Alterations in ionized and total blood magnesium after experimental traumatic brain injury: relationship to neurobehavioral outcome and neuroprotective efficacy of magnesium chloride

Initial Serum Magnesium Level Is Associated with Mortality Risk in Traumatic Brain Injury Patients

BACKGROUND

Electrolyte disorder is prevalent in traumatic brain injury (TBI) patients. This study is designed to explore the association between initial serum magnesium levels and mortality of TBI patients.

METHODS

TBI patients recorded in the Medical Information Mart for Intensive Care-III database were screened for this study. Logistic regression analysis was used to explore risk factors for mortality of included TBI patients. The restricted cubic spline (RCS) was applied to fit the correlation between initial serum magnesium level and mortality of TBI.

RESULTS

The 30-day mortality of included TBI patients was 17.0%. Patients with first-tertile and third-tertile serum magnesium levels had higher mortality than those of the second tertile. Univariate regression analysis showed that the serum magnesium level was not associated with mortality. Unadjusted RCS indicated the relationship between serum magnesium level mortality was U-shaped. After adjusting confounding effects, multivariate regression analysis presented that serum magnesium level was positively associated with mortality.

CONCLUSION

TBI patients with abnormally low or high levels of serum magnesium both have a higher incidence of mortality. At the same time, a higher initial serum magnesium level is independently associated with mortality in TBI patients. Physicians should pay attention to the clinical management of TBI patients, especially those with higher serum magnesium levels.

Early Plasma Magnesium in Near-Term and Term Infants with Neonatal Encephalopathy in the Context of Perinatal Asphyxia

Magnesium ions are implicated in brain functioning. The disruption of brain metabolism subsequent to a perinatal hypoxic-ischaemic insult may be reflected by plasma magnesium. Infants at 36 weeks after birth or later with neonatal encephalopathy and who were admitted to our neonatal unit from 2011 to 2019 were retrospectively included. The kinetics of plasma magnesium were investigated for the first 72 h of life and correlated to the Barkovich MRI score. Among the 125 infants who met the inclusion criteria, 45 patients (36%) had moderate to severe brain lesions on neonatal MRI. Plasma magnesium values were not strongly associated with the severity of clinical encephalopathy, initial EEG background and brain lesions. Intriguingly, higher plasma magnesium values during the 0−6 h period were linked to the presence of brain injuries that predominated within the white matter (p < 0.001) and to the requirement of cardiac resuscitation in the delivery room (p = 0.001). The occurrence of seizures was associated with a lower mean magnesium value around the 24th hour of life (p = 0.005). This study supports that neonatal encephalopathy is a complex and multifactorial condition. Plasma magnesium could help to better identify the subtypes of neonatal encephalopathy. Further studies are needed to confirm these results in this prospect.

Alterations of Serum Magnesium Concentration in Animal Models of Seizures and Epilepsy—The Effects of Treatment with a GPR39 Agonist and Knockout of the Gpr39 Gene

Several ligands have been proposed for the GPR39 receptor, including the element zinc. The relationship between GPR39 and magnesium homeostasis has not yet been examined, nor has such a relationship in the context of seizures/epilepsy. We used samples from mice that were treated with an agonist of the GPR39 receptor (TC-G 1008) and underwent acute seizures (maximal electroshock (MES)- or 6-hertz-induced seizures) or a chronic, pentylenetetrazole (PTZ)-induced kindling model of epilepsy. MES seizures and PTZ kindling, unlike 6 Hz seizures, increased serum magnesium concentration. In turn, Gpr39-KO mice that underwent PTZ kindling displayed decreased concentrations of this element in serum, compared to WT mice subjected to this procedure. However, the levels of expression of TRPM7 and SlC41A1 proteins—which are responsible for magnesium transport into and out of cells, respectively—did not differ in the hippocampus between Gpr39-KO and WT mice. Furthermore, laser ablation inductively coupled plasma mass spectrometry applied to hippocampal slices did not reveal differences in magnesium levels between the groups. These data show the relationship between magnesium homeostasis and certain types of acute or chronic seizures (MES seizures or PTZ kindling, respectively), but do not explicitly support the role of GPR39 in mediating magnesium balance in the hippocampus in the latter model. However, decreased expression of TRPM7 and increased expression of SLC41A1—which were observed in the hippocampi of Gpr39-KO mice treated with TC-G 1008, in comparison to WT mice that received the same treatment—implicitly support the link between GPR39 and hippocampal magnesium homeostasis.

Dynamic changes in c-Fos and NF-κB gene expression and Ca, Fe, Cu, Zn and Mg content due to brain injury in irradiated rats

BACKGROUND

This study aims to investigate the dynamic changes of c-Fos and NF-κB expression, and to evaluate the Ca, Fe, Cu, Zn and Mg content of hippocampal tissues in rat brains injured by 20 Gy of electron beam irradiation.

MATERIALS AND METHODS

A single dose of 5 MeV is administered to the whole brains of rats to establish animal model of radiation-induced brain injury (RBI). Hematoxylin and eosin staining is performed to observe the pathological changes in brain microvascular endothelial cells. Quantitative reverse transcription-PCR and western blotting assays are utilized to test c-Fos and NF-κB gene expression levels in brain tissue. Inductively coupled plasma-atomic emission spectrometry is leveraged to detect the Ca, Fe, Cu, Zn and Mg contents of the hippocampi.

RESULTS

The c-Fos and NF-κB gene expression levels in protective group are lower than those in the irradiated group after MgSO4 treatment. In the irradiated group, Ca content at several time points and Fe content on days 1, 3 and 7 are higher than those in the blank group. Additionally, in the irradiated group, Cu and Zn contents on days 1, 7, 14 and 60 are less than those in the blank group.

CONCLUSION

In RBI model, adding Mg2+ may relieve RBI. The protective mechanisms of Mg2+ in the hippocampi from a variety of brain activity indicators including the c-Fos and NF-κB genes.

Magnesium administration after experimental traumatic brain injury improves decision-making skills

After sustaining a traumatic brain injury (TBI), a person's ability to make daily decisions can be affected. Simple tasks such as, deciding what to wear are no longer effortless choices, but are instead difficult decisions. This study explored the use of a discrimination task with a magnesium treatment in order to examine how decision-making skills are affected after TBI and if the treatment helped to attenuate cognitive and motor impairments. Thirty-one male rats were separated into MAG/TBI, VEH/TBI, or VEH/Sham groups. Pre-TBI, rats were trained to dig in the sand for a reinforcer. After establishment of consistent digging behavior rats received a bilateral frontal cortex injury. Rats received either an i.p. injection of 2 mmol/kg magnesium chloride or control at 4, 24, 72 h post-surgery. Dig task testing began 7 days post-injury, lasting for 4 weeks. The discriminations included two scent pairings; basil (baited) versus coffee then the reversal and then cocoa (baited) versus cumin then the reversal. The results indicated that the magnesium treatment was successful at attenuating cognitive and motor deficits after TBI. The results also indicated that the dig task is a sufficient operant conditioning task in the assessment of frontal functioning after TBI.

Serum Magnesium as a Marker of Neurological Outcome in Severe Traumatic Brain Injury Patients

Hypomagnesemia is postulated as one of the important determinants of outcome following traumatic brain injury (TBI) through its effect on secondary injuries to neurons.

Magnesium sulfate for acute traumatic brain injury

BACKGROUND

The purpose of this systematic review was to evaluate the effect of magnesium sulfate in the treatment of acute traumatic brain injury.

