Local hemodynamics at the rupture point of cerebral aneurysms determined by computational fluid dynamics analysis

Background: Cerebral aneurysms carry a high risk of rupture and so present a major threat to the patient's life. Accurate criteria for predicting aneurysm rupture are important for therapeutic decision-making, and some clinical and morphological factors may help to predict the risk for rupture of unruptured aneurysms, such as sex, size and location. Hemodynamic forces are considered to be key in the natural history of cerebral aneurysms, but the effect on aneurysm rupture is uncertain, and whether low or high wall shear stress (WSS) is the most critical in promoting rupture remains extremely controversial. This study investigated the local hemodynamic features at the aneurysm rupture point. Methods: Computational models of 6 ruptured middle cerebral artery aneurysms with intraoperative confirmation of rupture point were constructed from 3-dimensional rotational angiography images. Computational fluid dynamics (CFD) simulations were performed under pulsatile flows using patient-specific inlet flow conditions. Time-averaged WSS (TAWSS) and oscillatory shear index (OSI) were calculated, and compared at the rupture point and at the aneurysm wall without the rupture point. We performed an additional CFD simulation of a bleb-removed model for a peculiar case in which bleb formation could be confirmed by magnetic resonance angiography. Results: All rupture points were located at the body or dome of the aneurysm. The TAWSS at the rupture point was significantly lower than that at the aneurysm wall without the rupture point (1.10 vs. 4.96 Pa, p = 0.031). The OSI at the rupture point tended to be higher than at the aneurysm wall without the rupture point, although the difference was not significant (0.0148 vs. 0.0059, p = 0.156). In a bleb-removed simulation, the TAWSS at the bleb-removed area was 6.31 Pa, which was relatively higher than at the aneurysm wall (1.94 Pa). Conclusion: The hemodynamics of 6 ruptured cerebral aneurysms of the middle cerebral artery were examined using retrospective CFD analysis. We could confirm the rupture points in all cases. With those findings, local hemodynamics of ruptured aneurysms were quanti-tatively investigated. The rupture point is located in a low WSS region of the aneurysm wall. Bleb-removed simulation showed increased WSS of the bleb-removed area, associated with the flow impaction area. Although the number of subjects in this study was relatively small, our findings suggest that the location of the rupture point is related to a low WSS at the aneurysm wall. Further investigations will elucidate the detailed hemodynamic effects on aneurysm rupture.     

Does calcium deposition play a role in the stability of atheroma? Location may be the key

BACKGROUND: Rupture of vulnerable atheromatous plaque in the carotid and coronary arteries often leads to stroke and heart attack respectively. The role of calcium deposition and its contribution to plaque stability is controversial. This study uses both an idealized and a patient-specific model to evaluate the effect of a calcium deposit on the stress distribution within an atheromatous plaque. METHODS: Using a finite-element method, structural analysis was performed on an idealized plaque model and the location of a calcium deposit within it was varied. In addition to the idealized model, in vivo high-resolution MR imaging was performed on 3 patients with carotid atheroma and stress distributions were generated. The individual plaques were chosen as they had calcium at varying locations with respect to the lumen and the fibrous cap. RESULTS: The predicted maximum stress was increased by 47.5% when the calcium deposit was located in the thin fibrous cap in the model when compared with that in a model without a deposit. The result of adding a calcium deposit either to the lipid core or remote from the lumen resulted in almost no increase in maximal stress. CONCLUSION: Calcification at the thin fibrous cap may result in high stress concentrations, ultimately increasing the risk of plaque rupture. Assessing the location of calcification may, in the future, aid in the risk stratification of patients with carotid stenosis.     

