Post-mortem assessment in vascular dementia: advances and aspirations

The standardization of cerebrospinal fluid markers and neuropathological diagnoses brings to light the frequent complexity of concomitant pathology in Alzheimer's disease: The next challenge for biochemical markers?

During the last two decades, neuropathological examination of the brain has evolved both technically and scientifically. The increasing use of immunohistochemistry to detect protein aggregates paralleled a better understanding of neuroanatomical progression of protein deposition. As a consequence, an international effort was achieved to standardize hyperphosphorylated-Tau (phospho-TAU), ßAmyloid (Aß), alpha syncuclein (alpha-syn), phosphorylated transactive response DNA-binding protein 43 (phospho-TDP43) and vascular pathology detection. Meanwhile harmonized staging systems emerged in order to increase inter rater reproducibility. Therefore, a refined definition of Alzheimer's disease was recommended., a clearer picture of the neuropathological lesions diversity emerged secondarily to the systematic assessment of concomitant pathology highlighting finally a low rate of pure AD pathology. This brings new challenges to laboratory medicine in the field of cerebrospinal fluid (CSF) markers of Alzheimer's disease: how to further validate total Tau, phospho-TAU, Aß40 and Aß42 and new marker level cut-offs while autopsy rates are declining?

Emerging Biomarkers in Vascular Cognitive Impairment and Dementia: From Pathophysiological Pathways to Clinical Application

Vascular pathology is the second most common neuropathology of dementia after Alzheimer’s disease (AD), with small vessels disease (SVD) being considered the major cause of vascular cognitive impairment and dementia (VCID). This review aims to evaluate pathophysiological pathways underlying a diagnosis of VCID. Firstly, we will discuss the role of endothelial dysfunction, blood-brain barrier disruption and neuroinflammation in its pathogenesis. Then, we will analyse different biomarkers including the ones of inflammatory responses to central nervous system tissue injuries, of coagulation and thrombosis and of circulating microRNA. Evidences on peripheral biomarkers for VCID are still poor and large-scale, prospectively designed studies are needed to translate these findings into clinical practice, in order to set different combinations of biomarkers to use for differential diagnosis among types of dementia.

Role of cortical microbleeds in cognitive impairment: In vivo behavioral and imaging characterization of a novel murine model

Cerebral microbleeds (CMBs) could contribute to cognitive impairment in the general population and in patients with dementia. We designed a study to (i) develop a murine model of CMBs, (ii) assess whether CMBs affect cognition in this model and (iii) assess whether this model is sensitive to pharmacological modulation. Male C57Bl6/J mice were stereotactically administered collagenase to induce cortical lesion analysed by MRI at 24 h. CMB-mice were assessed at six weeks post-lesion for cognitive performances (Barnes maze and Touchscreen automated paired-associated learning (PAL) task) and for cerebral metabolism (in vivo PET/CT with fluorodeoxyglucose (FDG)). CMB-model sensitivity to pharmacological modulation was assessed by administering atorvastatin (5 mg/kg/day) over the follow-up period. CMB mice were compared to naïve littermates. Collagenase at 0.8 µU/µl appeared suitable to induce reproducible and reliable CMBs. At six weeks, a decline in learning, spatial and visuospatial memory was significantly observed in CMB-mice. Brain metabolism was impaired in all cortex, striatum and the ipsilateral dentate gyrus. A significant improvement in cognition performances was depicted under atorvastatin. In this novel murine model of CMBs, we validated that CMBs lowered cognitive performances and affected regional metabolism. We also proved that this CMB-model is sensitive to pharmacological modulation.

The Impact of Cerebral Amyloid Angiopathy in Various Neurodegenerative Dementia Syndromes: A Neuropathological Study

Purpose

The Boston criteria for cerebral amyloid angiopathy (CAA) have to be confirmed by postmortem examination. The present study investigates the incidence and the cerebrovascular impact of the severity of CAA in various neurodegenerative dementia diseases.

Material and Methods

208 patients underwent an autopsy. They consisted of 92 brains with Alzheimer's disease (AD), 46 with frontotemporal lobar degeneration (FTLD), 24 with progressive supranuclear palsy (PSP), 21 with Lewy body dementia (LBD), 5 with corticobasal degeneration (CBD), and 20 controls. In addition to the macroscopic examination, a whole coronal section of a cerebral hemisphere, at the level of the mamillary body, was taken for semiquantitative microscopic evaluation of the small cerebrovascular lesions.

Results

CAA is present in 2/3% of the AD brains of which half of them have a severe form, grade 3. Only the latter displays more cerebrovascular lesions. CAA is present in 45% of the LBD brains. Cortical microinfarcts are only more frequent in the CAA grade 3 group. In LBD additional AD pathology is present in 41% of the CAA grade 0, 83% in grade 1-2, and 100% in grade 3. In PSP only 21% had CAA grade 1-2. In FTLD, CBD, and normal controls no CAA pathology is observed.

