Regional White Matter Hyperintensities Research Articles

Impact of Systolic Blood Viscosity on Deep White Matter Hyperintensities in Patients With Acute Ischemic Stroke.

Elevated blood viscosity (BV), a critical determinant in blood rheology, is a contributing factor in cerebrovascular diseases. The specific influence of BV on small vessel disease burden remains unexplored. This study aims to examine the relationship between BV and regional white matter hyperintensity (WMH) volume in patients with acute ischemic stroke. We enrolled a cohort of 302 patients with acute ischemic stroke or transient ischemic attack who were admitted to a hospital within 7 days of symptom onset in this study. We measured whole BV using a scanning capillary-tube viscometer and categorized systolic blood viscosity into 3 groups based on established references. We quantified and normalized WMH volumes using automated localization and segmentation software by NEUROPHET Inc. We performed multivariable logistic regression analysis to assess the correlation between systolic BV and WMH. The mean subject age was 66.7±13.4 years, and 38.7% (n=117) of the participants were female. Among a total of 302 patients, patients with higher deep WMH volume (T3) were typically older and had an atrial fibrillation, strokes of cardioembolic or undetermined cause, elevated levels of C-reactive protein, diastolic blood viscosity and systolic BV. A multivariable adjustment revealed a significant association between high systolic BV and increased deep-WMH volume (odds ratio [OR], 2.636 [95% CI, 1.225-5.673]). Elevated systolic BV is more likely to be associated with deep WMH volume in patients with acute ischemic stroke or transient ischemic attack. These findings reveal novel therapeutic strategies focusing on blood rheology to enhance cerebral microcirculation in stroke management.

Impact of age and apolipoprotein E ε4 status on regional white matter hyperintensity volume and cognition in healthy aging.

White matter hyperintensity (WMH) volume is a neuroimaging marker of lesion load related to small vessel disease that has been associated with cognitive aging and Alzheimer's disease (AD) risk. The present study sought to examine whether regional WMH volume mediates the relationship between APOE ε4 status, a strong genetic risk factor for AD, and cognition and if this association is moderated by age group differences within a sample of 187 healthy older adults (APOE ε4 status [carrier/non-carrier] = 56/131). After we controlled for sex, education, and vascular risk factors, ANCOVA analyses revealed significant age group by APOE ε4 status interactions for right parietal and left temporal WMH volumes. Within the young-old group (50-69 years), ε4 carriers had greater right parietal and left temporal WMH volumes than non-carriers. However, in the old-old group (70-89 years), right parietal and left temporal WMH volumes were comparable across APOE ε4 groups. Further, within ε4 non-carriers, old-old adults had greater right parietal and left temporal WMH volumes than young-old adults, but there were no significant differences across age groups in ε4 carriers. Follow-up moderated mediation analyses revealed that, in the young-old, but not the old-old group, there were significant indirect effects of ε4 status on memory and executive functions through left temporal WMH volume. These findings suggest that, among healthy young-old adults, increased left temporal WMH volume, in the context of the ε4 allele, may represent an early marker of cognitive aging with the potential to lead to greater risk for AD.

Abstract 126: Connectome Gradient Dysfunction Contributes to White Matter Hyperintensity-Related Cognitive Decline

Introduction: Although White matter hyperintensity (WMH) is closely associated with cognitive decline, the precise neurobiological mechanisms underlying this relationship are not fully elucidated. Connectome studies have identified a primary-to-transmodal gradient in functional brain networks that support the spectrum from sensation to cognition. However, whether this gradient structure is altered as WMH progresses and how this alteration is associated with WMH-related cognitive decline remain unknown. Methods: A total of 758 individuals with WMH were enrolled from two medical centers and one community. All these participants completed cognitive assessment and resting-state functional MRI (rs-fMRI). The functional connectome gradient was reconstructed based on rs-fMRI by using a gradient decomposition framework. Interrelations amongst regional WMH, functional gradient measures, and specific cognitive domains were explored. Results: The larger WMH volume, the narrower range ( r = -0.099, p = 0.006) and smaller variance ( r = -0.121, p < 0.001) of the primary-to-transmodal gradient, as well as the poorer executive function ( r = -0.135, p = 0.001) and information processing speed ( r = -0.224, p = 0.001). A narrower range ( r = 0.131, p = 0.001) and smaller variance ( r = 0.136, p = 0.001) of the primary-to-transmodal gradient corresponded to poorer executive function. In particular, the relationship between frontal/occipital WMH and executive function was partly mediated by gradient range/variance of the primary-to-transmodal gradient (the 95% confidence interval did not contain the value 0). WMH-related gradient alterations were associated with gene expression levels involved in the G protein-coupled receptor (GPCR) signaling pathway (FDR q -value < 10 -4 ) and chemical synaptic transmission (FDR q -value < 10 -6 ). Discussion: We found that the primary-to-transmodal gradient dysfunction contributes to WMH-related cognitive decline. The detrimental effect of frontal/occipital WMH on executive function was mediated by decreased differentiation of the connectivity pattern between the primary and transmodal areas. The neurobiological mechanisms may be related to the GPCR signaling pathway and chemical synaptic transmission.

