High-resolution Magnetic Resonance Imaging Reveals Hidden Etiologies of Symptomatic Vertebral Arterial Lesions

Magnetic resonance imaging for diagnostic workup of embolic stroke of undetermined source: A systematic review

BACKGROUND

Embolic stroke of undetermined source (ESUS) refers to ischemic stroke where the underlying cause of thromboembolism cannot be found despite the recommended diagnostic workup. Unidentified source of emboli hinders clinical decision-making and patient management with detrimental consequences on long-term prognosis. The rapid development and versatility of magnetic resonance imaging (MRI) make it an appealing addition to the diagnostic routine of patients with ESUS for the assessment of potential vascular and cardiac embolic sources.

AIMS

To review the use of MRI in the identification of cardiac and vascular embolic sources in ESUS and to assess the reclassification value of MRI examinations added to the conventional workup of ESUS.

SUMMARY OF REVIEW

We reviewed the use of cardiac and vascular MRI for the identification of a variety of embolic sources associated with ESUS, including atrial cardiomyopathy, left ventricular pathologies, and supracervical atherosclerosis in carotid and intracranial arteries and in distal thoracic aorta. The additional reclassification after MRI examinations added to the workup of patients with ESUS ranged from 6.1% to 82.3% and varied depending on the combination of imaging modalities.

CONCLUSION

MRI techniques allow us to identify additional cardiac and vascular embolic sources and may further decrease the prevalence of patients with the diagnosis of ESUS.

Association between Urine Albumin-to-creatinine Ratio and Intracranial Atherosclerotic Plaque in Chinese Adults - Results from the PRECISE Study

AIMS

Intracranial plaque may cause stroke in the absence of luminal stenosis. Although urine albumin-to-creatinine ratio (ACR) has been proved an established risk factor for cardiovascular disease, stroke and carotid atherosclerosis, little is known on the relationship between urine ACR and intracranial plaque.

METHODS

Subjects with history of stroke or coronary heart disease (CHD) were excluded in the PRECISE study. The intracranial plaque was assessed by vessel wall magnetic resonance imaging (MRI). Subjects were stratified according to ACR tertiles. Logistic regression and ordinal regression were performed to analyze the association between ACR and the presence of intracranial plaque or sum of the stenosis score for each artery.

RESULTS

2962 individuals were included with the mean age of 61.0±6.6 years. The median ACR was 11.7mg/g (interquartile range 7.0-22.0 mg/g), and the mean estimated glomerular filtration rate (eGFR) based on combination of creatinine and cystatin C was 88.5±14.8 ml/min·1.73m2. 495 (16.7%) participants had intracranial plaque. The highest ACR tertile with ACR ＞16.00mg/g was independently associated with the presence of intracranial plaque (OR 1.38, 95% CI: 1.05-1.82, p=0.02) and the odds of higher intracranial plaque burden (common OR 1.39, 95% CI: 1.05-1.83, p=0.02) after adjustment of confounding factors. No significant association was observed between eGFR and intracranial plaque presence or intracranial plaque burden.

CONCLUSIONS

Among a low-risk community-dwelling population without prior stroke or CHD in China, ACR was independently associated with intracranial plaque presence and plaque burden measured by vessel wall MRI.

Percutaneous transluminal angioplasty and stenting for vertebral artery stenosis

BACKGROUND

Vertebral artery stenosis (narrowing of the vertebral artery) is an important cause of posterior circulation ischaemic stroke. Medical treatment (MT) e.g. controlling risk-factors and drug treatment, surgery, and endovascular treatment (ET) are the prevailing treatment strategies for symptomatic vertebral artery stenosis. ET consist s of percutaneous transluminal angioplasty (balloon catheter through the skin), with or without stenting. However, optimal management of people with symptomatic vertebral artery stenosis has not yet been established.

OBJECTIVES

To assess the safety and efficacy of percutaneous transluminal angioplasty, with or without stenting, combined with MT, compared to MT alone, in people with episodes of cerebral ischaemia due to vertebral artery stenosis.

SEARCH METHODS

We searched the Cochrane Stroke Group, MEDLINE, Embase, BIOSIS, and two other indexes in Web of Science, China Biological Medicine Database, Chinese Science and Technique Journals Database, China National Knowledge Infrastructure and Wanfang Data, as well as ClinicalTrials.gov trials register and the World Health Organization (WHO) International Clinical Trials Registry Platform to 23 July 2021.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) that compared ET plus MT with MT alone in treating people aged 18 years or over with symptomatic vertebral artery stenosis. We included all types of ET modalities (e.g. angioplasty alone, balloon-mounted stenting, and angioplasty followed by placement of a self-expanding stent). MT included risk factor control, antiplatelet therapy, lipid-lowering therapy, and individualised management for people with hypertension or diabetes.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened potentially eligible studies, extracted data, and assessed trial quality and risk of bias.  We applied the GRADE approach to assess the certainty of evidence. The primary outcomes were 30-day post-randomisation death/stroke (short-term outcome) and fatal/non-fatal stroke after 30 days post-randomisation to completion of follow-up (long-term outcome).  MAIN RESULTS: We included three RCTs with 349 participants with symptomatic vertebral artery stenosis with a mean age of 64.4 years. The included RCTs were at low risk of bias overall. However, all included studies had a high risk of performance bias because blinding of the ET was not feasible. There was no significant difference in 30-day post-randomisation deaths/strokes between ET plus MT and MT alone (risk ratio (RR) 2.33, 95% confidence interval (CI) 0.77 to 7.07; 3 studies, 349 participants; low-certainty evidence). There were no significant differences between ET plus MT and MT alone in fatal/non-fatal strokes in the territory of the treated vertebral artery stenosis after 30 days post-randomisation to completion of follow-up (RR 0.51, 95% CI 0.26 to 1.01; 3 studies, 349 participants; moderate-certainty evidence), ischaemic or haemorrhagic stroke during the entire follow-up period (RR 0.77, 95% CI 0.44 to 1.32; 3 studies, 349 participants; moderate-certainty evidence), death during the entire follow-up period (RR 0.78, 95% CI 0.37 to 1.62; 3 studies, 349 participants; low-certainty evidence), and stroke or transient ischaemic attack (TIA) during the entire follow-up period (RR 0.65, 95% CI 0.39 to 1.06; 2 studies, 234 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

This Cochrane Review provides low- to moderate-certainty evidence indicating that there are no significant differences in either short- or long-term risks of stroke, death, or TIA between people with symptomatic vertebral artery stenosis treated with ET plus MT and those treated with MT alone.

