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[Blood-brain barrier pathophysiology and ischaemic brain oedema].

Cerebral oedema is a potentially lethal complication of brain infarction. Ischemia, by altering membrane ionic pump function, induces cell swelling and cytotoxic oedema. It also initiates early oxidative and inflammatory cascades leading to blood-brain barrier disruption, vasogenic oedema and haemorrhagic transformation. The mechanisms of blood-brain barrier disruption involve endothelial cell activation and endothelial basal membrane degradation by matrix metalloproteinases. Reperfusion by tissue plasminogen activators is the only treatment improving stroke prognosis. This treatment also increases vasogenic oedema and the risk of symptomatic haemorrhagic transformation, reducing the benefit of reperfusion. Experimental studies suggest that the inhibition of blood-brain barrier proteolysis reduces vasogenic oedema and the risk of haemorrhage. This recent progress in the understanding of blood-brain barrier disruption during ischaemia brings forward new therapeutic strategies using agents capable of interfering with the ischaemic cascade in order to increase the therapeutic window between the onset of ischaemia and thrombolytic reperfusion.

Blood-Brain Barrier↗

Dose-dependent neuroprotection with tiagabine in a focal cerebral ischemia model in rat.

Enhancement of the inhibitory activity of GABA may protect ischemic neurons. We evaluated the neuroprotective effect of tiagabine, a novel GABA agonist, in reversible focal cerebral ischemia rats subjected to 2h middle cerebral artery (MCA) occlusion. Tiagabine was given at 10, 20 and 40 mg/kg, i.p., 2 h after the onset of reperfusion. We found that post-ischemia treatment with tiagabine improved neurobehavioral outcome and reduced brain infarction volume in a dose-dependent manner. The data suggest that post-ischemic administration of tiagabine is neuroprotective in the focal cerebral ischemia model.

Animals↗

Cerebrovascular complications in cancer patients.

The clinician should be alert to the possibility of cerebrovascular disease in cancer patients who develop signs of diffuse or focal cerebral dysfunction. The cause of cerebrovascular disease can usually be determined by knowing the primary tumor type, extent of metastatic disease, and type of antineoplastic treatment. Symptomatic infarctions are more common than hemorrhages in patients with carcinoma, and NBTE and cerebral intravascular coagulation are the most common causes of infarction. Brain hemorrhages in patients with carcinoma are usually from hemorrhage into metastatic tumor. Symptomatic hemorrhages are much more common than infarction in patients with leukemia, and hemorrhages may be caused by coagulopathy or central nervous system infiltration. Infarction in leukemia is usually due to septic embolism or intravascular coagulation. By determining the cause of cerebrovascular disease in the cancer patient, the clinician can often recommend appropriate treatment and predict the clinical outcome.

Brain Neoplasms↗

Diagnosis and management of vascular cognitive impairment and dementia.

Vascular dementias (VaDs) are the second most common cause of dementia. Cerebrovascular disease (CVD) and stroke relates to high risk of cognitive impairment, but also relate to Alzheimer's disease (AD): Vascular cognitive impairment (VCI) and dementias extend beyond the traditional multi-infarct dementia. Pathophysiology of VaD incorporates interactions between vascular etiologies (CVD and vascular risk-factors), changes in the brain (infarcts, white matter lesions, atrophy), host factors (age, education) and cognition. Variation in defining the cognitive syndrome, in vascular etiologies, and allowable brain changes in current criteria have resulted in variable estimates of prevalence, of groups of subjects, and of the types and distribution of putative causal brain lesions. Should new criteria be developed? Ideally in constructing new criteria the diagnostic elements should be tested with prospective studies with clinical-pathological correlation: replace dogma with data. Meanwhile focus on more homogenous subtypes of VaD, and on imaging criteria could be a solution. Subcortical ischemic vascular disease and dementia (SIVD) incorporate small vessel disease as the chief vascular etiology, lacunar infarct and ischaemic white matter lesions as primary type of brain lesions, subcortical location as the primary location of lesions, and subcortical syndrome as the primary clinical manifestation. It incorporates two clinical entities "Binswanger's disease" and "the lacunar state". AD with VaD (mixed dementia) has been underestimated as a prevalent cause in the older population. In addition to simple co-existence, VaD and AD have closer interaction: several vascular risk factors and vascular brain changes relate to clinical manifestation of AD, and they share also common pathogenetic mechanisms. Vascular cognitive impairment (VCI) is a category aiming to replace the "Alzhemerized" dementia concept in the setting of CVD, and substitute it with a spectrum that includes subtle cognitive deficits of vascular origin, post-stroke dementia, and the complex group of the vascular dementias. As far there is no standard treatment for VaDs, and still little is known on the primary prevention (brain at risk for CVD) and secondary prevention (CVD brain at risk for VCI/VaD). There is no standard symptomatic treatment for VaD. Recently symptomatic cholinergic treatment has shown promise in AD with VaD, as well as probable VaD. Future focus should be directed to the distinct etiological and pathological factors: the vascular and the AD burden of the brain.

