Regional cerebral blood flow in patients with transient ischemic attacks studied by Xenon-133 inhalation and emission tomography

Cerebral blood flow CBF was studied in 14 patients with transient ischemic attacks TIA and arteriosclerotic neck vessel disease. CBF was measured by a rapidly rotating single photon emission computerized tomograph using Xenon-133 inhalation. This method yields images of 3 brain slices depicting CBF with a spatial resolution of 1.7 cm. Based primarily on the clinical evidence and on the angiographical findings embolism was considered the pathogenetic factor in 10 cases, whereas chronic hemodynamic insufficiency rendered symptomatic by postural factors probably accounted for the symptoms in 4 patients. Of the 14 patients, all studied days to weeks after the most recent TIA, four showed hypoperfused areas on the CBF-tomograms and with roughly the same location hypodense areas on CT-scanning, i.e. areas of complete infarction. However, an additional five patients showed reduction of CBF in areas with no abnormality on the CT-scan. The abnormal blood flow pattern was found to be unchanged after clinically successful reconstructive vascular surgery. This suggests the presence of irreversible ischemic tissue damage without gross emollition (incomplete infarction). It is concluded, that TIAs are often harmful events, as no less than 9 of the 14 patients studied had evidence of complete and/or incomplete infarction. Thorough examination and rational therapy should be instituted as soon as possible to prevent further ischemic lesions.     

SPECT study of cerebral blood flow reactivity after acetazolamide in patients with transient ischemic attacks

We investigated 15 patients with one or more transient ischemic attacks (TIAs) in the internal carotid artery territory within the month following the most recent TIA. Cerebral blood flow (CBF) was measured by single-photon emission computed tomography, using intravenous xenon-133 before and after injection of 1 g acetazolamide. Six patients had severe carotid stenosis or occlusion; the other nine patients had no significant carotid lesions. Twenty age-matched volunteers free of neurologic symptoms or history were used as controls. Mean CBF in the sylvian region was not significantly different between patients and controls. Seven patients exhibited a focal hypoperfusion at rest in the symptomatic hemisphere, and their hypoperfused areas were hyporeactive after administration of acetazolamide. Seven other patients exhibited hyporeactive areas after acetazolamide administration while their CBF tomograms at rest were normal. Thus, CBF abnormalities were detected in 14 of the 15 patients. Our findings suggest that CBF measured early after acetazolamide administration could be useful to confirm the clinical diagnosis of TIA. In the nine patients with no significant lesion of the internal carotid artery, the areas of hypoperfusion were small and were probably related to the focal ischemic event. In the six patients with severe lesions of the internal carotid artery, abnormalities were of variable size and intensity but were often large and pronounced. The discrepancy between these two subgroups of patients could be ascribed to the hemodynamic influence of the internal carotid artery lesions. Moreover, our findings may provide some insight into the pathophysiology of TIAs.     

Acetazolamide effects on cerebral blood flow in acute reversible ischemia

Cerebral blood flow (CBF) was studied in 4 patients with acute reversible ischemia (RIND). To test the ischemic areas' vasoreactivity, CBF was measured by the Xenon-133 inhalation method, before and after acetazolamide injected intravenously. At the baseline CBF study, 3 patients presented hypoperfused areas while one patient had increased CBF over the affected hemisphere. The acetazolamide test, showed in this latter case a "steal phenomenon" while in the other 3 an increase of perfusion was evidenced, in areas of normal flow, as well as in areas with reduced flow. These results suggest that in the acute phase of patients with RIND, when brain regions of hypoperfusion and neurological signs are still present, the vasomotor response may be preserved.     