Arterial Wall Imaging in Angiographically Occult Spontaneous Subarachnoid Hemorrhage : New Insight into the Usual Suspect

Objective

The etiology of angiographically occult spontaneous subarachnoid hemorrhage (AOsSAH) is unclear. Threedimensional (3D) high-resolution vessel wall magnetic resonance imaging (HVM) might be useful in detecting the hidden arterial wall angiopathy in patients with AOsSAH. We aimed to demonstrate the feasibility of HVM for detecting the arterial cause of AOsSAH.

Methods

Patients, who were diagnosed with AOsSAH in the first evaluations and underwent HVM, were enrolled. Their clinical and radiologic data were retrospectively reviewed. Especially, focal enhancement of arterial wall on HVM and repetitive catheterized angiograms were precisely compared.

Results

Among 251 patients with spontaneous SAH, 22 patients were diagnosed with AOsSAH in the first evaluations (8.76%). After excluding three patients who did not undergo 3D-HVM, 19 patients were enrolled and classified as convexal (n=2) or perimesencephalic (n=4), and diffuse (n=13) groups. In convexal and perimesencephalic groups, no focal enhancement on HVM and no positive findings on repetitive angiography were noted. In diffuse group, 10 patients showed focal enhancement of arterial wall on HVM (10/13, 76.9%). Repeated angiography with 3D reconstruction revealed four patients of angiographically positive causative arteriopathy and possible lesion in one case in the concordant location of intramural enhancement on 3D-HVM (5/10, 50%). Three of them were treated with endovascular stent insertion. All patients, except one, recovered with good clinical outcome (3-month modified Rankin score, 0 and 1).

Conclusion

3D-HVM was useful in detecting hidden true arteriopathy in AOsSAH. It may provide new insights into the etiologic investigation of AOsSAH by proving information about the arterial wall status.

Presence of Vessel Wall Hyperintensity in Unruptured Arteriovenous Malformations on Vessel Wall Magnetic Resonance Imaging: Pilot Study of AVM Vessel Wall "Enhancement"

Purpose: High-resolution vessel wall magnetic resonance imaging (VW-MRI) could provide a way to identify high risk arteriovenous malformation (AVM) features. We present the first pilot study of clinically unruptured AVMs evaluated by high-resolution VW-MRI.

Methods: A retrospective review of clinically unruptured AVMs with VW-MRI between January 1, 2016 and December 31, 2018 was performed documenting the presence or absence of vessel wall “hyperintensity,” or enhancement, within the nidus as well as perivascular enhancement and evidence of old hemorrhage (EOOH). The extent of nidal vessel wall “hyperintensity” was approximated into five groups: 0, 1–25, 26–50, 51–75, and 76–100%.

Results: Of the nine cases, eight demonstrated at least some degree of vessel wall nidus “hyperintensity.” Of those eight cases, four demonstrated greater than 50% of the nidus with hyperintensity at the vessel wall, and three cases had perivascular enhancement adjacent to nidal vessels. Although none of the subjects had prior clinical hemorrhage/AVM rupture, of the six patients with available susceptibility weighted imaging to assess for remote hemorrhage, only two had subtle siderosis to suggest prior sub-clinical bleeds.

Conclusion: Vessel wall “enhancement” occurs in AVMs with no prior clinical rupture. Additional studies are needed to further investigate the implication of these findings.

T2-Weighted Whole-Brain Intracranial Vessel Wall Imaging at 3 Tesla With Cerebrospinal Fluid Suppression

Background

T₂-weighted (T₂w) intracranial vessel wall imaging (IVWI) provides good contrast to differentiate intracranial vasculopathies and discriminate various important plaque components. However, the strong cerebrospinal fluid (CSF) signal in T₂w images interferes with depicting the intracranial vessel wall. In this study, we propose a T₂-prepared sequence for whole-brain IVWI at 3T with CSF suppression.

Methods

A preparation module that combines T₂ preparation and inversion recovery (T₂IR) was used to suppress the CSF signal and was incorporated into the commercial three-dimensional (3D) turbo spin echo sequence-Sampling Perfection with Application optimized Contrast using different flip angle Evolution (SPACE). This new technique (hereafter called T₂IR-SPACE) was evaluated on nine healthy volunteers and compared with two other commonly used 3D T₂-weighted sequences: T₂w-SPACE and FLAIR-SPACE (FLAIR: fluid-attenuated inversion recovery). The signal-to-noise ratios (SNRs) of the vessel wall (VW) and CSF and contrast-to-noise ratios (CNRs) between them were measured and compared among these three T₂-weighted sequences. Subjective wall visualization of the three T₂-weighted sequences was scored blindly and independently by two radiologists using a four-point scale followed by inter-rater reproducibility analysis. A pilot study of four stroke patients was performed to preliminarily evaluate the diagnostic value of this new sequence, which was compared with two conventional T₂-weighted sequences.

Results

T₂IR-SPACE had the highest CNR (11.01 ± 6.75) compared with FLAIR-SPACE (4.49 ± 3.15; p < 0.001) and T₂w-SPACE (-56.16 ± 18.58; p < 0.001). The subjective wall visualization score of T₂IR-SPACE was higher than those of FLAIR-SPACE and T₂w-SPACE (T₂IR-SPACE: 2.35 ± 0.59; FLAIR-SPACE: 0.52 ± 0.54; T₂w-SPACE: 1.67 ± 0.58); the two radiologists' scores showed excellent agreement (ICC = 0.883).

Conclusion

The T₂IR preparation module markedly suppressed the CSF signal without much SNR loss of the other tissues (i.e., vessel wall, white matter, and gray matter) compared with the IR pulse. Our results suggest that T₂IR-SPACE is a potential alternative T₂-weighted sequence for assessing intracranial vascular diseases.

