Regional cerebral blood flow and its autoregulation in patients with transient focal cerebral ischemic attacks.
01 May 1970-Neurology (Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology)-Vol. 20, Iss: 5, pp 485-485
TL;DR: The xenon-133 injection method is used to investigate the regional cerebral blood ffow (rCBF) of patients with TIA and predicts that the autoregulation of focal cerebral blood flow would be normal in the chronic symptom-free state between attacks.
Abstract: THE PATHOGENESIS of transient ischemic attacks (TIA) is often not clear. By definition, transient ischemic attacks are provoked by acute but transitory focal cerebral ischemia due to focal failure of the cerebral circulation, but the cause of this circulatory failure is, in most cases, uncertain. Two main theories have been put forward: the hernodynamic and the thromboembolic. The so-calIed hemodynamic theory postulates that the focal brain area is chronically on the brink of ischemia because of lesions of the smaller or larger arteries. The ischemia is rendered manifest by a temporary decrease in perfusion pressure, usually secondary to systemic arterial hypotension. In normal human beings, a decrease in cerebral perfusion pressure is quite efficiently counteracted by vasodilatation and cerebral blood flow, therefore, it tends to remain unchanged. This autoregulatory response is chronically abolished in the marginally perfused focal area. In contrast, the thromboembolic theory postulates that transient ischemic attacks are caused by recurrent acute thromboembolic cerebral vascular occlusions of transitory nature due to rapid disappearance of the occlusion by thrombolytic mechanism. This theory predicts that the autoregulation of focal cerebral blood flow would be normal in the chronic symptom-free state between attacks. In order to investigate the pathogenetic mechanisms of TIA we have, in this study, used the xenon-133 injection method to investigate the regional cerebral blood ffow (rCBF) of patients with TIA. Particular attention has been focused on the autoregulatory response of a large number of cerebral regions.
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TL;DR: Investigation into the importance of hemodynamic factors in ischemic stroke can now be based on accurate assessment of cerebral (not carotid or vertebrobasilar) hemodynamics in the context of other coexisting epidemiological, clinical, hematological, and angiographic risk factors.
Abstract: During the past decade, technological advances have made it possible to measure regional cerebral hemodynamics in individual patients. Studies performed with these techniques have demonstrated that the degree of carotid stenosis correlates poorly with the hemodynamic status of the ipsilateral cerebral circulation. The primary determinant of cerebral perfusion pressure and blood flow under these circumstances is the adequacy of collateral circulatory pathways. Since collateral circulation varies from patient to patient, there is no critical degree of carotid stenosis that consistently produces hemodynamic compromise of the cerebral circulation. It is, thus, time to abandon the concept of the hemodynamically significant carotid stenosis as it relates to the pathogenesis and treatment of cerebrovascular disease. Measurement of regional cerebral hemodynamics have provided new insight into the pathogenesis of tranisent ischemic attacks and generated some preliminary data on the prognostic and therapeutic importance of chronic reductions in regional cerebral perfusion pressure. Further investigations into the importance of hemodynamic factors in ischemic stroke can now be based on accurate assessment of cerebral (not carotid or vertebrobasilar) hemodynamics in the context of other coexisting epidemiological, clinical, hematological, and angiographic risk factors.
782 citations
TL;DR: Experimental results demonstrate the theoretically expected close relationship between rCBFinitial and flow of gray substance (r CBFinitial 20% to 30% lower than Fg) and how the cerebral clearance curve (normally biexponential) with low flow values becomes gradually monoexponential.
Abstract: The regional cerebral blood flow can be calculated from the initial slope of the logarithmically displayed clearance curve following intra-arterial injection of 133Xe (rCBFinitial). The relationship between this parameter and the values resulting from stochastic (height over area) and compartmental analyses is extensively discussed. Experimental results demonstrate the theoretically expected close relationship between rCBFinitial and flow of gray substance (rCBFinitial 20% to 30% lower than Fg). It is shown how the cerebral clearance curve (normally biexponential) with low flow values becomes gradually monoexponential. Thus only flow of gray substance changes, whereas flow of white substance is independent of CBF∞. CBF10 was shown to overestimate CBF∞ with about 15% independent of the flow level. Correlation between CBFinitial and CBF10 was linear (r=0.98) at CBF10 values above 20 ml/100 gm/min.
The CBFinitial normal value is found to be 64±9 ml/100 gm/min, and the interchannel coefficient of variation is 8.2%. A correction for remaining radioactivity from previous measurements is described. Using this, no significant difference was found between repeated resting state measurements.
The CBFinitial-Paco2 relationship was found to be best described as exponential. In a group of patients with various intracranial diseases, 1 mm Hg change in Paco2 resulted in 4% change of CBFinitial quite independent of the CBFinitial level.
498 citations
TL;DR: In 334 consecutive admissions for acute stroke, the blood pressure was elevated in 84% on the day of admission and decreased spontaneously an average of 20mm Hg systolic and 10 mm Hg diastolic in the ten days following the acute event.
