A longitudinal study of collateral flow patterns in the circle of Willis and the ophthalmic artery in patients with a symptomatic internal carotid artery occlusion

BACKGROUND AND PURPOSE: The purpose of the present study was to assess whether the direction of flow via the circle of Willis and the ophthalmic artery (OphA) changed over time in patients with a symptomatic occlusion of the internal carotid artery (ICA) who did not experience recurrent cerebral ischemic symptoms. METHODS: Sixty-two patients with a symptomatic ICA occlusion were investigated within 6 months after symptoms occurred. The investigations were repeated after 6 and 12 months. The directions of flow in the A1 segment and the posterior communicating artery (PCoA), both on the side of the symptomatic ICA occlusion, were assessed with the use of magnetic resonance angiography. The pattern of collateral flow via the circle of Willis was categorized as via the A1 segment only, via the PCoA only, via the A1 segment plus the PCoA, or no collateral flow via the circle of Willis. The direction of flow in the OphA was investigated with transcranial Doppler sonography. CO(2) reactivity was determined with transcranial Doppler sonography to investigate whether changes in flow patterns were accompanied by changes in cerebrovascular reactivity. RESULTS: There were no statistically significant changes over time in the direction of blood flow in the A1 segment and the PCoA or in the pattern of collateral flow via the circle of Willis. On average, 72% of patients with a unilateral ICA occlusion (n=41) had willisian collateral flow compared with 37% of patients with a bilateral ICA occlusion (n=21; P<0.05). Patients with a unilateral ICA occlusion tended to a lower prevalence of reversed flow via the OphA over time. CO(2) reactivity did not change significantly in any patient group. In patients with a unilateral ICA occlusion, decreased CO(2) reactivity was associated with a higher prevalence of absent willisian collateral flow and a lower prevalence of collateral flow via the A1 segment plus the PCoA. CONCLUSIONS: The absence of recurrent cerebral ischemic symptoms in patients with a symptomatic ICA occlusion is not associated with an improvement in collateral flow via the circle of Willis or the OphA during 1.5-year follow-up.     

Hemodynamic flow patterns evaluated by transcranial color-coded duplex sonography after STA-MCA bypass for internal carotid artery occlusion

Extracranial-intracranial (EC-IC) bypass surgery had been widely performed for the treatment of internal carotid artery occlusion. However, it is presently difficult to predict how the bypass flow will contribute to intracranial circulation. We examined intracranial hemodynamics by transcranial color-coded duplex sonography (TCCD) after superficial temporal artery (STA)-middle cerebral artery (MCA) bypass and retrospectively studied the relationship between the postoperative contribution of the bypass flow and the preoperative collateral circulation and cerebrovascular perfusion status in 10 patients. Hemodynamics in the MCA detected by TCCD were classified into three patterns. In pattern A, perfusion of the whole MCA area is completely dependent on the bypass flow. In pattern B, perfusion of the M2 segment is dependent on the bypass flow, but perfusion of the M1 segment is independent of the bypass flow. In pattern C, perfusion of the whole MCA area is supplied by collateral flow and the bypass does not function efficiently. Preoperative absence of collateral flow via anterior communicating artery and cerebral perfusion status type 3 (reduced regional cerebral blood flow and regional cerebral vasoreactivity) seems to predict hemodynamic usefulness of the bypass flow after surgery. TCCD is an easy and noninvasive method for evaluating intracranial cerebral circulation after EC-IC bypass surgery.     

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.     

Diffusion-weighted MRI in patients with symptomatic internal carotid artery disease

Beside the early detection of ischemia, there is an increasing body of evidence that diffusion-weighted imaging (DWI) can provide important information on stroke etiology. Against the background of an increased use of magnetic resonance angiography in patients being evaluated for carotid endarterectomy (CEA), the question arises if the additional performance of a DWI scan could also yield clinically relevant findings in these patients. In a prospective observational study we analysed the DWI data of 107 patients with high-grade symptomatic carotid artery disease (CAD) being evaluated for CEA. While no patient with a retinal TIA (n = 29) exhibited a DWI lesion, nineteen of the 42 patients with a hemisphere TIA and all patients with a minor stroke (n = 36) showed DWI lesion(s). In patients with TIAs the occurrence of DWI abnormalities was significantly more frequent in patients with long lasting TIAs. The majority of patients had multiple DWI lesions suggestive of acute large-artery thromboembolism as a common morphological phenotype of stroke. The finding of a similar lesion pattern in 4 patients with additional pre-existing atrial fibrillation suggested a symptomatic carotid stenosis. In contrast, unexpected bihemisphere lesions suggested cardioembolism in two patients with a normal circle of Willis and instigated thorough cardiac investigations. In both instances 24-h Holter monitoring revealed intermittent atrial fibrillation, so that a CEA was not performed. In conclusion, we demonstrate a common DWI lesion pattern in patients with symptomatic high-grade CAD eligible for CEA. In patients with known concomitant cardiac disorders the finding of this typical lesion pattern may support the diagnosis of a symptomatic CAD. In contrast, the additional performance of DWI can also reveal an unexpected cardiac source of embolism in some patients, which can substantially influence their further clinical management.     

