Cerebral microinfarcts affect brain structural network topology in cognitively impaired patients

Loss of white matter integrity mediates the association between cortical cerebral microinfarcts and cognitive dysfunction: A longitudinal study

Cortical cerebral microinfarcts (CMIs) are associated with loss of white matter (WM) integrity and cognitive impairment in cross-sectional studies, while further investigation using longitudinal datasets is required. This study aims to establish the association between cortical CMIs and WM integrity assessed by diffusion-tensor imaging (DTI) measures and to investigate whether DTI measures mediate the relationship between cortical CMIs and cognitive decline. Cortical CMIs were graded on 3T MRI. DTI measures were derived from histogram analysis of mean diffusivity (MD) and fractional anisotropy (FA). Cognitive function was assessed using a neuropsychological test battery. Linear mixed-effect models were employed to examine associations of cortical CMIs with longitudinal changes in DTI measures and cognitive function. Final analysis included 231 patients (71.14 ± 7.60 years). Presence of cortical CMIs at baseline was associated with longitudinal changes in MD median and peak height and FA median and peak height, as well as global cognition (β = -0.50, 95%CI: -0.91, -0.09) and executive function (β = -0.77, 95%CI: -1.25, -0.28). MD median mediated the cross-sectional association between cortical CMIs and global cognition. Further studies are required to investigate whether cortical CMIs and loss of WM integrity are causally related or if they are parallel mechanisms that contribute to cognitive decline.

Blood-based biomarkers of cerebral small vessel disease

Age-associated cerebral small vessel disease (CSVD) represents a clinically heterogenous condition, arising from diverse microvascular mechanisms. These lead to chronic cerebrovascular dysfunction and carry a substantial risk of subsequent stroke and vascular cognitive impairment in aging populations. Owing to advances in neuroimaging, in vivo visualization of cerebral vasculature abnormities and detection of CSVD, including lacunes, microinfarcts, microbleeds and white matter lesions, is now possible, but remains a resource-, skills- and time-intensive approach. As a result, there has been a recent proliferation of blood-based biomarker studies for CSVD aimed at developing accessible screening tools for early detection and risk stratification. However, a good understanding of the pathophysiological processes underpinning CSVD is needed to identify and assess clinically useful biomarkers. Here, we provide an overview of processes associated with CSVD pathogenesis, including endothelial injury and dysfunction, neuroinflammation, oxidative stress, perivascular neuronal damage as well as cardiovascular dysfunction. Then, we review clinical studies of the key biomolecules involved in the aforementioned processes. Lastly, we outline future trends and directions for CSVD biomarker discovery and clinical validation.

Relationship between Cerebral Microinfarcts and Dementia by Sex: Findings from a community-based Autopsy Study

Cerebral microinfarcts are common in older adults and are associated with cognitive impairment. Less is known about sex-related variation in the relationship between cerebral microinfarcts and dementia in older adults, the examination of which was the objective of this study. This case-control study was based on the 727 participants (419 women) in the Adult Changes in Thought (ACT) autopsy data. Microinfarcts were ascertained by blinded board-certified neuropathologists, and dementia diagnoses were made by the ACT Consensus Diagnosis Conference per DSM-IV. Multivariable logistic regression models were used to estimate adjusted odds ratio (aOR) and 95% confidence interval (CI). Microinfarcts were present in 49% (356/727) of the participants, which was numerically higher in women: 51% (213/419) vs 46% (143/308). aOR (95% CI) for dementia associated with any microinfarct for female and male participants were 1.45 (0.91-2.30) and 1.24 (0.75-2.06), respectively (p for interaction, 0.34). Respective aORs (95%CIs) associated with ≥2 microinfarcts were 1.37 (0.79-2.36) and 1.53 (0.84-2.78), with interaction p, 0.84. Subcortical microinfarcts were present in 36% (138/381) and 23% (78/346) of patients with and without dementia (aOR, 1.65; 95% CI, 1.14-2.38). Respective aOR (95% CI) in female and male participants were 1.70 (1.03-2.82) and 1.59 (0.90-2.80), (p for interaction, 0.55). There was no association with cortical microinfarcts (aOR, 1.19; 95% CI, 0.83-1.69). These findings suggest that association between microinfarcts and dementia is primarily mediated by subcortical microinfarcts, but we found no evidence of sex-related variation. Future studies with greater power are needed to determine if the associations we found are replicable.