Usefulness of 3D High-resolution Vessel Wall MRI in Diffuse Nonaneurysmal SAH Patients

PURPOSE

In 15-20% of patients with nontraumatic diffuse subarachnoid hemorrhage (SAH), the initial conventional angiography does not reveal a causative vascular abnormality, such as intracranial aneurysm. In this study, we evaluated clinical utility of 3D high-resolution vessel wall magnetic resonance imaging (HR-VWI) in patients with diffuse nonaneurysmal SAH.

METHODS

A total of 17 patients with diffuse nonaneurysmal SAH were included in this retrospective study. We characterized demographics and HR-VWI findings and reviewed the clinical management and outcomes.

RESULTS

Of the patients 14 (14/17; 82.4%,) showed abnormal findings on HR-VWI, including 5 with intracranial dissections (29.4%), 3 with blood blister-like aneurysm (17.6%), 1 with ruptured fusiform aneurysm (5.9%), and 5 with focal nodular wall enhancement without unclassified pathology (29.4%). Of these patients were treated with endovascular management. Most patients (16/17) had a favorable modified Rankin scale scores of 0-2 on discharge.

CONCLUSION

The 3D HR-VWI revealed various hidden pathologies, such as intracranial arterial dissection, blood blister-like aneurysm, and fusiform aneurysm in patients with diffuse nonaneurysmal SAH. In addition, 3D HR-VWI had an impact on the management of SAH. The 3D HR-VWI can be a complementary diagnostic method for patients with diffuse nonaneurysmal SAH in a research or clinical setting.

Association of Hypertension With Both Occurrence and Outcome of Symptomatic Patients With Mild Intracranial Atherosclerotic Stenosis: A Prospective Higher Resolution Magnetic Resonance Imaging Study

Background

Intracranial atherosclerotic plaque causing mild luminal stenosis might lead to acute ischemic events. However, the difference between culprit and nonculprit lesions is unclear, as are the factors associated with favorable treatment outcomes.

Purpose

To quantify characteristics of intracranial atherosclerosis with mild luminal stenosis and to identify factors associated with lesion type (culprit or nonculprit) and with clinical outcomes.

Study Type

Prospective

Population

293 patients who had acute stroke with mild luminal stenosis (<50%) in the middle cerebral or basilar artery.

Field Strength/Sequence

3.0 T higher resolution magnetic resonance imaging (hrMRI) of intracranial arteries and whole brain MR images.

Assessment

Morphological and compositional analysis of plaques was performed. This included assessment of plaque volume, plaque burden, remodeling ratio, eccentricity, intraplaque hemorrhage, and enhancement ratio. Clinical outcomes were assessed according to the modified Rankin Scale (mRS) at day 90, with a favorable outcome being defined as a 90‐day mRS ≤2.

Statistical Tests

The odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by a logistic regression model.

Results

Hypertension (OR 5.2; 95% CI 2.6–10.3; P < 0.05) and hrMRI enhancement ratio (OR 2.7; 95% CI 1.4–5.1; P < 0.05) were independently associated with lesion type. Patients without hypertension had significantly more (P < 0.05) favorable outcomes (124/144) than patients with hypertension (97/149). Most hypertensive patients without any previous blood pressure control (54/63) had a favorable outcome. However, these patients were significantly younger (P < 0.05) than those with adequate blood pressure control. After adjusting for all significant characteristics, hypertension duration (OR 1.19; 95% CI 1.09–1.29; P < 0.05), hypertension management (OR 2.49; 95% CI 1.18–5.26; P < 0.05), and enhancement ratio (OR 0.01; 95% CI 0.001–0.157; P < 0.05) were found to be independent high‐risk factors for outcome prediction.

Data Conclusion

hrMRI provided incremental value over traditional risk factors in identifying higher risk intracranial atherosclerosis with mild luminal stenosis.

Level of Evidence

2

Technical Efficacy

Stage 2

Intramural Hematoma Shape and Acute Cerebral Infarction in Intracranial Artery Dissection: A High-Resolution Magnetic Resonance Imaging Study

BACKGROUND

Intracranial artery dissection (IAD) is gaining recognition as an important cause of stroke, but limited information is available about the morphology of the dissection. This study aimed to investigate the relationship between acute cerebral infarctions and the shape of hematoma in patients with IADs using high-resolution magnetic resonance imaging (HRMRI).

METHODS

We enrolled consecutive patients who presented with vascular headaches, transient ischemic attacks, or ischemic strokes with acute IAD confirmed by HRMRI using key pathognomonic radiological findings of IAD, including intimal flap, intramural hematoma (IMH), and double lumen. All patients were enrolled and HRMRI was performed, both within 7 days of symptom onset. All patients with acute ischemic infarction within 7 days were enrolled. Patients were divided into 2 groups: those with a proximal dominant intramural hematoma (PIMH) and those with a distal dominant intramural hematoma (DIMH). A PIMH was defined as when the volume of the hematoma in the proximal region was greater than that in the distal region, and a DIMH was defined as when the distal region was greater than that in the proximal region. Clinical and radiological characteristics between the 2 groups were compared using univariable and multivariable logistic regression.

RESULTS

The mean age of the 42 participants was 52.6 ± 12.7 years, and 24 (57.1%) were male. Twenty-seven (64.3%) had a PIMH and 15 (35.7%) had a DIMH. Thirty-six (85.7%) showed a double lumen and 27 (64.3%) showed a dissecting flap. Acute infarction was observed in 31 (73.8%) patients. Patients with PIMHs showed a higher prevalence of cerebral infarction than those with DIMHs (96.3 vs. 33.3%; p < 0.001). Univariable (odds ratio [OR] 52.00; 95% confidence interval [CI] 5.386-502.082; p = 0.001) and multivariable (OR 65.43; 95% CI 5.20-822.92; p = 0.001) analyses showed that only dissection type was independently associated with the risk of cerebral infarction.

CONCLUSION

In patients with cerebral artery dissections, the shape of IMHs was independently associated with cerebral infarction. PIMHs may be more closely associated with cerebral infarctions than DIMHs.

