Asymptomatic cerebral microbleeds seen in healthy subjects have a strong association with asymptomatic lacunar infarction

Preliminary evidence of high prevalence of cerebral microbleeds in astronauts with spaceflight experience

Long-duration spaceflight poses a variety of health risks to astronauts, largely resulting from extended exposure to microgravity and radiation. Here, we assessed the prevalence and incidence of cerebral microbleeds in sixteen astronauts before and after a typical 6-month mission on board the International Space Station Cerebral microbleeds are microhemorrhages in the brain, which are typically interpreted as early evidence of small vessel disease and have been associated with cognitive impairment. We identified evidence of higher-than-expected microbleed prevalence in astronauts with prior spaceflight experience. However, we did not identify a statistically significant increase in microbleed burden up to 7 months after spaceflight. Altogether, these preliminary findings suggest that spaceflight exposure may increase microbleed burden, but this influence may be indirect or occur over time courses that exceed 1 year. For health monitoring purposes, it may be valuable to acquire neuroimaging data that are able to detect the occurrence of microbleeds in astronauts following their spaceflight missions.

Nomogram based on clinical and brain computed tomography characteristics for predicting more than 5 cerebral microbleeds in the hypertensive population

Background

Cerebral microbleeds (CMBs) are common in the hypertensive population and can only be detected with magnetic resonance imaging (MRI). The anticoagulation and thrombolytic regimens for patients with >5 CMBs are different from those for patients with ≤ 5 CMBs. However, MRI is not suitable for evaluating CMBs in patients with MRI contraindications or acute ischemic stroke urgently requiring thrombolysis. We aimed to develop and validate a nomogram combining clinical and brain computed tomography (CT) characteristics for predicting >5 CMBs in a hypertensive population.

Materials and methods

In total, 160 hypertensive patients from 2016 to 2020 who were confirmed by MRI to have >5 (77 patients) and ≤ 5 CMBs (83) were retrospectively analyzed as the training cohort. Sixty-four hypertensive patients from January 2021 to February 2022 were included in the validation cohort. Multivariate logistic regression was used to evaluate >5 CMBs. A combined nomogram was constructed based on the results, while clinical and CT models were established according to the corresponding characteristics. Receiver operating characteristic (ROC) and calibration curves and decision curve analysis (DCA) were used to verify the models.

Results

In the multivariable analysis, the duration of hypertension, level of homocysteine, the number of lacunar infarcts (LIs), and leukoaraiosis (LA) score were included as factors associated with >5 CMBs. The clinical model consisted of the duration of hypertension and level of homocysteine, while the CT model consisted of the number of LIs and LA. The combined model consisted of the duration of hypertension, level of homocysteine, LI, and LA. The combined model achieved an area under the curve (AUC) of 0.915 (95% confidence interval [CI]: 0.860–0.953) with the training cohort and 0.887 (95% CI: 0.783–0.953) with the validation cohort, which were higher than those of the clinical model [training cohort: AUC, 0.797 (95% CI: 0.726, 0.857); validation cohort: AUC, 0.812 (95% CI: 0.695, 0.899)] and CT model [training cohort: AUC, 0.884 (95% CI: 0.824, 0.929); validation cohort: AUC, 0.868 (95% CI: 0.760, 0.940)]. DCA showed that the clinical value of the combined model was superior to that of the clinical model and CT model.

Conclusion

A combined model based on clinical and CT characteristics showed good diagnostic performance for predicting >5 CMBs in hypertensive patients.

[A Method for Evaluating the T2∗-weighting Effect in MRI]

PURPOSE

To propose a method for evaluating the T₂*-weighting effect in MRI.

METHODS

Multiple solutions with different concentrations of a superparamagnetic iron oxide contrast agent were made and their signal intensities on T₂*-weighted images were measured. The relationship between iron concentration and signal intensity was determined, and we simulated an iron concentration map representing a simplified model of a brain microbleed and converted the pixel values in the map to signal intensity based on the determined relationship, generating a simulated T₂*-weighted image. An 'S-value' parameter was defined to evaluate the low-intensity regions in the simulated image. S-values were obtained using T₂*-weighted sequences acquired with different echo time (TE) values on three MRI scanners (Philips 1.5 T, GE 3.0 T, and Siemens 3.0 T). Another parameter (A-value) defined by the American Society for Testing and Materials (ASTM-F2119) for assessing artifacts was applied to evaluate the weighting effect in the T₂*-weighted image of a laboratory-made susceptibility-effect phantom.