Cerebral microinfarcts revisited: Detection, causes, and clinical relevance

Cerebral microinfarcts (CMIs) are small ischemic lesions invisible to the naked eye at brain autopsy, while the larger ones (0.5-4 mm in diameter) have been visualized in-vivo on magnetic resonance imaging (MRI). CMIs can be detected on diffusion-weighted imaging (DWI) as incidental small DWI-positive lesions (ISDPLs) and on structural MRI for those confined to the cortex and in the chronic phase. ISDPLs may evolve into old cortical-CMIs, white matter hyperintensities or disappear depending on their location and size. Novel techniques in neuropathology and neuroimaging facilitate the detection of CMIs, which promotes understanding of these lesions. CMIs have heterogeneous causes, involving both cerebral small- and large-vessel disease as well as heart diseases such as atrial fibrillation and congestive heart failure. The underlying mechanisms incorporate vascular remodeling, inflammation, blood-brain barrier leakage, penetrating venule congestion, cerebral hypoperfusion, and microembolism. CMIs lead to clinical outcomes, including cognitive decline, a higher risk of stroke and mortality, and accelerated neurobehavioral disturbances. It has been suggested that CMIs can impair brain function and connectivity beyond the microinfarct core and are also associated with perilesional and global cortical atrophy. This review aims to summarize recent progress in studies involving both cortical-CMIs and ISDPLs since 2017, including their detection, etiology, risk factors, MRI correlates, and clinical consequences.

Relationships between Cerebral Vasculopathies and Microinfarcts in a Community-Based Cohort of Older Adults

Cerebral microinfarcts are associated with cognitive impairment and dementia. Small vessel diseases such as cerebral arteriolosclerosis and cerebral amyloid angiography (CAA) have been found to be associated with microinfarcts. Less is known about the associations of these vasculopathies with the presence, numbers, and location of microinfarcts. These associations were examined in the clinical and autopsy data of 842 participants in the Adult Changes in Thought (ACT) study. Both vasculopathies were categorized by severity (none, mild, moderate, and severe) and region (cortical and subcortical). Odds ratios (OR) and 95% CIs for microinfarcts associated with arteriolosclerosis and CAA adjusted for possible modifying covariates such as age at death, sex, blood pressure, APOE genotype, Braak, and CERAD were estimated. 417 (49.5%) had microinfarcts (cortical, 301; subcortical, 249), 708 (84.1%) had cerebral arteriolosclerosis, 320 (38%) had CAA, and 284 (34%) had both. Ors (95% CI) for any microinfarct were 2.16 (1.46-3.18) and 4.63 (2.90-7.40) for those with moderate (n = 183) and severe (n = 124) arteriolosclerosis, respectively. Respective Ors (95% CI) for the number of microinfarcts were 2.25 (1.54-3.30) and 4.91 (3.18-7.60). Similar associations were observed for cortical and subcortical microinfarcts. Ors (95% Cis) for the number of microinfarcts associated with mild (n = 75), moderate (n = 73), and severe (n = 15) amyloid angiopathy were 0.95 (0.66-1.35), 1.04 (0.71-1.52), and 2.05 (0.94-4.45), respectively. Respective Ors (95% Cis) for cortical microinfarcts were 1.05 (0.71-1.56), 1.50 (0.99-2.27), and 1.69 (0.73-3.91). Respective Ors (95% Cis) for subcortical microinfarcts were 0.84 (0.55-1.28), 0.72 (0.46-1.14), and 0.92 (0.37-2.28). These findings suggest a significant association of cerebral arteriolosclerosis with the presence, number, and location (cortical and subcortical) of microinfarcts, and a weak and non-significant association of CAA with each microinfarct, highlighting the need for future research to better understand the role of small vessel diseases in the pathogenesis of cerebral microinfarcts.

