Clinical features associated with internal carotid artery occlusion do not correlate with MRA cerebropetal flow measurements

OBJECTIVES: The aetiology of clinical symptoms in patients with severe internal carotid artery (ICA) lesions may be thromboembolic or haemodynamic. The purpose was to assess whether changes in cerebropetal blood flow caused by an ICA occlusion have an effect on clinical symptoms and cerebral metabolism. METHODS: Forty three patients with an ICA occlusion who had hemispheric ischaemia (transient ischaemic attack or stroke), retinal ischaemia, or without symptoms, and 34 patients without significant ICA lesions with either hemispheric ischaemia or no symptoms were studied. Magnetic resonance angiography (MRA) was used to investigate total cerebropetal flow (flow in the ICAs plus basilar artery) and the flow in the middle cerebral arteries. Cerebral metabolic changes in the flow territory of the middle cerebral artery were determined with proton MR spectroscopy. RESULTS: Low total cerebropetal flow (r=-0.15, p<0.05) and low middle cerebral artery flow (r=-0.31, p<0.001) were found in patients with an ICA occlusion, but did not correlate with the clinical syndrome. By contrast, patients with prior symptoms of hemispheric ischaemia had decreased cerebral N-acetylaspartate/choline ratios (r=-0.35, p<0.001). However, the presence of an ICA occlusion (and subsequent low flow) did not correlate with low N-acetylaspartate/choline ratios. CONCLUSION: Neurological deficit caused by (transient) hemispheric ischaemia is associated with low N-acetylaspartate/choline ratios, whereas prior clinical features are not associated with low cerebropetal blood flow, as measured with MR angiography. As a result, differences in cerebropetal flow cannot explain why patients with similar carotid artery disease experience different neurological features.     

Dysgenesis of the carotid artery associated with congenital ipsilateral Horner syndrome

We report a case with dysgenesis of the carotid artery associated with congenital Homer syndrome. A 6-year-old boy, who had undergone surgical repair for pulmonary atresia, ventricular septal defect, and patent ductus arteriosus at 20 months of age, presented with miosis of the left eye, and anhidrosis of the left face, neck, and shoulder girdle. Since the anhidrosis was obvious in early childhood, he was suspected as having congenital Horner syndrome. Cranial and cervical CT showed unpredicted abnormalities of the left carotid arteries, including the absence of an internal carotid artery (ICA), and hypoplasia of the common carotid and external carotid arteries. The anterior and middle cerebral arterial flow was supplied through the communicating arteries. Congenital agenesis of the ICA was highly suspected, because the left carotid canal could not be discerned at all. The concurrence of agenesis of ICA with ipsilateral Horner syndrome is accounted for by simultaneous organogenesis of the carotid artery and cervical sympathetic nerve, both of which are derived from neural crest cells. Developmental anomalies of the cervical neural crest, though rare, should be included in the differential diagnosis of congenital Homer syndrome.     

Ischaemia-induced vascular vulnerability resulting in intracerebral haemorrhage with ipsilateral internal carotid artery occlusion

Intracerebral haemorrhage accompanied with cervical internal carotid artery (ICA) occlusion on the same side without moyamoya-like vessels is rare. A 73-year-old man with left ICA occlusion and no presence of moyamoya disease criteria underwent xenon-enhanced computed tomography with acetazolamide challenge test. The findings showed hypoperfusion and no vasoreactivity in the territory of the left middle cerebral artery. During follow-up he suffered bleeding in the left frontoparietal lobe. Cerebral angiography showed left ICA occlusion and cross flow via the anterior communicating artery without moyamoya vessels. Long-term ischaemia would make perforating or anastomotic arteries vulnerable. These arteries were easily ruptured by hypertension, resulting in intracerebral haemorrhage.     

Improvements in the intraluminal thread technique to induce focal cerebral ischaemia in rabbits

Although the intraluminal thread technique has been used to induce focal cerebral ischaemia in rabbits, its success rate is not high. We, therefore, attempted to improve the stability and reproducibility of this method by using thread tips of appropriate diameter as determined from the anatomical characteristics of the carotid and cerebral arteries of New Zealand white rabbits. Following intraarterial injection of casting material, we tested threads of four different tip diameters to determine the optimal thread tip that could occlude the middle cerebral artery (MCA). 2,3,5-Triphenyltertrazolium chloride (TTC) staining showed that, consistent with the intraluminal diameter of the MCA from the arterial casts ( 0.50 +/- 0.06 mm), thread with 0.51-0.55 mm tip diameter was optimal for the occlusion of the MCA. Ability to induce focal cerebral ischaemia was also dependent on variations in the anatomy of the internal carotid artery (ICA), especially the origin of the occipital artery. Our results suggest that use of appropriately sized thread and accurate manipulation of its tip significantly improves the stability and reproducibility of this model.     

