Alterations of the cerebral cortex in sporadic small vessel disease: A systematic review of in vivo MRI data

The relationship between cortical thickness and white matter hyperintensities in mid to late life

White matter hyperintensities (WMH) are associated with cortical thinning. Although they are primarily detected in older participants, these lesions can appear in younger and midlife individuals. Here, we tested whether WMH are associated with cortical thinning in relatively younger (26-50 years) and relatively older (58-84) participants who were free of dementia, and how these associations are moderated by WMH localization. WMH were automatically quantified and categorized according to the localization of three classes of white matter tracts: association, commissural and projection fibers. Mediation analyses were used to infer whether differences in cortical thickness between younger and older participants were explained by WMH. Our results revealed that total WMH explained between 20.6 % and 65.5 % of the effect of age on cortical thickness in AD-signature regions including the lateral temporal lobes and supramarginal gyrus, among others. This mediation was slightly stronger for projection WMH, although it was still significant for association and commissural WMH. These results suggest that there is an interplay between vascular and AD causes of cognitive impairment that starts at younger ages.

Cortical microstructural involvement in cerebral small vessel disease

Background

In cerebral small vessel disease (CSVD), cortical atrophy occurs at a later stage compared to microstructural abnormalities and therefore cannot be used for monitoring short-term disease progression. We aimed to investigate whether cortical diffusion tensor imaging (DTI) and quantitative (q) magnetic resonance imaging (MRI) are able to detect early microstructural involvement of the cerebral cortex in CSVD.

Materials and Methods

33 CSVD patients without significant cortical or whole-brain atrophy and 16 healthy control subjects were included and underwent structural MRI, DTI and high-resolution qMRI with T2, T2* and T2' mapping at 3 T as well as comprehensive cognitive assessment. After tissue segmentation and reconstruction of the cortical boundaries with the Freesurfer software, DTI and qMRI parameters were saved as surface datasets and averaged across all vertices.

Results

Cortical diffusivity and quantitative T2 values were significantly increased in patients compared to controls (p < 0.05). T2 values correlated significantly positively with white matter hyperintensity (WMH) volume (p < 0.01). Both cortical diffusivity and T2 showed significant negative associations with axonal damage to the white matter fiber tracts (p < 0.05).

Conclusions

Cortical diffusivity and quantitative T2 mapping are suitable to detect microstructural involvement of the cerebral cortex in CSVD and represent promising imaging biomarkers for monitoring disease progression and effects of therapeutical interventions in clinical studies.

Reduced left hippocampal perfusion is associated with insomnia in patients with cerebral small vessel disease

OBJECTIVES

Insomnia was associated with cerebral structural changes and Alzheimer's disease. However, associations among cerebral perfusion, insomnia with cerebral small vessel disease (CSVD), and cognitive performance were little investigated.

METHODS

This cross-sectional study included 89 patients with CSVDs and white matter hyperintensities (WMHs). They were dichotomized into the normal sleep and poor sleep group, according to Pittsburgh sleep quality index (PSQI). Baseline characteristics, cognitive performance, and cerebral blood flow (CBF) were measured and compared between the two groups. The association or correlation between cerebral perfusion, cognition, and insomnia was analyzed using binary logistic regression.

RESULTS

Our study found that declined MoCA score (P = .0317) was more prevalent in those with poor sleep. There was a statistical difference in the recall (P = .0342) of MMSE, the delayed recall (P = .0289) of MoCA between the two groups. Logistic regression analysis showed educational background (P < .001) and insomnia severity index (ISI) score (P = .039) were independently correlated with MoCA scores. Arterial spin labeling demonstrated that left hippocampal gray matter perfusion was significantly reduced (P = .0384) in the group with poor sleep. And, negative correlation was found between left hippocampal perfusion and PSQI scores.

CONCLUSIONS

In the patients with CSVDs, insomnia severity was associated with cognitive decline. Left hippocampal gray matter perfusion was correlated with PSQI scores in CSVDs.