Interrelation between plaque surface morphology and degree of stenosis on carotid angiograms and the risk of ischemic stroke in patients with symptomatic carotid stenosis. On behalf of the European Carotid Surgery Trialists' Collaborative Group

BACKGROUND AND PURPOSE: The risk of ischemic stroke distal to an atherothrombotic carotid stenosis increases with the degree of stenosis. The main mechanism of stroke is thought to be embolism from fissured or ruptured plaque, but there are few published data on the relationship between plaque morphology and severity of stenosis and their independent effects on the risk of ischemic stroke. We sought to determine the interrelation between plaque surface morphology, degree of carotid stenosis, and the risk of ipsilateral ischemic stroke. METHODS: Severity of stenosis and plaque surface morphology were assessed on angiograms of the symptomatic carotid artery in 3007 patients in the European Carotid Surgery Trial and were related to baseline clinical characteristics, pathological characteristics of plaques examined at endarterectomy, and the risks of carotid territory ipsilateral ischemic stroke and other vascular events on follow-up. RESULTS: The early risk of ipsilateral ischemic stroke on medical treatment was closely related to the degree of carotid stenosis. However, the initial degree of carotid stenosis was not predictive of strokes occurring >2 years after randomization. Angiographic plaque surface irregularity and plaque surface thrombus at endarterectomy increased in frequency as the degree of stenosis increased (both P<0.0001). However, the degree of stenosis was still predictive of the 2-year risk of stroke on medical treatment after correction for plaque surface irregularity. Angiographic plaque surface irregularity was an independent predictor of ipsilateral ischemic stroke on medical treatment at all degrees of stenosis (hazard ratio=1.80; 95% CI, 1. 14 to 2.83; P=0.01). This relationship was maintained when the analysis was confined to strokes occurring >2 years after randomization (hazard ratio=2.75; 95% CI, 1.30 to 5.80; P=0.01). Neither the degree of stenosis nor plaque surface irregularity was predictive of the "background" stroke risk after endarterectomy or the risk of nonstroke vascular events. CONCLUSIONS: Angiographic plaque surface irregularity is associated with an increased risk of ipsilateral ischemic stroke on medical treatment at all degrees of stenosis. The increase in stroke risk with degree of stenosis is partly accounted for by the parallel increase in plaque surface irregularity and thrombus formation, but the degree of narrowing of the vessel lumen is still an independent predictor of ischemic stroke within 2 years of presentation.     

B-mode ultrasound and spiral CT for the assessment of carotid atherosclerosis

More studies on the natural history of carotid artery plaques are needed to predict more reliably which plaque types or features are the most dangerous (see Table 2). Studies on carotid and coronary endarterectomy specimens indicate a dynamic process of rupture, thrombus formation, healing, and remodeling of the plaque. A plaque from a symptomatic patient may not show any signs of plaque rupture if the plaque has healed or evolved since the debut of symptoms. Selection of high-risk symptomatic patients with carotid atherosclerosis for medical or surgical treatment requires reliable, noninvasive, and cost-effective imaging methods. B-mode ultrasonography can be used for detection of early (IMT) as well as late (plaque morphology) atherosclerotic disease. Plaque morphology evaluation on spiral CT imaging is only for research and not yet for clinical use. Asymptomatic patients with carotid atherosclerosis hardly benefit from surgical treatment, as the minimal decrease in ischemic stroke risk is almost equal to the risk of perioperative stroke or death. A high degree of carotid stenosis measured using conventional angiography is an accepted risk factor for stroke but does not identify all vulnerable plaques. Echolucency on ultrasound B-mode imaging can be included as an important parameter in this risk stratification, as it appears to predict rupture-prone, lipid-rich plaques in the mild to severely stenotic carotid artery of a symptomatic patient. The subjective evaluation of plaque morphology on B-mode ultrasound should be complemented or substituted with objective evaluation such as videodensitometric analysis. This method is commercially available and is a relatively cheap and investigator-independent solution, but more studies are required to determine the exact contribution of echolucency to stroke risk. Furthermore, the evaluation of plaque morphology using ultrasound B-mode is still subject to large variations and observer-dependence, limiting its clinical use. In contrast, carotid IMT measurements are reliable to monitor progression and regression of early carotid disease as well as the impact of interventions. This method, however, suffers when used in severely diseased vessels where the boundaries of the IMT complex are hard to distinguish in all segments of the artery. Spiral CT imaging is a preliminary test for plaque characterization, as it primarily identifies calcification but not the more relevant lipid component. Moreover, it is time and resource demanding and involves use of both contrast and radiation, increasing the risk of allergic events and cancer. Standardization and continuous quality control are important, as are consensus agreements on how to quantify lesions (especially IMT), calibrate and standardize B-mode images and outline the plaque, and analyze data. The development of imaging methods for atherosclerotic research is currently fast and promising. This progress is most necessary, considering the very high demands for surrogate endpoints and risk markers in clinical intervention studies. Whether ultrasonic plaque characterization can be implemented in broad general clinical practice, for example, in screening of individuals at high risk of developing atherosclerosis and ischemic events, has to be based upon data from large prospective studies with long-term follow-up. IMT is already used in population screening, as in the ARIC study [9,101].     