颈动脉斑块的稳定性与青中年脑梗死

目的　研究颈动脉颅外段斑块稳定性与青中年脑梗死。方法　对78例青中年脑梗死患者及6 9例对照组作颈动脉超声检查。结果　(1)青中年脑梗死组斑块检出率(5 3.9% )明显高于健康对照组(6 .6 % ) ,P<0 .0 5 ;(2 )青中年脑梗死组中不稳定斑块[软斑(37.7% )及溃疡斑(4.3% ) ]检出率高达4 2 % ,而稳定性斑块[扁平斑(4.3% )、硬斑(2 6 .1% ) ]检出率为30 .4 %。健康对照组仅2例发现斑块形成,两组比较差异有显著性(P<0 .0 5 ) ;(3)斑块好发于颈总动脉膨大处、颈内动脉起始处及颈总动脉主干;(4)青中年脑梗死组以轻、中度血管狭窄为主(7.8% ) ,老年脑梗死组以中、重度狭窄为主(36 .9% ) ,健康对照组无明显管腔狭窄。结论　青中年脑梗死患者颈动脉斑块具有不稳定性。斑块的组织学结构是影响其稳定性的内因,切应力作用是决定斑块稳定性的外因。在内因及外因的共同作用下,不稳定斑块成为青中年脑梗死的危险因素之一。     

脑血管病颈动脉粥样硬化14例病理研究

目的探讨颈动脉粥样硬化与脑血管病的关系。方法对１４例脑血管病死亡病例（脑出血及脑梗死各７例）的颈动脉进行病理观察及形态定量分析。结果脑血管病患者颈动脉粥样硬化导致管腔狭窄的程度，轻度占６３％，中、重度狭窄约占３７％。脑梗死患者颈动脉粥样硬化导致管腔狭窄的程度比脑出血患者严重；７例脑梗死患者中２例的病因为颈内动脉栓塞，脑梗死患者颈动脉粥样硬化斑块具备不稳定的组织学特性，常见质地松散、密度不均易脱落的斑块。脑出血组出血灶同侧的颈内动脉较对侧显著狭窄。结论颈内动脉栓塞是大面积脑梗死的常见病因之一；不稳定的颈动脉粥样硬化导致的斑块脱落可能也是脑梗死的病因之一。     

Internal carotid artery agenesis: diagnosis,clinical spectrum,associated conditions and its importance in the era of stroke interventions

Abstract

Background: Internal carotid artery (ICA) agenesis has been usually reported as an asymptomatic condition in association with other congenital anomalies. However, it is less well described in the context of clinical neurological syndromes.

Method: Five cases of ICA agenesis are reviewed. The diagnosis of ICA agenesis was based on the absence of bony carotid canal on computed tomography. Brain CT and magnetic resonance image (MRI) scans were done in all the patients and four vessels digital angiograms were obtained in two. Clinical presentation, coexistent radiological findings and associated abnormalities are reviewed.

Findings: The initial presentations were pulsatile tinnitus, ischemic stroke, migraine, Horner's syndrome, and subarachnoid hemorrhage. Collateral circulation was supplied via the posterior communicating artery and the anterior communicating artery. Ophthalmic artery was supplied by meningeal arteries. On CT, all cases demonstrated agenesis of the bony carotid canal. Smaller cavernous sinus were detected in all cases, enlargement of the foramen spinosum was found in three patients and hyper-pneumatization of the petrous apex was detected in two cases. In one patient a cerebral aneurysms was detected and treated with an endovascular approach. Other associated vascular abnormalities were aortic origin of the vertebral artery in two patients, ICA coiling in two cases and fenestration of basilar artery in one case.

Conclusion: ICA agenesis is usually asymptomatic but occasionally may be associated with ischemic stroke. Collateral supply is usually effective in preventing stroke but may become inefficient leading to ischemia. Associated anomalies such as cerebral aneurysms are commonly depicted on the same side as the ICA agenesis and may represent a potential life-threatening condition.     

