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Describes the need for neurosurgical capabilities in combat zone to best provide care for combat casualties with trauma brain injury.

Increased resource constraints secondary to a smaller medical footprint, prolonged evacuation times, or overwhelming casualty volumes all increase the challenges of effective management of traumatic brain injury (TBI) in the austere environment. Prehospital providers are responsible for the battlefield recognition and initial management of TBI. As such, targeted education is critical to efficient injury recognition, promoting both provider readiness and improved patient outcomes. When austere conditions limit or prevent definitive treatment, a comprehensive understanding of TBI pathophysiology can help inform acute care and enhance prevention of secondary brain injury. Field deployable, noninvasive TBI assessment and monitoring devices are urgently needed and are currently undergoing clinical evaluation. Evidence shows that the assessment, monitoring, and treatment in the first few hours and days after injury should focus on the preservation of cerebral perfusion and oxygenation. For cases where medical management is inadequate (eg, evidence of an enlarging intracranial hematoma), guidelines have been developed for the performance of cranial surgery by nonneurosurgeons. TBI management in the austere environment will continue to be a challenge, but research focused on improving evidence-based monitoring and therapeutic interventions can help to mitigate some of these challenges and improve patient outcomes.

Energy drinks (EDs) have become an integral part of the young adult, athletic, and military culture. Many athletes are convinced that EDs enhance performance, and service members as well as college students frequently use EDs as stimulants to counter sleep deprivation, or to improve academic performance. However, concerns have been raised by some military leaders about potential adverse effects of EDs.

The expression and proteolysis of caspase family proteins are involved in the initiation and execution of apoptosis, which has been reported to occur in human and experimental traumatic brain injury (TBI). Caspase-3, -6, and -7 belong to the group of executioner caspases, which are cleaved and activated at the late, irreversible stage of apoptosis. Our previous studies demonstrated roles for caspase-1, -3, and -8 in humans after severe TBI. Here we report expression of caspase-7 mRNA and protein in humans after TBI (n = 16) and control brain-bank tissue (n = 6). Semiquantitative reverse transcription polymerase chain reaction showed no differences between caspase-7 mRNA in TBI patients versus controls (73 ± 24 vs. 85 ± 56 relative optical density [ROD], respectively). In contrast, Western blot analysis showed increased pro-caspase-7 in TBI patients versus controls (214 ± 30 vs. 1 ± 1 ROD, respectively), as well as an increase in the ∼20 kD proteolytic fragment in TBI patients versus controls (86 ± 13 vs. 22 ± 12 ROD, respectively), consistent with activation of caspase-7 after TBI in humans. Immunohistochemical analysis showed that cells expressing caspase- 7 included astrocytes and neurons and possibly other glial cell types and infiltrated inflammatory cells. These data show that caspase-7 and its cleavage product are increased in human brain after TBI in many central nervous system, as well as noncentral nervous system, cell types. Thus, caspase-7 may play a role in the glial and inflammatory responses, and possibly neuronal death, after TBI in humans.

Patients sustaining severe traumatic brain injury (TBI) have variable long-term outcomes. We examined the association between Glasgow Outcome Scale (GOS) assessed at 3 months and long-term outcomes at 12 months after TBI. We studied 159 patients with severe, closed traumatic brain injuries (Glasgow Coma Scale [GCS] ≤ 8) who were treated at an academic medical center and survived for a minimum of 3 months after TBI. Demographics and admission clinical data and GOS at 3 and 12 months were analyzed. Multivariate logistic regression was used to asses the relationship between 3-month GOS, demographics, and clinical data and a poor outcome, defined as GOS 1–3 assessed at 12 months after injury. The patient population was predominantly male (77%), with a median age of 30 years and a median admission GCS of 6. The logistic regression model showed that the GOS at 3 months was the best predictor of 12-month outcomes (odds ratio = 15.22, p < 0.001). The presence of prolonged hypotension, diffuse axonal injury (DAI), and fixed and dilated pupils on admission were also significant independent predictors of poor 12-month outcome (for all, p ≤ 0.047). The adjusted logistic model showed a steep gradient of long-term recovery potential depending upon GOS at 3 months, ranging from an 89.4% chance of poor outcome for patients with a GOS of 2, to a 0.11% chance of poor outcome for those with a GOS of 5. The 3-month GOS is a powerful independent predictor of long-term outcome for patients with severe TBI. Prolonged hypotension, DAI, and the presence of fixed and dilated pupils were also independent predictors of poor outcome.

This study examined the relationship between admission serum alcohol level (ETOH) and cerebral blood flow (CBF) and outcomes in the adult traumatic brain injured (TBI) population. We hypothesized that individuals with ETOH > 100 mg/dL will have decreased blood flow on admission and poorer outcomes. Eighty subjects, age 16-65, with severe TBI (Glasgow Coma Score [GCS] ≤ 8) were entered into the study. Correlational analysis assessed the relationship between ETOH and admission severity of injury scores as measured by Marshall and APACHE III scores, CBF, and outcomes. Comparison of CBF and outcomes between groups based on admission serum ETOH level was conducted with analysis of variance and post hoc Scheffé analyses as well as regression analysis. There was a significant relationship between serum ETOH level and GCS (p = 0.02), but not APACHE III scores (p = 0.12) or Marshall scores (p = 0.27). There was a significant correlation between global CBF and serum ETOH level (p = 0.02). There was no statistically significant association between serum ETOH level and GOS at 3 (p = 0.97), 6 (p= 0.56), or 12 (p = 0.73) months after injury. The data indicated that serum ETOH levels > 100 mg/dL at the time of admission after a TBI were associated with a decrease in global CBF. Elevated serum ETOH level at time of injury did not, however, impact outcomes.