Deep cortical microinfarction induced by femtosecond laser in mice: Long-term secondary pathological changes in corresponding superficial cortex

BACKGROUND AND PURPOSE

Previous studies have explored the clinical consequences of cortical microinfarction, mainly age-related cognitive decline. However, functional impairment of deep cortical microinfarction remains poorly understood. Based on anatomical knowledge and previous research, we infer that damage to the deep cortex may lead to cognitive deficits and communication impairment between the superficial cortex and thalamus. This study aimed to develop a new model of deep cortical microinfarction based on femtosecond laser ablation of a perforating artery.

METHODS

Twenty-eight mice were anesthetized with isoflurane, and a cranial window was thinned using a microdrill. Intensively focused femtosecond laser pulses were used to produce perforating arteriolar occlusions and ischemic brain damage was examined using histological analysis.

RESULTS

Occlusion of different perforating arteries induced different types of cortical microinfarctions. Blocking the perforating artery, which enters the cerebral cortex vertically and has no branches within 300 μm below, can result in deep cortical microinfarction. Moreover, this model showed neuronal loss and microglial activation in the lesions as well as dysplasia of nerve fibers and β-amyloid deposition in the corresponding superficial cortex.

CONCLUSIONS

We present here a new model of deep cortical microinfarction in mice, in which specific perforating arteries are selectively occluded by a femtosecond laser, and we preliminarily observe several long-term effects related to cognition. This animal model is helpful in investigating the pathophysiology of deep cerebral microinfarction. However, further clinical and experimental studies are required to explore deep cortical microinfarctions in greater molecular and physiological detail.

Patients with Alzheimer's disease dementia show partially preserved parietal 'hubs' modeled from resting-state alpha electroencephalographic rhythms

Introduction

Graph theory models a network by its nodes (the fundamental unit by which graphs are formed) and connections. 'Degree' hubs reflect node centrality (the connection rate), while 'connector' hubs are those linked to several clusters of nodes (mainly long-range connections).

Methods

Here, we compared hubs modeled from measures of interdependencies of between-electrode resting-state eyes-closed electroencephalography (rsEEG) rhythms in normal elderly (Nold) and Alzheimer's disease dementia (ADD) participants. At least 5 min of rsEEG was recorded and analyzed. As ADD is considered a 'network disease' and is typically associated with abnormal rsEEG delta (<4 Hz) and alpha rhythms (8-12 Hz) over associative posterior areas, we tested the hypothesis of abnormal posterior hubs from measures of interdependencies of rsEEG rhythms from delta to gamma bands (2-40 Hz) using eLORETA bivariate and multivariate-directional techniques in ADD participants versus Nold participants. Three different definitions of 'connector' hub were used.

Results

Convergent results showed that in both the Nold and ADD groups there were significant parietal 'degree' and 'connector' hubs derived from alpha rhythms. These hubs had a prominent outward 'directionality' in the two groups, but that 'directionality' was lower in ADD participants than in Nold participants.

Discussion

In conclusion, independent methodologies and hub definitions suggest that ADD patients may be characterized by low outward 'directionality' of partially preserved parietal 'degree' and 'connector' hubs derived from rsEEG alpha rhythms.