Magnetic resonance vessel wall imaging in cerebrovascular diseases

Cerebrovascular diseases manifest as abnormalities of and disruption to the intracranial vasculature and its capacity to carry blood to the brain. However, the pathogenesis of many cerebrovascular diseases begins in the vessel wall. Traditional luminal and perfusion imaging techniques do not provide adequate information regarding the differentiation, onset, or progression of disease. Intracranial high-resolution MR vessel wall imaging (VWI) has emerged as an invaluable technique for understanding and evaluating cerebrovascular diseases. The location and pattern of contrast enhancement in intracranial VWI provides new insight into the inflammatory etiology of cerebrovascular diseases and has potential to permit earlier diagnosis and treatment. In this report, technical considerations of VWI are discussed and current applications of VWI in vascular malformations, blunt cerebrovascular injury/dissection, and steno-occlusive cerebrovascular vasculopathies are reviewed.

Culprit intracranial plaque without substantial stenosis in acute ischemic stroke on vessel wall MRI: A systematic review

BACKGROUND AND AIMS

Intracranial atherosclerotic plaque is associated with ischemic strokes without substantial stenosis, and needs better characterization. We aim to investigate the clinical significance of intracranial plaque without substantial stenosis by high resolution vessel wall MRI (vwMRI) through a systematic review of existing studies.

METHODS

Studies investigating intracranial arterial atherosclerotic plaques without substantial stenosis in acute ischemic stroke patients using vwMRI were systematically identified by searching the PubMed and Medline database and article reference lists. Study characteristics were recorded, the methodological quality of eligible studies was assessed, relevant clinical data were extracted, and collective data was analyzed.

RESULTS

Twenty-one studies were identified as eligible. 463 patients were included without stenosis of the intracranial arteries, and 651 patients were included with stenosis <50%. The prevalence of intracranial plaque revealed by vwMRI among acute/subacute ischemic stroke patients with non-stenotic Magnetic Resonance Angiography (MRA) was 50.6% (95% confidence interval (CI), 46.1%-55.1%). The prevalence of <50% MRA stenotic culprit plaque among acute/subacute ischemic stroke patients with a clinical diagnosis of intracranial atherosclerosis was 51.2% (95% CI, 38.4%-64.0%). Plaques features, including wall enhancement, positive remodeling, intraplaque hemorrhage, plaque location and eccentricity, were associated with acute stroke, progressive motor deficits and unfavorable overall functional outcomes.

CONCLUSIONS

Intracranial high-risk plaque with zero or mild degree of stenosis is more prevalent than previously acknowledged, and is associated with ischemic stroke and unfavorable outcome. VwMRI can identify the high-risk plaque features, which may act as a promising tool to better risk stratify these patients.

Clinical application of high-resolution MRI in combination with digital subtraction angiography in the diagnosis of vertebrobasilar artery dissecting aneurysm: An observational study (STROBE compliant)

Vertebrobasilar artery dissecting aneurysm (VBA-DA) is associated with serious complications and poor prognosis in patients. High-resolution magnetic resonance imaging (HR-MRI) is a noninvasive method for the diagnosis of VBA-DA.VBA-DAs were classified according to the feature of HR-MRI in combination with digital subtraction angiography (DSA), and the clinical outcomes of different types of VBA-DAs were analyzed. Thirty-nine patients with 42 VBA-DAs were included and underwent HR-MRI, including three-dimensional T1 weighted image, three-dimensional T2 weighted image (3D-T2WI), three-dimensional time of flight MRA (3D-TOF-MRA), and three-dimensional fast imaging employing steady state acquisition (3D-FIESTA), and hematoma and flaps were compared. The follow-up was 3 to 25 months. The VBA-DAs were classified based on the images of HR-MRI and DSA, and the prognosis was analyzed.VBA-DAs more frequently occurred on the vertebral artery, especially on the dominant vertebral artery. 3D-TOF-MRA showed high signal from hematoma, and 3D-FIESTA showed high signal from flaps. Based on HR-MRI images in combination with DSA, VBA-DAs were classified into 4 types: classical, stenosis, spiral, and hemorrhagic. The patients with the classical VBA-DAs had a higher improvement rate and a lower exacerbation rate. The patients with spiral and hemorrhagic VBA-DAs had poor clinical outcomes. The patients with stenosis VBA-DAs had poorer clinical outcomes than classical types and better clinical outcomes than spiral and hemorrhagic types.The detection of intramural hematoma and dissection flap using HR-MRI provides basic information for the diagnosis of VBA-DA. Individualized therapeutic strategies can be designed for the treatment of VBA-DAs with different features of DSA and HR-MRI.

Clinical Significance of Intraplaque Hemorrhage in Low- and High-Grade Basilar Artery Stenosis on High-Resolution MRI

BACKGROUND AND PURPOSE

Intraplaque hemorrhage within intracranial atherosclerotic plaques identified by high-resolution MR imaging has been studied as a potential marker of stroke risk. However, previous studies only examined intracranial arteries with high-grade stenosis (degree of stenosis, >50%). This study aimed to ascertain the clinical relevance of intraplaque hemorrhage in patients with low- and high-grade stenotic basilar artery plaques.

MATERIALS AND METHODS

Patients with basilar artery stenosis (n = 126; mean age, 62 ± 10 years; 66 symptomatic and 60 asymptomatic) underwent high-resolution MR imaging. The relationship between imaging findings (intraplaque hemorrhage, contrast enhancement, degree of stenosis, minimal lumen area, and plaque burden) and symptoms was analyzed.

RESULTS

Intraplaque hemorrhage was identified in 22 patients (17.5%), including 21 (31.8%) symptomatic patients and 1 (1.7%) asymptomatic patient. Multivariate analysis showed that intraplaque hemorrhage was the strongest independent marker of symptomatic status (odds ratio, 27.5; 95% CI, 3.4-221.5; P = .002). Contrast enhancement was also independently associated with symptomatic status (odds ratio, 9.9; 95% CI, 1.5-23.6; P = .016). Stenosis, minimal lumen area, and plaque burden were not correlated with symptoms (P > .05). Intraplaque hemorrhage was present in both low- and high-grade stenotic basilar arteries (11.3% versus 16.3%, P = .63). Diagnostic performance values of intraplaque hemorrhage for patients with acute/subacute symptomatic stroke were the following: specificity, 98.3%; sensitivity, 31.8%; positive predictive value, 95.5%; and negative predictive value, 56.7%.

