Clinical Implications of Basilar Artery Plaques in the Pontine Infarction with Normal Basilar Angiogram: A High-Resolution Magnetic Resonance Imaging Study

Small vessel disease burden and prognosis of recent subcortical ischaemic stroke differ by parent artery atherosclerosis

BACKGROUND AND PURPOSE

Parent artery atherosclerosis is an important aetiology of recent subcortical ischaemic stroke (RSIS). However, comparisons of RSIS with different degrees of parent artery atherosclerosis are lacking.

METHODS

Prospectively collected data from our multicentre cohort (all were tertiary centres) of the Stroke Imaging Package Study between 2015 and 2017 were retrospectively reviewed. The patients with RSIS defined as a single clinically relevant diffusion-weighted imaging positive lesion in the territory of lenticulostriate arteries were categorized into three subgroups: (1) normal middle cerebral artery (MCA) on magnetic resonance angiography and high-resolution magnetic resonance imaging (HR-MRI); (2) low-grade MCA atherosclerosis (normal or <50% stenosis on magnetic resonance angiography and with MCA plaques on HR-MRI); (3) steno-occlusive MCA atherosclerosis (stenosis ≥50% or occlusion). The primary outcome was 90-day functional dependence (modified Rankin Scale score >2). The clinical and imaging findings were compared between subgroups.

RESULTS

A total of 239 patients (median age 60.0 [52.0-67.0] years, 72% male) were enrolled, including 140 with normal MCA, 64 with low-grade MCA atherosclerosis and 35 with steno-occlusive MCA atherosclerosis. Patients with steno-occlusive MCA atherosclerosis had the largest infarct volume. Low-grade MCA atherosclerosis was independently associated with cerebral microbleeding, more severe perivascular spaces in basal ganglia and higher total cerebral small vessel disease burden. Low-grade MCA atherosclerosis was an independent determinant of 90-day functional dependence (odds ratio 3.897; 95% confidence interval 1.309-11.604).

CONCLUSIONS

Our study suggested RSIS with varying severity of parent artery atherosclerosis exhibits distinctive clinical and neuroimaging characteristics, with low-grade MCA atherosclerosis associating with higher cerebral small vessel disease burden and worse prognosis.

Culprit Plaques of Large Parent Arteries, Rather than Cerebral Small Vessel Disease, Contribute to Early Neurological Deterioration in Stroke Patients with Intracranial Branch Atheromatous Disease

INTRODUCTION

Intracranial branch atheromatous disease (BAD) has been applied to occlusions that occur at the origin of large caliber penetrating arteries due to the microatheromas or large parent artery plaques. This study aimed to explore the association between culprit plaques of large parent arteries, neuroimaging markers of cerebral small vessel disease (CSVD), and the risk of early neurological deterioration (END) in stroke patients with BAD.

METHODS

A total of 97 stroke patients with BAD in the vascular territories of the lenticulostriate arteries or paramedian pontine arteries, diagnosed using high-resolution magnetic resonance imaging, were prospectively recruited in this observational study. A culprit plaque in the middle cerebral artery was defined as the only arterial plaque on the ipsilateral side of an infarction visible on diffusion-weighted imaging. A culprit plaque in the basilar artery (BA) was identified when it was observed within the same axial slices of an infarction or on the adjacent upper or lower slice, whereas a plaque within the BA located in the ventral region was considered non-culprit. If more than one plaque was present in the same vascular territory, the most stenotic plaque was chosen for the analysis. Four CSVD neuroimaging markers, including white matter hyperintensity, lacunes, microbleeds, and enlarged perivascular spaces, were evaluated in accordance with the total CSVD score. The associations between neuroimaging features of lesions within large parent arteries, neuroimaging markers of CSVD, and the risk of END in stroke patients with BAD were investigated using logistic regression analysis.

RESULTS

END occurred in 41 stroke patients (42.27%) with BAD. The degree of large parent artery stenosis (p < 0.001), culprit plaques of large parent arteries (p < 0.001), and plaque burden (p < 0.001) were significantly different between the END and non-END groups in stroke patients with BAD. In logistic regression analysis, culprit plaques of large parent arteries (odds ratio, 32.258; 95% confidence interval, 4.140-251.346) were independently associated with the risk of END in stroke patients with BAD.

CONCLUSIONS

Culprit plaques of large parent arteries could predict the risk of END in stroke patients with BAD. These results suggest that lesions in the large parent arteries, rather than damage to the cerebral small vessels, contribute to END in stroke patients with BAD.

Characterization of non-stenotic plaques in intracranial arteries with multi-contrast, multi-planar vessel wall image analysis

OBJECTIVES

Non-stenotic plaques have been observed in intracranial arteries but are less understood compared to those in coronary and carotid arteries. We sought to compare plaque distribution and morphology between stenotic and non-stenotic intracranial plaques with MR vessel wall imaging (VWI) and quantitative image analysis.

MATERIALS AND METHODS

Twenty-four patients with intracranial arterial stenosis or luminal irregularity on clinical imaging were scanned with a multi-contrast VWI protocol. Plaques were detected as focal wall thickening on co-registered multiplanar reformats of multi-contrast VWI, with assessment of the location and morphology. TOF-MRA was independently reviewed for any appreciable stenosis using the WAISD criteria.