Striking gender differences have been reported in the pathophysiology and outcome of acute neurological injury. Greater neuroprotection in females versus males may be due, in part, to direct and indirect sex hormone-mediated antioxidant mechanisms. Progesterone administration decreases brain levels of F2-isoprostane, a marker of lipid peroxidation, after experimental traumatic brain injury (TBI) in male rats, and estrogen is neuroprotective in experimental neurological injury. In this study, we evaluated the effect of gender on lipid peroxidation, as assessed by cerebrospinal fluid (CSF) levels of F2-isoprostane, after severe TBI in humans. Lipid peroxidation was assessed in CSF from 68 adults enrolled in two randomized controlled trials evaluating the effect of therapeutic hypothermia after severe TBI (Glasgow coma scale [GCS] score ≤ 8). Patients treated with hypothermia (n = 41, 12 females, 29 males) were cooled to 32-33°C (within ~6 h) for either 24 or 48 h and then re-warmed. F2-isoprostane levels were assessed by ELISA in ventricular CSF samples (n = 199) on day 1, 2, and 3. The association between age, GCS score, time, gender, treatment, duration of treatment, core temperature at the time of CSF sampling, secondary hypoxemia, and CSF F2-isoprostane level was assessed by multivariate and dichotomous analyses. F2-isoprostane was ~2-fold higher in males than females (145.8 ± 39.6 versus 75.4 ± 16.6 pg/mL, day 1 p = 0.018). An effect of time after injury (p = 0.007) was reflected by a marked early peak in F2-isoprostane (day 1). CSF F2-isoprostane was also associated with hypoxemia (p = 0.04). Hypothermia tended to decrease F2-isoprostane levels only in males on d1 after TBI. To our knowledge, this is the first study showing gender differences in lipid peroxidation after clinical TBI. Lipid peroxidation occurs early after severe TBI in adults and is more prominent in males vs females. These results established that gender is an important consideration in clinical trial design, particularly in the case of antioxidant strategies.

There is increasing evidence linking neurodegenerative mechanisms in Alzheimer's disease (AD) and traumatic brain injury (TBI), including increased production of amyloid precursor protein (APP), and amyloid-beta (Aβ) peptide. In vitro data indicate that expression of APP may be regulated in part by the inflammatory cytokine IL-1β. To further investigate the mechanisms involved, we measured APP and IL-1β protein levels and examined immunohistochemical localization of APP in brain tissue from rats subjected to controlled cortical impact (CCI) injury. Animals were examined at time intervals ranging from 3 h to 4 weeks after TBI. The 24-h time point revealed a dramatic increase in APP immunoreactivity, detected with both N- and C-terminal antibodies, in the hippocampus and cortex ipsilateral to injury. This finding was sustained up to 3 days post-injury. At these early time points, APP increase was particularly robust in the white matter axonal tracts. By 14 days after injury, APP immunoreactivity was not significantly different from sham controls in cortex, but remained slightly elevated in hippocampus. Western blot data corroborated early increases in hippocampal and cortical APP in injured versus control animals. Despite profound APP changes, no Aβ deposits were observed at any time after injury. Hippocampal and cortical IL-1β increases were even more robust, with IL-1β levels peaking by 6 h post-injury and returning to baseline by 24-72 h. Our results demonstrate that both APP and IL-1β are rapidly elevated after injury. Because of the rapidity in the IL-1β peak increase, it may serve a role in regulation of APP expression after TBI.

Elevated blood flow velocity (BFV), measured by transcranial Doppler (TCD), has been associated with hyperemia and cerebral vasospasm. This study examined whether the lack of a diastolic notch within the TCD waveform was associated with relative hyperemia within 5 days after injury in 35 traumatic brain injured (TBI) patients. Hyperemia (avDO2of < 4 ml/dL) was present in 16 patients and absent in 19 patients. Two clinicians independently coded TCD waveforms based on the presence of a diastolic notch (88 agreement). There was no significant difference in the presence of a diastolic notch by group; a diastolic notch was present in 57 (11/19) of patients without hyperemia and 81 (13/16) of patients with hyperemia. Sensitivity and specificity of detecting hyperemia using the diastolic notch was 18.7 and 57.9 respectively. The results showed that relative hyperemia was present without an elevation in blood flow velocities, and that the lack of a diastolic notch did not detect the presence of hyperemia in the TBI patient.

Traumatic brain injury (TBI) remains a major public health problem globally. In the United States the incidence of closed head injuries admitted to hospitals is conservatively estimated to be 200 per 100,000 population, and the incidence of penetrating head injury is estimated to be 12 per 100,000, the highest of any developed country in the world. This yields an approximate number of 500,000 new cases each year, a sizeable proportion of which demonstrate signficant long-term disabilities. Unfortunately, there is a paucity of proven therapies for this disease. For a variety of reasons, clinical trials for this condition have been difficult to design and perform. Despite promising pre-clinical data, most of the trials that have been performed in recent years have failed to demonstrate any significant improvement in outcomes. The reasons for these failures have not always been apparent and any insights gained were not always shared. It was therefore feared that we were running the risk of repeating our mistakes. Recognizing the importance of TBI, the National Institute of Neurological Disorders and Stroke (NINDS) sponsored a workshop that brought together experts from clinical, research, and pharmaceutical backgrounds. This workshop proved to be very informative and yielded many insights into previous and future TBI trials. This paper is an attempt to summarize the key points made at the workshop. It is hoped that these lessons will enhance the planning and design of future efforts in this important field of research.

