脑缺血与白质损伤的研究进展

脑血管病具有发病率、致残率、病死率及复发率高的特点,其中缺血性脑血管病的发病率占45．5％～75．9％.因此,对缺血性脑血管病的治疗已成为医学界和社会关注的热点.目前对缺血性脑血管病的治疗,主要集中在改善脑血流,抢救缺血半暗带和神经功能保护方面.     

缺血半暗带的检测MRI还是PET?

缺血半暗带概念的提出为缺血性卒中的超早期治疗明确了方向,但在如何迅速准确获得半暗带信息,即如何选择半暗带的测量方法时,是采用弥散加权成像/灌注加权成像不匹配,还是采用正电子发射体层摄影尚存争议。文章就此问题做了回顾。     

缺血半暗带的检测 MRI还是PET？

缺血半暗带概念的提出为缺血性卒中的超早期治疗明确了方向，但在如何迅速准确获得半暗带信息，即如何选择半暗带的测量方法时，是采用弥散加权成像催注加权成像不匹配，还是采用正电子发射体层摄影尚存争议。文章就此问题做了回顾。     

缺血半暗带的研究进展

缺血性卒中的治疗靶应当是可逆的半暗带部分。PET和MRI技术有助于确认半暗带的存在。缺血半暗带的主要代谢特点是葡萄糖利用率增高和ATP水平逐渐下降。由兴奋性氨基酸介导的钙积聚、多形核白细胞 (PMN)积聚导致的微血管受累、梗死周边去极化以及细胞凋亡是促使半暗带发展的可能机制。这些机制因不同个体具有差异。今后有可能在成像技术的指导下确认半暗带 ,把握好治疗时间窗 ,根据不同个体的状况 ,确定有效的治疗方法     

多模式磁共振成像在急性缺血性卒中治疗中的研究进展

随着诊断技术的进步,凭借多模式影像学评估缺血半暗带,根据组织窗指导临床治疗更有优势的证据越来越多。MR技术被广泛应用于急性缺血性卒中的早期诊断,近年来,依据MR不匹配模式判断缺血半暗带,指导再灌注治疗的安全性和有效性得到证实。该文就多模式MR指导急性缺血性卒中治疗研究进展进行综述。     

缺血半暗带的神经影像学判定

精确地判断缺血半暗带的存在 ,是临床治疗缺血性卒中成功与否的关键。为此 ,文章对缺血半暗带的血流阈值、常规正电子发射体层摄影术及特殊显像剂的应用、功能磁共振及其他相关神经影像学检查方法作了介绍     

成纤维细胞生长因子与卒中后血管发生

增加缺血半暗带脑血流有利于促进神经功能恢复.成纤维细胞生长因子与卒中后血管发生密切相关,可使缺血半暗带脑血流得到改善,从而促进神经功能恢复.其应用将成为治疗缺血性卒中的一种新方法.     

超早期成像在缺血性卒中治疗处理中的作用

缺血性卒中始终是残疾或死亡的一个重要原因。目前急性缺血性卒中的治疗选择包括静脉溶栓或血管内治疗,其目的是使近端动脉闭塞再通。迅速确定卒中的可能病因或机制有益于紧急治疗方案的选择。超早期成像在显示卒中病理生理学和制订合理的卒中治疗方案中起着必不可少的作用。缺血性卒中的超早期影像学检查可证实近端血管闭塞、代偿性侧支循环、残存或侧支组织灌注,区别缺血核心区与缺血半暗带。缺血区域,包括核心区和半暗带(多重模式CT或MRI显示的各种不匹配模式)的鉴别有可能优化目前的脑缺血治疗策略。超早期影像学检查的诊断和治疗作用已使之成为缺血性卒中评价和处理的一个关键组成部分。     

