Recurrent haemorrhage from a malignant brain stem glioma: a review of the mechanisms of tumoural haemorrhage.

The authors report a 23-year-old man who was diagnosed with a brain stem malignant glioma following his first episode of generalised seizure. This was subsequently complicated by three separate documented episodes of intracranial haemorrhage. The literature is reviewed and the pathophysiological mechanisms of tumoural haemorrhage are discussed. It is speculated that significant intratumoural arteriovenous shunting may lead to recurrent haemorrhages.

The role of leukocyte function-associated antigen-1 in animal models of inflammation.

Both preclinical and clinical data have identified leukocyte function-associated antigen-1 (LFA-1) as an important component of inflammatory disease states. We evaluated small molecule inhibitors of this glycoprotein in several animal models in which the inflammatory process is dependent on human or non-human primate LFA-1. (R)-5(4-bromobenzyl)-3(3,5-dichlorophenyl)-1,5-dimethylimidazolidine-2,4-dione, BIRT 377, effectively suppressed the production of human immunoglobulin (IgG) following reconstitution of severe combined immunodeficient (SCID) mice with human peripheral blood mononuclear cells. The BIRT 377 analog, BIX 642, inhibited the cellular infiltrate and increase in skin thickness associated with the delayed-type hypersensitivity reaction in previously immunized squirrel monkeys challenged with antigen. BIX 642 also inhibited the trans-vivo delayed-type hypersensitivity response in the footpads of SCID mice injected with human peripheral blood mononuclear cells and donor-sensitive antigen. These results demonstrate the efficacy of small molecule inhibitors of LFA-1 in preclinical models of inflammation dependent on human or non-human primate LFA-1.

Brain injury: the pathophysiology of the first hours.'Talk and Die revisited'.

In the 25 years since the 'Talk and Die' paper there have been substantial advances in the management of patients with severe closed head injury. This paper discusses developments in understanding of primary and secondary injury. Current management focuses on preventing secondary brain injury. That this has been successful is illustrated by a fall in mortality in recent decades. Evidence based guidelines have set standards of management but they do not take into account variations between individuals, between regions of the brain and variations with time from injury. Various monitoring techniques such as transcranial doppler, jugular venous oxygen saturation and ICP waveform analysis attempt to set individual therapeutic endpoints and to target therapy appropriately. Primary injury is no longer seen as a single irreversible event occurring at the time of impact, but rather as a process initiated by the impact and evolving over subsequent hours and days. Experimental studies have identified agents which reduce the evolution of brain injury and improve outcome. An experimental model of brain injury developed by the Adelaide He ad Injury Group identifies diffuse axonal injury as a target for therapeutic manipulation. Magnesium has been shown in other studies to improve outcome after diffuse brain injury. This has now been linked with upregulation of beta amyloid precursor prote in. Although this and several other experimental therapies have shown great promise, they have not so far produced benefit in large clinical studies. Avoiding secondary insults will remain the goal of management for the foreseeable future. Halting the evolution of the primary injury remains a highly sought after goal. Although elusive so far, it is likely to be the next major advance in clinical care.

Clostridium perfringens prototoxin-induced alteration of endothelial barrier antigen (EBA) immunoreactivity at the blood-brain barrier (BBB).

It has been reported that the severe cerebral edema produced in experimental animals by Clostridium perfringens (Cl p) type D epsilon toxin can be prevented by prior treatment with its precursor prototoxin due to competitive binding to endothelial cells (ECs) at the blood-brain barrier (BBB). In this study we investigate the effects of the prototoxin on the BBB, without added toxin. The integrity of the BBB was assessed by its ability to prevent leakage of endogenous albumin. ECs at the BBB were studied by immunocytochemistry for any alteration in the endothelial barrier antigen (EBA), a molecular marker for the intact BBB. Immunocytochemistry showed rapid but mild opening of the BBB to endogenous albumin. Light and electron immunocytochemistry showed qualitative and quantitative reduction in EBA immunoreactivity, with a spectrum of changes at time intervals from 1 h to 14 days post-prototoxin injection. Some vessels with ultrastructural changes and widening of the perivascular space retained EBA immunoreactivity. Many vessels showed partial or complete loss of EBA staining with minimal widening of the perivascular space and edema. Recovery of EBA expression was still incomplete at 14 days postinjection. This is the first report to show endothelial cell damage, mild reversible cerebral edema, and alteration in BBB markers following administration of Cl p prototoxin. This model of mild brain edema may be useful for BBB studies.

