MRI-Visible Perivascular Spaces and Risk of Incident Dementia: The Framingham Heart Study

Relation of MRI visible perivascular spaces with global and regional brain structural connectivity measures: The Framingham Heart Study (FHS)

MRI visible perivascular spaces (PVS) are associated with cognitive impairment and dementia, which are also associated with disrupted network connectivity. PVS may relate to dementia risk through disruption in brain connectivity. We studied the relation between PVS grade and global and regional structural connectivity in Framingham Heart Study participants free of stroke and dementia. PVS were rated on axial T2 sequences in the basal ganglia (BG) and centrum semiovale (CSO). We assessed structural global and regional network architecture using global efficiency, local efficiency and modularity. Analysis of covariance was used to relate PVS grades with structural network measures. Models adjusted for age, sex (model 1), and vascular risk factors (model 2). Effect modification on the associations by age, sex, hypertension and APOE-ɛ4 status was assessed. Among 2525 participants (mean age 54 ± 13 years, 53 % female), significant associations were observed between grade III and IV PVS in the BG and CSO with reduced global efficiency. Grade III (β -0.0030; 95 % confidence interval [CI] -0.0041, -0.0019) and IV (β -0.0033, CI -0.0060, -0.0007) PVS in the BG and grade IV (β -0.0015; CI -0.0024, -0.0007) PVS in the CSO were associated with reduced local efficiency. We observed shared and different strength of association by age, hypertension, sex and APOE-ɛ4 in the relationship between high burden PVS in the BG and CSO with structural network measures. Findings suggest that higher grade PVS are associated with disruption of global and regional structural brain networks.

Cerebral small vessel disease among rural-dwelling Chinese older adults: prevalence, distribution, and associated factors

Epidemiological characteristics of cerebral small vessel disease (cSVD) in the general population, especially among rural older adults, are poorly defined. Here, we reported the prevalence, distribution, and associated factors of cSVD in a rural-dwelling older population in China. This population-based cross-sectional study included 1272 older adults (age ≥60 years; mean age 69.43 years; 58.57% women) who underwent structural brain MRI scans (3.0T) in 2018-2020. MRI markers of cSVD were assessed following the Standards for Reporting Vascular Changes on Neuroimaging-1 criteria. We performed descriptive and regression analyses. The overall prevalence was 20.31% for cerebral microbleeds (CMBs), 26.87% for lacunes, 60.06% for basal ganglia perivascular spaces (PVS), 76.31% for centrum semiovale PVS, 95.74% for deep white matter hyperintensities (WMHs), and 94.17% for periventricular WMHs. The prevalence increased with advancing age for all cSVD markers, except PVS in the centrum semiovale. The prevalence of moderate-to-severe deep WMHs was higher in women than in men (P = 0.005). Older age and hypertension were associated with increased likelihoods of all cSVD markers. A higher body mass index was linked to more WMHs. Coronary heart disease (CHD) was associated with WMHs, CMBs, and lacunes. Our study suggests that cSVD, especially WMHs and PVS, was highly prevalent among rural Chinese older adults. Older age, hypertension, and CHD are associated with distinct cSVD. Future prospective cohort studies are warranted to determine incidence and major risk factors of cSVD, which could facilitate preventive interventions to reduce the burden of cSVD in resource-limited settings.

Cerebrovascular burden and neurodegeneration linked to 15-year odor identification decline in older adults

Background

The mechanisms underlying olfactory decline in aging need further investigation. Noticeably, the longitudinal relationship of biological markers with olfaction remains underexplored. We investigated whether baseline levels and progression of microvascular lesions and brain atrophy are associated with odor identification (OID) decline.

Methods

The association between structural MRI markers and OID decline was examined in participants from the SNAC-K MRI study who were free from dementia at baseline (n = 401, mean age = 70.2 years, 60% females). OID was repeatedly assessed over 15 years. Presence of lacunes, white matter hyperintensities (WMH), perivascular spaces (PVS), and lateral ventricular, hippocampal, amygdalar, and total gray matter (GM) volumes were assessed up to 6 years, concurrent with the first 6 years of olfactory assessments.

Results

Higher PVS count and lower hippocampal and GM volumes at baseline were associated with accelerated OID decline (pFWE  < 0.05). Longitudinally (n = 225), presence of lacunes at follow-up, faster WMH volume and PVS count increases, faster lateral ventricular enlargement, and faster hippocampal, amygdalar, and GM atrophy were associated with accelerated OID decline (p FWE < 0.05).