缺血半暗带的神经影像学判定

精确地判断缺血半暗带的存在，是临床治疗缺血性卒中成功与否的关键。为此，文章对缺血半暗带的血流阈值、常规正电子发射体层摄影术及特殊显像剂的应用、功能磁共振及其他相关神经影像学检查方法作了介绍。     

雌激素与缺血性脑卒中关系研究进展

<正>缺血性脑卒中是一种常见的神经系统疾病,随着缺血性脑卒中的发病率逐年升高以及治疗方法的欠缺,学者们开始关注于寻找新的治疗出路。近年来的研究表明,雌激素对神经系统具有保护作用。现就目前国内外学者对雌激素与缺血性脑卒中关系的研究进展,作一综述。1缺血性脑卒中与雌激素脑动脉血流中断致神经细胞的不可逆损害过程,是一种非常复杂的缺血性级联反应。主要涉及以下几个机制:(1)兴奋性中毒和离子失衡;(2)氧化或亚硝基化作用;(3)类程序性细胞凋亡。当缺血中心区血流中断时,ATP不足,电解质失衡,代谢紊乱等情况十分严重,以致神经细胞可在数分钟内死亡。在缺血半暗带区域,因侧支循环的代偿供血,损伤较轻,缺血早期半暗带常占整个缺血区的1/2～1/3,其内的糖代谢较为活跃,半暗带区域的神经损伤较为缓慢。因此,拯救缺血半暗带是目前缺血性脑卒中治疗的一个大方     

CT灌注和CT血管成像在缺血性卒中早期诊断中的作用

目的探讨CT灌注和CT血管成像对缺血性卒中患者早期诊断缺血半暗带和缺血部位的作用。方法回顾20例缺血性卒中患者,于发病24h之内均行CT灌注检查,8例行CT血管成像,获取梗死侧与正常侧脑血流量(CBF)、脑血容量(CBV)和平均通过时间(MTT)参数图和脑血管影像,将上述结果进行统计学分析。结果本组急性脑梗死16例,4例TIA患者,经CT灌注检查梗死侧缺血中心区的CBV、CBF为(2.1±0.6)ml/100g、(22.8±26.2)ml.100g-1.min-1,较正常侧明显减少,MTT为(7.6±3.2)s,与正常对照区相比差异有显著性(P<0.01)。15例可见缺血半暗带存在,CT血管成像8例,与CT灌注判断的梗塞血管基本相符。结论CT灌注成像能快速、准确反映缺血半暗带的部位、范围,结合CT血管成像,可以准确判断栓塞血管部位,对早期诊断缺血性卒中和抓住动脉溶栓时机有较好的指导作用。     

急性脑梗死患者影像学缺血半暗带的临床评价策略

缺血性卒中再灌注治疗近年来取得了重大进展,治疗前快速精准评估缺血半暗带是临床诊治的紧迫需求.目前,影像学是显示缺血半暗带最直观、有效的方法,该方法通过利用组织窗筛选出能够从再灌注治疗中获益的患者,并预估风险和预后.作者介绍了急性脑梗死影像学缺血半暗带的临床评估模式,并对不同发病时间、拟进行再灌注治疗患者的缺血半暗带评价...     

脑储备能力评价参数概述及对比

脑储备能力的减退是预示缺血性卒中发生的危险因素已得到证实，具有重要的临床意义。其评价参数多样，如脑血流量、脑血容量、平均通过时间、脑循环时间、临界关闭压、血管舒缩反应性、反应时间、氧摄取指数、脑氧代谢率等，但迄今尚没有统一的评价标准。本文就脑储备能力不同阶段的各评价参数及其临床意义作一综述。     

