High frequency of apolipoprotein E epsilon 2 allele in hemorrhage due to cerebral amyloid angiopathy

Cerebral Amyloid Angiopathy in Patients with Cognitive Impairment: Cerebrospinal Fluid Biomarkers

INTRODUCTION

Cerebral amyloid angiopathy (CAA) is characterized by amyloid β (Aβ) deposition in brain vessels, leading to hemorrhagic phenomena and cognitive impairment. Magnetic resonance imaging (MRI)-based criteria allow a diagnosis of probable CAA in vivo, but such a diagnosis cannot predict the eventual development of CAA.

METHODS

We conducted a retrospective cohort study of 464 patients with cognitive disorders whose data were included in a brain health biobank. De-identified parameters including sex, age, cognitive score, APOE status, and cerebrospinal fluid (CSF) levels of Aβ 1-40, Aβ 1-42, phosphorylated tau, and total tau were assessed in those with and without CAA. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined.

RESULTS

CAA was present in 53 of 464 (11.5%) patients. P-tau level was significantly higher in those with CAA (115 vs. 84.3 pg/mL p = 0.038). In univariate analyses, the risk of developing CAA was higher with increased age (OR, 1.036; 95% CI: 1.008, 1.064; p = 0.011) and decreased CSF level of Aβ 1-40 (OR, 0.685; 95% CI: 0.534, 0.878; p = 0.003). In multivariate analyses, the risk of CAA remained higher with a decreased CSF level of Aβ 1-40 (OR, 0.681; 95% CI: 0.531, 0.874; p = 0.003).

CONCLUSION

These findings suggest that Aβ 1-40 levels in the CSF might be a useful molecular biomarker of CAA in patients with dementia.

Between a rock and a hard place: resumption of oral anticoagulant therapy after intracranial hemorrhage

Intracranial hemorrhage (ICH) is the most feared and lethal complication of oral anticoagulant (OAC) therapy. Resumption of OAC after ICH has long posed a challenge for clinicians, complicated by the expanding range of anticoagulant agents available in modern clinical practice, including direct OACs and, more recently, factor XI and XII inhibitors. A review of the current literature found support for resuming OAC in the majority of patients after ICH based on pooled retrospective data showing that resumption is associated with a lower risk of mortality and thromboembolism without a significantly increased risk of recurrent hemorrhage. The optimal time to resume OAC is less clear; however, the available evidence suggests that the composite risk of both recurrent hemorrhage and thromboembolism is likely minimized, somewhere between 4 and 6 weeks, after ICH in most patients. Specific considerations to guide the optimal resumption time in the individual patient include ICH location, mechanism, and anticoagulant class. Patients with mechanical heart valves and intracerebral malignancy represent high-risk groups who require more nuanced decision making. Here, we appraise the literature with the aim of providing a practical guide for clinicians while also discussing priorities for future investigation.

Prevalence, distribution, and severity of cerebral amyloid angiopathy differ between Lewy body diseases and Alzheimer's disease

Dementia with Lewy bodies (DLB), Parkinson's disease dementia (PDD), and Parkinson's disease (PD) collectively known as Lewy body diseases (LBDs) are neuropathologically characterised by α-synuclein deposits (Lewy bodies and Lewy neurites). However, LBDs also exhibit pathology associated with Alzheimer's disease (AD) (i.e. hyperphosphorylated tau and amyloid β (Aβ). Aβ can be deposited in the walls of blood vessels in the brains of individuals with AD, termed cerebral amyloid angiopathy (CAA). The aim of this study was to investigate the type and distribution of CAA in DLB, PDD, and PD and determine if this differs from AD. CAA type, severity, and topographical distribution was assessed in 94 AD, 30 DLB, 17 PDD, and 11 PD cases, and APOE genotype evaluated in a subset of cases where available. 96.3% AD cases, 70% DLB cases and 82.4% PDD cases exhibited CAA (type 1 or type 2). However only 45.5% PD cases had CAA. Type 1 CAA accounted for 37.2% of AD cases, 10% of DLB cases, and 5.9% of PDD cases, and was not observed in PD cases. There was a hierarchical topographical distribution in regions affected by CAA where AD and DLB displayed the same distribution pattern that differed from PDD and PD. APOE ε4 was associated with severity of CAA in AD cases. Topographical patterns and severity of CAA in DLB more closely resembled AD rather than PDD, and as type 1 CAA is associated with clinical dementia in AD, further investigations are warranted into whether the increased presence of type 1 CAA in DLB compared to PDD are related to the onset of cognitive symptoms and is a distinguishing factor between LBDs. Possible alignment of the the topographical distribution of CAA and microbleeds in DLB warrants further investigation. CAA in DLB more closely resembles AD rather than PDD or PD, and should be taken into consideration when stratifying patients for clinical trials or designing disease modifying therapies.

Exploring cerebral amyloid angiopathy: Insights into pathogenesis, diagnosis, and treatment

Cerebral Amyloid Angiopathy (CAA) is a neurological disorder characterized by the deposition of amyloid plaques in the walls of cerebral blood vessels. This condition poses significant challenges in terms of understanding its underlying mechanisms, accurate diagnosis, and effective treatment strategies. This article aims to shed light on the complexities of CAA by providing insights into its pathogenesis, diagnosis, and treatment options. The pathogenesis of CAA involves the accumulation of amyloid beta (Aβ) peptides in cerebral vessels, leading to vessel damage, impaired blood flow, and subsequent cognitive decline. Various genetic and environmental factors contribute to the development and progression of CAA, and understanding these factors is crucial for targeted interventions. Accurate diagnosis of CAA often requires advanced imaging techniques, such as magnetic resonance imaging (MRI) or positron emission tomography (PET) scans, to detect characteristic amyloid deposits in the brain. Early and accurate diagnosis enables appropriate management and intervention strategies. Treatment of CAA focuses on preventing further deposition of amyloid plaques, managing associated symptoms, and reducing the risk of complications such as cerebral hemorrhage. Currently, there are no disease-modifying therapies specifically approved for CAA. However, several experimental treatments targeting Aβ clearance and anti-inflammatory approaches are being investigated in clinical trials, offering hope for future therapeutic advancements.

Amyloid-related imaging abnormalities (ARIA): radiological, biological and clinical characteristics

Excess accumulation and aggregation of toxic soluble and insoluble amyloid-β species in the brain are a major hallmark of Alzheimer's disease. Randomized clinical trials show reduced brain amyloid-β deposits using monoclonal antibodies that target amyloid-β and have identified MRI signal abnormalities called amyloid-related imaging abnormalities (ARIA) as possible spontaneous or treatment-related adverse events. This review provides a comprehensive state-of-the-art conceptual review of radiological features, clinical detection and classification challenges, pathophysiology, underlying biological mechanism(s) and risk factors/predictors associated with ARIA. We summarize the existing literature and current lines of evidence with ARIA-oedema/effusion (ARIA-E) and ARIA-haemosiderosis/microhaemorrhages (ARIA-H) seen across anti-amyloid clinical trials and therapeutic development. Both forms of ARIA may occur, often early, during anti-amyloid-β monoclonal antibody treatment. Across randomized controlled trials, most ARIA cases were asymptomatic. Symptomatic ARIA-E cases often occurred at higher doses and resolved within 3-4 months or upon treatment cessation. Apolipoprotein E haplotype and treatment dosage are major risk factors for ARIA-E and ARIA-H. Presence of any microhaemorrhage on baseline MRI increases the risk of ARIA. ARIA shares many clinical, biological and pathophysiological features with Alzheimer's disease and cerebral amyloid angiopathy. There is a great need to conceptually link the evident synergistic interplay associated with such underlying conditions to allow clinicians and researchers to further understand, deliberate and investigate on the combined effects of these multiple pathophysiological processes. Moreover, this review article aims to better assist clinicians in detection (either observed via symptoms or visually on MRI), management based on appropriate use recommendations, and general preparedness and awareness when ARIA are observed as well as researchers in the fundamental understanding of the various antibodies in development and their associated risks of ARIA. To facilitate ARIA detection in clinical trials and clinical practice, we recommend the implementation of standardized MRI protocols and rigorous reporting standards. With the availability of approved amyloid-β therapies in the clinic, standardized and rigorous clinical and radiological monitoring and management protocols are required to effectively detect, monitor, and manage ARIA in real-world clinical settings.

