Brain imaging biomarkers of carotid artery disease

Increased Risk of Recurrent Stroke in Symptomatic Large Vessel Disease With Impaired BOLD Cerebrovascular Reactivity

BACKGROUND

Impaired cerebrovascular reactivity (CVR) has been correlated with recurrent ischemic stroke. However, for clinical purposes, most CVR techniques are rather complex, time-consuming, and lack validation for quantitative measurements. The recent adaptation of a standardized hypercapnic stimulus in combination with a blood-oxygenation-level-dependent (BOLD) magnetic resonance imaging signal as a surrogate for cerebral blood flow offers a potential universally comparable CVR assessment. We investigated the association between impaired BOLD-CVR and risk for recurrent ischemic events.

METHODS

We conducted a retrospective analysis of patients with symptomatic cerebrovascular large vessel disease who had undergone a prospective hypercapnic-challenged BOLD-CVR protocol at a single tertiary stroke referral center between June 2014 and April 2020. These patients were followed up for recurrent acute ischemic events for up to 3 years. BOLD-CVR (%BOLD signal change per mm Hg CO2) was calculated on a voxel-by-voxel basis. Impaired BOLD-CVR of the affected (ipsilateral to the vascular pathology) hemisphere was defined as an average BOLD-CVR, falling 2 SD below the mean BOLD-CVR of the right hemisphere in a healthy age-matched reference cohort (n=20). Using a multivariate Cox proportional hazards model, the association between impaired BOLD-CVR and ischemic stroke recurrence was assessed and Kaplan-Meier survival curves to visualize the acute ischemic stroke event rate.

RESULTS

Of 130 eligible patients, 28 experienced recurrent strokes (median, 85 days, interquartile range, 5-166 days). Risk factors associated with an increased recurrent stroke rate included impaired BOLD-CVR, a history of atrial fibrillation, and heart insufficiency. After adjusting for sex, age group, and atrial fibrillation, impaired BOLD-CVR exhibited a hazard ratio of 10.73 (95% CI, 4.14-27.81; P<0.001) for recurrent ischemic stroke.

CONCLUSIONS

Among patients with symptomatic cerebrovascular large vessel disease, those exhibiting impaired BOLD-CVR in the affected hemisphere had a 10.7-fold higher risk of recurrent ischemic stroke events compared with individuals with nonimpaired BOLD-CVR.

Associations of Arterial Thickness, Stiffness, and Blood Pressure With Brain Morphology in Early Adolescence: A Prospective Population-Based Study

BACKGROUND

Arterial wall thickness and stiffness, and high blood pressure have been repeatedly associated with poorer brain health. However, previous studies largely focused on mid- or late-life stages. It is unknown whether any arterial health-related brain changes may be observable already in adolescence.

METHODS

We examined whether (1) carotid intima-media thickness, (2) carotid distensibility, and (3) systolic blood pressure and diastolic blood pressure, measured at the age of 10 years, were associated with brain volumes and white matter microstructure (ie, fractional anisotropy and mean diffusivity) at the age of 14 years. In addition to cross-sectional analyses, we explored associations with longitudinal change in each brain outcome from 10 to 14 years. Analyses were based on 5341 children from the Generation R Study.

RESULTS

Higher diastolic blood pressure was associated with lower total brain volume (β, -0.04 [95% CI, -0.07 to -0.01]) and gray matter volume (β, -0.04 [95% CI, -0.07 to -0.01]) at the age of 14 years, with stronger associations in higher diastolic blood pressure ranges. Similar associations emerged between systolic blood pressure and brain volumes, but these were no longer significant after adjusting for birth weight. No associations were observed between blood pressure and white matter microstructure or between carotid intima-media thickness or distensibility and brain morphology.

CONCLUSIONS

Arterial blood pressure, but not intima-media thickness and distensibility, is associated with structural neuroimaging markers in early adolescence. Volumetric measures may be more sensitive to these early arterial health differences compared with microstructural properties of the white matter, but further studies are needed to confirm these results and assess potential causal mechanisms.