Transcranial Doppler identification of changing autoregulatory thresholds after autoregulatory impairment.

OBJECTIVE: Transcranial Doppler (TCD) flow velocity (FV) assessment may provide a useful index of autoregulatory impairment after severe head injury. It may define a therapeutic end point against which cerebral perfusion pressure (CPP) can be titrated. This study examines the relationship between cerebral blood flow (CBF) and TCD FV indices in a laboratory model before and after autoregulatory impairment. METHODS: CPP, CBF, and middle cerebral artery TCD FV were measured continuously in nine anesthetized and ventilated sheep. CPP was decreased by hemorrhagic hypotension. The process was repeated after impairment of autoregulation by cisternal infusion, which maintained CPP at 0 mm Hg for 15 minutes. Points of significant change (i.e., breakpoints) from baseline values for each of the measured flow parameters were identified by using a ratio of variance technique. RESULTS: Before any significant change in CBF or systolic TCD, diastolic TCD FV decreased (mean breakpoint, 69 mm Hg; range, 56-78 mm Hg) as CPP was reduced. This divergence of diastolic and systolic TCD FV, which occurred before autoregulatory failure, was associated with an increasing TCD pulsatility index (mean breakpoint, 63 mm Hg; range, 53-70 mm Hg). At diastolic TCD FV congruent with 10 cm/s, systolic TCD FV (mean breakpoint, 48 mm Hg; range, 46-53 mm Hg) and CBF (mean breakpoint, 49 mm Hg; range, 47-51 mm Hg) decreased rapidly, indicating autoregulatory failure. After autoregulatory impairment, the breakpoints for all four indices shifted to higher CPP values (mean, 16 mm Hg). CONCLUSION: TCD FV assessment identified two CPP thresholds of autoregulatory loss. Before autoregulatory failure, an earlier phase of autoregulatory disturbance may be detected by divergent systolic and diastolic TCD FVs. It is important to note that this phase may be detected before CBF decreases. These TCD FV breakpoints depend on the state of autoregulatory impairment and may provide potential targets for CPP-directed therapy.

Pituitary surgery complicated by haemorrhagic necrosis of residual tumour.

Haemorrhagic necrosis of residual pituitary tumour following partial excision has not previously been well described. This is differentiated from post-operative sellar haematoma due to inadequate haemostasis on the basis of absent free clot. The authors report two cases of large macroadenomas with significant supra-sellar extension which were complicated by haemorrhagic necrosis of residual tumour following initial surgery. The literature is reviewed and possible pathophysiogical mechanisms are discussed.

Upregulation of neuronal amyloid precursor protein (APP) and APP mRNA following magnesium sulphate (MgSO4) therapy in traumatic brain injury.

The aim of this study was to assess and quantitate topographically the effects of posttraumatic intravenous magnesium sulphate (MgSO4) on neuronal perikaryal APP antigen and messenger RNA (mRNA) expression in sheep brains 2 h after a controlled focal head impact. The percentage brain area with APP immunoreactive neuronal perikarya was 71, 56, 27.5 and 5.5%, respectively, in MgSO4-treated head-injured animals, head-injured animals without any treatment, MgSO4 treated nonimpacted animals, and nontreated nonimpacted control sheep. Although there was no statistically significant difference in APP immunoreactive neuronal perikarya in the MgSO4-treated HI group (mean 71%) compared to the HI group without any treatment (mean 56%), northern analysis showed that there was a 2.3-+/-0.2-fold increase in APP mRNA in the thalamus of treated impacted animals compared to untreated impacted animals (p < 0.005). However, MgSO4 treated nonimpacted control animals also showed a 1.6-+/-0.1-fold increase in APP mRNA compared to untreated nonimpacted controls (p < 0.005). MgSO4 therapy results in upregulation of neuronal APP mRNA and APP expression that is quantitatively greater following a focal head impact.

Topography and severity of axonal injury in human spinal cord trauma using amyloid precursor protein as a marker of axonal injury.