Conclusions

The present study shows that CAA is most frequently associated to AD but that only the severe form displays more cerebrovascular lesions. LBD is the second most frequent disease associated to CAA with a clear correlation between the incidence of the associated AD features and the increasing severity of the CAA. In PSP only 21% display mild CAA features. PSP, tau-FTLD, and CBD are part of the Pick complex diseases, who are known to have a favourable vascular profile which can explain their low incidence of cerebrovascular lesions, in contrast to AD and LBD brains.

Defining Cognitive Reserve and Implications for Cognitive Aging

PURPOSE OF REVIEW

The aim of this review is to summarize current conceptual models of cognitive reserve (CR) and related concepts and to discuss evidence for these concepts within the context of aging and Alzheimer's disease.

RECENT FINDINGS

Evidence to date supports the notion that higher levels of CR, as measured by proxy variables reflective of lifetime experiences, are associated with better cognitive performance, and with a reduced risk of incident mild cognitive impairment/dementia. However, the impact of CR on longitudinal cognitive trajectories is unclear and may be influenced by a number of factors. Although there is promising evidence that some proxy measures of CR may influence structural brain measures, more research is needed. The protective effects of CR may provide an important mechanism for preserving cognitive function and cognitive well-being with age, in part because it can be enhanced throughout the lifespan. However, more research on the mechanisms by which CR is protective is needed.

[The role of arterial, venous blood and cerebrospinal fluid flow disturbances in forming cognitive impairment types in age-related cerebral microangiophathy]

BACKGROUND

Age-related cerebral microangiopathy (small vessel disease, SVD) is the main cause of vascular and mixed cognitive impairment (CI) with a complex neuropsychological profile.

AIM

To investigate the role of arterial and venous blood flow and cerebrospinal fluid (CSF) flow, as well as their interrelation, in the forming of CI types in patients with SVD.

MATERIAL AND METHODS

Fifty patients (31 f., mean age 61.2±6,2) with SVD (STRIVE, 2013), including 37 with mild CI and 13 with dementia, were examined. A type of CI was determined based on combination of standard deviations from normal results on memory and executive function tests: isolated dysexecutive (13) and predominantly dysexecutive (6), predominantly amnestic (12), mixed, equal impairment of EF and memory, (19). In the statistical analysis, groups of the isolated and predominantly dysexecutive types were merged according to the dominance of deviations in the EF into the dysexecutive type of CI (19). Phase contrast MRI (PhC-MRI) was used to assess characteristics of arterial and venous blood flow and CSF flow on different levels. Indexes of pulse and intracranial compliance and surface of the cerebral aqueduct were calculated.

RESULTS

Patients with all CI types had a CSF flow systolic peak delay at the cervical level. Mixed and dysexecutive CI types as compared with predominantly amnestic type and control were defined by blood flow reduction in the sinus rectus, and mixed type by the additional decrease in its pulse wave width, blood flow reduction in an internal jugular artery and maximal blood flow velocity in the inner carotid artery, the increase in the intracranial compliance index and surface of the cerebral aqueduct.

CONCLUSION

The neuropsychological CI type in SVD is defined by features of pathophysiological mechanisms conditioned on differences in blood flow and CSF flow impairment severity and formed hydrodynamic interaction between them. Differential features of CI types in SVD defined by PhC-MRI might become important predictive indicators of potential interaction between SVD and degeneration, improve understanding of risk factors, pathogenesis, prevention and treatment of age-related brain damage.

White matter in different regions evolves differently during progression to dementia

White matter hyperintensities (WMHs) are common in individuals with mild cognitive impairment (MCI) and Alzheimer's disease. Patients with MCI with high WMH volumes are known to have an increased chance of conversion to Alzheimer's disease compared with those without WMHs. In this article, we assess the differences between patients with MCI that remain stable (N = 413) and those that progress to dementia (N = 178) in terms of WMH volume (as a surrogate of amount of tissue damage) and T1-weighted (T1w) image hypointensity (as a surrogate of severity of tissue damage) in periventricular, deep, and juxtacortical brain regions. Together, lesion volume and T1w hypointensity are used as a surrogate of vascular disease burden. Our results show a significantly greater increase of all regional WMH volumes in the MCI population that converts to dementia (p < 0.001). T1w hypointensity for the juxtacortical WMHs was significantly lower in the converter group (p < 0.0001) and was not affected by age. Conversely, T1w hypointensity in other regions showed a significant decrease with age (p < 0.0001). Within the converters, Time2Conversion was associated with both WMH volume and T1w hypointensity (p < 0.0001), and conversion to dementia was significantly associated with decreased intensity (and not volume) of periventricular and juxtacortical WMHs (p < 0.001). These changes differ according to the WM region, suggesting that different mechanisms affect the juxtacortical area in comparison to deep and periventricular regions in the process of conversion to dementia.