Cognitive impairments are pervasive and persistent sequelae of human traumatic brain injury (TBI). In vivo models of TBI, such as the controlled cortical impact (CCI) and fluid percussion (FP), are utilized extensively to produce deficits reminiscent of those seen clinically with the hope that empirical study will lead to viable therapeutic interventions. Both CCI and FP produce spatial learning acquisition deficits, but only the latter has been reported to impair working memory in rats tested in the Morris water maze (MWM). We hypothesized that a CCI injury would impair working memory similarly to that produced by FP, and that delayed and chronic treatment with the D2 receptor agonist bromocriptine would attenuate both working memory and spatial learning acquisition deficits. To test these hypotheses, isoflurane-anesthetized adult male rats received either a CCI (2.7 mm deformation, 4 m/sec) or sham injury, and 24 h later were administered bromocriptine (5 mg/kg, i.p.) or vehicle, with continued daily injections until all behavioral assessments were completed. Motor function was assessed on beam balance and beam walking tasks on postoperative days 1-5 and cognitive function was evaluated in the MWM on days 11-15 for working memory (experiment 1) and on days 14-18 for spatial learning acquisition (experiment 2). Histological examination (hippocampal CA1 and CA3 cell loss/survival and cortical lesion volume) was conducted 4 weeks after surgery. All injured groups exhibited initial impairments in motor function, working memory, and spatial learning acquisition. Bromocriptine did not affect motor function, but did ameliorate working memory and significantly attenuated spatial acquisition deficits relative to the injured vehicle-treated controls. Additionally, the injured bromocriptine-treated group exhibited significantly more morphologically intact CA3 neurons than the injured vehicle-treated group (55.60 ± 3.10% vs. 38.34 ± 7.78% [p = 0.03]). No significant differences were observed among TBI groups in CA1 cell survival (bromocriptine, 40.26 ± 4.74% vs. vehicle, 29.13 ± 6.63% [p = 0.14]) or cortical lesion volume (bromocriptine, 17.78 ± 0.62 mm3 vs. vehicle, 19.01 ± 1.49 mm3 [p > 0.05]). These data reveal that CCI produces working memory deficits in rats that are similar to those observed following FP, and that the delayed and chronic bromocriptine treatment regimen conferred cognitive and neural protection after TBI.

The use of therapeutic moderate hypothermia for treating severe traumatic brain injury has been reported for more than 50 years. However, the most intense investigation of this treatment has occurred during the last 10 to 15 years. Virtually all preclinical studies have documented a robust treatment effect, not only in terms of reduced excitotoxicity and cerebral acidosis, but also in terms of histologic preservation and improved behavioral outcomes. Several single-center and small multicenter clinical trials conducted during the last decade also demonstrated benefit of early and late therapeutic hypothermia. However, a multicenter trial reported in February 2001 that included nearly 400 patients found no notable differences in neurologic outcomes in matched patients with head injuries who were treated with 48 hours of therapeutic moderate hypothermia compared with those kept at normal temperature. Findings from this study did suggest that rapid rewarming of patients with head injuries may be deleterious. A subgroup of young patients (less than 45 years of age) who were kept normovolemic showed a trend toward improved outcomes when treated with hypothermia. Current investigations, particularly in the preclinical arena, are focusing on combination therapy. To date, however, the addition of fibroblast growth factor, cyclosporine, or interleukin (IL)-10 to therapeutic moderate hypothermia has not been found to provide greater benefit than either therapy when used alone. Future investigations are aimed at further identifying the physiologic mechanisms responsible for secondary brain injury and ways in which other novel combination therapies may be expected to improve outcomes.

Data from the "National Acute Brain Injury Study: Hypothermia" were examined to identify the impact of hypothermia on admission. In all patients, temperature was measured at randomization using bladder catheters with thermistors. Patients assigned to hypothermia were cooled using fluid-circulating pads. Outcome was assessed at 6 months using the dichotomized Glasgow Outcome Scale (good outcome = good recovery/moderate disability; poor outcome = severe disability/vegetative/dead). One-hundred and two patients (hypothermia, 62; normothermia, 40) were hypothermic on admission (≤35.0°C). Hypothermia-on-admission patients assigned to normothermia (n = 40) had a 78% poor outcome, and normothermia-on-admission patients assigned to normothermia had a 52% poor outcome (p < 0.004). Hypothermia-on-admission patients assigned to hypothermia had a lower percentage of poor outcomes than those assigned to normothermia (hypothermia, 61%; normothermia, 78%; p = 0.09). Patients over 45 years of age had an adverse effect of hypothermia regardless of admission temperature due to medical complications. Patients who were hypothermic on admission, age ≤45 years (n = 81), and assigned to hypothermia had a significantly lower percentage of poor outcomes than those assigned to normothermia (hypothermia, 52%; normothermia, 76%; p = 0.02). Factors associated with hypothermia on admission were increased age, prehospital hypotension, smaller size, positive blood alcohol, larger volume of pre-hospital fluids, slightly higher injury severity, and winter enrollment. The treatment effect was found in all of the four centers, which randomized the majority (80%) of the patients. It is unclear whether the improved outcome when hypothermia is maintained is a beneficial effect of very early hypothermia induction or an adverse effect of permitting the patients to rewarm passively.

To determine the relationship between cerebrospinal fluid procalcitonin concentration and severe traumatic brain injury in children.

Despite considerable investigation in rodent models of traumatic brain injury (TBI), no novel therapy has been successfully translated from bench to bedside. Although well-described limitations of clinical trails may account for these failures, several modeling factors may also contribute to the lack of therapeutic translation from the laboratory to the clinic. Specifically, models of TBI may omit one or more critical, clinically relevant pathophysiologic features. In this invited review article, the impact of the limited incorporation of several important clinical pathophysiologic factors in TBI, namely secondary insults (i.e., hypotension and/or hypoxemia), coma, and aspects of standard neurointensive care monitoring and management strategies (i.e., intracranial pressure [ICP] monitoring and ICP-directed therapies, sedation, mechanical ventilation, and cardiovascular support) are discussed. Comparative studies in rodent and large animal models of TBI (which may, in some cases, represent super models) are also presented. We conclude that therapeutic breakthroughs will likely require a multidisciplinary approach, involving investigation in a range of models, including clinically relevant modifications of established animal models, along with development and application of new innovations in clinical trial design.