经颅多普勒超声评估单侧颈内动脉颅外段闭塞患者颅内侧支循环的临床意义

目的 探讨经颅多普勒超声(TCD)评估单侧颈内动脉颅外段闭塞(ICAO)患者颅内侧支循环的临床价值.方法 回顾性连续纳入2018年1月至2020年12月就诊于苏州大学附属第一医院卒中中心、行颈部血管超声检查为单侧ICAO及数字减影血管造影(DSA)证实患者145例,其中症状组109例,无症状组36例.记录TCD评估颅内...     

Cerebral blood flow and oxygen metabolism in symptomatic internal carotid artery occlusion by (traumatic) cervical artery dissection

The present study investigates whether cerebral infarction resulting from internal carotid artery occlusion by cervical dissection is due to emboli, released from a superimposed luminal thrombus, or is due to haemodynamic failure and hypoperfusion. Ten patients with a history of stroke and with a visible cerebral infarct on computed tomographic scan, due to cervical dissection and thrombosis of the internal carotid artery, were studied with positron emission tomography in order to assess the regional cerebral blood flow (rCBF), the regional cerebral metabolic rate of oxygen (rCMRO2) and the regional oxygen extraction fraction (rOEF) in different regions of the brain. rCBF and rCMRO2 were only decreased in the infarct area but not in the peri-infarct zone or elsewhere in the brain. As rOEF was not increased in the affected cerebral hemisphere, the present study suggests artery-to-artery embolism rather than a haemodynamic event as the cause of the stroke. Use of anticoagulants thus appears to be the appropriate treatment in the acute stage.     

Intravenous digital subtraction angiography: an index of collateral cerebral blood flow in internal carotid artery occlusion

The objective of this investigation was to correlate Xenon-133 inhalation rCBF measurements with the pattern of cortical arterial filling on intravenous DSA in 18 patients with unilateral internal carotid artery occlusion. Of 9 patients showing symmetrical filling of hemispheric cortical arteries, none showed an inter-hemispheric difference in rCBF ( delta Fg) greater than 10ml/100gm/min. Of 9 patients showing delayed cortical opacification ipsilateral to the internal artery occlusion, 3 showed a delta Fg greater than 10ml/100gm/min, 3 showed a delta Fg in the 7-10ml/100gm/min range, and 3 had a delta Fg less than 7ml/100gm/min. All patients with asymmetric abnormalities in the rCBF profile had the delayed pattern of cortical filling on DSA. The presence of symmetrical hemispheric opacification of cortical arteries on DSA indicates adequate interhemispheric redistribution of rCBF and patent inter-hemispheric collateral channels, but not necessarily normal cerebral blood flow. The presence of delayed cortical arterial opacification on the side of internal carotid artery occlusion does not necessarily imply significant inter-hemispheric rCBF differences, nor does it rule out a normal rCBF. The presence of bilateral reduction of rCBF and symmetrical cortical artery filling on DSA may represent an "interhemispheric steal".     

Intracerebral laser Doppler blood flow measurements compared to blood flow in porcine internal carotid artery

The aim was to validate intracerebral laser Doppler measurements: a technique with potential applications for studying cerebral microcirculation. A technique for measurements of blood flow from the internal carotid artery was developed and compared to the laser Doppler method in a pig model. Cerebral blood flow was varied using haemorrhage, high cerebrospinal fluid pressure and blood volume expansion. The coefficient of correlation between flow in the carotid artery and laser Doppler flow signals from probes in the cerebral cortex was 0.29 (P<0.005). The correlation improved using relative changes from baseline (coefficient of correlation=0.62, P<0.0001). The highest coefficient of correlation (0.85, P<0.0001) was obtained when blood flow in the right internal carotid artery and laser Doppler flow signal from the corresponding right hemisphere were compared. Laser Doppler flowmetry from intracerebral probes correlates with the internal carotid artery blood flow. Laser Doppler flowmetry from intracerebral probes may provide a simple method for continuous local blood flow measurement in the brain.     

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.     

