Regional cerebral blood flow in patients with brain infarcts. A study with the 85Kr clearance technique

Changes in cerebral blood flow and recovery from acute stroke

We prospectively studied 14 patients with acute cerebral infarctions using serial 133Xenon inhalation cerebral determination (133Xe-rCBF), scored neurological examinations, and neuropsychological testing. All patients underwent the same battery of tests at 3 days, 1 week, 2 weeks, and 4 weeks after cerebral infarction to determine the prognostic value of early rCBF studies and the chronological relationship of changes in rCBF to clinical status. Baseline rCBF within 3 days of symptoms of acute stroke did not correlate with clinical neurological outcome (r = -0.17, p less than 0.30; r = -0.18, p less than 0.28, for the two indices of rCBF used). Among the 11 patients demonstrating neurological recovery, 7 improved at 1 week, significantly before increases in rCBF (p less than 0.05). We conclude that early baseline rCBF does not predict clinical outcome in patients with acute cerebral infarctions and that return of neurological function precedes rather than follows increases in rCBF.

Effect of small deep hemispheric infarction on the ipsilateral cortical blood flow in man

The effect of small, deep ischemic lesions on the ipsilateral cortical circulation was investigated in 10 patients with persistent mild or moderate neurological deficits due to infarcts in the internal capsule. rCBF studies by the 133Xe intracarotid injection method were performed 14-180 days after the onset of the infarction. The rCBF functional image was made up from the data of 133Xe dynamic images measured by an Anger-type gamma camera and the rCBF values were calculated by the initial slope method. The average value of mean rCBFs (mCBF) in 10 patients was 44.9 +/- 7.1 ml/100g/min (average PaCO2; 39.9 +/- 4.3 mm Hg). In the rCBF functional images, a focal hypoperfusion area was observed in all cases and localized around the central sulcus, especially in the precentral and central areas. Significant decreases of mCBF and the tendency to decrease of the rCBFs in the hypoperfusion focus were noted in the patients with the larger infarcts in comparison with those with the smaller ones. These results suggest that a small, deep ischemic lesion such as a capsular infarct may have remote effects on the ipsilateral cortical circulation, due probably to the damage of a number of fibers passing through the lesion.

Comparative evaluation of different methods for calculation of cerebral blood flow (CBF) in nonanesthetized rabbits

The measurement of cerebral blood flow (CBF) by the extracranial detection of the radioactivity of 133Xe injected into an internal carotid artery has proved to be of considerable value for the investigation of cerebral circulation in conscious rabbits. Methods are described for calculating CBF from the curves of clearance of 133Xe, and include exponential analysis (two-component model), initial slope, and stochastic method. The different methods of curve analysis were compared in order to evaluate the fitness with the theoretical model. The initial slope and stochastic methods, compared with the biexponential model, underestimate the CBF by 35% and 46% respectively. Furthermore, the validity of recording the clearance curve for 10 min was tested by comparing these CBF values with those obtained from the whole curve. CBF values calculated with the shortened procedure are overestimated by 17%. A correlation exists between the "10 min" CBF values and the CBF calculated from the whole curve; in spite of that, the values are not accurate for limited animal populations or for single animals. The extent of the two main compartments into which the CBF is divided was also measured. There is no correlation between CBF values and the extent of the relative compartment. This fact suggests that these two parameters correspond to different biological entities.

Lack of evolution of the cerebral blood flow during clinical recovery of a stroke

Cerebral blood flow and clinical parameters were studied in 30 stroke patients at 15th, 30th, 60th, 90th days after the cerebral insult (Xenon 133 inhalation method). The clinical improvement was not accompanied by a progressive normalization of the CBF at rest. No relationship was found between the clinical data and the CBF values; either on the affected hemisphere or on the contralateral one. It is concluded that measurement of the CBF at rest has no predictive value as regards further clinical evolution.

Long-term prognosis in ischemic cerebrovascular disease in relation to cerebral blood flow and metabolism

The correlation between long-term prognosis and cerebral hemodynamics and oxygen consumption was investigated in 46 patients with ischemic supratentorial cerebrovascular disease. Cerebral blood flow (CBF) and cerebral oxygen consumption (CMRO2) were measured by the N2O method 1-6 months (mean 68 days) after disease onset. No significant correlation was observed among CBF, CMRO2 and activities of daily living at the time of measurement. The patients' physical condition was reevaluated by the questionnaire method 2 years or more (mean 53 months) later. The CBF values in patients who were independent after completion of the follow-up period significantly exceeded those of patients dying during the period (P less than 0.05). No correlation was observed in CMRO2. The relationship among CBF, CMRO2 and changes in physical condition during the period was evaluated. Mean CBF values in patients with better prognosis exceeded those of patients with poor prognosis. Notably, CBF values in the "improved" group significantly exceeded those in the "unchanged" or "died" group (P less than 0.05, P less than 0.01). CMRO2 was not significantly correlated with changes of physical condition. These results emphasize the importance of total CBF for long-term prognosis and indicate that flow values, rather than metabolic indices, obtained in the chronic stage can usefully predict the long-term prognosis.