Focal cerebral hypoperfusion in children with dysphasia and/or attention deficit disorder

The neural mechanisms involved in learning disorders are largely unknown. We studied three-dimensional regional cerebral blood flow (rCBF) in 13 children with dysphasia and/or attention deficit disorder (ADD), using xenon 133 inhalation and emission computed tomography. The rCBF distribution was abnormal in both hemispheres in all patients, as compared with the mean CBF distribution of nine normal children. Regions of hypoperfusion and, by inference, low metabolic activity were predominantly seen in the periventricular white matter and in border zones between major arterial territories. In patients with dysphasia, parts of both perisylvian regions were hypoperfused, and object-naming tasks failed to produce an increased flow in relevant cortical regions. Patients with different dysphasic syndromes appeared to have different patterns of rCBF. All 11 patients with ADD had hypoperfusion in the white matter of the frontal lobes and seven also in the caudate nuclei region. Methylphenidate hydrochloride increased perfusion in the central region, including the mesencephalon and the basal ganglia, and decreased perfusion of motor and primary sensory cortical areas. The location of hypoperfused structures in cognitive disorders of childhood is consistent with a role for an early hypoxic-ischemic event in their origin.     

Positron emission tomography in the asphyxiated term newborn: parasagittal impairment of cerebral blood flow

Hypoxic-ischemic encephalopathy secondary to perinatal asphyxia in the term newborn is the most common recognized cause of the subsequent motor deficits often grouped under the rubric "cerebral palsy." In order to provide insight into the basic nature and pathogenesis of the brain injury in such infants, we studied regional cerebral blood flow (CBF) by positron emission tomography (PET) in 17 asphyxiated term infants during the acute period of illness. A consistent and apparently unifying abnormality was observed, namely, a relative decrease in CBF to parasagittal regions, generally symmetrical and more marked posteriorly than anteriorly. Thus, parasagittal values for CBF were generally 25 to 50% lower than those for the sylvian cortex; in the normal or near normal infant, parasagittal values are only approximately 10% lower than those for the sylvian cortex. (Additional normal findings for regional CBF were 50% higher flows to the cerebral cortex than to the cerebral white matter and flows to the basal ganglia and thalamus at least as high as those to the cerebral cortex). That the relative deficit in CBF to parasagittal regions reflects tissue injury was indicated by the close topographic correlation on technetium brain scans in 3 patients of increased tissue uptake of radionuclide and the CBF abnormality. Moreover, the single patient studied at postmortem examination exhibited parasagittal ischemic cerebral injury that correlated well with the PET abnormality of regional CBF. The topography of the PET abnormality, i.e., the cerebrovascular watershed regions, suggests that the brain injury is basically ischemic and that the pathogenesis relates to impaired cerebral perfusion, perhaps secondary to systemic hypotension occurring in association with the perinatal asphyxia. Experimental data support this formulation.     

Relationship between cholinergic dysfunction and discrimination learning disabilities in Wistar rats following chronic cerebral hypoperfusion

The effects of chronic hypoperfusion of cerebral blood flow (CBF) on central cholinergic indices and intellectual functions were investigated in rats. Male Wistar rats, aged 9 weeks, were anesthetized with pentobarbital, and the bilateral common carotid arteries were permanently ligated. Cortical CBF in the hypoperfused rats was markedly decreased at 6 weeks after the operation. In the hypoperfused group, cholinergic indices were changed to consist two phases after the operation, before (acute) and after (chronic) 6 weeks after the operation. At 6 weeks, choline acetyltransferase activity was restored to the sham-operated level compared with the changes in the frontal cortex and thalamus + midbrain at 3 weeks. On the other hand, the maximum number of muscarinic acetylcholine receptors was reduced in the frontal cortex, hippocampus and striatum at 6 weeks and thereafter remained at this low level. In discrimination learning task, the percentage of correct responses in the hypoperfused rats was generally reduced in contrast with that of the sham-operated rats, although the number of total responses were not changed. As a consequence, cholinergic dysfunctions correlate with discrimination learning disabilities in the hypoperfused rats. These findings suggest that the hypoperfused rat may be useful for the cerebrovascular type dementia model to clarify pathophysiology.     

