Quantitative EEG alterations after isovolemic-hemodilutional augmentation of cerebral perfusion in stroke patients

Eleven patients with ischemic neurologic deficits in the middle cerebral arterial (MCA) territory and ipsilateral slowing on initial EEG underwent venesection and equal volume replacement with intravenous 5% human serum albumin. As the mean hematocrit was reduced by 19%, the mean cerebral blood flow (CBF) in the MCA territory of the affected and contralateral hemisphere determined by the 133Xenon inhalation technique increased 18 and 21%, respectively. Similarly, CBF in the contralateral occipital region increased 17%. The percentage total slow-wave EEG activity (fractional sum of theta and delta activity, 1.0 to 7.5 Hz) determined by fourier analysis was reduced significantly in the affected MCA territory and in the contralateral occipital region within 1 to 2 hours after isovolemic hemodilution. Using quantitative EEG analysis, rapid improvement in background EEG activity can be demonstrated following the diffuse elevation in CBF by hemodilution.     

Impaired cerebral circulation and the effect of glycerol infusion in the acute stage of hypertensive intracerebral hematoma

The purpose of the present study was to clarify the mechanism of reduction in cerebral blood flow (CBF) in the acute stage of hypertensive intracerebral hematoma and the effect of glycerol infusion on the reduced CBF. We examined 55 cases. Thirty-eight cases showed putaminal hematoma and 17 presented thalamic hematoma. The range of consciousness was from alert to stupor. CBF was measured by single photon emission CT with Xe-133 inhalation within five days after the onset of the hemorrhage. A CBF map was obtained at a slice 5 cm above the OM-line and mean CBF of the affected and non-affected hemispheres was calculated. In 20 of 55 cases, 500 ml of glycerol was intravenously infused for 60 minutes and thereafter CBF was measured again. Epidural pressure was also recorded at the affected frontal area during glycerol infusion in three of the 20 cases. CBF reduced more profoundly in the area around the hematoma on the CBF map. Mean CBF of the affected hemisphere was negatively correlated with the volume of hematoma by a quadratic regression. After glycerol infusion, 13 of 20 cases showed a significant increase in mean CBF of the affected hemisphere, while the other seven cases showed no increase. Mean CBF increased with a higher percentage in cases with ventricular hemorrhage than without ventricular hemorrhage. In three cases where epidural pressure was measured during glycerol infusion, mean CBF increased and epidural pressure decreased. The increase in mean CBF was proportional to a rise in perfusion pressure calculated as pressure difference between mean systemic arterial pressure and mean epidural pressure, indicating impaired autoregulation in these cases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive xenon-133 measurements of cerebral blood flow using stationary detectors compared with dynamic emission tomography

Repeated bedside measurements of CBF have been made possible by the recent development of a mobile unit with 10 stationary detectors using the intravenous xenon-133 method. To evaluate this technique, comparative CBF studies at rest and following the application of a cerebral vasodilatory stimulus (acetazolamide, 1 g i.v.) were performed with the mobile equipment and with xenon-133 single-photon emission inhalation tomography in patients with cerebrovascular disease. The CBF level and the flow response to acetazolamide as determined with the two methods were well correlated, although at low flow levels the stationary detectors yielded somewhat lower CBF values than did emission tomography. Considering the side-to-side asymmetry, an excellent correlation was obtained. Using the initial slope index, the stationary detectors revealed quantitatively 83% of the interhemispheric asymmetry and 63% of the asymmetry in the middle cerebral artery territory shown with the tomograph. As illustrated by a case history, the nontomographic CBF unit used in this study may provide reliable and useful information in patients with occlusive cerebrovascular disease by performing repeated CBF studies and challenging the cerebral circulation with acetazolamide.     

Cortical infarct volume is dependent on the ischemic reduction of perifocal cerebral blood flow in a three-vessel intraluminal MCA occlusion/reperfusion model in the rat