Relationship of lumen diameter to type and degree of arterial remodeling at sites of expanding wall or plaque thickness in human carotid artery

BACKGROUND: Arterial remodeling exhibits a bidirectional capacity. Whether lumen size affects remodeling response to lesion change is unknown. METHODS: Prospective study by duplex ultrasonography over 2 years in 61 subjects with coronary artery disease. Direction and magnitude of vessel remodeling are calculated for internal carotid, bifurcation, and common carotid artery segments. RESULTS: A linear trend is discernible between lumen diameter and direction and magnitude of remodeling at sites of expanding intima-media thickness (IMT) or plaque. Rate of lesion change varied inversely with lesion thickness with an inflection between rates for low-dimension IMT and plaque. CONCLUSIONS: Dilatation versus shrinkage in the remodeling response to expanding lesions appears related to lumen size. IMT and plaque exhibit independent biologies.     

颈动脉粥样硬化不稳定斑块异质性的病理研究及高分辨MRI影像特点分析

目的通过对颈动脉粥样硬化（CAS）不稳定斑块内不同成分的病理研究，分析斑块异质性红斑块不稳定化过程中的作用，及其高分辨MRI影像特点，为颈动脉内膜切除术（CEA）术前判断斑块稳定性及防止斑块不稳定化和术后再狭窄提供参考。方法对经CEA手术获取的CAS斑块进行H-E和Masson染色，观察斑块内纤维帽、脂质坏死池、出血、钙化和纤维化等成分的特点，并与术油颈动脉高分辨MRI影像时照，分析其影像学特征。结果共取得28块斑块，均为复杂性斑块，纤维帽不完整，存在不同程度的脂质坏死池和纤维化，其中16例出现斑块内出血，19例出现斑块内钙化；斑块内不同成分具有不同的高分辨MRI影像特征。结论不稳定斑块的主要特征在于其病理成分的异质性，即纤维帽的破损、广泛的脂质坏死、斑块内出血、弥漫性钙化和纤维化等成分并存，斑块的异质性是导致其易于产生栓子或诱发血栓形成、晚期呈急性进展并迅速发展为颈动脉闭塞等临床特征的主要原因，也是其高分辨MRI影像特点的主要形成原因。     

Endovascular treatment of carotid dissecting aneurysms.

BACKGROUND AND PURPOSE: Cervical arterial dissection is a well-recognised cause for acute ischaemic stroke. Dissecting aneurysms commonly occur in the affected vessels contributing to the clinical presentation. Persistence of these aneurysms may provide a source of future embolic events as well as causing local symptoms or even be at risk of spontaneous rupture. METHODS: We describe 4 patients with traumatic internal carotid artery (ICA) dissections with aneurysm formation at the skull base. Three of the 4 patients still had carotid aneurysms on follow-up investigations and so underwent endovascular procedures using stenting and coil techniques. The carotid aneurysm resolved spontaneously in the fourth patient. RESULTS: The endovascular procedures resulted in significant reduction or obliteration of the flow within the carotid aneurysms with restoration of the true lumen diameter in the adjacent ICA in all 3 patients. No perioperative complications were experienced except for transient headache in 2 patients. CONCLUSIONS: In patients with persistent aneurysms the exact risk of subsequent ischaemic events remains unknown and prospective long-term studies are needed to ascertain this risk. If recurrent stroke rates are found to be high, then carotid stenting (with or without coil insertion) is a feasible invasive approach which could be considered in these patients.     

Recently occluded intracranial and extracranial carotid arteries. Relevance of the unstable atherosclerotic plaque.

