The Application Of Asymmetrically Hypointense Veins And Susceptibility Vessel Sign On Susceptibility-Weighted Imaging In Acute Ischemic Stroke

BackgroundsIschemic stroke is one of the most common diseases with high mortality and disability rates worldwide.The key to treating ischemic stroke is saving the ischemic penumbra.A number of factors,such as the location of blood vessels,the characteristics of thrombus and collateral circulation,can influence the death of ischemic neurons.Susceptibility weighted imaging(SWI)is a newly developed magnetic resonance(MR)protocol that is based on the blood oxygen level-dependent(BOLD)image principle.In acute ischemic stroke,severe reduction in cerebral perfusion pressure causes an increase in the ratio of deoxyhemoglobin to oxyhemoglobin by increasing the oxygen extraction fraction(OEF).As a result,SWI shows increased and stronger drainage veins in the hypoperfusion region than in normal brain areas,which are called “asymmetrically hypointense veins(AHVs)”,is a new technique that might reflect the ischemic penumbra,and also has the value in evaluating collateral status.Besides,the thrombus at the occlusion presented as hypoperfusion signals as the deoxyhemoglobin in it was relatively increased.This phenomenon was named as susceptibility vessel sign(SVS),and it showed highsensitivity and specificity to the thrombus site and size.Our research aimed to study the application of the AHVs and the SVS in acute ischemic stroke.Part one: The detective value of asymmetrically hypointense veins to perfusion-diffusion mismatch in acute ischemic stroke ObjectiveAHVs on SWI have been proposed to be a surrogate marker by which to predict penumbra.This study aimed to assess the value of AHVs in detecting penumbra in acute ischemic stroke.MethodsWe conducted a retrospective study of patients with acute anterior circulation ischemic stroke who underwent diffusion-weighted imaging(DWI),SWI,perfusion-weighted imaging(PWI),and magnetic resonance angiography(MRA).Stroke severities were measured using the National Institutes of Health Stroke Scale(NIHSS).A favorable outcome was defined as a modified Rankin Scale(mRS)of 0-2at 3.0 months.A modified Alberta Stroke Program Early CT Score(ASPECTS)was used to evaluate AHVS on SWI and the infarction lesions on DWI.We evaluated AHVs,the infarction,and the perfusion lesions,and assessed the correlations of SWI/DWI with PWI/DWI and PWI-DWI mismatch volumes.The receiver operating characteristic(ROC)curve was used to find the cutoff SWI-DWI mismatch to detect optimal PWI-DWI mismatch.The associations of SWI-DWI mismatch with clinical data and MR parameters were analyzed.ResultsFifty-three patients were enrolled in this study.SWI/DWI was positively correlated with PWI/DWI and PWI-DWI mismatch volumes.ROC curve revealed the cutoff SWI/DWI mismatch ratio was set at 1.14(sensitivity 74.1%,specificity 82.1%).Patients with SWI-DWI mismatch were more likely to have stenosis of theintracranial internal cerebral artery or proximal middle cerebral artery,smaller infarction,and larger PWI-DWI mismatch volumes.The stroke severities of these patients on admission and at discharge were more likely to be mild or moderate.Favorable outcomes between the two groups were not significantly different.ConclusionSWI-DWI mismatch is an effective method by which to evaluate the detection value of AHVs for penumbra,and is related to mild or moderate severity of acute stroke,but not to a favorable outcome.Part two: The association between asymmetrically hypointense veins on SWI and collateral statusObjective The status of collateral flow is an important factor that influences the evolution of the infarct core and the prognosis of ischemic stroke.However,the association between collateral status and AHVs is still not clear.Thus,we conducted a research to explore the relationship between them.Methods We retrospectively enrolled acute ischemic stroke patients with severe stenosis or occlusion of M1 segment middle cerebral artery ± intracranial internal carotid artery.All the patients underwent DWI,SWI,and computed tomography angiography(CTA)of intracranial and cervical arteries within 72 hours from symptom onset.We explored the association of the level of AHVs with the degree of the regional leptomeningeal score(r LMC)on baseline CTA and other clinical and image data.The factors that might influence the prognosis of stroke were also analyzed.Results Fifteen patients with mild AHVs and 15 with extensive AHVs were enrolled in our study.Patients with extensive AHVs had better collateral status,smaller DWI infarction lesion,and more mild NIHSS scores on admission and at discharge.The high degree of r LMC,small DWI lesion,young age and mild NIHSS scores,but not extensive AHVs were related with favorable outcome at 3 months after stroke.Conclusion Extensive AHVs can reflect good collateral circulation to some extent,but it can not be equivalent to or replace the collateral status.Part three: The predictive value of susceptibility vessel sign to clinical outcome for acute stroke patients untreated with thrombolysisObjective The susceptibility vessel sign(SVS)on SWI is related to the presence of deoxyhemoglobin.The location and length of it may predict poor outcome for patients received thrombolysis or mechanical thrombectomy.The aim of our study is to assess the predictive value of SVS to clinical outcome for patients untreated with thrombolysis.MethodsWe conducted a retrospective study of patients who hadn't received thrombolysis therapy with acute anterior circulation ischemic stroke.All of them underwent DWI,SWI,and MRA within 3 days from symptom onset.The presence(SVS+)or absence of the SVS(SVS-)was recorded.The characteristics of SVS like location and length were also assessed.The univariate analysis and multivariate logistic regression analysis were used to examine the association between SVS and clinical outcome.ResultsForty-three patients with SVS+ and 73 with SVS-were included in our study.MRS ?2 at 3 months occurred in 41.9% patients in the SVS+ group and 79.4 % in the SVS-group(P < 0.001).On multivariate analysis,the presence of SVS was an independent parameter before treatment that could predict m RS >2 at 3 months(odds ratio,3.390;95% confidence interval,1.122-10.240;P = 0.030).For patients with SVS,the location and length of SVS were not independent predictors to clinical outcome.ConclusionThe presence of SVS may predict poor clinical outcome for acute stroke patients untreated with thrombolysis.