Inflammatory Cerebral Amyloid Angiopathy: A Broad Clinical Spectrum

Cerebral amyloid angiopathy (CAA) is a common central nervous system (CNS) vasculopathy, which in some cases is associated with subacute encephalopathy, seizures, headaches, or strokes due to vascular inflammation directed against vascular amyloid accumulation. The pathological subtypes of inflammatory CAA include CAA-related inflammation (CAAri) with mostly perivascular lymphocytic infiltrates, or amyloid-beta (Aβ)-related angiitis (ABRA) with transmural granulomatous inflammation. CAAri and ABRA probably represent part of the spectrum of CNS vasculopathies, intermediate between CAA and primary CNS vasculitis, and they are closely related to Aβ-related imaging abnormalities and other manifestations of an inflammatory response directed against Aβ in the leptomeninges and cerebral parenchyma. As treatment strategies in Alzheimer's disease shift toward potentially effective antiamyloid immunotherapy, the incidence rate of inflammatory CAA (which is probably an underrecognized condition) is likely to increase. Its clinical features are varied and include subacute encephalopathy, behavioral symptoms, headaches, seizures, and focal neurological deficits, which necessitate a high degree of suspicion for this disorder that often responds to treatment. The recent definition of the typical clinical and radiological syndrome has increased its recognition and may eliminate the need for invasive histological sampling in at least some affected patients. Here we review the pathophysiology, clinical spectrum, and approach to diagnosis, and discuss illustrative cases that highlight the wide range of clinical presentations.

Fatal thrombolysis-related intracerebral haemorrhage associated with amyloid-β-related angiitis in a middle-aged patient - case report and literature review

BACKGROUND

Amyloid-β-related angiitis (ABRA) is a rare complication of cerebral amyloid angiopathy, characterized by amyloid-β deposition in the leptomeningeal and cortical vessels with associated angiodestructive granulomatous inflammation. The clinical presentation is variable, including subacute cognitive decline, behavioural changes, headaches, seizures and focal neurological deficits, which may mimic other conditions. Here, we present a case with fatal thrombolysis-related haemorrhage associated with ABRA in a middle-aged patient.

CASE PRESENTATION

A 55-year-old man was admitted to hospital with sudden onset left-sided cheek, arm and hand sensory loss, blurred vision, and worsening headache, with a National Institutes of Health Stroke Scale (NIHSS) score of 3. An acute CT head scan showed no contraindications, and therefore the decision was made to give intravenous thrombolysis. Post-thrombolysis, he showed rapid deterioration with visual disturbances, headache and confusion, and a repeat CT head scan confirmed several areas of intracerebral haemorrhage. No benefit from surgical intervention was expected, and the patient died four days after the first presentation. Neuropathological examination found acute ischemic infarcts of three to five days duration in the basal ganglia, insular cortex and occipital lobe, correlating with the initial clinical symptoms. There were also extensive recent intracerebral haemorrhages most likely secondary to thrombolysis. Furthermore, the histological examination revealed severe cerebral amyloid angiopathy associated with granulomatous inflammatory reaction, consistent with ABRA.

CONCLUSIONS

Presentation of ABRA in a middle-aged patient highlighted the difficulties in recognition and management of this rare condition. There is emerging evidence that patients with CAA may have increased risk of fatal intracerebral haemorrhages following thrombolysis. This may be further increased by a coexisting CAA-related inflammatory vasculopathy which is potentially treatable with steroid therapy if early diagnosis is made.

Clinical and neuroimaging risk factors associated with the development of intracerebral hemorrhage while taking direct oral anticoagulants

BACKGROUND AND AIMS

Intracerebral hemorrhage (ICH) associated with direct oral anticoagulant (DOAC) usage confers significant mortality/disability. We aimed to understand the clinical and neuroimaging features associated with developing ICH among DOAC users.

METHODS

Clinical and radiological data were collected from consecutive DOAC users with ICH (DOAC-ICH) and age-matched controls without ICH from a single referral center. The frequency/distribution of MRI markers of hemorrhage risk were assessed. Baseline demographics and neuroimaging markers were compared in univariate tests. Significant associations (p < 0.1) were entered into a multivariable regression model to determine predictors of ICH.

RESULTS

86 DOAC-ICH and 94 ICH-free patients were included. Diabetes, coronary artery disease, prior ischemic stroke, smoking history, and antiplatelet usage were more common in ICH patients than ICH-free DOAC users. In the neuroimaging analyses, severe white matter hyperintensities (WMHs), lacunes, cortical superficial siderosis (cSS), and cerebral microbleeds (CMBs) were more common in the ICH cohort than the ICH-free cohort. In the multivariable regression, diabetes [OR 3.53 95% CI (1.05-11.87)], prior ischemic stroke [OR 14.80 95% CI (3.33-65.77)], smoking history [OR 3.08 95% CI (1.05-9.01)], CMBs [OR 4.07 95% CI (1.45-11.39)], and cSS [OR 39.73 95% CI (3.43-460.24)] were independently associated with ICH.

CONCLUSIONS

Risk factors including diabetes, prior stroke, and smoking history as well as MRI biomarkers including CMBs and cSS are associated with ICH in DOAC users. Although screening MRIs are not typically performed prior to initiating DOAC therapy, these data suggest that patients of high-hemorrhagic risk may be identified.

Intracerebral Hemorrhage: The Effects of Aging on Brain Injury

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke with high rates of mortality and morbidity. ICH patients often suffer devastating and debilitating neurological impairments, from which the majority of victims are unable to fully recover to functional independence. Unfortunately, there is no established medical therapy for ICH, which is partly attributed to the lack of understanding of the complex pathology of the disorder. Despite advanced age being a major risk factor of ICH, most preclinical studies on ICH employed young animal subjects. Due to this discrepancy, the molecular level changes in the aging brain after ICH are largely unknown, limiting the translation of preclinical studies into potential human treatments. The purpose of this review is to highlight the effects of advanced age on ICH- induced brain injury and recovery and to draw attention to current knowledge gaps, which warrant further investigation.

Cerebral Hemorrhage: Pathophysiology, Treatment, and Future Directions

Intracerebral hemorrhage (ICH) is a devastating form of stroke with high morbidity and mortality. This review article focuses on the epidemiology, cause, mechanisms of injury, current treatment strategies, and future research directions of ICH. Incidence of hemorrhagic stroke has increased worldwide over the past 40 years, with shifts in the cause over time as hypertension management has improved and anticoagulant use has increased. Preclinical and clinical trials have elucidated the underlying ICH cause and mechanisms of injury from ICH including the complex interaction between edema, inflammation, iron-induced injury, and oxidative stress. Several trials have investigated optimal medical and surgical management of ICH without clear improvement in survival and functional outcomes. Ongoing research into novel approaches for ICH management provide hope for reducing the devastating effect of this disease in the future. Areas of promise in ICH therapy include prognostic biomarkers and primary prevention based on disease pathobiology, ultra-early hemostatic therapy, minimally invasive surgery, and perihematomal protection against inflammatory brain injury.