BACKGROUND AND PURPOSE: It is now widely accepted that thrombotic coronary artery occlusion usually follows rupture of an unstable atherosclerotic plaque. The significance of such instability in arteries supplying the brain is less well appreciated. We therefore describe the clinical and pathological features of recent, symptomatic internal carotid artery occlusion to examine the pathogenetic role of plaque instability at both extracranial and intracranial sites. METHODS: Cases were selected from a consecutive series of 188 adult neuropathology autopsies. In 90 of these, the principal neuropathological abnormality was cerebral infarction, in 14 cases due to recent occlusion of 1 or more segments of the internal carotid artery. In each case, a full systemic, cardiovascular, and neuropathological autopsy was performed. Plaque instability was assessed by the presence or absence of a large, necrotic, lipid core; a thin, fibrous cap; and superficial inflammation. RESULTS: Of the 14 cases, 3 showed extracranial (carotid sinus), 7 intracranial, and 4 both extracranial and intracranial carotid artery occlusion. In 6 of the 7 occluded carotid sinuses, thrombus overlay an ulcerated, unstable, atherosclerotic plaque. In 1 extracranial and all 11 intracranial occlusions, there was either no atheroma or a mildly stenotic, stable, fibrous plaque, and in these cases, the cause of occlusion was embolism (8 cases), giant-cell arteritis (1 case), and unknown (3 cases). CONCLUSIONS: Coronary-type rupture of an unstable atherosclerotic plaque is the usual cause of fatal occlusion of the carotid sinus, but other causes usually underlie intracranial carotid occlusion. The nature and consequences of intracranial atherosclerosis require further study.     

磁共振颈动脉斑块成像技术的现状 与进展

颈动脉是动脉粥样硬化斑块易发部位,其脱落会导致下游血管的阻塞并引发卒中。由于优
秀的软组织对比度和较高的空间分辨率,磁共振影像可以提供颈动脉斑块易损性的直接证据。本文
将从临床应用需求的角度出发介绍磁共振颈动脉斑块成像和图像处理的关键技术,希望有助于从事
斑块的临床和研究的人员了解目前的成像方法和未来趋势。     

Determinants of carotid plaque occurrence. A long-term prospective population study: the San Daniele Project

BACKGROUND: Increased carotid intima media thickness (CIMT) is frequently associated with established modifiable and non-modifiable cardiovascular risk factors, and is thought to be an independent predictor of ischemic cerebrovascular and cardiac events. The presence of carotid plaque is considered an established feature of atherosclerosis. There exist few longitudinal data on the predictive role of CIMT in the occurrence of carotid plaque. METHODS: We restudied the survivors of a cohort of the San Daniele Project, a large randomized general population study, investigated in 1990 regarding the prevalence and determinants of carotid atherosclerosis. Using ultrasonography, we determined in 1,193 subjects (548 men and 645 women), the common carotid IMT and the presence of non-stenotic and stenotic plaque. RESULTS: In 795 subjects without plaques or previous ischemic events at baseline, we found in multivariate analysis that CIMT > or =1 mm, age, hypertension and history of smoking are significant predictive elements of the occurrence of a new carotid plaque. The incremental probability of plaque occurrence is greater in midlife. CIMT and age are the most predictive risk factors with ORs of 3.66 (95% CI 1.4-9.4) and 3.02 (95% CI 2.4-3.7), respectively. The ORs for hypertension and smoking account for 1.5 (95% CI 1.1-3.4) and 1.7 (95% CI 1.1-2.8), respectively. CONCLUSIONS: Age, hypertension, history of smoking and B-mode detection of CIMT increases in subjects without carotid atherosclerosis and free of previous vascular events predict the occurrence of carotid atherosclerotic plaque.     