RESULTS

With all three scanners, the S-values increased as the TE increased, indicating enhancement of the T₂*-weighting effect. For every TE, the S-values obtained for the Philips scanner were the largest, followed by those for the GE and Siemens scanners. The results of this comparative evaluation were similar to those obtained using A-values.

CONCLUSION

Comparisons with the established A-value parameter showed our proposed method for the quantitative evaluation of the T₂*-weighting effect using S-values to be valid. The proposed method has the advantage that the S-values do not depend on a specific susceptibility-effect phantom.

Cerebral microbleeds are associated with blood pressure levels in individuals with hypertension

Objective: Cerebral microbleeds (CMBs), which appear as small dot-like hypointense lesions, are strongly associated with cerebrovascular disease. Recently, numerous investigations have suggested that hypertension and age are risk factors for CMBs; however, whether blood pressure grade and age rank are related to the severity of CMBs remains unclear. The purpose of this research was to assess the association between cerebral microbleeds and blood pressure levels.Methods: In total, 460 consecutive hypertension patients (214 males and 246 females; aged 44-96 years, mean age 60.95 ± 6.82 years) from Lishui Central Hospital were enrolled and classified as CMB or non-CMB patients according to magnetic resonance imaging (MRI). Gradient echo T2*-weighted MRI was used to detect CMBs. Differences in blood pressure, CMB severity, and other patient characteristics were compared between the two groups. Multifactorial logistic regression was used to analyze the correlation between blood pressure and microbleeds.Results: In our study, CMB lesions were identified in 123 patients (26.7%), including 39 patients with CMB lesions located deep in the brain. In the hypertensive population, smoking is an independent risk factor for CMBs. Additionally, systolic blood pressure (SBP), diastolic blood pressure (DBP) and age are also independent risk factors for CMBs. Furthermore, a modest correlation was noted between the number of microbleeds and grade of hypertension.Conclusions: This study provides novel evidence that microbleed severity is associated with hypertension grade. This conclusion emphasizes the importance of antihypertensive therapy in hypertension patients to avoid an increase in CMBs.

Increased prevalence of cerebral microbleeds in patients with low left ventricular systolic function

Gradient-echo T2-star (T2*)-weighted magnetic resonance imaging (MRI) is a sensitive method to detect cerebral microbleeds (CMBs). The presence of CMBs was reported to be a marker of future cardiovascular mortality and is associated with various cardiovascular risk factors, use of antithrombotic drugs, and cognitive dysfunction. However, the relationship between cardiac function and CMBs remains unclear. We investigated the association between cardiac function and presence of CMBs in patients with cardiovascular diseases. This single-center retrospective study included a total of 424 participants (mean age 70 ± 12 years; men 286 (67%); mean left ventricular ejection fraction (LVEF) 61% ± 12%] who underwent echocardiography and brain T2*-weighted MRI within 1 month without neurologic abnormality. CMBs were found in 118 (28%) patients. There was no significant relationship between CMBs and anticoagulant or antiplatelet therapy. LVEF was significantly lower in patients with CMBs than in those without CMBs (59% ± 13% vs. 62% ± 11%, P < 0.05). On multivariate logistic analysis, lower LVEF [odds ratio (OR) 0.98, 95% confidence interval (CI) 0.96-1.00; P < 0.05] and age (OR 1.02, 95% CI 1.00-1.05; P < 0.05) were significantly associated with CMBs. The presence of CMBs was frequently observed in the patients with cardiovascular disease and was significantly associated with age and LVEF.

