Application Of High-Resolution Magnetic Resonance Imaging In Assessment Of Carotid Artery Dissection And Cerebral Artery Dolichoectasia

PART Ⅰ:APPLICATION OF THREE-DIMENSIONAL HIGHRESOLUTION MAGNETIC RESONANCE IMAGING IN ASSESSMENT OF CERVICAL ARTERY DISSECTIONBackground:Cervical artery dissection(CAD)is a arterial disease in which the tissue layers of the vessel wall separate as a result of abnormal entry of blood components into the vessel wall.Blood can enter the vessel wall through the intima that has torn for a variety of reasons or ruptured vasa vasorum.Previously,the diagnosis of cervical artery dissection has been made by digital subtraction angiography(DSA),computed tomography angiography(CTA),magnetic resonance angiography(MRA)and other imaging tests.However,these traditional angiographic imaging modalities do not provide sufficient information about the vessel wall and have insufficient ability to demonstrate wall lesions such as smaller intramural hematomas.Three-dimensional(3D)high-resolution magnetic resonance imaging(HR-MRI),an emerging imaging technique,has demonstrated good visualization of wall lesion in the study of a variety of other craniocervical artery diseases and may therefore also be useful in the assessment of signs and diagnosis of disease in cervical artery dissection.Objective:The diagnostic value of 3D HR-MRI vessel wall imaging for CAD was evaluated by retrospectively analyzing imaging signs on HR-MRI in 14 patients with CAD.Methods:Patients registered from January 2016 to January 2021 in high-resolution MRI database of the China-Japan Friendship Hospital and were finally diagnosed with CAD,were consecutively included in this study for a retrospective analyzation.Cervical artery dissection was diagnosed by imaging presentations combined with clinical symptoms and signs.Given there is a lack of widely accepted gold standard for the diagnosis of cervical artery dissection,all patients included were required to have one or more direct signs of artery dissection(intramural hematoma,intimal flap or double lumen)on at least one examination including HR-MRI,DSA,CTA,MRA.After excluding patients with the presence of CNS vasculitis,smoker’s disease,the presence of atherosclerotic plaque in the entrapped artery and cardiogenic embolism,14 patients were finally included.Two experienced physicians reviewed the images independently,and dissection length,intramural hematoma,thickness and signal intensity heterogeneous,intimal flap,double lumen,intraluminal thrombus,and dilation percentage of the external diameter of dissection were evaluated.Consistency of evaluation was measured using Cohen’s κcoefficient,and consistency of measuring dissection length,intramural hematoma thickness and dilation percentage of arterial external diameter dilatation was assessed using interclass correlation coefficient(ICC).In addition,we summarized the clinical presentation of the patients.Results:A total of 14 patients with CAD were included in this study,with a mean age of 43.9±10.9 years old,including 6 male and 8 female patients.Seven of the 14 patients presented with acute ischemic stroke and 7 presented with neurological symptoms without acute ischemic stroke.The most common clinical presentation was weakness of one limb or one side of the body(50.0%).The least common clinical manifestation was facial paralysis(7.1%),followed by headache(14.3%).Eight patients(57.1%)had at least one vascular risk factors such as hypertension,smoking or trauma.Sixteen dissection lesions were identified in patients,of which 12(75.0%)were in the internal carotid artery and 4(25.0%)in the vertebral artery.Among the 16 lesions,9 patients presented with unilateral internal carotid arteries dissection(64.3%),3 with unilateral vertebral dissection(21.4%),2 with multiple dissection(14.3%).dissection caused no or mild stenosis in 6 lesions,moderate stenosis in 4 lesions,and severe stenosis or occlusion in 6 lesions.On 3D HR-MRI images,the presence of intramural hematoma was determined in 13 lesions of 11 patients(81.3%),intimal flaps were detected in 9 of 9 patients(56.3%),double lumen signs were detected in 4 of 4 patients(25.0%),and intraluminal thrombus was detected in 4 of 4 patients(25.0%).The mean length of dissection was 25.1 ± 13.7 mm,with the mean dilation percentage for the outer diameter of the dissection was 151.3±28.6%.The mean thickness of intramural hematoma was 4.3±2.3mm.The interobserver agreement was high for the identification of intramural hematomas(κ=0.818),intimal flaps(κ=0.871),and the double lumen sign(κ=0.846);it was moderate for identifying intraluminal thrombi(κ=0.714);and it was high for the measurements of the length of dissection(ICC=0.919),thickness of intramural hematoma(ICC=0.994),and percentage of dilation(ICC=0.919).Follow-up 3D HR-MRI was performed in six patients with seven lesions(204.8±109.9 days meanly).On follow-up 3D HR-MRI,intramural hematoma disappearance was found in 6 lesions(85.7%),including luminal complete recanalization in 5 lesions(71.4%)and luminal partial