超急性脑梗死的CT和MRI诊断宁波市第一医院影像科阮 新 忠前言Ø 脑缺血（cerebral ischaemia）是临 床一种致死率和致残率很高的常见脑 血管病，因血管闭塞致供应区缺血超 过一定时限后，即发生脑梗死（ cerebral infarction） Ø 发病6小时之内的脑梗死属超急性脑 梗死，以往的脑梗死分期并无超急性 期这一概念，在一些溶栓治疗研究成 功，并且认为起病3-6小时之内使用效 果最好和不良作用最小之后，才出现 这一新的分期Ø 近年来，随着缺血半暗带(ischemic penumbra，IP)概念的提出，以及许 多治疗脑梗死取得明显疗效的研究结 果出现，为超急性脑梗死的治疗带来 了新的活力与启示 Ø 其中经动脉介入溶栓治疗已逐步深 入，取得了很大进展，从而为脑梗死 的紧急处理提供了一种新的选择 检查方法：Ø1、CT：平扫、CTPI和CTA Ø2、MRI：平扫、DWI、PWI、 MRA、CE-MRA、MRS Ø3、SPECT/PET Ø4、DSA5一、CT检查 1、CT平扫：1.1直接征象豆状核轮廓模糊岛带低密度征及基底节回避灰白质分界不清、皮层低密度 以及脑组织肿胀致局部脑沟、 脑裂变窄1.2间接征象 1.2.1 大脑中动脉高密度征(HMCA sign) 女，54岁，左 侧肢体无力； 第一幅图片显 示“致密动脉征” 。
11天后复查1.2.2 大脑中动脉点征（MCA dot sign) 女性，65岁A：首次CT平扫显示左侧裂池 “大脑中动脉点征”（黑箭），同时显示 岛叶梗死；B：增强CT三维重建显示MCA M2段闭塞（白箭） a:大脑中动脉点征； b：T2WI； c:DWI女性，54岁A：首次CT平扫显示右侧裂池“大脑中动 脉点征”（白箭），同时显示岛叶后部皮层密度减低 ；B：DSA证实MCA M3段阻塞（黑箭）；C：动脉内溶 栓24h后，“大脑中动脉点征”消失 1.2.3 大脑后动脉高密度征(HPCA sign ) 女性，67岁，突然发生偏瘫和偏盲CT平扫显示环池内的左侧大 脑后动脉密度增高（图A、B 箭）；1天后CT复查（图C），可见丘 脑梗死灶 2、CTA正常CTACTA左侧大脑中动脉闭塞右侧大脑中动脉闭塞3、CT灌注成像 颈内动脉闭塞CTA and CT Perfusion CT平扫：左侧MCA供血区白质略低密度 CTPI：左侧颈内动脉供血区灌注缺损 CTA：左侧颈内动脉起始部严重狭窄大脑后动脉、前动脉、中动脉供血区梗死二、MRI检查1、MRI平扫 2、弥散加权成像（DWI）右偏瘫3小时3、灌注加权成像（PWI）õ 81-year-old woman scanned 2 and 19 hours post ictus. õ A, Diffusion-weighted imaging at 2 hours shows subtle restricted diffusion in the left deep cerebral structures, not appreciated prospectively. õ B and C, Perfusion- weighted imaging bolus- tracking curves (B) for selected regions (C) show approximately 6-second delayed transit to the distal left middle cerebral artery vessels (solid line).õ D, MR angiography demonstrates decreased flow-related enhancement in the left middle cerebral artery territory. õ E, Diffusion-weighted imaging at 19 hours reveals acute infarct in left basal ganglia and insular cortex. õ F, T2*-weighted imaging demonstrates a new 1-cm focus of profound hypointensity in the left putamen, consistent with focal hemorrhage or localized desaturation of hemoglobin.õ A, Patient with severe right hemiparesis and aphasia (NIHSS score 14). MRI 1.5 hours after symptom onset reveals a large PWI/DWI mismatch with a small diffusion lesion in the left basal ganglia (DWI, ADC) and a large area of hypoperfusion (TTP). MRA shows left M1 occlusion. Patient was treated by intravenous thrombolysis. FLAIR at day 1 shows only a small striatocapsular infarction. õ B, Patient with right hemiplegia, complete aphasia, and somnolence (NIHSS score 21). MRI 2 hours after symptom onset reveals a large diffusion lesion (DWI, ADC), a perfusion lesion covering the entire MCA territory (TTP), and no relevant PWI/DWI mismatch. MRA shows left carotid-T occlusion. DWI 5 hours after initial MRI reveals further lesion growth. Patient developed malignant MCA infarction and was treated with hemicraniectomy 24 hours after stroke onset. T2-WI indicates T2-weighted imaging.NIHSS : the National Institutes Of Health Stroke Scale4、MRA和CE-MRA a:TOF MRA 左侧MCA近端闭塞； b:TOF MRA基底动脉闭塞; c:CE-MRA 右侧ICA闭塞5、磁共振波谱分析(MRS)6、大脑中动脉磁敏感征（MCA Susceptibility Sign）A：轴位T2*MRI显示左侧“大脑中动脉 磁敏感征”（宽箭），管径超过对侧 未受累MCA（窄箭）；B：DSA显示左侧 MCA主干闭塞 三、缺血半暗带(ischemic penumbra，IP)1、概念和意义õ Reversible lesion after intra- arterial thrombolysis. õ MRI performed acutely shows (upper row) the presence of a hyperintensity on DWI (left image) corresponding to a decrease in ADC and changes in the time to peak values. õ After successful intra-arterial thrombolysis (lower row) the DWI changes tend to diminish whereas the perfusion deficit is absent.2、评价方法 2．1 CT灌注成像（CTPI）2．2 DWI和PWIThe mismatch conceptPatient with signs of acute cerebral ischaemia. The CT shows a dense middle cerebral artery. MR imaging was performed which shows no signs of major infarction on T2-weighted MRI. The perfusion image shows a large area of hypoperfusion in the middle cerebral artery territory. The diffusion images show an area of smaller diffusion defects.A 73-year-old woman with left hemiparesis. The first MRI was performed 6 hours after the onset of symptoms. In this first imaging, the bright area in the trace image (A) representing the infarct is clearly smaller than the hypoperfusion area on the rCBF map (B). Infarct growth is demonstrated on the diffusion weighted trace images 27 hours (C) and 1 week (D) after the onset of symptoms.Perfusion>DiffusionProgressive cortical infarction. A 62- year-old man had sudden onset of dense right hemiplegia 7 hours before his MRI study. The T2 sequence shows only a subtle increase in signal in a gyral pattern, whereas the DWI map shows an ischemic injury (arrow) mostly located in the insular and peri- insular cortex. The CBV map demonstrates a perfusion abnormality (arrow) much larger than the DWI abnormality. MRA demonstrates a left MCA stem occlusion (arrow). In the follow-up MRI the stroke has expanded beyond the initial area of perfusion abnormality (arrow).Perfusion>Diffusionõ 49-year old male with left-sided weakness. õ The diffusion image shows an area of hyperintensity in the MCA terri。