The informed road map to prevention of Alzheimer Disease: A call to arms

Alzheimer disease (AD) prevention trials hold the promise to delay or prevent cognitive decline and dementia onset by intervening before significant neuronal damage occurs. In recent years, the first AD prevention trials have launched and are yielding important findings on the biology of targeting asymptomatic AD pathology. However, there are limitations that impact the design of these prevention trials, including the translation of animal models that recapitulate key stages and multiple pathological aspects of the human disease, missing target validation in asymptomatic disease, uncertain causality of the association of pathophysiologic changes with cognitive and clinical symptoms, and limited biomarker validation for novel targets. The field is accelerating advancements in key areas including the development of highly specific and quantitative biomarker measures for AD pathology, increasing our understanding of the course and relationship of amyloid and tau pathology in asymptomatic through symptomatic stages, and the development of powerful interventions that can slow or reverse AD amyloid pathology. We review the current status of prevention trials and propose key areas of needed research as a call to basic and translational scientists to accelerate AD prevention. Specifically, we review (1) sporadic and dominantly inherited primary and secondary AD prevention trials, (2) proposed targets, mechanisms, and drugs including the amyloid, tau, and inflammatory pathways and combination treatments, (3) the need for more appropriate prevention animal models and experiments, and (4) biomarkers and outcome measures needed to design human asymptomatic prevention trials. We conclude with actions needed to effectively move prevention targets and trials forward.

APOE genotype dependent molecular abnormalities in the cerebrovasculature of Alzheimer's disease and age-matched non-demented brains

Cerebrovascular dysfunction is a hallmark feature of Alzheimer's disease (AD). One of the greatest risk factors for AD is the apolipoprotein E4 (E4) allele. The APOE4 genotype has been shown to negatively impact vascular amyloid clearance, however, its direct influence on the molecular integrity of the cerebrovasculature compared to other APOE variants (APOE2 and APOE3) has been largely unexplored. To address this, we employed a 10-plex tandem isobaric mass tag approach in combination with an ultra-high pressure liquid chromatography MS/MS (Q-Exactive) method, to interrogate unbiased proteomic changes in cerebrovessels from AD and healthy control brains with different APOE genotypes. We first interrogated changes between healthy control cases to identify underlying genotype specific effects in cerebrovessels. EIF2 signaling, regulation of eIF4 and 70S6K signaling and mTOR signaling were the top significantly altered pathways in E4/E4 compared to E3/E3 cases. Oxidative phosphorylation, EIF2 signaling and mitochondrial dysfunction were the top significant pathways in E2E2 vs E3/E3cases. We also identified AD-dependent changes and their interactions with APOE genotype and found the highest number of significant proteins from this interaction was observed in the E3/E4 (192) and E4/E4 (189) cases. As above, EIF2, mTOR signaling and eIF4 and 70S6K signaling were the top three significantly altered pathways in E4 allele carriers (i.e. E3/E4 and E4/E4 genotypes). Of all the cerebrovascular cell-type specific markers identified in our proteomic analyses, endothelial cell, astrocyte, and smooth muscle cell specific protein markers were significantly altered in E3/E4 cases, while endothelial cells and astrocyte specific protein markers were altered in E4/E4 cases. These proteomic changes provide novel insights into the longstanding link between APOE4 and cerebrovascular dysfunction, implicating a role for impaired autophagy, ER stress, and mitochondrial bioenergetics. These APOE4 dependent changes we identified could provide novel cerebrovascular targets for developing disease modifying strategies to mitigate the effects of APOE4 genotype on AD pathogenesis.

Recurrent Lobar Hemorrhages and Multiple Cortical Superficial Siderosis in a Patient of Alzheimer's Disease With Homozygous APOE ε2 Allele Presenting Hypobetalipoproteinemia and Pathological Findings of 18F-THK5351 Positron Emission Tomography: A Case Report

In Alzheimer's disease, the apolipoprotein E gene (APOE) ε2 allele is a protective genetic factor, whereas the APOE ε4 allele is a genetic risk factor. However, both the APOE ε2 and the APOE ε4 alleles are genetic risk factors for lobar intracerebral hemorrhage. The reasons for the high prevalence of lobar intracerebral hemorrhage and the low prevalence of Alzheimer's disease with the APOE ε2 allele remains unknown. Here, we describe the case of a 79-year-old Japanese female with Alzheimer's disease, homozygous for the APOE ε2 allele. This patient presented with recurrent lobar hemorrhages and multiple cortical superficial siderosis. The findings on the ¹¹C-labeled Pittsburgh Compound B-positron emission tomography (PET) were characteristic of Alzheimer's disease. ¹⁸F-THK5351 PET revealed that the accumulation of ¹⁸F-THK 5351 in the right pyramidal tract at the pontine level, the cerebral peduncle of the midbrain, and the internal capsule, reflecting the lesions of the previous lobar intracerebral hemorrhage in the right frontal lobe. Moreover, ¹⁸F-THK5351 accumulated in the bilateral globus pallidum, amygdala, caudate nuclei, and the substantia nigra of the midbrain, which were probably off-target reaction, by binding to monoamine oxidase B (MAO-B). ¹⁸F-THK5351 were also detected in the periphery of prior lobar hemorrhages and a cortical subarachnoid hemorrhage, as well as in some, but not all, areas affected by cortical siderosis. Besides, ¹⁸F-THK5351 retentions were observed in the bilateral medial temporal cortices and several cortical areas without cerebral amyloid angiopathy or prior hemorrhages, possibly where tau might accumulate. This is the first report of a patient with Alzheimer's disease, carrying homozygous APOE ε2 allele and presenting with recurrent lobar hemorrhages, multiple cortical superficial siderosis, and immunohistochemically vascular amyloid β. The ¹⁸F-THK5351 PET findings suggested MAO-B concentrated regions, astroglial activation, Waller degeneration of the pyramidal tract, neuroinflammation due to CAA related hemorrhages, and possible tau accumulation.

Management of Intracerebral Hemorrhage: JACC Focus Seminar

Intracerebral hemorrhage (ICH) accounts for a disproportionate amount of stroke-related morbidity and mortality. Although chronic hypertension and cerebral amyloid angiopathy are the underlying cerebral vasculopathies accounting for the majority of ICH, there are a broad range of potential causes, and effective management requires accurate identification and treatment of the underlying mechanism of hemorrhage. Magnetic resonance imaging and vascular imaging techniques play a critical role in identifying disease mechanisms. Modern treatment of ICH focuses on rapid stabilization, often requiring urgent treatment of mass effect, aggressive blood pressure reduction and correction of contributing coagulopathies to achieve hemostasis. We discuss management of patients with ICH who continue to require long-term anticoagulation, the interaction of ICH with neurodegenerative diseases, and our approach to prognostication after ICH. We close this review with a discussion of novel medical and surgical approaches to ICH treatment that are being tested in clinical trials.

APOE Genotypes and Brain Imaging Classes in Normal Cognition, Mild Cognitive Impairment, and Alzheimer's Disease: A Longitudinal Study

OBJECTIVE

To evaluate in 419 stroke-free cognitively normal subjects (CN) aged 45-82 years covering during a long prospective study (11.54 ± 1.47 years) the preclinical to dementia spectrum: 1) the distribution of small vessel disease (V) and brain atrophy (A) aggregated as following: V-/A-, V-/A+, V+/A-, V+/A+; 2) the relationship of these imaging classes with individual apolipoprotein E (APOE) genotypes; 3) the risk of progression to Alzheimer Disease (AD) of the individual APOE genotypes.

