Interest of CSF biomarker analysis in possible cerebral amyloid angiopathy cases defined by the modified Boston criteria

CSF and plasma biomarkers in cerebral amyloid angiopathy: A single-center study and a systematic review/meta-analysis

INTRODUCTION

There are limited data regarding cerebrospinal fluid (CSF) and plasma biomarkers among patients with Cerebral Amyloid Angiopathy (CAA). We sought to investigate the levels of four biomarkers [β-amyloids (Aβ42 and Aβ40), total tau (tau) and phosphorylated tau (p-tau)] in CAA patients compared to healthy controls (HC) and patients with Alzheimer Disease (AD).

PATIENTS AND METHODS

A systematic review and meta-analysis of published studies, including also a 5 year single-center cohort study, with available data on CSF and plasma biomarkers in symptomatic sporadic CAA versus HC and AD was conducted. Biomarkers' comparisons were investigated using random-effects models based on the ratio of mean (RoM) biomarker concentrations. RoM < 1 and RoM > 1 indicate lower and higher biomarker concentration in CAA compared to another population, respectively.

RESULTS

We identified nine cohorts, comprising 327 CAA patients (mean age: 71 ± 5 years; women: 45%) versus 336 HC (mean age: 65 ± 5 years; women: 45%) and 384 AD patients (mean age: 68 ± 3 years; women: 53%) with available data on CSF biomarkers. CSF Aβ42 levels [RoM: 0.47; 95% CI: 0.36-0.62; p < 0.0001], Aβ40 levels [RoM: 0.70; 95% CI: 0.63-0.79; p < 0.0001] and the ratio Aβ42/Aβ40 [RoM: 0.62; 95% CI: 0.39-0.98; p = 0.0438] differentiated CAA from HC. CSF Aβ40 levels [RoM: 0.73; 95% CI: 0.64-0.83; p = 0.0003] differentiated CAA from AD. CSF tau and p-tau levels differentiated CAA from HC [RoM: 1.71; 95% CI: 1.41-2.09; p = 0.0002 and RoM: 1.44; 95% CI: 1.20-1.73; p = 0.0014, respectively] and from AD [RoM: 0.65; 95% CI: 0.58-0.72; p < 0.0001 and RoM: 0.64; 95% CI: 0.57-0.71; p < 0.0001, respectively]. Plasma Aβ42 [RoM: 1.14; 95% CI: 0.89-1.45; p = 0.2079] and Aβ40 [RoM: 1.07; 95% CI: 0.91-1.25; p = 0.3306] levels were comparable between CAA and HC.

CONCLUSIONS

CAA is characterized by a distinct CSF biomarker pattern compared to HC and AD. CSF Aβ40 levels are lower in CAA compared to HC and AD, while tau and p-tau levels are higher in CAA compared to HC, but lower in comparison to AD patients.

Comparative methods for quantifying plasma biomarkers in Alzheimer's disease: Implications for the next frontier in cerebral amyloid angiopathy diagnostics

Plasma amyloid beta (Aβ) and tau are emerging as accessible biomarkers for Alzheimer's disease (AD). However, many assays exist with variable test performances, highlighting the need for a comparative assessment to identify the most valid assays for future use in AD and to apply to other settings in which the same biomarkers may be useful, namely, cerebral amyloid angiopathy (CAA). CAA is a progressive cerebrovascular disease characterized by deposition of Aβ40 and Aβ42 in cortical and leptomeningeal vessels. Novel immunotherapies for AD can induce amyloid-related imaging abnormalities resembling CAA-related inflammation. Few studies have evaluated plasma biomarkers in CAA. Identifying a CAA signature could facilitate diagnosis, prognosis, and a safer selection of patients with AD for emerging immunotherapies. This review evaluates studies that compare the diagnostic test performance of plasma biomarker techniques in AD and cerebrovascular and plasma biomarker profiles of CAA; it also discusses novel hypotheses and future avenues for plasma biomarker research in CAA.

Using Neuroimaging to Study Cerebral Amyloid Angiopathy and Its Relationship to Alzheimer's Disease

Cerebral amyloid angiopathy (CAA) is characterized by amyloid-β aggregation in the media and adventitia of the leptomeningeal and cortical blood vessels. CAA is one of the strongest vascular contributors to Alzheimer's disease (AD). It frequently co-occurs in AD patients, but the relationship between CAA and AD is incompletely understood. CAA may drive AD risk through damage to the neurovascular unit and accelerate parenchymal amyloid and tau deposition. Conversely, early AD may also drive CAA through cerebrovascular remodeling that impairs blood vessels from clearing amyloid-β. Sole reliance on autopsy examination to study CAA limits researchers' ability to investigate CAA's natural disease course and the effect of CAA on cognitive decline. Neuroimaging allows for in vivo assessment of brain function and structure and can be leveraged to investigate CAA staging and explore its associations with AD. In this review, we will discuss neuroimaging modalities that can be used to investigate markers associated with CAA that may impact AD vulnerability including hemorrhages and microbleeds, blood-brain barrier permeability disruption, reduced cerebral blood flow, amyloid and tau accumulation, white matter tract disruption, reduced cerebrovascular reactivity, and lowered brain glucose metabolism. We present possible areas for research inquiry to advance biomarker discovery and improve diagnostics.

The Role of Amyloid-β, Tau, and α-Synuclein Proteins as Putative Blood Biomarkers in Patients with Cerebral Amyloid Angiopathy

BACKGROUND

Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder characterized by the deposition of amyloid-β protein (Aβ) within brain blood vessels that develops in elderly people and Alzheimer's disease (AD) patients. Therefore, the investigation of biomarkers able to differentiate CAA patients from AD patients and healthy controls (HC) is of great interest, in particular in peripheral fluids.

OBJECTIVE

The current study aimed to detect the neurodegenerative disease (ND)-related protein (i.e., Aβ 1 - 40, Aβ 1 - 42, tau, and α-synuclein) levels in both red blood cells (RBCs) and plasma of CAA patients and HC, evaluating their role as putative peripheral biomarkers for CAA.

METHODS

For this purpose, the proteins' concentration was quantified in RBCs and plasma by homemade immunoenzymatic assays in an exploratory cohort of 20 CAA patients and 20 HC.

RESULTS

The results highlighted a significant increase of Aβ 1 - 40 and α-synuclein concentrations in both RBCs and plasma of CAA patients, while higher Aβ 1 - 42 and t-tau levels were detected only in RBCs of CAA individuals compared to HC. Moreover, Aβ 1 - 42/Aβ 1 - 40 ratio increased in RBCs and decreased in plasma of CAA patients. The role of these proteins as candidate peripheral biomarkers easily measurable with a blood sample in CAA needs to be confirmed in larger studies.

CONCLUSION

In conclusion, we provide evidence concerning the possible use of blood biomarkers for contributing to CAA diagnosis and differentiation from other NDs.

Blood amyloid and tau biomarkers as predictors of cerebrospinal fluid profiles

Introduction

Blood biomarkers represent a major advance for improving the management, diagnosis, and monitoring of Alzheimer's disease (AD). However, their context of use in relation to routine cerebrospinal fluid (CSF) analysis for the quantification of amyloid peptides and tau proteins remains to be determined.

Methods

We studied in two independent cohorts, the performance of blood biomarkers in detecting “nonpathological” (A−/T−/N−), amyloid (A+) or neurodegenerative (T+ /N+) CSF profiles.

