MRI for in vivo diagnosis of cerebral amyloid angiopathy: Tailoring artifacts to image hemorrhagic biomarkers

Cerebral amyloid angiopathy (CAA) is a frequent age-related small vessel disease (SVD) with cardinal magnetic resonance imaging (MRI) signatures that are hemorrhagic in nature, and include the presence of strictly lobar (superficial) cerebral microbleeds and intracerebral hemorrhages as well as cortical superficial siderosis. When investigating a patient with suspected CAA in the context of intracranial hemorrhage (parenchymal or subarachnoid) or cognitive dysfunction, various MRI parameters influence the optimal detection and characterization (and prognostication) of this frequent SVD. The present report describes the influence of imaging techniques on the detection of the key hemorrhagic CAA imaging signatures in clinical practice, in research studies, and the imaging parameters that must be understood when encountering a CAA patient, as well as reviewing CAA literature.

Cerebral Microbleeds Remain for Nine Years: A Prospective Study with Yearly Magnetic Resonance Imaging

BACKGROUND

Cerebral microbleeds (CMBs) are refined neuroimaging findings detected on T2*-weighted gradient echo (GRE) magnetic resonance imaging (MRI) and are widely accepted as an important marker of the vulnerability of cerebral small vessels. It is necessary to further clarify the natural history of CMBs by a longitudinal study. This study aimed to reveal the natural history of CMBs and find a better way to track CMBs by a prospective long-term observation.

METHODS

We performed yearly brain MRI assessments for 7 or more years in 8 nonvalvular atrial fibrillation Japanese outpatients with CMBs detected in the baseline MRI. We began to use a 3.0T MRI scanner from 2012 as well.

RESULTS

We followed up 3 patients for 9 years, 2 for 8 years, and 3 for 7 years. In all patients, the CMBs at baseline did not disappear during the follow-up period. Importantly, the CMB in 1 patient seemed to disappear during the sixth imaging using 1.5T T2*-weighted GRE but was detected again during the seventh imaging with 3.0T susceptibility weighted imaging and ninth imaging with 3.0T T2* GRE. Moreover, in a patient implanted with a pacemaker, which is only applicable for 1.5T MRI at present, the CMB seemed to disappear and appeared once again with a 1.5T T2*-weighted GRE at a slice thickness of 2.5 mm instead of 5 mm.

CONCLUSIONS

From this prospective study, we obtained 2 absolutely new findings that CMBs remained for as long as 9 years and a high-field or thin-slice MRI can detect concealed CMBs.

Location of Cerebral Microbleeds And Their Association with Carotid Intima-media Thickness: A Community-based Study

To assess whether high cerebral microbleeds (CMBs) are associated with carotid intima-media thickness (CIMT), a marker of systemic atherosclerosis, we cross-sectionally evaluated participants from a community-based study, the I-Lan Longitudinal Aging Study. The participants' demographics and cardiovascular risk factors were determined by questionnaire and/or laboratory measurements. CIMT was measured by ultrasonography. CMBs were assessed by susceptibility-weighted-imaging on 3 T MRI. Of the 962 subjects [62.5(8.6) years, 44.2% men] included, CMBs were found in 134(14.0%) subjects. Among the subjects with identified CMB's, 85(63.4%) had deep or infratentorial (DI) and 49(36.6%) had strictly lobar(SL) CMBs. After the results were adjusted for age and sex, the analysis revealed that hypertension, hyperlipidemia, obesity, and higher triglyceride levels correlated with DI but not SL CMBs. The subjects with DI CMBs also had a higher mean CIMT and higher prevalence of top quartile CIMT. The multivariate analysis demonstrated that high CIMT (top quartile) significantly predicted the presence of DI CMBs (odds ratio = 2.1; 95% confidence interval = 1.3-3.4; P = 0.004), independent of age, sex, cardiovascular risk factors, and other cerebral small vessel diseases, lacune, and white matter hyperintensity. There was no association between CIMT and SL CMBs. Our results support that there are distinct pathogenesis in DI and SL CMBs.

Developing an algorithm to identify patients with intracerebral haemorrhage secondary to a macrovascular cause

Introduction

Determining the cause of spontaneous (non-traumatic) intracerebral haemorrhage (ICH) is critical to guide treatment and prognosis. We investigated whether small vessel disease (SVD) in addition to clinical and other radiological findings on acute neuroimaging predicts a low risk of a macrovascular cause (e.g. an arterio-venous malformation, aneurysm or dural arteriovenous fistula).

Patients and methods

We identified patients with acute spontaneous ICH who underwent acute non-contrast CT, CT angiography (CTA) and intra-arterial digital subtraction angiography (IADSA) at our institution from January 2010 to April 2014. Logistic regression including CTA result, SVD, age, pre-ICH hypertension and ICH location was used to derive a prediction model, validated using bootstrapping.

Results

173 patients (46% female, median age 49) of whom 78 had a macrovascular cause on IADSA were included. Predictors of a macrovascular cause were: abnormal CTA (OR 67.4; p < 0.001); absence of SVD (OR 5.0; p = 0.019); and absence of pre-ICH hypertension (OR 3.4; p = 0.05). In our internally derived prediction model, the combination of CTA, SVD and pre-ICH hypertension predicted the likelihood of an underlying macrovascular cause (optimism-adjusted ROC area 0.919). Patients with negative CTA, SVD and pre-ICH hypertension have a low likelihood of an underlying macrovascular cause (1.8%).

Discussion and conclusion

A combination of CTA, SVD and pre-ICH hypertension predict the likelihood of finding a macrovascular cause in patients with acute spontaneous ICH, allowing informed decisions regarding the likely benefit and risk of IADSA.

Uncommon Causes of Cerebral Microbleeds

BACKGROUND

Cerebral microbleeds (CMBs) are small and round perivascular hemosiderin depositions detectable by gradient echo sequences or susceptibility-weighted imaging. Cerebral microbleeds are common among patients with hypertension, cerebral ischemia, or cerebral amyloid angiopathy. In this article, we describe uncommon causes of CMBs.

METHODS

We searched Pubmed with the keyword CMBs for relevant studies and looked for different uncommon causes of CMBs.

RESULTS

CMBs have several uncommon etiologies including posterior reversible encephalopathy syndrome, infective endocarditis, brain radiation therapy, cocaine abuse, thrombotic thrombocytopenic purpura, traumatic brain injury, intravascular lymphomatosis or proliferating angio-endotheliomatosis, moyamoya disease, sickle cell anemia/β-thalassemia, cerebral autosomal dominant arteriopathy subcortical infarcts, and leukoencephalopathy (CADASIL), genetic syndromes, or obstructive sleep apnea.

CONCLUSIONS

Understanding the uncommon causes of CMBs is not only helpful in diagnosis and prognosis of some of these rare diseases, but can also help in better understanding different pathophysiology involved in the development of CMBs.

Microbleeds in the Secondary Prevention of Small Subcortical Strokes Trial: Stroke, mortality, and treatment interactions

OBJECTIVE

To characterize cerebral microbleeds (CMBs) in lacunar stroke patients in the Secondary Prevention of Small Subcortical Strokes (SPS3) trial and to assess their relationship with recurrent stroke and death, and response to assigned treatment.

METHODS

SPS3 is a randomized, clinical trial conducted between 2003 and 2011. Patients with recent magnetic resonance imaging (MRI)-documented lacunar infarcts were randomly assigned in a factorial design to target levels of systolic blood pressure (130-149mmHg vs <130mmHg; open label) and to antiplatelet treatment (aspirin/clopidogrel vs aspirin/placebo; double-blinded). The current analysis involves 1,278 trial participants who had a baseline axial T2*-weighted gradient echo MRI sequence allowing for CMB detection.