CONCLUSIONS

Intraplaque hemorrhage is present in both low- and high-grade stenotic basilar artery plaques and is independently associated with symptomatic stroke status. Intraplaque hemorrhage may identify high-risk plaque and provide new insight into the management of patient with stroke without significant stenosis.

Feasibility of improved motion-sensitized driven-equilibrium (iMSDE) prepared 3D T1-weighted imaging in the diagnosis of vertebrobasilar artery dissection

BACKGROUND AND PURPOSE

This study was to evaluate the diagnostic value of improved motion-sensitized driven-equilibrium (iMSDE)-prepared 3D T1-weighted magnetic resonance imaging (MRI) (iMSDE-3DMRI) in intracranial vertebrobasilary dissection (VBD) and to compare iMSDE-3DMRI images with those obtained using 2D high-resolution (HR) MRI with respect to their diagnostic performance in VBD.

MATERIALS AND METHODS

We retrospectively reviewed 105 lesions from 102 patients who underwent multimodal imaging and contrast-enhanced iMSDE-3DMRI (CE-iMSDE-3DMRI). The 2D-HRMRI protocol comprised four axial HR images. The CE-iMSDE-3DMRI images were reformatted in the axial, coronal, and sagittal planes. The 2D-HRMRI-based diagnosis was compared with the final diagnosis. The 2D-HRMRI and CE-iMSDE-3DMRI images were examined independently for the diagnosis performance of dissection.

RESULTS

VBD was confirmed in 66 lesions in 63 patients; 17 patients had confirmed atherosclerosis, and 22 had no lesions in the vertebrobasilar artery. Diagnostic performances of 2D-HRMRI (AUC, 0.839±0.04; sensitivity, 94.0; specificity, 79.5; diagnostic accuracy, 88.6) CE-iMSDE-3DMRI (AUC, 0.847±0.04; sensitivity, 84.8; specificity, 84.6; diagnostic accuracy, 84.7) and 2D-HRMRI+CE-iMSDE-3DMRI (AUC, 0.893±0.03; sensitivity, 97.0; specificity, 85.0; diagnostic accuracy, 92.5) were good. Comparisons of the diagnostic performance of 2D-HRMRI andCE-iMSDE-3DMRI showed that combined interpretation of 2D-HRMRI and iMSDE-3DMRI yields a significantly higher diagnostic performance than that of 2D-HRMRI (P=0.042).

CONCLUSIONS

CE-iMSDE-3DMRI showed good diagnostic performance for the diagnosis of intracranial VBD. These results suggest that CE-iMSDE-3DMRI can be used in combination with 2D-HRMRI for the diagnosis of intracranial VBD.

Efficacy of high-resolution cone-beam CT in the evaluation of perforators in vertebral artery dissection

Introduction A major complication of internal coil trapping for vertebral artery dissection (VAD) is medullary infarction associated with perforator occlusion. Currently, higher spatial resolution imaging can be obtained with high-resolution cone-beam computed tomography (VASO CT), and the efficacy of perforator visualization adjacent to VAD was examined. Methods Eight patients who underwent internal coil trapping or stent-supported coil embolization underwent VASO CT to evaluate perforators around VAD. Visualization of perforators was compared with conventional digital subtraction angiography (DSA) and three-dimensional rotational angiography (3D-RA). Postoperative MRI was performed in all patients to investigate ischemic complications. The relationship between the perforators and the infarction was analyzed. Results Perforator visualization was much clearer on VASO CT than on 2D DSA or 3D-RA. It was sharp enough to identify each perforating artery. Medullary infarctions were detected in two cases. In these two cases, each ischemic lesion corresponded to the territory of a perforator that was well visualized on VASO CT. The axial view with adjoining tissue structures on VASO CT was useful to detect the territories of perforators. Conclusions VASO CT is an efficient modality for the detection and identification of perforators in the vicinity of VAD. It provides accurate anatomical information about the vertebrobasilar system that is useful for the treatment of unruptured VAD.

High-resolution Magnetic Resonance Vessel Wall Imaging for Intracranial Arterial Stenosis

OBJECTIVE

To discuss the feasibility and clinical value of high-resolution magnetic resonance vessel wall imaging (HRMR VWI) for intracranial arterial stenosis.

DATE SOURCES

We retrieved information from PubMed database up to December 2015, using various search terms including vessel wall imaging (VWI), high-resolution magnetic resonance imaging, intracranial arterial stenosis, black blood, and intracranial atherosclerosis.

STUDY SELECTION

We reviewed peer-reviewed articles printed in English on imaging technique of VWI and characteristic findings of various intracranial vasculopathies on VWI. We organized this data to explain the value of VWI in clinical application.

RESULTS

VWI with black blood technique could provide high-quality images with submillimeter voxel size, and display both the vessel wall and lumen of intracranial artery simultaneously. Various intracranial vasculopathies (atherosclerotic or nonatherosclerotic) had differentiating features including pattern of wall thickening, enhancement, and vessel remodeling on VWI. This technique could be used for determining causes of stenosis, identification of stroke mechanism, risk-stratifying patients, and directing therapeutic management in clinical practice. In addition, a new morphological classification based on VWI could be established for predicting the efficacy of endovascular therapy.

CONCLUSIONS

This review highlights the value of HRMR VWI for discrimination of different intracranial vasculopathies and directing therapeutic management.

Treatment and imaging of intracranial atherosclerotic stenosis: current perspectives and future directions

BACKGROUND AND PURPOSE

Intracranial atherosclerosis is a common cause of stroke worldwide. It results in ischemic stroke due to different mechanisms including artery-to-artery embolism, in situ thrombo-occlusion, occlusion of perforating arteries, and hemodynamic failure. In this review, we present an overview of current treatment and imaging modalities in intracranial atherosclerotic stenosis.

METHODS

PubMed was searched for relevant articles in English that evaluated the treatment and imaging of intracranial atherosclerotic stenosis (ICAS).