MATERIALS AND METHODS

A systematic search of ClinicalTrials.gov, the Cochrane Library database, EMBASE, MEDLINE, Web of Science, and the World Health Organization trial registry, plus manual searches of gray literature, was undertaken in April 2013. Two reviewers independently extracted the data with a predefined data extraction form. RevMan 5 software was used to synthesize data and calculate the risk ratio for mortality with the 95% confidence interval. For the Glasgow Outcome Scale and posttreatment Glasgow Coma Scale data, the weighted mean difference was calculated with the 95% confidence interval.

RESULTS

A total of 8 randomized controlled trials with a total of 786 patients were included. Meta-analysis showed that there was no significant difference between the groups for mortality. The Glasgow Outcome Scale of the treatment group was higher than that of the control group, although the significance was borderline. The Glasgow Coma Scale score change posttreatment was significantly higher than that of the control.

CONCLUSIONS

The present meta-analysis of existing randomized controlled trials does not identify a significant beneficial effect in the mortality of traumatic brain injury patients; however, it suggests that magnesium sulfate shows a tendency to improve the Glasgow Outcome Scale and Glasgow Coma Scale scores, which is a promising result for traumatic brain injury therapy. Further effort is necessary to explore which subgroup of traumatic brain injury patients could benefit from magnesium sulfate.

Networks of neuroinjury semantic predications to identify biomarkers for mild traumatic brain injury

Objective

Mild traumatic brain injury (mTBI) has high prevalence in the military, among athletes, and in the general population worldwide (largely due to falls). Consequences can include a range of neuropsychological disorders. Unfortunately, such neural injury often goes undiagnosed due to the difficulty in identifying symptoms, so the discovery of an effective biomarker would greatly assist diagnosis; however, no single biomarker has been identified. We identify several body substances as potential components of a panel of biomarkers to support the diagnosis of mild traumatic brain injury.

Methods

Our approach to diagnostic biomarker discovery combines ideas and techniques from systems medicine, natural language processing, and graph theory. We create a molecular interaction network that represents neural injury and is composed of relationships automatically extracted from the literature. We retrieve citations related to neurological injury and extract relationships (semantic predications) that contain potential biomarkers. After linking all relationships together to create a network representing neural injury, we filter the network by relationship frequency and concept connectivity to reduce the set to a manageable size of higher interest substances.

Results

99,437 relevant citations yielded 26,441 unique relations. 18,085 of these contained a potential biomarker as subject or object with a total of 6246 unique concepts. After filtering by graph metrics, the set was reduced to 1021 relationships with 49 unique concepts, including 17 potential biomarkers.

Conclusion

We created a network of relationships containing substances derived from 99,437 citations and filtered using graph metrics to provide a set of 17 potential biomarkers. We discuss the interaction of several of these (glutamate, glucose, and lactate) as the basis for more effective diagnosis than is currently possible. This method provides an opportunity to focus the effort of wet bench research on those substances with the highest potential as biomarkers for mTBI.

Impact of pharmacological treatments on outcome in adult rodents after traumatic brain injury: a meta-analysis

Pharmacological treatments have been widely investigated in pre-clinical animal trials to evaluate their usefulness in reducing cognitive, behavioural and motor problems after traumatic brain injury (TBI). However, the relative efficacy of these agents has yet to be evaluated, making it difficult to assess the strength of evidence for their use in a clinical population. A meta-analytic review of research (1980-2009) was therefore conducted to examine the impact of pharmacological treatments administered to adult male rodents after experimental TBI on cognitive, behavioural, and motor outcome. The PubMed and PsycInfo databases were searched using 35 terms. Weighted Cohen's d effect sizes, percent overlap, Fail-Safe N statistics and confidence intervals were calculated for each treatment. In total, 91 treatments were evaluated in 223 pre-clinical trials, comprising 5988 rodents. Treatments that were investigated by multiple studies and showed large and significant treatment effects were of greatest interest. Of the 16 treatments that were efficacious, six improved cognition, 10 improved motor function and no treatment improved behaviour (depression/anxiety, aggression, zoosocial behaviour). Treatment benefits were found across a range of TBI models. Drug dosage and treatment interval impacted on treatment effects.

Animal modelling of traumatic brain injury in preclinical drug development: where do we go from here?

Traumatic brain injury (TBI) is the leading cause of death and disability in young adults. Survivors of TBI frequently suffer from long-term personality changes and deficits in cognitive and motor performance, urgently calling for novel pharmacological treatment options. To date, all clinical trials evaluating neuroprotective compounds have failed in demonstrating clinical efficacy in cohorts of severely injured TBI patients. The purpose of the present review is to describe the utility of animal models of TBI for preclinical evaluation of pharmacological compounds. No single animal model can adequately mimic all aspects of human TBI owing to the heterogeneity of clinical TBI. To successfully develop compounds for clinical TBI, a thorough evaluation in several TBI models and injury severities is crucial. Additionally, brain pharmacokinetics and the time window must be carefully evaluated. Although the search for a single-compound, 'silver bullet' therapy is ongoing, a combination of drugs targeting various aspects of neuroprotection, neuroinflammation and regeneration may be needed. In summary, finding drugs and prove clinical efficacy in TBI is a major challenge ahead for the research community and the drug industry. For a successful translation of basic science knowledge to the clinic to occur we believe that a further refinement of animal models and functional outcome methods is important. In the clinical setting, improved patient classification, more homogenous patient cohorts in clinical trials, standardized treatment strategies, improved central nervous system drug delivery systems and monitoring of target drug levels and drug effects is warranted.

Use of magnesium in traumatic brain injury

Depletion of magnesium is observed in animal brain and in human blood after brain injury. Treatment with magnesium attenuates the pathological and behavioral changes in rats with brain injury; however, the therapeutic effect of magnesium has not been consistently observed in humans with traumatic brain injury (TBI). Secondary brain insults are observed in patients with brain injury, which adversely affect clinical outcome. Systemic administration studies in rats have shown that magnesium enters the brain; however, inducing hypermagnesemia in humans did not concomitantly increase magnesium levels in the CSF. We hypothesize that the neuroprotective effects of magnesium in TBI patients could be observed by increasing its brain bioavailability with mannitol. Here, we review the role of magnesium in brain injury, preclinical studies in brain injury, clinical safety and efficacy studies in TBI patients, brain bioavailability studies in rat, and pharmacokinetic studies in humans with brain injury. Neurodegeneration after brain injury involves multiple biochemical pathways. Treatment with a single agent has often resulted in poor efficacy at a safe dose or toxicity at a therapeutic dose. A successful neuroprotective therapy needs to be aimed at homeostatic control of these pathways with multiple agents. Other pharmacological agents, such as dexanabinol and progesterone, and physiological interventions, with hypothermia and hyperoxia, have been studied for the treatment of brain injury. Treatment with magnesium and hypothermia has shown favorable outcome in rats with cerebral ischemia. We conclude that coadministration of magnesium and mannitol with pharmacological and physiological agents could be an effective neuroprotective regimen for the treatment of TBI.

Magnesium for acute traumatic brain injury

BACKGROUND

Acute traumatic brain injury is a leading cause of death and disability in young adults. Numerous pharmacological and non-pharmacological tools have been investigated and considered as potential mechanisms for improving neurological outcome. Magnesium has been considered as one of these potential therapeutic tools because of its activity on NMDA-receptors, calcium channels and neuron membranes. Animal studies have indicated a beneficial effect of magnesium on outcome after brain injury, but its efficacy in humans is unknown.