Results

Plasma Aβ_1–42/Aβ_1–40 ratio and phosphorylated tau (p-tau(181)) were independent and complementary predictors of the different CSF profile and in particular of the nonpathological (A−/T−/N−) profile with a sensitivity and specificity close to 85%. These performances and the corresponding biomarker thresholds were significantly different from those related to AD detection.

Conclusion

The use of blood biomarkers to identify patients who may benefit from secondary CSF testing represents an attractive stratification strategy in the clinical management of patients visiting memory clinics. This could reduce the need for lumbar puncture and foreshadow the use of blood testing on larger populations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00702-022-02474-9.

Cerebrospinal Fluid Biomarkers in Cerebral Amyloid Angiopathy: New Data and Quantitative Meta-Analysis

Background

To evaluate the diagnostic accuracy of cerebrospinal fluid (CSF) biomarkers in patients with probable cerebral amyloid angiopathy (CAA) according to the modified Boston criteria in a retrospective multicentric cohort.

Methods

Beta-amyloid 1-40 (Aβ40), beta-amyloid 1-42 (Aβ42), total tau (t-tau), and phosphorylated tau 181 (p-tau¹⁸¹) were measured in 31 patients with probable CAA, 28 patients with Alzheimer’s disease (AD), and 30 controls. Receiver-operating characteristics (ROC) analyses were performed for the measured parameters as well as the Aβ42/40 ratio to estimate diagnostic parameters. A meta-analysis of all amenable published studies was conducted.

Results

In our data Aβ42/40 (AUC 0.88) discriminated best between CAA and controls while Aβ40 did not perform well (AUC 0.63). Differentiating between CAA and AD, p-tau¹⁸¹ (AUC 0.75) discriminated best in this study while Aβ40 (AUC 0.58) and Aβ42 (AUC 0.54) provided no discrimination. In the meta-analysis, Aβ42/40 (AUC 0.90) showed the best discrimination between CAA and controls followed by t-tau (AUC 0.79), Aβ40 (AUC 0.76), and p-tau¹⁸¹ (AUC 0.71). P-tau¹⁸¹ (AUC 0.76), Aβ40 (AUC 0.73), and t-tau (AUC 0.71) differentiated comparably between AD and CAA while Aβ42 (AUC 0.54) did not. In agreement with studies examining AD biomarkers, Aβ42/40 discriminated excellently between AD and controls (AUC 0.92–0.96) in this study as well as the meta-analysis.

Conclusion

The analyzed parameters differentiate between controls and CAA with clinically useful accuracy (AUC > ∼0.85) but not between CAA and AD. Since there is a neuropathological, clinical and diagnostic continuum between CAA and AD, other diagnostic markers, e.g., novel CSF biomarkers or other parameters might be more successful.

Associating Alzheimer’s disease pathology with its cerebrospinal fluid biomarkers

Alzheimer’s disease cerebrospinal fluid (CSF) biomarkers 42 amino acid long amyloid-β peptide (Aβ1-42), total tau protein (T-tau), and tau protein phosphorylated at threonine 181 (P-tau181) are considered surrogate biomarkers of Alzheimer’s disease pathology, and significantly improve diagnostic accuracy. Their ability to reflect neuropathological changes later in the disease course is not well characterized. This study aimed to assess the potential of CSF biomarkers measured in mid- to late-stage Alzheimer’s disease to reflect post mortem neuropathological changes. Individuals were selected from 2 autopsy cohorts of Alzheimer’s disease patients in Antwerp and Amsterdam. Neuropathological diagnosis was performed according to the updated consensus National Institute on Aging-Alzheimer’s Association guidelines by Montine et al, which includes quantification of amyloid beta plaque, neurofibrillary tangle, and neuritic plaque load. CSF samples were analyzed for Aβ1-42, T-tau, and P-tau181 by ELISA. 114 cases of pure definite Alzheimer’s disease were included in the study (mean age 74 years, disease duration 6 years at CSF sampling, 50% females). Median interval between CSF sampling and death was one year. We found no association between Aβ1-42 and Alzheimer’s disease neuropathological change profile. In contrast, an association of P-tau181 and T-tau with Alzheimer’s disease neuropathological change profile was observed. P-tau181 was associated with all three individual Montine scores, and the associations became stronger and more significant as the interval between lumbar puncture and death increased. T-tau was also associated with all three Montine scores, but in individuals with longer intervals from lumbar puncture to death only. Stratification of the cohort according to APOE ε4 carrier status revealed that the associations applied mostly to APOE ε4 non-carriers. Our data suggest that similarly to what has been reported for Aβ1-42, plateau levels of P-tau181 and T-tau are reached during the disease course, albeit at later disease stages, reducing the potential of tau biomarkers to monitor Alzheimer’s disease pathology as the disease progresses. As a consequence, CSF biomarkers, which are performant for clinical diagnosis of early Alzheimer’s disease, may not be well suited for staging or monitoring Alzheimer’s disease pathology as it progresses through later stages.

Association Between Plasma Biomarkers of Amyloid, Tau, and Neurodegeneration with Cerebral Microbleeds

BACKGROUND

Cerebral microbleeds (CMBs) are a common vascular pathology associated with future intracerebral hemorrhage. Plasma biomarkers of amyloid, tau, and neurodegeneration may provide a screening avenue to identify those with CMBs, but evidence is conflicting.

OBJECTIVE

To determine the association between plasma biomarkers (Aβ40, Aβ42, t-tau, p-tau181, p-tau217, neurofilament light chain (NfL)) and CMBs in a population-based study of aging and whether these biomarkers predict higher signal on Aβ-PET imaging in patients with multiple CMBs.

METHODS

712 participants from the Mayo Clinic Study of Aging with T2* GRE MRI and plasma biomarkers were included. Biomarkers were analyzed utilizing Simoa (Aβ40, Aβ42, t-tau, NfL) or Meso Scale Discovery (p-tau181, p-tau217) platforms. Cross-sectional associations between CMBs, plasma biomarkers and Aβ-PET were evaluated using hurdle models and multivariable regression models.

RESULTS

Among the 188 (26%) individuals with≥1 CMB, a lower plasma Aβ42/Aβ40 ratio was associated with more CMBs after adjusting for covariables (IRR 568.5 95% CI 2.8-116,127). No other biomarkers were associated with risk or number CMBs. In 81 individuals with≥2 CMBs, higher plasma t-tau, p-tau181, and p-tau217 all were associated with higher Aβ-PET signal, with plasma p-tau217 having the strongest predictive value (r2 0.603, AIC -53.0).

CONCLUSION

Lower plasma Aβ42/Aβ40 ratio and higher plasma p-tau217 were associated with brain amyloidosis in individuals with CMBs from the general population. Our results suggest that in individuals with multiple CMBs and/or lobar intracranial hemorrhage that a lower plasma Aβ42/Aβ40 ratio or elevated p-tau217 may indicate underlying cerebral amyloid angiopathy.