The study on analysis of risk factors for severity of white matter lesions and its correlation with cerebral microbleeds in the elderly with lacunar infarction

This study aimed to explore the risk factors for severity of white matter lesions and its correlation with in the elderly with lacunar infarction.Patients (range, 70-85 years) with lacunar infarction treated in a hospital in China from 2016 to 2017were enrolled. Fazekas rating scale (0-6 points) was used to assess severity of white matter lesions. Risk factors for the severity of white matter lesions and correlation between cerebral microbleeds and white matter lesions in the elderly with lacunar infarction were studied.The elderly (81-85 years' old, odds ratio [OR]: 2.423, 95% confidence interval [CI]: 1.795-3.271, P = .018; 76∼80 years' old, OR: 3.113, 95% CI: 1.723-5.625, P = .043), carotid atherosclerosis (OR: 3.062, 95% CI:1.715-5.468, P < .001), history of hypertension (OR: 3.694, 95% CI: 2.031-6.717, P < .001) were risk factors for the severity of white matter lesions. The white matter lesions score increased corresponding to increase in the cerebral microbleeds grade (P < .001). The white matter lesions score was higher in the cerebral microbleeds combined with the white matter lesions group than in the white matter lesions group (P < .01). After correcting the effects of age, there was a correlation between white matter lesions and cerebral microbleeds (P < .001). Logistic analysis revealed that the patients' age (81-85 years' old, OR: 2.722, 95% CI: 1.985-3.734, P = .019; 76∼80 years' old, OR: 1.857, 95% CI: 1.075-3.207, P = .031), history of hypertension (OR: 2.931, 95% CI: 1.136-7.567, P = 0.0.036), systolic blood pressure (OR: 1.049, 95% CI: 1.015-1.084, P = .007), high-sensitivity C-reactive protein (OR: 1.504, 95% CI: 1.254-1.803, P < .001), homocysteine (OR: 1.076, 95% CI: 1.020-1.136, P = .009), and carotid atherosclerosis (OR: 1.389, 95% CI: 1.103-1.748, P = .010) were significant risk factors for combined cerebral microbleeds with white matter lesions in patients with lacunar infarction.The elderly, carotid atherosclerosis, history of hypertension were risk factors for the severity of white matter lesions. Cerebral microbleeds were positively correlated with the severity of white matter lesions.

Subclinical Cerebrovascular Disease: Epidemiology and Treatment

PURPOSE OF REVIEW

Subclinical cerebrovascular disease (sCVD) is highly prevalent in older adults. The main neuroimaging findings of sCVD include white matter hyperintensities and silent brain infarcts on T2-weighted MRI and cerebral microbleeds on gradient echo or susceptibility-weighted MRI. In this paper, we will review the epidemiology of sCVD, the current evidence for best medical management, and future directions for sCVD research.

RECENT FINDINGS

Numerous epidemiologic studies show that sCVD, in particular WMH, is an important risk factor for the development of dementia, stroke, worse outcomes after stroke, gait instability, late-life depression, and death. Effective treatment of sCVD could have major consequences for the brain health of a substantial portion of older Americans. Despite the link between sCVD and many vascular risk factors, such as hypertension or hyperlipidemia, the optimal medical treatment of sCVD remains uncertain. Given the clinical equipoise about the risk versus benefit of aggressive medical management for sCVD, clinical trials to examine pragmatic, evidence-based approaches to management of sCVD are needed. Such a trial could provide much needed guidance on how to manage a common clinical scenario facing internists and neurologists in practice.

Deep cerebral microbleeds are associated with the severity of lacunar infarcts and hypertension: A retrospective analysis

Cerebral microbleeds (CMBs) and lacunar infarcts are common manifestations of cerebral small vessel disease. However, the association between the location of CMBs and lacunar infarcts is unclear. Our study aimed to clarify the relationship between the location of CMBs and lacunar infarcts.This study retrospectively analyzed 166 patients with ischemic stroke or transient ischemic attacks admitted in the Geriatric Neurology Department of Chinese PLA General Hospital between February 2010 and December 2012. We collected clinical characteristics and risk factors of CMBs. The location of CMBs on T2*-weighted angiography was assessed by the Microbleed Anatomical Rating Scale. The number of lacunar infarcts and the severity of white matter hyperintensities were also recorded. The association between the location of CMBs and lacunar infarcts parameters was examined.CMBs were present in 77 (46.4%) patients. The presence [odds ratios (OR), 2.14; 95% confidence interval (CI), 1.02-4.48], number (OR, 1.17; 95% CI, 1.02-1.36 per lesion), severity (OR, 1.61; 95% CI, 1.07-2.42) of lacunar infarcts, and hypertension (OR, 5.76; 95% CI, 2.01-16.55) were independent risk factors for CMBs. Stratified by the location of CMBs, lobar CMBs and infratentorial CMBs did not show significant association with lacunar infarcts. Deep CMBs were significantly associated with the number (OR 1.18, 95% CI 1.03-1.36) and severity (OR 1.71, 95% CI 1.11-2.63) of lacunar infarcts. Moreover, the percentage of deep CMBs increased with the increased severity of lacunar infarcts (P = .003).Deep CMBs rather than lobar and infratentorial CMBs are associated with lacunar infarcts.