Regional cerebral oxygen utilization and blood flow in normal man using oxygen-15 and positron emission tomography

Quantitative determination of regional cerebral blood flow (rCBF), regional cerebral oxygen utilization (rCMRO2) and regional oxygen extraction ratio (rOER) was performed in 11 normal volunteers by an oxygen 15 inhalation method and positron emission tomography. Regional values comparable with figures from the literature have been obtained. This non-invasive approach offers the possibility of a simultaneous quantitative evaluation of these physiological parameters in health and disease.

Evaluation of cerebral infarctions of the carotid area by an intravenous 133Xenon and 99mTechnetium method

Quantitative determinations of regional cerebral blood flow (rCBFf, rCBFm) and volume (rCBV), transfer time (rCTT) and fast compartmental weight (Wf) were performed in 34 patients with infarctions of the carotid area by a 133Xe and 99mTc intravenous injection method. The results were compared with clinical signs and electroencephalographic (EEG) findings. A significant difference was found between the lesion side and the control side in all the parameters except rCBV. This difference increased with the severity of the infarction and age of the patients. The difference between the two sides was especially great in the patients with totally occluded internal carotid artery. A slight diaschisis could be observed in the present infarction group. An almost significant reduction on the "normal side" was seen in Wf. In order to assess the reciprocal influence of all the different blood flow parameters, the difference index (DI): Formula: (see text) was calculated, where delta i = the difference between the two sides in one parameter expressed in percent. This proved to be abnormal in 80% of the patients. The atraumatic isotope technique employed offers a good opportunity for the quantitative evaluation of hemodynamics in cerebral infarction and serves as an aid in the diagnosis of infarction.

Diaschisis with cerebral infarction

Fifteen patients admitted to Philadelphia General Hospital with acute strokes had repeated measurements of cerebral blood flow measured by the 133Xenon inhalation method. A progressive decline in cerebral blood flow in both hemispheres was observed during the first week after infarction in twelve of these patients. This decline could be partially explained by loss of autoregulation, but could not be correlated with level of consciousness, clinical status of PCO2. This progressive decline in flow in the non-ischemic hemisphere indicates a process more complex than a simple destruction of axonal afferants to neurons as implied by the term diaschisis. The flow changes in the non-ischemic hemisphere are likely caused by a combination of the immediate effects of decreased neuronal stimulation modified by loss of autoregulation, release of vasoactive substances, cerebral edema, and other factors.

Correlation between the clinical picture, the EEG and cerebral blood flow after partial occlusion of the middle cerebral artery in man

Quantitative measurements of global and regional cerebral blood flow were performed in 18 patients 1 to 3 days after the onset of symptoms of acute cerebral ischemia due to partial occlusion of the middle cerebral artery and were repeated 21 days thereafter. The first rCBF measurement revealed either an extensive ischemic focus or an ischemic focus with simultaneous reduction of the global blood flow within the corresponding hemisphere in all patients. The later measurements indicated no change in blood flow in the ischemic focus in any case, but there was a slight increase of global cerebral blood flow in 1/3 of the cases. The measurements of cerebral blood flow were correlated with the neurological, psychopathological and EEG findings and in spite of an unaltered cerebral blood circulation, all patients showed a distinct clinical imrovement. Various hypotheses for the return of neurological functions in patients with persistent cerebral ischemia are discussed.

133Xenon inhalation method. Analysis of reproducibility: some of its physiological implications

Regional cerebral blood flow (rCBF) was simultaneously measured at seven locations in each hemisphere by the Obrist 133Xenon inhalation method. In each of 35 healthy right-handed subjects two rest measurements were performed on consecutive days. The data analysis comprises the two-compartmentally derived parameters for flow (f1), relative tissue weight (w1), and fractional flow (FF1) respectively of the first compartment, and in addition the initial slope index (ISI). At each detector location the coefficient of variation (C.V.) of the change from first to second measurement was on average 10.4% (ISI), 14.2% (f1), 7.2% (w1), and 2.9% (FF1) respectively. However, when each regional measurement was expressed as a percentage of its hemispheric mean, the C.V. of the intermeasurement change was on average 4.4% (ISI), 7.0% (f1), 7.7% (w1), and 1.9% (FF1) respectively; that of the hemispheric means of ISI, f1, and FF1 was found to be distinctly larger, whereas that of w1 was about equal in size. The interhemispheric coefficient of variation for the change of the hemispheric means from first to second measurement was only 2.3% (ISI), 4.4% (f1), 1.6% (w1), and 1.1% (FF1) respectively. The findings suggest that (1) the variability of rCBF from subject to subject and in consecutive measurements in the same subject is to a substantial degree of physiological origin, and that (2) there are two determinants of rCBF which may operate independently: a determinant of the hemispheric mean level, probably a single determinant for both hemispheres, and a set of determinants for each separate regions superimposed on the hemispheric mean level.