Targeting cerebral small vessel disease to promote healthy aging: Preserving physical and cognitive functions in the elderly

Cerebral small vessel disease (SVD), which is highly age-related, is the most common neuroimaging finding in community-dwelling elderly individuals. In addition to increasing the risk of dementia and stroke, SVD is associated with cognitive and physical (particularly gait speed) functional impairments in the elderly. Here, we provide evidence suggesting covert SVD, e.g. without clinically evident stroke or dementia, as a critical target to preserve the functional ability that enables well-being in older age. First, we discuss the relationship between covert SVD and geriatric syndrome. SVD lesions found in non-demented, stroke-free elderly are actually not "silent" but are associated with accelerated age-related functional decline. We also review the brain structural and functional abnormalities associated with covert SVD and the possible mechanisms underlying their contributions to SVD-related cognitive and physical functional impairments. Finally, we reveal current data, though limited, on the management of elderly patients with covert SVD to prevent SVD lesion progression and functional decline. Although it is important in aging health, covert SVD is still under-recognized or misjudged by physicians in both neurological and geriatric professions. Improving the acknowledgment, detection, interpretation, and understanding of SVD would be a multidisciplinary priority to maintain cognitive and physical functions in the elderly. The dilemmas and future directions of clinical practice and research for the elderly with covert SVD are also included in the present review.

Structural and functional alterations in cerebral small vessel disease: an ALE-based meta-analysis

 

Cerebral small vessel disease (CSVD) is one of the most important causes of stroke and dementia. Although increasing studies have reported alterations of brain structural or neuronal functional activity exhibited in patients with CSVD, it is still unclear which alterations are reliable. Here, we performed a meta-analysis to establish which brain structural or neuronal functional activity changes in those studies were consistent. Activation likelihood estimation revealed that changes in neuronal functional activity in the left angular gyrus, bilateral anterior cingulate cortex/left medial prefrontal cortex, right rolandic operculum, and alterations of gray structure in the left insular cortex/superior temporal gyrus/claustrum were reliable in sporadic CSVD. Decreased neuronal functional activity in the caudate head, anterior cingulate cortex, and reduced gray matter volume in the insular cortex/superior temporal gyrus/claustrum were associated with CSVD-related cognitive impairment. Furthermore, unlike sporadic CSVD, the reliable alterations of neuronal functional activity in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy were concentrated in the left parahippocampal gyrus. The current study presents stable brain structural and neuronal functional abnormalities within the brain, which can help further understand the pathogenesis of CSVD and CSVD-cognitive impairment and provide an index to evaluate the effectiveness of treatment protocols.

Highlights

• Default mode network and salience network are reliable networks affected in sporadic CSVD in resting-state.

• Altered corticostriatal circuitry is associated with cognitive decline.

• Decreased gray matter volume in the insular cortex is stable “remote effects” of sporadic CSVD.

• The parahippocampal gyrus may be a reliable affected brain region in CADASIL.

Small Vessel Disease, a Marker of Brain Health: What the Radiologist Needs to Know

Small vessel disease, a disorder of cerebral microvessels, is an expanding epidemic and a common cause of stroke and dementia. Despite being almost ubiquitous in brain imaging, the clinicoradiologic association of small vessel disease is weak, and the underlying pathogenesis is poorly understood. The STandards for ReportIng Vascular changes on nEuroimaging (STRIVE) criteria have standardized the nomenclature. These include white matter hyperintensities of presumed vascular origin, recent small subcortical infarcts, lacunes of presumed vascular origin, prominent perivascular spaces, cerebral microbleeds, superficial siderosis, cortical microinfarcts, and brain atrophy. Recently, the rigid categories among cognitive impairment, vascular dementia, stroke, and small vessel disease have become outdated, with a greater emphasis on brain health. Conventional and advanced small vessel disease imaging markers allow a comprehensive assessment of global brain heath. In this review, we discuss the pathophysiology of small vessel disease neuroimaging nomenclature by means of the STRIVE criteria, clinical implications, the role of advanced imaging, and future directions.