Continuous Arterial Spin Labeling Perfusion Magnetic Resonance Imaging Findings in Postpartum Vasculopathy

Postpartum vasculopathy (PPV) is a rare heterogeneous nonatherosclerotic vasculopathy that occurs in the puerperium. It occurs spontaneously but may be triggered by vasoconstrictor substances. The angiographic findings vary and include narrowing of the intracranial arteries and vasospasm. The angiographic findings and the occurrence of ischemic infarcts suggest that cerebral blood flow (CBF) is impaired in PPV. The purpose of this study is to determine CBF in patients with PPV. The authors conducted a case study of 3 patients with clinical and laboratory criteria for PPV examined during a 2-year period. Clinical examination, computed tomography imaging, structural magnetic resonance imaging (MRI), cerebral angiography, and continuous arterial spin labeling perfusion (CASL-PI) MRI were performed in all patients. Mean global CBF was determined, and perfusion maps were visually inspected. The CBF values and perfusion maps were correlated with the clinical symptoms and the neuroimaging findings. Three women were studied (22, 34, and 36 years old). The median time of presentation was 4 days postpartum. One presented with intracranial hemorrhage and diffuse arterial narrowing, the other 2 with stroke-like lesions, encephalopathy, and segmental narrowing mainly in the posterior circulation. CASL-PI was performed within 1 week of symptom onset in all 3 patients. Global mean CBF values were 51.8, 39.3, and 41.8 cc/100 g/min. Although global CBF was mildly diminished, it was above ischemic levels. Visual inspection of the CASL-PI perfusion maps did not reveal areas of focal hypoperfusion or hyperperfusion. In this series of patients with PPV, CBF was close to normal. Although angiography often reveals diffuse arterial narrowing, the CBF values encountered in this study do not support a state of generalized or focal oligoemia. Vasomotor tone may change intermittently in patients with PPV.     

Resting CBF sequential study during recovery from aphasia due to ischemic stroke

Cerebral blood flow (¹³³xenon inhalation method) has been studied in 30 aphasic stroke patients at 15, 30, 60 and 90 days after onset. In total aphasia the CBF values are low and the regional hypoperfused areas are extensive. In Broca's, Wernicke's and nominal aphasias, resting CBF measurements do not provide the clinician with useful additional information and clinical improvement can by no means be attributed to a resting CBF rise during the observation period.     

Postnatal adaptation of brain circulation in preterm infants

Global and regional postnatal cerebral circulatory changes in stable preterm infants were studied, and their relation to brain injury was assessed. Thirty-five preterm infants were studied on the first and second days of age. Cerebral blood flow (CBF) (mL/hg per min) and cerebral blood volume (CBV) (mL/hg) were measured using near-infrared spectroscopy. The cerebral blood flow velocity (cm/second) (peak systolic, diastolic flow, mean flow) and resistance index (RI) were determined in the internal carotid, anterior cerebral, and striate arteries by color Doppler flow imaging. Serial cerebral ultrasound studies were performed to detect changes in brain parenchymal echogenicity or intraventricular hemorrhage (IVH); the maximum severity of these findings was considered. CBF and cerebral blood flow velocity increased significantly with time, and such changes were independent of mean blood pressure, PO(2), PCO(2), hematocrit, or glycemia. In contrast, CBV and RI remained unchanged. According to the results of sonograms, no differences were found in postnatal CBF and cerebral blood flow velocity changes, regardless of whether patients had or did not have parenchymal lesions or IVH. However, higher CBV values were found on the second day in infants with IVH compared with infants without IVH. Early coupling of CBF and metabolic demands is independent of blood pressure. Improved venous return, instead of vasodilation, could be important in this adaptation.     