Screening for cerebral amyloid angiopathy based on serological biomarkers analysis using a dielectrophoretic force-driven biosensor platform

We aimed to analyze plasma amyloid-β (Aβ)_1-40 and Aβ_1-42 using a highly sensitive dielectrophoretic-driven biosensor platform to demonstrate the possibility of precise cerebral amyloid angiopathy (CAA) diagnosis in participants classified according to Aβ-positron emission tomography (PET) positivity and the neuroimaging criteria for CAA. We prospectively recruited 25 people with non-Alzheimer's disease (non-AD) and 19 patients with Alzheimer's disease (AD), which were further classified into the CAA- and CAA+ (possible and probable CAA) groups according to the modified Boston criteria. Patients underwent plasma Aβ analysis using a highly sensitive nano-biosensor platform, Aβ-PET scanning, and detailed neuropsychological testing. As a result, the average signal levels of Aβ_1-42/1-40 differed significantly between the non-AD and AD groups, and the CAA+ group exhibited significantly higher Aβ_1-40 signal levels than the CAA- group in both non-AD and AD groups. The concordance between the Aβ_1-40 signal level and the neuroimaging criteria for CAA was nearly perfect, with areas under the curve of 0.954 (95% confidence interval (CI) 0.856-1.000), 0.969 (0.894-1.000), 0.867 (0.648-1.000), and 1.000 (1.000-1.000) in the non-AD/CAA- vs. non-AD/possible CAA, non-AD/CAA- vs. non-AD/probable CAA, AD/CAA- vs. AD/possible CAA, and AD/CAA- vs. AD/probable CAA groups, respectively. Higher Aβ_1-40 signal levels were significantly associated with the presence of CAA according to regression analyses, and the neuroimaging pattern analysis partly supported this result. Our findings suggest that measuring plasma Aβ_1-40 signal levels using a highly sensitive biosensor platform could be a useful non-invasive CAA diagnostic method.

Performance of the plasma Aβ42/Aβ40 ratio, measured with a novel HPLC-MS/MS method, as a biomarker of amyloid PET status in a DPUK-KOREAN cohort

Background

We assessed the feasibility of plasma Aβ42/Aβ40 determined using a novel liquid chromatography-mass spectrometry method (LC-MS) as a useful biomarker of PET status in a Korean cohort from the DPUK Study.

Methods

A total of 580 participants belonging to six groups, Alzheimer’s disease dementia (ADD, n = 134), amnestic mild cognitive impairment (aMCI, n = 212), old controls (OC, n = 149), young controls (YC, n = 15), subcortical vascular cognitive impairment (SVCI, n = 58), and cerebral amyloid angiopathy (CAA, n = 12), were included in this study. Plasma Aβ40 and Aβ42 were quantitated using a new antibody-free, LC-MS, which drastically reduced the sample preparation time and cost. We performed receiver operating characteristic (ROC) analysis to develop the cutoff of Aβ42/Aβ40 and investigated its performance predicting centiloid-based PET positivity (PET+).

Results

Plasma Aβ42/Aβ40 were lower for PET+ individuals in ADD, aMCI, OC, and SVCI (p < 0.001), but not in CAA (p = 0.133). In the group of YC, OC, aMCI, and ADD groups, plasma Aβ42/Aβ40 predicted PET+ with an area under the ROC curve (AUC) of 0.814 at a cutoff of 0.2576. When adding age, APOE4, and diagnosis, the AUC significantly improved to 0.912.

Conclusion

Plasma Aβ42/Aβ40, as measured by this novel LC-MS method, showed good discriminating performance based on PET positivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00911-7.

Clinical and radiological features of cerebral amyloid angiopathy-related inflammation

OBJECTIVES

We want to report the clinical and radiological features of our cohort of patients diagnosed with cerebral amyloid angiopathy-related inflammation (CAA-RI) according to the Boston Criteria and additionally to disclose some atypical clinical characteristics observed in some of them to provide more knowledge about this novel entity.

METHODS

We describe 5 patients with probable CAA-RI according to a validation study of proposed criteria for the diagnosis of CAA-RI at University Hospital Josep Trueta of Girona. We consider some clinical characteristics which include the response to immunotherapy, CSF findings, and MRI features. The patient's neurologic outcomes were assessed using the modified Rankin Scale (mRS).

RESULTS

We collected 5 patients admitted for probable CAA-RI. Most were women and the median age was 72 years. The median mRS score at the onset of disease was 1. Parietal lobes were most affected clinically as well as radiologically. Two patients had intracranial hemorrhage. Decreased levels of CSF amyloid beta 42 and 40 protein were observed. Corticosteroids were used in four patients and a remarkable improvement was observed in all of them.

CONCLUSIONS

CAA-RI is a condition that predominantly affects parietal lobes according to our case series and this involvement seems to be directly related to a greater burden of microbleeds, cortical siderosis, WMH, and lobar hemorrhages on these lobes. Decreased levels of CSF amyloid beta protein plus increased total tau protein should be considered as part of the diagnostic criteria of CAA-RI. We recommend corticosteroids using, as they have been demonstrated to be very effective in managing CAA-RI.

Cerebrospinal Fluid Biomarkers in Cerebral Amyloid Angiopathy

Background:

There is limited data on cerebrospinal fluid (CSF) biomarkers in sporadic amyloid-β (Aβ) cerebral amyloid angiopathy (CAA).

Objective:

To determine the profile of biomarkers relevant to neurodegenerative disease in the CSF of patients with CAA.

Methods:

We performed a detailed comparison of CSF markers, comparing patients with CAA, Alzheimer’s disease (AD), and control (CS) participants, recruited from the Biomarkers and Outcomes in CAA (BOCAA) study, and a Specialist Cognitive Disorders Service.

Results:

We included 10 CAA, 20 AD, and 10 CS participants (mean age 68.6, 62.5, and 62.2 years, respectively). In unadjusted analyses, CAA patients had a distinctive CSF biomarker profile, with significantly lower (p < 0.01) median concentrations of Aβ₃₈, Aβ₄₀, Aβ₄₂, sAβPPα, and sAβPPβ. CAA patients had higher levels of neurofilament light (NFL) than the CS group (p < 0.01), but there were no significant differences in CSF total tau, phospho-tau, soluble TREM2 (sTREM2), or neurogranin concentrations. AD patients had higher total tau, phospho-tau and neurogranin than CS and CAA groups. In age-adjusted analyses, differences for the CAA group remained for Aβ₃₈, Aβ₄₀, Aβ₄₂, and sAβPPβ. Comparing CAA patients with amyloid-PET positive (n = 5) and negative (n = 5) scans, PET positive individuals had lower (p < 0.05) concentrations of CSF Aβ₄₂, and higher total tau, phospho-tau, NFL, and neurogranin concentrations, consistent with an “AD-like” profile.

Conclusion:

CAA has a characteristic biomarker profile, suggestive of a global, rather than selective, accumulation of amyloid species; we also provide evidence of different phenotypes according to amyloid-PET positivity. Further replication and validation of these preliminary findings in larger cohorts is needed.

Current Management and Therapeutic Strategies for Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is characterized by accumulation of amyloid β (Aβ) in walls of leptomeningeal vessels and cortical capillaries in the brain. The loss of integrity of these vessels caused by cerebrovascular Aβ deposits results in fragile vessels and lobar intracerebral hemorrhages. CAA also manifests with progressive cognitive impairment or transient focal neurological symptoms. Although development of therapeutics for CAA is urgently needed, the pathogenesis of CAA remains to be fully elucidated. In this review, we summarize the epidemiology, pathology, clinical and radiological features, and perspectives for future research directions in CAA therapeutics. Recent advances in mass spectrometric methodology combined with vascular isolation techniques have aided understanding of the cerebrovascular proteome. In this paper, we describe several potential key CAA-associated molecules that have been identified by proteomic analyses (apolipoprotein E, clusterin, SRPX1 (sushi repeat-containing protein X-linked 1), TIMP3 (tissue inhibitor of metalloproteinases 3), and HTRA1 (HtrA serine peptidase 1)), and their pivotal roles in Aβ cytotoxicity, Aβ fibril formation, and vessel wall remodeling. Understanding the interactions between cerebrovascular Aβ deposits and molecules that accumulate with Aβ may lead to discovery of effective CAA therapeutics and to the identification of biomarkers for early diagnosis.