Prevalence of and risk factors for cerebral microbleeds in a general Japanese elderly community

Background

We investigated the prevalence of and risk factors for cerebral microbleeds (CMBs) in a cross-sectional study of a general population of Japanese elderly.

Methods

In 2012, brain MRI scanning at 1.5T and comprehensive health examination were conducted for 1281 residents aged 65 years or older. CMBs were defined as ovoid hypointensity lesions less than 10 mm in diameter on T2*-weighted images and classified into deep/infratentorial or lobar CMBs. Age- and sex-specific and overall prevalence of CMBs were estimated, and the associations of traditional cardiovascular risk factors and APOE polymorphism with the presence of CMBs were examined using a logistic regression analysis.

Results

The crude prevalences of total, deep/infratentorial, and lobar CMBs were 18.7% (n = 240), 13.5% (n = 173), and 9.6% (n = 123), respectively. The prevalence of total CMBs was 23.0% in men and 15.5% in women and increased with aging in both sexes (both p for trend <0.01). Hypertension was significantly associated with the presence of both deep/infratentorial and lobar CMBs. Lower serum total cholesterol was a significant risk factor for deep/infratentorial CMBs, but not for lobar CMBs, while APOE ε4 carriers had a significantly higher likelihood only of lobar CMBs compared with noncarriers.

Conclusions

Our study suggests that approximately 1 of 5 Japanese elderly people have CMBs, and that risk factors for deep/infratentorial and lobar CMBs are different, indicating the distinct pathologic backgrounds of these lesions.

Frequency, Risk Factors, and Outcome of Coexistent Small Vessel Disease and Intracranial Arterial Stenosis: Results From the Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) Trial

IMPORTANCE

Intracranial arterial stenosis (ICAS) and small vessel disease (SVD) may coexist. There are limited data on the frequency and risk factors for coexistent SVD and the effect of SVD on stroke recurrence in patients receiving medical treatment for ICAS.

OBJECTIVE

To investigate the frequency and risk factors for SVD and the effect of SVD on stroke recurrence in patients with ICAS.

DESIGN, SETTING, AND PARTICIPANTS

A post hoc analysis of the Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) study, a prospective, multicenter clinical trial. Among 451 participants, 313 (69.4%) had baseline brain magnetic resonance imaging scans read centrally for SVD that was defined by any of the following: old lacunar infarction, grade 2 to 3 on the Fazekas scale (for high-grade white matter hyperintensities), or microbleeds. Patient enrollment in SAMMPRIS began November 25, 2008, and follow-up ended on April 30, 2013. Data analysis for the present study was performed from May 13, 2014, to July 29, 2015.

MAIN OUTCOMES AND MEASURES

Risk factors in patients with vs without SVD and the association between SVD and other baseline risk factors with any ischemic stroke and ischemic stroke in the territory of the stenotic artery determined using proportional hazards regression.

RESULTS

Of 313 patients, 155 individuals (49.5%) had SVD noted on baseline magnetic resonance imaging. Variables that were significantly higher in patients with SVD, reported as mean (SD), included age, 63.5 (10.5) years (P < .001), systolic blood pressure, 149 (22) mm Hg (P < .001), glucose level, 130 (50) mg/dL (P = .03), and lower Montreal Cognitive Assessment scores (median, ≥24 [interquartile range, 20-26]; P = .02).Other significant variables were the number of patients with diabetes mellitus (88 of 155 [56.8%]; P = .003), coronary artery disease (46 [29.7%]; P = .004), stroke before the qualifying event (59 [38.1%]; P < .001), old infarct in the territory of the stenotic intracranial artery (88 [56.8%]; P < .001), and receiving antithrombotic therapy at the time of the qualifying event (109 [70.3%]; P = .005). The association between SVD and any ischemic stroke was nearly significant in the direction of a higher risk (18 [23.7%]); P = .07) for patients with SVD. On bivariate analysis, SVD was not associated with an increased risk on multivariable analyses (hazard ratio, 1.7 [95% CI, 0.8-3.8]; P = .20). In addition, SVD was not associated with an increased risk of stroke in the territory on either bivariate or multivariable analyses.