Endothelial damage, vascular bagging and remodeling of the microvascular bed in human microangiopathy with deep white matter lesions

White matter lesions (WMLs) are a common manifestation of small vessel disease (SVD) in the elderly population. They are associated with an enhanced risk of developing gait abnormalities, poor executive function, dementia, and stroke with high mortality. Hypoperfusion and the resulting endothelial damage are thought to contribute to the development of WMLs. The focus of the present study was the analysis of the microvascular bed in SVD patients with deep WMLs (DWMLs) by using double- and triple-label immunohistochemistry and immunofluorescence. Simultaneous visualization of collagen IV (COLL4)-positive membranes and the endothelial glycocalyx in thick sections allowed us to identify endothelial recession in different types of string vessels, and two new forms of small vessel/capillary pathology, which we called vascular bagging and ghost string vessels. Vascular bags were pouches and tubes that were attached to vessel walls and were formed by multiple layers of COLL4-positive membranes. Vascular bagging was most severe in the DWMLs of cases with pure SVD (no additional vascular brain injury, VBI). Quantification of vascular bagging, string vessels, and the density/size of CD68-positive cells further showed widespread pathological changes in the frontoparietal and/or temporal white matter in SVD, including pure SVD and SVD with VBI, as well as a significant effect of the covariate age. Plasma protein leakage into vascular bags and the white matter parenchyma pointed to endothelial damage and basement membrane permeability. Hypertrophic IBA1-positive microglial cells and CD68-positive macrophages were found in white matter areas covered with networks of ghost vessels in SVD, suggesting phagocytosis of remnants of string vessels. However, the overall vessel density was not altered in our SVD cohort, which might result from continuous replacement of vessels. Our findings support the view that SVD is a progressive and generalized disease process, in which endothelial damage and vascular bagging drive remodeling of the microvasculature.

"Liquid Biopsy" of White Matter Hyperintensity in Functionally Normal Elders

Background and Objective: In the aging brain, increased blood-brain barrier (BBB) leakage and white matter hyperintensity (WMH) on MRI are frequently presumed secondary to cerebral small vessel disease (cSVD) or endotheliopathy. We investigate this association in vivo by quantifying protein cargo from endothelial-derived exosomes (EDE), and comparing levels between two groups of functionally normal elders with and without WMH. In addition, we study associations of EDE proteins with upstream and downstream factors, such as inflammation and neurodegenerative changes, respectively.

Methods: Twenty six neurologically normal older adults completed general health questionnaires, neuropsychological and physical examinations, and brain MRI. WMH was visually graded with modified Fazekas score of 2 or greater used to classify 11 subjects as cases, and 15 without WMH as controls. Plasma total exosomes were precipitated and EDEs enriched by sequential immuno-precipitations. In addition, we quantified three inflammatory cytokines from plasma and imaging variables on MRI. Group means were compared, the discriminant functions of biomarkers calculated, and the association of EDE biomarkers with plasma inflammatory markers, cognition, and imaging outcomes assessed via regression modeling.

Results: Plasma levels of EDE cargo proteins GLUT1, LAT1, P-GP, and NOSTRIN were significantly higher in subjects with WMH in comparison to those without. In contrast, EDE levels of the marker with low expression in brain (VCAM1) were equal between groups. The effect sizes for each of the brain-expressed cargo proteins (GLUT1, LAT1, and P-GP) were such that age-adjusted logistic regressions revealed areas under the curve (AUC) with range of 0.82–0.89, differentiating subjects with WMH from those without. VCAM1 poorly discriminated between groups (AUC:0.55). Higher levels of all brain-expressed EDE proteins were also associated with lower cognitive function, unrelated to burden of WMH. Levels of LAT1 and P-GP were significantly inversely associated with global gray matter volumes, and EDE GLUT1, LAT-1, and P-GP concentrations were significantly associated with systemic IL-6 levels.

Conclusion: In a case control study of clinically normal adults with and without WMH, concentrations of EDE proteins were significantly higher in subjects with WMH in comparison to controls. This work is a first step toward in vivo dissection of molecular changes in endothelia of functionally normal subjects with radiographic evidence of age-associated white matter disease.

APOE genotypes as a risk factor for age-dependent accumulation of cerebrovascular disease in older adults

INTRODUCTION

Apolipoprotein E (APOE) is a susceptibility gene for late-onset Alzheimer's disease neuropathology; less is known about the relationship between APOE and cerebrovascular disease (CVD) neuropathology.

METHODS

We investigated associations of APOE status with arteriolosclerosis, macroinfarcts and microinfarcts, and atherosclerosis in 1383 adults (65.9-108.2 years at death) with and without dementia. Excluding ε2/ε4 carriers, multivariable regressions for each CVD-related neuropathology compared ε4 and ε2 carriers to ε3/ε3 carriers adjusting for confounders including age and Alzheimer's neuropathology.