Comparison of Plasma Lipoprotein Composition and Function in Cerebral Amyloid Angiopathy and Alzheimer's Disease

Cerebral amyloid angiopathy (CAA) refers to beta-amyloid (Aβ) deposition in brain vessels and is clinically the main cause of lobar intracerebral hemorrhage (ICH). Aβ can also accumulate in brain parenchyma forming neuritic plaques in Alzheimer’s disease (AD). Our study aimed to determine whether the peripheral lipid profile and lipoprotein composition are associated with cerebral beta-amyloidosis pathology and may reflect biological differences in AD and CAA. For this purpose, lipid and apolipoproteins levels were analyzed in plasma from 51 ICH-CAA patients (collected during the chronic phase of the disease), 60 AD patients, and 60 control subjects. Lipoproteins (VLDL, LDL, and HDL) were isolated and their composition and pro/antioxidant ability were determined. We observed that alterations in the lipid profile and lipoprotein composition were remarkable in the ICH-CAA group compared to control subjects, whereas the AD group presented no specific alterations compared with controls. ICH-CAA patients presented an atheroprotective profile, which consisted of lower total and LDL cholesterol levels. Plasma from chronic ICH-CAA patients also showed a redistribution of ApoC-III from HDL to VLDL and a higher ApoE/ApoC-III ratio in HDL. Whether these alterations reflect a protective response or have a causative effect on the pathology requires further investigation.

Cerebrospinal fluid biomarkers and apolipoprotein E genotype in cerebral amyloid angiopathy. A narrative review

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Lower Cerebrospinal Fluid Levels of Aβ₄₀ and Aβ₄₂ in Cerebral Amyloid Angiopathy compared with Alzheimer Disease and Healthy Controls.

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Cortical Superficial Siderosis-extent and lower levels of Aβ₄₂ could be prognostic for the severity of Cerebral Amyloid Angiopathy.

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Apolipoprotein – E Genotype plays an important role in the pathophysiology of Cerebral Amyloid Angiopathy.

Sporadic cerebral amyloid angiopathy (CAA) is a cerebral small vessel disease, characterized by the deposition of β-amyloid within the cortical and leptomeningeal blood vessel walls. It has attracted interest concerning new therapeutic perspectives. However, there are scarce data regarding the cerebrospinal fluid biomarkers (CSF) and genetic factors in sporadic CAA.

In this narrative review, we investigated the literature regarding the cerebrospinal fluid core biomarkers profile of patients with probable or possible CAA and its subtype, the CAA- related inflammation (CAA-ri), taking into account the clinical and radiological characteristics of the patients. We also analyzed the Apolipoprotein E (APOE) genotype differentiations among the different subtypes of cerebral amyloid angiopathy.

Our results demonstrate specific CSF patterns of β-amyloid (Aβ₄₂ and Aβ₄₀) and tau-proteins (t-tau and p-tau) which may serve as molecular biomarkers for CAA/ CAA-ri and could prove helpful for novel therapeutic procedures. Specifically, decreased levels of Aβ₄₀ and Aβ₄₂ in both CAA and CAA-ri, mildly increased concentrations of tau protein in patients with CAA-ri and a strong association between APOE ε4/ε4 genotype and CAA-ri are the main findings.

MRI phenotyping of underlying cerebral small vessel disease in mixed hemorrhage patients

OBJECTIVE

To investigate underlying cerebral small vessel disease (CSVD) in patients with mixed cerebral hemorrhages patterns and phenotype them according to the contribution of the two most common sporadic CSVD subtypes: cerebral amyloid angiopathy (CAA) vs. hypertensive arteriopathy (HA).

METHODS

Brain MRIs of patients with intracerebral hemorrhages (ICHs) and/or cerebral microbleeds (CMBs) were assessed for the full spectrum of CSVD markers using validated scales: ICHs, CMBs, cortical superficial siderosis (cSS), white matter hyperintensities, MRI-visible perivascular spaces (PVS). PVS predominance pattern was grouped as centrum-semiovale (CSO)-PVS predominance, basal-ganglia (BG)-PVS predominance, CSO-PVS and BG-PVS equality. Patients with mixed cerebral hemorrhages were classified into mixed CAA-pattern or mixed HA-pattern according to the existence of cSS and/or a CSO-PVS predominance pattern and comparisons were performed.

RESULTS

We included 110 patients with CAA (strictly lobar ICHs/CMBs), 33 with HA (strictly deep ICHs/CMBs) and 97 with mixed lobar/deep ICHs/CMBs. Mixed patients were more similar to HA with respect to their MRI-CSVD markers, vascular risk profile and cerebrospinal fluid (CSF) measures. In the mixed patients, 33 (34%) had cSS, a CSO-PVS predominance pattern, or both, and were defined as mixed CAA-pattern cases. The mixed CAA-pattern patients were more alike CAA patients regarding their MRI-CSVD markers, CSF and genetic profile.

CONCLUSION

Our findings suggest that the heterogeneous group of patients with mixed cerebral hemorrhages distribution can be further phenotyped according to the predominant underlying CSVD. cSS presence and a CSO-PVS predominance pattern could serve as strongly suggestive markers of a contribution from CAA among patients with mixed hemorrhages.

Cerebrospinal fluid A beta 1-40 peptides increase in Alzheimer's disease and are highly correlated with phospho-tau in control individuals

BACKGROUND

Amyloid pathology, which is one of the characteristics of Alzheimer's disease (AD), results from altered metabolism of the beta-amyloid (Aβ) peptide in terms of synthesis, clearance, or aggregation. A decrease in cerebrospinal fluid (CSF) level Aβ1-42 is evident in AD, and the CSF ratio Aβ42/Aβ40 has recently been identified as one of the most reliable diagnostic biomarkers of amyloid pathology. Variations in inter-individual levels of Aβ1-40 in the CSF have been observed in the past, but their origins remain unclear. In addition, the variation of Aβ40 in the context of AD studied in several studies has yielded conflicting results.

METHODS

Here, we analyzed the levels of Aβ1-40 using multicenter data obtained on 2466 samples from six different cohorts in which CSF was collected under standardized protocols, centrifugation, and storage conditions. Tau and p-tau (181) concentrations were measured using commercially available in vitro diagnostic immunoassays. Concentrations of CSF Aβ1-42 and Aβ1-40 were measured by ELISA, xMAP technology, chemiluminescence immunoassay (CLIA), and mass spectrometry. Statistical analyses were calculated for parametric and non-parametric comparisons, linear regression, correlation, and odds ratios. The statistical tests were adjusted for the effects of covariates (age, in particular).

RESULTS

Regardless of the analysis method used and the cohorts, a slight but significant age-independent increase in the levels of Aβ40 in CSF was observed in AD. We also found a strong positive correlation between the levels of Aβ1-40 and p-tau (181) in CSF, particularly in control patients.

CONCLUSIONS

These results indicate that an increase in the baseline level of amyloid peptides, which are associated with an increase in p-tau (181), may be a biological characteristic and possibly a risk factor for AD. Further studies will be needed to establish a causal link between increased baseline levels of Aβ40 and the development of the disease.