Linking Dementia Pathology and Alteration in Brain Activation to Complex Daily Functional Decline During the Preclinical Dementia Stages: Protocol for a Prospective Observational Cohort Study.

Progressive difficulty in performing everyday functional activities is a key diagnostic feature of dementia syndromes. However, not much is known about the neural signature of functional decline, particularly during the very early stages of dementia. Early intervention before overt impairment is observed offers the best hope of reducing the burdens of Alzheimer disease (AD) and other dementias. However, to justify early intervention, those at risk need to be detected earlier and more accurately. The decline in complex daily function (CdF) such as managing medications has been reported to precede impairment in basic activities of daily living (eg, eating and dressing). Our goal is to establish the neural signature of decline in CdF during the preclinical dementia period. Gait is central to many CdF and community-based activities. Hence, to elucidate the neural signature of CdF, we validated a novel electroencephalographic approach to measuring gait-related brain activation while participants perform complex gait-based functional tasks. We hypothesize that dementia-related pathology during the preclinical period activates a unique gait-related electroencephalographic (grEEG) pattern that predicts a subsequent decline in CdF. We provide preliminary findings showing that older adults reporting CdF limitations can be characterized by a unique gait-related neural signature: weaker sensorimotor and stronger motor control activation. This subsample also had smaller brain volume and white matter hyperintensities in regions affected early by dementia and engaged in less physical exercise. We propose a prospective observational cohort study in cognitively unimpaired older adults with and without subclinical AD (plasma amyloid-β) and vascular (white matter hyperintensities) pathologies. We aim to (1) establish the unique grEEG activation as the neural signature and predictor of decline in CdF during the preclinical dementia period; (2) determine associations between dementia-related pathologies and incidence of the neural signature of CdF; and (3) establish associations between a dementia risk factor, physical inactivity, and the neural signature of CdF. By establishing the clinical relevance and biological basis of the neural signature of CdF decline, we aim to improve prediction during the preclinical stages of ADs and other dementias. Our approach has important research and translational implications because grEEG protocols are relatively inexpensive and portable, and predicting CdF decline may have real-world benefits. DERR1-10.2196/56726.

Association between white matter hyperintensities and altered cerebral blood flow in maintenance hemodialysis patients: a longitudinal study

ObjectivesTo explore changes in cerebral blood flow (CBF) and white matter in hemodialysis patients.MethodsThirty-three hemodialysis patients who underwent two brain MRI at an interval of three years and 33 age- and sex-matched healthy controls (HC) underwent structural and arterial spin-labeling MRI examinations. Intergroup differences in CBF in the gray matter, white matter, and whole matter, and regional white matter hyperintensities (WMH) were analyzed. Based on the changes in CBF between the baseline and follow-up groups, the hemodialysis patients were divided into two subgroups: an increased CBF group and a decreased CBF group. Differences in CBF and WMH between the subgroups and HC were analyzed.ResultsPatients undergoing hemodialysis exhibited increased cerebral watershed (CW) WMH, deep WMH, and periventricular WMH (P < 0.01). The CBF of patients with decreased CBF was higher than that of HC at baseline (,P < 0.01) and lower than that of HC at follow-up (P < 0.01). Compared with the increased CBF group, obvious development of deep WMH was found in the decreased CBF group for the gray matter, white matter, and whole matter (P < 0.01).ConclusionsWMH in hemodialysis patients were distributed in the deep white matter, periventricular white matter and CW, and progressed with the extension of hemodialysis duration. CBF in hemodialysis patients could manifest as both increased and decreased, and WMH in patients with decreased CBF developed severely with prolongation of hemodialysis duration.Advances in knowledgeThese findings provide a basis for exploring neuropathological changes of hemodialysis patients.