RESULTS

CMBs were present in 30% of 1,278 patients (mean age = 63 years). Male gender (odds ratio [OR] = 1.7, 95% confidence interval [CI] = 1.3-2.3), history of hypertension (OR = 1.6, 95% CI = 1.2-2.3), increased systolic blood pressure (1.2 per 20mmHg, 95% CI = 1.1-1.4), nondiabetic status (OR = 1.4, 95% CI = 1.1-1.9), multiple old lacunar infarcts (OR = 1.9, 95% CI = 1.5-2.5), and moderate (OR = 1.7, 95% CI = 1.2-2.3) or severe (OR = 4.2, 95% CI = 3.0-5.9) white matter hyperintensities on MRI were independently associated with CMBs. During a mean follow-up of 3.3 years, overall stroke recurrence was 2.5% per patient-year. Patients with CMBs had an adjusted 2-fold increased risk of recurrent stroke (hazard ratio = 2.1, 95% CI = 1.4-3.1). CMBs were not a risk factor for death. There were no statistically significant interactions between CMBs and treatment assignments.

INTERPRETATION

Patients with lacunar stroke and CMBs likely harbor a more advanced form of cerebral small vessel disease in need of efficacious therapeutic strategies. Ann Neurol 2017;82:196-207.

Putative Cerebral Microbleeds in Dogs Undergoing Magnetic Resonance Imaging of the Head: A Retrospective Study of Demographics, Clinical Associations, and Relationship to Case Outcome

BACKGROUND

Cerebral microbleeds (CMBs) are focal intraparenchymal signal voids on gradient-echo magnetic resonance imaging (MRI), corresponding to regions of chronic hemorrhage. In humans, they are associated with systemic disease and shorter survival times. Although similar findings have been identified in dogs, their epidemiology and clinical correlations have not been investigated.

OBJECTIVE

To determine epidemiological features, clinical associations, and associations with outcome for putative CMB-like foci (putative microbleeds [pMBs]) identified by T2*-weighted MRI in dogs.

ANIMALS

Five hundred and eighty-two dogs undergoing 3T brain MRI between 2011 and 2016.

METHODS

Retrospective case-control study. Demographic, diagnostic, and clinicopathological data were obtained from medical records and phone follow-up. Demographic variables were compared between dogs with and without evidence of pMBs. For dogs with such evidence, and a subset of matched controls, associations with clinical presentation, concurrent disease, and survival times were evaluated.

RESULTS

Dogs with pMBs were older (P < .001) and smaller (P = .004) than unaffected dogs. Compared to matched controls, they presented more frequently for vestibular signs (P = .030). Cortical atrophy occurred concurrently with pMBs in 26% (14/54) of dogs. Diagnosed renal disease was not significantly associated with pMBs, but proteinuria was more common in dogs with pMBs than in matched controls (odds ratio = 3.01, P = .005). Dogs with pMBs had a shorter median survival time than did matched controls (P = .011).

CONCLUSIONS AND CLINICAL IMPORTANCE

Putative microbleeds occurred in 54 of 582 (9.3%) of dogs undergoing brain MRI, but may not be a normal consequence of aging. They were associated with shorter survival time and proteinuria in the study population.

Amyloid positron emission tomography in sporadic cerebral amyloid angiopathy: A systematic critical update

Sporadic cerebral amyloid angiopathy (CAA) is a very common small vessel disease of the brain, showing preferential and progressive amyloid-βdeposition in the wall of small arterioles and capillaries of the leptomeninges and cerebral cortex. CAA now encompasses not only a specific cerebrovascular pathological trait, but also different clinical syndromes - including spontaneous lobar intracerebral haemorrhage (ICH), dementia and ‘amyloid spells’ - an expanding spectrum of brain parenchymal MRI lesions and a set of diagnostic criteria – the Boston criteria, which have resulted in increasingly detecting CAA during life. Although currently available validated diagnostic criteria perform well in multiple lobar ICH, a formal diagnosis is currently lacking unless a brain biopsy is performed. This is partly because in practice CAA MRI biomarkers provide only indirect evidence for the disease. An accurate diagnosis of CAA in different clinical settings would have substantial impact for ICH risk stratification and antithrombotic drug use in elderly people, but also for sample homogeneity in drug trials. It has recently been demonstrated that vascular (in addition to parenchymal) amyloid-βdeposition can be detected and quantified in vivo by positron emission tomography (PET) amyloid tracers. This non-invasive approach has the potential to provide a molecular signature of CAA, and could in turn have major clinical impact. However, several issues around amyloid-PET in CAA remain unsettled and hence its diagnostic utility is limited. In this article we systematically review and critically appraise the published literature on amyloid-PET (PiB and other tracers) in sporadic CAA. We focus on two key areas: (a) the diagnostic utility of amyloid-PET in CAA and (b) the use of amyloid-PET as a window to understand pathophysiological mechanism of the disease. Key issues around amyloid-PET imaging in CAA, including relevant technical aspects are also covered in depth. A total of six small-scale studies have addressed (or reported data useful to address) the diagnostic utility of late-phase amyloid PET imaging in CAA, and one additional study dealt with early PiB images as a proxy of brain perfusion. Across these studies, amyloid PET imaging has definite diagnostic utility (currently tested only in probable CAA): it helps rule out CAA if negative, whether compared to healthy controls or to hypertensive deep ICH controls. If positive, however, differentiation from underlying incipient Alzheimer's disease (AD) can be challenging and so far, no approach (regional values, ratios, visual assessment) seems sufficient and specific enough, although early PiB data seem to hold promise. Based on the available evidence reviewed, we suggest a tentative diagnostic flow algorithm for amyloid-PET use in the clinical setting of suspected CAA, combining early- and late-phase PiB-PET images. We also identified ten mechanistic amyloid-PET studies providing early but promising proof-of-concept data on CAA pathophysiology and its various manifestations including key MRI lesions, cognitive impairment and large scale brain alterations. Key open questions that should be addressed in future studies of amyloid-PET imaging in CAA are identified and highlighted.

•

CAA is a major cause of brain haemorrhage and cognitive impairment in aged subjects.

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Without brain biopsy, its current diagnosis largely relies on indirect MRI markers.

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Amyloid PET may provide a non-invasive molecular signature to formally diagnose CAA.

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Based on our review, amyloid PET has excellent sensitivity but specificity is unclear.

•

Amyloid PET is also useful to investigate mechanisms underlying CAA manifestations.

Intracerebral haemorrhage risk in microbleed-positive ischaemic stroke patients with atrial fibrillation: Preliminary meta-analysis of cohorts and anticoagulation decision schema

INTRODUCTION

Whether ischaemic stroke patients with atrial fibrillation (AF) and cerebral microbleeds (CMBs) on MRI can be safely anticoagulated is a hotly debated topic. We performed a systematic review and meta-analysis of published aggregate data, to investigate the risk of subsequent intracerebral haemorrhage (ICH) based on CMBs presence in this stroke population, generally considered for oral anticoagulation. We also suggest a decision-making schema for anticoagulation use in this setting.

METHODS

We searched PubMed for relevant observational studies. Random effects models with DerSimonian-Laird weights were used to investigated the association between CMBs presence at baseline MRI and ICH or ischaemic stroke during follow-up.

RESULTS

Four studies, with slightly heterogeneous design, including 990 ischaemic stroke patients were pooled in a meta-analysis (crude CMBs prevalence: 25%; 95%CI: 17%-33%). The median follow-up ranged between 17 and 37months. The future symptomatic ICH rate was 1.6% (16/990), while recurrent ischaemic stroke rate was 5.9% (58/990). Baseline CMB presence was associated with increased risk of symptomatic ICH during follow-up compared to patients without CMBs (OR: 4.16; 95%CI: 1.54-11.25; p=0.005). There was no association between CMBs presence and recurrent ischaemic stroke risk.