Cerebral Small-Vessel Diseases: A Look Back from 1991 to Today

BACKGROUND

Cerebral small-vessel diseases (cSVDs) encompass a number of causes involving, but not limited to, alterations in the intracranial microvasculature, leading to the accumulation of brain tissue damage and the development of various degrees of cognitive impairment, behavioral alterations, gait instability, and localization signs, often associated with the occurrence of ischemic or hemorrhagic strokes.

SUMMARY

In 2021, although key questions remain unanswered, there is general agreement on the construct, its main pathophysiological bases, and the terms used to describe its main clinical and radiological features. However, this has not always been the case, and the 30th anniversary of Cerebrovascular Diseases is an opportunity to look back from 1991 to the present to understand how a number of features, sometimes considered independent, have been progressively brought together by successive scientific breakthroughs, gradually leading to the definition of the now widely accepted concept of cSVDs. Key Messages: In the course of this journey, we will detail with particular attention the role of what we consider 2 crucial events: the advent of cerebral MRI and the building of large cohorts with monogenic forms of small-vessel disease of the brain.

The influence of white matter hyperintensities severity on functional brain activity in cerebral small vessel disease: An rs-fMRI study

OBJECTIVE

To investigate relationships between the severity of white matter hyperintensities (WMH), functional brain activity, and cognition in cerebral small vessel disease (CSVD) based on resting-state functional magnetic resonance imaging (rs-fMRI) data.

METHODS

A total of 103 subjects with CSVD were included. The amplitude of low frequency fluctuations (ALFF), regional homogeneity (ReHo), functional connectivity (FC) and their graph properties were applied to explore the influence of WMH burden on functional brain activity. We also investigated whether there are correlations between different functional brain characteristics and cognitive assessments. Finally, we selected disease-related rs-fMRI features in combination with ensemble learning to classify CSVD patients with low WMH load and with high WMH load.

RESULTS

The high WMH load group demonstrated significantly abnormal functional brain activity based on rs-MRI data, relative to the low WMH load group. ALFF and graph properties in specific brain regions were significantly correlated with patients' cognitive assessments in CSVD. Moreover, altered rs-fMRI signal can help predict the severity of WMH in CSVD patients with an overall accuracy of 92.23%.

CONCLUSIONS

This study provided a comprehensive analysis and evidence for a pattern of altered functional brain activity under different WMH load in CSVD based on rs-fMRI data, enabling accurately individual prediction of status of WMH.

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.

Abnormal Cerebral Blood Flow and Functional Connectivity Strength in Subjects With White Matter Hyperintensities

White matter hyperintensities (WMHs) are common neuroimaging findings in the aging population and are associated with various clinical symptoms, especially cognitive impairment. Abnormal global cerebral blood flow (CBF) and specific functional connections have been reported in subjects with higher WMH loads. Nevertheless, the comprehensive functional mechanisms underlying WMH are yet to be established. In this study, by combining resting-state functional magnetic resonance imaging and arterial spin labeling, we investigated the neurovascular dysfunction in subjects with WMH in CBF, functional connectivity strength (FCS), and CBF–FCS coupling. The whole-brain alterations of all these measures were explored among non-dementia subjects with different WMH loads using a fine-grained Human Brainnetome Atlas. In addition, exploratory mediation analyses were conducted to further determine the relationships between these neuroimaging indicators, WMH load, and cognition. The results showed that subjects with higher WMH loads displayed decreased CBF and FCS mainly in regions involving the cognitive- and emotional-related brain networks, including the default mode network, salience network, and central executive network. Notably, subjects with higher WMH loads also showed an abnormal regional CBF–FCS coupling in several regions of the thalamus, posterior cingulate cortex, and parahippocampal gyrus involving the default mode network. Furthermore, regional CBF in the right inferior temporal gyrus and right dorsal caudate may mediate the relationship between WMH load and cognition in WMH subjects. These findings indicated characteristic changes in cerebral blood supply, brain activity, and neurovascular coupling in regions involving specific brain networks with the development of WMH, providing further information on pathophysiology underpinnings of the WMH and related cognitive impairment.