Conclusion

Olfactory decline is related to both increased cerebrovascular burden and accelerated brain atrophy over time.

Enlarged perivascular spaces correlate with blood-brain barrier leakage and cognitive impairment in Alzheimer's disease

BackgroundThe clinical significance of enlarged perivascular spaces (EPVS) in Alzheimer' s disease (AD) was ambiguous.ObjectiveTo investigate whether EPVS contribute to blood-brain barrier (BBB) leakage and cognition in AD.MethodsThe study included a total of 64 participants (26 healthy controls and 38 patients with AD). The evaluation of EPVS and BBB permeability was performed in specific anatomical locations: the centrum semiovale (CSO), basal ganglia, and hippocampus. The EPVS ratings were performed according to Potter's instructions. BBB permeability was evaluated using dynamic contrast-enhanced-MRI. The relationship between EPVS and global cognition (Mini-Mental State Examination and Montreal Cognitive Assessment), cognitive subdomains, and BBB permeability were examined in both groups. Finally, the relationship between CSO BBB permeability and cognition in AD patients was investigated.ResultsHigh-grade CSO EPVS was found associated with AD (OR: 3.40, 95% CI: 1.11-11.90, p = 0.04). In the AD group, a significant correlation was observed between high-grade CSO EPVS and lower MMSE score (r = -0.36, p = 0.03) and verbal fluency (r = -0.44, p = 0.01). High-grade CSO EPVS positively correlated with BBB leakage (r = 0.58, p < 0.001). The BBB permeability of CSO negatively correlated with verbal fluency (r = -0.52, p < 0.001) and attention (r = -0.40, p = 0.01).ConclusionsHigh-grade CSO EPVS is related to BBB leakage, which contributes to cognitive impairment in AD patients, especially verbal frequency. CSO EPVS can function as a convenient AD marker for intervention and therapy.

Emerging non-invasive MRI techniques for glymphatic system assessment in neurodegenerative disease

The discovery of the glymphatic system has revolutionized our understanding of brain physiology, particularly in waste clearance and fluid dynamics within the central nervous system. This pathway, essential for nutrient distribution and waste removal, operates predominantly during sleep and has been implicated in neurodegenerative diseases like Alzheimer's and Parkinson's. Recent advances in non-invasive MRI techniques, including diffusion tensor imaging along the perivascular space (DTI-ALPS), perivascular space (PVS) analysis, and free water (FW) indices, have improved our ability to study glymphatic function and its alterations in disease states. This review discusses the glymphatic system's ultrastructure, physiology, and the latest imaging methods to assess this critical pathway. We highlight how these non-invasive MRI techniques can enhance the understanding of glymphatic function in health and disease, with a focus on neurodegenerative conditions. By integrating insights from current research, this review underscores the diagnostic and therapeutic implications of glymphatic dysfunction. Understanding these mechanisms can pave the way for novel strategies to enhance waste clearance and improve neurological health, offering potential benefits for early diagnosis and intervention in neurodegenerative diseases.

Imaging markers of cerebral small vessel disease are associated with Alzheimer's disease: a systematic review and meta-analysis

Objective

This study aims to assess the correlation between cerebral small vessel disease (CSVD) imaging markers and the risk of Alzheimer's disease (AD) through a systematic review and meta-analysis.

Methods

In July 2024, two researchers independently conducted a thorough literature search across databases such as PubMed, Embase, Web of Science, and the Cochrane Library. The selected studies investigated the correlations between white matter hyperintensities (WMHs), cerebral microbleeds (CMBs), lacunar infarction (LI), and enlarged perivascular spaces (EPVS) and the risk of AD. The Newcastle-Ottawa Scale (NOS) was employed to assess the risk of bias in the included cohort and case-control studies.

Results

A total of 6,487 articles were identified, with 15 articles meeting the inclusion criteria. Pooled analyses showed that WMHs (HR: 1.38, 95% CI: 1.10-1.74, N = 7,661), CMBs (HR: 1.60, 95% CI: 1.07-2.40, N = 6,567), and EPVS (HR: 1.84, 95% CI: 1.24-2.72, N = 3,045) were associated with an increased risk of AD, with EPVS showing the strongest correlation. LI did not show a statistically significant association with an increased risk of AD (HR: 1.41, 95% CI: 0.98-2.01, N = 4,014).

Conclusion

WMHs, CMBs, and EPVS are associated with an elevated risk of AD, whereas LI is considered a potential risk factor. However, additional studies are required to determine the role of CSVD markers in AD progression.