Adrenomedullin is a recently discovered 52–amino acid peptide that is a potent vasodilator and is produced in the brain in experimental models of cerebral ischemia. Infusion of adrenomedullin increases regional cerebral blood flow and reduces infarct volume after vascular occlusion in rats, and thus may represent an endogenous neuroprotectant. Disturbances in cerebral blood flow (CBF), including hypoperfusion and hyperemia, frequently occur after severe traumatic brain injury (TBI) in infants and children. We hypothesized that cerebrospinal fluid (CSF) adrenomedullin concentration would be increased after severe TBI in infants and children, and that increases in adrenomedullin would be associated with alterations in CBF. We also investigated whether post-traumatic CSF adrenomedullin concentration was associated with relevant clinical variables (CBF, age, Glasgow Coma Scale [GCS] score, mechanism of injury, and outcome). Total adrenomedullin concentration was measured using a radioimmunometric assay. Sixty-six samples of ventricular CSF from 21 pediatric patients were collected during the first 10 days after severe TBI (GCS score < 8). Control CSF was obtained from children (n = 10) undergoing lumbar puncture without TBI or meningitis. Patients received standard neurointensive care, including CSF drainage. CBF was measured using Xenon computed tomography (CT) in 11 of 21 patients. Adrenomedullin concentration was markedly increased in CSF of infants and children after severe TBI vs control (median 4.5 versus 1.0 fmol/mL, p < 0.05). Sixty-two of 66 CSF samples (93.9%) from head-injured infants and children had a total adrenomedullin concentration that was greater than the median value for controls. Increases in CSF adrenomedullin were most commonly observed early after TBI. CBF was positively correlated with CSF adrenomedullin concentration (p < 0.001), but this relationship was not significant when controlling for the effect of time. CSF adrenomedullin was not significantly associated with other selected clinical variables. We conclude adrenomedullin is markedly increased in the CSF of infants and children early after severe TBI. We speculate that adrenomedullin participates in the regulation of CBF after severe TBI.

Chronic frontal lobe functional deficits after traumatic brain injury (TBI) may be associated with altered catecholamine systems in the frontal cortex. To test this, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) levels were examined by immunohistochemistry and Western blot at 1, 7, 14, and 28 days after TBI or sham surgery. No alterations in DBH levels were observed by Western blot at any time point examined, but there was a significant increase in TH expression 28 days after TBI (optical density 334 ± 68 or 3.3-fold, ipsilateral and 218 ± 39 or 2.2-fold, contralateral) relative to the sham controls. The increase in TH may reflect a compensatory response of dopaminergic neurons to upregulate their synthesizing capacity and increase the efficiency of dopamine neurotransmission chronically after TBI.

DNA damage is a common sequela of traumatic brain injury (TBI). Available techniques for the in situ identification of DNA damage include DNA polymerase I-mediated biotin-dATP nick-translation (PANT), the Klenow fragment of DNA polymerase I-mediated biotin-dATP nick-end labeling (Klenow), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). While TUNEL has been widely utilized to detect primarily double-strand DNA breaks, the use of PANT to detect primarily single-strand DNA breaks and Klenow to detect both single- and double-strand DNA breaks has not been reported after TBI. Accordingly, coronal brain sections from naive rats and rats at 0, 0.5, 1, 2, 6, 24, and 72 h (n = 3-5/group) after controlled cortical impact with imposed secondary insult were processed using the PANT, Klenow, and TUNEL methods. Cells with DNA breaks were detected by PANT in the ipsilateral hemisphere as early as 0.5 h after injury and were maximal at 6 h (cortex = 66.3 ± 15.8, dentate gyrus 58.6 ± 12.8, CA1 = 15.8 ± 5.9, CA3 = 12.8 ± 4.2 cells/ × 400 field, mean ± SEM, all p < 0.05 versus naive). Cells with DNA breaks were detected by Klenow as early as 30 min and were maximal at 24 h (cortex = 56.3 ± 14.3, dentate gyrus 78.0 ± 16.7, CA1 = 25.8 ± 4.7, CA3 = 29.3 ± 15.1 cells/ × 400 field, all p < 0.05 versus naive). Cells with DNA breaks were not detected by TUNEL until 2 h and were maximal at 24 h (cortex = 47.7 ± 21.4, dentate gyrus 63.0 ± 11.9, CA1 = 5.6 ± 5.4, CA3 = 6.9 ± 3.7 cells/ × 400 field, cortex and dentate gyrus p < 0.05 versus naive). Dual-label immunofluorescence revealed that PANT-positive cells were predominately neurons. These data demonstrate that TBI results in extensive DNA damage, which includes both single- and double-strand breaks in injured cortex and hippocampus. The presence of multiple types of DNA breaks implicate several pathways in the evolution of DNA damage after TBI.

The influence of anesthetic agents on cerebral blood flow (CBF) was tested in normal rats. CBF is quantified with arterial spin‐labeled MRI in rats anesthetized with either an opiate (fentanyl), a potent inhalation anesthetic agent (isoflurane), or a barbiturate (pentobarbital) using doses commonly employed in experimental paradigms. CBF values were found to be about 2.5–3 times lower in most regions analyzed during anesthesia with either fentanyl (with N2O/O2) or pentobarbital vs. isoflurane (with N2O/O2), in agreement with findings utilizing invasive measurement techniques. CBF was heterogeneous in rats anesthetized with isoflurane (with N2O/O2), but relatively homogeneous in rats anesthetized with either fentanyl (with N2O/O2) or pentobarbital, also in agreement with studies using other techniques. Magn Reson Med 46:202–206, 2001. © 2001 Wiley‐Liss, Inc.