Hippocampal vascularization patterns exert local and distant effects on brain structure but not vascular pathology in old age

The hippocampus within the medial temporal lobe is highly vulnerable to age-related pathology such as vascular disease. We examined hippocampal vascularization patterns by harnessing the ultra-high resolution of 7 Tesla magnetic resonance angiography. Dual-supply hemispheres with a contribution of the anterior choroidal artery to hippocampal blood supply were distinguished from single-supply ones with a sole dependence on the posterior cerebral artery. A recent study indicated that a dual vascular supply is related to preserved cognition and structural hippocampal integrity in old age and vascular disease. Here, we examined the regional specificity of these structural benefits at the level of medial temporal lobe sub-regions and hemispheres. In a cross-sectional study with an older cohort of 17 patients with cerebral small vessel disease (70.7  ±  9.0 years, 35.5% female) and 27 controls (71.1  ±  8.2 years, 44.4% female), we demonstrate that differences in grey matter volumes related to the hippocampal vascularization pattern were specifically observed in the anterior hippocampus and entorhinal cortex. These regions were especially bigger in dual-supply hemispheres, but also seemed to benefit from a contralateral dual supply. We further show that total grey matter volumes were greater in people with at least one dual-supply hemisphere, indicating that the hippocampal vascularization pattern has more far-reaching structural implications beyond the medial temporal lobe. A mediation analysis identified total grey matter as a mediator of differences in global cognition. However, our analyses on multiple neuroimaging markers for cerebral small vessel disease did not reveal any evidence that an augmented hippocampal vascularization conveys resistance nor resilience against vascular pathology. We propose that an augmented hippocampal vascularization might contribute to maintaining structural integrity in the brain and preserving cognition despite age-related degeneration. As such, the binary hippocampal vascularization pattern could have major implications for brain structure and function in ageing and dementia independent of vascular pathology, while presenting a simple framework with potential applicability to the clinical setting.

Cortical and Subcortical Grey Matter Abnormalities in White Matter Hyperintensities and Subsequent Cognitive Impairment

Grey matter (GM) alterations may contribute to cognitive decline in individuals with white matter hyperintensities (WMH) but no consensus has yet emerged. Here, we investigated cortical thickness and grey matter volume in 23 WMH patients with mild cognitive impairment (WMH-MCI), 43 WMH patients without cognitive impairment, and 55 healthy controls. Both WMH groups showed GM atrophy in the bilateral thalamus, fronto-insular cortices, and several parietal-temporal regions, and the WMH-MCI group showed more extensive and severe GM atrophy. The GM atrophy in the thalamus and fronto-insular cortices was associated with cognitive decline in the WMH-MCI patients and may mediate the relationship between WMH and cognition in WMH patients. Furthermore, the main results were well replicated in an independent dataset from the Alzheimer's Disease Neuroimaging Initiative database and in other control analyses. These comprehensive results provide robust evidence of specific GM alterations underlying WMH and subsequent cognitive impairment.

Small vessel disease lesion type and brain atrophy: The role of co-occurring amyloid

INTRODUCTION

It is unknown whether different types of small vessel disease (SVD), differentially relate to brain atrophy and if co-occurring Alzheimer's disease pathology affects this relation.

METHODS

In 725 memory clinic patients with SVD (mean age 67 ± 8 years, 48% female) we compared brain volumes of those with moderate/severe white matter hyperintensities (WMHs; n = 326), lacunes (n = 132) and cerebral microbleeds (n = 321) to a reference group with mild WMHs (n = 197), also considering cerebrospinal fluid (CSF) amyloid status in a subset of patients (n = 488).

RESULTS

WMHs and lacunes, but not cerebral microbleeds, were associated with smaller gray matter (GM) volumes. In analyses stratified by CSF amyloid status, WMHs and lacunes were associated with smaller total brain and GM volumes only in amyloid-negative patients. SVD-related atrophy was most evident in frontal (cortical) GM, again predominantly in amyloid-negative patients.

DISCUSSION

Amyloid status modifies the differential relation between SVD lesion type and brain atrophy in memory clinic patients.

