Intracranial vessel wall imaging for evaluation of steno-occlusive diseases and intracranial aneurysms

Incidental vascular findings on brain magnetic resonance angiography

Given the ever-increasing utilization of magnetic resonance angiography, incidental vascular findings are increasingly discovered on exams performed for unconnected indications. Some incidental lesions represent pathology and require further intervention and surveillance, such as aneurysm, certain vascular malformations, and arterial stenoses or occlusions. Others are benign or represent normal anatomic variation, and may warrant description, but not further work-up. This review describes the most commonly encountered incidental findings on magnetic resonance angiography, their prevalence, clinical implications, and any available management recommendations.

Advanced cross-sectional imaging of cerebral aneurysms

While the rupture rate of cerebral aneurysms is only 1% per year, ruptured aneurysms are associated with significant morbidity and mortality, while aneurysm treatments have their own associated risk of morbidity and mortality. Conventional markers for aneurysm rupture include patient-specific and aneurysm-specific characteristics, with the development of scoring systems to better assess rupture risk. These scores, however, rely heavily on aneurysm size, and their accuracy in assessing risk in smaller aneurysms is limited. While the individual risk of rupture of small aneurysms is low, due to their sheer number, the largest proportion of ruptured aneurysms are small aneurysms. Conventional imaging techniques are valuable in characterizing aneurysm morphology; however, advanced imaging techniques assessing the presence of inflammatory changes within the aneurysm wall, hemodynamic characteristics of blood flow within aneurysm sacs, and imaging visualization of irregular aneurysm wall motion have been used to further determine aneurysm instability that otherwise cannot be characterized by conventional imaging techniques. The current manuscript reviews conventional imaging techniques and their value and limitations in cerebral aneurysm characterization, and evaluates the applications, value and limitations of advanced aneurysm imaging and post-processing techniques including intracranial vessel wall MRA, 4D-flow, 4D-CTA, and computational fluid dynamic simulations.

Vessel Wall MR Imaging in the Pediatric Head and Neck

Vessel wall MR imaging (VWI) is a technique that progressively has gained traction in clinical diagnostic applications for evaluation of intracranial and extracranial vasculopathies, with increasing use in pediatric populations. The technique has shown promise in detection, differentiation, and characterization of both inflammatory and noninflammatory vasculopathies. In this article, optimal techniques for intracranial and extracranial VWI as well as applications and value for pediatric vascular disease evaluation are discussed.

Cardiovascular Risk Factors Affect Specific Segments of the Intracranial Vasculature in High-Resolution (HR) Vessel Wall Imaging (VWI)

OBJECTIVES

Luminal-based imaging have identified different risk factors for extracranial and intracranial atherosclerosis (ICAS), but these techniques are known to underestimate the true extent of the disease. High-resolution (HR) vessel wall imaging (VWI) has recently gained recognition as a valuable tool in the assessment of ICAS. The aim of this study is to determine the association between cardiovascular risk factors and specific intracranial vessel segment involvement using HR-VWI.

MATERIALS AND METHODS

From January 2017 to January 2020, consecutive patients ≥ 18 years-old undergoing HR-VWI of the brain were identified. Patients with history of primary or secondary vasculitis, reversible cerebral vasoconstriction syndrome, or moya-moya were excluded. The presence of vessel wall thickening and enhancement were assessed in the perpendicular plane for each vessel segment by two neuroradiologists. Univariate and multivariate analyses were performed to assess associations between imaging findings and cardiovascular risk factors. Interrater reliability was calculated.

RESULTS

Seventy-one patients (39 men; mean age: 55.9 years) were included. Vessel wall enhancement was seen in 39/71 (55%). A total number of 105 vessel segments demonstrated abnormal enhancement and 79/105 (75%) had an eccentric pattern. Eccentric vessel wall enhancement was independently associated with age >65 years-old in the ICA (OR 9.0, CI 2.1 - 38.2, p < 0.01) and proximal MCA (OR 4.0, CI 1.2 - 13.2, p = 0.02), and with hyperlipidemia in the posterior circulation (OR 44.0, CI2.9-661.0, p<0.01).