OBJECTIVES

To quantify the effect of magnesium administration on mortality and morbidity in patients with acute traumatic brain injury.

SEARCH STRATEGY

We searched the Cochrane Injuries Group's specialised register, Cochrane Central Register of Controlled Trials, CENTRAL (The Cochrane Library issue 2, 2008), MEDLINE (and PubMed to 28 May, 2008: last 60 days), EMBASE, National Research Register, Current Controlled Trials, SIGLE, LILACS, and Zetoc. Searches were initially conducted in July 2005. The latest search was conducted in May 2008.

SELECTION CRITERIA

We included all randomized controlled trials comparing any magnesium salt with no magnesium or with placebo, in patients following acute traumatic brain injury.

DATA COLLECTION AND ANALYSIS

Two authors independently screened search results and assessed the full texts of potentially relevant studies for inclusion. Data were extracted and methodological quality was examined.

MAIN RESULTS

Four studies met the inclusion criteria; one of which is an ongoing study. Data from three studies were included in the analysis. Data on mortality were only available in one study; RR 1.48 [1.00, 2.19], Test for overall effect: Z = 1.96 (P = 0.05). Glasgow Outcome Score at six months was described in the three studies. The Mean Difference = 0.02 (95% CI -0.38 to 0.041), Test for overall effect: Z = 0.08 (P = 0.94).

AUTHORS' CONCLUSIONS

There is currently no evidence to support the use of magnesium salts in patients with acute traumatic brain injury.

Serum and Cerebrospinal Fluid Magnesium in Severe Traumatic Brain Injury Outcome

Serum magnesium concentration has a neuroprotective effect in experimental models of traumatic brain injury (TBI). This study was designed to assess the relationship between initial serum magnesium, cerebrospinal fluid (CSF) magnesium, neurological outcome and the efficacy of magnesium replacement therapy (MgSO4). A retrospective analysis was performed on a prospectively collected dataset from 216 patients admitted during 1996-2006 to the University of Pittsburgh Medical Center with severe TBI. Admission serum and CSF magnesium were dichotomized into low and normal magnesium concentration groups for serum and normal and high concentration groups for CSF. A logistic-regression analysis was performed with 6-month Glasgow Outcome Scale (GOS) scores as outcome variable. The outcome of a subset of 31 patients who presented with low serum magnesium and who were rapidly corrected within 24 h of admission was also analyzed. Low initial serum magnesium was measured in 56.67% of all patients. Patients with an initial serum magnesium of <1.3 mEq/L were 2.37 times more likely to have a poor outcome (CI: 1.18-4.78, p = 0.016). The prognostic significance of depressed serum magnesium remained, even in patients whose serum magnesium levels were corrected within 24 h (OR = 11.03, CI: 1.87-68.14, p = 0.008). Patients with an initial high CSF magnesium were 7.63 more likely to have a poor outcome (p = 0.05). Elevated CSF magnesium correlated with depressed serum magnesium only in patients with poor outcome (p = 0.013). Patients with low serum magnesium and high CSF magnesium are most likely to have poor outcome after severe TBI. Rapid correction of serum magnesium levels does not reverse the prognostic value of these markers.

Effects of estradiol on cognition and hippocampal pathology after lateral fluid percussion brain injury in female rats

Studies involving animal models of acute central nervous system (CNS) stroke and trauma strongly indicate that sex and/or hormonal status are important determinants of outcome after brain injury. The present study was undertaken to examine the ability of estradiol to protect hippocampal neurons from lateral fluid percussion brain injury. Sprague-Dawley female rats (211-285 g; n = 119) were ovariectomized, and a subset (n = 66) were implanted with 17beta-estradiol pellets to provide near physiological levels of estradiol. Animals were subjected to lateral fluid percussion brain injury or sham injury 1 week later. Activation of caspase-3 (n = 26) and TUNEL staining (n = 21) were assessed at 3 and 12 h after injury, respectively, in surviving control and estradiol-treated animals. Memory retention was examined using a Morris water maze test in a separate subset of animals (n = 43) at 8 days after injury. Activated caspase-3 and TUNEL staining were observed in the dentate hilus, granule cell layer, and CA3 regions in all injured rats, indicative of selective hippocampal cell apoptosis in the acute posttraumatic period. Estradiol did not significantly alter the number of hippocampal neurons exhibiting caspase-3 activity or TUNEL staining. Brain injury impaired cognitive ability, assessed at 1 week post-injury (p < 0.001). However, estradiol at physiological levels did not significantly alter injury-induced loss of memory. These data indicate that estradiol at physiological levels does not ameliorate trauma-induced hippocampal injury or cognitive deficits in ovariectomized female rats.

Magnesium for acute traumatic brain injury

BACKGROUND

Acute traumatic brain injury is a leading cause of death and disability in young adults. Magnesium had been considered as a potential therapeutic tool because of its activity on NMDA-receptors, calcium channels and neuron membranes. Animals studies have indicated a beneficial effect of magnesium on outcome after brain injury, but its efficacy in humans is unknown.

OBJECTIVES

To quantify the effect of magnesium administration on mortality and morbidity in patients with acute traumatic brain injury.

SEARCH STRATEGY

We searched the Cochrane Injuries Group's specialised register, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, National Research Register, Current Controlled Trials, SIGLE, LILACS, Zetoc. The searches were conducted in July 2005.

SELECTION CRITERIA

We included all randomized controlled trials comparing any magnesium salt with no magnesium or with placebo, in patients following acute traumatic brain injury.

DATA COLLECTION AND ANALYSIS

Two authors independently screened search results and assessed the full texts of potentially relevant studies for inclusion. Data were extracted and methodological quality was examined.

MAIN RESULTS

Three studies met the inclusion criteria, one of which is an ongoing study. Two studies were included in the analysis. No data on mortality were available. For Glasgow Outcome Score at six months the pooled WMD = 0.55 (95% CI -0.15 to 1.26), P = 0.12.

AUTHORS' CONCLUSIONS

There is currently no evidence to support the use of magnesium salts in patients with acute traumatic brain injury.

Ionized magnesium in the cerebrospinal fluid of patients with head injuries

BACKGROUND

In head injury patients, a decrease in the serum ionized magnesium (iMg) concentration is considered to be related to the severity of the injury, however, this phenomenon is still not completely understood. The cerebrospinal fluid (CSF) iMg concentration has not been well documented under such conditions and, moreover, its normal value has not yet been established. We hereby intended to investigate the role of the iMg concentration and other parameters in both the serum and CSF of head injury patients and identify any relationship with other parameters.

MATERIALS AND METHODS

The subjects consisted of head injury patients without any other serious injuries. Ten healthy volunteers were selected as control subjects. Arterial blood and CSF specimens were simultaneously obtained and measured. We measured the Glasgow Coma Scale scores (GCS), the intracranial pressure (ICP), pH, po2, pco2, sodium, potassium, iCa, iMg, glucose, lactate, urea nitrogen. All data are expressed as the mean+/-SD and the units of iMg and iCa (corrected under pH 7.40) are given in mmol/L.

