Journal of Neurotrauma

The complement cascade has been suggested to be involved in the development of secondary brain injuries following brain contusions, based on animal experiments. The aim of the present study was to examine the possible involvement of the complement cascade following traumatic head injury in the human brain. Sixteen patients were included in this study, 12-77 years of age, treated at the neurointensive care unit for traumatic brain contusions. All of these patients were operated with frontal or temporal lobe resection due to intractable intracranial hypertension. The resected tissue was analyzed with regard to components related to complement activation. The time interval between accident and operation was 2-82 h. Brain tissue from three patients operated with hippocampectomy due to epilepsy, including temporal lobe resection, were used as controls. We found increased immunoreactivity for complement components C1q, C3b, and C3d and the membrane attack complex (MAC), C5b-9, in the immediate vicinity of neurons in the penumbra area of the contusion. These findings constitute histological evidence for activation of the complement cascade in the penumbra of cortical contusions in the human brain. Using in situ hybridization, we also found C3-mRNA in the penumbra, suggesting a local synthesis of complement. Furthermore, upregulation of the endogenous complement regulator clusterin was found in some neurons in the same area. We suggest that unknown compounds in the debris from injured neurons or myelin breakdown products trigger complement activation, including formation of C5b-9. Activated complement components may stimulate accumulation of inflammatory cells and formation of brain edema, as well as having membrane destructive effects by the end product MAC, thereby being mediators in the development of secondary brain damage.

Repinotan is a high-affinity, selective, full agonist of the 5HT_1A-receptor subtype with neuroprotective properties. This paper presents the results of a randomized, double-blind, placebo-controlled study examining the safety and tolerability of three different doses of repinotan in patients with severe traumatic brain injury. Sixty patients were enrolled to receive repinotan (0.5, 1.25, or 2.50 mg/day) or placebo, by continuous i.v. infusion for 7 days. Repinotan treatment had no apparent adverse effects on intracranial pressure, hemodynamic parameters or laboratory parameters. No seizures occurred during treatment, and the incidence and severity of adverse events was as expected for this indication. No serious adverse events were considered related to drug treatment, with the possible exception of one case of inappropriate ADH secretion. No further safety concerns were raised during the 3 months following treatment. On a descriptive basis, the proportion of patients having good outcome or moderate disability(Glasgow Outcome Scale) was somewhat greater in repinotan-treated patients (60%) than in placebo (50%).

Transient amnesia caused by minor head injury is commonly encountered in daily neurosurgical practice, but the mechanism of such amnesia has not been extensively studied. We measured the regional cerebral blood flow (rCBF) of patients with postconcussive amnesia with Xe/CT CBF to examine whether a focal disturbance of CBF exists. The Xe/CT CBF study was performed in eight patients with closed head injury without organic cerebral lesion while they were suffering from posttraumatic amnesia (concussion group). The time interval between accident and CBF measurement was less than 2 h in three patients, 5–6 h in two, 8–9 h in two, and 18 in one. The results were compared with those of nine normal volunteers and eight other age-matched patients who recovered without any neurological deficit despite the presence of hemorrhagic regions (mild hemorrhage group). The rCBF of the concussion group was significantly elevated in the bilateral mesial temporal cortex in comparison to the normal group. The rCBF in the mild hemorrhage group was lower than that of normal controls in all regions. The analysis of right–left difference in CBF indicated that there was significant asymmetry (right > left) in the frontal and temporal cortex in the concussion group, but not in the normal and mild hemorrhage group. This Xe/CT CBF study in acute stages of cerebral concussion, in which patients were amnestic, detected focal cerebral hyperemia. Such hyperemia in regions closely related to human memory function may be the result of vasoparalysis or the compensatory activation of memory circuits after denervation injury.