STUDY DESIGN: Axonal injury was examined in 18 human cases of acute spinal cord compression using amyloid precursor protein as a marker of AI. OBJECTIVES: To topographically map and semiquantitate axonal injury in spinal cord compression of sufficient severity to produce para- or quadriplegia. SUMMARY OF BACKGROUND DATA: Amyloid precursor protein is carried along the axon by fast axoplasmic transport and has been extensively used as a marker of traumatic axonal injury. METHODS: The study group comprised 18 cases of spinal cord compression (17 due to fracture dislocation of the vertebral column and 1 iatrogenic compression from Harrington rods) and two normal control. All the cords were examined according to a standard protocol, and at least 10 segmental levels were immunostained using a monoclonal antibody to amyloid precursor protein and immunopositive AI was semiquantitated using a grading system to provide the axonal injury severity score (AISS). The focal injury at the site of cord compression (haemorrhage, haemorrhagic necrosis, ischaemic necrosis) was also semiquantitated to provide the focal injury area score (FIAS). AI occurring around the site of focal compression (focal axonal injury severity score or FAISS) was distinguished from AI distant to the focal injury (nonfocal axonal injury severity score or NFAISS). RESULTS: All 18 cases showed widespread amyloid precursor protein immunoreactive axonal injury and the AISS ranged from 28 to 60%. In all cases, the FAISS was greater than the NFAISS and there was a statistically significant relationship between the AISS and the FIAS. CONCLUSION: Acute spinal cord compression of sufficient severity to produce permanent paralysis causes widespread axonal damage that is maximal at the site of compression but also present throughout the length of the cord in segments far distant from the site of the focal injury.

Toxin-induced vasogenic cerebral oedema in a rat model.

Vasogenic cerebral oedema (VCO) was induced in Hooded Wistar rats by intraperitoneal injection of Clostridium perfringens type D epsilon prototoxin. Animals were killed, 1 h to 14 d postinjection, by perfusion fixation under general anaesthesia. VCO was detected by the presence of endogenous albumin in the brain, visualised by immunocytochemistry. As early as 1 h postinjection, albumin was detected in the walls of cerebral microvessels. Maximal diffuse leakage within the neural parenchyma was seen at 24 and 48 h and immunoreactivity was still present at 4 d. At 7 d only few foci were seen, and at 14 d albumin distribution was similar to that in controls. Ultrastructural assessment of the microvessels showed swelling of many astrocytic processes and abnormalities of the endothelial cells varying from swelling with loss of cytoplasmic organelles to cells showing increased electron density. Immunostaining for the endothelial barrier antigen (EBA) showed strongly immunoreactive vessels throughout normal brains. Experimental animals showed partial reduction in EBA expression, most evident at 24 and 48 h, with gradual recovery to normal by 14 d. The exact role that EBA plays in the intact BBB remains obscure.

Cutting edge: a small molecule antagonist of LFA-1-mediated cell adhesion.

LFA-1 (CD18,CD11a) is a cell-adhesion molecule that mediates critical immunological processes. In this paper we report the discovery and characterization of (R)-5-(4-bromobenzyl)-3-(3, 5-dichlorophenyl)-1,5-dimethylimidazolidine-2,4-dione (BIRT 377), an orally bioavailable small molecule that interacts specifically with LFA-1 via noncovalent binding to the CD11a chain and prevents LFA-1 from binding to its ligand, ICAM-1. BIRT 377 inhibits lymphocyte activity both in vitro and in vivo, in functional assays that require LFA-1-mediated cell adhesion. These results demonstrate that LFA-1-mediated leukocyte adhesion can be antagonized with noncharged, low m.w. molecules and suggest that the potential therapeutic value of adhesion inhibitors can be attained with a small, orally bioavailable compound.

Upregulation of amyloid precursor protein messenger RNA in response to traumatic brain injury: an ovine head impact model.

There is evidence that the amyloid precursor protein (APP) plays an important role in neuronal growth and synaptic plasticity and that its increased expression following traumatic brain injury represents an acute phase response to trauma. We hypothesized that the previously described increased APP expression in response to injury (Van den Heuvel et al., Acta Neurochir. Suppl. 71, 209-211) is due to increased mRNA expression and addressed this by examining the expression of APP mRNA and APP within neuronal cell bodies over time in an ovine head impact model. Twenty-five anesthetized and ventilated 2-year-old Merino ewes sustained a left temporal head impact using a humane stunner and 9 normal sheep were used as nonimpact controls. Following postimpact survival periods of 15, 30, 45, 60, and 120 min, brains were perfusion fixed in 4% paraformaldehyde and examined according to standard neuropathological protocol. APP mRNA and antigen expression were examined in 5-microm sections by nonisotopic in situ hybridization and APP immunocytochemistry. The percentage of brain area with APP immunoreactivity within neuronal cell bodies in the impacted animals increased with time from a mean of 7.5% at 15 min to 54.5% at 2 h. Control brains showed only very small numbers of weakly APP-positive neuronal cell bodies ranging from 2 to 14% (mean 7%). Increased expression of APP mRNA was first evident in impacted hemispheres at 30 min after impact and progressively increased over time to involve neurons in all sampled regions of the brain, suggesting increased transcription of APP. In contrast, APP mRNA was undetectable in tissue from nonimpacted sheep. These data show that APP mRNA and antigen expression are sensitive early indicators of neuronal injury with widespread upregulation occurring as early as 30 min after head impact.

