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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The development of ischemic edema and blood-brain barrier (BBB) disruption during the 1st day of experimental cerebral infarction induced by transorbital occlusion of the middle cerebral artery (MCA) in cats was evaluated by computerized tomography (CT) scanning and compared to gravimetric and pathological studies. Regional cerebral blood flow was measured using the hydrogen clearance technique or stable xenon-enhanced CT scanning. Edema was observed gravimetrically and microscopically as early as 1 hour after the onset of ischemia in the cortex and at 3 hours or later in both the cortex and white matter. However, a significant decrease of Hounsfield numbers on the CT scans was not detectable at 1 or 3 hours and was scarcely visible at 9 hours after occlusion. Disruption of the BBB was detected by leakage of Evans blue dye at 3 hours after the occlusion in two of six animals and at 9 hours in five of five animals. However, CT scanning after infusion of contrast material showed no significant increase in Hounsfield number even 24 hours after MCA occlusion. These discrepancies should be emphasized when the dynamics of ischemic edema and BBB disruption are evaluated for clinical therapy by CT scanning.
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PMID:Discrepancies among CT, histological, and blood-brain barrier findings in early cerebral ischemia. 376 Sep 62

Forty-four studies of regional cerebral blood flow (rCBF), fractional oxygen extraction (rOER) and oxygen consumption (rCMRO2) were made on twenty-five patients with recent internal carotid artery territory infarcts. The purpose was to study flow-metabolism relationships in the contralateral hemispheres, and to investigate whether contralateral rCMRO2 was depressed as a result of the recent infarcts. Two groups of controls were included for comparison--seventeen normal volunteers, and ten patients with proven extracranial cerebrovascular disease but without evidence of cerebral infarction. The results demonstrated that: contralateral hemispheric rCMRO2 was less variable than regional oxygen availability (the product of rCBF and arterial oxygen content). This was due, in part, to the effect of individual variations in PaCO2 on rCBF, but other uncontrolled factors, such as intracranial pressure, may have had influences. As a result, rCMRO2 did not correlate with rCBF; mean rCMRO2 in the contralateral hemispheres was 12% lower than normal (a significant difference), but was not different from the value found in patients with extracranial vascular disease in whom there was no evidence of infarction or ischemia; contralateral rCMRO2 did not correlate with the size of the infarct in the opposite hemisphere. It is concluded that rCMRO2 cannot be inferred from rCBF measurements in uncontrolled human studies (as frequently done in the past), and that depression of contralateral rCMRO2 may have preceded infarction in the opposite hemisphere, a consequence of the previous influences of diseases that predispose to stroke.
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PMID:No evidence for transhemispheric diaschisis after human cerebral infarction. 376 54

Despite its efficacy in preventing rebleeding, the anticipated strong trend in favor of early intracranial surgery has not been achieved. Early intracranial operation remains a useful choice in the management of recent SAH in good-risk patients, but patients must be carefully selected on an individual basis. Many patients will undoubtedly benefit from early surgery but it is not a panacea. Further investigation of surgical treatment in combination with improved preoperative and postoperative medical therapy will be required to ameliorate the outcome of SAH. In particular, the prevention and treatment of cerebral infarction deserves attention. The results of the antifibrinolytic and timing of intracranial surgery studies point to the need for an effective prevention treatment regimen for vasospasm. Further studies about the efficacy of calcium channel blocking drugs in prevention of ischemia after SAH are needed among patients given antifibrinolytic drugs or having early operation. All the advances in treatment are predicated on prompt diagnosis of SAH in good-condition patients. The medical community needs to maintain a high degree of vigilance for the diagnosis of SAH in all patients complaining of a new, unusual or severe headache. Early referral to properly equipped and staffed medical facilities remains a keystone to effective treatment of SAH.
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PMID:Early management of the patient with recent aneurysmal subarachnoid hemorrhage. 381 Jul 3

