Clinical Application Of Asymmetrical Vein Sign On SWI In Ischemic Cerebrovascular Disease

Part 1 Comparison of SWI and PWI in patients with severe stenosis or occlusion of unilateral internal carotid artery/middle cerebral arteryBackground:The ischemic cerebrovascular disease is a common disease with high fatality and morbidity.Conventional magnetic resonance imaging(MRI),diffusion weighted imaging(DWI)and magnetic resonance angiography(MRA)can provide important information for diagnosis and prognosis of ischemic cerebrovascular disease,but can not reflect the perfusion of brain tissue.Perfusion weighted imaging(PWI)can be used to examine the hemodynamic effects of artery stenosis or occlusion,but requires the use of contrast agents.Susceptibility weighted imaging(SWI)is a new high-resolution MRI technology that has been used to detect the ischemic penumbra and benign oligemia in stroke patients in recent years.SWI does not require the application of contrast agents but uses paramagnetic susceptibility effects to study metabolic changes in hypoperfused brain tissues,SWI can reflect the proporticon of deoxygenated hemoglobin and oxygenated hemoglobin,and indirectly reflect the oxygen extraction fraction(OEF)of brain tissues.The previous studies had shown that the asymmetrical vein sign(AVS)on SWI can reflect the degree of brain perfusion in patients with ischemic cerebrovascular disease.Objective:The aim of our study was to investigate whether the AVS on SWI can give information similar to PWI in patients with severe stenosis or occlusion of unilateral internal carotid artery(ICA)or middle cerebral artery(MCA)at variable degrees of ischemia.Methods:The patients with severe stenosis or occlusion of unilateral ICA or MCA Ml segment were analyzed.All patients underwent MRI examination,including T2WI,DWI,SWI,PWI and MRA.The degree of artery stenosis was estimated according to the North American Symptomatic Carotid the Endarterectomy Trial(NASCET).According to the clinical data and imaging findings,the patients were divided into three groups:acute cerebral infarction group,chronic cerebral infarction group and transient ischemic attack(TIA)group.The AVS on SWI,prolonged time topeak(TTP),prolonged mean transit time(MTT)and decreased cerebral blood flow(CBF)on PWI of MCA territory were performed by Alberta Stroke Program Early Computed Tomography Score(ASPECTS)in all patients.The diffusion restriction on DWI in the patients with acute cerebral infarction was also evaluated.The SWI-ASPECTS and TTP-ASPECTS,MTT-ASPECTS,CBF-ASPECTS were compared respectively in each group.The SWI-ASPECTS and DWI-ASPECTS were compared in the patients with acute cerebral infarction.Spearman's rank correlation test was also used to examine the correlation between the DWI-SWI mismatch and DWI-TTP mismatch,DWI-MTT mismatch,DWI-CBF mismatch respectively in patients with acute cerebral infarction.Results:68 patients wer divided into 3 groups:acute cerebral infarction group(n =24),chronic cerebral infarction group(n = 23)and TIA group(n = 21).The age,sex,location and degree of ICA or MCA were not significantly different among the three groups(statistical value = 1.494,0.929,2.382 and 1.977,P = 0.232,0.629,0.702 and 0.381,respectively).There were no significant differences between the SWI-ASPECTS and TTP-ASPECTS,MTT-ASPECTS in patients with acute cerebral infarction(Z =-0.961 and-0.736,P = 0.336 and 0.462).The SWI-ASPECTS was significantly lower than the CBF-ASPECTS and DWI-ASPECTS(Z =-2.294 and-5.214,P = 0.022 and 0.002).The SWI-ASPECTS was significantly higher than the TTP-ASPECTS,MTT-ASPECTS and CBF-ASPECTS in patients with chronic cerebral infarction(Z =-5.057,-4.988 and-2.158,P = 0.000,0.000 and 0.031,respectively).The SWI-ASPECTS was significantly higher than the TTP-ASPECTS and MTT-ASPECTS in TIA patients(Z =-5.124 and-5.214,P = 0.000 and 0.000).There was no significantly difference between the SWI-ASPECTS and CBF-ASPECTS(Z ?-1.526,P = 0.127).In patients with acute cerebral infarction group,the DWI-SWI mismatch was correlated with DWI-TTP mismatch and DWI-MTT mismatch(r = 0.569 and 0.433,P = 0.004 and 0.035),whereas there was no significantly difference about the correlation between DWI-SWI mismatch and DWI-CBF mismatch(r = 0.323,P = 0.124).Conclusion:The AVS on SWI can reflect the brain tissue perfusion of patients with severe stenosis or occlusion of ICA or MCA at variable degrees of ischemia.The corresponding relations between the AVS on SWI and PWI were different in acute cerebral infarction,chronic cerebral infarction and TIA patients.The DWI-SWI mismatch can be used as the assessment of ischemic penumbra and benign oligemia in patients with acute cerebral infarction.Part 2 Related factors of asymmetrical vein sign in acute middle cerebral artery stroke and correlation with clinical outcomeBackground:Susceptibility weighted imaging(SWI)is a modern magnetic resonance imaging(MRI)technique that is a high-resolution 3D phase-enhanced gradient echo method sequence.Recently,SWI has been applied widely as a method available to evaluate intracerebral hemorrhage,hemorrhagic transformation,cerebral venous thrombosis,and