症状性大脑中动脉狭窄率与组织灌注的相关性

目的 应用单一症状性M1段狭窄模型定量分析症状性大脑中动脉狭窄率与组织灌注的相关性.方法 从连续203例症状性颅内动脉狭窄选择性支架成形术患者中严格筛选所有单一M1段狭窄患者.所有患者均进行头颅CT、CT灌注(CTP)和DSA检查.根据CTP检查结果,测量两侧从前往后包括额叶、前分水岭、岛盖、颞叶、后分水岭和枕叶的各脑区CTP各参数.CTP参数包括平均通过时间(MTT)、脑血流量(CBF)和脑血容量(CBV).以健侧作为正常对照,计算患侧各脑区CTP参数相对值和判定患侧各脑区CTP各参数变化.根据DSA造影结果,肓法手工测量M1段狭窄率和判断侧支代偿动脉来源及侧支血流分级.对M1段狭窄率与患侧各脑区CTP各参数绝对值、相对值进行相关性分析.结果 20例患者入组,患侧M1段狭窄率平均为70.5%±10.6%(53%～91%).以对侧为对照,患侧额叶MTT正常,CBF正常,CBV升高;前分水岭MTT延长,CBF正常,CBV升高;岛盖MTT延长,CBF正常,CBV升高;颞叶MTT延长,CBF正常,CBV正常;后分水岭MTT延长,CBF下降,CBV正常;枕叶MTT正常,CBF正常,CBV正常.狭窄M1段供血相关脑区,从前往后各脑区血流灌注逐渐减低;而后分水岭是惟一处于血流失代偿期的脑区.所有患者DSA显示侧支代偿均主要来自大脑前动脉软脑膜支.M1段狭窄率与后分水岭区相对CBV正相关(r=0.66,P=0.002);与其余各脑区各CTP灌注参数均没有相关性.结论 症状性大脑中动脉狭窄患侧各脑区组织灌注水平受侧支代偿动脉的影响有明显空间分布效应;M1段狭窄率与血流失代偿期脑区相对CBV呈正相关,与血流代偿期脑区组织灌注没有相关性.

Abstract：

Objective To quantitatively analyze the correlation between stenosis ratio and cerebral perfusion in patients with solely symptomatic M1 stenosis of middle cerebral artery.Methods All the patients with solely symptomatic M1 stenosis of middle cerebral artery were selected to this study from consecutive 203 patients with elective stenting of symptomatic intracranial artery stenosis.Brain CT, CT perfusion (CTP) and DSA examinations were performed in all cases.The CTP parameters of mean transit time (MTT), cerebral blood flow (CBF) and cerebral blood volume (CBV) were measured in regions of interest (ROIs) including bilateral frontal lobe, anterior watershed, opercula of the insula (including parsopercluaris and part of insula), temporal lobe, posterior watershed and occipital lobe.Compared with the unaffected side as control, the change of CTP and their relative CTP parameters in these ROIs at affected side were analyzed.Based on DSA data, the ratio of M1 stenosis was measured manually and blindly, the source of collateral branch of compensative artery was estimated and the blood flow was graded.Correlation between the ratio of M1 stenosis and the CTP parameters including the absolute and the relative values was investigated.Results Twenty patients were selected into this study; their average M1 stenosis ration of the affected side was 70.5% ± 10.6% (53% to 91%).Compared with the unaffected side, MTT and CBF were no significant change but CBV increased in the affected frontal lobe; MTT prolonged, CBF was normal and CBV increased in the affected anterior watershed and opercula of the insula; MTT prolonged, CBF and CBV had no significant difference in the affected temporal lobe; MTT prolonged, CBF decreased and CBV had no significant difference in the affected posterior watershed; MTT, CBF and CBV were normal in occipital lobe.Tissue perfusion gradually decreased from the front to the backward in all the M1 stenosis affected cerebral regions and the posterior watershed area was the only region at hemodynamic failure stage.Leptomeningeal vessels of the anterior cerebral artery were the major sources of compensative arteries shown in the DSA in all cases.The ratio of M1 stenosis was positively correlated (r =0.66, P =0.002) with the rCBV in posterior watershed and there is no significant correlation between the ratio and any other CTP parameters in any regions.Conclusions Associated with distribution of collateral compensative artery,tissue perfusion showed obvious spatial distribution at different level in different cerebral region.M1 stenosis ratio is positively correlated with rCBV in hemodynamic failure regions, and there is no correlation with tissue perfusion in hemodynamic compromise regions.     