RESULTS

In the healthy subjects, the iMg concentration in the serum/CSF was 0.48 +/- 0.02 / 0.66 +/- 0.14, and iCa was 1.14 +/- 0.05 / 0.94 +/- 0.07. The GCS of the 15 head injury subjects at examination was 8.7 +/- 4.5. When the subjects were divided into 3 groups according to the GCS level (3 and 4, 5-8, and > or =9) at the time of examination, the serum iMg concentration was thus found to be related to the severity of injury based on the GCS level (p = 0.028), but not the CSF iMg concentration (p = 0.89). No relationship was observed between the iMg concentration in the serum and CSF when all specimens were compared, but an extremely close correlation was seen in the group with GCS 3 and 4 (p < 0.0001, r = 0.995), although no such correlation was seen in the other 2 groups (p = 0.12, r = -0.56 in the group with GCS 5-8, and p = 0.26, r = -0.35 in the group with GCS > or = 9). There was a significant correlation between the serum iMg and iCa (p = 0.0093, r = 0.47), and also between the CSF iMg and iCa concentrations (p < 0.0001, r = 0.67).

CONCLUSION

The serum iMg concentration has been suggested to possibly affect the neurologic state through CSF iMg in patients with the most severe head injury. In patients with moderate or mild head injuries, however, the ionized magnesium concentration is also probably associated with the degree of neurologic deficit based on the ionized calcium level. The CSF and serum ionized magnesium dissociation may thus result from the slow movement of ionized magnesium through the blood brain barrier.

Lateral fluid percussion brain injury: a 15-year review and evaluation

This article comprehensively reviews the lateral fluid percussion (LFP) model of traumatic brain injury (TBI) in small animal species with particular emphasis on its validity, clinical relevance and reliability. The LFP model, initially described in 1989, has become the most extensively utilized animal model of TBI (to date, 232 PubMed citations), producing both focal and diffuse (mixed) brain injury. Despite subtle variations in injury parameters between laboratories, universal findings are evident across studies, including histological, physiological, metabolic, and behavioral changes that serve to increase the reliability of the model. Moreover, demonstrable histological damage and severity-dependent behavioral deficits, which partially recover over time, validate LFP as a clinically-relevant model of human TBI. The LFP model, also has been used extensively to evaluate potential therapeutic interventions, including resuscitation, pharmacologic therapies, transplantation, and other neuroprotective and neuroregenerative strategies. Although a number of positive studies have identified promising therapies for moderate TBI, the predictive validity of the model may be compromised when findings are translated to severely injured patients. Recently, the clinical relevance of LFP has been enhanced by combining the injury with secondary insults, as well as broadening studies to incorporate issues of gender and age to better approximate the range of human TBI within study design. We conclude that the LFP brain injury model is an appropriate tool to study the cellular and mechanistic aspects of human TBI that cannot be addressed in the clinical setting, as well as for the development and characterization of novel therapeutic interventions. Continued translation of pre-clinical findings to human TBI will enhance the predictive validity of the LFP model, and allow novel neuroprotective and neuroregenerative treatment strategies developed in the laboratory to reach the appropriate TBI patients.

Total and ionized plasma magnesium concentrations in children after traumatic brain injury

This study examined 1) whether plasma total Mg (TMg) and ionized Mg (IMg) concentrations in children are reduced by traumatic brain injury (TBI) and 2) whether the extent of reduction correlates with severity of trauma assessed by the Glasgow Coma Scale (GSC) score. This was a prospective cohort study of 98 pediatric patients who had TBI and were admitted through the emergency department. A GCS score was assigned and blood was obtained upon presentation and 24 h later. Plasma was analyzed for TMg and IMg. Patients were grouped into three categories-GCS scores 13-15, 8-12, and <8-to designate mild (n=21), moderate (n=37), and severe (n=40) TBI, respectively. Blood was obtained from 50 healthy children before elective surgery as controls. Control subjects had a TMg and an IMg of 0.94 +/- 0.08 and 0.550 +/- 0.06 mM. TBI patients had an initial TMg and IMg of 0.83 +/- 0.09 and 0.520 +/- 0.05 mM, respectively. Initial TMg for mild, moderate, and severe TBI subgroups (0.87 +/- 0.16, 0.81 +/- 0.15, and 0.83 +/- 0.14 mM, respectively) was reduced from control subjects (p <0.01). IMg was reduced only in the severe TBI subgroup (0.516 +/- 0.07 mM; p=0.016). Twenty-four hours later, TMg remained lower than in control subjects for all subgroups of TBI; however, IMg normalized. TBI in children is associated with a reduction in TMg, whereas IMg decreased only with severe TBI. IMg returned to control values by 24 h despite a continued lower TMg, suggesting mechanisms to maintain IMg. Changes in plasma IMg may serve as a marker for TBI but only over a limited time interval.

Effect of magnesium sulfate administration on blood-brain barrier in a rat model of intraperitoneal sepsis: a randomized controlled experimental study

Introduction

Permeability changes in the blood–brain barrier (BBB) and their possible contribution to brain edema formation have a crucial role in the pathophysiology of septic encephalopathy. Magnesium sulfate has been shown to have a protective effect on BBB integrity in multiple experimental models. In this study we determine whether magnesium sulfate administration could have any protective effects on BBB derangement in a rat model of sepsis.

Methods

This randomized controlled experimental study was performed on adult male Sprague–Dawley rats. Intraperitoneal sepsis was induced by using the infected fibrin–thrombin clot model. To examine the effect of magnesium in septic and sham-operated rats, a dose of 750 μmol/kg magnesium sulfate was given intramuscularly immediately after surgery. Control groups for both infected and sham-operated rats were injected with equal volume of saline. Those rats surviving for 24 hours were anesthetized and decapitated for the investigation of brain tissue specific gravity and BBB integrity by the spectrophotometric assay of Evans blue dye extravasations. Another set of experiments was performed for hemodynamic measurements and plasma magnesium level analysis. Rats were allocated into four parallel groups undergoing identical procedures.

Results

Sepsis significantly increased BBB permeability to Evans blue. The dye content of each hemisphere was significantly lower in the magnesium-treated septic rats (left hemisphere, 0.00218 ± 0.0005; right hemisphere, 0.00199 ± 0.0007 [all results are means ± standard deviation]) than in control septic animals (left hemisphere, 0.00466 ± 0.0002; right hemisphere, 0.00641 ± 0.0003). In septic animals treated with magnesium sulfate, specific gravity was higher (left hemisphere, 1.0438 ± 0.0007; right hemisphere, 1.0439 ± 0.0004) than in the untreated septic animals (left hemisphere, 1.0429 ± 0.0009; right hemisphere, 1.0424 ± 0.0012), indicating less edema formation with the administration of magnesium. A significant decrease in plasma magnesium levels was observed 24 hours after the induction of sepsis. The dose of magnesium that we used maintained the baseline plasma magnesium levels in magnesium-treated septic rats.

Conclusions

Magnesium administration attenuated the increased BBB permeability defect and caused a reduction in brain edema formation in our rat model of intraperitoneal sepsis.

A Molecular Basis for the Efficacy of Magnesium Treatment following Traumatic Brain Injury in Rats

Magnesium ions have been shown to be a promising treatment for brain lesions caused by traumatic brain injury (TBI), as well as for the associated acute neurodegeneration and progressive functional deficits. This study investigated the effects of magnesium on the expression of the cell death/survival related proteins following TBI. Male Sprague-Dawley (SD) rats (n = 66, 280-320 g body weight) were subjected to sham surgery alone (n = 14), or to the surgery followed by a lateral fluid percussion brain injury of moderate severity (n = 52, 2.4-2.7 atm). The injured rats were randomly treated with an intravenous bolus of magnesium chloride (n = 26, 125 micromol) or saline vehicle (n = 26). The coronal brain sections were quantitatively analyzed for cell apoptosis and the expression of p53-related proteins, Bcl-2, cyclin D1 and PCNA at 1, 2, and 4 days post-injury by immunohistochemistry or in situ hybridization. Tissue damage was observed primarily in the ipsilateral cortex of the injured region with the induction of apoptosis and p53 mRNA level at 2 days after TBI. The expression of p53 and responding proteins (p21(WAF1/CIP1), Mdm2 and Bax) showed a temporal pattern similar to the apoptotic events in the time course experiments. They were induced in the early time points of days 1-2, decreasing by day 4 after TBI. In contrast, the expression of the cell survival related proteins - Bcl-2, cyclin D1, and PCNA - was most significant at day 4 post-injury, when the rate of apoptosis decreased. Magnesium treatment resulted in a reduction in apoptosis and expression of p53-related proteins. However, it had only a slight additive effect on the expression of the survival related proteins in the same time-course. These results provide a molecular basis for the efficiency of magnesium in treating TBI-induced tissue damage.