Alzheimer Disease↗

Transient ischemic attack: definition and natural history.

The standard definition of a transient ischemic attack--"a cerebral dysfunction of an ischemic nature lasting no longer than 24 hours with a tendency to recur"--was arrived at arbitrarily and is no longer tenable. Experience shows that attacks are much briefer, usually less than an hour, and many are associated with brain infarction. A newer definition, more consonant with the data, is preferred--"transient ischemic attack is a brief episode of neurological dysfunction caused by focal brain or retinal ischemia, with clinical symptoms typically lasting less than an hour, and without evidence of acute infarction." Patients with transient ischemic attacks require urgent evaluation that includes brain and vascular imaging, blood tests, and often cardiac investigations. Treatment will depend on the nature of the causative cervico-cranial vascular, cardiac, and hematologic abnormalities found on investigation.

Humans↗

The complications of migraine with aura.

Migraine with aura is a common disorder in industrialised countries, affecting up to 5% of the adult population. Although migraine aura is usually a benign disorder, in rare instances it can be the cause of serious neurologic complications. The most common is migrainous stroke, defined as a persistent neurologic deficit following the aura with evidence of brain infarction at neuroimaging and lack of alternative explanations. The most likely pathogenic mechanism is brain ischaemia induced by cortical spreading depression, but other possibilities, such as intracranic arterial dissection or embolism through patent foramen ovale need to be considered. Other complications are migraine-related seizures, which are probably caused by neuronal hyperexcitability in migraineurs, and persistent auras without infarction. These disorders are of both clinical and scientific interest, as they throw light on the complex and not yet fully understood relationship between migraine with aura, stroke and epilepsy.

Epilepsy↗

The electroencephalogram and acute ischemic stroke. Distinguishing cortical from lacunar infarction.

One hundred consecutive cases of clinically diagnosed, acute forebrain infarction were studied using computerized tomography (CT) and electroencephalography (EEG). Computed tomography confirmed brain infarction in 91 patients and was normal in the remaining nine. Each EEG was read independently by two experienced electroencephalographers without knowledge of CT or clinical details and their findings were compared with those of CT. Lateralized theta and/or delta activity predicted ipsilateral cortical infarction with a sensitivity of 76% and specificity of 82%. In contrast, cerebral hemisphere lacunae produced similar EEG abnormalities in only a few cases (9%). Electroencephalography is particularly useful following stroke if the initial CT excludes hemorrhage but does not detect infarction. In conjunction with clinical details, the EEG can then be used to indicate the likelihood of cortical involvement and thus suggest the likely pathophysiologic mechanism of infarction.

Acute Disease↗

Clinical implications for the management of acute thromboembolic occlusion of the superior mesenteric artery: autopsy findings in 213 patients.

OBJECTIVE: To study findings at autopsy in patients with fatal acute thromboembolic occlusion of the superior mesenteric artery (SMA). SUMMARY BACKGROUND DATA: Acute occlusion of the SMA is difficult to diagnose and mortality remains high. In Malmo, Sweden, the autopsy rate between 1970 and 1982 was 87%, creating possibilities for a population-based study. METHODS: Among 23,496 clinical autopsies and 7569 forensic autopsies, 213 cases with acute thromboembolic occlusion of the SMA and intestinal infarction were identified. RESULTS: A clinical suspicion of intestinal infarction was documented in 32% of the patients, only 35% being in the care of surgeons. The embolus/thrombus ratio was 1.4 to 1. Thrombotic occlusions were located more proximally than embolic occlusions (P < 0.001), intestinal infarction was more extensive (P = 0.025) and thrombotic occlusions were associated with old brain infarction (P = 0.048), aortic wall thrombosis (P = 0.080), and disseminated cancer (P = 0.079). Patients with embolic occlusions (n = 122) had a higher frequency of acute myocardial infarction (AMI) than patients with thrombotic occlusions (P = 0.049). The embolic source was identified in 80%. In 115 (94%), synchronous embolism and/or source of embolus were present. There were findings of remaining cardiac thrombi in 58 (48%) and synchronous emboli affected 273 other arterial segments in 83 (68%). CONCLUSIONS: Early recognition and revascularization would have been a prerequisite for survival in at least half of the patients, since the jejunum, ileum, and colon were affected by infarction. A minority of all patients were under surgical care. AMI, cardiac thrombi, and synchronous emboli were common findings among patients with embolic occlusions.

