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Background: The underlying cause of cognitive decline in individuals who are positive for biomarkers of neurodegeneration (N) but negative for biomarkers of amyloid-beta (A), designated as Suspected non-Alzheimer's pathophysiology (SNAP), remains unclear. We evaluate whether cerebrovascular disease (CeVD) is more prevalent in those with SNAP compared to A−N− and A+N+ individuals and whether CeVD is associated with cognitive decline over time in SNAP patients. Methods: A total of 216 individuals from a prospective memory clinic cohort (mean [SD] age, 72.7 [7.3] years, 100 women [56.5%]) were included and were diagnosed as no cognitive impairment (NCI), cognitive impairment no dementia (CIND), Alzheimer's dementia (AD) or vascular dementia (VaD). All individuals underwent clinical evaluation and neuropsychological assessment annually for up to 5 years. Carbon 11-labeled Pittsburgh Compound B ([11C]-PiB) or [18F]-flutafuranol-positron emission spectrometry imaging was performed to ascertain amyloid-beta status. Magnetic resonance imaging was performed to assess neurodegeneration as measured by medial temporal atrophy ≥2, as well as significant CeVD (sCeVD) burden, defined by cortical infarct count ≥1, Fazekas score ≥2, lacune count ≥2 or cerebral microbleed count ≥2. Results: Of the 216 individuals, 50 (23.1%) A−N+ were (SNAP), 93 (43.1%) A−N−, 36 (16.7%) A+N− and 37 (17.1%) A+N+. A+N+ individuals were significantly older, while A+N+ and SNAP individuals were more likely to have dementia. The SNAP group had a higher prevalence of sCeVD (90.0%) compared to A−N−. Moreover, SNAP individuals with sCeVD had significantly steeper decline in global cognition compared to A−N− over 5 years (p = 0.042). Conclusions: These findings suggest that CeVD is a contributing factor to cognitive decline in SNAP. Therefore, SNAP individuals should be carefully assessed and treated for CeVD.

The prevalence of cerebrovascular disease increases with age, placing the elderly at a greater lifetime risk for dementia. Vascular cognitive impairment (VCI) encompasses a spectrum of cognitive deficits from mild cognitive impairment to dementia. VCI and its most severe form, vascular dementia (VaD), is becoming a major public health concern worldwide. As growing efforts are being taken to understand VCI and VaD in animal models and humans, the pathogenesis of the disease is being actively explored. It is postulated that chronic cerebral hypoperfusion (CCH) is a major cause of VCI. CCH activates a molecular and cellular injury cascade that leads to breakdown of the blood brain barrier (BBB) and neurodegeneration. The BBB tightly regulates the movement of substances between the blood and the brain, thereby regulating the microenvironment within the brain parenchyma. Here we illustrate how BBB damage is causal in the pathogenesis of VCI through the increased activation of pathways related to excitotoxicity, oxidative stress, inflammation and matrix metalloproteinases that lead to downstream perivascular damage, leukocyte infiltration and white matter changes in the brain. Thus, CCH-induced BBB damage may initiate and contribute to a vicious cycle, resulting in progressive neuropathological changes of VCI in the brain. This review outlines the molecular and cellular mechanisms that govern BBB breakdown during CCH and highlights the clinical evidence in identifying at-risk VCI patients.

Alzheimer’s disease (AD) is characterized by the accumulation of amyloid-β plaques and Tau tangles in brain tissues. Recent studies indicate that aberrant splicing and increased level of intron retention is linked to AD pathogenesis. Bioinformatic analysis revealed increased retention of intron 11 at the Tau gene in AD female dorsal lateral prefrontal cortex as compared to healthy controls, an observation validated by quantitative polymerase chain reaction using different brain tissues. Retention of intron 11 introduces a premature stop codon, resulting in the production of truncated Tau11i protein. Probing with customized antibodies designed against amino acids encoded by intron 11 showed that Tau11i protein is more enriched in AD hippocampus, amygdala, parietal, temporal, and frontal lobe than in healthy controls. This indicates that Tau messenger RNA with the retained intron is translated in vivo instead of being subjected to nonsense-mediated decay. Compared to full-length Tau441 isoform, ectopically expressed Tau11i forms higher molecular weight species, is enriched in Sarkosyl-insoluble fraction, and exhibits greater protein stability in cycloheximide assay. Stably expressed Tau11i also shows weaker colocalization with α-tubulin of microtubule network in human mature cortical neurons as compared to Tau441. Endogenous Tau11i is enriched in Sarkosyl-insoluble fraction in AD hippocampus and forms aggregates that colocalize weakly with Tau4R fibril-like structure in AD temporal lobe. The elevated level of Tau11i protein in AD brain tissues tested, coupled with biochemical properties resembling pathological Tau species suggest that retention of intron 11 of Tau gene might be an early biomarker of AD pathology.