assessment of brain tissue at risk for infarction.The previous studies have shown that the asymmetrical vein sign(AVS)on SWI can appear in acute ischemic stroke case.The presence of prominent dilated vessels along the course of the cortical veins on SWI has been called the "asymmetrical cortical vein sign(ACVS)",whereas the same status that occurred along the course of the subependymal and medullary veins in the deep white matter has been called the“asymmetrical medullary vein sign(AMVS)".However,the appearance of ACVS and AMVS seems to be pathophysiologically complex,and the clinical significance is still unclear.It has not been clearly established which clinical and radiological factors affect the appearance of ACVS and AMVS on SWI in acute cerebral ischemia.Furthermore,whether the presence of asymmetrical vein sign on SWI is associated with stroke severity and outcome in previous studies remains controversial.Objective:The aim of our study was to analyze the related factors of ACVS and AMVS on SWI in patients with acute middle cerebral artery(MCA)territoryinfarction and whether their presence were used as independent predictor for stroke severity and outcome.Methods:124 patients with acute MCA territory infarction within 3 days of stroke onset were included.The following clinical data were reviewed:patient age,sex,history of hypertension,hyperlipidemia,diabetes mellitus,or atrial fibrillation,platelet,international normalized ratio level(INR),the magnetic resonance(MR)time from stroke onset and National Institutes of Health Stroke Scale(NIHSS)score at admission.All patients underwent MRI examination,including diffusion weighted imaging(DWI),SWI and magnetic resonce angiography(MRA).The infarct extent was scored using the semiquantitative scoring system,the Alberta Stroke Program Early computed tomography Score(ASPECTS).The stenosis degree of MCA on MRA was rated by using the Thrombolysis in Myocardial Infarction grading scale(TIMI).According to the presence of ACVS and AMVS on SWI,the patients were divided into several different groups.In addition,clinical outcome at 3 months after stroke was assessed by using the modified Rankin Scale(mRS),which was dichotomized into good(mRS 0-1)and poor outcome(mRS 2-6).We investigated respectively the differences in magnetic resonance imaging findings and the clinical data among different groups.Binary logistic regression analysis was used to evaluate whether the AC VS or AM VS was used as an independent predictor for stroke severity and clinical outcome in patients with acute MCA territory infarction.Results:A total of 124 patients(84 men and 40 women;mean age,64 years)were included for the final analysis.All patients had no infarction on DWI in other territories except MCA territory.Most of patients(83 of 124)had a history of hypertension.Some patients had other risk factors for atherosclerosis,such as hyperlipidemia(47 of 124)and diabetes mellitus(55 of 124).The ACVS was demonstrated in 90(72.6%)of 124 patients.Of the 90 patients,47 were accompanied with the AMVS.The rest of 34 patients showed no ACVS and AMVS.None of patient only presented AMVS without ACVS was detected in the present study.All patients were divided into 3 groups according to the ACVS and AMVS:ACVS+,AMVS+ group;ACVS+,AMVS-group;and ACVS-,AMVS-group.The MR time from stroke onset,NIHSS score at admission,poor clinical outcome,DWI-ASPECTS and status of MCA steno-occlusion were sigrnificantly different among three groups(all P<0.001),By further comparison between each two groups,the patients in ACVS+,AMVS+ group had shorter MR time from stroke onset,higher NIHSS score at admission,more poor clinical outcome,lower DWI-ASPECTS and more severe MCA status than the other two groups(all P<0.01).The DWI-ASPECTS score was significantly lower and status of MCA steno-occlusion was more severe in ACVS+,AMVS-group than ACVS-,AMVS-group(all P<0.001).The MR time from stroke onset,admission NIHSS score and clinical outcome were not significantly different between ACVS+,AMVS-group and ACVS-,AMVS-group(P = 0.179,0.15 and 0.06,respectively).Moreover,77 of 124(62.1%)patients were classified as having good outcome and 47/124(37.9%))as having poor outcome.The median admission NIHSS score was significantly higher and the DWI-ASPECTS was significantly lower in the poor outcome group compared with the good outcome group(all P<0.001).The ACVS and AMVS were significantly more common in the poor outcome group(all P<0.001).In the multivariate binary logistic stepwise regression including the factors with significant difference between the poor and good outcome group,the admission NIHSS score(odds ratio[OR],1.54;95%confidence interval[Cl],1.04-2·46;P ?0.031)and AMVS(OR,2.37;95%Cl,1.23-8.73;P = 0.027)were associated with poor outcome.The ACVS(OR 2.35;95%Cl 0.83-4.55;P = 0.36)was not predictor of clinical outcome.Conclusion:The ACVS and AMVS were correlated to status of MCA steno-occlusion,whereas the AMVS was closely related to poor outcome in patients with acute MCA territory infarction rather than ACVS.Therefore,SWI should be added to the routine neuroimaging protocol for patients with acute MCA territory infarction.