Diagnostic accuracy of superb microvascular imaging for detecting intraplaque neovascularization: a systematic review and meta-analysis

Background

Atherosclerotic plaques can cause carotid artery stenosis, and "vulnerable plaques" can even lead to ischemic stroke. The objective of this study was to assess the accuracy of superb microvascular imaging (SMI) for the detection of carotid intraplaque neovascularization (IPN) in patients with atherosclerotic plaques.

Methods

We searched the Cochrane Library, Embase, Medline, and Wanfang databases until January 17, 2023. We included original studies with information on diagnostic accuracy of SMI for the evaluation of carotid IPN. The primary outcome was the accuracy of SMI for detecting carotid IPN. A meta-analysis was performed to estimate the accuracy of each parameter. We used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) to assess the risk of bias for each included article. Meta-regression was performed to determine items that may have contributed to heterogeneity in the sensitivity or specificity of the test.

Results

This meta-analysis included 20 studies with 1,589 carotid plaques in 1,225 patients. The analysis showed a sensitivity and specificity of SMI for detecting IPN of 93% [95% confidence interval (CI): 87-96%] and 80% (95% CI: 71-87%), respectively. The risk of bias across the QUADAS-2 domains was low. Only the proportion of dyslipidemia influenced the estimates of sensitivity and specificity.

Conclusions

This review suggests that SMI has a good diagnostic performance for detecting carotid IPN. The very high sensitivity with excellent post-test probability indicated that SMI can be recommended to screen for carotid IPN among patients with carotid plaques.

Patients with Carotid Intraplaque Hemorrhage Have Higher Incidence of Cerebral Microbleeds

AIMS

Carotid intraplaque hemorrhage (IPH) is considered a marker of plaque vulnerability. Cerebral microbleeds (CMBs) are recognized on magnetic resonance imaging (MRI) in patients with cerebrovascular disease. Any connection between carotid IPH and CMBs remains scantly investigated. This study aimed to determine whether the histologic evidence of carotid IPH is related to CMBs.

METHODS

We retrospectively enrolled 101 consecutive patients undergoing carotid endarterectomy with symptomatic (ischemic stroke, TIA, and amaurosis fugax) or asymptomatic ipsilateral carotid artery disease. The presence and the extent (%) of IPH were identified on carotid plaques stained with Movat Pentachrome. CMBs were localized on T2*-weighted gradient-recalled echo or susceptibility-weighted imaging sequence on brain MRI before surgery. The degree of carotid stenosis was measured by neck CTA.

RESULTS

IPH was identified in 57 (56.4%) patients, and CMBs were found in 24 (23.7%) patients. CMBs were more commonly observed in patients with carotid IPH compared to those without [19 (33.3%) vs 5 (11.4%); p=0.010]. The carotid IPH extent was significantly higher in patients with CMBs than in those without [9.0 % (2.8-27.1%) vs 0.9% (0.0-13.9%); p=0.004] and was associated with the number of CMBs (p=0.004). Logistic regression analysis demonstrated an independent association between carotid IPH extent and the presence of CMBs [OR 1.051 (95% CI 1.012-1.090); p=0.009]. Additionally, patients with CMBs had a lower degree of ipsilateral carotid stenosis compared to those without [40% (35-65%) vs 70% (50-80%); p=0.049].

CONCLUSIONS

CMBs may be potential markers of the ongoing process of carotid IPH, especially in those with nonobstructive plaques.

Hemodynamic MRI parameters to predict asymptomatic unilateral carotid artery stenosis with random forest machine learning

BACKGROUND

Internal carotid artery stenosis (ICAS) can cause stroke and cognitive decline. Associated hemodynamic impairments, which are most pronounced within individual watershed areas (iWSA) between vascular territories, can be assessed with hemodynamic-oxygenation-sensitive MRI and may help to detect severely affected patients. We aimed to identify the most sensitive parameters and volumes of interest (VOI) to predict high-grade ICAS with random forest machine learning. We hypothesized an increased predictive ability considering iWSAs and a decreased cognitive performance in correctly classified patients.