RESULTS

Aggressive medical management, consisting of dual antiplatelet therapy and intensive risk factor management, is important in patients with ICAS because of a substantial risk of recurrent stroke, approximately 20% in the first year, in patients on aspirin or warfarin alone. Recent trials have suggested that, aggressive medical therapy results in better outcome as compared with intracranial stenting. However, the question remains what the optimal treatment strategy would be in patients with recurrent strokes in the setting of failed aggressive medical therapy. Moreover, controversy exists whether a subgroup of patients with symptomatic ICAS could benefit from intracranial stenting if selection is based on radiological evidence of hemodynamic failure. With regard to imaging, transcranial Doppler ultrasound and magnetic resonance angiography are useful screening tests for exclusion of ICAS, but need confirmation by other imaging modalities when stenosis is suggested. Computed tomography angiography has a high positive and negative predictive value for detection of intracranial luminal stenosis of 50% or higher, but performs worse than digital subtraction angiography with regard to establishing the exact degree of luminal stenosis. Novel imaging techniques including high-resolution CT and MRI better identify plaque characteristics than conventional imaging methods.

CONCLUSIONS

Currently, aggressive medical management remains the standard of care for patients with ICAS. Further research is needed to identify high-risk subgroups and to develop more effective treatments for ICAS patients.

More Precise Imaging Analysis and Diagnosis of Moyamoya Disease and Moyamoya Syndrome Using High-Resolution Magnetic Resonance Imaging

BACKGROUND

The diagnosis of moyamoya disease (MMD) is often uncertain. Moyamoya syndrome (MMS) is often misdiagnosed as MMD. High-resolution magnetic resonance imaging (HR-MRI) enables vessel wall assessment to obtain more precise diagnoses. The aim of this study was to determine the true etiologies of arterial steno-occlusion in patients with an angiographic diagnosis of MMD or MMS using HR-MRI.

METHODS

HR-MRI was performed in 21 adult patients with angiographically proven MMD or MMS. A definite diagnosis was based on the HR-MRI findings. The diagnoses made via the 2 different imaging technologies were compared, and significant findings were analyzed.

RESULTS

A total of 21 patients were enrolled, including 7 patients with angiographically proven MMD and 14 patients with angiographically proven MMS. Among the 7 patients with MMD, HR-MRI confirmed the diagnosis of MMD in 6; the remaining patient was considered to have atherosclerosis in the bilateral distal internal carotid arteries (ICAs) and the left middle cerebral artery. Among the 14 patients with MMS, HR-MRI confirmed MMD in 6 patients (including 2 patients with unilateral MMD), atherosclerosis in 5 patients (including 3 patients with bilateral atherosclerosis and 2 with unilateral atherosclerosis), arterial dissection of the left ICA in 1 patient, and MMD in the left cerebral hemisphere with atherosclerosis in the right hemisphere in 2 patients.

CONCLUSIONS

Differentiating MMD from MMS is difficult in certain situations, and HR-MRI may help provide a more in-depth understanding of MMD and MMS, thereby achieving a more reliable diagnosis.

Qualitative Evaluation of a High-Resolution 3D Multi-Sequence Intracranial Vessel Wall Protocol at 3 Tesla MRI

Background and Purpose

Intracranial vessel wall imaging using MRI has great potential as a clinical method for assessing intracranial atherosclerosis. The purpose of the current study was to compare three 3T MRI vessel wall sequences with different contrast weightings (T₁w, PD, T₂w) and dedicated sagittal orientation perpendicular to the middle cerebral artery, to the reconstructed sagittal image from a transverse 3D T₁w volumetric isotropically reconstructed turbo spin-echo acquisition (VIRTA), and provide a clinical recommendation.

Materials and Methods

The above-mentioned sequences were acquired in 10 consecutive Chinese ischemic stroke or TIA patients (age: 68 years, sex: 4 females) with angiographic-confirmed MCA stenosis at 3T. Institutional review board approval was obtained. Two raters qualitatively scored all images on overall image quality, presence of artifacts, and visibility of plaques. Data were compared using Repeated measures ANOVA and Sidak’s adjusted post hoc tests.

Results

All sequences except the T₂w sequence were able to depict the walls of the large vessels of the Circle of Willis (p<0.05). T₁w sagittal oblique VIRTA showed significantly more artifacts (p<0.01). Peripherally located plaques were sometimes missed on the sagittal sequences, but could be appreciated on the transverse T₁w VIRTA.

Conclusion

With the 3T multi-sequence vessel wall protocol we were able to assess the intracranial plaque with two different image contrast weightings. The sequence of preference to include in a clinical protocol would be the transverse 3D T₁w VIRTA based on absence of artifacts, larger coverage including the whole Circle of Willis, and excellent lesion depiction.

High-resolution intracranial vessel wall imaging: imaging beyond the lumen

Accurate and timely diagnosis of intracranial vasculopathies is important due to significant risk of morbidity with delayed and/or incorrect diagnosis both from the disease process as well as inappropriate therapies. Conventional vascular imaging techniques for analysis of intracranial vascular disease provide limited information since they only identify changes to the vessel lumen. New advanced MR intracranial vessel wall imaging (IVW) techniques can allow direct characterisation of the vessel wall. These techniques can advance diagnostic accuracy and may potentially improve patient outcomes by better guided treatment decisions in comparison to previously available invasive and non-invasive techniques. While neuroradiological expertise is invaluable in accurate examination interpretation, clinician familiarity with the application and findings of the various vasculopathies on IVW can help guide diagnostic and therapeutic decision-making. This review article provides a brief overview of the technical aspects of IVW and discusses the IVW findings of various intracranial vasculopathies, differentiating characteristics and indications for when this technique can be beneficial in patient management.

Quantitative Intracranial Atherosclerotic Plaque Characterization at 7T MRI: An Ex Vivo Study with Histologic Validation

BACKGROUND AND PURPOSE

In recent years, several high-resolution vessel wall MR imaging techniques have emerged for the characterization of intracranial atherosclerotic vessel wall lesions in vivo. However, a thorough validation of MR imaging results of intracranial plaques with histopathology is still lacking. The aim of this study was to characterize atherosclerotic plaque components in a quantitative manner by obtaining the MR signal characteristics (T1, T2, T2*, and proton density) at 7T in ex vivo circle of Willis specimens and using histopathology for validation.

MATERIALS AND METHODS

A multiparametric ultra-high-resolution quantitative MR imaging protocol was performed at 7T to identify the MR signal characteristics of different intracranial atherosclerotic plaque components, and using histopathology for validation. In total, 38 advanced plaques were matched between MR imaging and histology, and ROI analysis was performed on the identified tissue components.