RESULTS

Three hundred forty-two individuals (24.7%; ∼87.7 years at death; 39.9% nondemented) were ε3/ε4 or ε4/ε4, and 180 (13.0%; ∼89.9 years at death; 66.6% nondemented) were ε2/ε3 or ε2/ε2. ε4 carriers had higher odds of macroinfarcts (odds ratio = 1.41, 95% confidence interval: 1.02-1.94, P = .03), whereas ε2 carriers had higher odds of moderate-to-severe arteriolosclerosis (odds ratio = 1.68, 95% confidence interval: 1.15-2.45, P = .006) compared to ε3/ε3 carriers. Age-stratified analyses suggested that these relationships were driven by ε4 carriers <90 years at death and ε2 carriers ≥90 years at death, respectively.

DISCUSSION

APOE differentially affects type and timing of CVD-related neuropathology.

Understanding the role of the perivascular space in cerebral small vessel disease

Small vessel diseases (SVDs) are a group of disorders that result from pathological alteration of the small blood vessels in the brain, including the small arteries, capillaries and veins. Of the 35-36 million people that are estimated to suffer from dementia worldwide, up to 65% have an SVD component. Furthermore, SVD causes 20-25% of strokes, worsens outcome after stroke and is a leading cause of disability, cognitive impairment and poor mobility. Yet the underlying cause(s) of SVD are not fully understood. Magnetic resonance imaging has confirmed enlarged perivascular spaces (PVS) as a hallmark feature of SVD. In healthy tissue, these spaces are proposed to form part of a complex brain fluid drainage system which supports interstitial fluid exchange and may also facilitate clearance of waste products from the brain. The pathophysiological signature of PVS and what this infers about their function and interaction with cerebral microcirculation, plus subsequent downstream effects on lesion development in the brain has not been established. Here we discuss the potential of enlarged PVS to be a unique biomarker for SVD and related brain disorders with a vascular component. We propose that widening of PVS suggests presence of peri-vascular cell debris and other waste products that form part of a vicious cycle involving impaired cerebrovascular reactivity, blood-brain barrier dysfunction, perivascular inflammation and ultimately impaired clearance of waste proteins from the interstitial fluid space, leading to accumulation of toxins, hypoxia, and tissue damage. Here, we outline current knowledge, questions and hypotheses regarding understanding the brain fluid dynamics underpinning dementia and stroke through the common denominator of SVD.

Study on epidemiology of cognitive dysfunction after stroke in the population over the age of 45 in Inner Mongolia

OBJECTIVE

To analyze the prevalence of different degrees vascular cognitive impairment (VCI) in stroke and the characteristics of demography distribution in Inner Mongolia. In order to provide reference data and theoretical guidance for the prevention and treatment of VCI after stroke in the area.

METHODS

Stratified multi-stage random sampling was used to extract six regions of Inner Mongolia as the first sampling cluster; and then the corresponding banners (counties) were selected randomly as the secondary sampling cluster; according to the number of patient required to investigation, the corresponding number of communities was randomly selected from the secondary sampling cluster. According to the diagnostic criteria of 'Guidelines for the diagnosis and treatment of vascular cognitive impairment' and National Institute of Neurological Disorders and Stroke convened an International Workshop with support from the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN), we screened all stroke patients aged 45 or older from each community, a total of 444 patients participated in the questionnaire and various scale assessments.

RESULTS

The prevalence of VCI, vascular cognitive impairment no dementia and vascular dementia was 80.41%, 34.46% and 45.95% respectively. The prevalence of VCI in stroke was significantly different in different nationality, age and education level (P < 0.05), and there was no significant difference in gender, occupation, marital status and family structure (P > 0.05).

CONCLUSION

The prevalence of VCI after stroke was higher in Inner Mongolia, and VCI had a relatively high morbidity in old age people and person with less education in Chinese Han population.

Incident Cerebral Microbleeds Detected by Susceptibility Weight-Imaging Help to Identify Patients with Mild Cognitive Impairment Progressing to Alzheimer's Disease

BACKGROUND

The relationship between cerebral microbleeds (CMB) and Alzheimer's disease (AD) has not yet been clearly determined, particularly with susceptibility weight-imaging (SWI).

OBJECTIVE

To evaluate the SWI sequence using 3T MRI for the detection of CMB, and its ability to differentiate elderly control subjects (CS), stable mild cognitive impairment patients (MCI-s), MCI patients progressing to AD (MCI-p), and AD patients.

METHODS

It was a prospective, monocentric, observational study that took place in Toulouse, France. Participants were 65 years and older, enrolled in three groups: CS, MCI, and AD. Based on the longitudinal analysis of cognitive decline, MCI subjects were retrospectively classified as MCI-s or MCI-p. Each patient had a 4-year follow-up with MRI at baseline (MRI#1) and during the fourth year (MRI#3). CMB were counted on native SWI images juxtaposed to minIP reformatted images.