Clinical and radiological differences between patients with probable cerebral amyloid angiopathy and mixed cerebral microbleeds

BACKGROUND

The key imaging features of cerebral amyloid angiopathy (CAA) are lobar, cortical, or cortico-subcortical microbleeds, macrohaemorrhages and cortical superficial siderosis (cSS). In contrast, hypertensive angiopathy is characterized by (micro) haemorrhages in the basal ganglia, thalami, periventricular white matter or the brain stem. Another distinct form of haemorrhagic microangiopathy is mixed cerebral microbleeds (mixed CMB) with features of both CAA and hypertensive angiopathy. The distinction between the two entities (CAA and mixed CMB) is clinically relevant because the risk of haemorrhage and stroke should be well balanced if oral anticoagulation is indicated in CAA patients. We aimed to comprehensively compare these two entities.

METHODS

Patients with probable CAA according to the modified Boston criteria and mixed CMB without macrohaemorrhage were retrospectively identified from our database. Comprehensive comparison regarding clinical and radiological parameters was performed between the two cohorts.

RESULTS

Patients with CAA were older (78 ± 8 vs. 74 ± 9 years, p = 0.036) and had a higher prevalence of cSS (19% vs. 4%, p = 0.027) but a lower prevalence of lacunes (73% vs. 50%, p = 0.018) and deep lacunes (23% vs. 51%, p = 0.0003) compared to patients with mixed CMB. Logistic regression revealed an association between the presence of deep lacunes and mixed CMB. The other collected parameters did not reveal a significant difference between the two groups.

CONCLUSIONS

CAA and mixed CMB demonstrate radiological differences in the absence of macrohaemorrhages. However, more clinically available biomarkers are needed to elucidate the contribution of CAA and hypertensive angiopathy in mixed CMB patients.

Apolipoprotein D: a potential biomarker for cerebral amyloid angiopathy

AIMS

We investigated the potential of apolipoprotein D (apoD) as cerebrospinal fluid (CSF) biomarker for cerebral amyloid angiopathy (CAA) after confirmation of its association with CAA pathology in human brain tissue.

METHODS

The association of apoD with CAA pathology was analysed in human occipital lobe tissue of CAA (n = 9), Alzheimer's disease (AD) (n = 11) and healthy control cases (n = 11). ApoD levels were quantified in an age- and sex-matched CSF cohort of CAA patients (n = 31), AD patients (n = 27) and non-neurological controls (n = 67). The effects of confounding factors (age, sex, serum levels) on apoD levels were studied using CSF of non-neurological controls (age range 16-85 years), and paired CSF and serum samples.

RESULTS

ApoD was strongly associated with amyloid deposits in vessels, but not with parenchymal plaques in human brain tissue. CSF apoD levels correlated with age and were higher in men than women in subjects >50 years. The apoD CSF/serum ratio correlated with the albumin ratio. When controlling for confounding factors, CSF apoD levels were significantly lower in CAA patients compared with controls and compared with AD patients (P = 0.0008).

CONCLUSIONS

Our data show that apoD is specifically associated with CAA pathology and may be a CSF biomarker for CAA, but clinical application is complicated due to dependency on age, sex and blood-CSF barrier integrity. Well-controlled follow-up studies are required to determine whether apoD can be used as reliable biomarker for CAA.

Hypertensive Arteriopathy and Cerebral Amyloid Angiopathy in Patients with Cognitive Decline and Mixed Cerebral Microbleeds

BACKGROUND

Hypertensive arteriopathy (HA) and cerebral amyloid angiopathy (CAA) may contribute to the development of mixed cerebral microbleeds (CMBs). Recently, the total small vessel disease (SVD) scores for HA and CAA were proposed, which are determined by a combination of MRI markers to reflect overall severity of these microangiopathies.

OBJECTIVE

We investigated whether or not total HA-SVD and CAA-SVD scores could be used to predict overlap of HA and CAA in patients with mixed CMBs.

METHODS

Fifty-three subjects with mixed CMBs were retrospectively analyzed. MRI markers (CMBs, lacunes, perivascular space, white matter hyperintensity [WMH] and cortical superficial siderosis [cSS]) were assessed. The HA-SVD score and CAA-SVD score were obtained for each subject. Anterior or posterior WMH was also assessed using the age-related white matter changes scale.

RESULTS

The two scores were positively correlated (ρ= 0.449, p < 0.001). The prevalence of lobar dominant CMB distribution (p < 0.001) and lacunes in the centrum semiovale (p < 0.001) and the severity of WMH in the parieto-occipital lobes (p = 0.004) were significantly higher in the high CAA-SVD score group. cSS was found in four patients with high CAA-SVD score who showed lobar-dominant CMB distribution and severe posterior WMH.

CONCLUSION

Mixed CMBs are mainly due to HA. Assessing both two scores may predict the overlap of HA and CAA in individuals with mixed CMBs. Patients with a high CAA-SVD score may have some degree of advanced CAA, especially when lobar predominant CMBs, severe posterior WMH, lobar lacunes, or cSS are observed.

Reduced Levels of Cerebrospinal Fluid/Plasma Aβ40 as an Early Biomarker for Cerebral Amyloid Angiopathy in RTg-DI Rats

The accumulation of fibrillar amyloid β-protein (Aβ) in blood vessels of the brain, the condition known as cerebral amyloid angiopathy (CAA), is a common small vessel disease that promotes cognitive impairment and is strongly associated with Alzheimer’s disease. Presently, the clinical diagnosis of this condition relies on neuroimaging markers largely associated with cerebral macro/microbleeds. However, these are markers of late-stage disease detected after extensive cerebral vascular amyloid accumulation has become chronic. Recently, we generated a novel transgenic rat model of CAA (rTg-DI) that recapitulates multiple aspects of human CAA disease with the progressive accumulation of cerebral vascular amyloid, largely composed of Aβ40, and the consistent emergence of subsequent microbleeds. Here, we investigated the levels of Aβ40 in the cerebrospinal fluid (CSF) and plasma of rTg-DI rats as CAA progressed from inception to late stage disease. The levels of Aβ40 in CSF and plasma precipitously dropped at the early onset of CAA accumulation at three months of age and continued to decrease with the progression of disease. Notably, the reduction in CSF/plasma Aβ40 levels preceded the emergence of cerebral microbleeds, which first occurred at about six months of age, as detected by in vivo magnetic resonance imaging and histological staining of brain tissue. These findings support the concept that reduced CSF/plasma levels of Aβ40 could serve as a biomarker for early stage CAA disease prior to the onset of cerebral microbleeds for future therapeutic intervention.

[Cerebral amyloid angiopathy revealed or hypertension-related cerebral small vessel diseases: A clinical challenge]

Cerebral amyloid angiopathy (CAA) is a entity characterized by degenerative Amyloïd deposits in the walls of the meningeal and cortical vessels. It is considered as the second cause of primitives cerebral hemorrhage in elderly. The differential diagnosis between AAC and hypertension-related cerebral small vessel diseases is difficult and represent a true challenge for the clinician. We report two cases of cerebral small vessel diseases revealed by malignant hypertension.

Early Aβ reduction prevents progression of cerebral amyloid angiopathy

OBJECTIVE

Clinical trials targeting β-amyloid peptides (Aβ) for Alzheimer disease (AD) failed for arguable reasons that include selecting the wrong stages of AD pathophysiology or Aβ being the wrong target. Targeting Aβ to prevent cerebral amyloid angiopathy (CAA) has not been rigorously followed, although the causal role of Aβ for CAA and related hemorrhages is undisputed. CAA occurs with normal aging and to various degrees in AD, where its impact and treatment is confounded by the presence of parenchymal Aβ deposition.