Occlusion of the middle cerebral artery (MCA) causes a reduction of cerebral blood flow (CBF), which shows a progressive decrease from the periphery to the core of the MCA territory. The severity of ischemia is dependent on the duration of the ischemic episode and degree of CBF reduction. Fixing the ischemic episode to 1 h, we have examined whether or not cortical infarct size was related to the degree of CBF reduction in a perifocal cortical area in rats. One-hour intraluminal MCA occlusion accompanied with bilateral common carotid artery (CCA) occlusion (three-vessel occlusion/reperfusion model) was carried out in Sprague-Dawley rats and CBF was monitored with laser-Doppler flowmetry in the fronto-parietal cortex, an area which is perifocal to the core of the MCA territory. Finally, infarct size was measured 7 days later and was related to the corresponding CBF decrease. Sequential ipsilateral CCA, MCA and contralateral CCA occlusions produced reductions of CBF to 96%, 52% and 33% of baseline, respectively. Cortical infarct volume was found to be dependent on the corresponding reduction of perifocal cortical CBF during the ischemic episode. These results show that the reduction of CBF in the periphery of the MCA territory during 1-h focal ischemia determines infarct size in a three-vessel occlusion/reperfusion model.     

Use of cerebrovascular reactivity in patients with symptomatic major cerebral artery occlusion to predict 5-year outcome: comparison of xenon-133 and iodine-123-IMP single-photon emission computed tomography.

The aim of this prospective study was to investigate whether decreased cerebrovascular reactivity to acetazolamide, as determined by single-photon emission computed tomography (SPECT), is an independent predictor of the 5-year risk of subsequent stroke in patients with symptomatic major cerebral artery occlusion. Cerebrovascular reactivity to acetazolamide in the middle cerebral artery (MCA) territory ipsilateral to the occluded artery was determined on the basis of two different methodologies: cerebral blood flow (CBF) percent change obtained quantitatively from xenon-133 (133Xe) SPECT, and asymmetry index (AI) percent change obtained qualitatively from N-isopropyl-p-[123I]-iodoamphetamine (IMP) SPECT. Seventy patients with unilateral internal carotid artery or MCA occlusion were divided into two groups within each SPECT methodology (normal or decreased CBF percent change and AI percent change) and followed up for 5 years. Cumulative recurrence-free survival rates for patients with decreased CBF percent change were significantly lower than for those with normal CBF percent change (P = 0.0205). There was no significant difference in cumulative recurrence-free survival rates between patients with decreased AI percent change and those with normal AI percent change. Only decreased CBF percent change was a significant independent predictor of stroke recurrence (P = 0.0051). The present study demonstrated that decreased cerebrovascular reactivity to acetazolamide determined quantitatively by 133Xe SPECT is an independent predictor of the 5-year risk of subsequent stroke in patients with symptomatic major cerebral artery occlusion, and that the qualitative method using 123I-IMP SPECT is a poor predictor of the risk of subsequent stroke in this type of patient.     

Herpes zoster ophthalmicus with cerebral angiitis and reduced cerebral blood flow

Two patients with herpes zoster ophthalmicus (HZO) who experienced a delayed contralateral hemiparesis, the so-called crossed zoster syndrome, are described. Particular emphasis is paid to the cerebral blood flow (CBF) findings studied with the Xenon-133 inhalation technique using single photon emission computed tomography (SPECT). In a 40-year-old female with right-sided hemiparesis, angiography showed multiple segmental narrowings of the intracerebral arteries. Cerebral computer tomography (CT) scans were normal. The CBF studied 11 months after the HZO showed a generalized reduction of flow which, however, was more pronounced in the left hemisphere. On re-examination 8 months later both the mean hemispheric flow and regional CBF (rCBF) had increased to normal values. In a 66-year-old male with dysphasia and right-sided hemiparesis, cerebral CT scans demonstrated two small deep left-sided infarcts. CBF examination showed a generalized reduction of flow in the left hemisphere. The flow was slightly increased on re-examination 12 months later. These findings suggest that the Xenon-133 inhalation method represents a useful way to demonstrate the CBF pattern in this group of patients.     

A comparison of xenon-133 and xenon-127 for the determination of regional cerebral blood flow measured by dynamic SPECT.

Phantom studies and cerebral blood flow (CBF) measurements in 11 normal subjects at rest were performed by single photon emission tomography (SPECT) with Xe-133 (16 mm full-width at half-maximum [FWHM] collimation) and Xe-127 (16 mm, 12 mm, and 9 mm FWHM collimation). The phantom results clearly illustrated the feasibility of Xe-127 studies and the advantage of Xe-127 over Xe-133 for equivalent patient dose exposures. CBF values obtained with Xe-127 were comparable to those of Xe-133 for the 16 mm collimator, although higher flow values were found with the better resolution, probably because of reduced partial volume effects. The correlations between the various groups of examinations were high, except for the Xe-133 and Xe-127 16 mm collimator groups. Xe-127 allows a considerable increase in the resolution of the images, while exposing the patient to a lower radiation dose. Potential limitations because of higher energy penetrating photons from Xe-127 were not observed in this specially shielded equipment.     

