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Increasing evidence indicates that blood-brain barrier (BBB) impairment may play a role in the pathophysiology of cognitive decline and dementia. In vivo imaging studies are needed to quantify and localize the BBB defects during life, contemplating the circulatory properties. We reviewed the literature for imaging studies investigating BBB impairment in patients suffering from dementia. After selection, 11 imaging studies were included, of which 6 used contrast-enhanced magnetic resonance imaging (MRI), 2 used contrast-enhanced computed tomography (CT), and 3 positron emission tomography (PET). Primarily the MRI studies hint at a subtle increasing permeability of the BBB, particularly in patients already exhibiting cerebrovascular pathology. More elaborate studies are required to provide convincing evidence on BBB impairment in patients with various stages of dementia with and without obvious cerebrovascular pathology. In the future, dynamic contrast enhanced MRI techniques and transport specific imaging using PET may further detail the research on the molecular nature of BBB defects., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

To date, the exact pathogenesis of dementia is still unknown. The most frequently hypothesized initiating factor is an accumulation of the protein amyloid-β in the brain, which has been associated with dementia of the Alzheimer type. Another potentially important initiating factor is a disrupted blood-brain barrier. This can initiate cerebral microangiopathy, which has frequently been associated with vascular dementia. Although amyloid-β and blood-brain barrier dysfunction have both been associated with one particular type of dementia (Alzheimer's disease and vascular dementia, respectively), they co-exist in most demented patients. In fact, increasing evidence indicates that amyloid-β and blood-brain barrier disruption may interact and facilitate each other in their effect on neurodegeneration. The present systematic analysis describes the available evidence for a significant interplay between amyloid-β and blood-brain barrier function in dementia.

The standard for differentiating between dementia subtypes is currently based on neuropathological changes and follows traditional nosological classifications. However, the high incidence of comorbid neuropathologies complicates the differentiation between dementia diagnoses in the clinic. The aim of this study was to investigate the grades of agreement between clinical and neuropathological diagnoses in neurodegenerative disorders, to compare them with rates found in previous studies, and to propose implications for dementia diagnostics. Patients, who donated their brains to the Brain Bank of Navarre (Pamplona, Spain), had been diagnosed with a neurodegenerative disorder during life (clinical diagnosis) and postmortem (neuropathological diagnosis). We studied a sample of patients with a short average time interval between the last clinical assessment and death (4.6 months). Overall, there was a mean grade of agreement of 44.0% between the clinical diagnosis and the pure neuropathological diagnosis (i.e., without co-morbid neuropathological disorders). This grade of agreement differed between dementia subtypes: e.g., 85% for prion disease, 49% for Alzheimer's disease, and 0% for Lewy body dementia. Our data confirm that co-occurrence of multiple neuropathological disorders is very common in individuals with dementia, and that the underlying neuropathology often differs from the neuropathology implied by the clinical diagnosis. These findings support a multidimensional approach to diagnosing dementia, in which dementia syndromes are not categorized into diagnostic subtypes, but are seen as syndromes characterized by a combination of various neuropathological dimensions.

Cerebral small vessel disease (cSVD) and amyloid-β (Aβ) deposition often co-exist in (prodromal) dementia, and both types of pathology have been associated with neurodegeneration. We examined whether cSVD and Aβ have independent or interactive effects on hippocampal volume (HV) in a memory clinic population. We included 87 individuals with clinical diagnoses of Alzheimer's disease (AD) (n = 24), mild cognitive impairment (MCI) (n = 26), and subjective cognitive complaints (SCC) (n = 37). cSVD magnetic resonance imaging markers included white matter hyperintensity (WMH) volume, lacunar infarct presence, and microbleed presence. Aβ pathology was assessed as cerebrospinal fluid-derived Aβ1 - 42 levels and dichotomized into normal or abnormal, and HV was determined by manual volumetric measurements. A linear hierarchical regression approach was applied for the detection of additive or interaction effects between cSVD and Aβ on HV in the total participant group (n = 87) and in the non-demented group (including SCC and MCI individuals only, n = 63). The results revealed that abnormal Aβ and lacunar infarct presence were independently associated with lower HV in the non-demented individuals. Interestingly, Aβ and WMH pathology interacted in the non-demented individuals, such that WMH had a negative effect on HV in individuals with abnormal CSF Aβ42 levels, but not in individuals with normal CSF Aβ42 levels. These associations were not present when individuals with AD were included in the analyses. Our observations suggest that relatively early on in the disease process older individuals with abnormal Aβ levels are at an increased risk of accelerated disease progression when concomitant cSVD is present. [ABSTRACT FROM AUTHOR]

The neurovascular unit, which protects neuronal cells and supplies them with essential molecules, plays an important role in the pathophysiology of Alzheimer's Disease (AD). The aim of this study was to noninvasively investigate 2 linked functional elements of the neurovascular unit, blood–brain barrier (BBB) permeability and cerebral blood flow (CBF), in patients with early AD and healthy controls. Therefore, both dynamic contrast-enhanced magnetic resonance imaging and arterial spin labeling magnetic resonance imaging were applied to measure BBB permeability and CBF, respectively. The patients with early AD showed significantly lower CBF and local blood volume in the gray matter, compared with controls. In the patients, we also found that a reduction in CBF is correlated with an increase in leakage rate. This finding supports the hypothesis that neurovascular damage, and in particular impairment of the neurovascular unit constitutes the pathophysiological link between CBF reduction and BBB impairment in AD. [ABSTRACT FROM AUTHOR]