CONCLUSION

We have shown that the presence of CMBs in cohorts of ischaemic stroke patients, most with AF on warfarin, is associated with a 4-fold increase in subsequent ICH (but not ischaemic stroke) risk (Class III evidence). These pooled estimates are useful for future trials design. We propose a simple data-driven anticoagulation schema which awaits validation and refinement as new prospective data are accumulated.

Determination of detection sensitivity for cerebral microbleeds using susceptibility-weighted imaging

Cerebral microbleeds (CMBs) are small brain hemorrhages caused by the break down or structural abnormalities of small vessels of the brain. Owing to the paramagnetic properties of blood degradation products, CMBs can be detected in vivo using susceptibility-weighted imaging (SWI). SWI can be used not only to detect iron changes and CMBs, but also to differentiate them from calcifications, both of which may be important MR-based biomarkers for neurodegenerative diseases. Moreover, SWI can be used to quantify the iron in CMBs. SWI and gradient echo (GE) imaging are the two most common methods for the detection of iron deposition and CMBs. This study provides a comprehensive analysis of the number of voxels detected in the presence of a CMB on GE magnitude, phase and SWI composite images as a function of resolution, signal-to-noise ratio (SNR), TE, field strength and susceptibility using in silico experiments. Susceptibility maps were used to quantify the bias in the effective susceptibility value and to determine the optimal TE for CMB quantification. We observed a non-linear trend with susceptibility for CMB detection from the magnitude images, but a linear trend with susceptibility for CMB detection from the phase and SWI composite images. The optimal TE values for CMB quantification were found to be 3 ms at 7 T, 7 ms at 3 T and 14 ms at 1.5 T for a CMB of one voxel in diameter with an SNR of 20: 1. The simulations of signal loss and detectability were used to generate theoretical formulae for predictions. Copyright © 2016 John Wiley & Sons, Ltd.

Overview of quantitative susceptibility mapping

Magnetic susceptibility describes the magnetizability of a material to an applied magnetic field and represents an important parameter in the field of MRI. With the recently introduced method of quantitative susceptibility mapping (QSM) and its conceptual extension to susceptibility tensor imaging (STI), the non-invasive assessment of this important physical quantity has become possible with MRI. Both methods solve the ill-posed inverse problem to determine the magnetic susceptibility from local magnetic fields. Whilst QSM allows the extraction of the spatial distribution of the bulk magnetic susceptibility from a single measurement, STI enables the quantification of magnetic susceptibility anisotropy, but requires multiple measurements with different orientations of the object relative to the main static magnetic field. In this review, we briefly recapitulate the fundamental theoretical foundation of QSM and STI, as well as computational strategies for the characterization of magnetic susceptibility with MRI phase data. In the second part, we provide an overview of current methodological and clinical applications of QSM with a focus on brain imaging. Copyright © 2016 John Wiley & Sons, Ltd.

Correlation of Cerebral Microbleed Distribution to Amyloid Burden in Patients with Primary Intracerebral Hemorrhage

The underlying pathology of cerebral microbleeds (CMBs) with mixed lobar and deep distribution remains contentious. The aim of this study was to correlate CMBs distribution to β-amyloid burden in patients with primary intracerebral hemorrhage (ICH). Fourty-seven ICH patients underwent magnetic resonance susceptibility-weighted imaging and ¹¹C-Pittsburgh Compound B positron emission tomography. The amyloid burden was expressed as standardized uptake value ratio with reference to cerebellum, and presented as median (interquartile range). Patients were categorized into the lobar, mixed (both lobar and deep regions), and deep types of CMB. Comparing the lobar (17%), mixed (59.6%) and deep (23.4%) CMB types, the global amyloid burden was significantly higher in the mixed type than the deep type (1.10 [1.03–1.25] vs 1.00 [0.97–1.09], p = 0.011), but lower than in the lobar type (1.48 [1.18–1.50], p = 0.048). On multivariable analysis, the ratio of lobar to deep CMB number was positively correlated with global (p = 0.028) and occipital (p = 0.031) amyloid burden. In primary ICH, patients with lobar and mixed CMB types are associated with increased amyloid burden than patients with deep type. The ratio of lobar to deep CMB number is an independent indicator of cerebral β-amyloid deposition.

Cerebral microbleeds topography and cerebrospinal fluid biomarkers in cognitive impairment

Cerebral microbleeds, a marker of small vessel disease, are thought to be of importance in cognitive impairment. We aimed to study topographical distribution of cerebral microbleeds, and their involvement in disease pathophysiology, reflected by cerebrospinal fluid biomarkers; 1039 patients undergoing memory investigation underwent lumbar puncture and a brain magnetic resonance imaging scan. Cerebrospinal fluid samples were analyzed for amyloid β(Aβ)42, total tau(T-tau), tau phosphorylated at threonine 18(P-tau) and cerebrospinal fluid/serum albumin ratios. Magnetic resonance imaging sequences were evaluated for small vessel disease markers, including cerebral microbleeds, white matter hyperintensities and lacunes. Low Aβ42 levels were associated with lobar cerebral microbleeds in the whole cohort and Alzheimer's disease ( P < 0.001). High cerebrospinal fluid/serum albumin ratios were seen with increased number of cerebral microbleeds in the brainstem ( P < 0.001). There were tendencies for increased Aβ42 levels and decreased Tau levels with deep and infratentorial cerebral microbleeds ( P < 0.05). Lobar cerebral microbleeds were associated with white matter hyperintensities and lacunes ( P < 0.001). Probable cerebral amyloid angiopathy-related cerebral microbleeds were associated with low Aβ42 levels and lacunes, whereas probable cerebral amyloid angiopathy-unrelated cerebral microbleeds were associated with white matter hyperintensities ( P < 0.001). Our findings show that cerebral microbleed distribution is associated with different patterns of cerebrospinal fluid biomarkers, supporting different pathogenesis of deep/infratentorial and lobar cerebral microbleeds.

Evolution of cerebral microbleeds after cranial irradiation in medulloblastoma patients

OBJECTIVE

To characterize the temporal and spatial pattern of cerebral microbleeds (CMBs) after cranial irradiation in patients with medulloblastoma.

METHODS

We retrospectively identified patients with medulloblastoma treated with craniospinal irradiation at the Massachusetts General Hospital between 1999 and 2015. Longitudinal MRI including T2*-weighted gradient-recalled echo (GRE) sequences were reviewed, and the prevalence, spatial pattern, and risk factors associated with CMBs were characterized.

RESULTS

We identified a total of 27 patients; 5 patients were children (median age 6.3 years) and 22 patients were adults (median age 28.8 years). CMBs were found in 67% (18/27) of patients, who were followed for a median of 4.1 years. Patients with CMBs had longer GRE follow-up time compared to those without CMBs (4.9 vs 1.7 years, p = 0.035). The median latency of the appearance of CMBs was 2.79 years (interquartile range 1.76-4.26). The prevalence of CMBs increased with each year from time of radiation therapy, and the cumulative prevalence was highest in patients age <20 years (100% cumulative prevalence, vs 59% in adult patients treated at age ≥20 years). CMBs were mostly found in lobar distribution and predominately in bilateral occipital lobes. Patients using antithrombotic medications developed CMBs at a significantly higher rate (p = 0.041).

CONCLUSIONS

Our data demonstrate a high prevalence of CMBs following cranial irradiation, progressively increasing with each year from time of radiation therapy.

Cerebral Microbleeds on MRI in Patients with Obstructive Sleep Apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is known to increase the risk of stroke. Cerebral microbleeds (CMBs) are considered one of the precursors to symptomatic stroke. We aimed to clarify the relationship between OSA and CMBs.

METHODS

We recruited patients who visited our clinic for the evaluation of sleep-disordered breathing. All patients underwent both overnight polysomnography and brain magnetic resonance imaging, which included T2*-weighted gradient-recalled echo images. We applied multivariate logistic regression and partial correlation analysis to estimate the relationship between OSA and CMBs.