RESULTS

Mean T1, T2, and T2* relaxation times and proton density values were significantly different between different tissue components. The quantitative T1 map showed the most differences among individual tissue components of intracranial plaques with significant differences in T1 values between lipid accumulation (T1 = 838 ± 167 ms), fibrous tissue (T1 = 583 ± 161 ms), fibrous cap (T1 = 481 ± 98 ms), calcifications (T1 = 314 ± 39 ms), and the intracranial arterial vessel wall (T1 = 436 ± 122 ms).

CONCLUSIONS

Different tissue components of advanced intracranial plaques have distinguishable imaging characteristics with ultra-high-resolution quantitative MR imaging at 7T. Based on this study, the most promising method for distinguishing intracranial plaque components is T1-weighted imaging.

High-resolution Vessel Wall Magnetic Resonance Imaging in Intracranial Aneurysms and Brain Arteriovenous Malformations

Over the last several years, the advent of intracranial high-resolution vessel wall magnetic resonance imaging (VW-MRI) has provided a new lens with which to view cerebrovascular disease that has not previously been available with conventional imaging. It has already fundamentally changed the way that steno-occlusive diseases are evaluated at many academic centers. This review focuses on current and emerging applications of intracranial high-resolution VW-MRI in the clinical evaluation of intracranial aneurysms and brain arteriovenous malformations. Examples are provided from our clinical practice.

Wall Imaging for Unilateral Intracranial Vertebral Artery Hypoplasia with Three-dimensional High-isotropic Resolution Magnetic Resonance Images

BACKGROUND

There are few studies for evaluating wall characteristics of intracranial vertebral artery hypoplasia (VAH). The aim of this study was to determine wall characteristics of VAH with three-dimensional volumetric isotropic turbo spin echo acquisition (3D VISTA) images and differentiate between acquired atherosclerotic stenosis and VAH.

METHODS

Thirty patients with suspicious VAH by luminograms were retrospectively enrolled between January 2014 and February 2015. The patients were classified as "acquired atherosclerotic stenosis" or "VAH" based on 3D VISTA images. The wall characteristics of VAH were assessed to determine the presence of atherosclerotic lesions, and the patients were classified into two subgroups (VAH with atherosclerosis and VAH with normal wall). Wall characteristics of basilar arteries and vertebral arteries were also assessed. The clinical and wall characteristics were compared between the two groups.

RESULTS

Five of 30 patients with suspicious VAH were finally diagnosed as acquired atherosclerotic stenosis by 3D VISTA images. 25 patients were finally diagnosed as VAH including 16 (64.00%) patients with atherosclerosis and 9 (36.00%) patients with normal wall. In the 16 patients with atherosclerosis, plaque was found in 9 patients, slight wall thickening in 6 patients, and thrombus and wall thickening in 1 patient. Compared with VAH patients with normal wall, VAH patients with atherosclerosis showed atherosclerotic basilar arteries and dominant vertebral arteries more frequently (P = 0.000).

CONCLUSIONS

Three-dimensional VISTA images enable differentiation between the acquired atherosclerotic stenosis and VAH. VAH was also prone to atherosclerotic processes.

Comparative analysis of general characteristics of ischemic stroke of BAD and non-BAD CISS subtypes

Based on the recently proposed Chinese ischemic stroke subclassification (CISS) system, intracranial branch atheromatous disease (BAD) is divided into large artery atherosclerosis (LAA) and penetrating artery disease (PAD). In the current retrospective analysis, we compared the general characteristics of BAD-LAA with BAD-PAD, BAD-LAA with non-BAD-LAA and BAD-PAD with non-BAD-PAD. The study included a total of 80 cases, including 45 cases of BAD and 35 cases of non-BAD. Subjects were classified using CISS system: BAD-LAA, BAD-PAD, non-BAD-LAA and non-BAD-PAD. In addition to analysis of general characteristics, the correlation between the factors and the two subtypes of BAD was evaluated. The number of cases included in the analysis was: 32 cases of BAD-LAA, 13 cases of BAD-PAD, 21 cases of non-BAD-LAA, and 14 cases of non-BAD-PAD. Diabetes mellitus affected more non-BAD-LAA patients than BAD-LAA patients (P=0.035). In comparison with non-BAD-PAD, patients with BAD-PAD were younger (P=0.040), had higher initial NIHSS score (P<0.001) and morbidity of ischemic heart disease (P=0.033). Within patients with BAD, the PAD subtype was associated with smoking (OR=0.043; P=0.011), higher low-density lipoprotein (OR=5.339; P=0.029), ischemic heart disease (OR=9.383; P=0.047) and diabetes mellitus (OR=12.59; P=0.020). It was concluded that large artery atherosclerosis was the primary mechanism of BAD. The general characteristics showed no significant differences between the CISS subtypes of LAA and PAD within BAD, as well as between the BAD and non-BAD within LAA subtype. Several differences between PAD subtypes of BAD and non-BAD were revealed.

High-Resolution Magnetic Resonance Imaging of Intracranial Vertebral Artery Dissecting Aneurysm for Planning of Endovascular Treatment

The equipment and techniques associated with magnetic resonance imaging (MRI) have rapidly evolved. The development of 3.0 Tesla MRI has enabled high-resolution imaging of the intracranial vessel wall. High-resolution MRI (HRMRI) can yield excellent visualization of both the arterial wall and lumen, thus facilitating the detection of the primary and secondary features of intracranial arterial dissection. In the present report, we describe the manner in which HRMRI affected our endovascular treatment planning strategy in 2 cases with unruptured intracranial vertebral artery dissection aneurysm. HRMRI provides further information about the vessel wall and the lumen of the unruptured intracranial vertebral artery dissecting aneurysm, which was treated by an endovascular approach in the 2 current cases.

Multicontrast High-Resolution Vessel Wall Magnetic Resonance Imaging and Its Value in Differentiating Intracranial Vasculopathic Processes

Background and Purpose—

Although studies have attempted to differentiate intracranial vascular disease using vessel wall magnetic resonance imaging (VWI), none have incorporated multicontrast imaging. This study uses T1- and T2-weighted VWI to differentiate intracranial vasculopathies.