RESULTS

150 patients were enrolled: 48 CS, 25 MCI-s, 18 MCI-p, 59 AD. At MRI#1 and at MRI#3, there was no significant difference in the prevalence of CMB between groups (p = 0.75 and p = 0.87). In the MCI-p + AD group, significantly more subjects had≥4 incident CMB compared to the CS + MCI-s group (p = 0.016). In the MCI-p + AD group, the prevalence of patients with >4 CMB was significantly higher at MRI#3 than at MRI#1 (p = 0.008).

CONCLUSION

Using SWI, AD and MCI-p patients had developed significantly more new CMB than CS and MCI-s patients during the follow-up. Incident CMB might be suggested as a potential imaging marker of AD progression.

Transactive DNA Binding Protein 43 Rather Than Other Misfolded Proteins in the Brain is Associated with Islet Amyloid Polypeptide in Pancreas in Aged Subjects with Diabetes Mellitus

A link between diabetes mellitus (DM) related islet amyloid polypeptide (IAPP) and Alzheimer’s disease (AD) related amyloid-β (Aβ) has been suggested in epidemiological and clinical studies. In 2017, proof for existing interaction between type 2 DM and AD on a molecular level was provided based on research carried out in experimental animal models. We assessed aging-related neurodegenerative lesions, i.e., misfolded proteins, associated with dementia such as hyperphosphorylated τ (HPτ), Aβ, α-synuclein (αS), and phosphorylated transactive DNA binding protein 43 (pTDP43) seen in the brain and IAPP seen in the pancreas in subjects with and without DM applying immunohistochemical techniques. HPτ in the brain and IAPP in the pancreas were observed in most subjects. The prevalence and the extent of all misfolded proteins increased with age but this increase was not influenced by DM. Interestingly the extent of misfolded proteins in the brain was higher in non-diabetics when compared with diabetics in demented. A significant correlation was observed between HPτ, Aβ, αS, and pTDP43, whereas IAPP showed no association with HPτ, Aβ, and αS. In subjects with DM, the extent of pTDP43 in brain correlated with the extent of IAPP in pancreas. Thus, there is no evidence of a link between AD-related pathology and DM in humans, whereas an association was found between pTDP43 and IAPP in DM. TDP43 is ubiquitously expressed in all organs but whether TDP43 is phosphorylated in other organs in DM or whether the phosphorylation of TDP43 is influenced by glucose metabolism is yet unknown.

Targeting Early Dementia: Using Lipid Cubic Phase Nanocarriers to Cross the Blood⁻Brain Barrier

Over the past decades, a frequent co-morbidity of cerebrovascular pathology and Alzheimer's disease has been observed. Numerous published studies indicate that the preservation of a healthy cerebrovascular endothelium can be an important therapeutic target. By incorporating the appropriate drug(s) into biomimetic (lipid cubic phase) nanocarriers, one obtains a multitasking combination therapeutic, which targets certain cell surface scavenger receptors, mainly class B type I (i.e., SR-BI), and crosses the blood⁻brain barrier. This targeting allows for various cell types related to Alzheimer's to be simultaneously searched out for localized drug treatment in vivo.

Neuropathology correlates of cognitive assessments

BACKGROUND

Alzheimer's disease and other dementias are the fourth largest contributors to neurological disability and the second largest contributor to deaths from neurological disease. Described in the 1980s as 'the silent epidemic' these disorders principally, though not exclusively, affect persons 80 years or older, and in developed countries, this 'old old' population continues to grow. Definitive diagnosis of the underlying cause of the neurodegenerative disease relies on neuropathological evaluation.` AIMS: Herein, we review the sampling methods, analysis and interpretation of both pathological and immunocytochemical techniques in the diagnostic assessment of neurodegenerative disease.

FINDINGS

Neurodegenerative disorders are characterised by accumulation of pathologically altered protein in the human brain, and in some cases, in the peripheral tissues. Whilst it is suggested that a comprehensive review of the patient's clinical history, cognition and behaviour, together with a full clinical examination and radiological analysis, should lead to a high degree of confidence in the clinical diagnosis, the view persists that underlying pathology can only be predicted on clinical grounds especially in Alzheimer's disease, vascular brain injury and diffuse Lewy body disease with only limited accuracy.

CONCLUSIONS

Neuropathological assessment of well characterised clinical cases provides accurate data on the prevalence of neurodegenerative diseases. This will aid future biomarker, neuroimaging studies and clinical trials focussed on population based cohorts.