RESULTS

A total of 75 (45 male, 30 female) patients were enrolled. Their mean age was 60.5 years. Patients with CMBs had a significantly higher apneahypopnea index (AHI) compared with those without CMBs. AHI equal to or greater than 15 was a significant independent predictor of CMBs (adjusted odds ratio, 4.51; 95% CI, 1.40-14.58; p = 0.012) in the multivariate regression analysis. In addition, a partial correlation analysis adjusted for age, hypertension, diabetes, and cardiovascular disease revealed a positive relationship between AHI and the number of CMBs (r = 0.585, p = 0.028).

CONCLUSIONS

Moderate-to-severe OSA can be one of the independent predictors of CMBs which are considered a surrogate marker of overt stroke.

Radiologic-Histopathologic Correlation of Cerebral Microbleeds Using Pre-Mortem and Post-Mortem MRI

Introduction

Cerebral microbleeds (CMB), also known as cerebral microhemorrhages, are small areas of susceptibility on brain magnetic resonance imaging (MRI), that are increasingly detected due to the higher availability of high-field MRI systems and dedicated pulse sequences. The prevalence of CMBs increases in cases with cognitive decline. The current investigation assessed the poorly investigated radiologic–histopathologic correlation of CMBs on MRI.

Methods

The local ethical committee approved the current investigation. We retrospectively assessed a consecutive series of 1303 autopsy cases hospitalized in Geneva University Hospitals between 2000–2014. Of 112 cases with pre-mortem T2* sequences, we included 25 cases (mean age 77.3 ± 9.6, 9 females) with at least one CMB. We compared pre-mortem CMBs with targeted histopathology and post-mortem MRI.

Results

25 cases had 31 CMB lesions detected by pre-mortem MRI. 25 additional CMB were detected on histopathology. 4 CMBs on pre-mortem MRI were false positives, resulting in a total of 52 CMBs. 27 CMBs on pre-mortem MRI were confirmed on histopathology, corresponding to a sensitivity or true positive rate of 51.9% (95% CI 37.6–66.0%). The false negative rate of pre-mortem MRI was 48.1% (95% CI 34.0–62.4%). Post-mortem MRI showed only 3 cases with additional CMBs. Overall, pre-mortem MRI significantly underestimated CMBs (p = 0.0001).

Conclusions

Routine clinical brain MRI underestimates the prevalence of CMBs by approximately 50%, and 12% of radiologic pre-mortem MRI CMBs were false positives. Post-mortem MRI confirmed that this discordance is not explained by microbleeds occurring after the pre-mortem MRI.

Structural MR Imaging in the Diagnosis of Alzheimer's Disease and Other Neurodegenerative Dementia: Current Imaging Approach and Future Perspectives

With the rise of aging population, clinical concern and research attention has shifted towards neuroimaging of dementia. The advent of 3T, magnetic resonance imaging (MRI) has permitted the anatomical imaging of neurodegenerative disease, specifically dementia, with improved resolution. Furthermore, more powerful techniques such as diffusion tensor imaging, quantitative susceptibility mapping, and magnetic transfer imaging have successfully emerged for the detection of micro-structural abnormalities. In the present review article, we provide a brief overview of Alzheimer's disease and explore recent neuroimaging developments in the field of dementia with an emphasis on structural MR imaging in order to propose a simple and easily applicable systematic approach to the imaging diagnosis of dementia.

The concept of sporadic cerebral small vessel disease: A road map on key definitions and current concepts

Sporadic cerebral small vessel disease is considered to be among the most common known neuropathological processes and has an important role in stroke, cognitive impairment, and functional loss in elderly persons. The term is now commonly used to describe a range of neuroimaging, neuropathological, and associated clinical features, the pathogenesis of which is largely unclear but that are thought to arise from disease affecting the perforating cerebral arterioles, capillaries, and venules. Modern neuroimaging has revolutionized our understanding of the consequences of small vessels disease on the brain parenchyma, even though small arteries, arterioles, capillaries, and venules are difficult to be directly visualized with current techniques used in clinical practice. In this short review, we focus on histopathological and neuroimaging perspectives, basic definitions, and recent advances in the field.

Microbleed and microinfarct detection in amyloid angiopathy: a high-resolution MRI-histopathology study

Cerebral amyloid angiopathy is a common neuropathological finding in the ageing human brain, associated with cognitive impairment. Neuroimaging markers of severe cerebral amyloid angiopathy are cortical microbleeds and microinfarcts. These parenchymal brain lesions are considered key contributors to cognitive impairment. Therefore, they are important targets for therapeutic strategies and may serve as surrogate neuroimaging markers in clinical trials. We aimed to gain more insight into the pathological basis of magnetic resonance imaging-defined microbleeds and microinfarcts in cerebral amyloid angiopathy, and to explore the pathological burden that remains undetected, by using high and ultra-high resolution ex vivo magnetic resonance imaging, as well as detailed histological sampling. Brain samples from five cases (mean age 85 ± 6 years) with pathology-proven cerebral amyloid angiopathy and multiple microbleeds on in vivo clinical magnetic resonance imaging were subjected to high-resolution ex vivo 7 T magnetic resonance imaging. On the obtained high-resolution (200 μm isotropic voxels) ex vivo magnetic resonance images, 171 microbleeds were detected compared to 66 microbleeds on the corresponding in vivo magnetic resonance images. Of 13 sampled microbleeds that were matched on histology, five proved to be acute and eight old microhaemorrhages. The iron-positive old microhaemorrhages appeared approximately four times larger on magnetic resonance imaging compared to their size on histology. In addition, 48 microinfarcts were observed on ex vivo magnetic resonance imaging in three out of five cases (two cases exhibited no microinfarcts). None of them were visible on in vivo 1.5 T magnetic resonance imaging after a retrospective analysis. Of nine sampled microinfarcts that were matched on histology, five were confirmed as acute and four as old microinfarcts. Finally, we explored the proportion of microhaemorrhage and microinfarct burden that is beyond the detection limits of ex vivo magnetic resonance imaging, by scanning a smaller sample at ultra-high resolution, followed by serial sectioning. At ultra-high resolution (75 μm isotropic voxels) magnetic resonance imaging we observed an additional 48 microbleeds (compared to high resolution), which proved to correspond to vasculopathic changes (i.e. morphological changes to the small vessels) instead of frank haemorrhages on histology. After assessing the serial sections of this particular sample, no additional haemorrhages were observed that were missed on magnetic resonance imaging. In contrast, nine microinfarcts were found in these sections, of which six were only retrospectively visible at ultra-high resolution. In conclusion, these findings suggest that microbleeds on in vivo magnetic resonance imaging are specific for microhaemorrhages in cerebral amyloid angiopathy, and that increasing the resolution of magnetic resonance images results in the detection of more 'non-haemorrhagic' pathology. In contrast, the vast majority of microinfarcts currently remain under the detection limits of clinical in vivo magnetic resonance imaging.

The Cerebrovascular-Chronic Kidney Disease Connection: Perspectives and Mechanisms

Chronic kidney disease (CKD) is an independent risk factor for the development of cerebrovascular disease, particularly small vessel disease which can manifest in a variety of phenotypes ranging from lacunes to microbleeds. Small vessel disease likely contributes to cognitive dysfunction in the CKD population. Non-traditional risk factors for vascular injury in uremia include loss of calcification inhibitors, hyperphosphatemia, increased blood pressure variability, elastinolysis, platelet dysfunction, and chronic inflammation. In this review, we discuss the putative pathways by which these mechanisms may promote cerebrovascular disease and thus increase risk of future stroke in CKD patients.

Recurrent stroke risk and cerebral microbleed burden in ischemic stroke and TIA: A meta-analysis

Objective:

To determine associations between cerebral microbleed (CMB) burden with recurrent ischemic stroke (IS) and intracerebral hemorrhage (ICH) risk after IS or TIA.