颈动脉斑块稳定性与青中年脑梗死发病关系探讨

目的探讨颅外颈动脉粥样硬化斑块的稳定性对青中年脑梗死发病的影响及其成因。方法对96例青中年脑梗死患者和80例对照组作颈动脉超声检查。结果（1）青中年脑梗死组斑块栓出率为65．6％,不稳定斑块（软斑和溃疡斑）栓出率高达41.7％,稳定性斑块（扁平斑和硬斑）检出率为25％;健康对照组仅3例发现斑块形成,栓出率仅7．5％,均为稳定性斑块,两组比较差异显著（P〈0．05）。（2）斑块好发于颈总动脉膨大处、颈内动脉起始处及颈总动脉主干。（3）青中年脑梗死组以轻中度血管狭窄为主（25．4％）,老年脑梗死组以中、重度狭窄为主（40．5％）,健康对照组无明显管腔狭窄。结论青中年脑梗死患者颈动脉斑块具有不稳定性,影响斑块稳定性的内因是其组织结构,外因是切应力作用,二者共同作用,使不稳定性斑块成为青中年脑梗死发病的一个重要危险因素。     

Middle-aged, but not young, rats develop cognitive impairment and cortical neurodegeneration following the four-vessel occlusion/internal carotid artery model of chronic cerebral hypoperfusion

Permanent, stepwise occlusion of the vertebral arteries (VAs) and internal carotid arteries (ICAs) following the sequence VA→ICA→ICA, with an interstage interval (ISI, →) of 7 days, has been investigated as a four-vessel occlusion (4-VO)/ICA model of chronic cerebral hypoperfusion. This model has the advantage of not causing retinal damage. In young rats, however, 4-VO/ICA with an ISI of 7 days fails to cause behavioral sequelae. We hypothesized that such a long ISI would allow the brain to efficiently compensate for cerebral hypoperfusion, preventing the occurrence of cognitive impairment and neurodegeneration. The present study evaluated whether brain neurodegeneration and learning/memory deficits can be expressed by reducing the length of the ISI and whether aging influences the outcome. Young, male Wistar rats were subjected to 4-VO/ICA with different ISIs (5, 4, 3 or 2 days). An ISI of 4 days was used in middle-aged rats. Ninety days after 4-VO/ICA, the rats were tested for learning/memory impairment in a modified radial maze and then examined for neurodegeneration of the hippocampus and cerebral cortex. Regardless of the ISI, young rats were not cognitively impaired, although hippocampal damage was evident. Learning/memory deficits and hippocampal and cortical neurodegeneration occurred in middle-aged rats. The data indicate that 4-VO/ICA has no impact on the capacity of young rats to learn the radial maze task, despite 51% hippocampal cell death. Such resistance is lost in middle-aged animals, for which the most extensive neurodegeneration observed in both the hippocampus and cerebral cortex may be responsible.     

Do stroke patients with normal carotid arteries require TEE for exclusion of relevant aortic plaques?

OBJECTIVES: This study investigated (a) the hypothesis that stroke patients with aortic atheroma would show comparable atherosclerotic changes in the carotid arteries, which are easily accessible for ultrasound evaluation and (b) the possibility of carotid duplex sonography as a replacement for transoesophageal echocardiography (TEE) for the exclusion or prediction of relevant aortic plaques. METHODS: In 301 consecutive patients (mean age 62 years) with acute cerebral ischaemia, two dimensional ultrasound measurements were taken of common carotid artery intima media thickness (IMT) and maximal plaque area (PA) and the local degree of internal carotid artery (ICA) stenosis were determined. Maximal aortic wall thickness (AWT) was assessed by TEE. RESULTS: An IMT < or =0.9 mm yielded a negative predictive value (NPV) of 95.8% for exclusion of aortic atheromas > or =4 mm and an NPV of 100% for the exclusion of aortic thrombi. However, positive predictive value of IMT >0.9 mm was low (29.6%), increasing only slightly in the presence of carotid plaques (33%). Incidence of aortic thrombi was significantly higher with > or =50% compared with <50% ICA stenosis (11.3% v 3.9%, respectively). IMT and PA correlated moderately with AWT (r = 0.47, r = 0.53, respectively; p<0.001). Systolic blood pressure, coronary heart disease and peripheral artery disease, increased IMT, and ICA stenosis > or =50% were independently related to AWT > or =4 mm. CONCLUSIONS: A high NPV of normal carotid ultrasound does not support routine TEE for the exclusion of complex aortic plaques as a high risk source of cerebral embolism. However, in patients with carotid atherosclerosis, particularly in those with ICA stenosis > or =50%, TEE should be performed to exclude an additional high risk source for stroke.     

