function, damaged axons from surviving neurons have to grow through the lesion site to their initial targets. However, the territory they have to traverse has changed: the highway is full of inhibitory signals (myelin and scar components); the pavement itself has become bumpy (demyelination); and specialized cells are recruited to clear the way (inflammatory cells). Thus, actual strategies to treat spinal injuries aim at providing a permissive environment for regenerating axons and boosting the endogenous potential of axons to regenerate while limiting progression of secondary damage. Here we review some of the strategies currently under consideration to treat spinal injuries.

An Appraisal of Ongoing Experimental Procedures in Human Spinal Cord Injury

Clinicians and scientists in the field of spinal cord injury research and medicine are poised to begin translating promising new experimental findings into treatments for people. Advances in experimental regeneration research have led to several transplantation strategies that promote axonal regrowth and partial functional recovery in animal models of injury. In this review, we summarize current knowledge regarding various invasive experimental treatments that have been or are now being applied clinically. Various questions about the timeliness, safety, and benefits of the procedures are under discussion within the spinal cord injury (SCI) research community. We also describe guidelines for carrying out optimal clinical trials and efforts to establish specific international guidelines to translate preclinical treatment strategies into clinical trials in SCI. The clinical trial process and the role that clinical professionals have in advising individuals regarding participation in experimental procedures also is discussed.

The use of 4-aminopyridine (fampridine) in demyelinating disorders

4-Aminopyridine (4-AP or fampridine) is a potassium channel-blocking agent that has been shown to restore conduction in focally demyelinated axons. A sustained-release matrix tablet form of 4-AP (fampridine-SR) is currently undergoing multicenter clinical trials in patients with multiple sclerosis or chronic spinal cord injury. This review describes the pharmacology and mechanisms of action of 4-AP, its pharmacokinetics in human subjects, and the outcomes of clinical trials employing either immediate-release or sustained-release formulations of the drug. The randomized clinical trials that have been completed to date indicate that K+ channel blockade may prove to be a useful strategy for ameliorating central conduction deficits due to demyelination. Diverse neurological gains have been reported for both motor and sensory domains. At the present time, however, the clinical trials have not provided sufficiently robust or definitive evidence of efficacy to gain regulatory approval for the symptomatic management of patients with either multiple sclerosis or spinal cord injury.

Setting the stage for functional repair of spinal cord injuries: a cast of thousands

Here we review mechanisms and molecules that necessitate protection and oppose axonal growth in the injured spinal cord, representing not only a cast of villains but also a company of therapeutic targets, many of which have yet to be fully exploited. We next discuss recent progress in the fields of bridging, overcoming conduction block and rehabilitation after spinal cord injury (SCI), where several treatments in each category have entered the spotlight, and some are being tested clinically. Finally, studies that combine treatments targeting different aspects of SCI are reviewed. Although experiments applying some treatments in combination have been completed, auditions for each part in the much-sought combination therapy are ongoing, and performers must demonstrate robust anatomical regeneration and/or significant return of function in animal models before being considered for a lead role.

Efficacy of steroid treatment for sensory impairment after orthognathic surgery

PURPOSE

Steroid hormones are therapeutic for motor and/or sensory dysfunctions caused by nerve injury. However, the timing for giving such medicine is unclear. This study aimed to estimate the efficacy of steroid treatment and determine an appropriate start time after sensory impairment.

PATIENTS AND METHODS

Twenty-seven patients with sensory impairment who received orthognathic surgery were classified into groups called 1W (n = 6), 3W (n = 6), or 6W (n = 8) group on the basis of start time for steroid treatment, being 1 week, 3 weeks, or 6 weeks after surgery, respectively, and a no steroid treatment (NST) group (a control group) (n = 6) that did not receive treatment for 10 to 12 weeks after surgery. Sensory impairment was diagnosed if postoperative first week mechanical-touch threshold was over 4.0 as measured by Semmes aesthesiometer. Prednisolone treatment was administered orally to patients at 30 mg for 7 days, 15 mg for 4 days, and 5 mg for 3 days. Mechanical-touch threshold and thermal perceptions were compared before and after treatment.

RESULTS

At 1 week postoperatively, there were no significant differences in mechanical-touch threshold among the 4 groups (analysis of variance, P >.05). Changes in mechanical-touch threshold in the 1W group showed no significant improvement (analysis of variance, P >.05), but in the 3W and 6W groups, there were significant differences compared with the NST group (Dunns methods, P <.05).

CONCLUSIONS

Steroid treatment for sensory impairment after orthognathic surgery has the potential to accelerate recovery and it appears desirable to start treatment later than 1 week postoperatively.

Low micromolar concentrations of 4-aminopyridine facilitate fictive locomotion expressed by the rat spinal cord in vitro

Upregulating the operation of spinal locomotor networks is one mechanism to restore, at least partially, lesion-impaired locomotion. We investigated if the K+ channel blocker 4-aminopyridine (4-AP) could facilitate spinal locomotor networks in addition to its well-known effect on motor nerve conduction. Fictive locomotor patterns were recorded from ventral roots (VRs) of the isolated spinal cord of the neonatal rat. 4-AP (0.1-50 microM) produced synchronous VR oscillations which did not develop into fictive locomotion. These oscillations had network origin, required intact glutamatergic transmission and were probably amplified via electrotonic coupling because of their depression by the selective gap junction blocker carbenoxolone. 4-AP (5 microM) slightly increased input resistance of lumbar motoneurons without affecting their action or resting potentials. Dorsal root (DR) evoked synaptic responses were enhanced (217 +/- 65%) by 5 microM 4-AP without changes in axon conduction. 4-AP (5 microM) accelerated fictive locomotion induced by N-methyl-d-aspartate (NMDA) and serotonin (5-HT) without altering cycle amplitude and facilitated the onset of fictive locomotion in the presence of sub-threshold concentrations of NMDA and 5-HT. Furthermore, in the presence of 4-AP, weak DR stimuli, previously insufficient to activate locomotor patterns, generated alternating VR discharges. Thus, although 4-AP per se could not directly activate the locomotor network of the spinal cord, it could strongly facilitate the locomotor program initiated by neurochemicals or electrical stimuli. These data suggest that the reported improvement by 4-AP in locomotor activity of spinal-injury patients may include activation of locomotor networks when low concentrations of this drug are administered in coincidence with appropriate stimuli.