RESULTS

Across 504 arterial segments, a total of 80 plaques were detected, including 23 (29%) with stenosis on TOF-MRA, 56 (70%) without, and 1 (1%) not covered by TOF-MRA. Plaques involving the ICA were more likely to be non-stenotic than those involving other segments (80% versus 55%, p = 0.030) whereas the basilar artery (40%) and PCA (33%) had the lowest proportions of non-stenotic plaques. Maximum wall thickness, indicative of plaque burden, correlated poorly with degree of stenosis (p = 0.10) and overlapped substantially between stenotic and non-stenotic plaques (1.9 [1.5, 2.4] versus 2.0 [1.5, 2.2] mm, p = 0.074).

CONCLUSIONS

Intracranial plaques without appreciable stenosis on TOF-MRA represent a large proportion of lesions throughout arterial segments but disproportionately affect the ICA. Morphological characterization of plaques with and without stenosis shows that luminal stenosis is a poor indicator of the underlying burden of intracranial atherosclerosis.

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

Black blood vessel wall MRI to identify vulnerable atherosclerotic plaque in a non-stenotic intracranial vertebral artery as a cause of acute ischaemia

Conventional neuroimaging techniques for investigating the cause of stroke are mainly centred on investigating luminal stenosis. The pathophysiology of intracranial atherosclerotic disease (ICAD) and stroke is complex and extends beyond just vessel narrowing. The concept of the vulnerable atherosclerotic plaque, that can result in acute coronary syndromes, has been well described in the cardiac literature^1,2although this concept is less well accepted among stroke physicians. We describe a case of a 61-year-old male with acute neurological sequelae from a non-stenotic atherosclerotic plaque of the intracranial vertebral artery. This case report describes the additional use of vessel wall MRI techniques to aid the radiologist in identifying such vulnerable lesions and therefore helping to tailor management and prevent further clinical deterioration.

Imaging endpoints of intracranial atherosclerosis using vessel wall MR imaging: a systematic review

PURPOSE

The vessel wall MR imaging (VWI) literature was systematically reviewed to assess the criteria and measurement methods of VWI-related imaging endpoints for symptomatic intracranial plaque in patients with ischemic events.

METHODS

PubMed, Scopus, Web of Science, EMBASE, and Cochrane databases were searched up to October 2019. Two independent reviewers extracted data from 47 studies. A modified Guideline for Reporting Reliability and Agreement Studies was used to assess completeness of reporting.

RESULTS

The specific VWI-pulse sequence used to identify plaque was reported in 51% of studies. A VWI-based criterion to define plaque was reported in 38% of studies. A definition for culprit plaque was reported in 40% of studies. Frequently scored qualitative imaging endpoints were plaque quadrant (21%) and enhancement (21%). Frequently measured quantitative imaging endpoints were stenosis (19%), lumen area (15%), and remodeling index (14%). Reproducibility for all endpoints ranged from good to excellent (range: ICC_{T1 hyperintensity} = 0.451 to ICC_stenosis = 0.983). However, rater specialty and years of experience varied among studies.

CONCLUSIONS

Investigators are using different criteria to identify and measure VWI-imaging endpoints for culprit intracranial plaque. Early awareness of these differences to address methods of acquisition and measurement will help focus research resources and efforts in technique optimization and measurement reproducibility. Consensual definitions to detect plaque will be important to develop automatic lesion detection tools particularly in the era of radiomics.

Assessment of Intracranial Atherosclerotic Plaques Using 3D Black-Blood MRI: Comparison With 3D Time-of-Flight MRA and DSA

BACKGROUND

Noninvasive assessment of intracranial stenosis is important to manage ischemic stroke patients. However, few previous studies have compared 3D black-blood MRI with 3D time-of-flight (TOF), magnetic resonance angiography (MRA), and digital subtraction angiography (DSA) for intracranial artery plaque assessment.

PURPOSE

To compare 3D black-blood MRI and 3D TOF-MRA, using DSA as the reference standard for intracranial stenosis and atherosclerotic plaque assessment in patients with posterior circulation stroke or transient ischemic attacks (TIAs).

STUDY TYPE

Prospective, cohort study.

POPULATION

One hundred and one patients with posterior circulation stroke and/or TIA (age 63 ± 10 years, 84 male) who underwent DSA and MRI within 4 weeks of each other.

FIELD STRENGTH/SEQUENCE

3D fast-spin-echo MRI for intracranial vessel wall imaging (IVWI) and 3D TOF at 3T.

ASSESSMENT

Two radiologists independently measured the degree of stenosis on 3D IVWI and TOF, using DSA as a reference. Plaque enhancement was recorded when the plaque was stenosis-free on DSA.

STATISTICAL TESTS

Shapiro-Wilk's test, Student's t-test, Mann-Whitney U-test, Spearman correlation, Bland-Altman analysis, and interclass correlation coefficient (ICC).

RESULTS

A total of 238 intracranial plaques (203 posterior, 35 anterior) were included. 3D IVWI showed better agreement with DSA in measuring stenosis than TOF (ICC = 0.89 vs. 0.64). 3D IVWI had higher sensitivity and specificity for detecting stenosis >50% and stenosis >75% than TOF, using DSA as the standard. TOF significantly overestimated the degree of stenosis compared to DSA (65 ± 19% vs. 51 ± 15%, P < 0.001). DSA did not observe 62 nonstenotic plaques (26.1%) that were shown only on 3D IVWI, in which 36 plaques (58.1%) showed contrast enhancement. The interreader agreement for measuring stenosis were excellent, with ICCs >0.90 for all three modalities.

DATA CONCLUSION

3D black-blood MRI is accurate and reproducible for quantifying intracranial artery stenosis compared with DSA, and performs better than 3D TOF. As compared to DSA, it detects more nonstenotic plaques. Level of Evidence 1 Technical Efficacy Stage 2 J. MAGN. RESON. IMAGING 2021;53:469-478.

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.