An Up-to-Date Review on Cerebral Microbleeds

BACKGROUND

Cerebral microbleeds (CMBs) are small cerebrovascular lesions. More and more CMBs have been found in patients with ischemic stroke, dementia, and cerebral amyloid angiopathy, as well as some normal elderly populations. The objective of this study is to summarize the main risk factor, impairment, and therapy of CMBs.

METHODS

We searched and scanned all the literature with the keyword "cerebral microbleeds" or "CMBs" in the database of PubMed and Elsevier.

RESULTS

The risks factors for CMBs are complicated, including those that cause large-vessel disease, such as hypertension and old age, and those that cause small-vessel disease, such as amyloid deposits, endothelial lesions, and atrial fibrillation. Moreover, drugs and therapies used to treat cerebrovascular diseases such as statin, intravenous thrombolysis, and coumarin may also increase risk of CMBs. The relationship between antiplatelet treatment and CMBs is now unclear. Gene polymorphisms have been considered to be associated with CMBs. Gene mutations involving collagen type IV alpha 1 and collagen type IV alpha 2, sortilin-related receptor gene, forkhead box C1, and paired-like homeodomain 2 were reported to affect CMBs with the modification of corresponding proteins and functions. The cognition impairment caused by CMBs draws great attention. White matter deterioration is the possible answer. However, different studies could not reach the same conclusion on the damage of cognition of CMBs.

CONCLUSIONS

Further research is needed to provide effectual therapeutic proposals for CMBs, which differ from the treatment for large-artery disease and dementia.

The relation between APOE genotype and cerebral microbleeds in cognitively unimpaired middle- and old-aged individuals

Positive associations between cerebral microbleeds (CMBs) and APOE-ε4 (apolipoprotein E) genotype have been reported in Alzheimer's disease, but show conflicting results. We investigated the effect of APOE genotype on CMBs in a cohort of cognitively unimpaired middle- and old-aged individuals enriched for APOE-ε4 genotype. Participants from ALFA (Alzheimer and Families) cohort were included and their magnetic resonance scans assessed (n = 564, 50% APOE-ε4 carriers). Quantitative magnetic resonance analyses included visual ratings, atrophy measures, and white matter hyperintensity (WMH) segmentations. The prevalence of CMBs was 17%, increased with age (p < 0.05), and followed an increasing trend paralleling APOE-ε4 dose. The number of CMBs was significantly higher in APOE-ε4 homozygotes compared to heterozygotes and non-carriers (p < 0.05). This association was driven by lobar CMBs (p < 0.05). CMBs co-localized with WMH (p < 0.05). No associations between CMBs and APOE-ε2, gray matter volumes, and cognitive performance were found. Our results suggest that cerebral vessels of APOE-ε4 homozygous are more fragile, especially in lobar locations. Co-occurrence of CMBs and WMH suggests that such changes localize in areas with increased vascular vulnerability.

The brains of aged mice are characterized by altered tissue diffusion properties and cerebral microbleeds

Background

Brain aging is a major risk factor in the progression of cognitive diseases including Alzheimer’s disease (AD) and vascular dementia. We investigated a mouse model of brain aging up to 24 months old (mo).

Methods

A high field (11.7T) MRI protocol was developed to characterize specific features of brain aging including the presence of cerebral microbleeds (CMBs), morphology of grey and white matter, and tissue diffusion properties. Mice were selected from age categories of either young (3 mo), middle-aged (18 mo), or old (24 mo) and fed normal chow over the duration of the study. Mice were imaged in vivo with multimodal MRI, including conventional T2-weighted (T2W) and T2*-weighted (T2*W) imaging, followed by ex vivo diffusion-weighted imaging (DWI) and T2*W MR-microscopy to enhance the detection of microstructural features.

Results

Structural changes observed in the mouse brain with aging included reduced cortical grey matter volume and enlargement of the brain ventricles. A remarkable age-related change in the brains was the development of CMBs found starting at 18 mo and increasing in total volume at 24 mo, primarily in the thalamus. CMBs presence was confirmed with high resolution ex vivo MRI and histology. DWI detected further brain tissue changes in the aged mice including reduced fractional anisotropy, increased radial diffusion, increased mean diffusion, and changes in the white matter fibers visualized by color-coded tractography, including around a large cortical CMB.

Conclusions

The mouse is a valuable model of age-related vascular contributions to cognitive impairment and dementia (VCID). In composite, these methods and results reveal brain aging in older mice as a multifactorial process including CMBs and tissue diffusion alterations that can be well characterized by high field MRI.