Diffusion and Perfusion MRI in Acute Cerebral Ischemia

Ｃｅｒｅｂｒａｌｉｓｃｈｅｍｉａｉｓａｌｅａｄｉｎｇｃａｕｓｅｏｆｄｅａｔｈａｎｄｌｏｎｇ ｔｅｒｍｄｉｓａｂｉｌｉｔｙ .Ｔｈｅｄｉｒｅｃｔａｎｄｉｎｄｉｒｅｃｔｃｏｓｔｓｔｏｓｏｃｉｅｔｙａｒｅｅｘｐｅｃｔｅｄｔｏｒｉｓｅｉｎａｎａｇｅｉｎｇｐｏｐｕｌａｔｉｏｎ .Ｈｏｗｅｖｅｒ ,ｒｅｃｅｎｔａｄｖａｎｃｅｓｉｎｓｔｒｏｋｅｃａｒｅ ,ｓｕｃｈａｓｄｅｓｉｇｎａｔｅｄｓｔｒｏｋｅｔｅａｍｓａｎｄｔｈｒｏｍｂｏｌｙｓｉｓ ,ｈａｖｅｓｈｏｗｎｓｉｇｎｉｆｉｃａｎｔｉｍｐｒｏｖｅｍｅｎｔｓｉｎｔｈｅｃｌ…     

Hypoperfusion and its augmentation in patients with brain ischemia

Opinion statement Control of hypertension is a well-established goal of the primary and secondary prevention of stroke. However, management of blood pressure in the setting of acute brain ischemia is complicated by the possible effect of blood pressure changes on cerebral perfusion. In acute stroke, patients may have an ischemic penumbra of brain tissue, which has impaired perfusion but which is not irreversibly damaged. The ischemic penumbra may be salvaged with reperfusion. Lowering of blood pressure in this setting, however, would hasten the progression of the penumbra to infarction. With the exception of patients treated with thrombolytic agents, blood pressure reduction is not recommended in acute ischemic stroke for this reason. Preliminary studies suggest that there may be a role for interventions to elevate blood pressure as a treatment for acute stroke patients. Despite interest in induced hypertension as a treatment of stroke dating back to the 1950s, this practice has not achieved widespread use owing to concerns about potential adverse effects such as intracerebral hemorrhage, cerebral edema, and myocardial ischemia. It is commonly used, however, to treat patients with threatened cerebral ischemia due to vasospasm after subarachnoid hemorrhage. Until future studies clarify the effectiveness of induced hypertension in stroke treatment, maintaining adequate blood pressure and fluid volume is recommended for patients with acute ischemic stroke, particularly if the neurologic deficits are fluctuating or the patient has persistent large-vessel occlusive disease.     

大鼠的局灶性脑缺血再灌注损伤分区及再灌注时间窗

目的　研究脑缺血早期神经元损伤、半暗带及再灌注时间窗。方法　采用线栓法制做大鼠大脑中动脉梗阻 /再灌注模型。动物分为 :正常对照组 ;假手术组 ;缺血 (不再灌注 ) 30min组 ;缺血 (不再灌注 ) 1 ,2 ,4,6 ,2 4h ;缺血 1 ,2 ,3h后再灌注 2 4h组。每组 6只。恒温冰冻切片 ,行微管相关蛋白 (MAP2 )免疫组化染色 ;嗜银Ⅲ染色法复染 ;甲苯胺蓝染色。结果　MAP2免疫染色可显示神经元形态和皮质结构 ,显示缺血 30min的神经元病变。病变可分为 :中心区———MAP2阳性消失区 ;半暗带———MAP2阳性减弱伴选择性表达增强 ;继发损伤反应区———MAP2表达增强。缺血 6h内半暗带被迅速扩大的中心区取代 ,同时半暗带的神经元病变进行性加重。再灌注的时间窗应在缺血 3h以内。嗜银神经元集中分布于中心区边缘 ,半暗带也有散在分布 ,MAP2表达增强的神经元不易被银染。结论　MAP2表达增加可能是神经元对抗缺血的保护性反应 ;MAP2免疫染色是显示半暗带的理想的组织学方法     

