Role of collateral flow on cerebral hemodynamics in patients with unilateral internal carotid artery occlusion

The objective of this study was to evaluate the role of collateral blood flow via the anterior and posterior communicating arteries (ACoA and PCoA) and via the ophthalmic artery (OphA) on cerebral hemodynamics, metabolism, and border zone infarcts in 57 patients with unilateral symptomatic occlusions of the internal carotid artery. Collateral flow via the ACoA and PCoA was determined with magnetic resonance angiography (MRA) and collateral flow via the OphA with transcranial Doppler (TCD). Volume flow was studied with MRA, metabolism with ¹H MR spectroscopy, CO₂ reactivity with TCD, and the incidence of border zone infarcts with MRI. Compared with controls, patients had deteriorated volume flow, metabolism, and CO₂ reactivity. No differences were found between patients with and patients without collateral flow through the ACoA and/or PCoA, or between patients with or without collateral flow via the OphA. Patients without collateral flow via any of these collaterals had decreased volume flow in the middle cerebral artery, decreased N -acetylaspartate/choline, and increased lactate/ N -acetylaspartate, compared with the other patients. Patients with symptomatic internal carotid artery occlusion have deteriorated cerebral hemodynamics and metabolism. Different collateral flow patterns via the ACoA, PCoA, or OphA have no effect on the hemodynamic and metabolic parameters, as long as one of these pathways is present.     

Clinical implications of collateral middle cerebral artery flow in acute ischaemic stroke with internal carotid artery occlusion

Background and purpose: The presence of collateral middle cerebral artery (MCA) flow via the primary collateral pathway is thought to protect against the progression of cerebral ischaemia. However, there have been few reports on early clinical outcomes according to the presence of collateral MCA flow in acute ischaemic stroke (AIS) with internal carotid artery (ICA) occlusion. Therefore, we sought to investigate the early clinical outcomes and lesion patterns according to the presence of collateral MCA flows in AIS with ICA occlusion. Methods: This is a retrospective study of patients with AIS with ICA occlusion consecutively admitted to our stroke center between October 2008 and March 2010. Patients were included if they were admitted within 12 h of symptom onset with AIS and symptomatic ICA occlusion. Collateral MCA flow was defined as the presence of MCA signals from proximal M1 to distal MCA branches ipsilateral to the ICA occlusion by magnetic resonance angiography. Early neurological deterioration (END) was defined as a 4‐point increase in the National Institutes of Health Stroke Scale (NIHSS) score and persistent neurological deterioration for at least 24 h or newly developed neurological symptoms within 7 days. Results: Sixty‐five patients (42 men, 23 women) were finally included. Initial NIHSS scores were significantly lower, and favorable outcomes at 3 months were better in patients with collateral MCA flow than in those without (P < 0.001). Initial lesion patterns were different according to the collateral MCA flow. However, patients with mild AIS might more frequently deteriorate than those with moderate to severe AIS. Conclusions: In our study, collateral MCA flow reduced initial stroke severity and was associated with favorable outcomes at 3 months but did not seem to protect against END in mild AIS patients with ICA occlusion. Therefore, the results of this study suggest that mild AIS patients with ICA occlusion should be carefully managed because their conditions may deteriorate.     

Rat middle cerebral artery occlusion by an intraluminal thread compromises collateral blood flow

We compared in Wistar rats collateral blood flow through leptomeningeal anastomoses after middle cerebral artery occlusion using craniotomy (‘extravasal occlusion'), which results in a small volume of cerebral infarction, and after intraluminal thread occlusion (‘intravasal occlusion'), which produces a large volume of cerebral infarction. Simultaneous laser–Doppler flowmetry with two probes placed on the cerebral cortex was used to measure and compare collateral blood flow. Extravasal occlusion caused a cortical blood flow reduction along a gradient in lateral direction, whereas blood flow reduction after intravasal occlusion was more uniformly distributed. It is concluded that permanent intravasal occlusion compromises collateral blood flow and therefore may not be a suitable model for measuring the ability of pharmacotherapeutic agents, if any, to improve collateral blood flow acutely after middle cerebral artery occlusion. The two models can be useful for testing drugs on parenchymal neuroprotective properties. Thereby, the intraluminal technique is preferred because of the possibility to study reperfusion damage when transient occlusion is applied.     