Incident cerebral microbleeds and hypertension defined by the 2017 ACC/AHA Guidelines

Background

The cut-off for hypertension was lowered to blood pressure (BP) over 130/80 mmHg in the 2017 American College of Cardiology/American Heart Association (ACC/AHA) guideline. Whether the new definition of hypertension remains a potent risk factor of cerebral microbleeds (CMBs) is uncertain. We aimed to analyze the relationship between the new definition of hypertension and incident CMBs in a 7-year longitudinal community study.

Methods

This study is a sub-study of the Shanghai Aging Study (SAS). A total of 317 participants without stroke or dementia were included at baseline (2009–2011), and were invited to repeated clinical examinations and cerebral magnetic resonance imaging (MRI) at follow-up (2016–2018). CMBs at baseline and follow-up were evaluated on T2*-weighted gradient recalled echo (GRE) and susceptibility-weighted angiography (SWAN) sequence of MRI. We classified baseline BP into four categories: normal BP, elevated systolic BP, stage 1 hypertension and stage 2 hypertension according to the ACC/AHA guideline. We assessed the associations between BP categories and incident CMBs by generalized linear models.

Results

A total of 159 participants (median age, 67 years) completed follow–up examinations with a mean interval of 6.9 years. Both stage 1 and stage 2 hypertension at baseline were significantly related with a higher risk of incident CMBs (IRR 2.77, 95% CI, 1.11–6.91, P=0.028; IRR 3.04, 95% CI, 1.29–7.16, P=0.011, respectively), indicating dose-response effects across BP categories. Participants with ≥5 incident CMBs or incident CMBs in the deep locations all had baseline stage 1 and 2 hypertension.

Conclusions

Participants with baseline stage 1 and stage 2 hypertension had a significantly higher risk of incident CMBs in this 7-year longitudinal community cohort.

ALDH2 rs671 polymorphisms and the risk of cerebral microbleeds in Chinese elderly: the Taizhou Imaging Study

Background

Cerebral microbleeds (CMBs) are more prevalent in Asian populations, and have been associated with increased risk of stroke, dementia and mortality. So far, risk factors for CMBs other than hypertension were merely known. Previous studies have shown that polymorphisms at aldehyde dehydrogenase 2 (ALDH2) gene were independently associated with the risk of stroke. Its role in CMBs, however, remains unclear. This study aimed to evaluate the associations of ALDH2 gene polymorphisms with CMBs in Chinese elderly.

Methods

Using bio-specimen and data collected at baseline survey of the population-based Taizhou Imaging Study (TIS) (phase I), we genotyped the single nucleotide polymorphisms (SNPs) at ALDH2 among 549 individuals aged 55–65 years, and rs671 was used as surrogate marker of ALDH2. CMBs were detected on brain magnetic resonance imaging (MRI), and further categorized as strictly lobar or as deep/mixed. Logistic regression models were used to evaluate the associations of the variants at ALDH2 and CMBs.

Results

CMBs were present in 103 individuals (18.8%). Forty-one point three percent participants were with ALDH2 *2 allele and 5.1% had ALDH2 *2/*2 genotype. Subjects with ALDH2 *1 allele were more likely to be drinker, have hypertension or CMBs than those with *2 allele (all P<0.05). Multivariate logistic regression model showed that the ALDH2 *1/*1 genotype was independently associated with CMBs (P=0.013), particularly for deep/mixed CMBs (P=0.008), and the association was more pronounced in men, non-drinkers or hypertension patients.

Conclusions

The results suggest that Han Chinese with ALDH2 *1/*1 genotype may be more susceptible to CMBs than those with ALDH2 *2 allele.

Enhanced Reader Confidence and Differentiation of Calcification from Cerebral Microbleed Diagnosis Using QSM Relative to SWI

PURPOSE

Accurate detection of cerebral microbleeds (CMBs) is important for detection of multiple conditions. However, CMBs can be challenging to identify on MR images, especially for distinguishing CMBs from the mimic of calcification. We performed a comparative reader study to assess the diagnostic performance of two primary MR sequences for differentiating CMBs from calcification.