Diminished regional cerebral blood flow during the intercritical period in temporal lobe epilepsy

Hemisphere and regional cerebral blood flow (CBF) were determined during interictal periods by intravenous Xenon 133 in 43 patients considered to have "temporal" epilepsy and presenting complex partial attacks with altered consciousness and lateralized EEG anomalies predominant in the temporal region. Brain scans were normal in all cases. Three subgroups were differentiated according to EEG and polygraphic examinations during sleep; temporal epilepsy with left or right EEG anomalies, with asynchronous bilateral EEG anomalies, with alternating labile unilateral EEG anomalies. Measurements of CBF were compared with those of normal subjects (n = 13) of comparable age and with those of epileptic patients with cerebral lesions on CT scan (n = 4). In epileptics with left EEG anomalies CBF was diminished by about 25 p. 100 in the left temporal region and from 15 to 22 p. 100 in other regions of the ipsi- and contralateral hemisphere. In epileptics with right EEG anomalies CBF was diminished by 20 p. 100 in the right temporal region but not on the left. CBF in the third group was comparable to that of normal subjects. In epileptics with abnormal CT scans the reduction in CBF could be correlated with EEG and CT scan findings. Studies were also conducted to determine variations in reactivity to CO2 in the areas with reduced flow, during ictal and interictal periods. Results emphasize the value of CBF measurements for investigation of epileptic foci. The importance of areas of reduced blood flow as a parameter of severity and course is discussed, as well as their pathophysiological significance.     

Paradoxical reduction of cerebral blood flow after acetazolamide loading: a hemodynamic and metabolic study with 15O PET

Paradoxical reduction of cerebral blood flow (CBF) after administration of the vasodilator acetazolamide is the most severe stage of cerebrovascular reactivity failure and is often associated with an increased oxygen extraction fraction (OEF). In this study, we aimed to reveal the mechanism underlying this phenomenon by focusing on the ratio of CBF to cerebral blood volume (CBV) as a marker of regional cerebral perfusion pressure (CPP). In 37 patients with unilateral internal carotid or middle cerebral arterial (MCA) steno-occlusive disease and 8 normal controls, the baseline CBF (CBF_b), CBV, OEF, cerebral oxygen metabolic rate (CMRO₂), and CBF after acetazolamide loading in the anterior and posterior MCA territories were measured by ¹⁵O positron emission tomography. Paradoxical CBF reduction was found in 28 of 74 regions (18 of 37 patients) in the ipsilateral hemisphere. High CBF_b (>47.6 mL/100 mL/min, n = 7) was associated with normal CBF_b/CBV, increased CBV, decreased OEF, and normal CMRO₂. Low CBF_b (<31.8 mL/100 mL/min, n = 9) was associated with decreased CBF_b/CBV, increased CBV, increased OEF, and decreased CMRO₂. These findings demonstrated that paradoxical CBF reduction is not always associated with reduction of CPP, but partly includes high-CBF_b regions with normal CPP, which has not been described in previous studies.     

Evaluation of the cerebral vasodilatory capacity by the acetazolamide test before EC-IC bypass surgery in patients with occlusion of the internal carotid artery

Cerebral blood flow (CBF) was measured by xenon-133 inhalation tomography in 18 patients with cerebrovascular disease before and 4 months after extracranial-intracranial bypass surgery. Only patients who showed a reduced CBF in areas that were intact on the CT scan and relevant to the clinical and angiographical findings were operated. The majority of the patients had suffered a minor stroke with or without subsequent transient ischemic attacks. They were studied at least 6 weeks following the stroke. All patients had an occlusion of the relevant internal carotid artery. To identify preoperatively the patients with a compromised collateral circulation and hence reduced CBF due to reduced perfusion pressure, a cerebral vasodilatory stress test was performed using acetazolamide (Diamox). In normal subjects, Diamox has been shown to increase tomographic CBF without change of the flow distribution. In the present series 9 patients showed a significant redistribution of flow in favor of the non-occluded side ("positive" Diamox test). Two of these 9 patients showed even a paradoxical decrease in focal CBF preoperatively, i.e., a "steal" effect. These 2 patients were the only patients who improved in focal CBF after shunting. The remaining 9 patients all showed uniform flow responses ("negative" Diamox test), and none of these increased in focal CBF postoperatively. The finding of an unchanged flow map postoperatively confirmed that the low flow areas were not due to restricted flow via collateral pathways. However, an increase in the regional vasodilatory capacity was observed postoperatively in the majority of patients.     