Acute Disease↗

Hydrogen ions kill brain at concentrations reached in ischemia.

Elevation of brain glucose before the onset of nearly complete ischemia leads to increased lactic acid within brain. When excessive, such acidosis may be a necessary factor for converting selective neuronal loss to brain infarction from nearly complete ischemia. To examine the potential neurotoxicity of excessive lactic acid concentrations, we microinjected (0.5 microliter/min) 150 mM sodium lactate solutions (adjusted to 6.50-4.00 pH) for 20 min into parietal cortex of anesthetized rats. Interstitial pH (pH0) was monitored with hydrogen ion-selective microelectrodes. Animals were allowed to recover for 24 h before injection zones were examined with the light microscope. Injectants produced brain necrosis in a histological pattern resembling ischemic infarction only when pH0 was less than or equal to 5.30. Nonlethal injections showed only needle tract injuries. Abrupt deterioration of brain acid-base homeostatic mechanisms correlated with necrosis since pH0 returned to baseline more slowly after lethal tissue injections than after nonlethal ones. The slowed return of pH0 to baseline after the severely acidic injections may reflect altered function of plasma membrane antiport systems for pH regulation and loss of brain hydrogen ion buffers.

Acidosis↗

Wallerian degeneration of the descending tracts. CT and MRI features of the brain stem.

The authors have studied by CT brain infarcts of different ages in 16 patients, two of whom were also examined by MRI. The early and CT signs of wallerian degeneration of the descending tracts within the brain stem are described. Three cases of crossed cerebellar atrophy are reported; in one of them, the cerebral lesion had been present for less than 8 years. The physiopathology of pontine hemiatrophy and crossed cerebellar atrophy is discussed.

Adolescent↗

Classification and mechanisms of cerebrovascular disease.

Infarction remains the cause of stroke in 75 to 80% of patients. The leading cause is embolism from one of several sources, although the source of the particles is often not discovered despite prolonged search. Brain infarction associated with high-grade stenosis or occlusion of major arteries may also be caused by local embolism but in one-third of patients, the process of infarction seems attributable to perfusion failure, with a more leisurely evolution of the syndrome than that typical of embolism. Lacunar disease accounts for roughly 20% of strokes.

Brain Ischemia↗

Cerebrospinal fluid homovanillic acid in cerebral infarction.

Cerebrospinal fluid (CSF) homovanillic acid (HVA) concentration was measured in 39 consecutive cases of hemispheric infarction, 7 cases of brainstem infarction, and in 16 controls. The CSF-HVA level was 38 +/- 15 ng/ml (mean +/- S.D.) in the control patients, 15 +/- 6 ng/ml in patients with brainstem infarcts, and 49 +/- 41 ng/ml in those with hemispheric infarcts. The CSF-HVA levels were decreased in brainstem infarct cases (p less than 0.001) and greatly scattered in patients with hemispheric infarcts (range 4--207 ng/ml) when compared to controls. The decrease of levels of CSF-HVA in brainstem infarct cases may reflect interference with the dopaminergic pathways. CSF-HVA values in hemispheric infarction could not be related to the acuteness, location, nor severity of the lesion. The broad range of CSF-HVA values may be due to the interaction of multiple, as yet unknown factors. These findings suggest that dopamine metabolism is altered in many cases with acute brain infarction.

Adolescent↗

Effect of the serotonin antagonist ketanserin on the hemodynamic and morphological consequences of thrombotic infarction.