METHODS

Participants underwent one baseline (t0), and 4 clinical and neuropsychological assessments (t1,t2,t3, and t4). Brain MRI was performed in all subjects at t0, t2, t3 and t4.. White matter hyperintensities were assessed through two visual rating scales. Lacunes were also rated. Subcortical and global brain atrophy were determined through the bicaudate ratio and the lateral ventricle to brain ratio, respectively. APOE genotypes were determined at t0 in all subjects. Cox proportional hazard model was used to evaluate the risk of progression to AD.

RESULTS

The imaging class of mixed type was very common in AD, and in non amnestic mild cognitive impaired APOE ε4 non carriers. In these subjects, frontal and parieto-occipital regions were most affected by small vessel disease.

CONCLUSION

Our findings suggest that the APOE ε3 allele is probably linked to the brain vascular pathology.

Insights in the pathophysiology of haemorrhagic strokes in a sub-Sahara African country, an epidemiological and MRI study

OBJECTIVE

Intra-cerebral Haemorrhage (ICH) seems more prevalent in sub-Saharan Africa (SSA) than in High-Income Countries (HIC) with poorer clinical outcome. Higher impact of hypertension and/or amyloid angiopathy could account for this disproportion. Here, we sought to (i) retrospectively compare ICH clinical and imaging patterns in Belgium and Guinea and in a subsequent cohort (ii) prospectively compare brain MRI characteristics to seek evidence for a different proportion of amyloid angiopathy patterns.

METHODS

Ninety one consecutive patients admitted for spontaneous ICH at Brussels Erasme-ULB Hospital and at Conakry Ignace Deen-UGANC were retrospectively compared in terms of ICH volume estimated with the ABC/2 method, clinical characteristics and modified ranking (mRS) score at 30 days. mRS was dichotomised as good outcomes (≤3) and poor outcomes (>3). A prospective cohort of 30 consecutive patients with ICH admitted at CHU Conakry Ignace Deen-UGANC was prospectively included to undergo brain MRI. Results of the Guinean MRI were compared to 30 patients randomly selected from Brussels' initial cohort. Paired Student's t-test and Mann-Whitney u-test were used for group comparisons.

RESULTS

Age of ICH onset was higher in Belgium (68 ± 17 years vs. 56 ± 14 years, P < 0.01) while ICH volume and 30-day mortality rate were higher in Guinea (20 ml vs. 11 ml, P < 0.01 and mortality 33% vs. 10 %, P < 0.01). ICH burden in survivors in Conakry and Brussels showed respectively good outcomes in 56.7% and 60.4% (P = 0.09) and poor outcomes in 10.3% vs. 29.6% (P < 0.001). MRI analysis of the prospective cohort failed to disclose significant differences regarding brain MRI characteristics.

CONCLUSIONS

Intra-cerebral Haemorrhage affected patients 15 years younger in Guinea with larger haematoma volumes and higher mortality than in Belgium. MRI findings did not show more prevalent amyloid angiopathy pathology suggesting that better primary prevention of hypertension could positively impact ICH epidemiology in Guinea.

APOE2: protective mechanism and therapeutic implications for Alzheimer's disease

Investigations of apolipoprotein E (APOE) gene, the major genetic risk modifier for Alzheimer's disease (AD), have yielded significant insights into the pathogenic mechanism. Among the three common coding variants, APOE*ε4 increases, whereas APOE*ε2 decreases the risk of late-onset AD compared with APOE*ε3. Despite increased understanding of the detrimental effect of APOE*ε4, it remains unclear how APOE*ε2 confers protection against AD. Accumulating evidence suggests that APOE*ε2 protects against AD through both amyloid-β (Aβ)-dependent and independent mechanisms. In addition, APOE*ε2 has been identified as a longevity gene, suggesting a systemic effect of APOE*ε2 on the aging process. However, APOE*ε2 is not entirely benign; APOE*ε2 carriers exhibit increased risk of certain cerebrovascular diseases and neurological disorders. Here, we review evidence from both human and animal studies demonstrating the protective effect of APOE*ε2 against AD and propose a working model depicting potential underlying mechanisms. Finally, we discuss potential therapeutic strategies designed to leverage the protective effect of APOE2 to treat AD.

Genetic architecture of common non-Alzheimer's disease dementias

Frontotemporal dementia (FTD), dementia with Lewy bodies (DLB) and vascular dementia (VaD) are the most common forms of dementia after Alzheimer's disease (AD). The heterogeneity of these disorders and/or the clinical overlap with other diseases hinder the study of their genetic components. Even though Mendelian dementias are rare, the study of these forms of disease can have a significant impact in the lives of patients and families and have successfully brought to the fore many of the genes currently known to be involved in FTD and VaD, starting to give us a glimpse of the molecular mechanisms underlying these phenotypes. More recently, genome-wide association studies have also pointed to disease risk-associated loci. This has been particularly important for DLB where familial forms of disease are very rarely described. In this review we systematically describe the Mendelian and risk genes involved in these non-AD dementias in an effort to contribute to a better understanding of their genetic architecture, find differences and commonalities between different dementia phenotypes, and uncover areas that would benefit from more intense research endeavors.

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

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

Cerebral amyloid angiopathy and Alzheimer disease - one peptide, two pathways

The shared role of amyloid-β (Aβ) deposition in cerebral amyloid angiopathy (CAA) and Alzheimer disease (AD) is arguably the clearest instance of crosstalk between neurodegenerative and cerebrovascular processes. The pathogenic pathways of CAA and AD intersect at the levels of Aβ generation, its circulation within the interstitial fluid and perivascular drainage pathways and its brain clearance, but diverge in their mechanisms of brain injury and disease presentation. Here, we review the evidence for and the pathogenic implications of interactions between CAA and AD. Both pathologies seem to be driven by impaired Aβ clearance, creating conditions for a self-reinforcing cycle of increased vascular Aβ, reduced perivascular clearance and further CAA and AD progression. Despite the close relationship between vascular and plaque Aβ deposition, several factors favour one or the other, such as the carboxy-terminal site of the peptide and specific co-deposited proteins. Amyloid-related imaging abnormalities that have been seen in trials of anti-Aβ immunotherapy are another probable intersection between CAA and AD, representing overload of perivascular clearance pathways and the effects of removing Aβ from CAA-positive vessels. The intersections between CAA and AD point to a crucial role for improving vascular function in the treatment of both diseases and indicate the next steps necessary for identifying therapies.

Coexistence of Cerebral Microbleeds and Amyloid Pathology in Patients with Cognitive Complaints

Background and Purpose

We investigated the prevalence of amyloid positivity and cerebral microbleeds (CMBs) in subjects with cognitive complaints with the aim of identifying differences in clinical parameters and cognitive function according to the pattern of coexistence.

Methods

We retrospectively enrolled 200 subjects with memory impairment and applied both standardized ¹⁸F-florbetaben PET and brain MRI, including susceptibility-weighted imaging. The amyloid burden was visually classified as positive or negative, and the number and location of CMBs were also analyzed visually. Descriptive analysis was performed for the prevalence of amyloid positivity and CMBs. The relationship between the coexisting pattern of those two findings and clinical parameters including the results of neuropsychiatric tests was analyzed.