CONCLUSION

There is a significant association between eccentric vessel wall enhancement of the ICA and proximal MCA in patients with age > 65; and of the proximal posterior circulation (basilar - PCA1) with hyperlipidemia.

Diagnosis and follow-up evaluation of central nervous system vasculitis: an evaluation of vessel-wall MRI findings

Objective

To approach the clinical value of MRI with vessel wall imaging (VWI) in patients with central nervous system vasculitis (CNSV), we analyzed patterns of VWI findings both at the time of initial presentation and during follow-up.

Methods

Stenoocclusive lesions, vessel-wall contrast enhancement (VW-CE) and diffusion-restricted lesions were analyzed in patients with a diagnosis of CNSV. On available VWI follow-up, progression, regression or stability of VW-CE were evaluated and correlated with the clinical status.

Results

Of the 45 patients included, 28 exhibited stenoses visible on MR angiography (MRA-positive) while 17 had no stenosis (MRA-negative). VW-CE was found in 2/17 MRA-negative and all MRA-positive patients (p < 0.05). 79.1% (53/67) of stenoses showed VW-CE. VW-CE was concentric in 88.3% and eccentric in 11.7% of cases. Diffusion-restricted lesions were found more frequently in relation to stenoses with VW-CE than without VW-CE (p < 0.05). 48 VW-CE lesions in 23 patients were followed over a median time of 239.5 days. 13 VW-CE lesions (27.1%) resolved completely, 14 (29.2%) showed partial regression, 17 (35.4%) remained stable and 4 (8.3%) progressed. 22/23 patients received immunosuppressive therapy for the duration of follow-up. Patients with stable or progressive VW-CE were more likely (p < 0.05) to have a relapse (14/30 cases) than patients with partial or complete regression of VW-CE (5/25 cases).

Conclusion

Concentric VW-CE is a common finding in medium/large-sized vessel CNSV. VW-CE might represent active inflammation in certain situations. However, follow-up VWI findings proved ambiguous as persisting VW-CE despite immunosuppressive therapy and clinical remission was a frequent finding.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10683-7.

Black blood imaging of intracranial vessel walls

Traditional vascular imaging focuses on non-invasive cross-sectional imaging to assess luminal morphology; however, the vessel wall itself may be specifically involved in many diseases. Newer pulse sequences, and particularly black blood MRI of intracranial vessels, have brought a paradigm shift in understanding the pathophysiology of many vasculopathies. Black blood MRI of intracranial vessel walls can help in a range of pathologies with differing pathophysiology, including intracranial atherosclerosis, aneurysms, vasculitis and vasculopathy, moyamoya disease, dissection and vertebrobasilar hypoplasia. This review highlights how vessel wall imaging can contribute to the clinical diagnosis and management of patients with intracranial vascular pathology.

Contemporary and emerging magnetic resonance imaging methods for evaluation of moyamoya disease

Numerous recent technological advances offer the potential to substantially enhance the MRI evaluation of moyamoya disease (MMD). These include high-resolution volumetric imaging, high-resolution vessel wall characterization, improved cerebral angiographic and perfusion techniques, high-field imaging, fast scanning methods, and artificial intelligence. This review discusses the current state-of-the-art MRI applications in these realms, emphasizing key imaging findings, clinical utility, and areas that will benefit from further investigation. Although these techniques may apply to imaging of a wide array of neurovascular or other neurological conditions, consideration of their application to MMD is useful given the comprehensive multidimensional MRI assessment used to evaluate MMD. These MRI techniques span from basic cross-sectional to advanced functional sequences, both qualitative and quantitative.The aim of this review was to provide a comprehensive summary and analysis of current key relevant literature of advanced MRI techniques for the evaluation of MMD with image-rich case examples. These imaging methods can aid clinical characterization, help direct treatment, assist in the evaluation of treatment response, and potentially improve the understanding of the pathophysiology of MMD.