MATERIALS AND METHODS

Twenty-four patients with asymptomatic, unilateral, high-grade carotid artery stenosis and 24 age-matched healthy controls underwent MRI comprising pseudo-continuous arterial spin labeling (pCASL), breath-holding functional MRI (BH-fMRI), dynamic susceptibility contrast (DSC), T2 and T2* mapping, MPRAGE and FLAIR. Quantitative maps of eight perfusion, oxygenation and microvascular parameters were obtained. Mean values of respective parameters within and outside of iWSAs split into gray (GM) and white matter (WM) were calculated for both hemispheres and for interhemispheric differences resulting in 96 features. Random forest classifiers were trained on whole GM/WM VOIs, VOIs considering iWSAs and with additional feature selection, respectively.

RESULTS

The most sensitive features in decreasing order were time-to-peak (TTP), cerebral blood flow (CBF) and cerebral vascular reactivity (CVR), all of these inside of iWSAs. Applying iWSAs combined with feature selection yielded significantly higher receiver operating characteristics areas under the curve (AUC) than whole GM/WM VOIs (AUC: 0.84 vs. 0.90, p = 0.039). Correctly predicted patients presented with worse cognitive performances than frequently misclassified patients (Trail-making-test B: 152.5s vs. 94.4s, p = 0.034).

CONCLUSION

Random forest classifiers trained on multiparametric MRI data allow identification of the most relevant parameters and VOIs to predict ICAS, which may improve personalized treatments.

Advances in Noninvasive Carotid Wall Imaging with Ultrasound: A Narrative Review

Carotid atherosclerosis is a major cause for stroke, with significant associated disease burden morbidity and mortality in Western societies. Diagnosis, grading and follow-up of carotid atherosclerotic disease relies on imaging, specifically ultrasound (US) as the initial modality of choice. Traditionally, the degree of carotid lumen stenosis was considered the sole risk factor to predict brain ischemia. However, modern research has shown that a variety of other imaging biomarkers, such as plaque echogenicity, surface morphology, intraplaque neovascularization and vasa vasorum contribute to the risk for rupture of carotid atheromas with subsequent cerebrovascular events. Furthermore, the majority of embolic strokes of undetermined origin are probably arteriogenic and are associated with nonstenosing atheromas. Therefore, a state-of-the-art US scan of the carotid arteries should take advantage of recent technical developments and should provide detailed information about potential thrombogenic (/) and emboligenic arterial wall features. This manuscript reviews recent advances in ultrasonographic assessment of vulnerable carotid atherosclerotic plaques and highlights the fields of future development in multiparametric arterial wall imaging, in an attempt to convey the most important take-home messages for clinicians performing carotid ultrasound.

Identification of Biomarkers of Autophagy-Related Genes Between Early and Advanced Carotid Atherosclerosis

Background

Accumulating evidence demonstrates that autophagy is important in inhibiting inflammation and cholesterol efflux. It suggested the autophagy may be a treatment of atherosclerosis. Thus, we screened autophagy-related mRNA to explore their mechanism of scientific basis for early diagnosis and therapy of atherosclerosis.

Methods

The GSE28829 datasets were assessed to analyze differentially expressed genes by GEO2R. And autophagy-related hub genes were identified by HADb. The biological function of autophagy-related DEmRNAs was examined by Metascape. The construction of a protein–protein network was explored by String. Cytohubba was utilized to screen hub genes. Analysis of DEmiRNA-mRNA pairs was executed by DIANA microT-CDS database. Finally, correlation analysis was carried out to identify the relationship between DEARGs and clinical and prognostic factors.