Biomarker-Based Prediction of Progression to Dementia: F-18 FDG-PET in Amnestic MCI

Background

Metabolic patterns on brain F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) can predict the decline in amnestic mild cognitive impairment (aMCI) to Alzheimer's disease dementia (AD) or other dementias.

Objective

This study was undertaken to evaluate the diagnostic accuracy of baseline F-18 FDG-PET in aMCI for predicting conversion to AD or other dementias on follow-up.

Patients and Methods

A total of 87 patients with aMCI were enrolled in the study. Each patient underwent a detailed clinical and neuropsychological examination and FDG-PET at baseline. Each PET scan was visually classified based on predefined dementia patterns. Automated analysis of FDG PET was performed using Cortex ID (GE Healthcare). The mean follow-up duration was 30.4 ± 9.3 months (range: 18-48 months). Diagnosis of dementia at follow-up (obtained using clinical diagnostic criteria) constituted the reference standard, and all the included aMCI patients were divided into two groups: the aMCI converters (MCI-C) and MCI nonconverters (MCI-NC). Diagnostic accuracy of FDG PET was calculated using this reference standard.

Results

There were 23 MCI-C and 64 MCI-NC. Of the 23 MCI-C, 19 were diagnosed as probable AD, 1 as frontotemporal demetia (FTD), and 3 as vascular dementia (VD). Of the 64 MCI-NC, 9 had subjective improvement in cognition, and 55 remained stable. The conversion rate for all types of dementia in our series was 26.4% (23/87) and for Alzheimer's type dementia was 21.8% (19/87). The of PET-based visual interpretation was 91.9%. Sensitivity, specificity, positive predictive value, and negative predictive value for FDG-PET-based prediction of dementia conversion were 86.9% [confidence interval (CI) 66.4%-97.2%)], 93.7% (CI 84.7%-98.2%), 83.3% (CI 65.6%-92.9%), and 95.2% (CI 87.4%-98.9%), respectively. Kappa for agreement between visual and Cortex ID was 0.94 indicating excellent agreement. In the three aMCI patients progressing to VD, no specific abnormality in metabolic pattern was noted; however, there was marked cortical atrophy on computed tomography.

Conclusion

FDG-PET-based visual and cortex ID classification has a good accuracy in predicting progression to dementia including AD in the prodromal aMCI phase. Absence of typical metabolic patterns on FDG-PET can play an important exclusionary role for progression to dementia. Vascular cognitive impairment with cerebral atrophy needs further studies to confirm and uncover potential mechanisms.

Endothelial-derived plasma exosome proteins in Alzheimer's disease angiopathy

Small cerebral vascular disease (SCeVD) demonstrated by white matter hyperintensity (WMH) on MRI contributes to the development of dementia in Alzheimer's disease (AD), but it has not been possible to correlate onset, severity, or protein components of SCeVD with characteristics of WMH in living patients. Plasma endothelial-derived exosomes (EDEs) were enriched by two-step immunoabsorption from four groups of participants with no clinical evidence of cerebrovascular disease: cognitively normal (CN) without WMH (CN without SCeVD, n = 20), CN with SCeVD (n = 22), preclinical AD (pAD) + mild cognitive impairment (MCI) without SCeVD (pAD/MCI without SCeVD, n = 22), and pAD/MCI with SCeVD (n = 16) for ELISA quantification of cargo proteins. Exosome marker CD81-normalized EDE levels of the cerebrovascular-selective biomarkers large neutral amino acid transporter 1 (LAT-1), glucose transporter type 1 (Glut-1), and permeability-glycoprotein (p-GP, ABCB1) were similarly significantly higher in the CN with SCeVD and pAD/MCI with SCeVD groups than their corresponding control groups without SCeVD. CD81-normalized EDE levels of Aβ40 and Aβ42 were significantly higher in the pAD/MCI with SCeVD group but not in the CN with SCeVD group relative to controls without SCeVD. Levels of normal cellular prion protein (PrPc), a receptor for amyloid peptides, and phospho-181T-tau were higher in both CN and pAD/MCI with SCeVD groups than in the corresponding controls. High EDE levels of Aβ40, Aβ42, and phospho-181T-tau in patients with WMH suggesting SCeVD appear at the pre-clinical or MCI stage of AD and therapeutic lowering of neurotoxic peptide levels may delay progression of AD angiopathy.