Robust, fully-automated assessment of cerebral perivascular spaces and white matter lesions: a multicentre MRI longitudinal study of their evolution and association with risk of dementia and accelerated brain atrophy

BACKGROUND

Perivascular spaces (PVS) on brain MRI are surrogates for small parenchymal blood vessels and their perivascular compartment, and may relate to brain health. However, it is unknown whether PVS can predict dementia risk and brain atrophy trajectories in participants without dementia, as longitudinal studies on PVS are scarce and current methods for PVS assessment lack robustness and inter-scanner reproducibility.

METHODS

We developed a robust algorithm to automatically assess PVS count and size on clinical MRI, and investigated 1) their relationship with dementia risk and brain atrophy in participants without dementia, 2) their longitudinal evolution, and 3) their potential use as a screening tool in simulated clinical trials. We analysed 46,478 clinical measurements of cognitive functioning and 20,845 brain MRI scans from 10,004 participants (71.1 ± 9.7 years-old, 56.6% women) from three publicly available observational studies on ageing and dementia (the Alzheimer's Disease Neuroimaging Initiative, the National Alzheimer's Coordinating Centre database, and the Open Access Series of Imaging Studies). Clinical and MRI data collected between 2004 and 2022 were analysed with consistent methods, controlling for confounding factors, and combined using mixed-effects models.

FINDINGS

Our fully-automated method for PVS assessment showed excellent inter-scanner reproducibility (intraclass correlation coefficients >0.8). Fewer PVS and larger PVS diameter at baseline predicted higher dementia risk and accelerated brain atrophy. Longitudinal trajectories of PVS markers differed significantly in participants without dementia who converted to dementia compared with non-converters. In simulated placebo-controlled trials for treatments targeting cognitive decline, screening out participants at low risk of dementia based on our PVS markers enhanced the power of the trial independently of Alzheimer's disease biomarkers.

INTERPRETATION

These robust cerebrovascular markers predict dementia risk and brain atrophy and may improve risk-stratification of patients, potentially reducing cost and increasing throughput of clinical trials to combat dementia.

FUNDING

US National Institutes of Health.

Vascular Cognitive Impairment

OBJECTIVE

Vascular cognitive impairment is a major contributor to age-associated cognitive decline, both independently and as a contributor to mixed dementia syndromes. This article reviews the current understanding of how vascular dysfunction contributes to cognitive impairment and dementia risk in older individuals and includes updated diagnostic criteria and treatment recommendations.

LATEST DEVELOPMENTS

Clinical and research criteria have been evolving to more accurately determine the full prevalence of vascular cognitive impairment. The Boston Criteria version 2.0 for cerebral amyloid angiopathy now includes multiple punctate MRI T2 white matter hyperintensities and MR-visible perivascular spaces in addition to previously described T2* hemorrhagic signatures. MR-visible perivascular spaces are associated with both vascular cognitive impairment and Alzheimer disease, potentially linking cerebrovascular dysfunction to neurodegenerative disorders through its role in brain waste clearance. The American Heart Association's goal for cardiovascular health promotion, "Life's Essential 8," has been updated to include sleep health and acknowledges psychological well-being and social determinants of health as fundamental components necessary to achieve optimal cardiovascular health for all adults.

ESSENTIAL POINTS

Vascular cognitive impairment is a common and often underrecognized contributor to cognitive impairment in older individuals, with heterogeneous etiologies requiring individualized treatment strategies. Effective cerebrovascular disease risk factor modification starting in midlife is critical to reducing the risk of Alzheimer disease and related dementias, with the goal of preventing vascular brain injury and maintaining cognitive reserve in the presence of nonvascular age-related brain pathologies.

Cerebrovascular markers of WMH and infarcts in ADNI: A historical perspective and future directions