Cerebral effects of hyperbaric oxygen breathing: a CBF SPECT study on professional divers

We investigated the effects on cerebral blood flow (CBF) of pure oxygen breathing exposure during dives in a group of professional divers, in both the normobaric (NBO) and the hyperbaric oxygen (HBO) breathing conditions. Using single photon emission computerized tomography (SPECT) and Tc-99m hexamethylpropylenamine oxime (HM-PAO), we studied 10 young divers and six normal volunteers. Divers were studied by SPECT in the NBO and HBO conditions, in two different sessions. The HBO state was obtained in a hyperbaric chamber at 2.8 ATA for 15 min. By ANOVA, we did not observe any significant difference in CBF distribution between controls and divers in both NBO and HBO conditions. By individual analysis, divers showed a decreased CBF in a total of 33 regions of interest (ROIs) during NBO and 46 ROIs during HBO with respect to control values. In particular, two divers showed a remarkable increase in the number of hypoperfused ROIs during HBO (+7 and +5 ROIs, respectively). Pure oxygen breathing exposure in young divers is associated with a patchy distribution of brain areas of hypoperfusion. This phenomenon is more pronounced in the HBO state than in the NBO state. Further studies on CBF are needed to help identify divers potentially prone to harmful oxygen effects.     

CBF before and after extracranial-intracranial bypass surgery in patients with ischemic cerebrovascular disease studied with 133Xe-inhalation tomography

Cerebral blood flow (CBF) was studied by 133Xenon inhalation tomography in 22 patients with symptoms of ischemic cerebrovascular disease before and after establishment of an extracranial-intracranial bypass shunt. Selection of patients for shunting was based on angiographically demonstrated arterial occlusions and on the finding of focal low flow areas corresponding to the clinical symptoms, that consisted mainly of minor stroke with good remission and with or without subsequent TIAs. It was required that the area of low flow should clearly exceed the CT lesion present in practically all cases. Following surgery, the permanent neurologic deficits remained unchanged, while the TIAs stopped in all but one case. Two patients showed a definite increase of CBF in the low flow area while another two showed a questionable increase. All the other cases, 18 of the 22, showed an unchanged tomographic flow map with no trend towards diminution in extension or severity of the focal hypoperfused area. A persistent low flow in areas with no corresponding CT lesion following alleviation of a possible flow impediment is interpreted to represent an incomplete infarction or diaschisis.     

Modulation of cerebral hemodynamics by surgical revascularization in patients with moyamoya disease

The purpose of this study was to evaluate hemodynamic compromise in the patients with moyamoya discase and surgical modulation of the hemodynamics using stable xenon enhanced computed tomographic CBF measurement with the acetazolamide challenge. The study group consisted of 15 preoperative cases and 17 postoperative cases. In the preoperative group, regional resting cerebral blood flow (rCBF) and regional cerebrovascular reserve capacity (rCRC) were reduced. The reduction was more prominent in the anterior circulation than in the posterior circulation. In the postoperative group, rCBF and rCRC were still low in the anterior circulation. Revascularization increased the resting CBF but did not change the CRC. Postoperative CBF did not increase in adults but increased in children. These findings suggest that the misery perfusion state may be present only in the child's brain. Measurement of CBF and CRC is useful to evaluate the hemodynamics of moyamoya disease.     

Brief Report: Alterations in Cerebral Blood Flow as Assessed by PET/CT in Adults with Autism Spectrum Disorder with Normal IQ

Specific biological markers for Autism Spectrum Disorder (ASD) have not yet been established. Functional studies have shown abnormalities in the anatomo-functional connectivity of the limbic-striatal “social” brain. This study aimed to investigate regional cerebral blood flow (rCBF) at rest. Thirteen patients with ASD of normal intelligence and ten IQ-, sex- and age-matched healthy controls (HC) underwent PET/CT using [1-¹¹C]butanol, a perfusion tracer. As compared to HC, ASD showed significant CBF increases in the right parahippocampal, posterior cingulate, primary visual and temporal cortex, putamen, caudatus, substantia nigra and cerebellum. No statistically significant correlation between CBF and IQ was found. The limbic, posterior associative and cerebellar cortices showed increased blood flow in ASD, confirming previous findings about the neurobiology of ASD.     

