| Part 1 Relationship between the vessel wall characteristics of arteriosclerotic middle cerebral artery stenosis and actue ischemic stroke riskObjective : Middle cerebral artery(MCA) severe atherosclerotic stenosis or occlusion does not necessarily occur ischemic stroke. however, MCA mild stenosis occurs ischemic stroke, So really need breakthrough simply focus on clinical luminal stenosis degree(plaque size) limitations, it’s necessary to evaluate the vessel wall characteristics of MCA stenosis segment(plaques itself). To investiagte the relationship between the vessel wall characteristics of arteriosclerotic MCA stenosis and actue ischemic stroke risk with 3.0T high resolution magnetic resonance imaging(HR MRI).Methods:Two hundred and eleven patients with moderat to severe atheroscl-erotic stenosis at M1 segment of MCA on magnetic resonance angiography(MRA)(50% ~ 99%) were enrolled. All patients were divided symptomatic and asympt-omatic group according to DWI findings. HR MRI wall imaging was performed on the target segment by using a 3.0T MR scanner. The vessel area(VA), luminal area(LA) and plaque signal intensity at the maximal lumen narrowing(MLN) sites, VA and LA at reference sites were measured. Plaque area(PA),plaque burden(PB) and remodeling index(RI) were calculated. RI was the ratio of VA at MLN site to reference VA. RI ≤ 0.95 was defined as negative remodeling(NR), RI ≥ 1.05 as positive remodeling(PR) and 0.95 > RI < 1.05 as intermediate remodeling(IR).No-PR including NR and IR. Intraplaque hemorrhage(IPH) was defined as an area with an intensity >150% of the signal of adjacent muscles(extraocular muscle or temporal muscle). The RI,PA,PB and IPH parameters derived from stenotic M1 segment of MCA between symptomatic and asymptomatic group. The relationship between the vessel wall characteristics of arteriosclerotic MCA stenosis and actue ischemic events was analyzed.The Mann-Whitney U test was used for quantitative variables, and the chi-squared or Fisher’s exact test was used for categoricalvariables.Results:A total of 216 atherosclerotic plaque of MCA stenosis(90 symptomatic and 126 asymptomatic) in 211 patients were analyzed. IPH was revealed on HR MRI in 27 vessels(12.5%, 22 symptomatic and 5 asymptomatic). The occurrence rate of IPH between symptomatic and asymptomatic MCA was significantly different(24.44% vs 3.97%, χ2 =20.125,p<0.001). PA and PB of the symptomatic group were signifiantly higher than those of asymptomatic group(5.47±1.37 vs 4.12±1.27,p=0.000;0.41±0.08 vs 0.35±0.08, p=0.000). Symptomatic MCA stenosis(68 PR vs22 no-PR). Asymptomatic MCA stenosis(38 PR vs 88 no-PR), significantly different between the two groups(χ2 =43.293,p<0.001).Conclusions:It was observed that IPH, greater PA and PB, positive remodeling within MCA on HR MRI were associated with actue ipsilateral ischemic stroke. HR MRI has emerged as a non-invasive vivo imaging tool in the reserch. These characteristics were promising factors for stratifying ischemic stroke risk.Part 2 Relationship between the Distribution of Plaque in Symptomatic Middle Cerebral Artery Stenosis and Ischemic Stroke Mechanism SubtypeObjective:The atherosclerotic plaque of middle cerebral artery(MCA) is the most common cause of ischemic stroke. The vascular wall imaging characteristics is associated with ischemic stroke, however little is known about the location of MCA plaques and how they relate to clinical status. We aimed to explore the relationship between the distribution of plaque in symptomatic MCA stenosis and ischemic stroke mechanism subtype.Methods:One hundred and thirty-six acute ischemic stroke patients on diffusion weighted imaging(DWI) with atherosclerotic MCA(M1 segment) stenosis werecollected. High resolution magnetic resonance imaging(HR MRI) was performed on the target segment by using a 3.0T MR scanner, and 3D-pulsed continuous arterial spin labeling(3D-p CASL) examination on whole brain was conducted on them. The distribution of plaque and DWI high signal intensity were observed,cerebral blood flow(CBF) in MCA supply area was assessed. to compare whether there were differences in cerebral infarction mechanism caused by the distribution of different plaques. The chi-squared or Fisher’s exact test was used for categorical variables. Comparison the CBF value between the affected side and mirror side was performed using paired t-test.Results:HR MRI could clearly show the structure of the MCA vascular wall.Among 136 enrolled patients(136 atherosclerotic plaques of MCA), 36(26.47%)patients were with ventral plaques, 14(10.29%) were with inferior wall plaques, 28(20.59%)were with ventral and inferior wall plaques, 11(8.08%)were with dorsal plaques, 10(7.35%)were with superior wall plaques, 9(6.62%)were with dorsal and superior plaques, 17(12.5%) were with annular plaques, 4(2.94%) were with ventral and superior wall plaques,and 7(5.15%)were with dorsal and inferior wall plaques.Thirty-nine(50%) had hypoperfusion/impaired emboli clearance and 30(38.46%)patients had artery-to-artery embolismin the