Angiographic circulation time and cerebral blood flow during balloon test occlusion of the internal carotid artery

Angiography-based balloon test occlusion (BTO) has been empirically used to predict tolerance to permanent carotid artery occlusion. We tested the hypothesis that the laterality of the hemispheric circulation time (HCT) of the contrast medium at cerebral angiography would reflect bilateral asymmetry of the cerebral blood flow (CBF) during BTO. Thirty-one consecutive patients who underwent BTO of the internal carotid artery were retrospectively analyzed. HCT was defined as the interval between the time-to-peak in the middle cerebral artery and the cortical veins calculated using time-density curve. The difference in HCT between the occluded and nonoccluded side was calculated at the carotid or dominant vertebral angiograms obtained during BTO. We estimated the correlation between the difference in HCT and bilateral asymmetry of the CBF, which was quantitatively determined by single-photon emission computed tomography. The HCT was 5.3±1.5 seconds and regional CBF was 41.3±11.3 mL/100 g per minute in the occluded side, compared with 3.6±0.9 seconds and 48.4±14.9 mL/100 g per minute in the nonoccluded side, respectively. The difference in HCT was strongly correlated with the asymmetry ratio of the CBF (r²=0.89, P<0.0001). Angiographically based measurement of the cerebral circulation time can provide valuable information concerning cerebral hemodynamics.     

Effect of nicardipine on cerebral blood flow in hypertensive patients with internal carotid artery occlusion: A PET study.

Purpose. The objective of this study was to elucidate the effect of intravenous administration of nicardipine on the cerebral blood flow of hypertensive patients with internal carotid artery occlusion (ICAO). Patients and Methods. Six patients with ICAO and 10 normal individuals were examined by positron emission tomography. The cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen, oxygen extraction fraction (OEF) and CBF/CBV ratio were evaluated for each vascular territory and each hemisphere, and the interhemispheric asymmetry index of each parameter was also calculated. Nicardipine was administered intravenously to each patient, and the changes in CBF (DeltaCBF%) and in blood pressure (DeltaBP) were examined. Results. After the administration of nicardipine, the CBF was significantly increased in the patient hemisphere and was unchanged in the occluded hemisphere. Stepwise regression analysis disclosed that the DeltaBP and asymmetry index of OEF were significantly correlated with the DeltaCBF% in the occluded hemisphere. Conclusions. These results suggest that CBF is unchanged or increased in ICAO patients after nicardipine administration, but that excessive reduction of blood pressure may lead to CBF decrease in the patients with marked hemodynamic imbalance between the occluded and patent hemispheres. These results suggest that it is advisable not to reduce blood pressure excessively in these patients in the treatment of perioperative or acute hypertension with calcium antagonist.     

Patency and flow velocity profiles in the internal carotid artery assessed by digital subtraction angiography and Doppler studies two years after endarterectomy

A follow-up of 55 patients 2 years after a total of 60 carotid endarterectomies. Fifty-two patients who had a total of 57 endarterectomies survived the first 2 post-operative years and were re-examined using pulsed Doppler spectral analysis and intravenous digital subtraction angiography (IVDSA). One patient had died following a stroke and 2 after a cardiac infarction. The Doppler and IVDSA examinations revealed a non-symptomatic restenosis of the relevant internal carotid artery in 2 patients. There were no relevant occlusions and no symptomatic re-stenoses were detected. Spectral spreading of the Doppler signal at the site of the endarterectomy was found in 18% of the internal carotid arteries, whereas wall irregularities (diameter reduction less than 10%) were demonstrated in 25% by IVDSA. A stenosis or occlusion was found in 14 (25%) of the 57 ipsilateral external carotid arteries.     

Clinico-radiological study of collateral circulation after internal carotid and middle cerebral occlusion

The intracranial collateral channels apart from the circle of Willis have been studied angiographically in 34 patients with internal carotid artery occlusion and 19 with occlusion of the middle cerebral artery. These collaterals are present in a high percentage of cases within a week of the ictus and are more common when the stroke has developed slowly. Their presence in occlusion of the middle cerebral artery seems to offer some protection against infarction but in internal carotid artery occlusion they are less important than the circle of Willis and when present suggest inadequacy of this structure.     