Nanotherapy for Alzheimer's disease and vascular dementia: Targeting senile endothelium

Due to the complexity of Alzheimer's disease, multiple cellular types need to be targeted simultaneously in order for a given therapy to demonstrate any major effectiveness. Ultrasound-sensitive coated microbubbles (in a targeted lipid nanoemulsion) are available. Versatile small molecule drug(s) targeting multiple pathways of Alzheimer's disease pathogenesis are known. By incorporating such drug(s) into the targeted "lipid-coated microbubble" [LCM]/"nanoparticle-derived" [ND] (or LCM/ND) nanoemulsion type, one obtains a multitasking combination therapeutic for translational medicine. This multitasking therapeutic targets cell-surface scavenger receptors (mainly class B type I), or SR-BI, making possible for various Alzheimer's-related cell types to be simultaneously searched out for localized drug treatment in vivo. Besides targeting cell-surface SR-BI, the proposed LCM/ND-nanoemulsion combination therapeutic(s) include a characteristic lipid-coated microbubble [LCM] subpopulation (i.e., a stable LCM suspension); such film-stabilized microbubbles are well known to substantially reduce the acoustic power levels needed for accomplishing temporary noninvasive (transcranial) ultrasound treatment, or sonoporation, if additionally desired for the Alzheimer's patient.

Alzheimer’s Disease, Brain Injury, and C.N.S. Nanotherapy in Humans: Sonoporation Augmenting Drug Targeting

Owing to the complexity of neurodegenerative diseases, multiple cellular types need to be targeted simultaneously in order for a given therapy to demonstrate any major effectiveness. Ultrasound-sensitive coated microbubbles (in a targeted nanoemulsion) are available. Versatile small-molecule drug(s) targeting multiple pathways of Alzheimer’s disease pathogenesis are known. By incorporating such drug(s) into the targeted lipid-coated microbubble/nanoparticle-derived (LCM/ND) lipid nanoemulsion type, one obtains a multitasking combination therapeutic for translational medicine. This multitasking therapeutic targets cell-surface scavenger receptors (mainly scavenger receptor class B type I (SR-BI)), making it possible for various Alzheimer’s-related cell types to be simultaneously sought for localized drug treatment in vivo. Besides targeting cell-surface SR-BI, the proposed LCM/ND-nanoemulsion combination therapeutic(s) include a characteristic lipid-coated microbubble (LCM) subpopulation (i.e., a stable LCM suspension); such LCM substantially reduce the acoustic power levels needed for accomplishing temporary noninvasive (transcranial) ultrasound treatment, or sonoporation, if additionally desired for the Alzheimer’s patient.

Parietal white matter lesions in Alzheimer's disease are associated with cortical neurodegenerative pathology, but not with small vessel disease

Cerebral white matter lesions (WML) encompass axonal loss and demyelination, and the pathogenesis is assumed to be small vessel disease (SVD)-related ischemia. However, WML may also result from the activation of Wallerian degeneration as a consequence of cortical Alzheimer's disease (AD) pathology, i.e. hyperphosphorylated tau (HPτ) and amyloid-beta (Aβ) deposition. WML seen in AD have a posterior predominance compared to non-demented individuals but it is unclear whether the pathological and molecular signatures of WML differ between these two groups. We investigated differences in the composition and aetiology of parietal WML from AD and non-demented controls. Parietal WML tissue from 55 human post-mortem brains (AD, n = 27; non-demented controls, n = 28) were quantitatively assessed for axonal loss and demyelination, as well as for cortical HPτ and Aβ burden and SVD. Biochemical assessment included Wallerian degeneration protease calpain and the myelin-associated glycoprotein (MAG) to proteolipid protein (PLP) ratio (MAG:PLP) as a measure of hypoperfusion. WML severity was associated with both axonal loss and demyelination in AD, but only with demyelination in controls. Calpain was significantly increased in WML tissue in AD, whereas MAG:PLP was significantly reduced in controls. Calpain levels were associated with increasing amounts of cortical AD-pathology but not SVD. We conclude that parietal WML seen in AD differ in their pathological composition and aetiology compared to WML seen in aged controls: WML seen in AD may be associated with Wallerian degeneration that is triggered by cortical AD-pathology, whereas WML in aged controls are due to ischaemia. Hence, parietal WML as seen on MRI should not invariably be interpreted as a surrogate biomarker for SVD as they may be indicative of cortical AD-pathology, and therefore, AD should also be considered as the main underlying cause for cognitive impairment in cases with parietal WML.

Emerging concepts in sporadic cerebral amyloid angiopathy

Sporadic cerebral amyloid angiopathy is a common, well-defined small vessel disease and a largely untreatable cause of intracerebral haemorrhage and contributor to age-related cognitive decline. The term 'cerebral amyloid angiopathy' now encompasses not only a specific cerebrovascular pathological finding, but also different clinical syndromes (both acute and progressive), brain parenchymal lesions seen on neuroimaging and a set of diagnostic criteria-the Boston criteria, which have resulted in increasingly detected disease during life. Over the past few years, it has become clear that, at the pathophysiological level, cerebral amyloid angiopathy appears to be in part a protein elimination failure angiopathy and that this dysfunction is a feed-forward process, which potentially leads to worsening vascular amyloid-β accumulation, activation of vascular injury pathways and impaired vascular physiology. From a clinical standpoint, cerebral amyloid angiopathy is characterized by individual focal lesions (microbleeds, cortical superficial siderosis, microinfarcts) and large-scale alterations (white matter hyperintensities, structural connectivity, cortical thickness), both cortical and subcortical. This review provides an interdisciplinary critical outlook on various emerging and changing concepts in the field, illustrating mechanisms associated with amyloid cerebrovascular pathology and neurological dysfunction.