ventral, inferior, ventral and inferior wall plaques, 21(70%)had perforating branch lesion in the superior, dorsal, dorsal and superior wall plaques, 13(76.47%) had multiple mechanisms lesion in annular plaques. Differences were statistically significant(p<0.001). The CBF value([30.92±8.75]ml/min/100 g in affected side MCA supply area were significantly lower than that in [54.17±10.41]ml/min/100 g the mirror side, t =14.519, p <0.001).Conclusions:The distribution of plaque in symptomatic MCA stenosis is related to ischemic stroke mechanism subtype. The atherosclerotic plaques of patients with symptomatic middle cerebral artery stenosis more frequently occur in the ventral,inferior, ventral and inferior part of the artery, facing toward penetrating branch artery ostia. Which are easy to cause hypoperfusion/impaired emboli clearance and artery-to-artery embolismin ischemic stroke. Dorsal, superior, dorsal and superior wall plaques are easy to block the openings of the penetrating artery, thus causing ischemic events. The annular plaques are easy to cause multiple mechanismsischemic stroke. Combining HR MRI with 3D-p CASL technique may assist to reveal ischemic stroke mechanism subtype.Part 3 Identifying Clinical and Multi-modality Magnetic Resonance Imaging Based Evaluation of Ischemic StrokeRisk in Atherosclerotic Middle Cerebral Artery StenosisObjective:The Essen Stroke Risk Score(ESRS) and ABCD series rating scales have been widely used in clinical practice are designed to predict the risk in non-cardiogenic actue ischemic stroke patients, while the ischemic events still occur in these patients assessed as low risk. predictive instruments based on clinical features for ischemic stroke risk limited specificity. To improve the accuracy of predictions for acute ischemic stroke risk, We sought to identifying clinical and multi-modality magnetic resonance imaging(MRI) based pediction of ischemic stroke risk in atherosclerotic middle cerebral artery(MCA) stenosis.Methods:Multi-modality MRI technique was used to examine 197 patients with atherosclerotic MCA stenosis. Multi-modality MRI technique including conventional MRI,magnetic resonance angiography(MRA), diffusion weighted imagine(DWI),high resolution magnetic resonance imaging(HR MRI) and 3D-pulsed continuous arterial spin labeling(3D-p CASL). All patients were divided cerebral infarction and no cerebral infarction group according to DWI findings. Baseline clinical and radiologic data variables, including Essen Stroke Risk Score(ESRS),high-sensitivity c-reactiveprotein(hs-CRP), homocysteine(Hcy), vascular stenosis, apparent diffusion coefficient(ADC)/r ADC value, vulnerable plaque, cerebral blood flow(CBF)/r CBF value that considered possibly related to acute ischemic stroke risk were selected in197 patients with atherosclerotic MCA stenosis. A univariate analysis was conducted to explore the association between these factors and schemic stroke risk. Logisticregression was then performed to select the most important variables independently affecting prognosis. Receiver operator characteristic curve(ROC) was then used to obtain cut-off points for each independent variable. A risk score(clinical and multi-modality MRI score) was then developed based on these variables. The area under the ROC was performed for risk of effectiveness evaluation with respect to acute ischemic stroke.Results : In the univariate analysis, variables associated with ischemic stroke were: ESRS, hs-CRP, hcy, the degree of MCA stenosis, ADC/r ADC, vulnerable plaque and CBF/r CBF. Five variables independently associated with ischemic stroke were identified by Logistic regression: ESRS, hs-CRP and(or) Hcy, the degree of MCA stenosis, vulnerable plaque and CBF. We then developed the clinical and multi-modality MRI score: ESRS≥4 score, the degree of MCA stenosis>60%,vulnerable plaque was postive, CBF≤ 30ml/(min.100 g) and hs-CRP>9mg/l or(and)Hcy>15umol/l. The factor that most accurately predicted ischemic stroke risk was clinical and multi-modality MRI score(area under the curve=0.937,p<0.001), The sensitivity, specificity were 89.1%,83.8%, respectively. followed by Hcy(area under the curve=0.880,p<0.001), predicted hs-CRP(area under the curve=0.850,p<0.001), predicted ESRS(area under the curve=0.793,p<0.001), predicted CBF value(area under the curve=0.720,p<0.001) and the degree of MCA stenosis(area under the curve=0.627,p =0.002).Conclusions : Clinical and multi-modality MRI score based on clinical and radiologic data is superior to single ESRS and radiologic parameters in estimating the chances of ischemic stroke risk. Combining vascular imaging findings, clinical features with serum biochemical test causes a dramatic boost in the accuracy of predictions with clinical features alone for ischemic stroke risk. If validated in relevant clinical settings, risk stratification by the clinical and multi-modality MRI model may assist in early implementation of therapeutic measures and effective use of hospital resources. |
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