BACKGROUND: There is no simple model to screen for Alzheimer's disease, partly because the diagnosis of Alzheimer's disease itself is complex-typically involving expensive and sometimes invasive tests not commonly available outside highly specialised clinical settings. We aimed to develop a deep learning algorithm that could use retinal photographs alone, which is the most common method of non-invasive imaging the retina to detect Alzheimer's disease-dementia.METHODS: In this retrospective, multicentre case-control study, we trained, validated, and tested a deep learning algorithm to detect Alzheimer's disease-dementia from retinal photographs using retrospectively collected data from 11 studies that recruited patients with Alzheimer's disease-dementia and people without disease from different countries. Our main aim was to develop a bilateral model to detect Alzheimer's disease-dementia from retinal photographs alone. We designed and internally validated the bilateral deep learning model using retinal photographs from six studies. We used the EfficientNet-b2 network as the backbone of the model to extract features from the images. Integrated features from four retinal photographs (optic nerve head-centred and macula-centred fields from both eyes) for each individual were used to develop supervised deep learning models and equip the network with unsupervised domain adaptation technique, to address dataset discrepancy between the different studies. We tested the trained model using five other studies, three of which used PET as a biomarker of significant amyloid β burden (testing the deep learning model between amyloid β positive vs amyloid β negative).FINDINGS: 12 949 retinal photographs from 648 patients with Alzheimer's disease and 3240 people without the disease were used to train, validate, and test the deep learning model. In the internal validation dataset, the deep learning model had 83·6% (SD 2·5) accuracy, 93·2% (SD 2·2) sensitivity, 82·0% (SD 3·1) specificity, and an area under the receiver operating characteristic curve (AUROC) of 0·93 (0·01) for detecting Alzheimer's disease-dementia. In the testing datasets, the bilateral deep learning model had accuracies ranging from 79·6% (SD 15·5) to 92·1% (11·4) and AUROCs ranging from 0·73 (SD 0·24) to 0·91 (0·10). In the datasets with data on PET, the model was able to differentiate between participants who were amyloid β positive and those who were amyloid β negative: accuracies ranged from 80·6 (SD 13·4%) to 89·3 (13·7%) and AUROC ranged from 0·68 (SD 0·24) to 0·86 (0·16). In subgroup analyses, the discriminative performance of the model was improved in patients with eye disease (accuracy 89·6% [SD 12·5%]) versus those without eye disease (71·7% [11·6%]) and patients with diabetes (81·9% [SD 20·3%]) versus those without the disease (72·4% [11·7%]).INTERPRETATION: A retinal photograph-based deep learning algorithm can detect Alzheimer's disease with good accuracy, showing its potential for screening Alzheimer's disease in a community setting.

There is an increasing prevalence of Vascular Cognitive Impairment (VCI) worldwide, and several studies have suggested that Chronic Cerebral Hypoperfusion (CCH) plays a critical role in disease onset and progression. However, there is a limited understanding of the underlying pathophysiology of VCI, especially in relation to CCH. Neuroinflammation is a significant contributor in the progression of VCI as increased systemic levels of the proinflammatory cytokine interleukin-1β (IL-1β) has been extensively reported in VCI patients. Recently it has been established that CCH can activate the inflammasome signaling pathways, involving NLRP3 and AIM2 inflammasomes that critically regulate IL-1β production. Given that neuroinflammation is an early event in VCI, it is important that we understand its molecular and cellular mechanisms to enable development of disease-modifying treatments to reduce the structural brain damage and cognitive deficits that are observed clinically in the elderly. Hence, this review aims to provide a comprehensive insight into the molecular and cellular mechanisms involved in the pathogenesis of CCH-induced inflammasome signaling in VCI.

Background Diagnostic performance of optical coherence tomography (OCT) to detect Alzheimer’s disease (AD) and mild cognitive impairment (MCI) remains limited. We assessed whether compensating the circumpapillary retinal nerve fiber layer (cpRNFL) thickness for multiple demographic and anatomical factors as well as the combination of macular layers improves the detection of MCI and AD. Methods This cross-sectional study of 62 AD (n = 92 eyes), 108 MCI (n = 158 eyes), and 55 cognitively normal control (n = 86 eyes) participants. Macular ganglion cell complex (mGCC) thickness was extracted. Circumpapillary retinal nerve fiber layer (cpRNFL) measurement was compensated for several ocular factors. Thickness measurements and their corresponding areas under the receiver operating characteristic curves (AUCs) were compared between the groups. The main outcome measure was OCT thickness measurements. Results Participants with MCI/AD showed significantly thinner measured and compensated cpRNFL, mGCC, and altered retinal vessel density (p p = 0.026). Combining macular and compensated cpRNFL parameters provided the best detection of MCI/AD (AUC = 0.80 vs 0.69; p Conclusions and relevance Accounting for interindividual variations of ocular anatomical features in cpRNFL measurements and incorporating macular information may improve the identification of high-risk individuals with early cognitive impairment.