METHODS

APPDutch mice develop CAA in the absence of parenchymal amyloid, mimicking hereditary cerebral hemorrhage with amyloidosis Dutch type (HCHWA-D). Mice were treated with a β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitor. We used 3-dimensional ultramicroscopy and immunoassays for visualizing CAA and assessing Aβ in cerebrospinal fluid (CSF) and brain.

RESULTS

CAA onset in mice was at 22 to 24 months, first in frontal leptomeningeal and superficial cortical vessels followed by vessels penetrating the cortical layers. CSF Aβ increased with aging followed by a decrease of both Aβ40 and Aβ42 upon CAA onset, supporting the idea that combined reduction of CSF Aβ40 and Aβ42 is a specific biomarker for vascular amyloid. BACE1 inhibitor treatment starting at CAA onset and continuing for 4 months revealed a 90% Aβ reduction in CSF and largely prevented CAA progression and associated pathologies.

INTERPRETATION

This is the first study showing that Aβ reduction at early disease time points largely prevents CAA in the absence of parenchymal amyloid. Our observation provides a preclinical basis for Aβ-reducing treatments in patients at risk of CAA and in presymptomatic HCHWA-D. ANN NEUROL 2019;86:561-571.

Beta-amyloid pathology in human brain microvessel extracts from the parietal cortex: relation with cerebral amyloid angiopathy and Alzheimer's disease

Several pieces of evidence suggest that blood-brain barrier (BBB) dysfunction is implicated in the pathophysiology of Alzheimer's disease (AD), exemplified by the frequent occurrence of cerebral amyloid angiopathy (CAA) and the defective clearance of Aβ peptides. However, the specific role of brain microvascular cells in these anomalies remains elusive. In this study, we validated by Western, ELISA and immunofluorescence analyses a procedure to generate microvasculature-enriched fractions from frozen samples of human cerebral cortex. We then investigated Aβ and proteins involved in its clearance or production in microvessel extracts generated from the parietal cortex of 60 volunteers in the Religious Orders Study. Volunteers were categorized as AD (n = 38) or controls (n = 22) based on the ABC scoring method presented in the revised guidelines for the neuropathological diagnosis of AD. Higher ELISA-determined concentrations of vascular Aβ40 and Aβ42 were found in persons with a neuropathological diagnosis of AD, in apoE4 carriers and in participants with advanced parenchymal CAA, compared to respective age-matched controls. Vascular levels of two proteins involved in Aβ clearance, ABCB1 and neprilysin, were lower in persons with AD and positively correlated with cognitive function, while being inversely correlated to vascular Aβ40. In contrast, BACE1, a protein necessary for Aβ production, was increased in individuals with AD and in apoE4 carriers, negatively correlated to cognitive function and positively correlated to Aβ40 in microvessel extracts. The present report indicates that concentrating microvessels from frozen human brain samples facilitates the quantitative biochemical analysis of cerebrovascular dysfunction in CNS disorders. Data generated overall show that microvessels extracted from individuals with parenchymal CAA-AD contained more Aβ and BACE1 and less ABCB1 and neprilysin, evidencing a pattern of dysfunction in brain microvascular cells contributing to CAA and AD pathology and symptoms.

Cerebrospinal fluid and blood biomarkers for neurodegenerative dementias: An update of the Consensus of the Task Force on Biological Markers in Psychiatry of the World Federation of Societies of Biological Psychiatry

In the 12 years since the publication of the first Consensus Paper of the WFSBP on biomarkers of neurodegenerative dementias, enormous advancement has taken place in the field, and the Task Force takes now the opportunity to extend and update the original paper. New concepts of Alzheimer's disease (AD) and the conceptual interactions between AD and dementia due to AD were developed, resulting in two sets for diagnostic/research criteria. Procedures for pre-analytical sample handling, biobanking, analyses and post-analytical interpretation of the results were intensively studied and optimised. A global quality control project was introduced to evaluate and monitor the inter-centre variability in measurements with the goal of harmonisation of results. Contexts of use and how to approach candidate biomarkers in biological specimens other than cerebrospinal fluid (CSF), e.g. blood, were precisely defined. Important development was achieved in neuroimaging techniques, including studies comparing amyloid-β positron emission tomography results to fluid-based modalities. Similarly, development in research laboratory technologies, such as ultra-sensitive methods, raises our hopes to further improve analytical and diagnostic accuracy of classic and novel candidate biomarkers. Synergistically, advancement in clinical trials of anti-dementia therapies energises and motivates the efforts to find and optimise the most reliable early diagnostic modalities. Finally, the first studies were published addressing the potential of cost-effectiveness of the biomarkers-based diagnosis of neurodegenerative disorders.

Core cerebrospinal fluid biomarker profile in cerebral amyloid angiopathy: A meta-analysis

OBJECTIVE

To perform a meta-analysis of 4 core CSF biomarkers (β-amyloid [Aβ]42, Aβ40, total tau [t-tau], and phosphorylated tau [p-tau]) to assess which of these are most altered in sporadic cerebral amyloid angiopathy (CAA).

METHODS

We systematically searched PubMed for eligible studies reporting data on CSF biomarkers reflecting amyloid precursor protein metabolism (Aβ42, Aβ40), neurodegeneration (t-tau), and tangle pathology (p-tau) in symptomatic sporadic CAA cohorts vs controls and patients with Alzheimer disease (AD). Biomarker performance was assessed in random-effects meta-analysis based on ratio of mean (RoM) biomarker concentrations: (1) in patients with CAA vs healthy controls and (2) in patients with CAA vs patients with AD. RoM >1 indicates higher biomarker concentration in patients with CAA vs comparison population and RoM <1 indicates higher concentration in comparison groups.

RESULTS

Three studies met inclusion criteria. These comprised 5 CAA patient cohorts (n = 59 patients) vs healthy controls (n = 94 cases) and AD cohorts (n = 158). Three core biomarkers differentiated CAA from controls: CSF Aβ42 (RoM 0.49, 95% confidence interval [CI] 0.38-0.64, p < 0.003), Aβ40 (RoM 0.70, 95% CI 0.63-0.78, p < 0.0001), and t-tau (RoM 1.54, 95% CI 1.15-2.07, p = 0.004); p-tau was marginal (RoM 1.24, 95% CI 0.99-1.54, p = 0.062). Differentiation between CAA and AD was strong for CSF Aβ40 (RoM 0.76, 95% CI 0.69-0.83, p < 0.0001), but not Aβ42 (RoM 1.00; 95% CI 0.81-1.23, p = 0.970). For t-tau and p-tau, average CSF ratios in patients with CAA vs patients with AD were 0.63 (95% CI 0.54-0.74, p < 0.0001) and 0.60 (95% CI 0.50-0.71, p < 0.0001), respectively.

CONCLUSION

Specific CSF patterns of Aβ42, Aβ40, t-tau, and p-tau might serve as molecular biomarkers of CAA, but analyses in larger CAA cohorts are needed.

Cerebrospinal Fluid Alzheimer's Disease Biomarkers in Isolated Supratentorial Cortical Superficial Siderosis

We evaluated cerebrospinal fluid amyloid-β 1-40 (Aβ40), amyloid-β 1-42 (Aβ42), total and phosphorylated-tau (t-tau and p-tau) in patients with symptomatic isolated cortical supratentorial superficial siderosis (SS), by prospectively recruiting ten patients with SS in the absence of pre-existing cognitive dysfunction, and comparing biomarkers with lobar hematoma cerebral amyloid angiopathy patients (LH-CAA, n = 13), Alzheimer's disease patients (AD, n = 42), and controls (n = 16). Compared to controls, SS patients showed statistically significant higher t-tau (p = 0.019) and lower Aβ42 (p = 0.0084). Compared to other groups, SS showed statistically significant lower t-tau, p-tau, and Aβ40 compared to AD (p = 0.0063, p = 0.0004, and p = 0022, respectively), and higher p-tau compared to LH-CAA (p = 0.012).