Cerebrovascular disruption frequently results from head and neck trauma. Injury to the extra- and intracranial carotid artery is uncommon but is associated with a high rate of death and permanent neurologic deficit. In this article, injuries to the carotid artery are reviewed with emphasis on the mechanisms, clinical manifestations, radiologic evaluation, and management of these traumatic lesions.

Adenosine analogs such as 2‐chloroadenosine are potent cerebrovasodilators. Spin‐labeled MRI was used to investigate the spatial distribution, dose‐response, and timing of the effect of 2‐chloroadenosine on cerebral blood flow (CBF) after intraparenchymal injection into rat brain. Sprague‐Dawley rats (N= 10) were injected with 2‐chloroadenosine at doses of 0.3, 6.0, or 12 nmoles, or saline vehicle (2–4 μL). CBF was serially quantified in a slice through the injection site in a circular (3.6 mm diameter) region of interest (ROI) around the injection and in ipsilateral hemispheric ROIs at ∼90 min and ∼180 min. Marked 3.77‐ and 3.93‐fold increases in CBF (vs. vehicle) were seen in the circular ROI at ∼90 min and ∼180 min after 12‐nmol injection, respectively. Similarly, 2.92‐ and 2.78‐fold increases in hemispheric CBF were observed at ∼90 min and ∼180 min, respectively, after injection of 12 nmoles. Linear dose‐response relationships were observed at both times after injection in both ROIs (all P< 0.01). Spin‐labeling MRI assessment revealed that parenchymal injection of 2‐chloroadenosine produces potent, dose‐dependent, and sustained vasodilation over large areas of brain. This treatment and imaging paradigm should facilitate investigation of the effect of CBF promotion in models of traumatic and ischemic brain injury. Magn Reson Med 45:924–929, 2001. © 2001 Wiley‐Liss, Inc.

In models of focal cerebral ischemia, adenoviral gene transfer is often attenuated or delayed versus naive. After controlled cortical impact (CCI)-induced traumatic brain injury in mice, CA1 and CA3 hippocampus exhibit delayed neuronal death by 3 days, with subsequent near complete loss of hippocampus by 21 days. We hypothesized that adenoviral-mediated expression of the reporter gene β-Galactosidase (β-Gal) in hippocampus would be attenuated after CCI in mice. C57BL6 mice (n = 16) were subjected to either CCI to left parietal cortex or sham (burr hole). Adenovirus carrying the β-Gal gene (AdlacZ; 1 × 109 plaque-forming units [pfu]/mL) was then injected into left dorsal hippocampus. At 24 or 72 h, β-Gal expression was quantified (mU/mg protein). Separate mice (n = 10) were used to study β-Gal spatial distribution in brain sections. β-Gal expression in left hippocampus was similar in shams at 24 h (48.4 ± 4.1) versus 72 h (68.8 ± 8.8, not significant). CCI did not reduce β-Gal expression in left hippocampus (68.8 ± 8.8 versus 88.1 ± 7.0 at 72 h, sham versus CCI, not significant). In contrast, CCI reduced β-Gal expression in right (contralateral) hippocampus versus sham (p < 0.05 at both 24 and 72 h). β-Gal was seen in many cell types in ipsilateral hippocampus, including CA3 neurons. Despite eventual loss of ipsilateral hippocampus, adenovirus-mediated gene transfer was surprisingly robust early after CCI providing an opportunity to test novel genes targeting delayed hippocampal neuronal death.

To present a state-of-the-art review of mechanisms of secondary injury in the evolution of damage after severe traumatic brain injury in infants and children.

Platelet (P‐) selectin and intercellular adhesion molecule‐1 (ICAM‐1) mediate accumulation of neutrophils in brain. However, the mechanisms regulating neutrophil accumulation and damage after traumatic brain injury (TBI) are poorly defined. We hypothesized that mice deficient in both P‐selectin and ICAM‐1 (‐/–) would have decreased brain neutrophil accumulation and edema, and improved functional and histopathological outcome after TBI compared with wild‐type (+/+). In Protocol I, neutrophils and brain water content were quantified at 24 h after TBI. No difference in brain neutrophil accumulation was observed between groups; however, brain edema was decreased in dual P‐selectin and ICAM‐1 –/– (P< 0.05 vs. +/+ mice). In Protocol II, after TBI, tests of motor and memory function and histopathology were assessed over 21 days. No difference in motor or memory function or histopathological damage was observed between +/+ and –/– mice. A role for adhesion molecules in the pathogenesis of brain edema independent of leukocyte accumulation in brain is suggested. J. Leukoc. Biol.67: 160–168; 2000.

The bcl‐2 and caspase families are important regulators of programmed cell death in experimental models of ischemic, excitotoxic, and traumatic brain injury. The Bcl‐2 family members Bcl‐2 and Bcl‐xLsuppress programmed cell death, whereas Bax promotes programmed cell death. Activated caspase‐1 (interleukin‐1β converting enzyme) and caspase‐3 (Yama/Apopain/Cpp32) cleave proteins that are important in maintaining cytoskeletal integrity and DNA repair, and activate deoxyribonucleases, producing cell death with morphological features of apoptosis. To address the question of whether these Bcl‐2 and caspase family members participate in the process of delayed neuronal death in humans, we examined brain tissue samples removed from adult patients during surgical decompression for intracranial hypertension in the acute phase after traumatic brain injury (n=8) and compared these samples to brain tissue obtained at autopsy from non‐trauma patients (n=6). An increase in Bcl‐2 but not Bcl‐xLor Bax, cleavage of caspase‐1, up‐regulation and cleavage of caspase‐3, and evidence for DNA fragmentation with both apoptotic and necrotic morphologies were found in tissue from traumatic brain injury patients compared with controls. These findings are the first to demonstrate that programmed cell death occurs in human brain after acute injury, and identify potential pharmacological and molecular targets for the treatment of human head injury.—Clark, R. S. B., Kochanek, P. M., Chen, M., Watkins, S. C., Marion, D. W., Chen, J., Hamilton, R. L., Loeffert, J. E., Graham, S. H. Increases in Bcl‐2 and cleavage of caspase‐1 and caspase‐3 in human brain after head injury. FASEB J.13, 813–821 (1999)