Utility of intracranial high-resolution vessel wall magnetic resonance imaging in differentiating intracranial vasculopathic diseases causing ischemic stroke

PURPOSE

High-resolution vessel wall imaging (HRVWI) by MRI is a novel noninvasive imaging tool which provides direct information regarding vessel wall pathologies. The utility of HRVWI in differentiating various intracranial vasculopathies among ischemic stroke is still evolving.

METHODS

Consecutive ischemic stroke/TIA patients within 2 weeks of symptom onset between January 2016 to December 2017, with symptomatic vessel stenosis of 50% or more/occlusion on baseline luminal imaging studies were recruited into the study. Stroke subtypes were classified as per TOAST classification initially on the basis of luminal imaging findings alone and subsequently after incorporation of HRVWI findings as well.

RESULTS

Forty-nine subjects were recruited into the study. The median age of the population was 42 years (range 11 to 75) with 69% being males. Incorporation of HRVWI findings classified 38.8% subjects into intracranial atherosclerotic disease (ICAD), 32.6% as stroke of other determined aetiology (ODE) (inflammatory vasculopathy [IVas] being the major subgroup [81.2%]) and 28.6% into stroke of undetermined aetiology (UE). HRVWI enabled a diagnostic reclassification in an additional 47.3% among the baseline UE category as against luminal imaging findings alone. ICAD was likelier to have eccentric vessel wall thickening, eccentric vessel wall enhancement and T2 juxtaluminal hyperintensity with surrounding hypointensity (P < 0.001), while IVas were more likely to exhibit concentric vessel wall thickening with homogenous enhancement (P < 0.001).

CONCLUSION

HRVWI is a useful noninvasive adjunctive tool in the diagnostic evaluation of intracranial vasculopathies, with maximum benefit in ICAD and IVas subtypes.

Progress in moyamoya disease

Moyamoya disease is characterized by progressive stenosis or occlusion of the intracranial portion of the internal carotid artery and their proximal branches, resulting in ischemic or hemorrhagic stroke with high rate of disability and even death. So far, available treatment strategies are quite limited, and novel intervention method is being explored. This review encapsulates current advances of moyamoya disease on the aspects of epidemiology, etiology, clinical features, imaging diagnosis and treatment. In addition, we also bring forward our conjecture, which needs to be testified by future research.

Risk prediction of cerebrovascular events with carotid plaque magneitc resonance analysis: A meta-analysis

BACKGROUND AND PURPOSE

It is not conclusive that magnetic resonance (MR)-based carotid atherosclerotic plaque assessment identifies high-risk features associated with cerebrovascular events. We aimed to systematically summarize the association of MR imaging (MRI)-determined intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and thinning/rupture of the fibrous cap (TRFC) with subsequent ischemic events.

MATERIALS AND METHODS

We performed a comprehensive literature search evaluating the association of MRI-based carotid plaque composition with ischemic outcomes. We included cohort studies examining IPH, LRNC, or TRFC with mean follow-up of≥6 months and an outcome measure of ipsilateral ischemic events. A meta-analysis was done according to the Cochrane guideline.

RESULTS

We identified 13 studies including 1.150 patients and 1.208 analyzed carotid arteries, with mean follow-up of 21.1 months. The hazard ratios (HR) for IPH, LRNC, and TRFC as predictors of subsequent ischemic events were 4.41 (95% CI: 2.87, 6.79), 3.00 (95% CI: 1.51, 5.95), and 5.94 (95% CI: 2.66, 13.28), respectively. The predictive value of carotid plaque MRI for ischemic events was acceptable, with sensitivity of 0.80 (95% CI: 0.66, 0.90) and specificity of 0.63 (95% CI: 0.57, 0.68). However, it was limited to confirm or exclude future ischemic events in clinical context, with positive likelihood ratio (LR) of 2.2 (95% CI: 1.9, 2.5) and negative LR of 0.31 (95% CI: 0.18, 0.55). No statistically significant heterogeneity or publication bias was observed.

CONCLUSION

The presence of IPH, LRNC, and TRFC determined by MRI is associated with increased risk of future ischemic events, but its predictive value is moderate and should not be used for confirmation or exclusion of future ischemic events in clinical context.

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.