High-Resolution Magnetic Resonance Imaging Of Atherosclerotic Middle Cerebral Artery Stenosis And Prediction Of The Infarction Pattern

Intracranial atherosclerosis of the middle cerebral artery (MCA) is a major cause of ischemic stroke in the chinese population. Important predictors of stroke include the degree of stenosis and the underlying plaque morphology. Recently, a few studies have confirmed not only the degree of stenosis but also the wall can be depicted by using high-resolution magnetic resonance imaging (HR MRI) for atherosclerotic patients of MCA. The purpose of this study is to evaluate the wall characteristics of atherosclerotic MCA stenosis and explore the possible stroke mechanisms of MCA by using HR MRI. And It aim to investigate the potential of HR MRI as a promising tool for assisting risk evaluation and therapy planning for atherosclerotic patients of MCA.Part I:High-Resolution Magnetic Resonance Imaging of the Vessel Wall in Patients with Symptomatic Atherosclerotic Stenosis of the Middle Cerebral ArteryObjective To analyze and compare vascular wall imaging characteristics between patients with symptomatic and asymptomatic atherosclerotic stenosis of the middle cerebral artery (MCA), by using high-resolution magnetic resonance imaging (HR MRI).Methods Sixty-four consecutive patients with moderate or severe atherosclerotic MCA stenosis underwent HR MRI with a 3.0-T scanner. The HR MRI protocol included four different scans:black blood T1-weighted, T2-weighted. proton density (PD)-weighted MRI, and 3D turbo spin echo (3D-SPACE) imaging technique and multiplanar reconstruction. The vessel wall area (VA), lumen area (LA), plaque area (PA) and remodeling index (RI) were calculated. Plaque characteristics, including location, morphology, and signal intensity, were analyzed on HR MRI. Differences between symptomatic and asymptomatic patients were statistically analyzed. Multivariate logistic regression analysis was performed to compare variables between symptomatic and asymptomatic patients.Results The imaging data of 57 patients (35 symptomatic,22 asymptomatic) were appropriate for analysis. PA, RI were significantly greater in the symptomatic group than in the asymptomatic group (PA:5.40±1.85mm2 vs 4.36±1.53mm2,P=0.046; RI:1.06±0.10 vs 1.00±0.09,P=0.021). Positive remodeling (PR), plaque location in the superior aspect of the vessel wall and irregular plaque surface were more frequently observed in the symptomatic group than in the asymptomatic group (P=0.038,P=0.034, P=0.032). Of the 57 study patients,19 showed intact arch-like or spot-like hyperintensities adjacent to the lumen on T2-weighted images. Of these 19 patients, six showed distinct layers in the signal intensity of the plaques. The difference in the rates of hyperintense plaque foci between symptomatic and asymptomatic patients was not significant. Moreover, multivariate logistic regression identified plaque location on the superior wall as an independent predictor of symptomatic MCA stenosis(OR=0.226; P=0.037).Conclusion Compared to asymptomatic patients, those with symptomatic atherosclerotic stenosis of MCA are more likely to have larger plaques, positive remodeling, superiorly located plaques, and irregular plaque surface. These characteristics are promising factors for stratifying stroke risk.Part II:Arterial Remodeling of Middle Cerebral Artery with Atherosclerotic Stenosis:A High-Resolution Magnetic Resonance Imaging StudyObjective To investigate remodeling mode of moderate or severe atherosclerotic stenosis of the middle cerebral artery (MCA) using high-resolution magnetic resonance imaging (HR MRI).Methods Sixty-four consecutive patients with atherosclerotic MCA stenosis were imaged with a 3.0-T magnetic resonance scanner. The HR MRI protocol included four different scans:T1-weighted, T2-weighted, proton density (PD)-weighted black blood imaging and 3D-SPACE. The vessel area (VA), lumen area (LA) and plaque area(PA) were calculated. The characterization of the plaque on HR MRI was analyzed. And the difference between positive remodeling(PR) and non-positive remodeling(non-PR) was explored.Results Fifty-seven patients imaging was appropriate for analyse. Positive remodeling was found in 28 lesions. Compared with the non-PR group, the PR group had greater VA(VAMLN:16.18±2.65mm2 vs 14.34±2.99mm2,P=0.003), wall area(WA) (WAMLN:10.79±2.27mm2 vs 9.00±1.77mm2,P=0.002) and greater PA (PA:6.11±1.77mm2 vs 3.93±1.00mm2,P=0). High intensity on diffusion-weighted magnetic resonance imaging (DWI) (71.4% vs 34.5%, P=0.005) and irregularity of plaque surface(53.6% vs 27.6%, P=0.046) were more frequently observed in PR than non-PR.Conclusion In patients with MCA atherosclerosis, PR lesions more likely to contain larger plaques and irregular plaque surface than non-PR lesions are probably with high risk for plaque rupture and subsequent stroke.Part III:Wall Characteristics of Atherosclerotic Middle Cerebral Artery Stenosis and Prediction of the Infarction PatternObjective To evaluate the characteristics of atherosclerotic middle cerebral artery (MCA) stenosis by high-resolution magnetic resonance imaging (HR MRI) and determine the relationship between wall characteristics and infarction patterns.Methods Thirty-six patients with acute ischemic stroke due to middle cerebral artery stenosis underwent diffusion-weighted magnetic resonance imaging (DWI) and HR MRI. Wall characteristics of MCA, including irregular surface, superior location, T2-hyperintense of plaques and positive remodeling(PR), were analyzed. Characteristics of acute infarct on DWI were categorized according to the number (single or multiple infarcts) and the pattern of cerebral infarcts (cortical, border zone, or perforating artery territory infarcts). The relationship between wall characteristics and infarction patterns was evaluated.Results Thirty patients imaging was appropriate for analyse. PR was observed in 20 patients, irregular surface plaque in 18 patients, superior location of plaques in 14 patients and T2-hyperintense foci in 13 patients. Seventeen patients had multiple acute cerebral infarcts and 13 showed single acute cerebral infarcts. Border zone infarcts were the most common (76.5%) among multiple acute infarcts. Penetrating artery infarcts(PAI) accounted for 76.9% of all single infarcts. Multiple infarcts were more frequently observed in patients with PR (P=0.007) or plaque surface irregularity (P=0.035). Single infarcts, especially PAI, were more prevalent in patients with superior plaque (P=0.030). No statistically significant differences were observed between multiple and single infarcts in patients with T2-hyperintense lesions (P= 0.638).Conclusion PR or irregular surface plaques were associated with artery-to-artery embolism. Superior location of plaques was associated with PAI. HR MRI provides insights into intracranial atherosclerosis in vivo, predictive of infarction patterns.