XIII. Cerebral circulation and metabolism in stroke. Cerebral circulation and metabolism in stroke study group

An understanding of the cerebral circulation is so fundamental to comprehension of the pathogenesis of stroke that cerebral blood flow and metabolism merit review in this series of reports. The authors recognize that the research described here is very technical in nature and may appear to have little practical application to clinical medicine. Nevertheless, these matters are basic to the development of precise methods for the measurement of regional cerebral blood flow in man which could be used to monitor the therapy of stroke with greater success than is possible at present.

Local cerebral blood flow and vascular reactivity in a chronic stable stroke in baboons

Blood flow in the hemispheres of baboons three years after middle cerebral artery occlusion has been assessed by the hydrogen clearance technique. Blood flow in the infarct itself varied from very low (8 ml/100 gm per minute) to very high (89 ml/100 gm per minute) values and, averaging the values for the infarct as a whole, it was impossible to distinguish average flows in the infarct from those of the normal hemisphere. Flow values in surrounding zones of the infarct remained significantly lower than those of comparable normal hemispheres, and, excluding the infarct, the mean average hemispheral blood flow was 35.2 ml/100 gm per minute. This indicates a significant reduction in flow in the cortex, subsequently shown histologically to be normal, compared with normal blood flow values for the baboon hemisphere. Autoregulation was lost in the infarct and impaired in surrounding tissue. CO2 reactivity was grossly reduced in the hemisphere as a whole but was present in all areas, even occasionally in electrode placements within the infarct itself. After perfusion fixation of the head, pathological study of the area of infarction showed a fairly consistent distribution, the infarct itself consisting of many dilated blood vessels of non-capillary nature scattered among fibrous tissue in what was virtually a glial scar.

Blood flow measurements and the "look through" artifact in focal cerebral ischemia

Regional cerebral blood flow (CBF) was measured (intra-arterial injections of 133Xe) and electroencephalograms (EEG) were recorded periodically before, for two hours during, and for one and one-fourth hours after middle cerebral artery (MCA) occlusion in 20 squirrel monkeys (Saimiri sciureus). A CBF-Paco2 response curve for these animals under barbiturate anesthesia was created from CBF values prior to MCA occlusion and during the time a steady state was being achieved. The animals were subdivided into four groups (five monkeys in each) on the basis of Paco 2 values: 20, 36, 40, and 60 mm Hg. CBF values from this study were compared to previous results obtained with 85Kr. The phenomenon of "look through" and the importance of recognizing this artifact and its significance in analyzing CBF results in areas of focal ischemia are discussed. The present results were correlated with cerebral ATP and lactate concentrations in ischemic regions determined in previous studies using this preparation at these Paco2 values and at comparable time intervals before, during, and after MCA occlusion. The EEG appears to reflect the state of ischemic brain accurately. However, CBF measured by the 133Xe method can be misleading in regard to the true degree of ischemia resulting from occlusion of an intracranial vessel and cannot be relied on to demonstrate accurately "steal" or "reverse steal" due to changes in Paco2.

The effect of cerebral infarction on the regional cerebral blood flow of the contralateral hemisphere

Regional cerebral blood flow (rCBF) measurements were performed over the contralateral hemisphere by the 133Xe intracarotid injection method in 20 patients with acute cerebral infarction in the territory of the internal carotid artery. The rCBF was found to be reduced, sometimes remarkably, in all of the patients. The mean reduction was 30 percent to 36 percent from the lowest normal value for the mean age of these patients. In the younger age group (40 to 59) the reduction was greater, 40 percent to 47 percent from the lowest normal value for this age. tthe rCBF depression was not related to cerebral dominance, previous hypertension or arterial PCO2 levels. The occurred in both patients who were fully alert and those with disturbances or consciousness, although it tended to be more diminished in the latter. tit can be assumed that the flow reduction in the nonaffected hemisphere is part of a general phenomenon affecting the entire brain and caused by globally reduced cerebral metabolism.

Regional cerebral blood flow and intraventricular pressure in acute head injuries

Twelve patients who were comatose after head injuries were studied with serial determinations of regional cerebral blood flow, jugular PO(2) tension, and intraventricular pressure. These determinations began a few hours after the injury, and were followed throughout the clinical course. Diffuse derangement of cerebral vasomotor regulation is confirmed after severe head trauma, which may contribute to deterioration and poor prognosis, and which indicates a need for therapeutic maintenance of rich oxygenation, hyperventilation with moderate hypocapnia, and steady blood pressure. Continuous recording of IVP (eventually sensitized by fluid infusion or CO(2) inhalation tests) may give an early indication of the subsequent clinical state and may suggest the need to submit the patients to further investigative and therapeutic procedures.