Early posttraumatic cerebral hypoperfusion is implicated in the evolution of secondary damage after experimental and clinical traumatic brain injury (TBI). This is the first report of cerebral blood flow (CBF) measurement by continuous arterial spin‐labeled magnetic resonance imaging (MRI) early after TBI in rats using the controlled cortical impact (CCI) model. CCI reduced CBF globally at ∼3 hr (versus normal), with 85% and 49% reductions in a contused cortical region and contralateral cortex, respectively. In contrast, a prior MRI study from this laboratory showed at 24 hr post trauma a focal CBF reduction restricted to the injury site. In vivo spin‐lattice relaxation time (T1obs), which is used in CBF quantification, was spatially heterogeneous early after CCI, a time when edema is developing in injured brain tissue. At 4.7 T, T1obsvalues are increased 29% in the contusion (versus normal), consequently reducing CBF quantification to a similar degree. MRI should facilitate coupling posttraumatic CBF with long‐term functional outcome. Magn Reson Med 42:673–681, 1999. © 1999 Wiley‐Liss, Inc.

Early posttraumatic cerebral hypoperfusion is implicated in the evolution of secondary damage after experimental and clinical traumatic brain injury (TBI). This is the first report of cerebral blood flow (CBF) measurement by continuous arterial spin-labeled magnetic resonance imaging (MRI) early after TBI in rats using the controlled cortical impact (CCI) model. CCI reduced CBF globally at ~3 hr (versus normal), with 85% and 49% reductions in a contused cortical region and contralateral cortex, respectively. In contrast, a prior MRI study from this laboratory showed at 24 hr post trauma a focal CBF reduction restricted to the injury site. In vivo spin-lattice relaxation time (T1obs), which is used in CBF quantification, was spatially heterogeneous early after CCI, a time when edema is developing in injured brain tissue. At 4.7 T, T1obs values are increased 29% in the contusion (versus normal), consequently reducing CBF quantification to a similar degree. MRI should facilitate coupling posttraumatic CBF with long-term functional outcome. Magn Reson Med 42:673–681, 1999. © 1999 Wiley-Liss, Inc.

Poly(ADP-ribose) polymerase (PARP), or poly-(ADP-ribose) synthetase, is a nuclear enzyme that consumes NAD when activated by DNA damage. The role of PARP in the pathogenesis of traumatic brain injury (TBI) is unknown. Using a controlled cortical impact (CCI) model of TBI and mice deficient in PARP, the authors studied the effect of PARP on functional and histologic outcome after CCI using two protocols. In protocol 1, naïve mice (n = 7 +/+, n = 6 –/–) were evaluated for motor and memory acquisition before CCI. Mice were then subjected to severe CCI and killed at 24 hours for immunohistochemical detection of nitrated tyrosine, an indicator of peroxynitrite formation. Motor and memory performance did not differ between naïve PARP +/+ and –/– mice. Both groups showed nitrotyrosine staining in the contusion, suggesting that peroxynitrite is produced in contused brain. In protocol 2, mice (PARP +/+, n = 8; PARP –/–, n = 10) subjected to CCI were tested for motor and memory function, and contusion volume was determined by image analysis. PARP –/– mice demonstrated improved motor and memory function after CCI versus PARP +/+ mice (P< 0.05). However, contusion volume was not different between groups. The results suggest a detrimental effect of PARP on functional outcome after TBI.

Experimental traumatic brain injury (TBI) produces cholinergic neurotransmission deficits that may contribute to chronic spatial memory deficits. Cholinergic neurotransmission deficits may be due to presynaptic alterations in the storage and release of acetylcholine (ACh) or from changes in the receptors for ACh. The vesicular ACh transporter (VAChT) mediates accumulation of ACh into secretory vesicles, and M2receptors can modulate cholinergic neurotransmission via a presynaptic inhibitory feedback mechanism. We examined the effects of controlled cortical impact (CCI) injury on hippocampal VAChT and M2muscarinic subtype receptor protein levels at four time points: 1 day, 1 week, 2 weeks, and 4 weeks following injury. Rats were anesthetized and surgically prepared for controlled cortical impact injury (4 m/s, 2.5- to 2.9-mm depth) and sham surgery. Animals were sacrificed and coronal sections (35 μm thick) were cut through the dorsal hippocampus for VAChT and M2immunohistochemistry. Semiquantitative measurements of VAChT and M2protein in hippocampal homogenates from injured and sham rats were assessed using Western blot analysis. Immunohistochemistry showed no obvious changes in VAChT and M2immunoreactivity at 1 day and 1 week postinjury. At 2 and 4 weeks postinjury, an increase in hippocampal VAChT protein and a corresponding loss of hippocampal M2protein was observed compared to sham controls. Consistent with these results, Western blot analyses at 4 weeks postinjury demonstrated a 40–50% increase in VAChT and a 25–30% decrease in M2. These changes may represent a compensatory response of cholinergic neurons to increase the efficiency of ACh neurotransmission chronically after TBI, by upregulating the storage capacity and subsequent release of ACh and downregulating presynaptic inhibitory receptors.