Results

Positive amyloid PET scans were exhibited by 102 (51.5%) of the 200 patients, and 51 (25.5%) of them had CMBs, which were mostly located in lobar areas in the patients with positive amyloid scans. The patients with CMBs were older and had a higher burden of white-matter hyperintensities than the patients without CMBs. The patients with CMBs also performed worse in confrontation naming and frontal/executive function. When classified by topographical region, parietal CMBs (odds ratio=3.739, p=0.024) were significantly associated with amyloid positivity.

Conclusions

The prevalence of CMBs was higher in patients with cognitive decline than in the general population. CMBs play distinctive roles in affecting clinical parameters and neuropsychological profiles according to the coexistence of amyloid pathology.

Absolute 10-year risk of dementia by age, sex and APOE genotype: a population-based cohort study

BACKGROUND

Dementia is a major cause of disability, and risk-factor reduction may have the potential to delay or prevent the disease. Our aim was to determine the absolute 10-year risk of dementia, by age, sex and apolipoprotein E (APOE) genotype.

METHODS

We obtained data from the Copenhagen General Population Study (from 2003 to 2014) and the Copenhagen City Heart Study (from 1991 to 1994 and 2001 to 2003). Participants underwent a questionnaire, physical examination and blood sampling at baseline. Diagnoses of dementia and cerebrovascular disease were obtained from the Danish National Patient Registry up to Nov. 10, 2014.

RESULTS

Among 104 537 individuals, the absolute 10-year risk of Alzheimer disease in 3017 women and men who were carriers of the APOE ɛ44 genotype was, respectively, 7% and 6% at age 60-69 years, 16% and 12% at age 70-79 years, and 24% and 19% at age 80 years and older. Corresponding values for all dementia were 10% and 8%, 22% and 19%, and 38% and 33%, respectively. Adjusted hazard ratios (HRs) for all dementia increased by genotype, from genotype ɛ22 to ɛ32 to ɛ33 to ɛ42 to ɛ43 to ɛ44 (p for trend < 0.001). Compared with ɛ33 carriers, ɛ44 carriers were more likely to develop Alzheimer disease (adjusted HR 8.74, 95% confidence interval [CI] 7.08-10.79), vascular dementia (adjusted HR 2.87, 95% CI 1.54-5.33), unspecified dementia (adjusted HR 4.68, 95% CI 3.74-5.85) and all dementia (adjusted HR 5.77, 95% CI 4.89-6.81).

INTERPRETATION

Age, sex and APOE genotype robustly identify high-risk groups for Alzheimer disease and all dementia. These groups can potentially be targeted for preventive interventions.

Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies

Polymorphism in the apolipoprotein E (APOE) gene is a major genetic risk determinant of late-onset Alzheimer disease (AD), with the APOE*ε4 allele conferring an increased risk and the APOE*ε2 allele conferring a decreased risk relative to the common APOE*ε3 allele. Strong evidence from clinical and basic research suggests that a major pathway by which APOE4 increases the risk of AD is by driving earlier and more abundant amyloid pathology in the brains of APOE*ε4 carriers. The number of amyloid-β (Aβ)-dependent and Aβ-independent pathways that are known to be differentially modulated by APOE isoforms is increasing. For example, evidence is accumulating that APOE influences tau pathology, tau-mediated neurodegeneration and microglial responses to AD-related pathologies. In addition, APOE4 is either pathogenic or shows reduced efficiency in multiple brain homeostatic pathways, including lipid transport, synaptic integrity and plasticity, glucose metabolism and cerebrovascular function. Here, we review the recent progress in clinical and basic research into the role of APOE in AD pathogenesis. We also discuss how APOE can be targeted for AD therapy using a precision medicine approach.

Intracerebral hemorrhage: an update on diagnosis and treatment

Introduction: Spontaneous non-traumatic intracerebral hemorrhage (ICH) is most often caused by small vessel diseases: deep perforator arteriopathy (hypertensive arteriopathy) or cerebral amyloid angiopathy (CAA). Although ICH accounts for only 10-15% of all strokes it causes a high proportion of stroke mortality and morbidity, with few proven effective acute or preventive treatments. Areas covered: We conducted a literature search on etiology, diagnosis, treatment, management and current clinical trials in ICH. In this review, We describe the causes, diagnosis (including new brain imaging biomarkers), classification, pathophysiological understanding, treatment (medical and surgical), and secondary prevention of ICH. Expert opinion: In recent years, significant advances have been made in deciphering causes, understanding pathophysiology, and improving acute treatment and prevention of ICH. However, the clinical outcome remains poor and many challenges remain. Acute interventions delivered rapidly (including medical therapies - targeting hematoma expansion, hemoglobin toxicity, inflammation, edema, anticoagulant reversal - and minimally invasive surgery) are likely to improve acute outcomes. Improved classification of the underlying arteriopathies (from neuroimaging and genetic studies) and prognosis should allow tailored prevention strategies (including sustained blood pressure control and optimized antithrombotic therapy) to further improve longer-term outcome in this devastating disease.

Brain ApoA-I, ApoJ and ApoE Immunodetection in Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a common cause of lobar intracerebral hemorrhage (ICH) in elderly individuals and it is the result of the cerebrovascular deposition of beta-amyloid (Aβ) protein. CAA is frequently found in patients with Alzheimer's disease (AD), although it has an independent contribution to the cognitive deterioration associated with age. Specific apolipoproteins (Apo) have been associated with Aβ fibrillization and clearance from the brain. In this regard, in the present study, we analyzed the brain levels of ApoE, ApoA-I, and ApoJ/clusterin in autopsy brains from 20 post-mortem cases with CAA type I, CAA type II, with parenchymal Aβ deposits or without Aβ deposits. Our objective was to find a possible differential pattern of apolipoproteins distribution in the brain depending on the CAA pathological presentation. The protein expression levels were adjusted by the APOE genotype of the patients included in the study. We found that ApoE and ApoJ were abundantly present in meningeal, cortical, and capillary vessels of the brains with vascular Aβ accumulation. ApoE and ApoJ also deposited extracellularly in the parenchyma, especially in cases presenting Aβ diffuse and neuritic parenchymal deposits. In contrast, ApoA-I staining was only relevant in capillary walls in CAA type I cases. On the other hand, ICH was the principal cause of death among CAA patients in our cohort. We found that CAA patients with ICH more commonly had APOEε2 compared with CAA patients without ICH. In addition, patients who suffered an ICH presented higher vascular ApoE levels in brain. However, higher ApoE presence in cortical arteries was the only independent predictor of suffering an ICH in our cohort after adjusting by age and APOE genotype. In conclusion, while ApoE and ApoJ appear to be involved in both vascular and parenchymal Aβ pathology, ApoA-I seems to be mainly associated with CAA, especially in CAA type I pathology. We consider that our study helps to molecularly characterize the distribution subtypes of Aβ deposition within the brain.

Clinical and neuropathologic analysis of intracerebral hemorrhage in patients with cerebral amyloid angiopathy

OBJECTIVE

To evaluate the clinical and histopathological features of elderly patients with subcortical intracerebral hemorrhage (ICH), and to analyze the presence of cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD) type pathologic changes using amyloid beta (Aβ) and tau immunohistochemistry.

PATIENTS AND METHODS

We retrospectively analyzed cases satisfying the Boston criteria for CAA among patients with subcortical hemorrhage who underwent surgical removal by craniotomy at our hospital. Surgical specimens were subjected to hematoxylin and eosin (HE) staining as well as immunostaining.