The effects of systemic magnesium sulfate infusion on brain magnesium concentrations and energy state during hypoxia-ischemia in newborn miniswine

The mechanism of neuroprotection associated with systemically administered magnesium remains unclear. This investigation examined the acute effects of systemically administered MgSO4 on brain extracellular ([Mg]ecf) and intracellular ([Mg]i) fluid Mg concentrations, specific brain phosphorylated metabolites, and brain intracellular pH. Miniswine were studied with P-31 magnetic resonance spectra, to derive [Mg]i, and brain microdialysis probes, to measure [Mg]ecf. Animals were infused with MgSO4 (n = 5, 275 mg/kg over 30 min followed by 100 mg/kg over 30 min, designated MgHI) or Na2SO4 (n = 5, designated NaHI), and both groups underwent hypoxia-ischemia (HI) over the last 15 min of the infusions. Groups differed in plasma [Mg] at the completion of HI (9.1 +/- 1.5 versus 1.1 +/- 0.6 mM for MgHI and NaHI, respectively, p < 0.05). MgHI had elevations of [Mg]ecf (0.23 +/- 0.11 and 0.40 +/- 0.14 mM at control and completion of HI, respectively), and [Mg]ecf was unchanged for NaHI (p < 0.05 versus MgHI). At the completion of HI, MgHI had greater decreases in nucleoside triphosphate (NTP) (48 +/- 6% of control), and more brain acidosis after HI (6.01 +/- 0.07) compared with NaHI (NTP, 70 +/- 3% of control; brain pH, 6.51 +/- 0.14, both p < 0.05 versus MgHI). [Mg]i increased to elevated values during HI in both MgHI and NaHI (p < 0.05 versus control of each group) and remained higher in MgHI over the next 25 min (p < 0.05 versus NaHI). There were inverse correlations during HI between [Mg]i and brain NTP (r2 = 0.73 and 0.59 for MgHI and NaHI, respectively), and brain acidosis (r2 = 0.85 and 0.85 for MgHI and NaHI, respectively) in each group. These findings indicate complex effects of Mg on the brain. Elevation of [Mg]ecf may be beneficial with regards to excitatory neurotransmitters. However, greater disturbance of brain NTP concentration, more acidosis, and the increase in [Mg]i may offset any benefit. The results warrant further investigation using indicators of neuronal injury to determine whether Mg supplementation provides neuroprotection.

Monitoring of serum ionized magnesium in neurosurgical intensive care unit: preliminary results

BACKGROUND

Our purpose was to determine the values for serum ionized magnesium (Mg) concentrations in traumatic brain injury and its effect on the prognostic scores of patients.

METHODS

We prospectively measured serum ionized magnesium concentrations in 30 patients that were classified into three groups (severe, moderate, mild) by Glasgow Coma Scale Score. Serum ionized magnesium concentrations were measured during posttraumatic 5 days. Thirty patients with head trauma were followed in a neurosurgical intensive care unit with monitoring serum ionized magnesium concentrations. All patients were treated conservatively.

RESULTS

We found significant difference of serum ionized magnesium concentrations when we compared all groups with each other (p<0.001).

CONCLUSIONS

Based on this clinical preliminary study, traumatic brain injury is associated with graded deficit in serum ionized magnesium concentrations. Thus, measurement of serum ionized magnesium concentrations can be used as a clinical marker in traumatic brain injury.

Low extracellular magnesium ions induce lipid peroxidation and activation of nuclear factor-kappa B in canine cerebral vascular smooth muscle: possible relation to traumatic brain injury and strokes

The present study was designed to test the hypothesis that administration of low extracellular levels of magnesium ions ([Mg(2+)](o)) to primary cultured cerebral vascular smooth muscle cells will cause lipid peroxidation, degradation of IkappaB-alpha, and activation of nuclear transcription factor kappa B (NF-kappaB) in cultured cerebral vascular smooth muscle cells. Low [Mg(2+)](o) (0, 0.15, 0.3 and 0.48 mM) resulted in concentration-dependent rises in malondialdehyde (MDA) in as little as 3 h after exposure to low [Mg(2+)](o), rising to levels 3-12xnormal after 18-24 h; the lower the [Mg(2+)](o), the higher the MDA level. Using electrophoretic mobility shift assays and specific antibodies, low [Mg(2+)](o) caused two DNA-binding proteins (p50, p65) to rise in nuclear extracts in a concentration-dependent manner. High [Mg(2+)](o) (i.e. 4.8 mM) downregulated p50 and p65. Using a rabbit antibody, IkappaB phosphorylation (and degradation) was stimulated by low [Mg(2+)](o) (in a concentration-dependent manner) and inhibited by a low concentration of the NF-kappaB inhibitor, pyrrolidine dithiocarbamate. These new biochemical and molecular data indicate that low [Mg(2+)](o), in concentrations found in the blood of patients, after traumatic brain injury (TBI) and diverse types of strokes, can elicit rapid lipid peroxidation and activation of NF-kappaB in cerebral vascular smooth muscle cells. The present results, when viewed in light of other recently published data, suggest that low [Mg(2+)](o)-induced lipid peroxidation and activation of NF-kappaB play important roles in TBI and diverse types of strokes.

The behavioral effects of magnesium therapy on recovery of function following bilateral anterior medial cortex lesions in the rat

Magnesium (Mg(++)) therapy has been shown to be neuroprotective and to facilitate recovery of motor and sensorimotor function in a variety of animal models of traumatic brain injury. However, few studies have investigated the efficacy of Mg(++) therapy on cognitive impairments following injury. The present study evaluated the ability of magnesium chloride (MgCl(2)) to facilitate recovery of function following bilateral anterior medial cortex lesions (bAMC). Rats received electrolytic bAMC lesions or sham surgery and were then treated with 1 mmol/kg, i.p. MgCl(2), 2 mmol/kg, i.p. MgCl(2), or 1.0 ml/kg, i.p. 0.9% saline. Drug treatment was administered 15 min following injury with subsequent injections administered at 24 and 72 h. Rats were tested on a battery of behavioral tests that measured both cognitive (reference and working memory in the Morris Water Maze (MWM) and spatial delayed matching-to-sample (DMTS)) and sensorimotor performance (bilateral tactile adhesive removal). The results indicated that bAMC lesions produced significant cognitive impairments in reference memory and working memory in the MWM, DMTS and sensorimotor impairments compared to shams. Mg(++) therapy exhibited a dose-dependent effect in facilitating recovery of function. Administration of 2mmol of MgCl(2) significantly improved performance on the bilateral adhesive tactile removal test, DMTS and working memory tests. The 1 mmol dose of MgCl(2) reduced the initial deficit on the tactile adhesive removal test and reduced the working memory impairment on the second day of testing. These results suggest Mg(++) therapy improves cognitive performance following injury in a dose-dependent manner.