The hemodynamic effects of internal carotid artery stenting: a study with color-coded duplex sonography

BACKGROUND: Stenting has been used as an alternative treatment for patients with internal carotid artery (ICA) stenosis. Color-coded duplex sonography (CDS) is able to measure not only the prestenting stenosis but also the poststenting hemodynamic changes. The purpose of this study was to quantify, using CDS, the hemodynamic changes after ICA stenting. METHODS: Both symptomatic and asymptomatic patients were included in this study. The degree of ICA stenosis before stenting was required to be more than 50%. Thirty-two treated ICAs were included to compare the prestenting and poststenting CDS findings, including the diameter and cross-sectional area of the lumen, the flow peak systolic and end-diastolic velocities, the resistivity index and the amount of flow in bilateral extracranial carotid and vertebral arteries. RESULTS: After stenting, the turbulent flow pattern in the stenotic ICA recovered to laminar flow, and the reversed ophthalmic flow direction normalized. Of the CDS parameters applied to evaluate the effect of stenting on ICA stenosis, the diameter, residual area, peak systolic velocity, diastolic velocity and the ration of systolic flow velocity ratio in the ICA to that in the common carotid artery (CCA) were altered significantly. The mean area and residual area of these stenotic ICAs showed increases of 24% (p = 0.005) and 84% (p = 0.001) after ICA stenting, respectively. The mean peak systolic flow velocity significantly decreased by 71%. The mean diastolic flow velocity also significantly decreased (by 77%). Both the systolic and diastolic velocities of the ipsilateral CCA significantly increased after stenting. The amount of flow in the contralateral ICA decreased significantly after stenting. The change in the amount of flow in the vertebral arteries after ICA stenting was insignificant. CONCLUSIONS: The results of this CDS study clearly demonstrated the hemodynamic changes after ICA stenting. The carotid stenting significantly changed the ICA flow pattern, diameter, residual area, peak systolic velocity and ICA to CCA velocity ratio.     

颈内动脉狭窄程度和血流速度与颈内动脉支架置入术后高灌注损伤的相关性研究

目的 探讨颈内动脉狭窄程度和血流速度与颈内动脉支架置入术后高灌注损伤的相关性。方法 选取2014年1月-2019年2月本院收治的298例颈内动脉狭窄患者为研究对象,全部患者采取颈内动脉支架置入术治疗,根据术后是否发生高灌注脑出血将其分为高灌注脑出血组(观察组,n=8)与未发生高灌注脑出血组(对照组,n=290); 采用改良RANKIN量表(mRS评分)评估2组受试者手术前、手术30 d后残疾程度,分别于手术前、手术后3 d采用彩色多普勒超声测定2组受试者患侧颈内动脉狭窄程度及血流速度,应用经颅多普勒TCD测定2组受试者患侧大脑中动脉血流速度; 采用NIHSS评分评估2组受试者手术前、手术30 d后神经功能缺损程度,采用LOGSTIC多元回归分析颈内动脉支架置入术后高灌注脑出血的影响因素。结果 观察组手术30 d后mRS评分高于对照组(P<0.05); 观察组手术前患侧颈内动脉狭窄程度高于对照组(P<0.05); 观察组手术前患侧大脑中动脉动脉血流速度(Vm)低于对照组(P<0.05); 观察组手术30 d后NIHSS评分高于对照组(P<0.05); Logistic多因素回归分析显示,颈内动脉支架置入术后高灌注脑出血与术前颈内动脉狭窄程度、血流速度、术后3 d患侧大脑中动脉血流速度(Vm)呈正相关(P<0.05),与术前患侧大脑中动脉血流速度(Vm)呈负相关(P<0.05)。结论 颈内动脉狭窄程度和血流速度是颈内动脉支架置入术后发生高灌注脑出血的独立影响因素。     

症状性和无症状性颈内动脉狭窄的大脑中动脉微栓子信号监测

目的观察症状性和无症状性颈内动脉狭窄的患者大脑中动脉微栓子信号（microembolicsig-nals,MES）阳性率及MES计数的变化,研究微栓子与临床症状和颈内动脉狭窄程度的关系。方法选取症状性颈内动脉狭窄患者26例,无症状性颈内动脉狭窄患者20例及正常对照组30例;症状性颈内动脉狭窄组又分为短暂性脑缺血发作（transient ischemic attack,TIA）组（12例）和脑梗死组（14例）;症状性和无症状性颈内动脉狭窄的患者均行DSA或CTA检查,并对颈内动脉狭窄程度进行分级;所有颈内动脉狭窄的患者均对颈内动脉狭窄同侧的大脑中动脉进行MES监测,正常对照组则对双侧大脑中动脉进行MES监测。结果有症状和无症状颈内动脉狭窄组的MES阳性率高于正常对照组（P〈0．01）;有症状颈内动脉狭窄组MES阳性率较无症状组高（P〈0．05）;TIA组和脑梗死组比较,MEs阳性率无显著性差异（P〉0．05）;症状性和无症状性颈内动脉狭窄患者,轻、中、重度狭窄三组的MES阳性率比较均有显著性差异（P〈0．05）;MES阳性患者MES计数与颈内动脉狭窄程度呈正相关（r=0．9155,P〈0．01）。结论MES多见在颈内动脉狭窄患者,特别是症状性颈内动脉狭窄的患者,是缺血性脑血管疾病发生的高危因素。     

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.