Methods:

We identified prospective studies of patients with IS or TIA that investigated CMBs and stroke (ICH and IS) risk during ≥3 months follow-up. Authors provided aggregate summary-level data on stroke outcomes, with CMBs categorized according to burden (single, 2–4, and ≥5 CMBs) and distribution. We calculated absolute event rates and pooled risk ratios (RR) using random-effects meta-analysis.

Results:

We included 5,068 patients from 15 studies. There were 115/1,284 (9.6%) recurrent IS events in patients with CMBs vs 212/3,781 (5.6%) in patients without CMBs (pooled RR 1.8 for CMBs vs no CMBs; 95% confidence interval [CI] 1.4–2.5). There were 49/1,142 (4.3%) ICH events in those with CMBs vs 17/2,912 (0.58%) in those without CMBs (pooled RR 6.3 for CMBs vs no CMBs; 95% CI 3.5–11.4). Increasing CMB burden increased the risk of IS (pooled RR [95% CI] 1.8 [1.0–3.1], 2.4 [1.3–4.4], and 2.7 [1.5–4.9] for 1 CMB, 2–4 CMBs, and ≥5 CMBs, respectively) and ICH (pooled RR [95% CI] 4.6 [1.9–10.7], 5.6 [2.4–13.3], and 14.1 [6.9–29.0] for 1 CMB, 2–4 CMBs, and ≥5 CMBs, respectively).

Conclusions:

CMBs are associated with increased stroke risk after IS or TIA. With increasing CMB burden (compared to no CMBs), the risk of ICH increases more steeply than that of IS. However, IS absolute event rates remain higher than ICH absolute event rates in all CMB burden categories.

Update on cerebral small vessel disease: a dynamic whole-brain disease

Cerebral small vessel disease (CSVD) is a very common neurological disease in older people. It causes stroke and dementia, mood disturbance and gait problems. Since it is difficult to visualise CSVD pathologies in vivo, the diagnosis of CSVD has relied on imaging findings including white matter hyperintensities, lacunar ischaemic stroke, lacunes, microbleeds, visible perivascular spaces and many haemorrhagic strokes. However, variations in the use of definition and terms of these features have probably caused confusion and difficulties in interpreting results of previous studies. A standardised use of terms should be encouraged in CSVD research. These CSVD features have long been regarded as different lesions, but emerging evidence has indicated that they might share some common intrinsic microvascular pathologies and therefore, owing to its diffuse nature, CSVD should be regarded as a 'whole-brain disease'. Single antiplatelet (for acute lacunar ischaemic stroke) and management of traditional risk factors still remain the most important therapeutic and preventive approach, due to limited understanding of pathophysiology in CSVD. Increasing evidence suggests that new studies should consider drugs that target endothelium and blood-brain barrier to prevent and treat CSVD. Epidemiology of CSVD might differ in Asian compared with Western populations (where most results and guidelines about CSVD and stroke originate), but more community-based data and clear stratification of stroke types are required to address this.

Post-mortem assessment in vascular dementia: advances and aspirations

BACKGROUND

Cerebrovascular lesions are a frequent finding in the elderly population. However, the impact of these lesions on cognitive performance, the prevalence of vascular dementia, and the pathophysiology behind characteristic in vivo imaging findings are subject to controversy. Moreover, there are no standardised criteria for the neuropathological assessment of cerebrovascular disease or its related lesions in human post-mortem brains, and conventional histological techniques may indeed be insufficient to fully reflect the consequences of cerebrovascular disease.

DISCUSSION

Here, we review and discuss both the neuropathological and in vivo imaging characteristics of cerebrovascular disease, prevalence rates of vascular dementia, and clinico-pathological correlations. We also discuss the frequent comorbidity of cerebrovascular pathology and Alzheimer's disease pathology, as well as the difficult and controversial issue of clinically differentiating between Alzheimer's disease, vascular dementia and mixed Alzheimer's disease/vascular dementia. Finally, we consider additional novel approaches to complement and enhance current post-mortem assessment of cerebral human tissue.

CONCLUSION

Elucidation of the pathophysiology of cerebrovascular disease, clarification of characteristic findings of in vivo imaging and knowledge about the impact of combined pathologies are needed to improve the diagnostic accuracy of clinical diagnoses.

Evaluating the Role of Reduced Oxygen Saturation and Vascular Damage in Traumatic Brain Injury Using Magnetic Resonance Perfusion-Weighted Imaging and Susceptibility-Weighted Imaging and Mapping

The cerebral vasculature, along with neurons and axons, is vulnerable to biomechanical insult during traumatic brain injury (TBI). Trauma-induced vascular injury is still an underinvestigated area in TBI research. Cerebral blood flow and metabolism could be important future treatment targets in neural critical care. Magnetic resonance imaging offers a number of key methods to probe vascular injury and its relationship with traumatic hemorrhage, perfusion deficits, venous blood oxygen saturation changes, and resultant tissue damage. They make it possible to image the hemodynamics of the brain, monitor regional damage, and potentially show changes induced in the brain's function not only acutely but also longitudinally following treatment. These methods have recently been used to show that even mild TBI (mTBI) subjects can have vascular abnormalities, and thus they provide a major step forward in better diagnosing mTBI patients.

Increased Number and Distribution of Cerebral Microbleeds Is a Risk Factor for Cognitive Dysfunction in Hemodialysis Patients: A Longitudinal Study

The aim of this study was to explore the risk factors associated with longitudinal changes in hemodialysis patients including the correlation between number and distribution of cerebral microbleeds (CMBs).

Sixty-one hemodialysis patients were enrolled in this prospective study. Twenty-eight patients had follow-up examinations with a mean interval of 24.79 ± 5.17 months. The number of CMBs was manually counted on susceptibility-weighted imaging. Subjects were divided into 2 groups with and without CMBs. In the CMB group, 8 of 33 patients did not have a mini-mental state examination (MMSE) because of blurred vision. Multiple logistic regression was used to investigate the risk factors for CMBs. Partial correlation was used to explore the correlation between the increased number of CMBs and the change of MMSE scores.

CMBs were seen in 33 (54%) hemodialysis patients. Both age and pre/postdialysis systolic blood pressure (SBP) positively correlated with CMBs. Serum iron (SI), and high-density lipoprotein cholesterol (HDL-c) negatively correlated with CMBs (all P < 0.05). Among 25 patients with CMBs and MMSE, 9 patients had scores <27, which was considered as subnormal and most CMBs in these patients were located in the brainstem and basal ganglia. Considering age and follow-up time as the co-confounding factors, the number of new CMBs over the 2 imaging time points negatively correlated with the change of MMSE scores (r = −0.673, P = 0.023).

The presence of new CMBs was a risk factor for cognitive dysfunction and the location of CMBs may be correlated with cognitive impairment. Both SI and HDL-c were protective factors for the CMBs. The risk factors for CMBs included age, pre- and postdialysis SBP.

Oily fish consumption is inversely correlated with cerebral microbleeds in community-dwelling older adults: results from the Atahualpa Project

BACKGROUND

Oily fish is a major dietary source of omega-3 polyunsaturated fatty acids (ω-3 PUFAs). These nutrients improve endothelial dysfunction, reduce β-amyloid induced damage of neurovascular units, and might prevent the occurrence of cerebral microbleeds. However, this relationship has not been investigated so far.

AIM

To evaluate the association between oily fish intake and cerebral microbleeds in a population of frequent fish consumers living in coastal Ecuador.

METHODS

Cerebral microbleeds were identified by gradient-echo MRI and oily fish consumption was calculated in community-dwellers aged ≥60 years enrolled in the Atahualpa Project. The association between cerebral microbleeds and fish servings was examined in regression models adjusted for relevant confounders. A predictive model was constructed using quintiles of fish servings to take into account the non-linearity in the relationship.