Three-dimensional power-mode ultrasound for quantification of the progression of carotid artery atherosclerosis

Elucidation of the dynamic nature of plaque progression has important implications for clinicians. The present study sought to establish an in vivo method for visualizing structural changes in carotid plaques. Three-dimensional reconstruction of parallel two-dimensional gray-scale B-mode ultrasound combined with power-mode examination of 38 carotid artery plaques was performed in a prospective study of 32 patients (18 men, 14 women; mean age 67.5 ± 7.6 years). Initial mean plaque volume was 391 μl. After a mean of 18.9 months carotid artery plaque progression had occurred in 15% of carotid artery plaques, with plaque volume increasing 59% in these cases. Plaque volume remained constant, within a range of ± 20% in 85% of cases. Progressive plaques were predominantly hypoechoic (3/5 cases) or had an ulcerated surface in cases of a hyperechoic echogenicity (2/5 cases). Risk factors and drug therapy were unrelated to plaque progression. This study illustrates that the combination of three-dimensional ultrasound with power-mode imaging improves the separation of the intraluminal plaque surface from the vessel lumen. Three-dimensional reconstruction of atherosclerotic carotid artery plaques enables the reproducible quantification of plaque volume and is therefore an excellent technique for longitudinal trials assessing progression or regression of carotid artery disease. Received: 14 January 1999/Received in revised form: 27 August 1999/Accepted: 15 October 1999     

脑梗死患者颈动脉颅外段狭窄危险因素分析

目的:探讨脑梗死患者颈动脉颅外段狭窄的相关危险因素,为脑梗死发病机制、临床诊断、治疗和预防提供重要依据。方法:应用HDI-5000彩色多普勒超声仪对脑梗死患者的颈动脉颅外段进行检测,观察血管解剖形态,内膜情况,有无斑块形成及斑块大小,管腔是否狭窄和狭窄程度。按颈动脉超声检测结果将脑梗死患者分为狭窄组和非狭窄组,进行相关危险因素分析。结果:年龄、男性、糖尿病、高血压、高TG、高apoB和高Fib与脑梗死患者颈动脉颅外段狭窄呈正相关,高HDL-C与脑梗死患者颈动脉颅外段狭窄呈负相关。结论:脑梗死患者颈动脉颅外段狭窄的危险因素有年龄、性别、糖尿病、高血压病、高TG、高APOB和高Fib,保护因素有高HDL-C。     

颈动脉粥样硬化斑块与脑梗死关系的高分辨磁共振研究

目的探讨高分辨磁共振(MRI)对颈动脉粥样硬化斑块与脑梗死关系的评估价值。方法选取驻马店市精神病医院2014-01—2016-01收治的32例经高分辨MRI检查证实的脑梗死患者为试验组,以同期我院体检的行MRI扫描的25例无脑梗死患者作对照(对照组),采用三维时间飞跃法(3D-TOF)、T1加权(T1WI)、T2加权(T2WI)及增强颈部血管成像等扫描序列,分析颈动脉斑块的成分、分型及其与脑梗死的关系。结果试验组有颈动脉粥样硬化斑块者30例(93.75%),无颈动脉粥样硬化斑块者2例(6.25%);对照组有颈动脉粥样硬化斑块者6例(24.00%),无颈动脉粥样硬化斑块者19例(76.00%);试验组颈动脉粥样硬化斑块的发生率明显高于对照组(P0.01)。试验组共发现60块颈动脉粥样硬化斑块,其中Ⅰ~Ⅱ型7块(11.67%),Ⅲ型8块(13.33%),Ⅳ~Ⅴ型19块(31.67%),Ⅵ型21块(35.00%),Ⅶ型2块(3.33%),Ⅷ型3块(5.00%);对照组共发现14块颈动脉粥样硬化斑块,以稳定性斑块为主,Ⅰ~Ⅱ型13块(92.86%),Ⅳ型1块(7.14%)。2组颈动脉不稳定斑块发生率比较差异有统计学意义(P0.05)。脑梗死患者颈总动脉、分叉处及颈内动脉3个部位的粥样硬化斑块分布情况差异无统计学意义(P0.05)。结论高分辨MRI可清晰显示颈动脉粥样斑块的内部成分,且颈动脉粥样硬化斑块与脑梗死的发生有密切的相关性,高分辨MRI可对脑梗死的发生风险作出预测,为临床防治脑梗死及疗效评价提供重要的影像学依据。     