The effect of the serotonin (5-hydroxytryptamine, 5-HT) antagonist ketanserin on the remote hemodynamic consequences of thrombotic brain infarction was studied in rats. Treated rats received an injection of 1 mg/kg ketanserin 30 min before and 1 h following photochemically induced cortical infarction. Local CBF (LCBF) was assessed autoradiographically with [14C]iodoantipyrine 4 h following infarction, and chronic infarct size was documented at 5 days. Thrombotic infarction led to significant decreases in LCBF within noninfarcted cortical regions. For example, mean LCBF was decreased to 63, 55, and 65% of control (nontreated normal rats) in ipsilateral frontal, lateral, and auditory cortices, respectively. In rats treated with ketanserin, significant decreases in LCBF were not documented within remote cortical areas compared with controls. In contrast to these hemodynamic effects, morphological analysis of chronic infarct size demonstrated no differences in infarct volume between treated (27 +/- 3 mm3) and nontreated (27 +/- 6 mm3) rats. These data are consistent with the hypothesis that 5-HT is involved in the widespread hemodynamic consequences of experimentally induced thrombotic infarction. Remote hemodynamic consequences of acute infarction can be inhibited without altering final infarct size.

Animals↗

Beyond mismatch: evolving paradigms in imaging the ischemic penumbra with multimodal magnetic resonance imaging.

BACKGROUND: The ability to quickly and efficiently identify the ischemic penumbra in the acute stroke clinical setting is an important goal for stroke researchers and clinicians. Early and accurate identification of potentially salvageable versus irreversibly infarcted brain tissue may enable selection of the most appropriate candidates for early stroke therapies and identify patients who may still benefit from late recanalization or neuroprotective treatment. Recent advances in magnetic resonance imaging of the ischemic penumbra have been driven by serial MRI studies characterizing the natural evolution of cerebral infarction as well as the brain's response to reperfusion. SUMMARY OF COMMENT: Based on these studies, various models for imaging the penumbra with MRI have been proposed, including the pioneering diffusion-perfusion mismatch model and later multivariate approaches. Each model has its own unique advantages and disadvantages. CONCLUSIONS: There now are sufficient data to support paradigm shifts in a variety of central tenets regarding MRI and the ischemic penumbra. These include the insights that diffusion-perfusion mismatch does not optimally define the penumbra; that early diffusion lesions are in part reversible and often include both irreversibly infarcted tissue and penumbra; that the visible zone of perfusion abnormality overestimates the penumbra by including regions of benign oligemia; that MRI is a very practical method for acute stroke imaging; and that therapeutic salvage of the ischemic penumbra has been demonstrated in humans using diffusion-perfusion MRI.

Animals↗

[Anticardiolipin antibodies in patients with ischemic brain disease].

Anticardiolipin antibodies are best defined antiphospholipid antibodies and a recently described marker of increased risk for ischemic brain disease. Investigations were performed in 151 patients with ischemic brain disease in order to determine the occurrence of anticardiolipin antibodies and define the clinical characteristics of patients with an increased titer of anticardiolipin antibodies. Measurement of anticardiolipin antibody titer was performed by immunoenzyme method. Besides, analyses of certain tests indicative for blood coagulative properties were also done. In addition, the occurrence of anticardiolipin antibodies was investigated in 49 patients with other non-immune neurological diseases and disorders. Control sera were obtained from 50 healthy subjects and 6 patients with senile cataract. Investigation showed the increase of anticardiolipin antibody titer in 22.8% of the patients with ischemic brain disease (30% with transient ischemic attacks, 19% with brain infarction) and in 4% of the patients with other neurological disorders of non-immunological genesis. The patients with increased titer of anticardiolipin antibodies suffered more frequently from recurrent forms of ischemic brain disease, all of them were below 50, and they had less risk factors for atherosclerosis and ischemic brain disease. It was concluded that the presence of increased titer of anticardiolipin antibodies in younger patients with recurrent forms of ischemic brain disease and less risk factors could be the marker of the increased risk for ischemic brain disease.

Adult↗

[Acute therapy and prevention of ischemic cerebral infarct].

The acute therapy of the cerebral infarct necessitates the fast evaluation of the favorable risk factors and the assessment of its pathogenetical mechanisms to facilitate a specific treatment as early as possible. Acute treatment procedures like the rheologic therapy, anticoagulation, thrombolysis, application of calcium antagonists, and antiedematous therapy are discussed. Recommendations for the secondary prophylaxis with drugs like acetylsalicylic acid or triclopidine after transitory ischemic attacks or manifest brain infarctions are given. The indications for the surgical therapy of stenoses of the extracranial vessels supplying the brain are discussed and rules for the emergency management of the transitory ischemic attack are introduced.