Transcranial Doppler assessment of the lower cerebral autoregulatory threshold.

Continuous transcranial Doppler ultrasonography of the middle cerebral artery (TCD-MCA) has been proposed as a method of identifying the lower cerebral autoregulatory threshold. This study investigated the relationship between continuous TCD-MCA and cerebral blood flow (CBF) in sheep. Arterial blood pressure, intracranial pressure, CBF and left TCD-MCA were measured in 12 anaesthetized and ventilated merino sheep. Cerebral perfusion pressure (CPP) was reduced by haemorrhagic hypotension. Measurements were recorded continuously and breakpoint thresholds calculated by an analysis of variance. The TCD-MCA systolic velocity breakpoint (50 +/- 1.5 mmHg) did not significantly differ from the lower limit of autoregulation, identified by the CBF breakpoint (50 +/- 1.8 mmHg). The TCD-MCA diastolic velocity breakpoint occurred at a significantly higher level of CPP (64 +/- 2 mmHg) (P < 0.01). The relationship between TCD-MCA flow velocity and CBF thresholds has been described. Early divergence of flow velocity may represent a compensatory mechanism to maintain CBF.

Widespread early dendritic injury associated with loss of cortical MAP-2 immunostaining in a focal ovine head impact model.

Dendritic pathology associated with traumatic brain injury may be identified by microtubule associated protein-2 (MAP-2) immunohistochemistry. The aim of this study was to examine the dendritic response in the cerebral cortical mantle in an ovine head impact model using MAP-2 immunostaining as a marker for dendritic injury. The loss of cortical MAP-2 immunoreactivity at 2 h was recorded and quantitated using a computerised image analysis system applied to standard coronal brain sections obtained from 10 impacted and 3 control sheep. Coup and contrecoup cortical contusions were present in 9 of 10 impacted brains examined 2 h after injury. MAP-2 immunoreactivity was lost in all areas of cortical contusion irrespective of site and in otherwise histologically normal cortex. MAP-2 immunostaining was lost in over 45% of the whole cortical area (range 32-54%) and only 2% (range 0-5.5%) was associated with contusions. This study has shown that there is widespread loss of MAP-2 immunostaining following head impact in the cerebral cortical mantle (up to 54%) suggestive of early dendritic injury.

Widespread axonal injury in gunshot wounds to the head using amyloid precursor protein as a marker.

In order to determine whether axonal injury (AI) is a factor in cases of penetrating head injury, the brains of 14 patients who died shortly after sustaining a fatal gunshot wound (GSW) to the head were examined, and the presence of AI determined using immunohistochemical staining for amyloid precursor protein (APP). The distribution of AI was mapped throughout the cerebral hemispheres and brain stem. AI was present in all cases in a diffuse distribution distant to the missle track with severe involvement of the brain stem in all cases. There was no axonal APP immunoreactivity in the direct region of the missle track at the point of primary axotomy. The APP-positive AI in these cases is likely to be a mixture of primary and secondary AI as APP immunostaining is unable to distinguish primary AI due to mechanical deformation from AI secondary to hypoxic-ischemic damage.

Distal anterior cerebral artery aneurysms: a clinical series.

Thirty patients with distal anterior cerebral artery (DACA) aneurysms were seen at the Royal Adelaide Hospital in the period 1970-1996. There were seven males (23%) and twenty three females (77%) with a mean age of 50 years. The average follow up was 5 years. Multiple aneurysms were present in seven cases (23%). The mean size of aneurysms was 5 mm. There were two post-traumatic aneurysms and one mycotic aneurysm. Out of the 30 cases, 19 presented with subarachnoid haemorrhage from ruptured DACA aneurysms. Eight (42%) of them were in good clinical grade (I or II). Operations were carried out in 25 (83%) patients. All five cases with unruptured aneurysms and the eight patients with good clinical grade had good recovery. In contrast, only six (55%) out of 11 patients with poor clinical grade had good outcome. The overall management mortality for the 19 cases with ruptured aneurysms was 16%. Postoperative complication occurred in two cases (8%), one patient developed deep vein thrombosis and seizures, the other patient had transient upper limb weakness. Although there is a definite trend towards better management outcome in the published series of DACA aneurysms over the years, there is still significant mortality and morbidity in the poor grade patients. Early surgery will prevent the deaths from rebleeding and may allow optimal management of vasospasm.