Effect of the NMDA antagonist MK-801 on local cerebral blood flow in focal cerebral ischaemia in the rat

The effects of MK-801 upon local CBF after permanent middle cerebral artery (MCA) occlusion have been examined using [14C]iodoantipyrine autoradiography in halothane-anaesthetised rats. MK-801 (0.5 mg kg-1 i.v.) or saline was administered 30 min before MCA occlusion and CBF measured approximately 40 min after occlusion. In the hemisphere contralateral to the occluded MCA, MK-801 significantly reduced local CBF in 19 of the 22 regions examined from the levels in saline-treated rats. In the contralateral hemisphere, after treatment with MK-801, blood flow was reduced by an average of 37% with little variation in the magnitude of the reductions in different regions. In the hemisphere ipsilateral to MCA occlusion, MK-801 reduced CBF in almost every region located outside the territory of the occluded MCA. Within the territory of the occluded MCA, blood flow in the MK-801-treated rat did not significantly differ from values in vehicle-treated rats in any of the five cortical areas examined, although in the caudate nucleus there was a tendency for CBF to be lower in rats pretreated with MK-801. MK-801 had no effect on the amount of hypoperfused cerebral tissue (CBF less than 30 ml 100 g-1 min-1) in the ipsilateral hemisphere at any coronal plane examined; e.g., at coronal plane anterior 7.2 mm, 51 +/- 5% of the hemisphere displayed CBF of less than 30 ml 100 g-1 min-1 in saline-treated rats with MCA occlusion compared with 52 +/- 8% of the hemisphere in rats treated with MK-801 prior to MCA occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prediction of infarct volume and neurologic outcome by using automated multiparametric perfusion-weighted magnetic resonance imaging in a primate model of permanent middle cerebral artery occlusion

By optimizing thresholds, we identified the perfusion-weighted magnetic resonance imaging (PWI) parameters that accurately predict final infarct volume and neurologic outcome in a primate model of permanent middle cerebral artery (MCA) occlusion. Ten cynomolgus monkeys underwent PWI and diffusion-weighted imaging (DWI) at 3 and 47 hours, respectively, after right MCA occlusion using platinum coils, and were killed at 48 hours. Volumes of the hypoperfused areas on PWI were automatically measured using different thresholds and 11 parametric maps to determine the optimum threshold (at which least difference was found between the average volumes on PWI and those determined using specimens or DWI). In the case of arrival time (AT), cerebral blood volume (CBV), time to peak (TTP), time to maximum (T_max), and cerebral blood flow (CBF) determined using deconvolution techniques, the volume of the hypoperfused area significantly correlated with the infarct volumes and the neurologic deficit scores with small variations, whereas in the case of mean transit time and nondeconvolution CBF, relatively poor correlations with large variations were seen. At optimum threshold, AT, CBV, TTP, T_max, and deconvolution CBF can accurately predict the final infarct volume and neurologic outcome in monkeys with permanent MCA occlusion.     

Interictal hyperperfusion observed in infants with cortical dysgenesis.

We investigated increases of interictal regional cerebral blood flow (rCBF) in patients with intractable epilepsy caused by cortical dysgenesis. Using single photon emission computed tomography, we measured interictal rCBF of epileptic foci in 24 patients with cortical dysgenesis who achieved Engel Class I or II outcomes at least 1 year after surgical intervention. The patients included 14 males and ten females, ranging in age from 2 months to 34 years (mean 6 years and 5 months). In the interictal period, dysplastic areas showed hyperperfusion in four patients (17%), hypoperfusion in 15 (62%), and isoperfusion patterns in five (21%). Interictal hyperperfusion was found in four infants aged 3-4 months; three with focal cortical dysplasia and one with hemimegalencephaly. Our results suggest that interictal hyperperfusion may indicate the presence of an active epileptic focus in infants with cortical dysgenesis, but not in older children or adults with the same disorder. Given the risk of misinterpreting the normal side as hypoperfused, the phenomenon of interictal hyperperfusion in the epileptogenic area should be taken into account when diagnosing pediatric epilepsy caused by cortical dysgenesis.