The neuropathology of vascular and mixed dementia and vascular cognitive impairment

Blood-brain barrier dysfunction and reduced cerebrospinal fluid levels of soluble amyloid precursor protein-β in patients with subcortical small-vessel disease

Introduction

Subcortical small-vessel disease (SSVD) is the most common vascular cognitive disorder. However, because no disease-specific cerebrospinal fluid (CSF) biomarkers are available for SSVD, our aim was to identify such markers.

Methods

We included 170 healthy controls and patients from the Gothenburg Mild Cognitive Impairment (MCI) study clinically diagnosed with SSVD dementia, Alzheimer's disease (AD), or mixed AD/SSVD. We quantified CSF levels of amyloid-β (Aβ)x-38, Aβx-40, Aβx-42, as well as soluble amyloid precursor protein (sAPP)-α and sAPP-β.

Results

sAPP-β was lower in SSVD patients than in AD patients and controls. Receiver-operating characteristic (ROC) analyses showed that sAPP-β moderately separated SSVD from AD and controls. Moreover, the CSF/serum albumin ratio was elevated exclusively in SSVD and could moderately separate SSVD from the other groups in ROC analyses.

Discussion

SSVD has a biomarker profile that differs from that of AD and controls, and to some extent also from mixed AD/SSVD, suggesting that signs of blood-brain barrier (BBB) dysfunction and sAPP-β could be additional tools to diagnose SSVD.

Highlights

Patients with subcortical small-vessel disease (SSVD) exhibited reduced levels of sAPP-β and disturbances of the blood-brain barrier (BBB).This biochemical pattern is different from that of Alzheimer's disease (AD) and to some degree from that of mixed AD/SSVD.Our findings are speaking in favor of the concept that SSVD is a distinct vascular cognitive disorder (VCD) form.

Amyloid Angiopathy in Brain Hemorrhage: A Postmortem Neuropathological-Magnetic Resonance Imaging Study

Background: Risk factors for intracerebral hemorrhage (ICH) include hypertension and cerebral amyloid angiopathy (CAA). The objective of this study was to determine the autopsy prevalence of CAA and the potential overlap with other risk factors among patients who died from ICH and also the correlation of CAA with cerebral microbleeds. Methods: We analyzed 81 consecutive autopsy brains from patients with ICH. Staining for CAA detection was performed. We used an age- and sex-matched control group of routine brain autopsies of nonneurological patients to determine the frequencies of CAA and hypertension. Postmortem 3D T2-weighted gradient-echo magnetic resonance imaging (MRI) with a 1.5-T magnet was performed in 11 brains with ICH (5 with CAA and 6 without) and histological correlation was performed when microbleeds were detected. Results: Hypertension and CAA were found in 69.1 and 24.7% of cases respectively. Among patients with CAA, 65.0% also had hypertension. The prevalence of CAA was similar among non-hypertensive cases and controls (33.3 and 23.1%; p = 0.54), whereas a significant difference was found between hypertensive cases vs. controls (28.9% vs. 0; p = 0.01). MRI documented 48 microbleeds and all 5 brains with CAA had ≥1 microbleed, compared to 3/6 brains without CAA. Among 48 microbleeds on MRI, 45 corresponded histologically to microbleeds surrounding microvessels (23 <200 µm in diameter, 19 between 200 µm and 2 mm, 3 were hemosiderin granules). Conclusions: Both hypertension and CAA frequently coexist in patients with ICH. MRI-detected microbleeds, proven by histological analysis, were twice as common in patients with CAA as in those with hypertensive ICH.

Poststroke cognitive impairment and dementia: prevalence, diagnosis, and treatment

Three aspects of poststroke cognitive impairment and dementia are discussed in this review: prevalence; diagnosis; and treatment. The aim is to increase awareness of poststroke cognitive impairment in order to further stimulate strategies to recognize the condition and to prevent its progression. Approximately two-thirds of all middle-aged and elderly stroke patients develop cognitive impairment, and one in three develops dementia. The standard reference for diagnosis is a detailed neuropsychological examination. Short screening tests have been used for both clinical and research purposes, but their sensitivity is limited and there is no consensus as to which test is the most appropriate. The treatment of poststroke cognitive impairment and dementia is based on effective treatment of vascular risk factors, including lifestyle modification when needed.

Pathology and pathogenesis of vascular cognitive impairment-a critical update

Vascular cognitive impairment (VCI) [vascular cognitive disorder (VCD), vascular dementia] describes a continuum of cognitive disorders ranging from mild cognitive impairment (MCI) to dementia, in which vascular brain injury involving regions important for memory, cognition and behavior plays an important role. Clinical diagnostic criteria show moderate sensitivity (ca 50%) and variable specificity (range 64-98%). In Western clinical series, VaD is suggested in 8-10% of cognitively impaired elderly subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with means of 8 to 15% (in Japan 22-35%). Major types of sporadic VaD are multi-infarct encephalopathy, small vessel and strategic infarct type dementias, subcortical arteriosclerotic leukoencephalopathy (SAE) (Binswanger), multilacunar state, mixed cortico-subcortical type, granular cortical atrophy (rare), postischemic encephalopathy, and a mixture of cerebrovascular lesions (CVLs). They result from systemic, cardiac and local large or small vessel disease (SVD); their pathogenesis is multifactorial. Hereditary forms of VaD caused by gene mutations are rare. Cognitive decline is commonly associated with widespread small ischemic vascular lesions involving subcortical brain areas (basal ganglia and hemispheral white matter). The lesions affect neuronal networks involved in cognition, memory, and behavior (thalamo-cortical, striato-subfrontal, cortico-subcortical, limbic systems). CVLs often coexist with Alzheimer-type lesions and other pathologies; 25-80% of elderly demented show mixed pathologies. The lesion pattern of "pure" VaD differs from that in mixed dementia (AD + CVLs) suggesting different pathogenesis of both phenotypes. Minor CVLs, except for severe amyloid angiopathy, appear not essential for cognitive impairment in full-blown AD, while both mild AD-type pathology and SVD may interact synergistically in promoting dementia. However, in a large percentage of non-demented elderly individuals, both AD-related and vascular brain pathologies have been reported. Despite recent suggestions for staging and grading CVLs in specific brain areas, due to the high variability of CVLs associated with cognitive impairment, no validated neuropathological criteria are currently available for VaD and mixed dementia. Further clinico-pathological studies and harmonization of neuropathological procedures are needed to validate the diagnostic criteria for VaD and mixed dementia in order to clarify the impact of CVLs and other coexistent pathologies on cognitive impairment as a basis for further successful therapeutic options.