Effects of magnesium administration on brain edema and blood-brain barrier breakdown after experimental traumatic brain injury in rats

In this study, we examined the effects of magnesium sulfate administration on brain edema and blood-brain barrier breakdown after experimental traumatic brain injury in rats. Seventy-one adult male Sprague-Dawley rats were anesthetized, and experimental closed head trauma was induced by allowing a 450-g weight to fall from a 2-m height onto a metallic disk fixed to the intact skull. Sixty-eight surviving rats were randomly assigned to receive an intraperitoneal bolus of either 750 micromol/kg magnesium sulfate (group 4; n = 30) or 1 mL of saline (group 2; n = 30) 30 minutes after induction of traumatic brain injury; 39 nontraumatized animals received saline (group 1; n = 21) or magnesium sulfate (group 3; n = 18) with an identical protocol of administration. Brain water content and brain tissue specific gravity, as indicators of brain edema, were measured 24 hours after traumatic brain injury. Blood-brain barrier integrity was evaluated quantitatively 24 hours after injury by spectrophotometric assay of Evans blue dye extravasations. In the magnesium-treated injured group, brain water content was significantly reduced (left hemisphere: group 2, 83.2 +/- 0.8; group 4, 78.4 +/- 0.7 [P <.05]; right hemisphere: group 2, 83.1 +/- 0.7; group 4, 78.4 +/- 0.5. [P <.05]) and brain tissue specific gravity was significantly increased (left hemisphere: group 2, 1.0391 +/- 0.0008; group 4, 1.0437 +/- 0.001 [P <.05]; right hemisphere, group 2, 1.0384 +/- 0.001; group 4, 1.0442 +/- 0.005 [P <.05]) compared with the saline-treated injured group. Evans blue dye content in the brain tissue was significantly decreased in the magnesium-treated injured group (left hemisphere: group 2, 0.0204 +/- 0.03; group 4, 0.0013 +/- 0.0002 [P <.05]; right hemisphere: group 2, 0.0064 +/- 0.0009; group 4, 0.0013 +/- 0.0003 [P <.05]) compared with the saline-treated injured group. The findings of the present study support that beneficial effects of magnesium sulfate exist after severe traumatic brain injury in rats. These results also indicate that a blood-brain barrier permeability defect occurs after this model of diffuse traumatic brain injury, and magnesium seems to attenuate this defect.

Structural and functional damage sustained by mitochondria after traumatic brain injury in the rat: evidence for differentially sensitive populations in the cortex and hippocampus

The cellular and molecular pathways initiated by traumatic brain injury (TBI) may compromise the function and structural integrity of mitochondria, thereby contributing to cerebral metabolic dysfunction and cell death. The extent to which TBI affects regional mitochondrial populations with respect to structure, function, and swelling was assessed 3 hours and 24 hours after lateral fluid-percussion brain injury in the rat. Significantly less mitochondrial protein was isolated from the injured compared with uninjured parietotemporal cortex, whereas comparable yields were obtained from the hippocampus. After injury, cortical and hippocampal tissue ATP concentrations declined significantly to 60% and 40% of control, respectively, in the absence of respiratory deficits in isolated mitochondria. Mitochondria with ultrastructural morphologic damage comprised a significantly greater percent of the population isolated from injured than uninjured brain. As determined by photon correlation spectroscopy, the mean mitochondrial radius decreased significantly in injured cortical populations (361 +/- 40 nm at 24 hours) and increased significantly in injured hippocampal populations (442 +/- 36 at 3 hours) compared with uninjured populations (Ctx: 418 +/- 44; Hipp: 393 +/- 24). Calcium-induced deenergized swelling rates of isolated mitochondrial populations were significantly slower in injured compared with uninjured samples, suggesting that injury alters the kinetics of mitochondrial permeability transition (MPT) pore activation. Cyclosporin A (CsA)-insensitive swelling was reduced in the cortex, and CsA-sensitive and CsA-insensitive swelling both were reduced in the hippocampus, demonstrating that regulated MPT pores remain in mitochondria isolated from injured brain. A proposed mitochondrial population model synthesizes these data and suggests that cortical mitochondria may be depleted after TBI, with a physically smaller, MPT-regulated population remaining. Hippocampal mitochondria may sustain damage associated with ballooned membranes and reduced MPT pore calcium sensitivity. The heterogeneous mitochondrial response to TBI may underlie posttraumatic metabolic dysfunction and contribute to the pathophysiology of TBI.

Magnesium attenuates persistent functional deficits following diffuse traumatic brain injury in rats

Although a number of studies have demonstrated that magnesium improves acute motor and cognitive outcome after traumatic brain injury, others have failed to show positive effects on cognitive outcome and none have examined persistent functional deficits. The present study shows that severe impact-acceleration induced, diffuse traumatic brain injury in rats produced profound motor and cognitive deficits that persisted for at least 4 weeks after trauma. Intravenous administration of magnesium sulfate (250 micromoles/kg) at 30 min after injury significantly improved rotarod (sensorimotor) and open field (stress/anxiety) performance, and led to a faster rate of recovery in the Barnes maze (learning). We conclude that posttraumatic magnesium administration attenuates long-term motor and cognitive deficits after traumatic brain injury, and that this improvement may include some reduction of post-traumatic stress and anxiety.

Optical spectroscopy and prevention of deleterious cerebral vascular effects of ethanol by magnesium ions

Previously, it has been suggested that acute ethanol (alcohol) administration can result in concentration-dependent vasoconstriction and decreased cerebral blood flow. Here, we present in vivo results using rapid (240 nm/min) optical backscatter measurements, with an intact cranial preparation in the rat, indicating that acute infusion of ethanol directly into the rat brain rapidly produces dose-dependent vasoconstriction of the cerebral microcirculation associated with a pronounced reduction in tissue blood content, pronounced rises in deoxyhemoglobin, significantly increased levels of reduced cytochrome oxidase and microvascular damage as the dose increases. Furthermore, we present in vivo experiments demonstrating the capability of magnesium ions (Mg(2+)) to attenuate and prevent these deleterious responses. Optical backscatter spectra (500-800 nm) were obtained by directing a single sending and receiving fiber to a portion of the left parietal cranium (in anesthetized rats), shaved to a translucent appearance to facilitate optical penetration. In the absence of added Mg(2+), infusion of a 10% solution of ethanol at 0.34 ml/min ( approximately 26.8 mg/min) produced prompt vasoconstriction as evidenced by a greater than 90% loss of oxyhemoglobin from the field-of-view and increases in levels of reduced cytochrome oxidase to between 50% and >90%. These effects were partially, to nearly completely, attenuated by the addition of MgCl(2) to the infusate containing added ethanol. Of special interest was the observation that attenuation of the vasoconstrictive effect of ethanol by Mg(2+) persisted despite a subsequent ethanol challenge without added Mg(2+). The results obtained demonstrate that, depending on dose, ethanol can produce prompt and severe vasoconstriction of the intact cerebral microcirculation and that infusion of moderate doses of Mg(2+) can largely attenuate and prevent this response. We conclude that appreciable, graded changes in cerebral cytochrome oxidase aa(3), blood volume and the state of hemoglobin occur at minimal tissue levels of ethanol which can be modulated by Mg(2+).