RESULTS

Out of 311 eligible individuals, 293 (94 %) were enrolled. Cerebral microbleeds were recognized in 37 (13 %) individuals. Mean fish consumption was 8.8 ± 5.4 servings per week (ω-3 PUFAs estimates: 10.2 ± 7.1 g). Multivariate analysis showed an inverse relationship between cerebral microbleeds and fish consumption (p < 0.001). Predictive margins of CMB were higher for individuals in the lowest (≤4.3) than for those in the highest (≥13.1) quintile of fish servings (17.4 vs 2.3 %, p < 0.001).

CONCLUSIONS

This study shows a lower cerebral microbleed presence among older adults eating large amounts of oily fish (13 servings per week, equivalent to about 15 g of ω-3 PUFAs). These high requirements can be more readily accomplished in other populations by taking fish oil preparations. Longitudinal studies are warranted to assess whether these interventions reduce incident cerebral microbleeds in high-risk individuals.

Cerebral microbleeds in patients with mild cognitive impairment and small vessel disease: The Vascular Mild Cognitive Impairment (VMCI)-Tuscany study

BACKGROUND AND OBJECTIVES

Cerebral microbleeds (CMBs) are a neuroimaging expression of small vessel disease (SVD). We investigated in a cohort of SVD patients with mild cognitive impairment (MCI): 1) the reliability of the Microbleed Anatomical Rating Scale (MARS); 2) the burden and location of CMBs and their association with cognitive performances, independent of other clinical and neuroimaging features.

METHODS

Patients underwent clinical, neuropsychological (4 cognitive domains), and MRI assessments. CMBs were assessed by three raters.

RESULTS

Out of the 152 patients (57.2% males; mean age±SD: 75.5±6.7years) with gradient-echo (GRE) sequences, 41 (27%) had at least one CMB. Inter-rater agreement for number and location of CMBs ranged from good to very good [multi-rater Fleiss kappa (95%CI): 0.70-0.95]. Lacunar infarcts and some clinical variables (e.g., hypertension and physical activity) were associated with CMBs in specific regions. Total number of CMBs and of those in deep and lobar regions were associated with attention/executive and fluency domains.

DISCUSSION

MARS is a reliable instrument to assess CMBs in SVD patients with MCI. Nearly one third of these patients had at least one CMB. Total CMBs burden was associated with attention/executive functions and fluency domains impairment, lacunar infarcts, and with some potentially modifiable risk factors.

Anticoagulation for Atrial Fibrillation in Patients with Cerebral Microbleeds

Intracranial haemorrhage (ICH) is the most feared and devastating complication of oral anticoagulation, with high mortality and disability in survivors. Oral anticoagulant-related ICH is increasing in incidence, most likely in part due to the increased use of anticoagulation for atrial fibrillation in the elderly populations with a high prevalence of bleeding-prone cerebral small vessel diseases. Risk scores have been developed to predict bleeding, including ICH, as well as the risk of ischaemic stroke. Recently, attention has turned to brain imaging, in particular, MRI detection of potential prognostic biomarkers, which may help better predict outcomes and individualize anticoagulant decisions. Cerebral microbleeds (CMBs)--small, round areas of signal loss on blood-sensitive MR sequences--have been hypothesized to be a marker for bleeding-prone small vessel pathology, and thus, future symptomatic ICH risk. In this review, we outline the prevalence and prognostic value of CMBs in populations affected by AF for whom anticoagulation decisions are relevant, including healthy older individuals and survivors of ischaemic stroke or ICH. We consider the limitations of currently available evidence, and discuss future research directions in relation to both prognostic markers and treatment options for atrial fibrillation.

Mapping the landscape of cerebral amyloid angiopathy research: an informetric analysis perspective

To quantitatively analyse the research output and major trends in the field of cerebral amyloid angiopathy (CAA) over six decades, from 1954 to 2014, using advanced informetrics methods, we systematically identified CAA-related articles from PubMed, collected metadata and performed productivity analysis, copublication analysis, and network and content analysis over defined time periods. Linear regression was used to investigate these relationships. Changes in CAA research themes (2000-2014) were defined using a topic modelling technique. A total of 2340 CAA papers were published between 1954 and 2014. The mean number (3.03; 95% CI 2.62 to 3.45; p<0.0001) and mean rate (0.13%; 95% CI 0.11% to 0.15%; p<0.0001) of CAA publications increased yearly. Analysis of copublication networks over 5-year periods from 1990 to 2014, revealed a great increase in the total number of connected investigators publishing on CAA (coefficient 16.74; 95% CI 14 to 19.49; p<0.0001) as well as the interactions between them (coefficient 73.53; 95% CI 52.03 to 89.03; p<0.0001). Further analysis of the network characteristics showed that in the past 15 years, copublication networks became not only larger, but also more connected and coherent. Content analysis identified 16 major CAA research themes and their differential evolution in the past 15 years, with the following main trends: (A) limited focus on vascular cognitive impairment; (B) a shift in emphasis towards neuroimaging, cerebral microbleeds and diagnostic aspects and away from pathological aspects; and (3) a reduced emphasis on basic biology apart from an increased focus on mouse models and perivascular drainage. Our study reveals the rapidly developing nature of the CAA research landscape, providing a novel quantitative and objective basis for identifying unmet needs and new directions. Our findings support the idea of a collaborative culture in the field, encouraging international research initiatives.

Heterogeneous histopathology of cortical microbleeds in cerebral amyloid angiopathy

OBJECTIVE

To investigate the histopathologic substrate of microbleeds detected on 7T postmortem MRI in autopsy cases with severe cerebral amyloid angiopathy (CAA) and Alzheimer pathology.

METHODS

Five decedents (mean age at death 79.6 ± 5.7 years) with documented severe CAA and Alzheimer pathology on standard neuropathologic examination were selected from a local database. Formalin-fixed coronal brain slices were scanned at 7T MRI, including high-resolution T2- and T2*-weighted sequences. Representative microbleeds from each case were sampled for histopathologic analysis, including the presence of blood, blood breakdown products, and markers of ischemic tissue injury.

RESULTS

On MRI, we identified >300 cortical and 4 subcortical microbleeds. Two out of 15 sampled cortical microbleeds corresponded histologically to erythrocytes (suggestive of recent hemorrhages), 4 to vasculopathies (fibrinoid necrosis in 3 and a cavernoma) without substantial parenchymal tissue injury, and 9 to accumulations of iron-positive siderophages without erythrocytes (suggestive of old hemorrhages) combined with mild to moderate degrees of chronic ischemic tissue injury.

CONCLUSIONS

This study provides evidence for heterogeneous pathologic substrates and possibly different pathophysiologic mechanisms underlying MRI-observed cortical microbleeds in the context of advanced CAA and Alzheimer disease.

High Prevalence of Cerebral Microbleeds in Inner City Young Stroke Patients

BACKGROUND

Data on cerebral microbleeds (CMBs) in younger populations are lacking, particularly in young stroke patients. We sought to characterize CMBs in an inner city cohort of young adults with stroke.

METHODS

CMB presence, count, and topography were assessed on magnetic resonance imaging (MRI) scans of 104 young stroke patients (≤49 years) presenting to Boston Medical Center between January 2006 and February 2010. Subsequent MRIs were assessed for the occurrence of new microbleeds in 29 patients. We performed cross-sectional analysis comparing baseline characteristics between patients with and without microbleeds, and between predefined microbleed burden and topography categories. We performed additional analysis to assess the determinants of new microbleeds on repeat MRI.