White matter hyperintensities (WMH) and infarcts found on magnetic resonance imaging (MR infarcts) are common biomarkers of cerebrovascular disease. In this review, we summarize the methods, publications, and conclusions stemming from the Alzheimer's Disease Neuroimaging Initiative (ADNI) related to these measures. We combine analysis of WMH and MR infarct data from across the three main ADNI cohorts with a review of existing literature discussing new methodologies and scientific findings derived from these data. Although ADNI inclusion criteria were designed to minimize vascular risk factors and disease, data across all the ADNI cohorts found consistent trends of increasing WMH volumes associated with advancing age, female sex, and cognitive impairment. ADNI, initially proposed as a study to investigate biomarkers of AD pathology, has also helped elucidate the impact of asymptomatic cerebrovascular brain injury on cognition within a cohort relatively free of vascular disease. Future ADNI work will emphasize additional vascular biomarkers. HIGHLIGHTS: White matter hyperintensities (WMHs) are common to advancing age and likely reflect brain vascular injury among older individuals. WMH and to a lesser extent, magnetic resonance (MR) infarcts, affect risk for transition to cognitive impairment. WMHs and MR infarcts are present, even among Alzheimer's Disease Neuroimaging Initiative (ADNI) participants highly selected to have Alzheimer's disease (AD) as the primary pathology. WMH burden in ADNI is greater among individuals with cognitive impairment and has been associated with AD neurodegenerative markers and cerebral amyloidosis. The negative additive effects of cerebrovascular disease appear present, even in select populations, and future biomarker work needs to further explore this relationship.

Higher burden of cerebral small vessel disease is associated with risk of incident stroke in community dwelling individuals

Background

Mild manifestations of individual cerebral small vessel disease (CSVD) markers are common and may not denote increased risk, but high CSVD burden identifies individuals at increased risk of stroke and dementia. Scores incorporating multiple individual CSVD markers may better identify a person's risk. We related a multi-marker CSVD score to risk of incident stroke and compared it with the Framingham Stroke Risk Profile (FSRP) in community-dwelling individuals.

Methods

Framingham Heart Study participants aged ≥55 years, free of stroke and dementia and with brain magnetic resonance imaging ratings of CSVD markers were included. A multi-marker CSVD score reflecting increasing CSVD burden was used, assigning one point each for presence of cerebral microbleeds, severe perivascular spaces, extensive white matter hyperintensities, covert brain infarcts, and cortical superficial siderosis. Multivariable Cox proportional hazards regression analyses were used to relate CSVD score to incident stroke.

Results

Among 1,154 participants (46% male, mean age 70.9±8.7), 92 (8%) developed stroke over a median follow-up of 8.6 years (Q1-Q3: 5.1-12.5). In models adjusting for age, sex, time interval between clinic exam and MRI, FHS cohort, and FSRP, those with three or more markers had increased risk of stroke (HR: 2.62; 95% CI: 1.17-5.88). In comparison, a 5-percent increase in FSRP was also associated with increased risk (aHR: 1.16; 95% CI: 1.04-1.29). The FSRP and CSVD score had similar model discrimination metrics.

Interpretation

Higher CSVD burden is associated with increased risk of stroke, beyond the effect explained by risk factors in the FSRP. These findings support consideration of CSVD burden to identify risk of stroke in community-dwelling individuals for early implementation of preventive strategies.

Nasal lymphatic obstruction of CSF drainage as a possible cause of Alzheimer's disease and dementia

Alzheimer's disease, the most common form of dementia among older adults, slowly destroys memory and thinking skills. In recent years, scientists have made tremendous progress in understanding Alzheimer's disease, still, they do not yet fully understand what causes the disease. This article proposes a novel etiology for Alzheimer's disease. Our hypothesis developed from a review of nuclear medicine scans, in which the authors observed a significant increase in nasal turbinate vasodilation and blood pooling in patients with hypertension, sleep apnea, diabetes and/or obesity, all risk factors for Alzheimer's disease. The authors propose that nasal turbinate vasodilation and resultant blood pooling lead to the obstruction of normal nasal lymphatic clearance of cerebrospinal fluid and its waste products from the brain. The nasal turbinate vasodilation, due to increased parasympathetic activity, occurs alongside the well-established increased sympathetic activity of the cardiovascular system as seen in patients with hypertension. The increased parasympathetic activity is likely due to an autonomic imbalance secondary to the increase in worldwide consumption of highly processed food associated with dysregulation of the glucose regulatory system. The authors' hypothesis offers a novel mechanism and a new paradigm for the etiology of Alzheimer's disease and helps explain the rapid worldwide rise in the disease and other dementias which are expected to double in the next 20 years. This new paradigm provides compelling evidence for the modulation of the parasympathetic nervous system as a novel treatment strategy for Alzheimer's disease and other degenerative brain diseases, specifically targeting nasal turbinate lymphatic flow.