Methylprednisolone and interleukin-10 reduce gray matter damage in the contused Fischer rat thoracic spinal cord but do not improve functional outcome

The effects of two antiinflammatory and neuroprotective agents, methylprednisolone (MP) and interleukin-10 (IL-10), singly and in combination on tissue damage, axonal preservation and functional recovery were studied in the contused adult Fischer rat thoracic spinal cord 12 weeks after injury. MP (30 mg/kg at 5 min, and 2 and 4 h after injury) was administered intravenously and IL-10 (15 or 30 microg/kg at 30 min after injury), intraperitoneally. MP, IL-10, or the combination significantly reduced the volume of damaged tissue (including cavities) compared to control animals. The loss of spinal tissue (cavities) was reduced after treatment with MP alone or combined with IL-10, but not with IL-10 alone. The reduction in tissue damage was confined to spinal gray matter; at the level of the lesion epicenter, the thickness of the lateral white matter columns was similar in all groups. Retrograde tracing using fast blue revealed that the number of spared propriospinal and supraspinal projections was similar in all groups at 12 weeks after the contusion. The open-field BBB-test showed no significant difference in hindlimb locomotion between groups. Our results demonstrate that all tested antiinflammatory treatments significantly increase the volume of spared spinal gray matter 3 months after a moderate contusion of the Fischer rat thoracic spinal cord, but none of the treatments improved axonal preservation or functional recovery.

Comparison of the protection against neuronal injury by hypothalamic peptides and by dexamethasone

The comparative study has been carried out on hypothalamic neurohormone (proline-rich polypeptides-PRP) and synthetic glucocorticoid dexamethasone (DEX) protective properties at the systemic (i/m) administration. Both background and evoked electrical activity (on n.ischiadicus stimulation) of single neurons in the lumbo-sacral part (laminae II-VI and VII-VIII by Rexed) and field potentials (FP) of spinal cord were recorded during acute experiments on intact spinal rats, subjected to Vipera Raddei (VR) venom intoxication, and chronic spinal cord trauma (hemisection). The action of PRP was characterized by the pronounced activation of the background activity (BA) with adaptive effect, depending on dose and initial level of BA, by results of the statistical analysis. A high effect is received from comparatively small doses. For comparison it was used strong glucocorticoid DEX, possessing single-directed but less expressed excitative action on investigated spinal cord neurons. The initial increase of BA frequency with subsequent depression was the typical symptom of venom influence. A protective effect of preliminary PRP injection is revealed on the succeeding VR venom influence. Use of PRP and DEX causes the increase of reduced activity of neurons on the injury side of animals with spinal cord hemisection. It provides the possibility of the therapeutic utilization. It was revealed considerably more expressed PRP action on neurodegenerative process connected to spinal cord injury (in comparison with DEX). The influence of hormones was compared in identical conditions of experiments on non-injured (control) and injured sides. Taking into consideration revealed protection characteristic of PRP and also the ability of snake venom to stabilize and to prolong its action combined with these preparations, the assumption is made on prospective use of the specified combination in clinical practice.

Combined treatment with alphaMSH and methylprednisolone fails to improve functional recovery after spinal injury in the rat

To date, relatively little progress has been made in the treatment of spinal cord injury (SCI)-related neurological impairments. Until now, methylprednisolone (MP) is the only agent with clinically proven beneficial effect on functional outcome after SCI. Although the mechanism of action is not completely clear, experimental data point to protection against membrane peroxidation and edema reduction. The melanocortin melanotropin is known to improve axonal regeneration following sciatic nerve injury, and to stimulate corticospinal outgrowth after partial spinal cord transection. Recently, we showed that intrathecally administered alphaMSH had beneficial effects on functional recovery after experimental SCI. Since both drugs have shown their value in intervention studies after (experimental) spinal cord injury (ESCI), we decided to study the effects of combined treatment. Our results again showed that alphaMSH enhances functional recovery after ESCI in the rat and that MP, although not affecting functional recovery adversely by itself, abolished the effects observed with alphaMSH when combined. Our data, thus, suggest that the mechanism of action of MP interferes with that of alphaMSH.

Spinal cord injury research: review and synthesis

This article provides a substantive review and synthesis of major areas of emphasis in spinal cord injury (SCI) research. Comprehensive examination of the current status and future implications for SCI research includes consideration of investigations from the following arenas: epidemiology, functional classification and prediction, neurophysiologic testing, models of injury and recovery, psychosocial considerations, surgical strategies, animal laboratory research, economic implications, life expectancy, complication rates, gender differences, pharmacological management, and prevention. Synthesis of these research conclusions from a broad spectrum of laboratory, clinical, and scientific domains provides opportunity for improving SCI prevention, treatment, and adaptation.