CONCLUSIONS AND RELEVANCE

Although SVD is common in patients with ICAS, the presence of SVD on baseline magnetic resonance imaging is not independently associated with an increased risk of stroke in patients with ICAS.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00576693.

Cerebral microbleeds in a multiethnic elderly community: demographic and clinical correlates

BACKGROUND

Microbleeds, small perivascular collections of hemosiderin manifested radiologically as hypointensities on gradient-echo magnetic resonance imaging (MRI), are important markers of small vessel pathology. Despite their clinical relevance, little is known about their prevalence and demographic correlates, particularly among ethnically diverse older adults. We examined demographic and clinical correlates of regional microbleeds in a multi-ethnic cohort and examined categorization schemes of microbleed distribution and severity.

METHODS

Between 2005 and 2007, 769 individuals participated in a MRI study as part of the Washington Heights/Inwood Columbia Aging Project. Approximately four years later, 243 out of 339 participants (mean age=84.50) who returned for a repeat MRI had gradient-echo scans for microbleed assessment and comprised the sample. We examined the association of deep and lobar microbleeds with age, sex, education, vascular factors, cognitive status and markers of small vessel disease.

RESULTS

Sixty-seven of the 243 (27%) participants had at least one microbleed. Individuals with microbleeds were more likely to have a history of stroke than individuals without. When categorized as having either no microbleeds, microbleeds in deep regions only, in lobar regions only, and both deep and lobar microbleeds, hypertension, proportion of strokes, and white matter hyperintensity volume (WMH) increased monotonically across the four groups. The number of lobar microbleeds correlated with WMH volume and diastolic blood pressure.

CONCLUSIONS

Microbleeds in deep and lobar locations are associated with worse outcomes than microbleeds in either location alone, although the presence of lobar microbleeds appears to be more clinically relevant.

Clinical associations of cerebral microbleeds on magnetic resonance neuroimaging

Susceptibility-weighted and gradient-recalled echo T2* magnetic resonance imaging have enabled the detection of very small foci of blood within the brain, which have been termed "cerebral microbleeds." These petechial intraparenchymal hemorrhages have begun to emerge as diagnostically and prognostically useful markers in a variety of disease states. Severe hypertension and cerebral amyloid angiopathy are perhaps the best established microhemorrhagic conditions from neuroimaging literature; however, many others are also recognized including cerebral autosomal dominant arteriopathy, subcortical infarcts, and leukoencephalopathy (CADASIL), moyamoya disease, fat embolism, cerebral malaria, and infective endocarditis. Microbleeds are also a common finding in the setting of trauma and stroke. The purpose of this review is to broadly describe the neuroimaging of cerebral microbleeds in a wide variety of conditions, including the differences in their appearance and distribution in different disease states. In a few situations, the presence of microbleeds may influence clinical management, and we discuss these situations in detail. The major importance of this emerging field in neuroimaging is the potential to identify microvascular pathology at an asymptomatic or minimally symptomatic stage and create a window of therapeutic opportunity.

Cerebral microbleeds are associated with deep white matter hyperintensities, but only in hypertensive patients