Pharmacological treatment of traumatic brain injury: a review of agents in development

Successful treatment strategies for patients with traumatic brain injury (TBI) remain elusive despite standardised clinical treatment guidelines, improved understanding of mechanisms of cellular response to trauma, and a decade of clinical trials aimed at identifying therapeutic agents targeted at mediators of secondary injury. The information explosion relative to mechanisms of secondary injury has identified several potential targets for intervention. Depending on the type of injury to the brain and the intensity and the success of resuscitation, necrosis, apoptosis, inflammatory and excitotoxic cellular damage can be seen. These same processes may continue postinjury, depending on the adequacy of clinical care. Each of these mechanisms of cellular damage can initiate a cascade of events mediated by endogenous signals that lead to secondary neurological injury. Several factors contributed to the failure of earlier clinical trials. Now that these have been recognised, a positive impact on future drug development in TBI has been realised. Both the US and Europe have organised brain injury consortiums where experts in the treatment of TBI provide insight into study design, implementation, conduct and oversight in conjunction with the pharmaceutical industry. Consequently, future clinical trials of new investigational treatments have greater potential for identifying therapies of merit in specific populations of patients with TBI. Pharmacological strategies under investigation are targeting sites involved in the secondary cascade that contribute to overall poor outcome following the primary injury. These treatments include ion channel antagonists including calcium channel antagonists, growth factors, antioxidants, stem cells, apoptosis inhibitors, and inhibitors of other signal modulators. In conclusion, the complexity of TBI pathology and the mechanisms contributing to secondary injury present unique therapeutic challenges. Appropriate research targets for intervention continue to be investigated, however, the likelihood of improving outcomes with a single approach is extremely small. There is a need for collaborative efforts to investigate the optimal time for drug administration and the logical sequence or combination of treatments that will ultimately lead to improved neurological outcomes in this population.

Mild head injury increasing the brain's vulnerability to a second concussive impact

OBJECT

Mild, traumatic repetitive head injury (RHI) leads to neurobehavioral impairment and is associated with the early onset of neurodegenerative disease. The authors developed an animal model to investigate the behavioral and pathological changes associated with RHI.

METHODS

Adult male C57BL/6 mice were subjected to a single injury (43 mice), repetitive injury (two injuries 24 hours apart; 49 mice), or no impact (36 mice). Cognitive function was assessed using the Morris water maze test, and neurological motor function was evaluated using a battery of neuroscore, rotarod, and rotating pole tests. The animals were also evaluated for cardiovascular changes, blood-brain barrier (BBB) breakdown, traumatic axonal injury, and neurodegenerative and histopathological changes between 1 day and 56 days after brain trauma. No cognitive dysfunction was detected in any group. The single-impact group showed mild impairment according to the neuroscore test at only 3 days postinjury, whereas RHI caused pronounced deficits at 3 days and 7 days following the second injury. Moreover, RHI led to functional impairment during the rotarod and rotating pole tests that was not observed in any animal after a single impact. Small areas of cortical BBB breakdown and axonal injury. observed after a single brain injury, were profoundly exacerbated after RHI. Immunohistochemical staining for microtubule-associated protein-2 revealed marked regional loss of immunoreactivity only in animals subjected to RHI. No deposits of beta-amyloid or tau were observed in any brain-injured animal.

CONCLUSIONS

On the basis of their results, the authors suggest that the brain has an increased vulnerability to a second traumatic insult for at least 24 hours following an initial episode of mild brain trauma.

Magnesium sulfate attenuates increased blood-brain barrier permeability during insulin-induced hypoglycemia in rats

Magnesium probably protects brain tissue against the effects of cerebral ischemia, brain injury and stroke through its actions as a calcium antagonist and inhibitor of excitatory amino acids. The effects of magnesium sulfate on cerebrovascular permeability to a dye, Evans blue, were studied during insulin-induced hypoglycemia with hypothermia in rats. Hypoglycemia was induced by an intramuscular injection of insulin. After giving insulin, each animal received MgSO4 (270 mg/kg) ip, followed by a 27 mg/kg dose every 20 min for 2.5 h. Plasma glucose and Mg2+ levels of animals were measured. Magnesium concentrations increased in the serum following MgSO4 administration (6.05 ± 0.57 vs. 2.58 ± 0.14 mg/dL in the Mg2+ group, and 7.14 ± 0.42 vs. 2.78 ± 0.06 mg/dL in the insulin + Mg2+ group, P < 0.01). Plasma glucose levels decreased following hypoglycemia (4 ± 0.66 vs. 118 ± 2.23 mg/dL in the insulin group, and 7 ± 1.59 vs. 118 ± 4.84 mg/dL in the insulin + Mg2+ group, P < 0.01). Blood-brain barrier permeability to Evans blue considerably increased in hypoglycemic rats (P < 0.01). In contrast, blood-brain barrier permeability to Evans blue was significantly reduced in treatment of hypoglycemic rats with MgSO4 (P < 0.01). These results indicate that Mg2+ greatly reduced the passage of exogenous vascular tracer bound to albumin into the brain during hypoglycemia with hypothermia. Mg2+ could have protective effects on blood-brain barrier permeability against insulin-induced hypoglycemia.Key words: blood-brain barrier, hypoglycemia, Mg2+, Evans-blue.

Subdural hematoma following traumatic brain injury causes a secondary decline in brain free magnesium concentration

A number of studies have demonstrated that neurologic motor and cognitive deficits induced by traumatic brain injury (TBI) can be attenuated with administration of magnesium salts. However, many severe traumatic brain injuries have a significant hematoma that develops subsequent to the primary events, and it is unclear whether magnesium salts are effective in this situation. In the present study, an impact-acceleration rodent model of TBI was used to produce an injury that causes an extensive subdural hematoma in over 50% of injured animals. At 30 min after TBI, rats were randomly administered 250 micromoles/kg intravenous MgSO4 or equal volume saline before being monitored by magnetic resonance spectroscopy for 8 h to determine brain intracellular free magnesium concentration. Animals were then assessed for neurologic motor deficits over 1 week using a rotarod device, followed by postmortem examination for presence of subdural hematoma. Animals with subdural hematoma treated with MgSO4 showed no improvement in motor outcome when compared to nontreated controls. Animals with no visible subdural hematoma demonstrated a significant improvement (p < 0.05 by ANOVA) in rotarod scores with MgSO4 treatment. Brain free magnesium concentration in the magnesium treated/hematoma group demonstrated a biphasic decline made up of an immediate initial decline, recovery of brain magnesium levels with MgSO4 treatment, and then a significant second magnesium decline (p < 0.05). Such a secondary decline did not occur in the Mg treated/no hematoma animals. Our results suggest that development of a subdural hematoma following TBI results in a decline in brain magnesium, even after bolus administration of magnesium salts. Such effects of hematoma development will need to be considered in trials examining efficacy of magnesium salts as an intervention following TBI.

The nutritional management of patients with head injuries

Severe head injuries tend to be associated with hypermetabolism and hypercatabolism resulting in negative nitrogen balances which may exceed 30 grams day-1. Enteral feeding should begin as soon as the patient is hemodynamically stable, attempting to reach a non-protein caloric intake of at least 30-35 kcal kg-1 day-1 and a protein intake of 2.0-2.5 g kg-1 day-1 as soon as possible. With severe head injuries (Glasgow Coma Scale < 8), there is an increased tendency for gastric feeding to regurgitate into the upper airway. Keeping the patient upright and checking residuals is important in such patients. Jejunal feedings are less apt to be aspirated. If it is apparent that the gastro-intestinal tract cannot be used to reach the nutritional goals within three days, total parental nutrition is begun within 24-48 h so as to reach these nutrition goals by either one or both routes by the third or fourth day. Blood glucose levels exceeding 150-200 mg dl-1 tend to increase the severity of the neurologic problems and efforts should be made to prevent hyperglycemia by carefully regulating the glucose and insulin intake. Indirect calorimetry to determine the respiratory quotient and resting energy expenditure should be determined twice weekly. To determine N2 balance, urinary urea nitrogen should be measured in 24-h specimens. These tests should be performed once or twice weekly until it is clear that the nutrition is adequate.