Collagenosis of the Deep Medullary Veins: An Underrecognized Pathologic Correlate of White Matter Hyperintensities and Periventricular Infarction?

White matter hyperintensities (WMH) are prevalent. Although arteriolar disease has been implicated in their pathogenesis, venous pathology warrants consideration. We investigated relationships of WMH with histologic venous, arteriolar and white matter abnormalities and correlated findings with premortem neuroimaging. Three regions of periventricular white matter were sampled from archived autopsy brains of 24 pathologically confirmed Alzheimer disease (AD) and 18 age-matched nonAD patients. Using trichrome staining, venous collagenosis (VC) of periventricular veins (<150 µm in diameter) was scored for severity of wall thickening and occlusion; percent stenosis by collagenosis of large caliber (>200 µm) veins (laVS) was measured. Correlations were made between WMH in premortem neuroimaging and vascular and white matter pathology. We found greater VC (U(114) = 2092.5, p = 0.005 and U(114) = 2121.5, p = 0.002 for small and medium caliber veins, respectively) and greater laVS (t(110) = 3.46, p = 0.001) in patients with higher WMH scores; WMH scores correlated with VC (rs(114) = 0.27, p = 0.004) and laVS (rs(110) = 0.38, p < 0.001). By multiple linear regression analysis, the strongest predictor of WMH score was laVS (β = 0.338, p < 0.0001). VC was frequent in patients with periventricular infarcts identified on imaging. We conclude that periventricular VC is associated with WMH in both AD and nonAD patients and the potential roles of VC in WMH pathogenesis merit further study.

A clinicopathological approach to the diagnosis of dementia

The most definitive classification systems for dementia are based on the underlying pathology which, in turn, is categorized largely according to the observed accumulation of abnormal protein aggregates in neurons and glia. These aggregates perturb molecular processes, cellular functions and, ultimately, cell survival, with ensuing disruption of large-scale neural networks subserving cognitive, behavioural and sensorimotor functions. The functional domains affected and the evolution of deficits in these domains over time serve as footprints that the clinician can trace back with various levels of certainty to the underlying neuropathology. The process of phenotyping and syndromic classification has substantially improved over decades of careful clinicopathological correlation, and through the discovery of in vivo biomarkers of disease. Here, we present an overview of the salient features of the most common dementia subtypes - Alzheimer disease, vascular dementia, frontotemporal dementia and related syndromes, Lewy body dementias, and prion diseases - with an emphasis on neuropathology, relevant epidemiology, risk factors, and signature signs and symptoms.

CSF/serum albumin ratio in dementias: a cross-sectional study on 1861 patients

A connection between dementias and blood-brain barrier (BBB) dysfunction has been suggested, but previous studies have yielded conflicting results. We examined cerebrospinal fluid (CSF)/serum albumin ratio in a large cohort of patients diagnosed with Alzheimer's disease (AD, early onset [EAD, n = 130], late onset AD [LAD, n = 666]), vascular dementia (VaD, n = 255), mixed AD and VaD (MIX, n = 362), Lewy body dementia (DLB, n = 50), frontotemporal dementia (FTD, n = 56), Parkinson's disease dementia (PDD, n = 23), other dementias (other, n = 48), and dementia not otherwise specified (NOS, n = 271). We compared CSF/serum albumin ratio to 2 healthy control groups (n = 292, n = 20), between dementia diagnoses, and tested biomarker associations. Patients in DLB, LAD, VaD, MIX, other, and NOS groups had higher CSF/serum albumin ratio than controls. CSF/serum albumin ratio correlated with CSF neurofilament light in LAD, MIX, VaD, and other groups but not with AD biomarkers. Our data show that BBB leakage is common in dementias. The lack of association between CSF/serum albumin ratio and AD biomarkers suggests that BBB dysfunction is not inherent to AD but might represent concomitant cerebrovascular pathology.

Vascular Contributions to Cognitive Impairment in Late Life

Cerebrovascular disease (CVD) is the second leading cause of cognitive impairment in late life. Structural neuroimaging offers the most sensitive and specific biomarkers for hemorrhages and infarcts, but there are significant limitations in its ability to detect microvascular disease, microinfarcts, dynamic changes in the blood-brain barrier, and preclinical cerebrovascular disease. Autopsy studies disclose the common co-occurrence of vascular and neurodegenerative conditions, suggesting that in late life, a multifactorial approach to cognitive impairment may be more appropriate than traditional dichotomous classifications. Management of vascular risk factors remains a proven and practical approach to reducing acute and progressive cognitive impairment and dementia.