血压和心率对颈动脉管壁切应力影响的初步研究

目的 研究血压、心率对颈总动脉管壁切应力（wall shear stress,WSS）的影响。方法 16例健康志愿者的双侧颈动脉分别行磁共振（magnetic resonance,MR）扫描,在颈动脉分叉部位下2 cm颈总动脉平面上,把颈总动脉壁平均分为24等份,利用相位对比MR成像和三维抛物面模型拟合的方法,计算每个空间位置一个心动周期内的平均WSS以及空间位置上最小的WSS。观察收缩压、舒张压、平均动脉压、心率对颈动脉血流动力学参数的影响。结果 16例健康志愿者的32条血管中,有3条血管因伪影排除在本研究之外。对剩下的29条血管进行分析,无论是双侧颈动脉,还是左侧或右侧颈动脉,平均WSS及空间位置上最低WSS与收缩压、舒张压、平均动脉压、心率均无明显相关性（P>0.05）。结论 健康志愿者颈总动脉平均WSS和最低WSS与血压、心率无明显相关。     

影响颈动脉粥样硬化易损斑块对称性分布的危险因素分析

目的探讨影响颈动脉粥样硬化斑块对称性分布的危险因素。方法前瞻性入组81例缺血性卒中患者作为研究对象,均进行了颈动脉多对比序列、黑血、高分辨磁共振成像(magnetic resonance imaging,MRI)。根据MRI结果将患者分为颈动脉无易损斑块组(40例)、单侧易损斑块组(26例)和双侧易损斑块组(15例)。记录患者年龄、性别、高血压、糖尿病、目前吸烟史、血压值、脉压、体质指数(body mass index,BMI)和血脂水平等临床资料。采用Logistic回归分析颈动脉易损斑块形成的危险因素。结果单因素分析显示,无易损斑块组、单侧易损斑块组和双侧易损斑块组患者在高血压病史、目前吸烟史、体质指数、收缩压等方面差异具有显著性。多因素Logistic回归分析显示,目前吸烟史是易损斑块对称性分布的独立影响因素[比值比(odds ratio,OR)3.136,95%可信区间(confidence interval,CI)1.122~8.766,P=0.03]。结论目前吸烟史与颈动脉易损斑块的对称性分布有相关性。     

The unstable plaque

Ischaemic strokes and transient ischaemic attacks are commonly caused by cerebral embolism originating from formation of a platelet-rich thrombus superimposed on an atherosclerotic plaque or by atherothrombotic plaque rupture in a carotid or intracranial artery. Despite advances made through ultrasound imaging in our understanding of atherosclerotic plaque progression and regression, the issue of whether differences in plaque structure alone can distinguish between lesions that become symptomatic and others that remain clinically silent continues to be debated. Recent biochemical and imaging studies have identified characteristics that may reflect a high risk of vulnerability, such as outward, abluminal plaque remodelling, the presence of intra-plaque haemorrhage, inflammation, severe flow disturbances around the encroaching lesion, plaque cap thinning and ulceration, and abnormal plaque motion. Plaque stability may be improved through management of traditional cardiovascular risk factors or with biological or pharmacological agents that target pathways involved in plaque pathophysiology. Unstable plaques place patients at risk of unpredictable ischaemic events and in patients with such lesions, specific preventive treatment beyond long-term antiplatelet therapy can be used to prevent new or recurrent events.     

Four-dimensional ultrasonographic characterization of plaque surface motion in patients with symptomatic and asymptomatic carotid artery stenosis.