This study was undertaken to determine the minimum CBF and CMRO2 required by the human brain to maintain normal function and viability for more than a few hours. Positron emission tomography (PET) was used to perform regional measurements in 50 subjects with varying degrees of cerebral ischemia but no evidence of infarction. There were 24 normal subjects, 24 subjects with arteriographic evidence of vascular disease of the carotid system, and two subjects with reversible ischemic neurological deficits due to cerebral vasospasm. Minimum values found in the 48 subjects with normal neurological function were 19 ml/100 g-min for regional cerebral blood flow (rCBF) and 1.3 ml/100 g-min for regional cerebral metabolic rate of oxygen (rCMRO2). Minimum values for all 50 subjects with viable cerebral tissue were 15 ml/100 g-min for rCBF and 1.3 ml/100 g-min for rCMRO2. Comparison of these measurements with values from 20 areas of established cerebral infarction in 10 subjects demonstrated that 80% (16/20) of infarcted regions had rCMRO2 values below the lower normal limit of 1.3 ml/100 g-min. Measurements of rCBF, regional cerebral blood volume, and oxygen extraction fraction were less useful for distinguishing viable from infarcted tissue. These data indicate that quantitative regional measurements of rCMRO2 with PET accurately distinguish viable from nonviable cerebral tissue and may be useful in the prospective identification of patients with reversible ischemia.
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PMID:Cerebral blood flow and cerebral metabolic rate of oxygen requirements for cerebral function and viability in humans. 387 67

Regional cerebral ischemia was produced in the rabbit by unilateral transorbital occlusion of the middle cerebral artery (procedure I); the middle cerebral and azygos anterior cerebral or anterior communicating artery (procedure II); or the middle cerebral, azygos anterior cerebral or anterior communicating, and internal carotid artery (procedure III). Evolution of ischemic lesions was examined with the immunohistochemical reaction for tubulin. With procedure I, ischemic lesions did not become constantly visible for 6 h in the basal ganglia and for 8 h in the frontoparietal region of the cerebral cortex. With procedure II, it was shortened to 3 h in the basal ganglia and to 6 h in the cerebral cortex. With procedure III, the ischemic lesions were observed in 1 h both in the basal ganglia and in the cerebral cortex as loss of the reaction for tubulin in the neuropil, nerve cell bodies, and dendrites. The evidence of neuronal damage became apparent in the same areas later by staining with hematoxylin-eosin. The experimental model presented here may be suitable for investigation of the mechanism that shifts reversible ischemia to cerebral infarction and for evaluation of the effectiveness of pharmacological intervention.
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PMID:Cerebral ischemia in rabbit: a new experimental model with immunohistochemical investigation. 393 74

In patients who present with TIA, RIND, or CVA, the cranial CT scan can rule out other etiologies for neurologic symptoms. In addition to the clinical presentation, the CT scan allows further stratification of patients being considered for carotid endarterectomy. We propose that patients be classified as TIA (+), TIA (-), RIND (+), or CVA (-). The CT scan has defined a new subgroup of patients, TIA (+) and RIND (+)--the Silent Cerebral Infarction. Patients who are categorized as TIA (+), RIND (+), and CVA (+) (cerebral infarction on CT or by history) are at increased risk for intraoperative ischemia and postoperative neurologic deficit. As such, they should be selectively shunted based on intraoperative EEG monitoring or routinely shunted. There is a strong association between ulcerative plaque at the carotid bifurcation and cerebral infarction on CT. The CT scan is a critical diagnostic procedure in evaluating the patient with an acute neurologic event. Patients with negative CT scans are candidates for early operation. Carotid endarterectomy should generally be delayed for 4 to 6 weeks in patients with positive CT scans.
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PMID:The role of cranial computed tomography in carotid surgery. 395