Apoptosis of brain cells is triggered by traumatic brain injury (TBI) and is blocked by caspase inhibitors. The neuronal apoptosis inhibitor protein (NAIP), which has been shown to inhibit apoptosis by both caspase-dependant and caspase-independent mechanisms, is neuroprotective in rat models of cerebral ischemia and axotomy. In order to gain a better appreciation of CNS apoptosis following head injury in general and the possible involvement of NAIP specifically, we have configured a mouse model of TBI. In addition to demonstrating apoptosis, the spatiotemporal expression or levels of a number of proteins with apoptosis modulating effects have been determined. Apoptosis of neurons and oligodendrocytes following TBI was observed in brain sections which were triple-stained with in situ end labeling, bisbenzimide and immunofluorescent stain for neuron specific nuclear protein and myelin-associated glycoprotein, respectively. Further evidence for apoptosis following TBI in this model was obtained in brain samples using ligation-mediated PCR amplification of DNA fragments and gel electrophoresis. The temporal profile of apoptosis was similar to the temporal profile of microglial activation determined by CD11b staining and TNF α expression induced by TBI. NAIP staining in sections of cerebral cortex and subcortical white matter increased at 6 h and decreased towards control levels at 24 h post-TBI. Temporal changes in the expression of NAIP were also observed using Western blot analysis of brain samples removed from injured cortex and sub-cortical white matter. At the time that NAIP expression decreased markedly (24 h post-TBI), procaspase-3 levels also decreased, PARP cleavage increased, and the highest levels of apoptosis were observed. These findings have implications in our understanding of traumatically induced programmed cell death and may be useful in the configuration of therapies for this common injury state.

Epidural mass lesions may cause ischemia due to progressive intracranial hypertension. In order to investigate the impact of intracranial pressure on accumulation of neuroactive substances, we gradually raised intracranial pressure in five halothane anesthetized cats by inflation of an epidural balloon. We evaluated in the parietal cortex contralateral to the site of balloon inflation, alterations of extracellular glutamate and purine catabolites and of the lactate/pyruvate ratio in relation to changes of intracranial, cerebral perfusion and mean arterial blood pressure. In a complementary experiment, regional cerebral blood flow was assessed by sequential positron emission tomography. In this simplified mass lesion model, extracellular glutamate increased in all cats at a late, critical stage after tentorial herniation, when intracranial pressure had increased to more than 90 mm Hg, cerebral perfusion pressure had decreased below 40–50 mm Hg. Positron emission tomography assessments revealed that the ischemic threshold for glutamate accumulation was in the range of 15–20 mL/100 g/min. Purine catabolites and the lactate/pyruvate ratio increased somewhat earlier than glutamate, but also after reaching the critical, terminal stage. We conclude that in this model of progressive epidural compression, glutamate-mediated excitotoxic processes at sites remote from the initial focal lesion depend on processes such as delayed ischemia in combination with tentorial herniation and systemic hypotension. These processes seem to be initiated by a decrease of cerebral perfusion pressure below a threshold of 40–50 mm Hg.

Management of cerebral perfusion pressure (CPP) is thought to be important for the treatment of traumatic brain injury (TBI). Vasopressors have been advocated as a method of increasing mean arterial blood pressure (mABP) and cerebral perfusion pressure (CPP) in the face of rising intracranial pressure (ICP). There are unresolved issues and theoretical risks about this therapy. This study therefore examined the effects of dopamine on physiological and MRI/MRS parameters in (1) a rodent model of rapidly rising intracranial pressure, caused by diffuse injury with secondary insult and (2) a model of cortical contusion. Dopamine was capable of restoring CPP in the model of rapidly rising ICP. This CPP restoration was associated with a partial restoration of CBF. Two profiles of change in the Apparent Diffusion Coefficient of water (ADC_W) were seen; one in which ADC_W recovered to baseline, and one in which ADC_W remained persistently low. Dopamine did not alter these profiles. MRI assessed tissue water content was increased four hours after injury and dopamine increased cerebral water content in both subgroups of injury; significantly in the group with a persistently low ADC_W(p < 0.01). In contusional injury, dopamine significantly worsened edema in both the ipsi- and contralateral hippocampus and temporal cortex. This occurred in the absence of ADC_W changes, except in the contralateral hippocampus, where both water content and ADC_W values rose with treatment, suggesting extracellular accumulation of water. In conclusion, although dopamine is capable of partially restoring CBF after injury, situations exist in which dopamine therapy worsens the swelling process. It is possible therefore that subgroups of patients exist who experience adverse effects of vasopressor treatment, and consequently the effects of vasopressor therapy in the clinical setting need to be more carefully evaluated.