Comparison of methods eliciting cerebral ischaemic pressor response in the cat

Three methods of intercepting the blood supply to the brain were tested by means of X-ray angiography and by monitoring the pressor response following cerebral ischaemia. The methods were: (1) occlusion of carotid and basilar artery; (2) occlusion of carotids and vertebral arteries in the cervical canal of the third vertebra; (3) occlusion of carotid and subclavian arteries. The X-ray angiographs showed that in most cases we could close the accessory sources of the cerebral circulation and drastically reduce the blood supply to the brain of the cat. With all three methods the cerebral ischaemia evoked strong blood pressor elevation, which was weaker however when the carotid and basilar artery were clamped, in comparison with the other two methods. This may be explained by the existence of small arteries supplying the lower brain stem and originating intracranially from the vertebral artery near to the junction of the vertebral and anterior spinal artery.     

Clinical and neuroradiological features of internal watershed infarction and the occlusive diseases of carotid artery system

Abstract

Background: To describe the clinical and neuroradiological features of internal watershed (IWS) infarction and to analyze the relationship between IWS infarction and occlusive diseases of carotid artery system.

Methods: We identified 27 IWS infarction patients with diffusion-weighted magnetic resonance imaging by commonly used templates within 10 days after the onset. Patients with potential cardiac sources of embolism were excluded. Occlusive diseases of carotid arteries were assessed by magnetic resonance angiography or digital subtraction angiography. Baseline characteristics, clinical course, prognosis, neuroradiological features and symptomatic arteries were analyzed.

Results: Two patterns were identified: 14 patients had confluent IWS (C-IWS) infarction, and 13 patients had partial IWS (P-IWS) infarction. Twelve patients in C-IWS group and 10 patients in P-IWS group had severe stenosis (>70%) or occlusion in either the internal carotid artery (ICA) or middle cerebral artery (MCA). Occlusive diseases of ICA and non-lacunar syndrome were more prevalent in C-IWS group, while occlusive diseases of MCA and lacunar syndrome were more prevalent in P-IWS group. Concomitant small cortical lesions ipsilateral to IWS infarcts were more common in C-IWS group than in P-IWS group, and were significantly associated with ICA diseases. Clinical deterioration during the first seven days after admission and poor outcome assessed by the Modified Rankin Score 3 months after stroke were more prevalent in C-IWS group than in P-IWS group.

Conclusions: There is a relatively definite relationship between IWS infarction and occlusive diseases of carotid arteries. The distribution of symptomatic arteries (ICA or MCA) in C-IWS group is significantly different from that in P-IWS group. Both hypoperfusion and microembolism are probable mechanisms. There may be some differences in their roles in pathogenesis of C-IWS and P-IWS infarction. Microembolism may contribute C-IWS infarction in addition to hypoperfusion, which is the major pathogenesis of P-IWS infarction.     

Topographical distribution of barrier function in cervico-cephalic arteries of dog. Major cerebral arteries possess definite barrier function?

Topographic distribution of barrier function in normal canine cervico-cephalic arteries was studied using horseradish peroxidase (HRP) and Evans blue as tracers. The carotid sinus of the internal carotid artery (ICA) was conspicuously permeable to HRP when compared to other areas of major cervical arteries. The cavernous portion of the ICA also showed prominent permeation of HRP, especially through the outer surface, which is covered with venous endothelial cells. On the luminal side of the cavernous portion of the ICA, barrier deficiency was noted at angulated segments such as the carotid siphon. Intracranial segments of both ICA and vertebral arteries demonstrated incomplete barrier function of the first 1 to 4 mm from the origin of the intradural segments. These areas were considered to be transitional sites in barrier function between extra- and intracranial arteries. Focal, but definite, barrier disruption was also noted at the distal ends of the ICA and other arterial branching sites of major intracranial arteries. While opening of the interendothelial junctions was considered to be one of the mechanisms causing increased permeability in the cavernous ICA, the mechanisms for the permeation of HRP into the major cerebral arteries could not be confirmed ultrastructurally.     

