MRI Detection of New Microbleeds in Patients With Ischemic Stroke

Cerebral microbleeds: a new dilemma in stroke medicine

Cerebral microbleeds (CMBs) are an increasingly common neuroimaging finding in the context of ageing, cerebrovascular disease and dementia, with potentially important clinical relevance. Perhaps the most pressing clinical question is whether CMBs are associated with a clinically important increase in the risk of intracerebral haemorrhage (ICH), the most feared complication in patients treated with thrombolytic or antithrombotic (antiplatelet and anticoagulant) drugs. This review will summarize the evidence available regarding CMBs as an indicator of future ICH risk in stroke medicine clinical practice.

Cerebral microbleeds on magnetic resonance imaging and anticoagulant-associated intracerebral hemorrhage risk

The increasing use of antithrombotic drugs in an aging population [including anticoagulants to prevent future ischemic stroke in individuals with atrial fibrillation (AF)] has been associated with a dramatic increase in the incidence of intracerebral hemorrhage (ICH) in users of antithrombotic drugs. Several lines of evidence suggest that cerebral small vessel disease (particularly sporadic cerebral amyloid angiopathy) is a risk factor for this rare but devastating complication of these commonly used treatments. Cerebral microbleeds (CMBs) have emerged as a key MRI marker of small vessel disease and a potentially powerful marker of future ICH risk, but adequately powered, high quality prospective studies of CMBs and ICH risk on anticoagulation are not available. Further data are urgently needed to determine how neuroimaging and other biomarkers may contribute to individualized risk prediction to make anticoagulation as safe and effective as possible. In this review we discuss the available evidence on cerebral small vessel disease and CMBs in the context of antithrombotic treatments, especially regarding their role as a predictor of future ICH risk after ischemic stroke, where risk-benefit judgments can be a major challenge for physicians. We will focus on patients with AF because these are frequently treated with anticoagulation. We briefly describe the rationale and design of a new prospective observational inception cohort study (Clinical Relevance of Microbleeds in Stroke; CROMIS-2) which investigates the value of MRI markers of small vessel disease (including CMBs) and genetic factors in assessing the risk of oral anticoagulation-associated ICH.

Intracerebral hemorrhage in the oldest old: a population-based study (vantaa 85+)

Aims: Very elderly subjects represent the fastest growing population in the world. Most of the recent studies on intracerebral hemorrhage (ICH) have been carried out on younger patients and/or preferably using novel radiological techniques. We investigated the prevalence, risk factors, and histopathological characteristics of the ICH in the oldest old. Materials and methods: The brains of 300 autopsied individuals (248 females, 52 males, mean age at death 92.4 ± 3.7 years) were investigated as part of the prospective population-based Vantaa 85+ study. After macroscopic investigation, the presence and extent of microscopic brain hemorrhages (MH) were analyzed by counting the number of iron containing macrophages (siderophages) by Prussian blue staining. Deposits with >5 siderophages were defined as MH+, forming a subgroup of MH. Genotyping of apolipoprotein E (APOE) and the analysis of microscopic (MI) or larger infarctions and cerebral amyloid angiopathy (CAA) were performed using standardized methods. Regression analysis was used to predict the presence of ICH, with and without co-localized CAA, and was adjusted for age at death and gender. Results: The prevalence of macroscopic ICH was 2.3% in total; consisting of 1% large lobar hemorrhage (LH), 1% deep hemorrhage (DH), and 0.3% of subarachnoid hemorrhage (SAH). 62% had MH and 15.3% MH+. All MH+ lesions were found to be >2 mm wide. 55.9% of subjects with MH and 81.2% of those with MH+ showed MH/MH+ and CAA in the same brain region (MHCAA and MH+CAA, respectively). MH was associated with none of the neuropathological or clinical conditions, nor with the APOE carrier status. The subjects with MH+, MHCAA or MH+CAA carried the APOE ε4 allele more frequently than controls (OR 3.681, 3.291, 7.522, respectively). Siderophages in MH+CAA co-localized with CAA and with two-thirds of the MI in the tissue sections. Conclusion: Macroscopic ICH was rare in the very elderly. MH was frequent and clinically insignificant. MH+ was rare but closely related with the APOE ε4 genotype and the presence of severe CAA and infarction.