Alterations in the hypothalamo-pituitary-adrenal (HPA) axis following traumatic brain injury have not been documented in detail. We used fluid percussion injury (FPI) to evaluate the early changes in components of the HPA axis following experimental traumatic brain injury. Wistar rats were sacrificed at 2 or 4 h following sham or FPI surgery. In situ hybridization histochemistry was used to determine the expression of mRNAs of corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) in the hypothalamus and pro-opiomelanocortin (POMC) in the pituitary. A group of animals undergoing no surgery were used as control. Repeated blood sampling from an indwelling catheter demonstrated that plasma corticosterone (CORT) levels peaked 30 min following surgery in sham and FPI animals but there was no significant difference in CORT concentration between these groups at any time. Pituitary POMC expression was increased following sham and FPI surgery (compared with control non-operated animals) but with no significant difference between the two groups undergoing surgery. Hypothalamic CRH mRNA expression was significantly higher in animals undergoing FPI compared with sham surgery. Hypothalamic AVP mRNA expression was not significantly increased when compared with control nonoperated animals. These data indicate that the anaesthesia and/or surgery associated with FPI or sham surgery induces a generalised activation of the HPA axis. The selective increase in CRH mRNA in animals undergoing FPI may be due to specific effects of traumatic brain injury rather than a general stress response and may suggest an additional neurotransmitter role for CRH following head injury. The absence of an AVP response suggests that the effects of FPI may be mediated through the CRH-alone-containing subpopulation of neurons.

Although human infants suffer traumatic spinal cord injury, appropriate animal models have not been developed. The consequences of neonatal injury are not necessarily the same as in adults, so treatments designed for adults may not generalize to infants. Therefore, understanding the effects of traumatic injury to the developing cord is important. In this experiment, mid-thoracic spinal cords of 4-day-old rats were compressed with forceps by 0% (sham), 90% or 95% of the uncompressed width. On postoperative day (POD) 1 or 11, rats were suspended in harnesses and administered L-DOPA to activate locomotor circuits. Slight modifications of interlimb coordination remained on POD 11 following the lesser compression, whereas the amount of hindlimb air-stepping, step rates, step lengths and coordination were reduced and declined post-operatively following the greater compression. Lesions were proportional to severity of compression. Progressive motor dysfunction during air-stepping revealed deficits in descending control of lumbar circuits, whereas previous reports of recovery of overground walking probably reflect activation of reflex mechanisms caudal to the transection.

This paper describes a modification of a balloon-compression technique to produce spinal cord injury in adult rats. A 2-French Fogarty catheter is inserted into the dorsal epidural space through a small hole made in T10 vertebral arch, advanced cranially to T8-9 spinal level, and inflated for 5 min. Spinal cord damage is graded by increasing the volume of saline used to inflate the balloon. Quantitative neurological and histopathological outcomes are presented with three different volumes (10, 15, and 20 μl of saline) to characterize the gradation of injury. Volume of 15 μ l produced complete paraplegia followed by gradual recovery, finally reaching approximately the middle of the scale used to quantitate the locomotor performance. With these animals, after 4 weeks, the center of the lesion shows complete loss of grey matter and partial sparing of the white matter. We conclude that 15 μl volume produced submaximal injury that will be useful for studying the pathophysiology and effects of protective therapies with this compression-injury model.