recanalization in 1 lesion(14.3%).For one lesion(14.3%),the intramural hematoma was reduced and became an intermediate signal intensity with luminal partial recanalization.Conclusions:1.In this study,intramural hematoma is the most common CAD imaging sign on 3D HR-MRI,while double lumen is the least common CAD sign.2.3D HR-MRI is able to reliably evaluate signs of artery dissection such as intramural hematoma,endothelial flap,double lumen and intraluminal thrombus,and good intraobserver consistency,making it an effective non-invasive technique for the diagnosis of CAD.PART Ⅱ:APPLICATION OF THREE-DIMENSIONAL HIGHRESOLUTION MAGNETIC RESONANCE IMAGING IN STUDDING THE IMAGING FEATURES OF VERTEBROBASILAR DOLICHOECTASIA AND MECHANISM OF CONCOMITANT ISCHEMIC STROKEBackground:Vertebrobasilar dolichoectasia(VBD)is a disease characterized by marked dilatation and elongation,distortion or angulation of the vertebral basilar artery.Previous clinical studies have used computed tomography angiography and magnetic resonance angiography to investigate the mechanisms of ischemic stroke in patients with prolonged dilatation of the vertebral basilar artery.The ability to visualize lesions such as small atherosclerotic plaques,interstitial layers and intramural hematomas in dilated arteries is insufficient.Three-dimensional(3D)high-resolution magnetic resonance imaging(HR-MRI)has now been shown to be an effective method for assessing the morphology and the composition of arterial wall lesions in a variety of craniocervical artery diseases,and the method has been used less frequently in studies of VBD.Objective:A retrospective analysis was performed to study the radiological features of 3D HR-MRI in patients with vertebrobasilar tortuous dilatation and to investigate the possible mechanisms of ischemic stroke in vertebrobasilar tortuous dilatation.Methods:Patients registered from July 2017 to June 2021 in high-resolution MRI database of the China-Japan Friendship Hospital and diagnosed with VBD were consecutively included in this study.Patients with the presence of CNS vasculitis,tumors,or cardiogenic embolism were excluded,and 26 patients were finally included for retrospective analysis.Patients were divided into stroke group or non-stroke group based on the presence of ischemic stroke in the posterior circulation area on brain MRI.We analyzed diameter,height of bifurcation and laterality of the basilar artery in both groups,and preliminarily analyzed the possible mechanisms of stroke in patients with VBD by comparing the features above and the clinical data and the transcranial Doppler ultrasound hemodynamic examination.HR-MRI images of the patients were reviewed by two reviewers.The consistency between the reviewers in evaluating the height of bifurcation and laterality of the basilar artery was assessed by Cohen’s κ coefficient,and the consistency in measuring the diameter of the basilar artery was assessed by the interclass correlation coefficient(ICC).Results:Twenty-six patients were included in this study with a mean age of 61.0±11.6 years,of which there were 21 male patients.There were 15 patients in the stroke group and 11 patients in the non-stroke group.No significant differences were found between the baseline levels of two groups in terms of age,hypertension,diabetes mellitus and hyperlipidaemia.Compared with the non-stroke group,the basilar artery diameter was significantly larger in the stroke group(6.57±1.00 mm vs.5.06±0.50 mm,P<0.001)and the basilar artery bifurcation height was higher(P=0.002),but basilar artery laterality were not significantly different between the two groups(P=0.763).There was a high degree of consistency between the 2 observers in evaluation of basilar artery diameter(ICC=0.991),basilar artery bifurcation height(κ=1.000)and laterality(κ=0.940).Thirty atherosclerotic plaques were found in the BA of 16 patients(stroke group,12;non-stroke group,4).Among the 30 atherosclerotic plaques,18 were in the greater curvature and 12 in the lesser curvature。One artery dissection and 2 dissecting aneurysms were found in the BAs of the 3 patients.Eighteen patients underwent TCD during their hospitalization,including 12 patients in the stroke group and 6 in non-stroke group.Mean values of mean velocity(Vm),systolic velocity(Vs),diastolic velocity(Vd),in the basilar artery were lower in the stroke group than in non-stroke group,and mean pulsatility index(PI)in the basilar artery was greater in the stroke group than in non-stroke group(0.91±0.20 vs.0.82±0.19,P=0.367),but no statistical difference was observed.Conclusions:1.Basilar artery diameter and bifurcation height were significantly higher in the stroke group than in non-stroke group.Basilar artery diameter and bifurcation height may be associated with the posterior circulation ischemic stroke in patients with VBD.2.The mechanism of stroke in patients with VBD may involve abnormal hemodynamics,atherosclerosis,and artery dissection.3.3D HR-MRI is a useful method for evaluating the risk and underlying mechanism of stroke in patients with VBD.