CBF and transcranial Doppler sonography during vasodilatory stress tests in patients with common carotid artery occlusion.

Cerebral blood flow (CBF) and the cerebral vasoreactivity was measured in patients with cerebrovascular disease and longstanding occlusion of the common carotid artery (CCA). In addition, regional CBF was correlated with transcranial doppler (TCD) measurements at baseline and during 6% CO2 inhalation and after intravenous administration of 1 g of acetazolamide. Twelve patients with a mean age of 62 years (range 45 to 71 years) were included, and the data compared to age-matched healthy controls. CBF was measured by intravenous injection of xenon-133 and SPECT (Tomomatic 564). TCD of the middle cerebral artery (MCA) was done by EME TC-64B. A very low global CBF value of 28 +/- 5 (SD) ml 100 g-1 min-1 was found at baseline as compared to 55 +/- 5 ml 100 g-1 min-1 in the normal controls. During 6% CO2-inhalation and after acetazolamide administration, CBF increased by 58 +/- 24% and 51 +/- 21%, respectively, indicating substantial collateral supply. Correlative analysis of CBF in the MCA territory and TCD in the MCA showed statistical significance only for the pooled data, i.e. compiling the data obtained during baseline and the two vasodilatory tests, and then only for the mean and peak TCD velocity (e.g. r = 0.59, p less than 0.002, n = 35, mean velocity, right side). We conclude that TCD measurements do not predict regional CBF in patients with CCA occlusion. The study emphasizes that these two methods yield supplementary information, with TCD measurements providing information of the circle of Willis and CBF studies of the flow distribution.     

Photothrombotic occlusion of rat middle cerebral artery: histopathological and hemodynamic sequelae of acute recanalization

The histopathological and hemodynamic consequences of photochemically induced middle cerebral artery (MCA) thrombosis and recanalization were studied in the rat. Recanalization of the thrombosed MCA segment was achieved by the topical application of nimodipine at 1 h following photochemically induced occlusion. Pathological consequences of permanent and temporary occlusion were compared by morphometric procedures 7 days following thrombus formation. Rats with permanent thrombosis exhibited consistent infarction of both striatum and cortex. MCA recanalization at 1 h was associated with a significant reduction in total infarct volume. In recanalized rats, small cortical infarcts, confined to the peripheral MCA territory, were observed in only three of six rats. In contrast, a mixed pattern of infarction and ischemic cell damage was documented throughout the striatum in all rats. Local CBF (1CBF), measured autoradiographically, was significantly reduced in the MCA territory following 1 h of MCA occlusion, especially within the striatum. At 1 h after recanalization, 1CBF recovered within the previously ischemic brain regions to greater than 50% of control. Perfusion deficits were detected by carbon black infusion within focal areas of the striatum following reperfusion. Thus, cortical neurons appear to tolerate 1 h of MCA occlusion in this model. In contrast, reperfusion following 1 h of photochemically induced MCA occlusion gives rise to selective injury to the striatum.     

Impact of craniotomy area on improvement of cerebral blood flow in combined revascularization surgery for moyamoya disease

ObjectiveTo investigate factors associated with improvements in cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) after combined revascularization surgery for moyamoya disease, with special attention to the size of craniotomy.MethodsWe retrospectively analyzed 35 hemispheres in 27 patients with adult and older pediatric moyamoya disease. CBF and CVR were measured separately in the MCA and ACA territories from acetazolamide-challenged single-photon emission computed tomography before and after 6 months postoperatively, and associations with various factors were analyzed.ResultsPostoperative CBF improved in patients with lower preoperative blood flow in both ACA and MCA territories. Postoperative CVR improved in 32 of 35 patients (91.4%) in the MCA territory and in 30 of 35 patients (85.7%) in the ACA territory, with more prominent improvement in the MCA territory than in the ACA territory (MCA territory 29.7% vs ACA territory 21.1%, p = 0.015). Craniotomy area did not correlate with postoperative CBF and only MCA territory was associated with good (≥30%) CVR improvement (odds ratio 9.33, 95% confidence interval 1.91–45.6, p = 0.003).ConclusionsPostoperative CBF improved in adult and older pediatric cases, reflecting preoperative CBF. Postoperative CVR improved in most cases, although the degree of improvement was more prominent in the MCA territory than in the ACA territory, suggesting a contribution of the temporal muscle. Large craniotomy area was not associated with improved blood flow in the ACA territory and should be applied prudently.     