Acute cytoskeletal alterations and cell death induced by experimental brain injury are attenuated by magnesium treatment and exacerbated by magnesium deficiency

Traumatic brain injury results in a profound decline in intracellular magnesium ion levels that may jeopardize critical cellular functions. We examined the consequences of preinjury magnesium deficiency and post-traumatic magnesium treatment on injury-induced cytoskeletal damage and cell death at 24 h after injury. Adult male rats were fed either a normal (n = 24) or magnesium-deficient diet (n = 16) for 2 wk prior to anesthesia and lateral fluid percussion brain injury (n = 31) or sham injury (n = 9). Normally fed animals were then randomized to receive magnesium chloride (125 micromol, i.v., n = 10) or vehicle solution (n = 11) at 10 min postinjury. Magnesium treatment reduced cortical cell loss (p < 0.05), cortical alterations in microtubule-associated protein-2 (MAP-2) (p < 0.05), and both cortical and hippocampal calpain-mediated spectrin breakdown (p < 0.05 for each region) when compared to vehicle treatment. Conversely, magnesium deficiency prior to brain injury led to a greater area of cortical cell loss (p < 0.05 compared to vehicle treatment). Moreover, brain injury to magnesium-deficient rats resulted in cytoskeletal alterations within the cortex and hippocampus that were not observed in vehicle- or magnesium-treated animals. These data suggest that cortical cell death and cytoskeletal disruptions in cortical and hippocampal neurons may be sensitive to magnesium status after experimental brain injury, and may be mediated in part through modulation of calpains.

Postinjury treatment with magnesium chloride attenuates cortical damage after traumatic brain injury in rats

The neuroprotective effect of magnesium chloride (MgCl2), a compound previously demonstrated to improve behavioral and neurochemical outcome in several models of experimental brain injury, was evaluated in the present study. Male Sprague-Dawley rats were anesthetized and subjected to lateral fluid-percussion brain injury of moderate severity (2.5-2.8 atm). A cannula was implanted in the left femoral vein and at 1 h following injury, animals randomly received a 15 min i.v. infusion of either MgCl2 (125 micromol/rat) or saline. A second group of animals received anesthesia, surgery, and either MgCl2 or vehicle to serve as uninjured (sham) controls. Two weeks following brain injury, animals were sacrificed, brains removed, and coronal sections were taken for quantitative analysis of cortical lesion volume and hippocampal CA3 cell counts. Traumatic brain injury resulted in a lesion in the ipsilateral cortex and loss of pyramidal neurons in the CA3 region of the hippocampus in vehicle-treated animals (p < 0.01 vs. uninjured animals). Administration of MgCl2 significantly reduced the injury-induced damage in the cortex (p < 0.01) but did not alter posttraumatic cell loss in the CA3 region of the ipsilateral hippocampus. The present study demonstrates that, in addition to its beneficial effects on behavioral outcome, MgCl2 treatment attenuates cortical histological damage when administered following traumatic brain injury.

Opportunities for neuroprotection in traumatic brain injury

Traumatic injury of the brain in man is normally followed by little or no recovery of function by the lesioned tissue. Neuroprotective strategies employed in the acute period after traumatic CNS injury attempt to use pharmacological tools to reduce the progressive secondary injury processes that follow after the initial lesion occurs to limit overall tissue damage. Results from experimental animal studies using a variety of drugs that modulate neurotransmitter function, scavenge free radicals, or interfere with cell death cascades point toward many new opportunities for pharmacological intervention in the acute and subacute period after traumatic brain injury.

Large cortical lesions produce enduring forelimb placing deficits in un-treated rats and treatment with NMDA antagonists or anti-oxidant drugs induces behavioral recovery

Previous studies have utilized a lesion model of cortical injury that produces transient behavioral impairments to investigate the recovery of function process. To better understand the recovery process, it would be beneficial to use a lesion model that produces more severe, enduring, behavioral impairments. The purpose of experiment 1 was to validate whether large lesions of the sensorimotor cortex (SMC), which included the rostral forelimb and caudal forelimb regions, produced enduring behavioral deficits. Rats were given large unilateral electrolytic lesions of the SMC, administered either the N-methyl-D-aspartate (NMDA) antagonist, MK-801 or saline 16 h after injury, and tested on a battery of behavioral tests. Enduring behavioral deficits were observed, for at least 6 months, on two tests of forelimb placing while transient deficits were observed on the foot-fault and somatosensory neutralization tests. Administration of MK-801 facilitated recovery on the somatosensory neutralization test; however, it did not induce recovery on either forelimb placing test. A second experiment was performed to determine if earlier administration of MK-801, the NMDA antagonist magnesium chloride (MgCl(2)), or the anti-oxidant N-tert-butyl-alpha-phenylnitrone (PBN) could induce behavioral recovery in this chronic model. Treatment with these drugs induced behavioral recovery on the forelimb placing tests, whereas, the saline-treated rats did not show any signs of behavioral recovery for at least 3 months. Anatomical analysis of the striatum showed that MK-801 and MgCl(2) but not PBN reduced the extent of lesion-induced striatal atrophy. These results suggest that administration of MK-801, MgCl(2), or PBN shortly after cortical injury can induce recovery of function when recovery is otherwise not expected in un-treated rats.

Experimental models of brain trauma

A short review of the most widely used and popular experimental models of traumatic brain injury is presented. This review focuses on current animal models of traumatic brain injury that apply mechanical energy to the skull or, after trephination of the skull, to the intact dura. Recent experimental studies evaluating the pathobiology of traumatic brain injury using these models are also discussed. This article attempts to provide a broad overview of current knowledge and controversies in experimental animal research on brain trauma.

Postinjury magnesium treatment attenuates traumatic brain injury-induced cortical induction of p53 mRNA in rats

Administration of magnesium has been shown to be neuroprotective in experimental models of traumatic brain injury (TBI). The present study examined the effect of magnesium on posttraumatic regional induction of p53, a gene associated with induction of cell death. Male Sprague-Dawley rats (350-400 g, n = 26) were anesthetized with sodium pentobarbital and subjected to either lateral fluid percussion brain injury of moderate severity (2.4-2.6 atm; n = 22) or sham surgery (n = 4). At 15 min postinjury, animals randomly received an intravenous bolus of either 125 micromol magnesium chloride (n = 12) or saline vehicle (n = 10). Expression of p53 mRNA was not observed in any uninjured animal. By 6 h postinjury in vehicle-treated, brain-injured animals, p53 mRNA was induced in the cortex, dentate hilus, and CA3 regions of the hippocampus and geniculate nuclei of the thalamus, ipsilateral to the impact site. Posttraumatic magnesium treatment significantly reduced the number of labeled cells in the injured cortex (P < 0.05), but not in the hippocampus or thalamus. p53 mRNA expression returned to near baseline in all animals by 24 h postinjury. These data suggest that the neuroprotective effects of magnesium treatment may be related, in part, to a downregulation in expression of a gene associated with induction of cell death and further support the utility of magnesium as a pharmacotherapy for TBI.