Development and validation of a multimodal deep learning framework for vascular cognitive impairment diagnosis

Cerebrovascular disease (CVD) is the second leading cause of dementia worldwide. The accurate detection of vascular cognitive impairment (VCI) in CVD patients remains an unresolved challenge. We collected the clinical non-imaging data and neuroimaging data from 307 subjects with CVD. Using these data, we developed a multimodal deep learning framework that combined the vision transformer and extreme gradient boosting algorithms. The final hybrid model within the framework included only two neuroimaging features and six clinical features, demonstrating robust performance across both internal and external datasets. Furthermore, the diagnostic performance of our model on a specific dataset was demonstrated to be comparable to that of expert clinicians. Notably, our model can identify the brain regions and clinical features that significantly contribute to the VCI diagnosis, thereby enhancing transparency and interpretability. We developed an accurate and explainable clinical decision support tool to identify the presence of VCI in patients with CVD.

Repetitive Head Impacts and Perivascular Space Volume in Former American Football Players

Importance

Exposure to repetitive head impacts (RHI) is associated with increased risk for neurodegeneration. Accumulation of toxic proteins due to impaired brain clearance is suspected to play a role.

Objective

To investigate whether perivascular space (PVS) volume is associated with lifetime exposure to RHI in individuals at risk for RHI-associated neurodegeneration.

Design, Setting, and Participants

This cross-sectional study was part of the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy (DIAGNOSE CTE) Research Project, a 7-year multicenter study consisting of 4 US study sites. Data were collected from September 2016 to February 2020 and analyses were performed between May 2021 and October 2023. After controlling for magnetic resonance image (MRI) and processing quality, former American football players and unexposed asymptomatic control participants were included in analyses.

Exposure

Prior exposure to RHI while participating in American football was estimated using the 3 cumulative head impact indices (CHII-G, linear acceleration; CHII-R, rotational acceleration; and CHII, number of head impacts).

Main Outcomes and Measures

Individual PVS volume was calculated in the white matter of structural MRI. Cognitive impairment was based on neuropsychological assessment. Linear regression models were used to assess associations of PVS volume with neuropsychological assessments in former American football players. All analyses were adjusted for confounders associated with PVS volume.

Results

Analyses included 224 participants (median [IQR] age, 57 [51-65] years), with 170 male former football players (114 former professional athletes, 56 former collegiate athletes) and 54 male unexposed control participants. Former football players had larger PVS volume compared with the unexposed group (mean difference, 0.28 [95% CI, 0.00-0.56]; P = .05). Within the football group, PVS volume was associated with higher CHII-R (β = 2.71 × 10-8 [95% CI, 0.50 × 10-8 to 4.93 × 10-8]; P = .03) and CHII-G (β = 2.24 × 10-6 [95% CI, 0.35 × 10-6 to 4.13 × 10-6]; P = .03). Larger PVS volume was also associated with worse performance on cognitive functioning in former American football players (β = -0.74 [95% CI, -1.35 to -0.13]; P = .04).

Conclusions and Relevance

These findings suggest that impaired perivascular brain clearance, as indicated by larger PVS volume, may contribute to the association observed between RHI exposure and neurodegeneration.

Augmentation of perivascular space visualization in basal ganglia and white matter hyperintensity lesion is a meaningful finding for subsequent cognitive decline

BACKGROUND

Cerebral small vessel disease (CSVD) causes cognitive decline and perivascular space enlargement is one of the image markers for CSVD.

PURPOSE

To search for clinical significance in the time-course augmentation of perivascular space in basal ganglia (BG-PVS) for cognitive decline.

MATERIAL AND METHODS

This study population included 179 participants from a community-based cohort, aged 70 years at baseline. They had undergone magnetic resonance imaging (MRI) studies two or three times between 2000 and 2008. Based on the severity of BG-PVS or white matter hyperintensity lesions (WMHL) in 2000, the participants were divided into low-grade or high-grade groups, respectively. In addition, their time-course augmentation was evaluated, and we created a categorical BG-PVS WMHL change score based on their augmentation (1 = neither, 2 = BG-PVS augmentation only, 3 = WMHL augmentation only, 4 = both). Cognitive function was assessed based on the Mini-Mental State Examination (MMSE); the change was defined as the difference between scores in 2000 and 2008. We used simple or multiple regression analysis for MMSE score change according to MRI findings and clinical characteristics that were probably related to cognitive decline.

RESULTS

In univariate analysis, MMSE score change was negatively associated with BG-PVS high grade at baseline and BG-PVS WMHL change score 4; this remained significant in multivariate analysis. In the final model based on the Akaike Information Criterion, BG-PVS WMHL change score 4 was associated with a 3.3-point decline in subsequent MMSE score.

CONCLUSIONS

This study suggested that augmentation in both BG-PVS and WMHL was associated with subsequent cognitive decline.