利用激光散斑成像技术观察尤瑞克林对脑梗死大鼠脑血流的影响

目的 利用激光散斑成像技术研究尤瑞克林对大鼠脑梗死后局部脑血流的影响.方法 成年雄性SD大鼠24只,线栓法制备大鼠永久性大脑中动脉梗死模型.激光散斑成像系统观测缺血半球皮质及大脑中动脉供血区血流,2,3,5-三苯基氯化四氮唑(TTC)染色法测定脑梗死体积,并进行神经功能评分.结果 皮质及大脑中动脉供血区血流在大剂量组第1天及第2天给药后均有明显改善,部分大脑皮质血管增粗,血流速度加快,小剂量组及生理盐水组无明显变化,脑缺血48 h后,大、小剂量尤瑞克林组及生理盐水组的梗死体积分别为10.14%±3.02%,25.99%±3.90%,27.10%±3.32%,大剂量组与生理盐水组比较差异有统计学意义(F=61.14,P<0.01),小剂量组与生理盐水组比较差异无统计学意义.缺血后4 h,大剂量组神经功能损伤明显改善,小剂量组及生理盐水组无明显改变,36 h各组间的神经功能评分差异无统计学意义.结论 尤瑞克林可以减少大鼠局灶性脑缺血后梗死体积,延缓神经功能损伤,其作用可能与促进侧支循环的开放,增加大脑皮质和缺血区血流有关.     

脑血管功能储备评估的方法学

应用单光子发射计算机断层(SPECT)结合放射性标记的同位素示踪剂，如IMP、^99mTc-HMPAO与^99mTc-ECD和^133Xe，至今仍作为测定脑血流量(CBF)的金标准。正电子发射断层扫描(PET)可通过放射性同住素标记的氧、葡萄糖或其他化舍物间接地测定CBF。动态的或功能的核磁共振成像通过去氧血红蛋白或氧敏感的成像技术评估CBF。CT成像技术与^133Xe清除率联合应用测定CBF，从1978年至今，仍可视为另一种CBF测定的金标准，其敏感性与特异性均超过60％。TCD作为无创的脑血流速度检测技术，直到1990年以后才始用于脑血管反应性的检测。所有的上述检测技术或方法，在一些特异的脑血管舒张剂或方法应用之前，均不能准确测定脑血管功能储备(CRC)。只是当这些方法与特异性的脑血管舒张剂或方法，如应用乙酰唑胺、吸入二氧化碳或短时间屏气联合应用时，CRC的检测可成为可能。     

Regional cerebral blood flow in the acute stage with ischemic cerebrovascular disease studied by xenon-133 inhalation and single photon emission computerized tomography

The papers about cerebral blood flow (CBF) in patients with cerebrovascular diseases have been already reported by positron emission computerized tomography (PET), single photon emission computerized tomography (SPECT), Xray CT (CT) using cold Xe, and so on. However the literature about the CBF changes in acute stage is few. We studied CBF in 68 patients with ischemic cerebrovascular disease within 48 hours after the onsets from February 1984 through February 1985. CBF was measured by a rapidly rotating single photon emission computerized tomography (SPECT) using non-invasive Xenon-133 inhalation method. Our subjects included 51 cases with cerebral infarction (male 37, female 14, average 62.9 years) and 17 cases with TIA (male 13, female 4, average 60.5 years), the patients who had a past history of stroke were excluded from the subjects. The SPECT was performed with use of Tomomatic 64 developed by Dr. Lassen, et al, SPECT and carotid arteriography were simultaneously performed within 48 hours in all cases. CT we used were GE CT 9800 scanner and Hitachi HF CT. The following results have been obtained: 1) SPECT clearly showed an ischemic focus correlated with clinical symptom after the attack rather than CT, the positive finding by SPECT was 92.2% and that by CT was 62.7% within 48 hours after the onset. 2) The remote effect phenomenon so-called crossed cerebellar diaschisis was demonstrated in 7 of 14 cases (50%) with cerebral infarction due to internal carotid artery occlusion and in 9 of 26 cases (34.6%) with that due to middle cerebral artery occlusion. 3) SPECT and CT were performed within 8 hours after the onset in 20 cases with cerebral infarction. SPECT showed decreased CBF in all cases whereas the positive finding by CT was 40.0%. The area of decreased CBF was always larger than the low density area that CT demonstrated. Mean CBF value of the cerebral hemisphere in the cases with ICA occlusion within 8 hours after the onsets was 31.0 (ml/100 g/min), and that of MCA occlusion was 36.0 (ml/100 g/min), and that of MCA occlusion was 36.0 (ml/100 g/min). 4) The positive finding by SPECT on TIA cases was 47% and that by CT was 41.1%, SPECT usually did not demonstrate a small ischemic focus especially at the deep region (ie, basal ganglia region). 5) SPECT using Xe-123 inhalation was useful and non-invasive method for the diagnosis in acute stage with ischemic cerebrovascular disease.(ABSTRACT TRUNCATED AT 400 WORDS)     