The increasing impact of cerebral amyloid angiopathy: essential new insights for clinical practice

Cerebral amyloid angiopathy (CAA) has never been more relevant. The last 5 years have seen a rapid increase in publications and research in the field, with the development of new biomarkers for the disease, thanks to advances in MRI, amyloid positron emission tomography and cerebrospinal fluid biomarker analysis. The inadvertent development of CAA-like pathology in patients treated with amyloid-beta immunotherapy for Alzheimer's disease has highlighted the importance of establishing how and why CAA develops; without this information, the use of these treatments may be unnecessarily restricted. Our understanding of the clinical and radiological spectrum of CAA has continued to evolve, and there are new insights into the independent impact that CAA has on cognition in the context of ageing and intracerebral haemorrhage, as well as in Alzheimer's and other dementias. While the association between CAA and lobar intracerebral haemorrhage (with its high recurrence risk) is now well recognised, a number of management dilemmas remain, particularly when considering the use of antithrombotics, anticoagulants and statins. The Boston criteria for CAA, in use in one form or another for the last 20 years, are now being reviewed to reflect these new wide-ranging clinical and radiological findings. This review aims to provide a 5-year update on these recent advances, as well as a look towards future directions for CAA research and clinical practice.

Background and distribution of lobar microbleeds in cognitive dysfunction

OBJECTIVES

Cerebral microbleeds (CMBs) are often observed in memory clinic patients. It has been generally accepted that deep CMBs (D-CMBs) result from hypertensive vasculopathy (HV), whereas strictly lobar CMBs (SL-CMBs) result from cerebral amyloid angiopathy (CAA) which frequently coexists with Alzheimer's disease (AD). Mixed CMBs (M-CMBs) have been partially attributed to HV and also partially attributed to CAA. The aim of this study was to elucidate the differences between SL-CMBs and M-CMBs in terms of clinical features and regional distribution.

MATERIALS

We examined 176 sequential patients in our memory clinic for clinical features and CMB location using susceptibility-weighted images obtained on a 3T-MRI. The number of lobar CMBs in SL-CMBs and M-CMBs was counted in each cerebral lobe and their regional density was adjusted according to the volume of each lobe.

RESULTS

Of the total 176 patients, 111 patients (63.1%) had CMBs. Within the patients who had CMBs, M-CMBs were found in 54 patients (48.6%), followed by SL-CMBs in 35 (31.5%) and D-CMBs in 19 (17.1%). The SL-CMB group showed a significantly higher prevalence of family history of dementia, whereas the M-CMB group showed an increasing trend toward hypertension and smoking. The prevalence of AD was significantly higher in the SL-CMBs group, whereas the prevalence of AD with cerebrovascular disease was higher in the M-CMBs group. The regional density of lobar CMBs was significantly higher in the occipital lobe in the M-CMB group, whereas the SL-CMB group showed higher regional density between regions an increasing tendency in the parietal and occipital lobe.

CONCLUSION

The between-group differences in clinical features and regional distribution indicate there to be an etiological relationship of SL-CMBs to AD and CAA, and M-CMBs to both HV and CAA.

Alzheimer's disease CSF biomarkers: clinical indications and rational use

This review focusses on the validation and standardization of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers, as well as on the current clinical indications and rational use of CSF biomarkers in daily clinical practice. The validated AD CSF biomarkers, Aβ1-42, T-tau, and P-tau181, have an added value in the (differential) diagnosis of AD and related disorders, including mixed pathologies, atypical presentations, and in case of ambiguous clinical dementia diagnosis. CSF biomarkers should not be routinely used in the diagnostic work-up of dementia and cannot be used to diagnose non-AD dementias. In cognitively healthy subjects, CSF biomarkers can only be applied for research purposes, e.g., to identify pre-clinical AD in the context of clinical trials with potentially disease-modifying drugs. Therefore, biomarker-based early diagnosis of AD offers great opportunities for preventive treatment development in the near future.

Cerebral microbleeds topography and cerebrospinal fluid biomarkers in cognitive impairment

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

β-Amyloid in CSF: Biomarker for preclinical cerebral amyloid angiopathy

OBJECTIVE

To investigate CSF biomarkers in presymptomatic and symptomatic mutation carriers with hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D), a model for sporadic cerebral amyloid angiopathy, and to determine the earliest deposited form of β-amyloid (Aβ).

METHODS

HCHWA-D mutation carriers and controls were enrolled in the cross-sectional EDAN (Early Diagnosis of Amyloid Angiopathy Network) study. The HCHWA-D group was divided into symptomatic carriers with a previous intracerebral hemorrhage and presymptomatic carriers. CSF concentrations of Aβ₄₀, Aβ₄₂, total tau, and phosphorylated tau₁₈₁ proteins were compared to those of controls of a similar age. Correlations between CSF biomarkers, MRI markers, and age were investigated with multivariate linear regression analyses.

RESULTS

We included 10 symptomatic patients with HCHWA-D (mean age 55 ± 6 years), 5 presymptomatic HCHWA-D carriers (mean age 36 ± 13 years), 31 controls <50 years old (mean age 31 ± 7 years), and 50 controls ≥50 years old (mean age 61 ± 8 years). After correction for age, CSF Aβ₄₀ and Aβ₄₂ were significantly decreased in symptomatic carriers vs controls (median Aβ₄₀ 1,386 vs 3,867 ng/L, p < 0.001; median Aβ₄₂ 289 vs 839 ng/L, p < 0.001) and in presymptomatic carriers vs controls (median Aβ₄₀ 3,501 vs 4,684 ng/L, p = 0.011; median Aβ₄₂ 581 vs 1,058 ng/L, p < 0.001). Among mutation carriers, decreasing CSF Aβ₄₀ was associated with higher lobar microbleed count (p = 0.010), increasing white matter hyperintensity volume (p = 0.008), and presence of cortical superficial siderosis (p = 0.02).

CONCLUSIONS

Decreased levels of CSF Aβ₄₀ and Aβ₄₂ occur before HCHWA-D mutation carriers develop clinical symptoms, implicating vascular deposition of both Aβ species as early steps in cerebral amyloid angiopathy pathogenesis. CSF Aβ₄₀ and Aβ₄₂ may serve as preclinical biomarkers of cerebral amyloid angiopathy pathology.

Cerebrospinal Fluid Alzheimer's Disease Biomarkers in Cerebral Amyloid Angiopathy-Related Inflammation

BACKGROUND

Decreased cerebrospinal fluid (CSF) amyloid-β 1-40 (Aβ40) and amyloid-β 1-42 (Aβ42) and increased total and phosphorylated tau (t-tau, p-tau) concentrations have been described in cerebral amyloid angiopathy (CAA).

OBJECTIVE

Our aim was to analyze these biomarkers in patients with CAA-related inflammation (CAA-I).

METHODS

We prospectively recruited nine patients with acute phase CAA-I fulfilling Chung criteria. CSF was analyzed for t-tau, p-tau, Aβ42, and Aβ40. Data were compared to controls (n = 14), patients with Alzheimer's disease (AD, n = 42), CAA (n = 10), and primary angiitis of the central nervous system (PACNS, n = 3).