Neuropathological diagnoses and clinical correlates in older adults in Brazil: A cross-sectional study

BACKGROUND

Clinicopathological studies are important in determining the brain lesions underlying dementia. Although almost 60% of individuals with dementia live in developing countries, few clinicopathological studies focus on these individuals. We investigated the frequency of neurodegenerative and vascular-related neuropathological lesions in 1,092 Brazilian admixed older adults, their correlation with cognitive and neuropsychiatric symptoms, and the accuracy of dementia subtype diagnosis.

METHODS AND FINDINGS

In this cross-sectional study, we describe clinical and neuropathological variables related to cognitive impairment in 1,092 participants (mean age = 74 y, 49% male, 69% white, and mean education = 4 y). Cognitive function was investigated using the Clinical Dementia Rating (CDR) and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE); neuropsychiatric symptoms were evaluated using the Neuropsychiatric Inventory (NPI). Associations between neuropathological lesions and cognitive impairment were investigated using ordinal logistic regression. We developed a neuropathological comorbidity (NPC) score and compared it to CDR, IQCODE, and NPI scores. We also described and compared the frequency of neuropathological diagnosis to clinical diagnosis of dementia subtype. Forty-four percent of the sample met criteria for neuropathological diagnosis. Among these participants, 50% had neuropathological diagnoses of Alzheimer disease (AD), and 35% of vascular dementia (VaD). Neurofibrillary tangles (NFTs), hippocampal sclerosis, lacunar infarcts, hyaline atherosclerosis, siderocalcinosis, and Lewy body disease were independently associated with cognitive impairment. Higher NPC scores were associated with worse scores in the CDR sum of boxes (β = 1.33, 95% CI 1.20-1.46), IQCODE (β = 0.14, 95% CI 0.13-0.16), and NPI (β = 1.74, 95% CI = 1.33-2.16). Compared to neuropathological diagnoses, clinical diagnosis had high sensitivity to AD and high specificity to dementia with Lewy body/Parkinson dementia. The major limitation of our study is the lack of clinical follow-up of participants during life.

CONCLUSIONS

NFT deposition, vascular lesions, and high NPC scorewere associated with cognitive impairment in a unique Brazilian sample with low education. Our results confirm the high prevalence of neuropathological diagnosis in older adults and the mismatch between clinical and neuropathological diagnoses.

White Matter Damage in the Cholinergic System Contributes to Cognitive Impairment in Subcortical Vascular Cognitive Impairment, No Dementia

Cholinergic deficiency has been implicated in the pathogenesis of vascular cognitive impairment (VCI), but the extent of involvement and underlying mechanism remain unclear. In this study, targeting the early stage of VCI, we determined regional atrophy within the basal forebrain and deficiency in cholinergic pathways in 25 patients with vascular cognitive impairment no dementia (VCIND) compared to 24 healthy elderly subjects. By applying stereotaxic cytoarchitectonic maps of the nucleus basalis of Meynert (NbM), no significant atrophy was identified in VCIND. Using probabilistic tractography analysis, our study tracked the two major white matter tracks which map to cholinergic pathways. We identified significantly lower fractional anisotropy (FA) in VCIND. Mediation analysis demonstrated that FA in the tracked pathways could fully account for the executive dysfunction, and partly mediate the memory and global cognition impairment. Our study suggests that the fibers mapped to the cholinergic pathways, but not the NbM, are significantly impaired in VCIND. MRI-based in vivo tracking of cholinergic pathways together with NbM measurement may become a valuable in vivo marker for evaluating the cholinergic system in cognitive disorders.

Multiple neuropathologies and dementia in the aging brain: a key role for cerebrovascular disease?

This short perspective discusses the conclusions of a Research Roundtable meeting held in October in 2014 within the overall theme of understanding the role of additional/comorbid pathologies in the aging brain and their potential interaction with clinical Alzheimer's disease and other dementia phenotypes. We specifically examine the key role of for cerebrovascular small vessel disease in this context and highlight future directions.

Rust on the Brain from Microbleeds and Its Relevance to Alzheimer Studies: Invited Commentary on Cacciottolo Neurobiology of Aging, 2016

Cerebral microbleeds (MB) and small vessel disease (SVD) with congophilic arterial angiopathy (CAA) are increasingly recognized as a variable factor in AD cognitive impairments. This commentary on our recent report on sex-ApoE interactions in MBs published this February, briefly explores three aspects of MBs that could not be fully discussed therein: I, A possible gap between the prevalence of MBs as detected by MRI and post mortem analysis; II, The role of hemoglobin-degradation products in amyloid-attributed neurodegenerative changes; and III, Possible assessment of MB by cerebrospinal fluid (CSF) assays for iron-related markers to better screen patient subgroups for AD interventions.

What is new in vascular dementia?

Any damage to the brain may affect cognition. However, although the effects of vascular changes have been known for years, involvement of such changes is becoming increasingly better recognized. In particular the effects of comorbid vascular disease to primary neurodegenerative processes adds to the complexity of the issue. An attempt to clarify the problems needed specific attention to different points, which led to Consensus Reports on several of them.