Semiquantitative evaluation of ophthalmic collateral flow in carotid artery occlusion: ultrasonic doppler study

The reliability of quantitative evaluation by doppler ultrasound with regard to the ophthalmic collateral blood flow in patients with carotid artery occlusion was estimated. The ultrasonic doppler flow signals of the ophthalmic collateral flow of 54 carotid occlusions were classified into four types and three degrees--high, moderate, and low reversed flow patterns--and were compared with the angiographic findings of the collateral flow classified into three grades--good, poor, and none. With the exception of three cases, the ultrasonic doppler flow patterns of the collateral flow correlated well with the angiographic findings in 54 occluded carotid arteries.     

Patency and flow velocity profiles in the internal carotid artery assessed by digital subtraction angiography and Doppler studies three months following endarterectomy.

Pulsed Doppler spectral analysis and intravenous digital subtraction angiography have been carried out in 55 patients, three months after a total of 60 carotid endarterectomies. Five patients were operated on both sides and there were no re-operations. There were no re-stenoses and only one of the 60 internal carotid arteries was occluded. Spectral spreading of of the Doppler signal at the site of the endarterectomy was found in 52% of the internal carotid arteries, whereas wall irregularities were demonstrated in 25% by intravenous digital subtraction angiography. A stenosis or occlusion was found in 11 (18%) of the 60 ipsilateral external carotid arteries.     

Comparison of magnetic resonance angiography, duplex ultrasound, and digital subtraction angiography in assessment of extracranial internal carotid artery stenosis.

The results of a prospective study comparing ultrasound, intra-arterial digital subtraction angiography, and magnetic resonance angiography in the assessment of the degree of extracranial internal carotid artery stenosis are reported in patients with symptoms of recent carotid territory ischaemia. A total of 70 patients and 137 vessels were examined by all three techniques. The results obtained by each technique were reported blind. The mean difference (SD) for the comparison of magnetic resonance angiography and digital subtraction angiography was -0.7 (14)%, for ultrasound and digital subtraction angiography 3.1 (15)%, and for magnetic resonance angiography and ultrasound -3.8 (15)%. The level of agreement was greater for the more tightly stenosed vessels. With the assumption that the results of the digital subtraction angiogram reflect the true situation, the sensitivity and specificity in the detection of > or = 30% stenoses were 93% and 82% with ultrasound and 89% and 82% with magnetic resonance angiography; for stenoses > or = 70% 93% and 92% with ultrasound and 90% and 95% with magnetic resonance angiography; and for stenoses of 70-99% 89% and 93% with ultrasound and 86% and 93% with magnetic resonance angiography. For occlusion the values were 93% and 99% with ultrasound and 80% and 99% with magnetic resonance angiography. Increased sensitivity and specificity were obtained when analysis was confined to those vessels in which ultrasound and magnetic resonance angiography were in agreement over classification. It is thus possible to accurately categorize the degree of stenosis of the extracranial internal carotid artery from a combination of ultrasound and magnetic resonance angiography. The adoption of this combination for the investigation of patients before carotid endarterectomy removes the risk associated with conventional angiography and represents an important advance in the management of carotid stenosis.     

Internal carotid artery stenosis: comparison of duplex scan and magnetic resonance angiography with digital subtraction angiography

OBJECTIVE: We compare duplex scan (DS) and magnetic resonance angiography (MRA) with digital angiography (DGA) in respect to accuracy in measuring internal carotid artery (IC) stenosis in symptomatic patients. METHOD: Ten symptomatic patients with IC stenosis greater than 70% previously diagnosed by DS were submitted to another DS and to both MRA and DGA. Both ICs from each patient (total 20 ICs) were evaluated by physicians blinded for the results of other tests. DS and MRA were compared with DGA, using the intraclass correlation coefficient (r) and its 95% confidence interval (95% ci). For each diagnostic test, the study group (20 Ics) was also divided in surgical patients (IC stenosis between 70 and 99%) and non surgical patients, using kappa concordance coefficient (k) to compare the results. RESULTS: Main comparisons are: DS and DGA, r = 0.71 (0.4 - 0.87); MRA and DGA, r = 0.61 (0.25 - 0.82). After division into surgical vs. non-surgical groups, k = 0.857 (p < 0.0001) between DS and DGA; and k = 0.545 (p = 0.003) between MRA and DGA. Most DS and MRA errors occurred in IC sub-occlusions. CONCLUSION: The results suggest that when they are used together, DS and non-contrast MRA may substitute DGA in the evaluation of patients for IC stenosis surgery, except when there is discordance between their results or when the methods show sub-occlusive stenosis.     