Cell non-autonomous regulation of cerebrovascular aging processes by the somatotropic axis

Age-related cerebrovascular pathologies, ranging from cerebromicrovascular functional and structural alterations to large vessel atherosclerosis, promote the genesis of vascular cognitive impairment and dementia (VCID) and exacerbate Alzheimer's disease. Recent advances in geroscience, including results from studies on heterochronic parabiosis models, reinforce the hypothesis that cell non-autonomous mechanisms play a key role in regulating cerebrovascular aging processes. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) exert multifaceted vasoprotective effects and production of both hormones is significantly reduced in aging. This brief overview focuses on the role of age-related GH/IGF-1 deficiency in the development of cerebrovascular pathologies and VCID. It explores the mechanistic links among alterations in the somatotropic axis, specific macrovascular and microvascular pathologies (including capillary rarefaction, microhemorrhages, impaired endothelial regulation of cerebral blood flow, disruption of the blood brain barrier, decreased neurovascular coupling, and atherogenesis) and cognitive impairment. Improved understanding of cell non-autonomous mechanisms of vascular aging is crucial to identify targets for intervention to promote cerebrovascular and brain health in older adults.

Role of endocrine PACAP in age-related diseases

Pituitary adenylate cyclase activating polypeptide (PACAP) is a conserved neuropeptide, which confers diverse anti-aging endocrine and paracrine/autocrine effects, including anti-apoptotic, anti-inflammatory and antioxidant action. The results of the in vivo and in vitro experiments show that increasing emphasis is being placed on the diagnostic/prognostic biomarker potential of this neuropeptide in a wide array of age-related diseases. After the initial findings regarding the presence and alteration of PACAP in different body fluids in physiological processes, an increasing number of studies have focused on the changes of its levels in various pathological conditions associated with advanced aging. Until 2016 - when the results of previous human studies were reviewed - a vast majority of the studies had dealt with age-related neurological diseases, like cerebrovascular and neurodegenerative diseases, multiple sclerosis, as well as some other common diseases in elderly such as migraine, traumatic brain injury and post-traumatic stress disorder, chronic hepatitis and nephrotic syndrome. The aim of this review is to summarize the old and the new results and highlight those 'classical' and emerging clinical fields in which PACAP may become subject to further investigation as a diagnostic and/or prognostic biomarker in age-related diseases.

The Impact of Cortical Cerebral Microinfarcts on Functional Outcomes in Patients With Ischemic Stroke

The present study examined cortical cerebral microinfarcts (CMIs) on a 3T magnetic resonance imaging and investigated the impact of CMIs on the comprehensive functional outcomes during the post-stroke rehabilitation period. Patients with acute phase of first-ever ischemic stroke were retrospectively recruited (n = 62) and divided into 2 groups with and without CMIs. Clinical parameters including age, sex, stroke lesion laterality, location, the National Institutes of Health Stroke Scale score, as well as history of hypertension, dyslipidemia, diabetes mellitus, and smoking were obtained. Functional outcomes were assessed twice at baseline and one month later with the Korean version of the Mini-Mental State Examination, the Berg balance scale (BBS), and the functional independence measure. Partial correlation and multiple linear regression analyses were used to examine the relationship between the presence of CMIs and the change in functional outcomes. At least one CMI was reported in 27 patients, who were older (p = 0.043). The presence of CMIs was significantly associated with functional impairment in all 3 functional outcomes, after controlling for confounding factors (p < 0.05). CMIs might contribute to poor functional outcomes during the post-stroke rehabilitation period. These results suggest that CMIs should be considered when establishing rehabilitation treatment strategies or making a prognosis.

The role of inflammasomes in vascular cognitive impairment

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.

Development and validation of prediction models for neurocognitive disorders in adult patients admitted to the ICU with sleep disturbance

BACKGROUND

Neurocognitive disorders (NCDs) and sleep disturbance are highly prevalent in the perioperative period and intensive care unit (ICU). There has been a lack of individualized evaluation tools designed for the high-risk NCDs in critically ill patients with sleep disturbance.

OBJECTIVES

The aim of this study was to develop and validate prediction models for NCDs among adult patients with sleep disturbance.