Cerebral microbleeds after use of extracorporeal membrane oxygenation in children

Cerebral microbleeds (CMB) on gradient-recalled echo (GRE) magnetic resonance imaging (MRI) are rarely seen in children, yet have been described following vascular procedures in adults. Extracorporeal membrane oxygenation (ECMO) has been associated with vascular injury and neurological events in children, but there have been no reports to date of GRE MRI findings in children treated with ECMO. We reviewed MRI scans for all vascular neurology consultations in children treated with ECMO at an academic medical center over a 5-year period. In 6 of 12 cases, GRE was acquired as others were unstable or had contraindications to MRI. All 6 of 6 (100%) GRE cases (mean age 2.1 years, 7 female, 5 male) demonstrated CMB. CMB were multiple (>3 lesions), situated in cortical or lobar regions, with a striking predominance (5/6 cases) for the right carotid distribution. Other than CMB, no cases demonstrated intracranial hemorrhage. CMB may be noted on GRE MRI after ECMO and may reflect vascular damage from gaseous emboli.

Amyloid-related imaging abnormalities in amyloid-modifying therapeutic trials: recommendations from the Alzheimer's Association Research Roundtable Workgroup

Amyloid imaging related abnormalities (ARIA) have now been reported in clinical trials with multiple therapeutic avenues to lower amyloid-β burden in Alzheimer's disease (AD). In response to concerns raised by the Food and Drug Administration, the Alzheimer's Association Research Roundtable convened a working group to review the publicly available trial data, attempts at developing animal models, and the literature on the natural history and pathology of related conditions. The spectrum of ARIA includes signal hyperintensities on fluid attenuation inversion recoverysequences thought to represent "vasogenic edema" and/or sulcal effusion (ARIA-E), as well as signal hypointensities on GRE/T2* thought to represent hemosiderin deposits (ARIA-H), including microhemorrhage and superficial siderosis. The etiology of ARIA remains unclear but the prevailing data support vascular amyloid as a common pathophysiological mechanism leading to increased vascular permeability. The workgroup proposes recommendations for the detection and monitoring of ARIA in ongoing AD clinical trials, as well as directions for future research.

Dynamic temporal change of cerebral microbleeds: long-term follow-up MRI study

Background

Cerebral microbleeds (MBs) are understood as an important radiologic marker of intracerebral hemorrhage. We sought to investigate the temporal changes of MBs and clinical factors associated with the changes using long-term follow-up MRI.

Methods/Principal Findings

From October 2002 to July 2006, we prospectively enrolled patients with stroke or transient ischemic attack, and followed-up their brain MRIs with an interval >12 mo. We compared demographic factors, vascular risk factors, laboratory findings, and radiologic factors according to the presence or changes of MBs. A total of 224 patients successfully completed the follow-up examinations (mean, 27 months). Newly developed MBs were noted in 10 patients (6.8%) among those without MBs at baseline (n = 148), and in those with MBs at baseline (n = 76), the MB count had decreased in 11 patients (14.5%), and increased in 41 patients (53.9%). The estimated annual rate of change of MB numbers was 0.80 lesions per year in all patients, a value which became greater in those patients who exhibited MBs at baseline (MBs≥5, 5.43 lesions per year). Strokes due to small vessel occlusion and intracerebral hemorrhage, as well as white matter lesions were independently associated with an increased MB count, whereas the highest quartile of low-density lipoprotein (LDL) cholesterol was associated with a decreased MB count.

Conclusion

During the follow-up period, most of MBs showed dynamic temporal change. Symptomatic or asymptomatic small vessel diseases appear to act as risk factors while in contrast, a high level of LDL cholesterol may act as a protective factor against MB increase.