RESULTS

Microbleeds were present in 17% of the sample. Male sex (odds ratio [OR] 5.7, 95% confidence interval [CI] 1.0-32.6, P = .049), hypertension (OR 6.2, 95% CI 1.2-32, P = .03), moderate-severe white matter hyperintensities on MRI (OR 5.8, 95% CI 1.6-29.0, P = .01), and intracerebral hemorrhage (ICH; OR 5.0, 95% CI 1.2-20, P = .03) were over-represented in patients with microbleeds. Patients who developed new microbleeds on repeat MRI (14%) had higher microbleed counts on baseline MRI (50% versus 0% ≥ 3 CMBs, P = .02), history of illicit drug use (75% versus 24%, P = .08), positive serum toxicology for cocaine (67% versus 13%, P = .11), ICH as their presenting stroke subtype (50% versus 8%, P = .08), and over-representation of moderate-severe white matter hyperintensities (75% versus 20%, P = .05).

CONCLUSIONS

Results from this inner city cohort suggest that microbleeds are prevalent in young stroke patients and are largely associated with modifiable risk factors.

Ischemic brain injury in cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is a common form of cerebral small vessel disease and an important risk factor for intracerebral hemorrhage and cognitive impairment. While the majority of research has focused on the hemorrhagic manifestation of CAA, its ischemic manifestations appear to have substantial clinical relevance as well. Findings from imaging and pathologic studies indicate that ischemic lesions are common in CAA, including white-matter hyperintensities, microinfarcts, and microstructural tissue abnormalities as detected with diffusion tensor imaging. Furthermore, imaging markers of ischemic disease show a robust association with cognition, independent of age, hemorrhagic lesions, and traditional vascular risk factors. Widespread ischemic tissue injury may affect cognition by disrupting white-matter connectivity, thereby hampering communication between brain regions. Challenges are to identify imaging markers that are able to capture widespread microvascular lesion burden in vivo and to further unravel the etiology of ischemic tissue injury by linking structural magnetic resonance imaging (MRI) abnormalities to their underlying pathophysiology and histopathology. A better understanding of the underlying mechanisms of ischemic brain injury in CAA will be a key step toward new interventions to improve long-term cognitive outcomes for patients with CAA.

[Discirculatory encephalopathy and small vessel disease]

The report examines the practicability of the term 'discirculatory encephalopathy' used in the Russian Federation to designate the chronic cerebral ischemia of different origin. The authors discuss the state of small vessel disease which manifests itself through slowly progressive cerebral changes. On the basis of their own research results and literature review the authors conclude that a standardized extract of Ginkgo biloba EGb761 (tanakan) can be effectively used in patients with small vessel disease.

Cerebral microbleeds and postthrombolysis intracerebral hemorrhage risk Updated meta-analysis

OBJECTIVE

We performed a systematic review and meta-analysis to assess whether the presence of cerebral microbleeds (CMBs) on pretreatment MRI scans of patients with acute ischemic stroke treated with thrombolysis is associated with an increased risk of symptomatic intracerebral hemorrhage (ICH).

METHODS

We searched PubMed for relevant studies and calculated pooled odds ratios (ORs) for symptomatic ICH, using the Mantel–Haenszel fixed-effects method, among individuals with vs without CMBs on pretreatment MRI scans. To minimize potential bias, sensitivity analysis was performed including studies providing data on patients treated only with IV thrombolysis.

RESULTS

Ten eligible studies including 2,028 patients were pooled in meta-analysis. The overall prevalence of CMBs was 23.3%. Among patients with CMBs, 40 of 472 (8.5%; 95%confidence interval [CI]: 6.1%–11.4%) experienced a symptomatic ICH after thrombolysis compared with 61 of 1,556 patients (3.9%; 95% CI: 3%–5%) without CMBs. The pooled OR of ICH across all studies was 2.26 (95%CI: 1.46–3.49; p , 0.0001). Eight studies, including 1,704 patients (n 5 401 with CMBs), provided data on patients treated with IV thrombolysis only; OR for the presence of CMBs and the development of symptomatic ICH was 2.87 (95%CI: 1.76–4.69; p , 0.0001).

CONCLUSIONS

Our meta-analysis of the available published data demonstrates an increased risk of symptomatic ICH after thrombolysis for acute ischemic stroke in patients with CMBs. However, we cannot fully exclude bias or confounding, so our results should be considered hypothesis generating. Detecting CMBs should not prevent thrombolytic treatment based on present evidence. Further analyses, taking into account CMB number and location, as well as measures of functional outcome, are needed.

Cerebral microbleeds as a biomarker in Alzheimer's disease? A review in the field

Cerebral microbleeds (CMBs) are a marker of small vessel disease, increasingly recognized as being of importance in the Alzheimer's disease (AD) process. CMBs influence in AD, and its longitudinal impact on disease progression is however still unknown. CMBs show several associations with AD across studies, are associated with decreased cerebrospinal fluid amyloid levels and are related with the ApoE ϵ4 allele, as well as other imaging manifestations typical for small vessel disease. CMBs, in addition to other markers of small vessel disease, are important to discover further in order to discern possible AD phenotypes.

Review And Insights Into The Bleeding Mechanism Incited By Antithrombotic Therapy: Mechanistic Nuances Of Dual Pro-Hemorrhagic Substrate Incorporating Drug-Induced Microvascular Leakage

In patients with atrial fibrillation antithrombotic prophylaxis for stroke is associated with an increased risk of bleeding. Cerebrovascular risk-benefit ratio for oral anticoagulation therapies continues to be debated. Macro and/or microhematomas as well as visible or cryptic ones may appear unexpectedly in any anatomic region. The diagnostic and prognostic value of subcutaneous hematomas (petechia, ecchymosis, bruise) potentially predisposing intracerebral micro- or macrobleeding might be reconsidered. Hypothetically, subcutaneous hemorrhagic events are "transparent" signs and reflect the coexistence of remote vulnerable sites that are potential bleeding sources. Obviously vigilance is needed for early signs of drug-related petechiae evaluation to determine whether it is a local/superficial subtlety or a systemic problem. Any bleeding complication, regardless of its scale and anatomical location, might be treated as a worrisome clinical symptom requiring subtle correction of antithrombotic regimen. The focus of this article is to review the current knowledge of drug-related hemorrhage with special emphasis on underlying mechanisms and links between the visible bleeding (predominantly subcutaneous) and remote (such as cerebral) hemorrhagic sources. To mitigate inappropriate therapy, we should consider new conceptual insights and more individualized approaches to achieve an optimal balance of efficacy and safety. We hypothesize that bleeding complications occur as a result of two factors - impact of antithrombotic drugs and related detrimental effect on microvascular network. Most likely the microvasculature undergoes pro-hemorrhagic medication stress leading to unfavorable vascular wall "fenestration" with ensuing consequences. If so, it suggests the presence of dual substrate responsible for hemorrhagic events.

Risk Factors Associated With Incident Cerebral Microbleeds According to Location in Older People: The Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study

IMPORTANCE

The spatial distribution of cerebral microbleeds (CMBs), which are asymptomatic precursors of intracerebral hemorrhage, reflects specific underlying microvascular abnormalities of cerebral amyloid angiopathy (lobar structures) and hypertensive vasculopathy (deep brain structures). Relatively little is known about the occurrence of and modifiable risk factors for developing CMBs, especially in a lobar location, in the general population of older people.

OBJECTIVE

To investigate whether lifestyle and lipid factors predict new CMBs in relation to their anatomic location.

DESIGN, SETTING, AND PARTICIPANTS

We enrolled 2635 individuals aged 66 to 93 years from the population-based Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study in a brain imaging study. Participants underwent a baseline magnetic resonance imaging (MRI) examination of the brain from September 1, 2002, through February 28, 2006, and returned for a second MRI examination from April 1, 2007, through September 30, 2011.

EXPOSURES

Lifestyle and lipid factors assessed at baseline included smoking, alcohol consumption, body mass index, and serum levels of total cholesterol, high- and low-density lipoprotein cholesterol, and triglycerides.