Relationship of Perivascular Space Markers With Incident Dementia in Cerebral Small Vessel Disease

BACKGROUND

Recent studies, using diffusion tensor image analysis along the perivascular space (DTI-ALPS), suggest impaired perivascular space (PVS) function in cerebral small vessel disease, but they were cross-sectional, making inferences on causality difficult. We determined associations between impaired PVS, measured using DTI-ALPS and PVS volume, and cognition and incident dementia.

METHODS

In patients with lacunar stroke and confluent white matter hyperintensities, without dementia at baseline, recruited prospectively in a single center, magnetic resonance imaging was performed annually for 3 years, and cognitive assessments, including global, memory, executive function, and processing speed, were performed annually for 5 years. We determined associations between DTI-ALPS and PVS volume with cerebral small vessel disease imaging markers (white matter hyperintensity volume, lacunes, and microbleeds) at baseline and with changes in imaging markers. We determined whether DTI-ALPS and PVS volume at baseline and change over 3 years predicted incident dementia. Analyses were controlled for conventional diffusion tensor image metrics using 2 markers (median mean diffusivity [MD] and peak width of skeletonized MD) and adjusted for age, sex, and vascular risk factors.

RESULTS

A total of 120 patients, mean age 70.0 years and 65.0% male, were included. DTI-ALPS declined over 3 years, while no change in PVS volume was found. Neither DTI-ALPS nor PVS volume was associated with cerebral small vessel disease imaging marker progression. Baseline DTI-ALPS was associated with changes in global cognition (β=0.142, P=0.032), executive function (β=0.287, P=0.027), and long-term memory (β=0.228, P=0.027). Higher DTI-ALPS at baseline predicted a lower risk of dementia (hazard ratio, 0.328 [0.183-0.588]; P<0.001), and this remained significant after including median MD as a covariate (hazard ratio, 0.290 [0.139-0.602]; P<0.001). Change in DTI-ALPS predicted dementia conversion (hazard ratio, 0.630 [0.428-0.964]; P=0.048), but when peak width of skeletonized MD and median MD were entered as covariates, the association was not significant. There was no association between baseline PVS volume, or PVS change over 3 years, and conversion to dementia.

CONCLUSIONS

DTI-ALPS predicts future dementia risk in patients with lacunar strokes and confluent white matter hyperintensities. However, the weakening of the association between change in DTI-ALPS and incident dementia after controlling for peak width of skeletonized MD and median MD suggests part of the signal may represent conventional diffusion tensor image metrics. PVS volume is not a predictor of future dementia risk.

Relation of MRI-Visible Perivascular Spaces and Other MRI Markers of Cerebral Small Vessel Disease

Perivascular spaces (PVS) visible on brain MRI signal cerebral small vessel disease (CSVD). The coexistence of PVS with other CSVD manifestations likely increases the risk of adverse neurological outcomes. We related PVS to other CSVD manifestations and brain volumes that are markers of vascular brain injury and neurodegeneration. Framingham Heart Study (FHS) participants with CSVD ratings on brain MRI were included. PVS were rated in the basal ganglia (BG) and centrum semiovale (CSO) into grades I-IV and a category reflecting high burden in single or mixed CSO-BG regions. We related PVS to covert brain infarcts (CBI), white matter hyperintensities (WMH), cerebral microbleeds (CMB), total brain, hippocampal, and cortical gray matter volumes using adjusted multivariable regression analyses. In 2454 participants (mean age 54 ± 12 years), we observed that higher PVS burden in both BG and CSO was related to CMB in lobar and deep brain regions and increased WMH. Greater CSO PVS burden was associated with decreased total cortical gray volumes. PVS are associated with ischemic markers of CSVD and neurodegeneration markers. Further studies should elucidate the causality between PVS and other CSVD manifestations.

Association between enlarged perivascular spaces and cerebrospinal fluid aquaporin-4 and tau levels: report from a memory clinic

Background

Perivascular spaces (PVS) are fluid-filled compartments that dilate in response to many different conditions. A high burden of enlarged PVS (EPVS) in the centrum semiovale (CSO) has been linked to neurodegeneration. Moreover, an increase in cerebrospinal fluid (CSF) levels of aquaporin-4 (AQP4), a water channel expressed on PVS-bounding astrocytes, has been described in patients with neurodegenerative dementia. Our aim was to investigate the relationship between neurodegenerative diseases and two putative glymphatic system biomarkers: AQP4 and EPVS.