Cerebral microbleeds (CMBs) and white matter hyperintensities (WMH) are the most common manifestations of small vessel disease, and often co-occur in patients with cerebral vascular disease. Hypertension is widely accepted as a risk factor for both CMBs and WMH. However, the effect of hypertension on the association between CMBs and WMH remains unclear. We hypothesized that the relationship between CMBs and WMH is determined by hypertension. One hundred forty-eight patients with acute cerebrovascular disease who were admitted to PLA general hospital in Beijing, China from February 2010 to May 2011 were recruited in this study. CMBs on T2*-weighted angiography (SWAN) were assessed using the Brain Observer Microbleed Rating Scale criteria. The severity of the WMH was separately assessed as either peri-ventricular hyperintensities (PVH) or deep white matter hyperintensities (DWMH). The association among CMBs and the severity of WMH, and hypertension were determined. CMBs were found in 65 (43.9%) patients. The frequency of CMBs was related to the severity of DWMH and PVH. CMBs were more frequently observed in patients with hypertension compared to patients without hypertension (51.3% vs. 20.0%, p = 0.001). Hypertension was an independent risk factor for CMBs (odds ratio 5.239, p = 0.001) and DWMH (odds ratio 2.373, p = 0.040). Furthermore, the relationship between the presence of CMBs and the severity of DWMH was only found in patients with hypertension (r = 0.298, p<0.01). However, CMBs were associated with PVH independently of hypertension. This study demonstrated that hypertension determined the association between CMBs and DWMH.

Cerebral microbleeds: their associated factors, radiologic findings, and clinical implications

Cerebral microbleeds (CMBs) are tiny, round dark-signal lesions that are most often detected on gradient-echo MR images. CMBs consist of extravasations of blood components through fragile microvascular walls characterized by lipohyalinosis and surrounding macrophages. The prevalence of CMBs in elderly subjects with no history of cerebrovascular disease is around 5%, but is much higher in patients with ischemic or hemorrhagic stroke. Development of CMBs is closely related to various vascular risk factors; in particular, lobar CMBs are thought to be associated with cerebral amyloid angiopathy. The presence of CMBs has been hypothesized to reflect cerebral-hemorrhage-prone status in patients with hypertension or amyloid microangiopathy. Stroke survivors with CMBs have been consistently found to have an elevated risk of subsequent hemorrhagic stroke or an antithrombotic-related hemorrhagic complication, although studies have failed to establish a link between CMBs and hemorrhagic transformation after thrombolytic treatment. A large prospective study is required to clarify the clinical significance of CMBs and their utility in a decision-making index.

Microbleeds in ischemic stroke are associated with lower serum adiponectin and higher soluble E-selectin levels

BACKGROUND

Cerebral microbleeds (CMBs) are the important indicators of cerebral small vessel disease. However, it is still unclear whether endothelial dysfunction is involved in CMBs. In this study, we performed a prospective study to investigate the correlation between sE-selectin (soluble E-selectin) or adiponectin and the prevalence of CMBs.

METHODS

We recruited 133 consecutive patients with first-ever ischemic stroke for this study. Finally, 126 patients were analyzed. The number and presence of CMBs were detected and evaluated on susceptibility-weighted magnetic resonance imaging within two weeks after symptom onset. We assessed the serum levels of adiponectin and sE-selectin for patients.

RESULTS

CMBs were detected in 63 subjects (50%) within 126 patients and more prevalent in mixed brain regions (55.6%). In binary logistic regression analysis, each 1SD-increase in adiponectin level was significantly conversely associated with the prevalence of CMBs after adjusting for age, sex and cardiovascular risk factors (OR = 0.55; 95% CI: 0.36-0.84); but sE-selectin was significantly positively associated with the prevalence of CMBs (OR = 1.09; 95% CI: 1.02-1.15). Furthermore, partial correlation analyses showed that sE-selectin remained significantly associated with and correlated conversely to adiponectin (r = -0.452, p = 0.001).

CONCLUSIONS

Endothelial injury may play a role in the pathogenesis of CMBs, and serum levels of adiponectin and sE-selectin were closely related to CMBs. Adiponectin might be protective for the prevalence of CMBs.

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.

In vivo iron quantification in collagenase-induced microbleeds in rat brain

Brain microbleeds (BMB) are associated with chronic and acute cerebrovascular disease. Because BMB present in the brain is a source of potentially cytotoxic iron proportional to the volume of extravasated blood, BMB iron content is a potentially valuable biomarker both to assess tissue risk and small cerebral vessel health. We recently reported methods to quantify focal iron sources using phase images that were tested in phantoms and BMB in postmortem tissue. In this study, we applied our methods to small hemorrhagic lesions induced in the in vivo rat brain using bacterial collagenase. As expected by theory, measurements of geometric features in phase images correlated with lesion iron content measured by graphite furnace atomic absorption spectrometry. Iron content estimation following BMB in an in vivo rodent model could shed light on the role and temporal evolution of iron-mediated tissue damage and efficacy of potential treatments in cerebrovascular diseases associated with BMB.