Regional cerebral blood flow in patients with hypertensive intracerebral hemorrhage

Regional cerebral blood flow was measured by 133 Xe clearance method in 44 patients with hypertensive intracerebral hemorrhage (HIH) within three weeks from attack. Mean CBF in cases with the more disturbed consciousness was the lower value. There was no definite relationship between mean CBF and the duration from last stroke to measurement. In 44 cases, 35 showed hematoma of so-called "lateral type" and nine showed a "mesial type." There was no difference of mean CBF between these two groups. In the group with lateral-type hematoma, 14 cases were thought to show large space-occupying signs, and their mean CBF was significantly lower than that of the other 21 cases.

In 16 cases, relative hyperemic regions were observed in both the focal and nonfocal areas. In seven cases, relative ischemic regions were frequently in nonfocus rather than focus.

Response of hyperemic region to carbon dioxide was good in seven and poor in three regions in focal area, and was good in eight and poor in one region in nonfocal area. Reactivity of ischemic region to 5% CO 2 inhalation was good in three and poor in zero regions in focus, and was good in three and poor in two regions in nonfocus.

Early venous filling (EVF) was observed in 13 cases and all of them were with lateral-type hematomas.

Only four out of 13 cases showed good correlation between angiographical findings and cerebral circulation.

[Neurological complications of heart surgery. Review of their pathogenesis and bases for their treatment]

São relatadas as complicações neurológicas assinaladas em 320 pacientes submetidos a cirurgias cardíacas, com uma incidência de 7,8%. As etiologias mais comuns encontradas foram a embolia aérea (4,0%) e isquemia cerebral após hipotensão sistêmica (2,4%). Os autores analisam a patogenia das complicações cerebrais e tentam correlacioná-las com o fluxo sangüíneo cerebral, com o metabolismo cerebral e com a dinâmica dos pequenos vasos cerebrais. Uma revisão a respeito dos métodos para tratamento da isquemia cerebral é apresentada.

Reactivity of cerebral blood flow to CO 2 in patients with transient cerebral ischemic attacks

Cerebral blood flow and its ability to increase in response to inhalation of 6% CO 2 was measured in six patients with a history of transient ischemic attacks in the internal carotid distribution and in ten normal control subjects. Flow was measured with a method which uses time concentration curves made with intravenously injected radioactive indicator and externally placed radiation detectors. It permits measurement of flow, expressed in arbitrary units as a flow index, within the range of a detector placed against the side of the head.

Resting flow indices and the increases in flow indices in response to CO 2 inhalation did not differ significantly between the TIA patients and the normal control subjects. These results are discussed in terms of possible mechanisms of TIA, and it is concluded that the preserved CO 2 responsiveness of the flow indices in these six patients is in support of the theory that intermittent platelet microembolization is an important cause of TIA.

Autoregulation of cerebral blood flow. Studies during drug-induced hypertension in normal subjects and in patients with cerebral vascular diseases

Autoregulation of cerebral blood flow (constant perfusion despite variations in blood pressure) was studied in 15 control subjects and in 24 patients with cerebral vascular lesions. Thirteen patients were studied within the first 2 days of an episode of cerebral ischemia ("acute" group); 11 were studied from 15 days to several months after an ischemic episode ("chronic" group). Measurements of regional cerebral blood flow (rCBF) were made by recording extracranially in four to six locations the clearance of 85 Kr dissolved in saline and injected into the internal carotid artery. Blood flow values were calculated with a digital computer, using a compartmental analysis of the clearance curves. After measuring rCBF in the resting state, the blood pressure was increased by 30 to 40 mm Hg by the intravenous infusion of angiotensin amide (Hypertensin, Ciba). While the blood pressure was kept constant at the new level, a second series of measurements was made. Autoregulation was present in all normal subjects: no significant differences were found in average or compartmental flow rates between values obtained at normal and at hypertensive levels of blood pressure.

Loss of autoregulation was demonstrated in 10 of 13 patients of the "acute" group and in two of 11 patients of the "chronic" group. These data support previous observations that autoregulation is impaired during the first few days after an ischemic episode. The three patients of the "acute" group with a preserved autoregulatory response to hypertension had only transient ischemic attacks. In each of the other subjects of this group loss of autoregulation was found in one to three different regions of the brain. Our results suggest that regional loss of autoregulation is found frequently near the periphery of the ischemic brain. Impairment of autoregulation is one of the types of derangement of cerebral circulation that occurs after an ischemic episode.