Results

A number of 1087 DEGs and 19 autophagy-related DEmRNAs were identified in advanced carotid atherosclerotic plaque compared with the early. The biological function containing development and growth was enriched. Moreover, we screened the top hub nodes with the highest degrees. MicroRNAs (miRNAs) are confirmed to participate in genesis and progression of atherosclerosis, so we further analyzed the miRNA–mRNA regulatory network genes with four hub genes to explore their potential mechanism in atherosclerosis. Then, we revealed co-expression of four key genes CTSB, ITGB1, CXCR4, TNFSF10 and autophagy-related genes. As for the clinical factors, hypertension factor showed higher expression of ITGB1. The probability of coronary heart disease factor was significantly increased with high expression of CTSB and CXCR4, as well as low expression of ITGB1 and TNFSF10. Diabetes factor tended to express distinguished levels of CTSB and ITGB1. TNFSF10 was highly expressed in both hyperlipidemia and ischemic stroke factor.

Conclusion

CTSB, ITGB1, CXCR4 and TNFSF10 may be critical in atherosclerosis development and were thought to be potential diagnostic biomarkers for atherosclerosis.

Diagnostic and prognostic significance of lncRNA SOX2-OT in patients with carotid atherosclerosis

Background

This paper aimed to analyze IncRNA SOX2-OT expression in patients with carotid atherosclerosis and to elucidate the predictive significance of SOX2-OT on carotid atherosclerosis.

Methods

The levels of SOX2-OT from 185 participants were tested. The relationship between CIMT levels and SOX2-OT expression was examined by Pearson analysis. The clinical value of SOX2-OT was investigated by the ROC curve, K–M curve, and COX regression analysis. The comparison of SOX2-OT expression between patients with good prognosis and poor prognosis was also performed.

Results

The expression of SOX2-OT was augmented in the patients with carotid atherosclerosis and was correlated with the level of CIMT. The high level of SOX2-OT might be a risk factor for carotid atherosclerosis. An enhancement of SOX2-OT expression was found in patients with poor prognosis. SOX2-OT might be an independent prognostic biomarker.

Conclusions

SOX2-OT was upregulated in patients with carotid atherosclerosis and might be a predictive indicator in the progression of carotid atherosclerosis.

Extracranial carotid atherosclerosis is associated with increased neurofibrillary tangle accumulation

OBJECTIVE

We sought to determine whether extracranial carotid atherosclerotic disease (ECAD) is associated with increased key neurodegenerative pathology such as neurofibrillary tangle (NFT), beta-amyloid plaque, or cerebral amyloid angiopathy (CAA) accumulation, findings associated with Alzheimer's disease (AD) and other dementias.

METHODS

Our prospective, longitudinal, clinicopathologic study, the AZSAND (Arizona study of aging and neurodegenerative disorders) and Brain and Body Donation Program, recorded the presence or absence of clinically diagnosed ECAD and performed semiquantitative density estimates of NFT, beta-amyloid plaque, and CAA at death. After adjusting for potential confounding factors determined by logistic regression analysis, histopathology density scores were evaluated in individuals with ECAD (n = 66) and those without ECAD (n = 125).

RESULTS

We found that the presence of ECAD was associated with a 21% greater NFT burden at death compared with no ECAD (P = .02). Anatomically, an increased NFT burden was seen throughout the brain regions evaluated but was significant in the temporal lobe (P < .05) and entorhinal cortex (P = .02). In addition, we found that subjects who had undergone carotid endarterectomy (CEA), the surgical treatment of ECAD (n = 32), had decreased NFT densities compared with those with ECAD who had not undergone CEA (n = 66; P = .04). In contrast to NFT, ECAD was not associated with beta-amyloid plaques or CAA density.

CONCLUSIONS

These findings indicate that ECAD is associated with the NFT burden in the temporal lobe and entorhinal cortex, which has clinical significance for AD and non-AD dementias and cognitive dysfunction. Further understanding of whether ECAD increases the risk of neurodegenerative brain changes is highly relevant because ECAD is a treatable disease that has not, otherwise, been evaluated for nor specifically treated as a dementia risk factor.