Pathophysiological studies in moyamoya disease by rCBF and cortical artery pressure measurements in comparison to those in ICA or MCA occlusion

The authors measured preoperative rCBF and intraoperative cortical artery pressure (CAP) during STA-MCA anastomosis to investigate cerebral hemodynamics in moyamoya disease. Six of 13 patients including 3 children showed ischemic attack and the remaining presented hemorrhagic attack. rCBF was measured by single photon ECT with Xe-133 inhalation technique. CAP's and rCBF's in moyamoya disease were compared to those in the 22 internal carotid artery (ICA) and 8 middle cerebral artery (MCA) occlusion. Systemic arterial blood pressure (SABP) was obtained at the radial artery. Mean rCBF in the MCA territory in moyamoya disease, ICA occlusion, and MCA occlusion were 39, 37, and 33 ml/100 g/min respectively. Mean SABP and CAP in moyamoya disease were 103 and 28 mmHg, respectively. In ICA occlusion, mean SABP and CAP were 98 and 45 mmHg, respectively. In MCA occlusion, mean SABP and CAP were 89 and 36 mmHg, respectively. To clarify the hemodynamics, vascular resistance was obtained from the following equations: The proximal vascular resistance (Rp), which was produced from the cervical ICA to cortical artery, was obtained by (mean SABP - mean CAP)/(rCBF). And distal vascular resistance (Rd) which was produced from the cortical artery to jugular vein, was obtained by (mean CAP)/(rCBF). Mean Rp in moyamoya disease ICA occlusion and MCA occlusion were 2.01, 1.21 and 1.70, respectively. Rd in moyamoya disease, ICA occlusion and MCA occlusion were 0.79, 1.37 and 1.22, respectively. There were significant differences in Rp and Rd between moyamoya disease and ICA or MCA occlusion. In ischemic group in moyamoya disease, rCBF, SABP, CAP, Rp and Rd were 41 ml/100 g/min, 111 mmHg, 28 mmHg, 1.92 and 0.70, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebral hyperemia, stroke, and transfusion in sickle cell disease

To investigate cerebral hemodynamics in sickle cell disease (SCD), we used the 133Xenon inhalation technique of quantifying cerebral blood flow (CBF) in 67 patients. Clinical examinations and cerebral magnetic resonance imaging also were performed in all patients. Compared with age-matched healthy controls, CBF was elevated by 68% in patients, and inversely related to hematocrit. An experimental index of cerebral blood volume, pr4, was also elevated in the patients in a similar manner. Cerebral blood volume was positively correlated to CBF in SCD patients but not in controls. History of stroke and current neurologic symptoms were associated with lower flow and higher cerebral blood volume. Transfusion therapy reduced the hyperemia, the reduction being greater than expected by hematocrit elevation alone. These findings document a vasodilatory hyperemia in SCD. This dilatation may be a risk factor for ischemic distal-field infarctions, as visualized by MRI, due to a limitation of cerebrovascular reserve capacity.     