BACKGROUND AND PURPOSE: In vitro studies of atherosclerotic plaque fracture mechanics suggest that analysis of local variations in surface deformability may provide information on relative vulnerability to plaque fissuring or rupture. We investigated plaque surface deformations in patients with symptomatic and asymptomatic carotid artery disease using 4-dimensional ultrasonography and techniques for measuring optical flow. METHODS: Four-dimensional ultrasound examinations of carotid artery plaques were performed in 23 asymptomatic and 22 symptomatic patients with 50% to 90% stenosis of the internal carotid artery. Plaque surface motion during 1 cardiac cycle was computed with a hierarchical model-based motion estimator. Results were compared with plaque echogenicity and surface structure. RESULTS: Of the 45 patients examined, plaque surface motion estimates were obtained for 18 asymptomatic and 13 symptomatic patients. There were no significant differences in echogenicity or surface structure of asymptomatic and symptomatic plaques (P>0.05). Results of motion estimation showed that asymptomatic plaques had surface motion vectors of equal orientation and magnitude to those of the internal carotid artery, whereas symptomatic plaques demonstrated evidence of inherent plaque movement. There was no significant difference in maximal plaque velocity between symptomatic and asymptomatic plaques (P<0.14). Maximal discrepant surface velocity (MDSV) in symptomatic plaques was 3.85+/-1.26 mm/s (mean+/-SD), which was significantly higher (P<0.001) than MDSV of asymptomatic plaques with 0.58+/-0.42 mm/s (mean+/-SD). CONCLUSIONS: ++MDSV of carotid artery plaques is significantly different in asymptomatic and symptomatic disease. Further studies are warranted to determine whether plaque surface motion patterns can identify vulnerable plaques in patients with carotid artery stenosis.     

颈动脉粥样硬化斑块无创性高分辨力磁共振成像研究进展

颈动脉粥样硬化性狭窄与脑卒中复发密切相关。目前颈动脉狭窄的治疗方法主要包括药物治疗和外科手术(颈动脉支架成形术和颈动脉内膜切除术)。脑卒中预防在于识别颈动脉狭窄危险因素,筛查脑卒中复发高危患者,从而使其从药物治疗或外科手术中获益,然而目前仅根据颈动脉狭窄程度制定治疗方案,缺乏个体化治疗。近年来,新型影像学技术如无创性高分辨力磁共振成像(HRMRI)等,可以检测出颈动脉易损斑块。与传统数字减影血管造影术测量的颈动脉狭窄程度相比,无创性HRMRI可以根据颈动脉斑块特征准确预测同侧脑卒中风险,从而指导个体化治疗。     

Risk factors for periprocedural complications in carotid artery stenting without filter protection

Introduction In highgrade stenosis, carotid artery stenting (CAS) may be chosen as an alternative to carotid surgery. Ischemic periprocedural complications may be documented best with diffusion–weighted MRI (DWMRI). In this prospective study serial DW–MRI and color–coded duplex sonography (CCDS) were used to identify carotid stenosis, which is associated with an increased risk of ischemic events due to CAS. Methods High resolution DW–MRI were performed in 74 out of 77 patients before and after CAS. All MRI scans were analyzed in a blinded manner. With CCDS each carotid stenosis was evaluated according to the grade, length, echo properties and plaque surface. Results In 42 out of 74 patients (56.8 %) a total of 188 new procedure– related DWI–lesions could be detected, while in 32 patients MRI–controls remained normal. Of the lesions 79.25 % had a size < 1 cm. In one major and two minor strokes due to CAS (total complication rate 3.9 %) corresponding territorial infarcts could be demonstrated. A highly significant correlation was found between the length of the stenosis and the incidence of new DWI–lesions (p = 0.0141). In contrast, neither the grade of ICA stenosis nor the sonographic plaque morphology or plaque surface correlated with the number of DWI–lesion in postinterventional scans. Conclusions The length—and not the degree—of an ICA stenosis seems to be the most decisive sonographic factor for estimating the periprocedural risk of embolism. DWI–lesions are much more frequent than clinical complications and may represent an important surrogate marker for improving the techniques of carotid artery stenting, especially comparing the benefit of different mechanical protection devices.     

Tic Movement of Thyroid Cartilage as a Cause for Localized Cerebral Embolism: Mimics of Embolic Stroke of Undetermined Source with Non-Stenotic Carotid Plaque

Several studies have suggested that non-stenotic carotid plaque was a risk factor for embolic stroke of undetermined source in some patients. However, individual backgrounds of these patients is unclear. We encountered a 64-years-old female with cerebral emboli, from an apparently stable non-stenotic carotid plaque (only 1.42mm thick) at the distal left common carotid artery, caused by violent tic movement of thyroid cartilage under well controlled dyslipidemia. Even though the plaque appeared thin and stable, mechanical stimulation could cause multiple, unnaturally localized emboli by stimulation-induced atherogenesis and plaque rupture, resulting in a misdiagnose of embolic stroke of undetermined source with non-stenotic carotid plaque.