Methods—

We retrospectively reviewed patients with clinically defined intracranial vasculopathies causing luminal stenosis/irregularity who underwent VWI studies. Two blinded experts evaluated T1 precontrast and postcontrast and T2-weighted VWI characteristics, including the pattern of wall thickening; presence, pattern, and intensity of postcontrast enhancement; and T2 signal characteristics.

Results—

Twenty-one cases of atherosclerosis (intracranial atherosclerotic disease [ICAD]), 4 of reversible cerebral vasoconstriction syndrome, and 4 of vasculitis were identified, with a total of 118 stenotic lesions (81 ICAD, 22 reversible cerebral vasoconstriction syndrome, and 15 vasculitic lesions). There was substantial to excellent inter-reader agreement for the assessment of lesional T2 hyperintensity ( κ =0.80), pattern of wall thickening ( κ =0.87), presence ( κ =0.90), pattern ( κ =0.73), and intensity ( κ =0.77) of enhancement. ICAD lesions were significantly more likely to have eccentric wall involvement (90.1%) than reversible cerebral vasoconstriction syndrome (8.2%; P <0.001) and vasculitic lesions (6.7%; P <0.001) and were also more likely to have T2 hyperintensity present than the other 2 vasculopathies (79% versus 0%; P <0.001). There were also significant differences in the presence, intensity, and pattern of enhancement between all lesion types. Combining T1 and T2 VWI increased the sensitivity of VWI in differentiating ICAD from other vasculopathies from 90.1% to 96.3%.

Conclusions—

Multicontrast VWI can be a complementary tool for intracranial vasculopathy differentiation, which often leads to more invasive workups when reversible cerebral vasoconstriction syndrome and vasculitis are in the differential diagnosis.

Imaging the intracranial atherosclerotic vessel wall using 7T MRI: initial comparison with histopathology

BACKGROUND AND PURPOSE

Several studies have attempted to characterize intracranial atherosclerotic plaques by using MR imaging sequences. However, dedicated validation of these sequences with histology has not yet been performed. The current study assessed the ability of ultra-high-resolution 7T MR imaging sequences with different image contrast weightings to image plaque components, by using histology as criterion standard.

MATERIALS AND METHODS

Five specimens of the circle of Wills were imaged at 7T with 0.11 × 0.11 mm in-plane-resolution proton attenuation-, T1-, T2-, and T2*-weighted sequences (through-plane resolution, 0.11-1 mm). Tissue samples from 13 fiducial-marked locations (per specimen) on MR imaging underwent histologic processing and atherosclerotic plaque classification. Reconstructed MR images were matched with histologic sections at corresponding locations.

RESULTS

Forty-four samples were available for subsequent evaluation of agreement or disagreement between plaque components and image contrast differences. Of samples, 52.3% (n = 23) showed no image contrast heterogeneity; this group comprised solely no lesions or early lesions. Of samples, 25.0% (n = 11, mostly advanced lesions) showed good correlation between the spatial organization of MR imaging heterogeneities and plaque components. Areas of foamy macrophages were generally seen as proton attenuation-, T2-, and T2*- hypointense areas, while areas of increased collagen content showed more ambiguous signal intensities. Five samples showed image-contrast heterogeneity without corresponding plaque components on histology; 5 other samples showed contrast heterogeneity based on intima-media artifacts.

CONCLUSIONS

MR imaging at 7T has the image contrast capable of identifying both focal intracranial vessel wall thickening and distinguishing areas of different signal intensities spatially corresponding to plaque components within more advanced atherosclerotic plaques.

What are the potential implications of identifying intracranial internal carotid artery atherosclerotic lesions on cone-beam computed tomography? A systematic review and illustrative case studies

PURPOSE

A systematic literature review was performed to examine the clinical implications of intracranial internal carotid artery calcific atherosclerotic lesions (IICACALs) detected at cone-beam computed tomographic (CBCT) examinations.

MATERIALS AND METHODS

The PubMed database was queried in 2 separate searches using the linked search terms non-contrast enhanced cone beam computed tomography and calcified intracranial vascular lesions and non-contrast enhanced computed tomography and calcified intracranial vascular lesions. Reviewed were all English-language articles using CBCT or CT imaging that enrolled neurologically asymptomatic and symptomatic patients. Excluded were studies describing patients with hemorrhagic stroke. Illustrative cases describing incidentally detected IICACALs on CBCT scans are provided.

RESULTS

Three articles described identification of IICACALs on CBCT scans of almost 1,500 dental patients. Two of these fully addressed the subject, with 1 noting that IICACALs were benign and another urging patient referral for further workup. Five non-contrast-enhanced CT studies were evaluated in detail; all confirmed IICACALs as a substantive risk marker of advanced stenotic disease in the cerebral circulation, central brain atrophy, concomitant advanced atherosclerotic disease in the cardiovascular circulation, and an indicator of future ischemic events. Five CBCT examinations showing IICACALs in the cavernous and ophthalmic segments are presented.

CONCLUSION

Few studies have denoted the importance of identifying IICACALs on CBCT scans. However, all non-contrast-enhanced CT studies emphasized the clinical significance of these lesions in relation to cerebral and cardiovascular disease. Therefore, IICACALs seen on CBCT and CT scans present the same risk and should prompt referral for further evaluation.

High-resolution MRI of intracranial atherosclerotic disease

Intracranial atherosclerotic disease (ICAD) causes up to 10% of all ischemic strokes, and the rate of recurrent vascular ischemic events is very high. Important predictors of vulnerability in atherosclerotic plaques include the degree of stenosis and the underlying plaque morphology. Vascular wall MRI can provide information about wall structures and atherosclerotic plaque components. High-resolution (HR)-MRI in ICAD poses a greater challenge in the neurologic fields, because a high in-plane resolution and a high signal-to-noise ratio are required for vessel wall imaging of ICAD. Until now, plaque imaging of ICAD has focused on assessing the presence of a plaque and evaluating the plaque load. Going forward, evaluation of plaque vulnerability through analysis of imaging characteristics will be a critical area of research. This review introduces the acquisition protocol for HR-MRI in ICAD and the current issues associated with imaging.