THE concentrations of L-aspartate, L-glutamate, L-serine, glycine, and γ-aminobutyric acid (GABA) were determined in repeated samples of ventricular CSF from five patients with severe closed head injury. The values were compared with those obtained from five subjects undergoing surgical treatment for intractable depression. In the head-injured patients, the concentrations of aspartate, glutamate, and glycine were 2− to 8-fold higher, and the concentration of GABA 56− to 317-fold higher than control values; the concentration of serine was unaffected. Spearman correlation analysis indicated that the concentration of glutamate significantly increased after injury (Rs= 0.60, p< 0.0001, n= 42), reaching an average concentration of about 7 μM 3 days after the injury. This is probably sufficient to cause further excitotoxicity, which suggests the use of excitatory amino acid receptor antagonists as a treatment following severe head injury may require prolonged administration for maximum therapeutic benefit.

The effect of posttraumatic hypothermia (brain temperature controlled at 32°C for 4 h) on mortality after severe controlled cortical impact (CCI) was studied in rats. Four posttraumatic brain temperatures were compared: 37°C (n = 10), 36°C (n = 4), 32°C (n = 10), and uncontrolled (UC; n = 6). Rats were anesthetized and subjected to severe CCI (4.0-m/s velocity, 3.0-mm depth) to the exposed left parietal cortex. At 10 min posttrauma the rats were cooled or maintained at their target brain temperature, using external cooling or warming. Brain temperature in the UC group was recorded but not regulated, and rectal temperature was maintained at 37 ± 0.5°C. After 4 h, rats were rewarmed over a 1-h period to 37°C, extubated, and observed for 24 h. In the 37 and 36°C groups, 24-h mortality was 50% (37°C = 5/10, 36°C = 2/4). In the 32°C group, 24-h mortality was 10% (1/10). In the UC group, brain temperature was 35.4 ± 0.6°C during the 4-h treatment period and 24-h mortality was 0% (0/6). Mortality was higher in groups with brain temperatures ≥36°C versus those with brain temperatures <36°C (50 vs. 6%, respectively; p< 0.05). Additionally, electroencephalograms (EEG) were recorded in subsets of each temperature group and the percentage of time that the EEG was suppressed (isoelectric) was determined. Percentage of EEG suppression was greater in the hypothermic (32°C, n = 6; UC, n = 4) groups than in the normothermic(36°C, n = 3; 37°C, n = 6) groups (23.3 ± 14.3 vs. 1.2 ± 3.1%, respectively; p< 0.05). Posttraumatic hypothermia suppressed EEG during treatment and reduced mortality after severe CCI. The threshold for this protective effect appears to be a brain temperature <36°C. Thus, even mild hypothermia may be beneficial after severe brain trauma.

We measured CBF and CO2reactivity after traumatic brain injury (TBI) produced by controlled cortical impact (CCI) using magnetic resonance imaging (MRI) and spin-labeled carotid artery water protons as an endogenous tracer. Fourteen Sprague-Dawley rats divided into TBI (CCI; 4.02 ± 0.14 m/s velocity; 2.5 mm deformation), sham, and control groups were studied 24 hours after TBI or surgery. Perfusion maps were generated during normocarbia (Paco230 to 40 mm Hg) and hypocarbia (Paco215 to 25 mm Hg). During normocarbia, CBF was reduced within a cortical region of interest (ROI, injured versus contralateral) after TBI (200 ± 82 versus 296 ± 65 mL · 100 g−1· min−1, P< 0.05). Within a contusion-enriched ROI, CBF was reduced after TBI (142 ± 73 versus 280 ± 64 mL · 100 g−1· min−1P< 0.05). Cerebral blood flow in the sham group was modestly reduced (212 ± 112 versus 262 ± 118 mL · 100 g−1· min−1, P< 0.05). Also, TBI widened the distribution of CBF in injured and contralateral cortex. Hypocarbia reduced cortical CBF in control (48%), sham (45%), and TBI rats (48%) versus normocarbia, P< 0.05. In the contusion-enriched ROI, only controls showed a significant reduction in CBF, suggesting blunted CO2reactivity in the sham and TBI group. CO2reactivity was reduced in the sham (13%) and TBI (30%) groups within the cortical ROI (versus contralateral cortex). These values were increased twofold within the contusion-enriched ROI but were not statistically significant. After TBI, hypocarbia narrowed the CBF distribution in the injured cortex. We conclude that perfusion MRI using arterial spin-labeling is feasible for the serial, noninvasive measurement of CBF and CO2reactivity in rats.

Using a controlled cortical impact model of traumatic brain injury (TBI) coupled with tissue microdialysis, interstitial concentrations of aspartate and glutamate (together with serine and glutamine) were assessed in rat frontal cortex. Histological analysis indicated that the severity of injury following severe TBI (depth of deformation = 3.5 mm) was approximately twice that occurring following moderate TBI (depth of deformation = 1.5 mm). Both groups demonstrated significant postinjury maximal increases in excitatory amino acid (EAA) concentration, which were proportional to the severity of injury. The mean ± SEM fold increase in dialysate concentrations of aspartate was 38 ± 13 (n = 5) for moderate TBI and 74 ± 12 (n = 5) for severe TBI. Fold increases in glutamate concentrations were 81 ± 26 and 144 ± 23 for moderate and severe TBI, respectively. Although these increases normalized within 20–30 min following moderate TBI, concentrations of aspartate and glutamate took >60 min to normalize after severe TBI. Changes in levels of nontransmitter amino acids were much smaller. Fold increases for serine concentrations were 4.6 ± 0.6 and 7.6 ± 1.7 in moderate and severe TBI, respectively; glutamine concentrations had similar small fold increases (2.6 ± 0.2 and 4.1 ± 0.6, respectively). Calculation of interstitial concentrations following severe TBI indicated that aspartate and glutamate maximally increased to 123 ± 20 and 414 ± 66 μM, respectively. To determine the extent to which such tissue concentrations of EAAs could contribute to the injury seen in TBI, the EAA receptor agonists N‐methyl‐d‐ aspartate and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid were slowly injected into rat cortex. Remarkably similar histological injuries were produced by this procedure, supporting the notion that TBI is an excitotoxic injury.