Abstract: In 334 consecutive admissions for acute stroke, the blood pressure was elevated in 84% on the day of admission. The blood pressure decreased spontaneously an average of 20 mm Hg systolic and 10 mm Hg diastolic in the ten days following the acute event without specific antihypertensive therapy and was elevated in only one third of the cases on the tenth hospital day. The early elevation in blood pressure is likely a physiological response to brain ischemia, and blood pressure falls as recovery of brain function occurs. (JAMA1981;246:2177-2180)
433 citations
TL;DR: A group of apoplectics with a single pathogenesis, i.l.e., with acute occlusion of the middle cerebral artery, has been studied with the aim of collecting information on the regional cerebral blood flow (rCBF) and its regulation in a well-defined type of Apoplexy.
Abstract: THE XENON 133 INJECTION METHOD allows simultaneous measurement of the blood flow in many areas of the brain.l.2 It has been used for determination of the regional cerebral blood flow in several small series of patients with cerebrovascular diseases of various types.3-7a The regional flow responses of the braip to changes of arterial blood pressure and arterial pC0, have also been studied, and focal loss of autoregulation and of pC0,-induced vasodilatation in cases of cerebral apoplexy have been reported.\"6y7a In the present study, a group of apoplectics with a single pathogenesis, i.e., with acute occlusion of the middle cerebral artery, has been studied with the aim of collecting information on the regional cerebral blood flow (rCBF) and its regulation in a well-defined type of apoplexy. The results obtained in apoplexy without occlusion of a major cerebral artery and in transient ischemic attacks will be reported in subsequent paper^.^.^
192 citations
TL;DR: The ISH statement on the management of blood pressure in acute stroke was finalized after presentation and discussion at the World Health Organization and International Society of Hypertension Meeting on Stroke and Blood Pressure, held in Melbourne, Australia, 5-7 December 2002.
Abstract: The ISH statement on the management of blood pressure in acute stroke was finalized after presentation and discussion at the World Health Organization and International Society of Hypertension (WHO-ISH) Meeting on Stroke and Blood Pressure, held in Melbourne, Australia, 5-7 December 2002. The meeting was conducted under the auspices of the Austin Hospital Medical Research Foundation, Melbourne.
180 citations
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704 citations
TL;DR: Ophthalmoscopic studies were made during 2 attacks of partial blindness in a patient who had had hundreds of such episodes in one eye, and the underlying vascular events were witnessed in greater detail than heretofore reported in the literature.
Abstract: ONLY ON RARE OCCASIONS does one have an opportunity to observe the retinal circulation during an episode of transient monocular blindness. Recently, ophthalmoscopic studies were made during 2 attacks of partial blindness in a patient who had had hundreds of such episodes in one eye. The underlying vascular events were witnessed in greater detail than heretofore reported in the literature. In addition to having their own intrinsic interest, such observations may, by inference, provide valuable information concerning the behavior of the cerebral circulation during transient ischemic attacks associated with cerebral thrombosis.
350 citations
TL;DR: In this article, bright, orange-colored plaques were found at bifurcations of the retinal arterioles in 27 of 235 patients with occlusive disease within the carotid arterial system and in 4 of 93 patients with vertebral-basilar arterial systems.
Abstract: Bright, orange-colored plaques were found at bifurcations of the retinal arterioles in 27 of 235 patients with occlusive disease within the carotid arterial system and in 4 of 93 patients with occlusive disease of the vertebral-basilar arterial system. Some of these plaques later disappeared from the retina, some remained stationary, and still others were observed to move distally. In 6 of 35 patients with recent carotid endarterectomy, new plaques appeared during or shortly after the operation. An occasional plaque caused occlusion of the arteriole. These plaques apparently consist of embolic material from atheromatous lesions in the aorta or carotid arteries. The finding of such plaques on routine ophthalmoscopy constitutes an important sign of atherosclerosis even in an otherwise asymptomatic person.
305 citations
TL;DR: The study demonstrates the existence of hyperemia in some regions in certain cases of acute apoplexy, and finds a local loss of the normal regulation to variations of arterial blood pressure and arterial carbon dioxide tension.
Abstract: THIS paper describes the result of simultaneous measurement of the blood flow in 16 regions of the brain using the xenon 133 (133Xe) injection method1-3in acute apoplexy. The study demonstrates the existence of hyperemia in some regions in certain cases of this disease. It further demonstrates that the local hyperemia correlated with the angiographic finding of early filling veins, a correlation also noted by Cronquist and Laroche.4Of perhaps greater importance for the understanding of the pathophysiology of apoplexy are our finding of a local loss of the normal regulation to variations of arterial blood pressure and arterial carbon dioxide tension. All these abnormalities are considered to be a consequence of localized tissue acidosis and to constitute an example of the "luxury perfusion syndrome" of brain tissue recently discussed by Lassen.5 Methods Regional cerebral blood flow was studied by the133Xe residue detection method
265 citations