Invited Review: The spectrum of age-related small vessel diseases: potential overlap and interactions of amyloid and nonamyloid vasculopathies

Deep perforator arteriopathy (DPA) and cerebral amyloid angiopathy (CAA) are the commonest known cerebral small vessel diseases (CSVD), which cause ischaemic stroke, intracebral haemorrhage (ICH) and vascular cognitive impairment (VCI). While thus far mainly considered as separate entities, we here propose that DPA and CAA share similarities, overlap and interact, so that 'pure' DPA or CAA are extremes along a continuum of age-related small vessel pathologies. We suggest blood-brain barrier (BBB) breakdown, endothelial damage and impaired perivascular β-amyloid (Aβ) drainage are hallmark common mechanisms connecting DPA and CAA. We also suggest a need for new biomarkers (e.g. high-resolution imaging) to deepen understanding of the complex relationships between DPA and CAA.

A cortical microvascular structure in vascular dementia, Alzheimer's disease, frontotemporal lobar degeneration and nondemented controls: a sign of angiogenesis due to brain ischaemia?

Aims

We observed a microvascular structure in the cerebral cortex that has not, to our knowledge, been previously described. We have termed the structure a ‘raspberry’, referring to its appearance under a bright‐field microscope. We hypothesized that raspberries form through angiogenesis due to some form of brain ischaemia or hypoperfusion. The aims of this study were to quantify raspberry frequency within the cerebral cortex according to diagnosis (vascular dementia, Alzheimer's disease, frontotemporal lobar degeneration and nondemented controls) and brain regions (frontal, temporal, parietal and occipital cortices, regardless of diagnosis).

Materials and methods

In each of 10 age‐matched subjects per group, a 20‐mm section of the cerebral cortex was examined in haematoxylin‐and‐eosin‐stained sections of the frontal, temporal and parietal, and/or occipital lobes. Tests were performed to validate the haematoxylin‐and‐eosin‐based identification of relative differences between the groups, and to investigate inter‐rater variability.

Results

Raspberry frequency was highest in subjects with vascular dementia, followed by those with frontotemporal lobar degeneration, Alzheimer's disease and last, nondemented controls. The frequency of raspberries in subjects with vascular dementia differed from that of all other groups at a statistically significant level. In the cerebral lobes, there was a statistically significant difference between the frontal and occipital cortices.

Conclusions

We believe the results support the hypothesis that raspberries are a sign of angiogenesis in the adult brain. It is pertinent to discuss possible proangiogenic stimuli, including brain ischaemia (such as mild hypoperfusion due to a combination of small vessel disease and transient hypotension), neuroinflammation and protein pathology.

The association between hypertensive arteriopathy and cerebral amyloid angiopathy in spontaneously hypertensive stroke-prone rats

We aimed to test the hypothesis that in spontaneously hypertensive stroke‐prone rats (SHRSP), non‐amyloid cerebral small vessel disease/hypertensive arteriopathy (HA) results in vessel wall injury that may promote cerebral amyloid angiopathy (CAA). Our study comprised 21 male SHRSP (age 17–44 weeks) and 10 age‐ and sex‐matched Wistar control rats, that underwent two‐photon (2PM) imaging of the arterioles in the parietal cortex using Methoxy‐X04, Dextran and cerebral blood flow (CBF) measurements. Our data suggest that HA in SHRSP progresses in a temporal and age‐dependent manner, starting from small vessel wall damage (stage 1A), proceeding to CBF reduction (stage 1B), non‐occlusive (stage 2), and finally, occlusive thrombi (stage 3). Wistar animals also demonstrated small vessel wall damage, but were free of any of the later HA stages. Nearly half of all SHRSP additionally displayed vascular Methoxy‐X04 positivity indicative of cortical CAA. Vascular β‐amyloid deposits were found in small vessels characterized by thrombotic occlusions (stage 2 or 3). Post‐mortem analysis of the rat brains confirmed the findings derived from intravital 2PM microscopy. Our data thus overall suggest that advanced HA may play a role in CAA development with the two small vessel disease entities might be related to the same pathological spectrum of the aging brain.