A bullet, lodged in the pineal-posterior region of the third ventricle and causing obstructive hydrocephalus, was removed without damage to critical adjacent vascular structures using stereotactic localization followed by laser-guided stereotactic craniotomy. Stereotactic techniques provided precise target localization and allowed dissection to be restricted to the previously injured missile track, thus avoiding any additional morbidity from the surgical procedure.

Elevated levels of nitrates/nitrites, the stable endproducts of nitric oxide (NO), were recently observed in septic patients. In this setting, NO maintains blood flow by vasodilation and inhibition of platelet aggregation. Trauma patients were found to have low plasma levels of nitrates/nitrites, even when they developed sepsis. The current study substantiated that trauma patients have suppressed production of NO; reductions in plasma nitrate/nitrite levels correlated with low urinary excretion of these endproducts. Nitric oxide production was upregulated in trauma patients with clinical infection compared with trauma patients without infection, but was still significantly suppressed compared with nitric oxide production in normal controls. The inability of trauma patients to produce NO may be an important component of the susceptibility of these patients to infection.

Recent studies have suggested that under certain conditions, inhalation of stable xenon can cause an increase in CBF or intracranial pressure (ICP). We reviewed the ICP changes that occurred during 48 stable xenon/CT CBF studies in 23 comatose head-injured patients to determine if the concentration (32%) and duration of inhalation (4.5 min) of stable xenon we used caused an increase in ICP. In the group as a whole, there was no significant difference between the mean ICP at the start of xenon inhalation and the mean ICP immediately after completion of the studies. An increase in ICP also was not found in subgroups with low, normal, or high global CBF, or groups with or without intracranial hypertension. Changes in ICP that occurred during individual studies usually were related to corresponding changes in the arterial pco2(p < 0.0001, Pearson's correlation test). Our data suggest that 32% stable xenon administered for 4.5 min does not cause a significant increase in ICP during xenon/CT CBF studies.

We tested the hypothesis that quinolinic acid, a tryptophan-derived N-methyl-d-aspartate agonist produced by macrophages and microglia, would be increased in CSF after severe traumatic brain injury (TBI) in humans, and that this increase would be associated with outcome. We also sought to determine whether therapeutic hypothermia reduced CSF quinolinic acid after injury. Samples of CSF (n= 230) were collected from ventricular catheters in 39 patients (16 to 73 years old) during the first week after TBI, (Glasgow Coma Scale [GCS] < 8). As part of an ongoing study, patients were randomized within 6 hours after injury to either hypothermia (32°C) or normothermia (37°C) treatments for 24 hours. Oth-erwise, patients received standard neurointensive care. Quinolinic acid was measured by mass spectrometry. Univariate and multivariate analyses were used to compare CSF quinolinic acid concentrations with age, gender, GCS, time after injury, mortality, and treatment (hypothermia versus normothermia). Quinolinic acid concentration in CSF increased maximally to 463 ± 128 nmol/L (mean ± SEM) at 72 to 83 hours after TBI. Normal values for quinolinic acid concentration in CSF are less than 50 nmol/L. Quinolinic acid concentration was increased 5-to 50-fold in many patients. There was a powerful association between time after TBI and increased quinolinic acid (P< 0.00001), and quinolinic acid was higher in patients who died than in survivors (P= 0.003). Age, gender, GCS, and treatment (32°C versus 37°C) did not correlate with CSF quinolinic acid. These data reveal a large increase in quinolinic acid concentration in CSF after TBI in humans and raise the possibility that this macrophage-derived excitotoxin may contribute to secondary damage.

Intracranial and extracranial complications that occur within days or weeks after head injuries can compromise neurologic recovery if unrecognized or untreated. Common intracranial complications include infections, hematomas, and hydrocephalus. Pulmonary complications such as pneumonia, pulmonary edema, and adult respiratory distress syndrome as well as gastritis, fluid and electrolyte abnormalities, and coagulopathies are among the systemic complications that are frequently encountered. This article discusses the incidence, diagnosis, and management of these and other complications after head injuries, with emphasis on the most recent recommendations for their treatment and prevention.

Programmed cell death involves a complex and interrelated cascade of cysteine proteases termed caspases that are synthesized as inactive zymogens, which are proteolytically processed to active enzymes. Caspase‐8 is an initiator caspase that becomes activated when Fas death receptor‐Fas ligand (FasL) coupling on the cell surface leads to coalescence of a “death complex” perpetuating the programmed cell death cascade. In this study, brain tissue samples removed from adult patients during the surgical management of severe intracranial hypertension after traumatic brain injury (TBI; n=17) were compared with postmortem control brain tissue samples (n=6). Caspase‐8 mRNA was measured by semiquantitative reverse transcription and polymerase chain reaction, and caspase‐8 protein was examined by Western blot and immunocytochemistry. Fas and FasL were also examined using Western blot. Caspase‐8 mRNA and protein were increased in TBI patients vs. controls, and caspase‐8 protein was predominately expressed in neurons. Proteolysis of caspase‐8 to 20‐kDa fragments was seen only in TBI patients. Fas was also increased after TBI vs. control and was associated with relative levels of caspase‐8, supporting formation of a death complex. These data identify additional steps in the programmed cell death cascade involving Fas death receptors and caspase‐8 after TBI in humans.