Progress in head injury management.

Preventable secondary injury remains disturbingly common and can only be reduced by highly organized and integrated services, and careful and continuous monitoring. Continuous non- or relatively non-invasive bedside monitoring of factors closely related to brain metabolism and function is becoming a practical reality. To the extent that the complex changes initiated by traumatic brain injury are 'processes' rather than 'events' it may become possible for components of injury to be halted or reversed. Pharmacological therapy given early after injury may be able to reduce the harmful events initiated by the injury. Head injury management is multidisciplinary. Improvements in head injury outcome have come about through better organisation of services - efficient retrieval, early investigation and removal of clots, and management in experienced intensive care units. Australian neurosurgeons have played a leading role in defining standards of care, in organizing services and in raising public health issues related to head injury. With the increasing and necessary involvement of other specialists and the greater dependence on technically demanding intensive monitoring and medical management, it is important that neurosurgeons remain at the forefront of the care of patients with head injury and not simply be reduced to managing the surgical complications on request.(86).

Effect of deoxycoformycin and Val-boroPro on the associated catalytic activities of lymphocyte CD26 and ecto-adenosine deaminase.

CD26 and ecto-adenosine deaminase (ADA) are found associated on the plasma membrane of T lymphocytes and each possess distinct catalytic activities. CD26 has a proteolytic activity identical to dipeptidylpeptidase IV (DPPIV; E.C. 3.4.14.5), and ecto-ADA (E.C. 3.5.4.4) degrades extracellular adenosine. The cell surface expression of CD26 and ecto-adenosine deaminase (ecto-ADA) is regulated on stimulated T lymphocytes, and ADA binding to CD26 produces a synergistic costimulatory response with T cell receptor activation. This study addresses the potential regulation by allosteric interactions of the catalytic activities of CD26 associated with ecto-ADA, which could define the mechanism of the synergism observed in T cell signaling. Cell lines genetically deficient in ADA, ligands for ADA such as adenosine, and a specific inhibitor of ADA, deoxycoformycin, were used to define the effect of ADA activity on CD26 DPPIV activity and affinity for dipeptide substrate. Conversely, a recombinant Chinese hamster ovary cell line expressing human CD26 with or without a mutation in the DPPIV catalytic domain, and the boronic acid inhibitor Val-boroPro, were used to determine the effect of DPPIV activity on ecto-ADA activity and association with CD26. These studies found no significant allosteric interaction between the catalytic activities of CD26 and ecto-ADA when associated. Therefore, signaling events in T cells involving costimulation with CD26 and ecto-ADA and the synergism observed upon ADA binding to CD26 occur independently of the catalytic activities of these cell surface molecules.

A head impact model of early axonal injury in the sheep.

Axonal injury (AI), one of the principal determinants of clinical outcome after head injury, may evolve over several hours after injury, raising the future possibility of therapeutic intervention during this period. A new head impact model of AI in sheep was developed to examine pathological and physiological changes in the brain resulting from a graded traumatic insult. In this preliminary study 10 anesthetized and ventilated Merino ewes were used. Head injury was produced by impact from a humane stunner to the temporal region of an unrestrained head. Eight sheep were studied for 1, 2, 4, or 6 h after impact. Two sham animals (no impact, 6 h survival) were also examined. Arterial blood pressure, intracranial pressure, and cerebral blood flow were monitored continuously. A physiological index of injury severity was calculated by weighting the percentage shift from preinjury values for each monitored parameter over the first hour after injury. Immunostaining with amyloid precursor protein (APP) was used as a marker of axonal damage and the distribution of APP positive axons was recorded according to a sector scoring method (APPS). Widespread AI was identified in 7 of the 8 impacted animals, around cerebral contusions and in hemispheric white matter, central gray matter, brain stem, and cerebellum, and was detected as early as 1 h after injury. The degree of axonal injury (APPS) correlated well with an index of physiological response to injury (r = 0.83, p = 0.005).