METHODS

The R software was used to analyze the dataset of adult patients admitted to the ICU with sleep disturbance, who were diagnosed following the codes of the International Classification of Diseases, 9th Revision (ICD-9) and 10th Revision (ICD-10) using the MIMIC-IV database. We used logistic regression and LASSO analyses to identify important risk factors associated with NCDs and develop nomograms for NCDs predictions. We measured the performances of the nomograms using the bootstrap resampling procedure, sensitivity, specificity of the receiver operating characteristic (ROC), area under the ROC curves (AUC), and decision curve analysis (DCA).

RESULTS

The prediction models shared the 10 risk factors (age, gender, midazolam, morphine, glucose, diabetes diseases, potassium, international normalized ratio, partial thromboplastin time, and respiratory rate). Cardiovascular diseases were included in the logistic regression, the sensitivity was 74.1%, and specificity was 64.6%. When platelet and Glasgow Coma Score (GCS) were included and cardiovascular diseases were removed in the LASSO prediction model, the sensitivity was 86.1% and specificity was 82.8%. Discriminative abilities of the logistic prediction and LASSO prediction models for NCDs in the validation set were evaluated as the AUC scores, which were 0.730 (95% CI 0.716-0.743) and 0.920 (95% CI 0.912-0.927). Net benefits of the prediction models were observed at threshold probabilities of 0.567 and 0.914.

CONCLUSIONS

The LASSO prediction model showed better performance than the logistic prediction model and should be preferred for nomogram-assisted decisions on clinical risk management of NCDs among adult patients with sleep disturbance in the ICU.

Association Between Cerebral Cortical Microinfarcts and Perilesional Cortical Atrophy on 3T MRI

BACKGROUND AND OBJECTIVES

Cerebral cortical microinfarcts (CMIs) are a novel MRI-marker of cerebrovascular disease (CeVD) that predicts accelerated cognitive decline. Presence of CMIs is known to be associated with global cortical atrophy, although the mechanism linking the two is unclear. Our primary objective was to examine the relation between CMIs and cortical atrophy and establish possible perilesional atrophy surrounding CMIs. Our secondary objective was to examine the role of cortical atrophy in CMI-associated cognitive impairment.

METHODS

Patients were recruited from two Singapore memory clinics between December 2010 and September 2013 and included if they received the diagnosis no objective cognitive impairment, cognitive impairment (with or without a history of stroke) or Alzheimer's or vascular dementia. Cortical thickness, chronic cortical microinfarcts and MRI-markers of CeVD were assessed on 3T MRI. Patients underwent cognitive testing. Cortical thickness was compared globally between patients with and without CMIs, regionally within individual patients with CMIs comparing brain regions with CMIs to the corresponding contralateral region without CMIs and locally within individuals patients in a 50 mm radius of CMIs. Global cortical thickness was analyzed as mediator in the relation between CMI and cognitive performance.

RESULTS

Of the 238 patients (mean age 72.5 SD 9.1 years) enrolled, 75 had ≥1 CMIs. Patient with CMIs had a 2.1% lower global cortical thickness (B=-.049 mm, 95% CI [.091; -.007] p=.022) compared to patients without CMIs, after correction for age, sex, education and intracranial volume. In patients with CMIs, cortical thickness in brain regions with CMIs was 2.2 % lower than in contralateral regions without CMIs (B=-.048 mm [-.071; -.026] p<.001). In a 20 mm radius area surrounding the CMI-core, cortical thickness was lower than in the area 20-50 mm from the CMI-core (Mean difference -.06 mm 95% CI [-.10; -.02] p=.002). Global cortical thickness was a significant mediator in the relationship between CMI presence and cognitive performance as measure with the Mini-Mental State Examination (B=-.12 [-.22; -.01] p=.025).

DISCUSSION

We found cortical atrophy surrounding CMIs, suggesting a perilesional effect in a cortical area many times larger than the CMI-core. Our findings support the notion that CMIs affect brain structure beyond the actual lesion site.