Abstract:

Objective To explore the mechanism of stroke in different middle cerebral artery (MCA) stenosis rate, by understanding the association of MCA stenosis rate, MCA plaque morphology and infarct pattern in stroke patients. Methods Patients with ischemic stroke in MCA territory within 2 weeks in Peking Union Medical College Hospital from 2009 to 2014 were consecutively collected. Patients with MCA plaque on high-resolution magnetic resonance imaging (HRMRI) were included, and patients with cardioembolic, extracranial large artery atherosclerotic stroke and other causes of stroke were excluded from the study. The infarct lesions were classified into penetrating artery, cortical, watershed (or border zone) and mixed infarction, and then the infarct volume on diffusion weighted image (DWI) was calculated. On sagittal HRMRI, the stenosis rate of MCA M1 segment, plaque distribution, length, thickness, signal and surface discontinuity were assessed. Patients with stenosis rate >50%were severe stenosis group, and patients with stenosis rate ≤50% were mild stenosis group. Results One hundred and two patients were analyzed, of whom, 39 patients were in severe stenosis group and 63 in mild stenosis group. Severe stenosis group had 14 cases of penetrating artery infarction (35.9%), 9 cortical infarction (23.1%), 4 watershed infarction (10.3%) and 12 mixed infarction (30.8%); mild stenosis group had 44 penetrating artery infarction (69.8%), 8 cortical infarction (12.7%), 3 watershed infarction (5.8%) and 8 mixed infarction (12.7%). The proportion of two groups had significant difference (P =0.014). The severe stenosis group had longer (P <0.001) and thicker (P <0.001) plaques, and more mixed-signal plaques (P <0.001). The plaque thickness (P <0.001, OR 87.792, 95%CI 13.120-587.453) and mixed-signal of plaque (P =0.007, OR 7.358, 95%CI 1.725-31.382) were independent predicting factors of MCA stenosis >50%. In severe stenosis group, the infarct volume was related to plaque surface discontinuity (P =0.004).In mild stenosis group, the infarct pattern was related to plaque surface discontinuity (P =0.002) and plaque thickness (P =0.002). The plaque discontinuity was the independent predicting factor of embolic infarction (P =0.003, OR 5.778, 95%CI 1.788-18.672) in mild stenosis group. Conclusion Patients with MCA stenosis >50% or ≤50% have different proportion of infarct pattern and plaque morphological markers. The surface discontinuity of plaques with stenosis ≤50% is the independent risk factor of embolic infarction, indicating the potential stroke mechanism of mild stenotic MCA.

Key words: Atherosclerotic plaque; High resolution magnetic resonance imaging; Stroke mechanism; Middle cerebral artery; Intracranial arterial stenosis

摘要：

目的 本研究旨在探索大脑中脉（middle cerebral artery，MCA）狭窄率与MCA斑块形态学及梗死类型 的相关性，并探索不同狭窄率患者卒中的发生机制。 方法 连续收集2009-2014年于北京协和医院就诊的2周内发生MCA供血区缺血性卒中并进行高 分辨磁共振（hi gh-resolution magnetic resonance imaging，HRMRI）扫描的患者。纳入MCA M1段存在斑 块的患者，排除心源性、颅外大动脉粥样硬化及其他病因的卒中患者。在弥散加权成像（diffusion weighted imaging，DWI）上将梗死类型分为穿支、皮层、分水岭和混合型梗死，并测量梗死体积。在矢 状位HRMRI上测量MCA M1段狭窄率，并收集斑块位置、长度、厚度、信号和斑块连续性等形态学指标。 将狭窄率>50%的患者分入重度狭窄组，将狭窄率≤50%的患者归入轻度狭窄组。 结果 研究共纳入102例患者，其中重度狭窄组39例，轻度狭窄组63例。重度狭窄组患者卒中，穿支梗 死14例（35.9%），皮层梗死9例（23.1%），分水岭梗死4例（10.3%），混合型梗死12例（30.8%）；轻 度狭窄组患者中，穿支梗死44例（69.8%），皮层梗死8例（12.7%），分水岭梗死3例（5.8%），混合 型梗死8例（12.7%），两组构成类型比较，差异有显著性（P =0.014）。与轻度狭窄组比较，重度狭窄 组患者斑块更长（P <0.001）、更厚（P <0.001）、更多混合信号斑块（P <0.001）。斑块厚度（P <0.001， OR 87.792，95%CI 13.120～587.453）和斑块混合信号（P =0.007，OR 7.358，95%CI 1.725～31.382）是 MCA狭窄率>50%的独立预测因子。重度狭窄组中，梗死体积与斑块表面不连续（P =0.004）相关。轻 度狭窄组中，梗死类型与斑块表面不连续（P =0.002）及斑块厚度（P =0.032）相关。且斑块表面不连 续是发生栓塞性梗死的独立预测因子（P =0.003，OR 5.778，95%CI 1.788～18.672）。 结论 MCA狭窄率>50%和≤50%的患者具有不同的卒中分型比例和斑块形态学；狭窄率≤50%的斑 块表面不连续是栓塞性梗死独立预测因子，提示轻度狭窄MCA斑块破裂可能是引起栓塞性病灶的 机制。

关键词: 粥样硬化斑块; 高分辨磁共振; 脑卒中机制; 大脑中动脉; 颅内动脉狭窄