METHODS

Under IRB approved exempt retrospective protocol, 49 adult patients with identifiable intracranial hemorrhage who underwent multi-echo 3D Gradient Recall Echo (GRE) using 3T MRI were non-sequentially recruited under a retrospective IRB approved protocol. Multi-echo complex total field inversion quantitative susceptibility mapping (QSM) and susceptibility weighted imaging/phase (SWI/P) images were generated for all patients. 53 lesion ROIs were identified and classified on provided images by an expert panel of three neuroradiologists as either: CMB, Blood, Calcification, or Other. Three additional neuroradiologists subsequently reviewed the same SWI/P and QSM images in independent sessions and designated lesions as either blood and/or calcification using a 5-point Likert scale. Statistical analyses, on lesion classification and reader diagnostic accuracy, reader confidence-level, reader agreement-level, and the predictability of mean susceptibility values between SWI/P and QSM were conducted with logistic regression and calculation of Fleiss' κ, Kendall's w, Krippendorff's α.

RESULTS

Across all qualitative assessment and quantitative metrics measured (simple accuracy, confidence as degree of ground truth alignment, and inter-rater agreement) QSM outperformed SWI/P. Additionally, logistic regression of average QSM voxel susceptibility achieved near-perfect separation in differentiating between CMB and calcification in the limited number of CMB/Calcification ROIs, indicating a high predictability.

CONCLUSION

Our study demonstrates that QSM offers improved detectability and classification of CMBs compared to the conventionally utilized SWI/P sequence. In addition, QSM simplifies the interpretation workflow by reducing the number of requisite images compared with the conventional counterpart, with improved diagnostic confidence.

Impact of cerebral microbleeds on cognitive functions and its risk factors in acute cerebral infarction patients

BACKGROUND

Cerebral microbleeds (CMBs) are subclinical lesions of the brain parenchyma and an important marker for the clinical diagnosis of central nervous system vascular disease. However, the relationship between CMBs and cerebral infarction, cerebral hemorrhage, and cognitive impairment remains unclear.

METHODS

In order to explore the cognitive function and risk factors of patients with acute cerebral infarction (ACI) complicated with cerebral microbleeds, 190 patients with ACI were collected. The patients were divided into groups with CMBs (n = 108) and groups without CMBs (n = 82) according to the presence or absence of CMBs. The general data, various examination indicators, Montreal Cognitive Assessment Scale (MoCA) scores of the two groups of patients were analyzed. Sixty healthy controls who underwent physical examination in our hospital during the same period were included as the healthy control group.

RESULTS

ACI patients with CMBs had significantly higher rates of leukoaraiosis, hyperhomocysteinemia, hypercholesterolemia, and hypertension. Cognitive function was significantly lower in ACI patients with CMBs. Serum D-dimer, serum high-sensitivity C-reactive protein, serum neuron-specific enolase, and serum S100β of ACI patients with CMBs were all negatively correlated with their MoCA scores.

CONCLUSION

ACI patients with CMBs tended to have lower cognitive abilities than ACI patients without CMBs.

Cerebral small vessel disease and its relationship with all-cause mortality risk: Results from the Amsterdam Ageing cohort

INTRODUCTION

Cerebral Small-Vessel Disease (CSVD) is a complex condition affecting the brain's vascular network, linked to cognitive and physical decline, cerebrovascular disease, and death. This study assesses the relationship between CSVD (composite and individual features) and all-cause mortality in a large cohort of geriatric outpatients.

METHODS

Data from 1305 geriatric outpatients (mean age 78 ± 7; 51 % female) in the Amsterdam Ageing cohort were analysed. CSVD presence was based on brain imaging (MRI or CT), defined by a Fazekas score ≥ 2, presence of ≥1 lacunes, or (in MRI) ≥ 3 microbleeds. Mortality data (February 2016 - January 2024) was sourced from the Dutch Municipality Register. The relationship between CSVD and all-cause mortality was evaluated using a Cox proportional-hazards model, adjusting for key confounders.

RESULTS

At baseline, 835 (64 %) of the 1305 patients had CSVD. During a median follow-up of 3.1 years (IQR 1.6-4.6 years), all-cause mortality was 40 % (333 patients) in the CSVD group and 26 % (121 patients) in the non-CSVD group, corresponding with incidence rates of 137 and 78 per 1000 patient-years, respectively. The age- and sex-adjusted hazard ratio for mortality in the CSVD group was 1.6 (95 % CI: 1.3-2.0). This association remained significant after adjusting for cardiovascular disease and its risk factors, physical function (gait speed), and cognitive function (MMSE).

CONCLUSION

Radiographic CSVD presence is prevalent and its integration into daily care is important as it is independently linked to increased all-cause mortality in geriatric outpatients.