Common Carotid Artery Agenesis: Duplex Ultrasonographic Findings

Background

Agenesis of the common carotid artery (CCA) resulting in separation of the origin of the external carotid artery (ECA) and internal carotid artery (ICA) from the aortic arch is rare. Fewer than 25 cases have been reported, and correlative ultrasound data were available for only 1 of them.

Case Report

A 52-year-old woman visited the hospital with a 3-day history of vertigo and headache. Color-coded duplex ultrasonography performed to evaluate the carotid and vertebral arteries revealed a normal configuration on the left side. However, the right CCA could not be found; instead, there were two vessels of approximately equal size in close proximity to each other. The cerebral angiographic findings were consistent with the ultrasonographic findings. The ECA and ICA originated directly from the brachiocephalic trunk, and the ECA arose proximal to the ICA.

Conclusions

The ultrasonographic findings revealed absence of the CCA, the ECA and ICA originating separately from the aortic arch. Color-coded duplex ultrasonography appears to be an effective and sensitive method for detecting absence of the CCA. These findings should help to further our understanding of the embryologic development of the carotid arteries.     

No evidence that severity of stroke in internal carotid occlusion is related to collateral arteries

Background/Aim

The neurological effects of internal carotid artery (ICA) occlusion vary between patients. The authors investigated whether the severity of symptoms in a large group of patients with ipsilateral or/and contralateral ICA occlusion at presentation with ocular or cerebral ischaemic symptoms could be explained by patency of other extra or intracranial arteries to act as collateral pathways.

Methods

The authors prospectively identified all patients (n = 2881) with stroke, cerebral transient ischaemic attack (TIA), retinal artery occlusion (RAO), and amaurosis fugax (AFx) presenting to our hospital over five years, obtained detailed history and examination, and examined the intra and extracranial arteries with carotid and colour‐power transcranial Doppler ultrasound. For this analysis, all those with intracranial haemorrhage on brain imaging and cerebral events without brain imaging were excluded.

Results

Among 2228/2397 patients with brain imaging (1713 ischaemic strokes, 401 cerebral TIAs, 193 AFx, and 90 RAO) who underwent carotid Doppler, 195 (9%) had ICA occlusion. Among those patients with cortical events, disease in potential collateral arteries (contralateral ICA, external carotid, ipsilateral or contralateral vertebral or intracranial arteries) was equally distributed among patients with severe and mild ischaemic presenting symptoms.

Conclusion

The authors found no evidence that the clinical presentation associated with an ICA occlusion was related to patency of other extra or intracranial arteries to act as collateral pathways. Further work is required to investigate what determines the clinical effects of ICA occlusion.     

De novo formation of an aneurysm in a case of unusual intracranial fibromuscular dysplasia

Intracranial fibromuscular dysplasia (FMD) is a vascular disease of unknown origin occurring predominantly in young women. The internal carotid artery is most often involved, but other cerebral arteries may also be affected. We report the case of a young woman presenting with an unusual angiographic appearance of intracranial FMD of the internal carotid artery (ICA) that could not be categorized into any type of the Osborn–Anderson classification. During follow up the patient presented with an intracerebral and subarachnoid hemorrhage. Repeated angiography revealed multiple aneurysms in the pathologic segment of the vessel. The patient underwent surgical treatment with clipping of the aneurysms, wrapping of the pathologic segment of the ICA and biopsy of the superficial temporal artery. Histopathological sections revealed FMD of the intimal type. ₁-antitrypsin blood levels were normal. Cases of intracranial FMD previously reported in the literature are reviewed and various aspects of this rare disease are discussed.     