Iron quantification of microbleeds in postmortem brain

Brain microbleeds (BMB) are associated with chronic and acute cerebrovascular disease and present a source of pathologic iron to the brain proportional to extravasated blood. Therefore, BMB iron content is potentially a valuable biomarker. We tested noninvasive phase image methods to quantify iron content and estimate true source diameter (i.e., unobscured by the blooming effect) of BMB in postmortem human tissue. Tissue slices containing BMB were imaged using a susceptibility weighted imaging protocol at 11.7T. BMB lesions were assayed for iron content using atomic absorption spectrometry. Measurements of geometric features in phase images were related to lesion iron content and source diameter using a mathematical model. BMB diameter was estimated by image feature geometry alone without explicit relation to the magnetic susceptibility. A strong linear relationship (R(2) = 0.984, P < 0.001) predicted by theory was observed in the experimental data, presenting a tentative standardization curve where BMB iron content in similar tissues could be calculated. In addition, we report BMB iron mass measurements, as well as upper bound diameter and lower bound iron concentration estimates. Our methods potentially allows the calculation of brain iron load indices based on BMB iron content and classification of BMB by size unobscured by the blooming effect.

Risk of "silent stroke" in patients older than 60 years: risk assessment and clinical perspectives

With the increasing size of the elderly population and evolving imaging technology, silent brain infarction (SBI) has garnered attention from both the public and the physicians. Over 20% of the elderly exhibit SBI, and the prevalence of SBI increases steadily with age, ie, 30%–40% in those older than 70 years. Well-known cardiovascular risk factors such as hypertension has been identified as a risk factor of SBI (odds ratio [OR] = 3.47) Besides this, blood pressure (BP) reactivity to mental stress, morning BP surges, and orthostatic BP changes have been demonstrated to contribute to the presence of SBI. Further, a metabolic syndrome not only as a whole syndrome (OR =2.18) but also as individual components could have an influence on SBI. Increased C-reactive protein and interleukin-6, coronary artery disease, body mass index, and alcohol consumption have also been associated with SBI. The ORs and possible mechanisms have been discussed in this article. Overt stroke, dementia, depression, and aspiration pneumonia were all associated with SBI. (overt stroke: hazard ratio [HR] =1.9, 95% confidence interval [CI]: 1.2–2.8; dementia: HR =2.26, 95% CI: 1.09–4.70). We also looked into their close relationship with SBI in this review.

Correlation of hypointensities in susceptibility-weighted images to tissue histology in dementia patients with cerebral amyloid angiopathy: a postmortem MRI study

Neuroimaging with iron-sensitive MR sequences [gradient echo T2* and susceptibility-weighted imaging (SWI)] identifies small signal voids that are suspected brain microbleeds. Though the clinical significance of these lesions remains uncertain, their distribution and prevalence correlates with cerebral amyloid angiopathy (CAA), hypertension, smoking, and cognitive deficits. Investigation of the pathologies that produce signal voids is necessary to properly interpret these imaging findings. We conducted a systematic correlation of SWI-identified hypointensities to tissue pathology in postmortem brains with Alzheimer’s disease (AD) and varying degrees of CAA. Autopsied brains from eight AD patients, six of which showed advanced CAA, were imaged at 3T; foci corresponding to hypointensities were identified and studied histologically. A variety of lesions was detected; the most common lesions were acute microhemorrhage, hemosiderin residua of old hemorrhages, and small lacunes ringed by hemosiderin. In lesions where the bleeding vessel could be identified, β-amyloid immunohistochemistry confirmed the presence of β-amyloid in the vessel wall. Significant cellular apoptosis was noted in the perifocal region of recent bleeds along with heme oxygenase 1 activity and late complement activation. Acutely extravasated blood and hemosiderin were noted to migrate through enlarged Virchow–Robin spaces propagating an inflammatory reaction along the local microvasculature; a mechanism that may contribute to the formation of lacunar infarcts. Correlation of imaging findings to tissue pathology in our cases indicates that a variety of CAA-related pathologies produce MR-identified signal voids and further supports the use of SWI as a biomarker for this disease.