Assessment of collateral blood flow in patients with distal branch occlusion of the middle cerebral artery

Purpose

Aim of this study was to evaluate the collateral blood flow between more distal branches of the middle cerebral artery (MCA) in the case of peripheral MCA branch occlusion on dynamic 4D angiograms. We sought to individually predict the finally resulting infarction volume with regard to the extent of collateral blood flow.

Impact of digital subtraction angiography on carotid evaluation

Impact of digital subtraction angiography by intravenous injection (DSAV) was examined in a private neurology clinic. In the evaluation of threatened stroke, advent of DSAV was associated with reduced use of both traditional noninvasive tests (from 100% of patients to 36%), and conventional arteriograms (from 29% to 4%). Less compelling indications were often prescreened with noninvasive tests; more compelling symptoms usually had initial DSAV. Conventional arteriograms were done for compelling indications and negative or inadequate DSAV. The average cost of evaluation was increased slightly in patients treated medically and reduced greatly in those having surgery. While cost and convenience might support such utilization, issues of quality of evaluation require consideration.     

Local cerebral blood flow during and after bilateral carotid artery occlusion in unanesthetized gerbils

Using [14C]iodoantipyrine autoradiography, we measured regional cerebral blood flow in unanesthetized gerbils subjected to 2 (n = 5) or 30 (n = 6) minutes of bilateral carotid artery occlusion or 5 (n = 6), 30 (n = 6), or 120 (n = 5) minutes of reflow after 30 minutes of occlusion. Blood pressure, respiratory rate, and blood gases were recorded, and these and other gerbils were evaluated with periodic neurologic examinations. Blood flow to structures above the level of the diencephalon ceased almost totally during occlusion. The lateral thalamus, the rostral three quarters of the hypothalamus, and the superior colliculi were also markedly ischemic. Blood flow to the brainstem and cerebellum was only slightly affected. After release of the occlusion, blood flow was restored in some of the affected areas but to levels somewhat below that in eight sham-operated gerbils. In several areas, principally column-shaped areas in the cortex as well as patchy areas in other structures, blood flow did not recover. This inhomogeneous blood flow distribution lasted at least 30 minutes after release of the occlusion. Thereafter, the inhomogeneity slowly disappeared in such a manner that blood flow to originally well reperfused areas appeared to decrease while that to poorly reperfused areas increased. During reflow, blood flow in the brainstem and cerebellum slowly and continuously decreased. We show that there is an early no-reflow phenomenon that is inhomogeneous and appears to be of vascular origin and lasts approximately 30 minutes after release of the occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Restenosis and occlusion after carotid surgery assessed by duplex scanning and digital subtraction angiography

In a study of 140 patients operated upon with 143 carotid endarterectomies (mean follow-up time 5.2 +/- 2.3 years, range 1 month - 9.3 years), vessel morphology was examined with duplex scanning in 113 patients and with digital subtraction angiography (DSA) in 82 patients. The operative mortality was 1.4%; persisting stroke morbidity 3.6% and the combined operative mortality/morbidity 5%. During the follow-up time a further 20 patients (14.5%) died, 13 had new strokes and 14 new TIAs. By life table analysis, the annual rate of stroke including the operative period was 2.7% (1.7% on the operated side and 1.0% on the non-operated side). Fourteen new occlusions (12%) of the operated carotid artery was found and restenosis (greater than 50%) in 13 patients (11.2%). Progression of the atherosclerotic disease in the contralateral non-operated carotid artery was found in 41 patients (37%) including 3 new occlusions. Agreement DSA/duplex was 88% on the operated side and 92% on the non-operated side. New strokes or TIAs on the operated side were more common in patients with occlusions or restenosis (p less than 0.05), whereas no symptoms were referable to occlusions on the non-operated side. Risk factor analysis revealed an increased risk of atherosclerotic progression on the non-operated side in smokers and those with two or more risk factors. The risk of restenosis in the operated carotid artery was higher in females (p less than 0.025).     

Stenosis of the carotid arteries in digital subtraction angiography

The quality of intravenous digital subtraction angiograms was sufficient for diagnostic evaluation in 90%. The accuracy of the method was 90% for the internal carotid artery. 40% of the internal carotid arteries showed stenoses, whereas the common and external carotid arteries were not narrowed in 90%. On behalf of these data the authors consider that i.v. DSA of the carotid vessels is a suitable screening method for carotid arterial occlusive disease.