Individual differences in regional cortical volumes across the life span are associated with regional optical measures of arterial elasticity

Aging is often accompanied by changes in brain anatomy and cerebrovascular health. However, the specific relationship between declines in regional cortical volumes and loss of cerebral arterial elasticity is less clear, as only global or very localized estimates of cerebrovascular health have been available. Here we employed a novel tomographic optical method (pulse-DOT) to derive local estimates of cerebral arterial elasticity and compared regional volumetric estimates (obtained with FreeSurfer) with optical arterial elasticity estimates from the same regions in 47 healthy adults (aged 18-75). Between-subject analyses revealed a global correlation between cortical volume and cortical arterial elasticity, which was a significant mediator of the association between age and cortical volume. Crucially, a novel within-subject analysis highlighted the spatial association between regional variability in cortical volumes and arterial elasticity in the same regions. This association strengthened with age. Gains in the predictability of cortical volumes from arterial elasticity data were obtained by sharpening the resolution up to individual cortical regions. These results indicate that some of the variance of sub-clinical age-related brain atrophy is associated with differences in the status of cerebral arteries, and can help explain the unique patterns of brain atrophy found within each individual.

Better Correlation of Cognitive Function to White Matter Integrity than to Blood Supply in Subjects with Leukoaraiosis

Leukoaraiosis is associated with increased risk of cognitive impairment, but its pathophysiological pathway is unclear. The aim of the present study was to determine whether brain structural damage or cerebral blood supply better correlated with the global cognitive outcome in subjects with leukoaraiosis. Seventy-five subjects with leukoaraiosis were included in present study, with age ranged from 43 to 85 years, with mean white matter hyperintensities (WMH) volume 30.69 ± 24.35 mL. Among them, 19(25.33%) subjects presented with cerebral microbleeds (CMB) and 40 (53.33%) subjects presented with lacunes. These participants received arterial spin labeling perfusion MRI, diffusion-tensor imaging (DTI) and diffusion Kurtosis imaging. We analyzed the cerebral blood flow (CBF) by dividing the brain tissue into three regions: WMH, normal appearing white matter (NAWM) and cortex. After adjusting for age and gender, the CBF of NAWM was significantly correlated with fractional anisotropy (FA) (r = 0.336, p = 0.004) and mean diffusion (MD) (r = -0.271, p = 0.020) of NAWM, while there lacked of association between CBF of cortex and mean kurtosis (MK) of cortex (r = -0.015, p = 0.912). Meanwhile, both NAWM-FA (r = -0.443, p < 0.001) and NAWM-MD (r = 0.293, p = 0.012), as well as cortex-MK (r = -0.341, p = 0.012) was significantly correlated with WMH volume. Univariate regression analysis demonstrated that global cognitive function was significantly associated with mean FA or MD of both WMH and NAWM, and cortex-CBF, but neither with the cortex-MK, nor the presences of CMB or lacunes. Finally, multiple linear regression analysis revealed that global cognitive function was independently associated with NAWM-FA (standardized β = 0.403, p < 0.001) and WMH-FA (Standardized β = 0.211, p = 0.017), but not with the cortex-CBF. A model that contained NAWM-FA, WMH-FA and years of education explained 49% of the variance of global cognitive function. Cerebral perfusion status might have a significant impact on the maintenance of white matter integrity in subjects with leukoaraiosis. Global cognitive function was more strongly associated with white matter integrity than with blood supply. DTI parameters, especially FA could serve as a potent imaging indicator for detecting the invisible alteration of white matter integrity and implying its potential cognitive relevance.