Methods

We included 70 individuals, 54 patients with neurodegenerative diseases and 16 subjects with non-degenerative conditions. EPVS were visually quantified on MRI-scans applying Paradise's scale. All subjects underwent lumbar puncture for the measurement of AQP4 levels in the cerebrospinal fluid (CSF). CSF levels of amyloid-β-1-42, phosphorylated and total tau (tTau) were also measured. Linear regression analyses were adjusted for age, sex, education and disease duration, after excluding outliers.

Results

Cerebrospinal fluid (CSF)-AQP4 levels were independent predictors of total (β = 0.28, standard error [SE] = 0.08, p = 0.001), basal ganglia (β = 0.20, SE = 0.08, p = 0.009) and centrum semiovale EPVS (β = 0.37, SE = 0.12, p = 0.003). tTau levels predicted CSO-EPVS (β = 0.30, SE = 0.15, p = 0.046). Moreover, increased levels of AQP4 were strongly associated with higher levels of tTau in the CSF (β = 0.35, SE = 0.13, p = 0.008).

Conclusion

We provide evidence that CSO-EPVS and CSF-AQP4 might be clinically meaningful biomarkers of glymphatic dysfunction and associated neurodegeneration.

Early therapeutic effects of an Angiopoietin-1 mimetic peptide in middle-aged rats with vascular dementia

Background

Vascular Dementia (VaD) refers to dementia caused by cerebrovascular disease and/or reduced blood flow to the brain and is the second most common form of dementia after Alzheimer's disease. We previously found that in middle-aged rats subjected to a multiple microinfarction (MMI) model of VaD, treatment with AV-001, a Tie2 receptor agonist, significantly improves short-term memory, long-term memory, as well as improves preference for social novelty compared to control MMI rats. In this study, we tested the early therapeutic effects of AV-001 on inflammation and glymphatic function in rats subjected to VaD.

Methods

Male, middle-aged Wistar rats (10-12 m), subjected to MMI, were randomly assigned to MMI and MMI + AV-001 treatment groups. A sham group was included as reference group. MMI was induced by injecting 800 ± 200, 70-100 μm sized, cholesterol crystals into the internal carotid artery. Animals were treated with AV-001 (1 μg/Kg, i.p.) once daily starting at 24 h after MMI. At 14 days after MMI, inflammatory factor expression was evaluated in cerebrospinal fluid (CSF) and brain. Immunostaining was used to evaluate white matter integrity, perivascular space (PVS) and perivascular Aquaporin-4 (AQP4) expression in the brain. An additional set of rats were prepared to test glymphatic function. At 14 days after MMI, 50 μL of 1% Tetramethylrhodamine (3 kD) and FITC conjugated dextran (500 kD) at 1:1 ratio were injected into the CSF. Rats (4-6/group/time point) were sacrificed at 30 min, 3 h, and 6 h from the start of tracer infusion, and brain coronal sections were imaged using a Laser scanning confocal microscope to evaluate tracer intensities in the brain.

Result

Treatment of MMI with AV-001 significantly improves white matter integrity in the corpus callosum at 14 days after MMI. MMI induces significant dilation of the PVS, reduces AQP4 expression and impairs glymphatic function compared to Sham rats. AV-001 treatment significantly reduces PVS, increases perivascular AQP4 expression and improves glymphatic function compared to MMI rats. MMI significantly increases, while AV-001 significantly decreases the expression of inflammatory factors (tumor necrosis factor-α (TNF-α), chemokine ligand 9) and anti-angiogenic factors (endostatin, plasminogen activator inhibitor-1, P-selectin) in CSF. MMI significantly increases, while AV-001 significantly reduces brain tissue expression of endostatin, thrombin, TNF-α, PAI-1, CXCL9, and interleukin-6 (IL-6).

Conclusion

AV-001 treatment of MMI significantly reduces PVS dilation and increases perivascular AQP4 expression which may contribute to improved glymphatic function compared to MMI rats. AV-001 treatment significantly reduces inflammatory factor expression in the CSF and brain which may contribute to AV-001 treatment induced improvement in white matter integrity and cognitive function.

Association of MRI Visible Perivascular Spaces and Neurofilament Light Chain: The Framingham Heart Study

BACKGROUND

Neurofilament light chain (NfL) is a marker of neuronal injury. Perivascular spaces (PVS) visible on magnetic resonance imaging (MRI) represent cerebral small vessel disease (CSVD) but their role as markers of neuronal injury needs further clarification.

OBJECTIVE

To relate PVS burden according to brain topography and plasma NfL.