脑梗死患者脑血管病变及侧支循环状态的研究

目的探讨脑梗死患者的责任病变血管及侧支循环主要方式。方法对110例脑梗死患者行牛津郡社区卒中项目（OCSP）分型,进行全脑数字减影血管造影（DSA）检查,判定梗死的责任血管、侧支循环是否存在及方式。结果各型患者,病变血管共137条,其中颈内动脉（ICA）54条（39．4％）、锁骨下．椎动脉（SUB—VA）42条（30．7％）、大脑中动脉（MCA）29条（21．2％）、颈总动脉（CCA）和基底动脉（BA）各4条（各2．9％）、无名动脉2条（1．5％）、大脑前动脉（ACA）和大脑后动脉（PCA）各1条（各0．7％）;责任血管ICA49条（44．5％）、MCA27条（24．5％）、SUB—VA19条（17．3％）及CCA3条（2．7％）、IA2条（1．8％）,余3支血管各1条（均占0．9％）。7例（6．4％）未发现异常。经软脑膜支吻合代偿59例,Willis环代偿49例,来自各种颅外代偿计27例,两种及以上方式联合代偿19例,罕见代偿3例,未发现代偿6例。结论脑动脉病变最多位于ICA、SUB-VA主干,其次位于MCA;前循环病变较后循环病变具有更高的梗死发生率。侧支循环代偿以Willis环最充分,软脑膜支吻合最常见;脑梗死的类型和预后受血管病变和侧支循环状态的综合影响。     

Unilateral internal carotid artery absence in trisomy 18

BackgroundInternal carotid artery (ICA) absence (agenesis or aplasia) is a rare congenital anomaly that is usually asymptomatic and found coincidentally. There has been no report showing a specific chromosomal abnormality causes ICA absence.Case reportsMR angiography in a Japanese male infant with trisomy 18 revealed left ICA absence with the left middle cerebral artery (MCA) and anterior cerebral artery (ACA) supplied from the ipsilateral posterior communicating artery and anterior communicating artery (ACoA), respectively, type A in Lie’s classification. Another Japanese male infant with trisomy 18 showed right ICA absence with the right ACA and MCA supplied from the ACoA, that is, type B in Lie’s classification.ConclusionThere have been no pathological or radiological reports of ICA absence in trisomy 18, however, it may be underestimated because the anomaly usually causes no clinical symptoms. It is necessary to evaluate further patients to clarify whether or not unilateral ICA absence is a characteristic congenital malformation.     

Early partial reperfusion in a new rat model of focal cerebral ischaemia

The influence of early partial reperfusion in a new rat model of focal cerebral ischaemia was investigated. Two groups, each of 30 adult male rats, were subjected to permanent occlusion of the right middle cerebral artery. The former, (group A) had an additional permanent occlusion of both common carotid arteries; the latter (group B) had a temporary carotid occlusion lasting for two hours. Mortality rate, evaluated within three days, was 70% ingroup A and 20% in group B. The mean size of cerebral infarcts was 63% in group A whereas it was 21% in group B. These data suggest that, in this animal model, early partial reperfusion is effective in reducing the mortality rate, and the size of the cerebral infarcts. Furthermore, this experimental model appears suitable for studies elucidating the role of reperfusion andlor other efforts in focal cerebral ischaemia.     

Higher cerebral function and hemispheric blood flow during awake carotid artery balloon test occlusions

OBJECTIVES: Measures capable of detecting early alterations of brain function during acute cerebral ischaemia have not been adequately defined. Internal carotid artery (ICA) test occlusions provide a well controlled environment to investigate the effects of reversible acute hemispheric hypoperfusion on brain function. A continuous time estimation task was developed that reliably demonstrated alterations in higher cerebral function before development of any deficits in elementary neurological function during ICA balloon catheter test occlusions. In the present study, we hypothesised that alterations in our behavioural task would correlate significantly with absolute level of ipsilateral CBF. METHODS: Twenty five patients underwent awake ICA test occlusions during which sustained attention and ipsilateral CBF were measured simultaneously using our time estimation task and the intracarotid 133Xe washout method. Alteration in sustained attention was correlated with CBF after occlusion using Fisher's exact test. RESULTS: Deterioration in sustained attention was significantly associated with ipsilateral CBF below 30 ml/g/min (Fisher's exact test, p=0.047). Changes in individual patients' performance on the behavioural task correlated in real time with changes occurring either at the point of occlusion or at a specific threshold of induced hypotension. Sensitivity for our behavioural test in predicting CBF was 75%; specificity 70%. CONCLUSIONS: Monitoring sustained attention during carotid balloon test occlusions seems to be a sensitive means to detect decreases in CBF as measured by 133Xe washout. Correlation between higher cerebral function and CBF can allow more detailed investigations of physiological relations between cerebral haemodynamics and brain function in human conditions of cerebral ischaemia.