31P NMR spectroscopy can be safely and successfully used to study cerebral energy metabolism in sick newborn infants, provided a suitable life support and monitoring system is available. Studies of normal infants have shown characteristic spectral peaks assigned to adenosine triphosphate, phosphocreatine, phosphodiesters plus phospholipids, inorganic orthophosphate, and a large peak at the phosphomonoester resonance frequency that is attributable mainly to phosphoethanolamine, a precursor of membrane phospholipids. Both the PCr/Pi and PCr/ATP ratios were lower in normal newborn infants than reported in studies using invasive techniques in adult animals. Tissue hypoxia-ischemia was associated with a fall in PCr levels and a rise in Pi. The PCr/Pi ratio, which is an index of cerebral energy status, was normal during the first day of life in infants who had suffered severe birth asphyxia, but subsequently fell to levels well below the normal range. The presence of this latent period raises the possibility of effective early treatment following birth asphyxia, before irreversible impairment of cellular energy metabolism occurs. Low PCr/Pi ratios have also been demonstrated in infants with idiopathic cerebral infarction, periventricular leukomalacia and inborn errors of metabolism. Preliminary experience suggests that ratios below 0.8 are associated with irrecoverable failure of energy metabolism and cellular necrosis. 31P NMRS and other spectroscopic NMR techniques utilizing, for instance, 1H and 13C nuclei, have exciting potential for exploring the mechanisms and methods of prevention of various forms of cerebral damage in the newborn period.
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PMID:Investigation of cerebral energy metabolism in newborn infants by phosphorus nuclear magnetic resonance spectroscopy. 397 89

The concentrations of cyclic adenosine 3',5'-monophosphate (c-AMP) and glucose were measured in cerebrospinal fluid (CSF) of 43 patients with recent cerebral infarction divided into five groups in respect to the time (up to 24 h) elapsed between cerebrovascular insult and CSF sampling. 10 of the additionally studied subjects were (control group) neurologically normal. None of the investigated subjects was under therapy at the time of CSF sampling. The levels of c-AMP and glucose in patients with cerebral infarction were found not to be related to the degree of neurological deficit but to the duration of ischemia. CSF c-AMP was elevated (p less than 0.001) for 8-12 h following the cerebrovascular insult and subsequently reached the level of controls. The CSF glucose level was elevated during the whole period of observation.
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PMID:Cyclic AMP in the cerebrospinal fluid of patients with recent cerebral infarction. 608 47

The effect of brain neovascularization by omental transposition on somatosensory evoked potentials and on regional cerebral blood flow (rCBF) measured by hydrogen clearance was evaluated in rabbits exposed to experimental ischemia after occlusion of the middle cerebral artery (MCA). After MCA occlusion, the animals with brains neovascularized by transposed omentum showed a mild drop of rCBF accompanied by normal patterns of somatosensory evoked potentials elicited by sciatic stimulation. In the control animals, the evoked cortical electrical activity drastically decreased in amplitude immediately after arterial occlusion and fell to zero one-half hour later. The decay of bioelectrical activity in these rabbits was associated inevitably with a major drop in the rCBF. Morphological examination, as well as the functional data, indicate that omental transposition in animals exposed to experimental ischemia minimizes the occurrence of cerebral infarction because the neovascularization is capable of maintaining the local blood flow for at least 1 hour; therefore, the cortical electrical activity is preserved totally. In the light of these results, the authors suggest that this surgical technique can also be utilized in human beings who are affected by transient ischemic attacks to prevent more serious consequences.
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PMID:Physiological function after middle cerebral artery occlusion in rabbits with neovascularization of the brain by transposed omentum. 615 16

The development of positron emission tomography now allows the local study of cerebral blood flow, oxygen consumption and glucose utilization in ischemic stroke patients. In recent cerebral infarction, a disruption of the normal couple between flow and metabolism is almost constantly observed: in the first few days cerebral blood flow is either inadequate (persistent ischemia) or over-abundant ("luxury perfusion"), whereas a late "luxury perfusion" is almost constant within the necrotic area between the 10th and the 40th day. Threshold values for cerebral blood flow and oxygen consumption that are ultimately associated with necrosis or tissue integrity have been determined. A metabolic depression without C.T. Scan counterpart has been observed in various brain structures remote from the infarcted area per se. Lastly, the hemodynamic and metabolic effects the superficial-temporal-middle-cerebral-artery anastomosis have been studied.
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PMID:[Positron emission tomography in the physiopathological study of cerebral ischemia in man]. 622 16


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