ISCHAEMIC PENUMBRA: HIGHLIGHTS

The ischaemic penumbra was described for the first time in the late 1970s as a ring of hypoperfused zone surrounding the region of complete infarction. The penumbral zone is a functionally silent tissue which is able to regain its function if promptly reperfused. This implies that the ischaemic penumbra is not a static but a “dynamic” and “time-dependent” concept. In this paper we describe the role of neuroimmaging tecniques such as single photon emission tomography (SPET), positron emission tomography (PET), and diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI and PWI) in the study of ischaemic penumbra. These functional imaging techniques have the advantage of giving “in vivo” quantitative estimate of cerebral blood flow (CBF) as well as information on how the ischaemic tissue metabolic changes develop. It follows that, as therapeutic options for treating acute stroke evolve, neuroimaging strategies are assuming an increasingly important role in the initial evaluation and management of the acute ischaemic patient. In this regard, a wide range of therapeutic approaches have been investigated for either ameliorating the perfusion, or interfering with the pathobiochemical cascade leading to ischaemic neuronal damage, or improving endogenous neuroprotection pathways

The “time windows” required for these treatments to be effective varies being rather short for reperfusion and longer for neuroprotection. Salvaging more penumbra would enhance recovery and thereby allow the most appropriate candidate for therapeutic trials to be selected.     

Ischaemic penumbra: highlights

The ischaemic penumbra was described for the first time in the late 1970s as a ring of hypoperfused zone surrounding the region of complete infarction. The penumbral zone is a functionally silent tissue which is able to regain its function if promptly reperfused. This implies that the ischaemic penumbra is not a static but a "dynamic" and "time-dependent" concept. In this paper we describe the role of neuroimmaging tecniques such as single photon emission tomography (SPET), positron emission tomography (PET), and diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI and PWI) in the study of ischaemic penumbra. These functional imaging techniques have the advantage of giving "in vivo" quantitative estimate of cerebral blood flow (CBF) as well as information on how the ischaemic tissue metabolic changes develop. It follows that, as therapeutic options for treating acute stroke evolve, neuroimaging strategies are assuming an increasingly important role in the initial evaluation and management of the acute ischaemic patient. In this regard, a wide range of therapeutic approaches have been investigated for either ameliorating the perfusion, or interfering with the pathobiochemical cascade leading to ischaemic neuronal damage, or improving endogenous neuroprotection pathways. The "time windows" required for these treatments to be effective varies being rather short for reperfusion and longer for neuroprotection. Salvaging more penumbra would enhance recovery and thereby allow the most appropriate candidate for therapeutic trials to be selected.     

Glucose metabolism and acidosis in the metabolic penumbra of rat brain

The characterization of tissue acid-base status related to the penumbral zone of increased glucose consumption surrounding a focal cerebral ischemic lesion may suggest therapeutic techniques to maximize tissue survivability from stoke. We measured local cerebral metabolic rate for glucose (l CMRglc) and an index of brain tissue pH (pH_t) concurrently and characterized their interaction in a model of focal cerebral ischemia in rats in a double-label autoradiographic study, using [¹⁴C]2-deoxyglucose and [¹⁴C]dimethyloxazolidinedione. Computer-assisted digitization and analysis permitted the simultaneous quantification of the two variables on a pixel-by-pixel basis in the same brain slices. Hemispheres ipsilateral to intravascular tamponade-induced middle cerebral artery occlusion showed areas of normal, depressed, and elevated glucose metabolic rate (as defined by an interhemispheric asymmetry index) after 2 hr of ischemia. Regions of increased l CMRglc showed moderate acidosis (6.87±0.05), while regions of normal glucose metabolic rate showed normal pH_t (pH±SD=6.98 ± 0.05) and regions of decreased l CMRglc showed severe acidosis (6.69±0.11). A repeated-measures analysis of variance found these values to differ from each other at theP < 0.0005 significance level. The finding of moderate acidosis coupled with increased l CRMglc in the metabolic penumbra suggests that the excess protons may result from the anaerobic dissociation of ATP synthesis and hydrolysis.