Vascular Cognitive Impairment

Cerebrovascular disease typically manifests with stroke, cognitive impairment, or both. Vascular cognitive impairment refers to all forms of cognitive disorder associated with cerebrovascular disease, regardless of the specific mechanisms involved. It encompasses the full range of cognitive deficits from mild cognitive impairment to dementia. In principle, any of the multiple causes of clinical stroke can cause vascular cognitive impairment. Recent work further highlights a role of microinfarcts, microhemorrhages, strategic white matter tracts, loss of microstructural tissue integrity, and secondary neurodegeneration. Vascular brain injury results in loss of structural and functional connectivity and, hence, compromise of functional networks within the brain. Vascular cognitive impairment is common both after stroke and in stroke-free individuals presenting to dementia clinics, and vascular pathology frequently coexists with neurodegenerative pathology, resulting in mixed forms of mild cognitive impairment or dementia. Vascular dementia is now recognized as the second most common form of dementia after Alzheimer's disease, and there is increasing awareness that targeting vascular risk may help to prevent dementia, even of the Alzheimer type. Recent advances in neuroimaging, neuropathology, epidemiology, and genetics have led to a deeper understanding of how vascular disease affects cognition. These new findings provide an opportunity for the present reappraisal of vascular cognitive impairment. We further briefly address current therapeutic concepts.

Focal Macroscopic Cortical Lesions in Cerebral Autosomal-Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy

Background and Purpose—

Cortical microinfarcts and secondary cortical degeneration have been demonstrated in cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a severe monogenic cerebral small vessel disease. The aim of this study was to determine whether focal macroscopic cortical lesions can be detected using a specific in vivo magnetic resonance imaging approach.

Methods—

Three-dimensional T1 magnetic resonance imaging scans were obtained in 28 nondemented nondisabled CADASIL patients and 29 age- and sex-matched controls. The cortical mantle of patients and controls were extracted using Brainvisa by an experienced user and then evaluated during a dedicated reading session by a second reader after removing the white matter to stay blind to the clinical status. Thereafter, confirmed focal macroscopic cortical lesions were characterized using all available imaging data, including 7-T magnetic resonance imaging in some patients.

Results—

Three focal macroscopic cortical lesions were confirmed in 3 of 28 patients (11%) but none in controls. All lesions were observed in the close vicinity of severe signal changes in the underlying white matter.

Conclusions—

Focal macroscopic cortical lesions can be detected using specific magnetic resonance imaging approaches in CADASIL patients long before the end stage of the disorder. The underlying mechanisms and precise clinical consequences of these cortical changes still need to be determined.

Intravoxel Incoherent Motion Imaging in Small Vessel Disease: Microstructural Integrity and Microvascular Perfusion Related to Cognition

BACKGROUND AND PURPOSE

Cerebral small vessel disease (SVD) is associated with cognitive impairment. This may be because of decreased microstructural integrity and microvascular perfusion, but data on these relationships are scarce. We determined the relationship between cognition and microvascular perfusion and microstructural integrity in SVD patients, using intravoxel incoherent motion imaging-a diffusion-weighted magnetic resonance imaging technique designed to determine microvascular perfusion and microstructural integrity simultaneously.

METHODS

Seventy-three patients with SVD and 39 controls underwent intravoxel incoherent motion imaging and neuropsychological assessment. Parenchymal diffusivity D (a surrogate measure of microstructural integrity) and perfusion-related measure fD* were calculated for the normal appearing white matter, white matter hyperintensities, and cortical gray matter. The associations between cognitive performance and D and fD* were determined.

RESULTS

In SVD patients, multivariable analysis showed that lower fD* in the normal appearing white matter and cortical gray matter was associated with lower overall cognition (P=0.03 and P=0.002, respectively), lower executive function (P=0.04 and P=0.01, respectively), and lower information-processing speed (P=0.04 and P=0.01, respectively). D was not associated with cognitive function. In controls, no association was found between D, fD*, and cognition.

CONCLUSIONS

In SVD patients, lower cognitive performance is associated with lower microvascular perfusion in the normal appearing white matter and cortical gray matter. Our results support recent findings that both cortical gray matter and normal appearing white matter perfusion may play a role in the pathophysiology of cognitive dysfunction in SVD.

CLINICAL TRIAL REGISTRATION

URL: http://www.trialregister.nl. Unique identifier: NTR3786.