Cerebral Small Vessel Disease Burden Related to Carotid Intraplaque Hemorrhage Serves as an Imaging Marker for Clinical Symptoms in Carotid Stenosis

Objectives: In patients with carotid stenosis, to investigate the relationship between carotid intraplaque hemorrhage (IPH) and total burden of cerebral small vessel disease (CSVD) and preliminarily explore whether the total CSVD burden as an imaging marker can distinguish the severity of clinical symptoms. Methods: A total of 108 patients (the mean age was 66 ± 7 years, and 85.2% were male) with unilateral carotid stenosis ≥50% underwent brain MRI and high-resolution MRI for carotid plaque characterization. The total burden of CSVD was calculated by accumulating one point according to the presence or severity of each of the four MRI markers: white matter hyperintensities, lacunes, perivascular spaces, and cerebral microbleeds. Recent clinical symptoms including transient ischemic attack, amaurosis fugax, and ischemic stroke were recorded. The association between intraplaque hemorrhage (IPH) and total CSVD burden was examined adjusted for other risk factors. The symmetry of CSVD burdens between the ipsilateral and contralateral hemispheres of IPH was tested. Imaging features (CSVD score, IPH, degree of stenosis, and completeness of the circle of Willis) were correlated with clinical symptoms by Kruskal-Wallis H test, Chi-square test, and Fisher's exact test. Results: Multivariable logistic regression analysis showed that IPH (OR = 2.98, 95% CI [1.39, 6.40], p = 0.005) was independently associated with a higher CSVD score. The presence of unilateral IPH was associated with the inter-hemispheric CSVD score difference (p = 0.004). Patients with stroke had a higher ipsilateral CSVD score than asymptomatic patients (p = 0.004) and those with transient ischemic attack/amaurosis fugax (p = 0.008). The statistical difference was marginally significant between symptoms and IPH (p = 0.057). No statistical difference was found between the symptoms and degree of stenosis and the completeness of the circle of Willis (p > 0.05). Conclusions: Carotid IPH is associated with an elevated total burden of CSVD in patients with carotid stenosis. Compared with the degree of stenosis, primary collaterals, and IPH, the total CSVD score might be a more effective imaging marker linked with clinical symptoms.

Quantitative susceptibility mapping of carotid arterial tissue ex vivo: Assessing sensitivity to vessel microstructural composition

PURPOSE

To characterize microstructural contributions to the magnetic susceptibility of carotid arteries.

METHOD

Arterial vessels were scanned using high-resolution quantitative susceptibility mapping (QSM) at 7 Tesla. Models of vessel degradation were generated using ex vivo porcine carotid arteries that were subjected to several different enzymatic digestion treatments that selectively removed microstructural components (smooth muscle cells, collagen, and elastin). Magnetic susceptibilities measured in these tissue models were compared to those in untreated (native) porcine arteries. Magnetic susceptibility measured in native porcine carotid arteries was further compared to the susceptibility of cadaveric human carotid arteries to investigate their similarity.

RESULTS

The magnetic susceptibility of native porcine vessels was diamagnetic (χ_native = -0.1820 ppm), with higher susceptibilities in all models of vessel degradation (χ_{elastin-degraded} = -0.0163 ppm; χ_{collagen-degraded} = -0.1158 ppm; χ_{decellularized} = -0.1379 ppm; χ_{fixed native} = -0.2199 ppm). Magnetic susceptibility was significantly higher in collagen-degraded compared to native porcine vessels (Tukey-Kramer, P < .01) and between elastin-degraded and all other models (including native, Tukey-Kramer, P < .001). The susceptibility of fixed healthy human arterial tissue was diamagnetic, and no significant difference was found between fixed human and fixed porcine arterial tissue susceptibilities (analysis of variance, P > .05).

CONCLUSIONS

Magnetic susceptibility measured using QSM is sensitive to the microstructural composition of arterial vessels-most notably to collagen. The similarity of human and porcine arterial tissue susceptibility values provides a solid basis for translational studies. Because vessel microstructure becomes disrupted during the onset and progression of carotid atherosclerosis, QSM has the potential to provide a sensitive and specific marker of vessel disease.