RESULTS

A total of 54 patients were included in this study, with a mean age of 74.5 years (range: 72.5-76.5 years, 95% confidence interval [CI]; 51% female). Of these 54 patients, 31 (57%) were hypertensive, 18 (33%) were undergoing antithrombotic therapy, and 12 (22%) had dementia. Strong immunoreactivity for Aβ40 in the cerebral vessels was observed in 30 patients (55.6%), and among these, 27 patients (90%) also showed strong immunoreactivity for Aβ42. Among the 54 patients, 25 (46%) exhibited AD characteristics, including Aβ-positive senile plaques and AT8-positive neurons. Multivariate analysis revealed that strong Aβ40 immunoreactivity in the cerebral vessels was associated with older patients, females, lack of high blood pressure, and the presence of AT8-positive neurons.

CONCLUSION

CAA patients with strong Aβ40 deposition in the cerebral vessels were associated with subcortical hemorrhage in our cohort. Future studies should investigate the pathomechanism of ICH in individuals with CAA.

β-amyloid wall deposit of temporal artery in subjects with spontaneous intracerebral haemorrhage

Background

Cerebral Amyloid Angiopathy has been indicated as an important cause of spontaneous non-hypertensive intracerebral haemorrhage (ICH).

Aims

to analyze the presence of β-amyloid deposit in the temporal artery of consecutive patients with ICH in comparison to control subjects and its relation to APO-E haplotype frequency.

Methods

We enrolled consecutive patients admitted to Neurosurgery Ward of University Hospital “P. Giaccone” of Palermo with a diagnosis of spontaneous non hypertensive ICH and as control 12 subjects without brain haemorrhage. Biopsy of superficial temporal artery has been performed and β-amyloid deposit was quantified.

Results

Among 25 subjects with ICH, 10 (40%) had APOE epsilon 2 allele and among these subjects 7 (70%) showed amyloid accumulation on temporal artery specimens, 8 (32%) subjects had APOE epsilon 3 allele and among these subjects only 2 (25%) showed amyloid accumulation on temporal artery specimens, whereas 7 (28%) had APOE epsilon 4 allele and of these, 7 (100%) showed amyloid accumulation on temporal artery specimens. At multivariable logistic regression analysis for the presence of amyloid, predictive factors for the presence of amyloid in temporal artery biopsies were: age, hypertension, intralobar site of haemorrhage, APOE epsilon 2 and APOE epsilon 4 alleles.

Discussion

Our findings of a higher frequency of amyloid deposition in temporal artery specimens in subjects with spontaneous intracerebral haemorrhage indicate a possible role of temporal artery as a possible diagnostic site of biopsy in subjects at high risk to develop intracranial haemorrhage related to Cerebral Amyloid Angiopathy.

Acute convexity subarachnoid haemorrhage and cortical superficial siderosis in probable cerebral amyloid angiopathy without lobar haemorrhage

INTRODUCTION

Acute non-traumatic convexity subarachnoid haemorrhage (cSAH) is increasingly recognised in cerebral amyloid angiopathy (CAA). We investigated: (a) the overlap between acute cSAH and cortical superficial siderosis-a new CAA haemorrhagic imaging signature and (b) whether acute cSAH presents with particular clinical symptoms in patients with probable CAA without lobar intracerebral haemorrhage.

METHODS

MRI scans of 130 consecutive patients meeting modified Boston criteria for probable CAA were analysed for cortical superficial siderosis (focal, ≤3 sulci; disseminated, ≥4 sulci), and key small vessel disease markers. We compared clinical, imaging and cortical superficial siderosis topographical mapping data between subjects with versus without acute cSAH, using multivariable logistic regression.

RESULTS

We included 33 patients with probable CAA presenting with acute cSAH and 97 without cSAH at presentation. Patients with acute cSAH were more commonly presenting with transient focal neurological episodes (76% vs 34%; p<0.0001) compared with patients with CAA without cSAH. Patients with acute cSAH were also more often clinically presenting with transient focal neurological episodes compared with cortical superficial siderosis-positive, but cSAH-negative subjects with CAA (76% vs 30%; p<0.0001). Cortical superficial siderosis prevalence (but no other CAA severity markers) was higher among patients with cSAH versus those without, especially disseminated cortical superficial siderosis (49% vs 19%; p<0.0001). In multivariable logistic regression, cortical superficial siderosis burden (OR 5.53; 95% CI 2.82 to 10.8, p<0.0001) and transient focal neurological episodes (OR 11.7; 95% CI 2.70 to 50.6, p=0.001) were independently associated with acute cSAH.

CONCLUSIONS

This probable CAA cohort provides additional evidence for distinct disease phenotypes, determined by the presence of cSAH and cortical superficial siderosis.

Pathological examination of cerebral amyloid angiopathy in patients who underwent removal of lobar hemorrhages

Cerebral amyloid angiopathy (CAA) is a degenerative disorder characterized by amyloid-β (Aβ) deposition in the brain microvessels. CAA is also known to contribute not only to cortical microbleeds but also lobar hemorrhages. This retrospective study examined CAA pathologically in patients who underwent direct surgeries for lobar hemorrhage. Thirty-three patients with lobar hemorrhage underwent open surgery with biopsy from 2007 to 2016 in our hospital. Cortical tissues over hematomas obtained surgically were pathologically examined using hematoxylin, eosin stain, and anti-Aβ antibody to diagnose CAA. We also investigated the advanced degree of CAA and clinical features of each patient with lobar hemorrhage. In the 33 patients, 4 yielded specimens that were insufficient to evaluate CAA pathologically. Twenty-four of the remaining 29 patients (82.8%) were pathologically diagnosed with CAA. The majority of CAA-positive patients had moderate or severe CAA based on a grading scale to estimate the advanced degree of CAA. About half of the CAA-positive patients had hypertension, and four took anticoagulant or antiplatelet agents. In five patients who were not pathologically diagnosed with CAA, one had severe liver function disorder, three had uncontrollable hypertension, and one had no obvious risk factor. Our pathological findings suggest that severe CAA with vasculopathic change markedly contributes to lobar hemorrhage. The coexistence of severe CAA and risk factors such as hypertension, anticoagulants or antiplatelets may readily induce lobar hemorrhage.

Apolipoprotein E polymorphism and the risk of aneurysmal subarachnoid hemorrhage in a South Indian population

Background

The rupture of a brain aneurysm causes bleeding in the subarachnoid space. This is known as aneurysmal subarachnoid hemorrhage (aSAH). We evaluated the association of apolipoprotein E (APOE) polymorphism and the risk of aSAH in a South Indian population.

Methods

The study was performed on 200 subjects with aSAH and 253 healthy control subjects. Blood samples (5 ml) were used to isolate DNA and genotyping was performed for rs7412 and rs429358 using a Taqman allelic discrimination assay. Statistical software R.3.0.11 was used to statistically analyze the data and a p value < 0.05 was considered as statistically significant.

Results

We found a significant association with the risk of aSAH in ε3/ ε4 genetic model (OR = 1.91, 95% CI = 1.16-3.14, p = 0.01). However, in the other genetic models and allele frequency, there was no significant association with the risk of aSAH. In subtyping, we found a significant association of ε2 allele frequency with posterior communicating artery (PCOM) aneurysm (OR = 3.59, 95% CI = 1.11-11.64, p = 0.03).

Conclusion

Our results suggest that APOE polymorphism has an influence on the risk of aSAH in this South Indian population, specifically in the PCOM subtype.