Brain Ischemia↗

Signaling of cell death and cell survival following focal cerebral ischemia: life and death struggle in the penumbra.

Focal ischemia by middle cerebral artery occlusion (MCAO) results in necrosis at the infarct core and activation of complex signal pathways for cell death and cell survival in the penumbra. Recent studies have shown activation of the extrinsic and intrinsic pathways of caspase-mediated cell death, as well as activation of the caspase-independent signaling pathway of apoptosis in several paradigms of focal cerebral ischemia by transient MCAO to adult rats and mice. The extrinsic pathway (cell-death receptor pathway) is initiated by activation of the Fas receptor after binding to the Fas ligand (Fas-L); increased Fas and Fas-L expression has been shown following focal ischemia. Moreover, focal ischemia is greatly reduced in mice expressing mutated (nonfunctional) Fas. Increased expression of caspase-1, -3, -8, and -9, and of cleaved caspase-8, has been observed in the penumbra. Activation of the intrinsic (mitochondrial) pathway following focal ischemia is triggered by Bax translocation to and competition with Bcl-2 and other members of the Bcl-2 family in the mitochondria membrane that is followed by cytochrome c release to the cytosol. Bcl-2 over-expression reduces infarct size. Cytochrome c binds to Apaf-1 and dATP and recruits and cleaves pro-caspase-9 in the apoptosome. Both caspase-8 and caspase-9 activate caspase-3, among other caspases, which in turn cleave several crucial substrates, including the DNA-repairing enzyme poly(ADP-ribose) polymerase (PARP), into fragments of 89 and 28 kDa. Inhibition of caspase-3 reduces the infarct size, further supporting caspase-3 activation following transient MCAO. In addition, caspase-8 cleaves Bid, the truncated form of which has the capacity to translocate to the mitochondria and induce cytochrome c release. The volume of brain infarct is greatly reduced in Bid-deficient mice, thus indicating activation of the mitochondrial pathway by cell-death receptors following focal ischemia. Recent studies have shown the mitochondrial release of other factors; Smac/DIABLO (Smac: second mitochondrial activator of caspases: DIABLO: direct IAP binding protein with low pI) binds to and neutralizes the effects of the X-linked inhibitor of apoptosis (XIAP). Finally, apoptosis-inducing factor (AIF) translocates to the mitochondria and the nucleus following focal ischemia and produces peripheral chromatin condensation and large-scale DNA strands, thus leading to the caspase-independent cell death pathway of apoptosis. Delineation of the pro-apoptotic and pro-survival signals in the penumbra may not only increase understanding of the process but also help to rationalize strategies geared to reducing brain damage targeted at the periphery of the infarct core.

Animals↗

Current concepts in clinical therapeutics: ischemic cerebrovascular disease.

The classification, epidemiology, pathophysiology, diagnosis, and treatment of ischemic cerebrovascular disease (ischemic stroke) are reviewed, and the major drugs used in the prevention of this disease are discussed. Ischemic stroke is a major problem in terms of morbidity and mortality because of the high prevalence of atherosclerosis in the United States population. The pathogenesis of cerebral ischemia is multifactorial, beginning with an atherosclerotic plaque on the arterial wall that may result in stenosis or ulceration with subsequent thrombosis or embolization. Platelets may adhere to the exposed arterial wall endothelium, stimulating further platelet aggregation and accumulation of leukocytes and fibrin. Consequences of cerebral ischemia include transient ischemic attacks and brain infarcts. Diagnosis is based mainly on patient history and ancillary radiologic studies. Treatment of ischemic cerebrovascular disease is primarily preventive, since the brain has limited capacity to recover neurologic function after an infarction. Transient ischemic attacks are treated with either antiplatelet agents, anticoagulants, or surgery. Treatment of stroke is also preventive, although anticoagulation is sometimes used to prevent stroke progression. Agents that may reverse neurologic impairment following an acute stroke, such as prostacyclin, calcium-channel blockers, and opiate antagonists, are being investigated. Antiplatelet therapy is indicated in subsets of patients with cerebral vascular insufficiency. Anticoagulation therapy, if needed, should be given for only three to four months.

Brain Ischemia↗