Poststroke vascular cognitive impairment is highly prevalent with significant functional consequences. However, reliable biomarkers for early prediction of cognitive decline after acute ischemic stroke (AIS) are not well established. Although parenchymal imaging in patients with AIS and transient ischemic attack (TIA) may predict the resultant cognitive impairment, it may not explain the progressive deterioration after the index event. We postulated that longitudinal changes in cerebral hemodynamic parameters may influence the cognitive performance after a cerebrovascular event.One-hundred consecutive AIS/TIA patients were recruited within 2 weeks following a cerebrovascular event. At 3-6 months, 69 patients were followed up with transcranial Doppler (TCD) and brief cognitive tests (Mini-Mental State Examination [MMSE]/Montreal Cognitive Assessment [MoCA]). Basic demographics, vascular risk factors, clinical, cognitive, and neurological status were recorded.Considerable proportion (12%) of patients showed cognitive decline and changes in the hemodynamic parameters over 3-6 months after the index event. We showed that right middle cerebral artery (MCA) stenosis and right internal carotid artery/MCA tandem lesions at 3-6 months are associated with the change in the MMSE scores. Additionally, there was a trend toward association between increased pulsatility index of the right MCA and a decline in the MMSE score. However, we did not observe any association between cognitive decline and longitudinal changes in hemodynamic parameters.Although hemodynamic parameters deteriorate in a considerable proportion of patients during first 3-6 months after a cerebrovascular event, cognitive decline appears to be an independent phenomenon.

Rationale The clinical effects of neuroprotective and/or neurorestorative therapies may vary according to location and size of the ischemic injury. Imaging techniques can be useful in stratifying patients for trials that may be beneficial against particular ischemic lesion characteristics. Aim To test the hypothesis that the efficacy of NeuroAiD compared with placebo in improving functional outcome and reducing neurological deficit in patients with cerebral infarction of intermediate severity varies between sub-groups of patients randomized in the main Chinese Medicine Neuroaid Efficacy on Stroke study when categorized according to baseline imaging characteristics. Design This is a retrospective cohort sub-group analysis of patients who participated in the main Chinese Medicine Neuroaid Efficacy on Stroke study, a multicenter, double-blind, placebo-controlled trial that recruited 1100 patients within 72 h of ischemic stroke onset with National Institutes of Health Stroke Scale 6–14 and were randomized to either NeuroAiD or placebo taken four capsules three times daily for three months. Review of the baseline images to classify the acute stroke lesions in terms of size, location, and extent of involvement will be performed retrospectively by two readers who will remain blinded as to treatment allocation and outcomes of the subjects. Study outcomes The primary efficacy end-point in the main Chinese Medicine Neuroaid Efficacy on Stroke study is the modified Rankin Scale grades at three-months. Secondary efficacy end-points are the National Institutes of Health Stroke Scale score at three-months; difference of National Institutes of Health Stroke Scale scores between baseline and 10 days and between baseline and three-months; difference of National Institutes of Health Stroke Scale sub-scores between baseline and 10 days and between baseline and three-months; modified Rankin Scale at 10 days, one-month, and three-months; Barthel index at three-months; and Mini Mental State Examination at 10 days and three-months. Analysis of these primary and secondary end-points will be performed for sub-groups defined in this study after review of the baseline brain imaging: nonlacunar and lacunar, cortical and sub-cortical, hemispheric vs. brainstem, Alberta Stroke Program Early CT score

The presence of microembolic signals (MES) may indicate an increased risk of recurrent ischemic events in patients with stroke. The optimal management of such patients is uncertain. We report the effect of clopidogrel in addition to aspirin on the number of MES in a series of patients with ischemic stroke and transient ischemic attack (TIA) due to large-vessel disease.8 patients with either extracranial or intracranial artery stenosis were identified in 30-min MES studies by transcranial Doppler sonography as having MES. All patients were on antiplatelet therapy prior to baseline transcranial Doppler monitoring. The patients were subsequently treated with clopidogrel in addition to aspirin. Repeat MES studies were performed between day 3 and 7 with aspirin and clopidogrel.All patients were Chinese. The median interval time from symptom onset to initial MES study was 7 days (range of 2-30). MES donor sites included 4 severely stenosed or occluded internal carotid arteries and 4 stenosed middle cerebral arteries. The median MES number at baseline was 8 (range 3-51). Repeat MES studies showed a significant decrease in MES (p = 0.012, Wilcoxon signed ranks test). 4 patients had complete cessation of MES and all patients showed a decline in MES. No patient had recurrent strokes or bleeding complications.The rapid and significant decline of MES in our stroke and TIA patients suggests the possible efficacy of dual antiplatelet therapy with aspirin and clopidogrel in patients with MES and symptomatic large-artery occlusive disease. Randomized controlled trials should be conducted to confirm this preliminary observation.