Apolipoprotein E as a Therapeutic Target in Alzheimer's Disease: A Review of Basic Research and Clinical Evidence

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that causes progressive cognitive decline. The majority of AD cases are sporadic and late-onset (>65 years old) making it the leading cause of dementia in the elderly. While both genetic and environmental factors contribute to the development of late-onset AD (LOAD), APOE polymorphism is a major genetic risk determinant for LOAD. In humans, the APOE gene has three major allelic variants: ε2, ε3, and ε4, of which APOE ε4 is the strongest genetic risk factor for LOAD, whereas APOE ε2 is protective. Mounting evidence suggests that APOE ε4 contributes to AD pathogenesis through multiple pathways including facilitated amyloid-β deposition, increased tangle formation, synaptic dysfunction, exacerbated neuroinflammation, and cerebrovascular defects. Since APOE modulates multiple biological processes through its corresponding protein apolipoprotein E (apoE), APOE gene and apoE properties have been a promising target for therapy and drug development against AD. In this review, we summarize the current evidence regarding how the APOE ε4 allele contributes to the pathogenesis of AD and how relevant therapeutic approaches can be developed to target apoE-mediated pathways in AD.

Impact of sex and APOE4 on cerebral amyloid angiopathy in Alzheimer's disease

Cerebral amyloid angiopathy (CAA) often coexists with Alzheimer's disease (AD). APOE4 is a strong genetic risk factor for both AD and CAA. Sex-dependent differences have been shown in AD as well as in cerebrovascular diseases. Therefore, we examined the effects of APOE4, sex, and pathological components on CAA in AD subjects. A total of 428 autopsied brain samples from pathologically confirmed AD cases were analyzed. CAA severity was histologically scored in inferior parietal, middle frontal, motor, superior temporal and visual cortexes. In addition, subgroups with severe CAA (n = 60) or without CAA (n = 39) were subjected to biochemical analysis of amyloid-β (Aβ) and apolipoprotein E (apoE) by ELISA in the temporal cortex. After adjusting for age, Braak neurofibrillary tangle stage and Thal amyloid phase, we found that overall CAA scores were higher in males than females. Furthermore, carrying one or more APOE4 alleles was associated with higher overall CAA scores. Biochemical analysis revealed that the levels of detergent-soluble and detergent-insoluble Aβ40, and insoluble apoE were significantly elevated in individuals with severe CAA or APOE4. The ratio of Aβ40/Aβ42 in insoluble fractions was also increased in the presence of CAA or APOE4, although it was negatively associated with male sex. Levels of insoluble Aβ40 were positively associated with those of insoluble apoE, which were strongly influenced by CAA status. Pertaining to insoluble Aβ42, the levels of apoE correlated regardless of CAA status. Our results indicate that sex and APOE genotypes differentially influence the presence and severity of CAA in AD, likely by affecting interaction and aggregation of Aβ40 and apoE.

Intracerebral haemorrhage in Down syndrome: protected or predisposed?

Down syndrome (DS), which arises from trisomy of chromosome 21, is associated with deposition of large amounts of amyloid within the central nervous system. Amyloid accumulates in two compartments: as plaques within the brain parenchyma and in vessel walls of the cerebral microvasculature. The parenchymal plaque amyloid is thought to result in an early onset

Alzheimer’s disease (AD) dementia, a phenomenon so common amongst people with DS that it could be considered a defining feature of the condition. The amyloid precursor protein ( APP) gene lies on chromosome 21 and its presence in three copies in DS is thought to largely drive the early onset AD. In contrast, intracerebral haemorrhage (ICH), the main clinical consequence of vascular amyloidosis, is a more poorly defined feature of DS. We review recent epidemiological data on stroke (including haemorrhagic stroke) in order to make comparisons with a rare form of familial AD due to duplication (i.e. having three copies) of the APP region on chromosome 21, here called ‘dup-APP’, which is associated with more frequent and severe ICH. We conclude that although people with DS are at increased risk of ICH, this is less common than in dup-APP, suggesting the presence of mechanisms that act protectively. We review these mechanisms and consider comparative research into DS and dup-APP that may yield further pathophysiological insight.

The role of APOE in cerebrovascular dysfunction

The ε4 allele of the apolipoprotein E gene (APOE4) is associated with cognitive decline during aging, is the greatest genetic risk factor for Alzheimer's disease and has links to other neurodegenerative conditions that affect cognition. Increasing evidence indicates that APOE genotypes differentially modulate the function of the cerebrovasculature (CV), with apoE and its receptors expressed by different cell types at the CV interface (astrocytes, pericytes, smooth muscle cells, brain endothelial cells). However, research on the role of apoE in CV dysfunction has not advanced as quickly as other apoE-modulated pathways. This review will assess what aspects of the CV are modulated by APOE genotypes during aging and under disease states, discuss potential mechanisms, and summarize the therapeutic significance of the topic. We propose that APOE4 induces CV dysfunction through direct signaling at the CV, and indirectly via modulation of peripheral and central pathways. Further, that APOE4 predisposes the CV to damage by, and exacerbates the effects of, additional risk factors (such as sex, hypertension, and diabetes). ApoE4-induced detrimental CV changes include reduced cerebral blood flow (CBF), modified neuron-CBF coupling, increased blood-brain barrier leakiness, cerebral amyloid angiopathy, hemorrhages and disrupted transport of nutrients and toxins. The apoE4-induced detrimental changes may be linked to pericyte migration/activation, astrocyte activation, smooth muscle cell damage, basement membrane degradation and alterations in brain endothelial cells.

Cerebrovascular disease in ageing and Alzheimer's disease

Cerebrovascular disease (CVD) and Alzheimer’s disease (AD) have more in common than their association with ageing. They share risk factors and overlap neuropathologically. Most patients with AD have Aβ amyloid angiopathy and degenerative changes affecting capillaries, and many have ischaemic parenchymal abnormalities. Structural vascular disease contributes to the ischaemic abnormalities in some patients with AD. However, the stereotyped progression of hypoperfusion in this disease, affecting first the precuneus and cingulate gyrus, then the frontal and temporal cortex and lastly the occipital cortex, suggests that other factors are more important, particularly in early disease. Whilst demand for oxygen and glucose falls in late disease, functional MRI, near infrared spectroscopy to measure the saturation of haemoglobin by oxygen, and biochemical analysis of myelin proteins with differential susceptibility to reduced oxygenation have all shown that the reduction in blood flow in AD is primarily a problem of inadequate blood supply, not reduced metabolic demand. Increasing evidence points to non-structural vascular dysfunction rather than structural abnormalities of vessel walls as the main cause of cerebral hypoperfusion in AD. Several mediators are probably responsible. One that is emerging as a major contributor is the vasoconstrictor endothelin-1 (EDN1). Whilst there is clearly an additive component to the clinical and pathological effects of hypoperfusion and AD, experimental and clinical observations suggest that the disease processes also interact mechanistically at a cellular level in a manner that exacerbates both. The elucidation of some of the mechanisms responsible for hypoperfusion in AD and for the interactions between CVD and AD has led to the identification of several novel therapeutic approaches that have the potential to ameliorate ischaemic damage and slow the progression of neurodegenerative disease.

Genetic risk factors for spontaneous intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is associated with the greatest morbidity and mortality of all stroke subtypes. Established risk factors for ICH include hypertension, alcohol use, current cigarette smoking, and use of oral anticoagulants and/or antiplatelet agents. Familial aggregation of ICH has been observed, and the heritability of ICH risk has been estimated at 44%. Few genes have been found to be associated with ICH at the population level, and much of the evidence for genetic risk factors for ICH comes from single studies conducted in relatively small and homogenous populations. In this Review, we summarize the current knowledge of genetic variants associated with primary spontaneous ICH. Two variants of the gene encoding apolipoprotein E (APOE) - which also contributes to the pathogenesis of cerebral amyloid angiopathy - are the most likely candidates for variants that increase the risk of ICH. Other promising candidates for risk alleles in ICH include variants of the genes ACE, PMF1/SLC25A44, COL4A2, and MTHFR. Other genetic variants, related to haemostasis, lipid metabolism, inflammation, and the CNS microenvironment, have been linked to ICH in single candidate gene studies. Although evidence for genetic contributions to the risk of ICH exists, we do not yet fully understand how and to what extent this information can be utilized to prevent and treat ICH.