Cerebral microbleeds: detection, mechanisms and clinical challenges

In the last decade or so, cerebral microbleeds (CMBs) – tiny perivascular hemorrhages seen as small, well-demarcated, hypointense, rounded lesions on MRI sequences that are sensitive to magnetic susceptibility – have generated increasing interest among neurologists and clinical stroke researchers. As MRI techniques become more sophisticated, CMBs are increasingly detected in various patient populations (including all types of stroke, Alzheimer’s disease and vascular cognitive impairment) and healthy community-dwelling older people. Their presence raises many clinical dilemmas and intriguing pathophysiological questions. CMBs are emerging as an important new manifestation and diagnostic marker of cerebral small-vessel disease. They are a potential predictor of future intracerebral hemorrhage risk, a possible contributor to cognitive impairment and dementia and a potential key link between vascular and degenerative pathologies. In this article, we discuss the available pathological, neuroimaging and clinical studies in the field, and we provide a modern overview of the clinical and pathophysiological implications of CMBs in different disease settings.

Magnetic resonance imaging in cerebral small vessel disease and its use as a surrogate disease marker

Cerebral small vessel disease is an important cause of vascular cognitive impairment and dementia. On brain imaging, discrete lacunar infarcts and/or more diffuse regions of white matter hyperintensities or leucoaraiosis are seen. Magnetic resonance imaging plays a crucial role in diagnosis, and advanced magnetic resonance imaging techniques are providing new information on disease mechanisms and offering potential as surrogate disease markers. Longitudinal studies have demonstrated detectable progression of lesion load over short time periods, and weak correlations with cognition. Stronger correlations with cognition have been found with diffusion tensor imaging, which is more sensitive to white matter tract structure, supporting a role for disconnection in the pathogenesis of cognitive impairment. Brain volume also consistently correlates with cognition in asymptomatic small vessel disease, sporadic small vessel disease, and Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy. Gradient echo magnetic resonance imaging identifies microbleeds in a significant proportion of patients with small vessel disease, although their role in clinical management remains to be determined. Surrogate markers to monitor disease progression and evaluate new therapies would have major clinical use. The greater sensitivity of diffusion tensor imaging parameters and brain volume to change, and the stronger correlation of these parameters with cognition, suggest that they may be more powerful surrogates. However, data from longitudinal and intervention studies are required to determine if this is indeed the case. In this systematic review, we describe the use of both conventional and advanced magnetic resonance imaging techniques in patient groups with the full spectrum of clinical small vessel disease, from normal populations with WMH to patients groups with lacunar stroke and dementia.

Brain microbleeds: more evidence, but still a clinical dilemma

PURPOSE OF REVIEW

Brain microbleeds (BMBs) are a radiological construct that is meant to represent a specific underlying microscopic pathology: perivascular collections of hemosiderin deposits. BMBs may represent two different types of underlying vasculopathies: hypertensive vasculopathy and cerebral amyloid angiopathy. This brief review highlights some recent works discussing their nature, and both their diagnostic and prognostic values.

RECENT FINDINGS

The improvement of detection techniques has modified our perception of BMBs prevalence, which can reach 35% among healthy people compared with 5% when conventional techniques are used. Our knowledge on BMBs is evolving very quickly. The careful study of their anatomical distribution sheds light on their histological significance: deep BMBs may represent hypertensive vasculopathies and lobar ones cerebral amyloid angiopathy.

SUMMARY

Despite an explosion of publications on BMBs, their diagnostic and prognostic values have only received indirect support and remain to be explored. To date, BMBs should not contraindicate antithrombotic treatment in settings wherein benefits have clearly been demonstrated in clinical trials and meta-analyses. One intriguing field is Alzheimer's disease, in which BMBs may be a missing link between two important theories on the neuropathogenesis of Alzheimer's disease: the amyloid cascade hypothesis and the vascular hypothesis.