METHODS

Framingham Heart Study (FHS) participants with brain MRI and NfL measurements were included. PVS were rated in the basal ganglia (BG) and centrum semiovale (CSO) using validated methods and categorized based on counts. A mixed region variable representing high burden PVS in either BG or CSO was assessed. Multivariable linear regression analyses were used to relate PVS burden to log-transformed NfL levels in models adjusted for age, sex, FHS cohort, time between MRI and clinic exam, and image view (model 1), vascular risk factors (model 2), and white matter hyperintensity volume, covert brain infarcts, and cerebral microbleeds (model 3).

RESULTS

Among 1,457 participants (68.1±8.5 years, 45% males), NfL levels increased with higher PVS burden. Multivariable analysis showed an association of high PVS burden strictly in BG with NfL (β= 0.117, 95% CI 0.014-0.221; p = 0.027), but attenuated in model 3. The associations were mainly in participants≥65 years (β= 0.122, 95% CI 0.015-0.229, p = 0.026), women (β= 0.156, 95% CI 0.024-0.288, p = 0.021), and APOE ɛ4 non-carriers (β= 0.140, 95% CI 0.017-0.263, p = 0.026).

CONCLUSIONS

The association of strictly BG high PVS burden with NfL suggests a role for PVS as markers of neuroaxonal injury, but our results are hypothesis generating and require further replication.

MRI Visible Perivascular Spaces and the Risk of Incident Mild Cognitive Impairment in a Community Sample

BACKGROUND

Magnetic resonance imaging (MRI) visible perivascular spaces (PVS) are associated with the risk of incident dementia but their association with the early stages of cognitive impairment remains equivocal.

OBJECTIVE

We examined the association between MRI visible PVS and the risk of incident mild cognitive impairment (MCI) in the community-based Framingham Heart Study (FHS).

METHODS

FHS participants aged at least 50 years free of stroke, cognitive impairment, and dementia at the time of MRI were included. PVS were rated according to severity in the basal ganglia and centrum semiovale (CSO) using established criteria. Cox regression analyses were used to relate PVS to incident MCI adjusted for demographic and cardiovascular variables.

RESULTS

The mean age of the sample (1,314 participants) at MRI was 68 years (SD, 9; 54% women). There were 263 cases of incident MCI over a median 7.4 years follow-up (max, 19.8 years). MCI risk increased with higher PVS severity in the CSO. Relative to persons with the lowest severity rating, persons with the highest severity rating in the CSO had a higher risk of incident MCI (hazard ratio [HR] = 2.55; 95% confidence interval [CI], 1.48-4.37; p = 0.0007). In secondary analysis, this association seemed stronger in women. Risk of incident MCI was nominally higher for participants with the highest severity grade of PVS in the basal ganglia, though not statistically significant relative to the lowest grade (HR = 2.19; 95% CI, 0.78-6.14; p = 0.14).

CONCLUSIONS

PVS burden in the CSO may be a risk marker for early cognitive impairment.

Clinical Features, Brain-Structure Changes, and Cognitive Impairment in Basal Ganglia Infarcts: A Pilot Study

Introduction

Stroke has been considered to raise the risk of dementia in several studies, but the relationship between brain structural changes and poststroke cognitive impairment (PSCI) is unclear.

Methods

In this study, 23 PSCI patients with basal ganglia infarcts after 2 weeks and 29 age-matched controls underwent magnetic resonance imaging measuring cortical thickness and volume changes, as well as neuropsychological tests. CI was derived from a performance score <1.5 standard deviations for normally distributed scores. We compared Z scores in different cognitive domains and cortical thickness and volumes in two groups. Multiple linear regressions were used to investigate the relationship between cortical thickness and volumes and neuropsychological tests.

Results

A majority of PSCI patients were in their 50s (55.19±8.52 years). PSCI patients exhibited significantly decreased Z scores in multiple domains, such as memory, language, visuomotor speed, and attention/executive function. The volumes of the middle posterior corpus callosum, middle anterior corpus callosum, and hippocampus in PSCI patients were markedly lower than controls. The thickness of the right inferior temporal cortex and insula were significantly smaller than controls. It found that the reduced right hippocampus was related to executive dysfunction. Hippocampus dysfunction may be involved in language impairment (p<0.05) in PSCI patients with basal ganglia infarcts.

Conclusion

These findings demonstrated that brain structure changed after ischemic stroke, and different gray-matter structural changes could lead to specific cognitive decline in PSCI patients with basal ganglia infarcts. Atrophy of the right hippocampus potentially serves as an imaging marker of early executive function of PSCI.