Clinical Neuropathological Analysis of 10 Cases of Cerebral Amyloid Angiopathy-Related Cerebral Lobar Hemorrhage

Objective

The clinical and pathological characteristics of 10 cases of cerebral amyloid angiopathy (CAA)-related cerebral lobar hemorrhage (CLH) that was diagnosed at autopsy were investigated to facilitate the diagnosis of this condition.

Methods

The clinical characteristics of 10 cases of CAA-related CLH were retrospectively reviewed, and a neuropathological examination was performed on autopsy samples.

Results

The 10 cases included two with a single lobar hemorrhage and eight with multifocal lobar hemorrhages. In all of the cases, the hemorrhage bled into the subarachnoid space. Pathological examinations of the 10 cases revealed microaneurysms in two, double barrel-like changes in four, multifocal arteriolar clusters in five, obliterative onion skin-like intimal changes in four, fibrinoid necrosis of the vessels in seven, neurofibrillary tangles in eight, and senile plaques in five cases.

Conclusion

CAA-related CLHs were located primarily in the parietal, temporal, and occipital lobes. These hemorrhages normally consisted of multiple repeated CLHs that frequently bled into the subarachnoid space. CAA-associated microvascular lesions may be the pathological factor underlying CLH.

No neuropathological evidence for a direct topographical relation between microbleeds and cerebral amyloid angiopathy

Introduction

Cerebral microbleeds correspond to blood breakdown products, including hemosiderin-containing macrophages around small vessels on histological examination. Superficial lobar cerebral microbleeds are increasingly recognized on MRI as a biomarker of cerebral amyloid angiopathy but the direct association between amyloid-laden vessels burden and cerebral microbleeds has yet to be validated neuropathologically. To address this issue, we examined the frequency of histopathologically-defined cerebral microbleeds in different brain regions and their relationship with cerebral amyloid angiopathy in a large autopsy population.

Results

The frontal, parietal and occipital cortex as well as the adjacent white matter and basal ganglia of 113 consecutive autopsies were examined. Cerebral microbleedss were identified on haematoxylin-eosin-stained histological slides, cerebral amyloid angiopathy using anti-amyloid antibody. Cerebral microbleeds were present in 92.9 % of the cases and cerebral amyloid angiopathy in 44.3 % of them. Cerebral microbleeds were more frequent in parietal and frontal lobes followed by the occipital region and basal ganglia. In contrast, cerebral amyloid angiopathy was most frequent in the occipital lobe. There was no significant topographical association between cerebral amyloid angiopathy presence or severity and cerebral microbleeds in any brain region. In lobar areas, cerebral amyloid angiopathy was found in the cortex, predominantly affecting pial arteries and their superficial cortical branches, in contrast to microbleeds which were mainly in the white matter and occurred around deeper arteries and arterioles, including the subcortical segment of long penetrating branches of pial vessels.

Conclusions

Our study does not support a direct relation between cerebral microbleeds and cerebral amyloid angiopathy burden at the neuropathological level, raising intriguing questions on the potential pathophysiological mechanisms of cerebral microbleeds in the context of cerebral amyloid angiopathy or other small vessel disease pathology.

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.

Cerebral amyloid angiopathy with and without hemorrhage: evidence for different disease phenotypes

OBJECTIVE

To gain insight into different cerebral amyloid angiopathy (CAA) phenotypes and mechanisms, we investigated cortical superficial siderosis (CSS), a new imaging marker of the disease, and its relation with APOE genotype in patients with pathologically proven CAA, who presented with and without intracerebral hemorrhage (ICH).

METHODS

MRI scans of 105 patients with CAA pathologic confirmation and MRI were analyzed for CSS (focal, ≤3 sulci; disseminates, ≥4 sulci) and other imaging markers. We compared pathologic, imaging, and APOE genotype data between subjects with vs without ICH, and investigated associations between CSS and APOE genotype.

RESULTS

Our cohort consisted of 54 patients with CAA with symptomatic lobar ICH and 51 without ICH. APOE genotype was available in 53 patients. More than 90% of pathology samples in both groups had neuritic plaques, whereas neurofibrillary tangles were more commonly present in the patients without ICH (87% vs 42%, p < 0.0001). There was a trend for patients with CAA with ICH to more commonly have APOE ε2 (48.7% vs 21.4%, p = 0.075), whereas patients without ICH were more likely to be APOE ε4 carriers (85.7% vs 53.9%, p = 0.035). Disseminated CSS was considerably commoner in patients with ICH (33.3% vs 5.9%, p < 0.0001). In logistic regression, disseminated CSS was associated with APOE ε2 (but not APOE ε4) (odds ratio 5.83; 95% confidence interval 1.49-22.82, p = 0.011).

CONCLUSIONS

This neuropathologically defined CAA cohort suggests that CSS and APOE ε2 are related to the hemorrhagic expression of the disease; APOE ε4 is enriched in nonhemorrhagic CAA. Our study emphasizes the concept of different CAA phenotypes, suggesting divergent pathophysiologic mechanisms.

Cerebral amyloid angiopathy: emerging concepts

Cerebral amyloid angiopathy (CAA) involves cerebrovascular amyloid deposition and is classified into several types according to the amyloid protein involved. Of these, sporadic amyloid β-protein (Aβ)-type CAA is most commonly found in older individuals and in patients with Alzheimer's disease (AD). Cerebrovascular Aβ deposits accompany functional and pathological changes in cerebral blood vessels (CAA-associated vasculopathies). CAA-associated vasculopathies lead to development of hemorrhagic lesions [lobar intracerebral macrohemorrhage, cortical microhemorrhage, and cortical superficial siderosis (cSS)/focal convexity subarachnoid hemorrhage (SAH)], ischemic lesions (cortical infarction and ischemic changes of the white matter), and encephalopathies that include subacute leukoencephalopathy caused by CAA-associated inflammation/angiitis. Thus, CAA is related to dementia, stroke, and encephalopathies. Recent advances in diagnostic procedures, particularly neuroimaging, have enabled us to establish a clinical diagnosis of CAA without brain biopsies. Sensitive magnetic resonance imaging (MRI) methods, such as gradient-echo T2^* imaging and susceptibility-weighted imaging, are useful for detecting cortical microhemorrhages and cSS. Amyloid imaging with amyloid-binding positron emission tomography (PET) ligands, such as Pittsburgh Compound B, can detect CAA, although they cannot discriminate vascular from parenchymal amyloid deposits. In addition, cerebrospinal fluid markers may be useful, including levels of Aβ40 for CAA and anti-Aβ antibody for CAA-related inflammation. Moreover, cSS is closely associated with transient focal neurological episodes (TFNE). CAA-related inflammation/angiitis shares pathophysiology with amyloid-related imaging abnormalities (ARIA) induced by Aβ immunotherapies in AD patients. This article reviews CAA and CAA-related disorders with respect to their epidemiology, pathology, pathophysiology, clinical features, biomarkers, diagnosis, treatment, risk factors, and future perspectives.