RESULTS

For the CAA-I group, statistically significant differences were: lower Aβ42 (p = 0.00053) compared to the control group; lower t-tau (p = 0.018), p-tau (p <  0.001), and Aβ40 (p <  0.001) compared to AD; lower Aβ42 (p = 0.027) compared to CAA; lower Aβ42 (p = 0.012) compared to PACNS. Nearly significantly lower Aβ40 (p = 0.051) and higher t-tau (p = 0.051) were seen in CAA-I compared to controls.

CONCLUSION

CSF biomarkers profile similar to that of CAA was observed in CAA-I (with even lower levels of Aβ42 compared to CAA). Based on our findings, high p-tau seems more specific for AD, whereas low Aβ42 differentiates CAA-I from CAA, PACNS, and controls, and low Aβ40 differentiates CAA-I from AD.

Cerebrospinal fluid profiles with increasing number of cerebral microbleeds in a continuum of cognitive impairment

Cerebral microbleeds (CMBs) are hypothesised to have an important yet unknown role in the dementia disease pathology. In this study we analysed increasing number of CMBs and their independent associations with routine cerebrospinal fluid (CSF) biomarkers in a continuum of cognitive impairment. A total of 1039 patients undergoing dementia investigation were analysed and underwent lumbar puncture, and an MRI scan. CSF samples were analysed for amyloid β (Aβ) 42, total tau (T-tau), tau phosphorylated at threonine 18 (P-tau) and CSF/serum albumin ratios. Increasing number of CMBs were independently associated with low Aβ42 levels, in the whole cohort, Alzheimer's disease and mild cognitive impairment (p < 0.05). CSF/serum albumin ratios were high with multiple CMBs (p < 0.001), reflecting accompanying blood-brain barrier dysfunction. T-tau and P-tau levels were lower in Alzheimer's patients with multiple CMBs when compared to zero CMBs, but did not change in the rest of the cohort. White matter hyperintensities were associated with low Aβ42 in the whole cohort and Alzheimer's disease (p < 0.05). Aβ42 is the routine CSF-biomarker mainly associated with CMBs in cognitive impairment, and there is an accumulative effect with increasing number of CMBs.

Cerebral amyloid angiopathy-related atraumatic convexal subarachnoid hemorrhage: an ARIA before the tsunami

Atraumatic convexal subarachnoid hemorrhage (cSAH) in elderly patients is a rare entity that has been associated with cerebral amyloid angiopathy (CAA) and intracerebral hematomas (ICH). To characterize this entity and to study these associations, 22 patients over 60 with cSAH were included in a multicenter ambispective cohort study. Clinical data, magnetic resonance imaging (MRI) studies, APOE genotyping, and cerebrospinal fluid (CSF) biomarkers were evaluated. Results were compared with data from healthy controls (HC), non-cSAH CAA patients (CAAo), and Alzheimer disease patients. Convexal subarachnoid hemorrhage presented with transient sensory or motor symptoms. At follow-up (median 30.7 months), 5 patients had died, 6 survivors showed functional disability (modified Rankins Scale (mRS)>2), and 12 cognitive impairment. Four patients had prior ICH and six had an ICH during follow-up. CSF-Aß40 and Aß42 levels were lower in cSAH and CAAo compared with HC. Convexal subarachnoid hemorrhage presented an APOE-ɛ2 overrepresentation and CAAo had an APOE-ɛ4 overrepresentation. On MRI, all patients fulfilled CAA-modified Boston criteria and 9 showed cortical ischemia in the surrounding cortex or the vicinity of superficial siderosis. The neuropathologic study, available in one patient, showed severe CAA and advanced Alzheimer-type pathology. Convexal subarachnoid hemorrhage in the elderly is associated with cognitive impairment and lobar ICH occurrence. Our findings support the existence of an underlying CAA pathology.

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.

The overlap between vascular disease and Alzheimer's disease--lessons from pathology

Recent epidemiological and clinico-pathological data indicate considerable overlap between cerebrovascular disease (CVD) and Alzheimer's disease (AD) and suggest additive or synergistic effects of both pathologies on cognitive decline. The most frequent vascular pathologies in the aging brain and in AD are cerebral amyloid angiopathy and small vessel disease. Up to 84% of aged subjects show morphological substrates of CVD in addition to AD pathology. AD brains with minor CVD, similar to pure vascular dementia, show subcortical vascular lesions in about two-thirds, while in mixed type dementia (AD plus vascular dementia), multiple larger infarcts are more frequent. Small infarcts in patients with full-blown AD have no impact on cognitive decline but are overwhelmed by the severity of Alzheimer pathology, while in early stages of AD, cerebrovascular lesions may influence and promote cognitive impairment, lowering the threshold for clinically overt dementia. Further studies are warranted to elucidate the many hitherto unanswered questions regarding the overlap between CVD and AD as well as the impact of both CVD and AD pathologies on the development and progression of dementia.

Outcome markers for clinical trials in cerebral amyloid angiopathy

Efforts are underway for early-phase trials of candidate treatments for cerebral amyloid angiopathy, an untreatable cause of haemorrhagic stroke and vascular cognitive impairment. A major barrier to these trials is the absence of consensus on measurement of treatment effectiveness. A range of potential outcome markers for cerebral amyloid angiopathy can be measured against the ideal criteria of being clinically meaningful, closely representative of biological progression, efficient for small or short trials, reliably measurable, and cost effective. In practice, outcomes tend either to have high clinical salience but low statistical efficiency, and thus more applicability for late-phase studies, or greater statistical efficiency but more limited clinical meaning. The most statistically efficient markers might be those that are potentially reversible with treatment, although their clinical significance remains unproven. Many of the candidate outcomes for cerebral amyloid angiopathy trials are probably applicable also to other small-vessel brain diseases.

Interaction between sleep-disordered breathing and apolipoprotein E genotype on cerebrospinal fluid biomarkers for Alzheimer's disease in cognitively normal elderly individuals

Previous studies have suggested a link between sleep disordered breathing (SDB) and dementia risk. In the present study, we analyzed the relationship between SDB severity, cerebrospinal fluid (CSF) Alzheimer's disease-biomarkers, and the ApoE alleles. A total of 95 cognitively normal elderly participants were analyzed for SDB severity, CSF measures of phosphorylated-tau (p-tau), total-tau (t-tau), and amyloid beta 42 (Aβ-42), as well as ApoE allele status. In ApoE3+ subjects, significant differences were found between sleep groups for p-tau (F[df2] = 4.3, p = 0.017), and t-tau (F[df2] = 3.3, p = 0.043). Additionally, among ApoE3+ subjects, the apnea and/or hypopnea with 4% O2-desaturation index was positively correlated with p-tau (r = 0.30, p = 0.023), t-tau (r = 0.31, p = 0.021), and Aβ-42 (r = 0.31, p = 0.021). In ApoE2+ subjects, the apnea and/or hypopnea with 4% O2-desaturation index was correlated with lower levels of CSF Aβ-42 (r = -0.71, p = 0.004), similarly to ApoE4+ subjects where there was also a trend toward lower CSF Aβ-42 levels. Our observations suggest that there is an association between SDB and CSF Alzheimer's disease-biomarkers in cognitively normal elderly individuals. Existing therapies for SDB such as continuous positive airway pressure could delay the onset to mild cognitive impairment or dementia in normal elderly individuals.