MAIN OUTCOMES AND MEASURES

Incident CMBs detected on MRIs, which were further categorized as exclusively lobar or as deep.

RESULTS

During a mean follow-up of 5.2 years, 486 people (18.4%) developed new CMBs, of whom 308 had lobar CMBs only and 178 had deep CMBs. In the multivariate logarithm-binomial regression model adjusted for baseline cardiovascular risk factors, including blood pressure, antihypertensive use, prevalent CMBs, and markers of cerebral ischemic small-vessel disease, heavy alcohol consumption (vs light to moderate consumption; relative risk [RR], 2.94 [95% CI, 1.23-7.01]) was associated with incident CMBs in a deep location. Baseline underweight (vs normal weight; RR, 2.41 [95% CI, 1.21-4.80]), current smoking (RR, 1.47 [95% CI, 1.11-1.94]), an elevated serum level of high-density lipoprotein cholesterol (RR per 1-SD increase, 1.13 [95% CI, 1.02-1.25]), and a decreased triglyceride level (RR per 1-SD decrease in natural logarithm-transformed triglyceride level, 1.17 [95% CI, 1.03-1.33]) were significantly associated with an increased risk for lobar CMBs exclusively but not for deep CMBs.

CONCLUSIONS AND RELEVANCE

Lifestyle and lipid risk profiles for CMBs were similar to those for symptomatic intracerebral hemorrhage and differed for lobar and deep CMBs. Modification of these risk factors could have the potential to prevent new-onset CMBs, particularly those occurring in a lobar location.

Antiplatelet Drug Use and Cerebral Microbleeds: A Meta-analysis of Published Studies

BACKGROUND

Antiplatelet therapy is a potential risk factor for intracerebral hemorrhage, and cerebral microbleeds reflect small perivascular hemorrhages without clinical symptoms. The question regarding whether antiplatelet therapy increases the risk of cerebral microbleeds has not yet reached a consensus.

METHODS

We conducted a search in English database and extracted data from studies assessing the relationship between antiplatelet therapy and cerebral microbleeds. Then, we adopted the Review Manager 5.2 package to calculate pooled odds ratios (ORs) with the method of the inverse variance.

RESULTS

We pooled data from 11 studies involving 10429 participants. The results revealed that there was a significant association between antiplatelet therapy and cerebral microbleeds in hemorrhagic stroke patients (OR, 1.96; 95% confidence interval [CI], 1.22-3.16) and ischemic stroke patients (OR, 1.65; 95% CI, 1.06-2.59), but not stroke-free population (OR, 1.30; 95% CI, .96-1.74). When stratified by population ethnicity, the association between antiplatelet therapy and cerebral microbleeds was significant in hemorrhagic stroke (OR, 2.26; 95% CI, 1.25-4.08) and ischemic stroke (OR, 2.18; 95% CI, 1.02-4.67) patients from Asian countries, but not significant in hemorrhagic stroke (OR, 1.95; 95% CI, .33-11.37) and ischemic stroke (OR, 1.16; 95% CI, .87-1.54) patients from European countries.

CONCLUSIONS

Antiplatelet therapy may increase the risk of cerebral microbleeds in stroke population. In addition, the relationship between antiplatelet therapy and cerebral microbleeds may be influenced by ethnic factors. More and larger prospective studies are urgently required to verify our results, because the studies to date are retrospective and the available data are limited.

The Clinical Relevance of Microbleeds in Stroke study (CROMIS-2): rationale, design, and methods

BACKGROUND AND RATIONALE

The increasing use of oral anticoagulants, mostly to prevent ischemic stroke due to atrial fibrillation in an ageing population, has been associated with a fivefold increased incidence of oral anticoagulant-associated intracerebral hemorrhage: a rare, serious, and unpredictable complication. We hypothesize that cerebral microbleeds and other markers of cerebral small vessel disease on magnetic resonance imaging, and genetic polymorphisms (e.g. influencing cerebral small vessel integrity or anticoagulation stability), are associated with an increased risk of oral anticoagulant-associated intracerebral hemorrhage, with potential to improve risk prediction.

AIMS

(1) To determine the incidence, clinical, radiological, and genetic associations of oral anticoagulant-associated intracerebral hemorrhage in a prospective, multicentre cohort study of patients with atrial fibrillation-related ischemic stroke or transient ischemic attack started on oral anticoagulants; (2) To investigate characteristics of oral anticoagulant-associated intracerebral hemorrhage compared with non-oral anticoagulants related intracerebral hemorrhage in a prospective study.

DESIGN AND METHODS

Study 1: Prospective, multicentre, inception cohort study of 1425 adults started on oral anticoagulants (including vitamin K antagonists and the nonvitamin K oral anticoagulants) after recent ischemic stroke and concurrent atrial fibrillation. Participants will have standardized brain magnetic resonance imaging (including a T2*-weighted gradient-recalled echo sequence) and DNA sample collection at baseline, with two-year follow-up by postal questionnaire and medical records surveillance for symptomatic intracranial hemorrhage, other serious vascular events, and death. We will compare the rates of symptomatic intracranial hemorrhage (primary outcome; subclassified as intracerebral, subdural, extradural, intraventricular), other vascular events, and death (secondary outcomes) in participants with one or more cerebral microbleeds to the rates in those without cerebral microbleeds.

STUDY

Prospective case-control study of oral anticoagulant-associated intracerebral hemorrhage compared with non-oral anticoagulant-associated intracerebral hemorrhage to investigate genetic, clinical, and radiological associations with oral anticoagulant-associated intracerebral hemorrhage. In participants with intracerebral hemorrhage (including at least 300 with oral anticoagulant-associated intracerebral hemorrhage), we will collect a DNA sample, standardized clinical data and routine brain imaging (magnetic resonance imaging or computed tomography), and information on functional outcome.

EXPECTED OUTCOMES

We will identify the factors associated with increased intracranial hemorrhage risk after oral anticoagulants for secondary prevention after ischemic stroke due to atrial fibrillation. We will determine clinical, radiological and genetic factors, and clinical outcomes associated with oral anticoagulant-associated intracerebral hemorrhage.

Population-Based Study of Cerebral Microbleeds in Stroke-Free Older Adults Living in Rural Ecuador: The Atahualpa Project

BACKGROUND AND PURPOSE

Prevalence of cerebral microbleeds (CMB) in white and Asian populations range from 4% to 15%. However, there is no information from indigenous Latin American people. We aimed to assess prevalence and cerebrovascular correlates of CMB in stroke-free older adults living in rural Ecuador.

METHODS

Of 311 Atahualpa residents aged ≥60 years identified during a door-to-door survey, 258 (83%) underwent brain magnetic resonance imaging. Twenty-one were further excluded for a diagnosis of overt stroke. Using multivariate logistic regression models, adjusted for demographics and cardiovascular risk factors, we evaluated whether CMB were independently associated with silent strokes, white matter hyperintensities, and global cortical atrophy.

RESULTS

Twenty-six (11%) of 237 participants had CMB, which were single in 54% of cases. CMB were deep in 11 patients, cortical in 9, and located both deep and cortical in 6. In univariate analyses, CMB were associated with age, systolic blood pressure, moderate-to-severe white matter hyperintensities, silent lacunar infarcts, and cortical atrophy. Mean (±SD) values for systolic blood pressure were 155±27 mm Hg in patients who had CMB versus 142±26 mm Hg in those who did not (P=0.017). In the adjusted models, moderate-to-severe white matter hyperintensities (P=0.009), silent lacunar infarcts (P=0.003), and global cortical atrophy (P=0.04) were independently associated with CMB.

CONCLUSIONS

Prevalence of CMB in stroke-free older adults living in Atahualpa is comparable with those reported from other ethnic groups. There is a strong relationship between CMB and increased age, high systolic blood pressure, silent markers of cerebral small vessel disease, and cortical atrophy.