Comparative study of regional cerebral blood flow values measured by Xe CT and Xe SPECT

The regional cerebral blood flow (rBCF) values measured by stable xenon-enhanced computed tomography (Xe XT) and by radioactive xenon-133 single photon emission computed tomography (Xe SPECT) were compared in 16 patients with cerebral infarct. On the non-lesion side Xe SPECT recorded 10.7% higher rCBF values than Xe CT in the anterior cerebral artery territory while Xe CT recorded 9.6% higher values than Xe SPECT in the middle cerebral artery territory. These differences were not statistically significant. Although the rCBF values were almost the same no correlation was found between the two methods in the posterior cerebral artery territory and the basal ganglia. Only hemispheric CBF on the non-lesion side showed the same value and a good correlation between the Xe CT and the Xe SPECT. There was a good correlation in the hemispheric CBF values on the lesion side, too. The difference of rCBF between the non-lesion side and the lesion side was expressed smaller in the Xe SPECT than in the Xe CT. This is in agreement with the previous reports that Xe SPECT overestimates the flow in the low flow areas. The higher rCBF values in the anterior cerebral artery territory measured by the Xe SPECT was ascribed to the artifact from the radioactivities in the inhalation mask and the air passages as reported previously. In conclusion, there is no good correlation between the rCBF values measured by the Xe CT and by the Xe SPECT. Only hemispheric CBF shows a good correlation between the two methods.     

Focal cerebral infarction in the rat: II. Neuropathological study and local cerebral blood flow pattern

We have recently reported that middle cerebral artery (MCA) occlusion in the rat produces a uniform pattern of cerebral ischemia in an acute phase. This study was done to determine if this model is also useful for quantitative evaluation of infarction size in a chronic phase. [Methods] Sprague-Dawley rats were anesthetized with halothane and left MCA was occluded via transretro-orbital approach. The following studies were done. Neuropathological study was done one week after MCA occlusion. After perfusion fixation, the brain was cut into 6 coronal slices and stained sections were examined. Local cerebral blood flow patterns were observed by 14C-iodoantipyrine autoradiographic technique 1, 2, and 5 days after the occlusion. [Results] Neuropathological studies invariably showed infarct in the cortex and the lateral part of the basal ganlia. The ratio of the infarct to the total areas of both hemispheres in 6 coronal sections was 14.05 +/- 2.66% (Mean +/- SD) in MCA occluded animals (N = 14) and 0.59 +/- 0.46% in sham operated animals (N = 12). Relative to the contralateral hemisphere, marked reduction in CBF was seen in the territory of the MCA and moderate reductions were also seen in the surrounding areas. The same pattern of increased CBF as previously reported was also seen in the ipsilateral substantia nigra and globus pallidus 1, 2, and 5 days after the occlusion. These results indicate the usefulness of this chronic focal cerebral infarction model in the evaluation of infarction.     

The effects of aging on cerebral blood flow in migraine

We studied cerebral blood flow (CBF) with the 133xenon inhalation technique in 92 migraine patients (49 classic/complicated, 43 common), aged 19 to 85 years, in the headache-free period. We compared results to 49 control subjects, aged 22 to 80 years. CBF declined with age in both groups, but at a slower rate in migraine patients, a difference most pronounced in classic migraine. CBF was lower in migraine patients than in controls under 48 years of age. In addition, regional asymmetry of blood flow was found more frequently in young migraine patients than in controls. These results suggest that differences exist in cerebrovascular resistance tone in migraine patients, which may contribute to the threshold for a migraine attack and result in differing age-related changes in blood flow.     

Regional cerebral blood flow, diaschisis, and steal after stroke

Regional CBF was measured by 133Xe inhalation in unilateral cerebral infarction, carotid TIAs, and normal volunteers. Regional CBF values were bilaterally and symmetrically reduced in patients measured within 3 weeks after stroke. Later, rCBF values returned toward normal in the contralateral hemisphere of patients with infarction and in both hemispheres with carotid TIAs. In cases with carotid occlusive disease, flow reduction was seen in the contralateral posterior cerebral artery distribution, with hyperemia in ipsilateral occipital lobe caused by interhemispheric steal. Brainstem-cerebellar flow values were increased following acute cerebral infarction if patients were alert but reduced if consciousness was impaired.     

Two minute slope inhalation technique for cerebral blood flow measurement in man. 1. Method.

The two minute slope method of measuring cerebral blood flow (CBF) by inhalation of 133Xe is described. It requires the subject to remain still for only two minutes and is thus applicable to a wide variety of patients and to investigations involving brief physiological stimuli. The influence of extracerebral blood flow on CBF calculated by this method has been studied. Results from the two minute slope inhalation method using two minutes of data correlate well with those obtained by carotid injection using either two minutes or 10 minutes of data.