A pilot study of longitudinal changes in neurocognition, white matter hyperintensities, and cortical thickness in atrial fibrillation patients following catheter ablation vs medical management

BackgroundCerebral microembolization and atrophy complicate atrial fibrillation (AF). ObjectivesWe aimed to compare changes in neuroimaging findings between AF patients treated with catheter ablation and those treated with medical therapy. MethodsIn this pilot study, we evaluated differences in the change in regional white matter hyperintensity burden (WMHb) and cognitive function from baseline to 6-weeks and 1-year in patients treated with AF ablation (ABL, n=12) and patients treated with medical management alone (MM, n=11). Change in cortical thickness in Alzheimer’s Disease (AD)-risk, aging-associated or shared AD-risk/aging regions was also compared between groups. ResultsThe mean age was 69.7±5.0, 78% of patients were male, 39% had persistent AF, and all received oral anticoagulation. There were no significant differences between groups in the change in cognitive function. At 6-weeks, there were no significant differences in periventricular WMHb changes between groups (0.00 vs. 0.04; p=0.12), but changes in attention/concentration were inversely correlated with periventricular (p=0.01) and total WMHb (p=0.03). MM patients demonstrated significantly greater cortical thinning in AD-risk regions from baseline to 1-year (p=0.003). ConclusionsAF patients who underwent ablation demonstrated less cortical thinning in regions associated with AD risk than patients treated with medical therapy. Larger, prospective studies are needed to better understand the relationship between AF therapies and the development of cognitive decline.

The Association of Upper Airway Anatomy with Brain Structure: The Multi-Ethnic Study of Atherosclerosis.

Sleep apnea, affecting an estimated 1 in 4 American adults, has been reported to be associated with both brain structural abnormality and impaired cognitive function. Obstructive sleep apnea is known to be affected by upper airway anatomy. To better understand the contribution of upper airway anatomy to pathways linking sleep apnea with impaired cognitive function, we investigated the association of upper airway anatomy with structural brain abnormalities. Based in the Multi-Ethnic Study of Atherosclerosis, a longitudinal cohort study of community-dwelling adults, a comprehensive sleep study and an MRI of the upper airway and brain were performed on 578 participants. Machine learning models were used to select from 74 upper airway measures those measures most associated with selected regional brain volumes and white matter hyperintensity volume. Linear regression assessed associations between the selected upper airway measures, sleep measures, and brain structure. Maxillary divergence was positively associated with hippocampus volume, and mandible length was negatively associated with total white and gray matter volume. Both coefficients were small (coefficients per standard deviation 0.063 mL, p = 0.04, and - 7.0 mL, p < 0.001 respectively), and not affected by adjustment for sleep study measures. Self-reported snoring >2 times per week was associated with larger hippocampus volume (coefficient 0.164 mL, p = 0.007), and higher percentage of time in the N3 sleep stage was associated with larger total white and gray matter volume (4.8 mL, p = 0.004). Despite associations of two upper airway anatomy measures with brain volume, the evidence did not suggest that these upper airway and brain structure associations were acting primarily through the pathway of sleep disturbance.

Investigating the relationship between sleep disturbances and white matter hyperintensities in older adults on the Alzheimer's disease spectrum.

While studies report that sleep disturbance can have negative effects on brain vasculature, its impact on cerebrovascular diseases such as white matter hyperintensities (WMHs) in beta-amyloid-positive older adults remains unexplored. Sleep disturbance, WMH burden, and cognition in normal controls (NCs), and individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD), were examined at baseline and longitudinally. A total of 912 amyloid-positive participants were included (198 NC, 504 MCI, and 210 AD). Individuals with AD reported more sleep disturbances than NC and MCI participants. Those with sleep disturbances had more WMHs than those without sleep disturbances in the AD group. Mediation analysis revealed an effect of regional WMH burden on the relationship between sleep disturbance and future cognition. These results suggest that WMH burden and sleep disturbance increase from aging to AD. Sleep disturbance decreases cognition through increases in WMH burden. Improved sleep could mitigate the impact of WMH accumulation and cognitive decline.

Regional White Matter Hyperintensities are Associated with Diminished Blood Flow and Microstructure in Middle Age

AbstractBackgroundWhite matter hyperintensities (WMH) are areas of increased signal visualized on T2‐weighted FLAIR magnetic resonance imaging (MRI), thought to reflect macrostructural damage due to small vessel cerebrovascular disease. Previous work established an association of WMH severity, particularly in posterior regions, with risk and progression of AD in late onset and genetic forms of AD, suggesting a vascular component to disease pathogenesis and course. Examination of the emergence and correlates of cerebrovascular changes in middle age, a critical time when vascular risk appears to be most penetrant, can give insight into mechanisms linking vascular brain injury and risk for AD. In the current study, we examined the association of cerebral blood flow (CBF) and white matter microstructure with total and regional WMH volume in middle‐aged, community dwelling adults.MethodFour hundred and ninety‐two middle‐aged participants (55+/‐11 age = 28 ‐85 years) from the community‐based Offspring Study of Mechanisms for Racial Disparities in Alzheimer’s Disease received multi‐modal MRI scanning. Regional WMH volumes were derived with in‐house software that labeled clusters of voxels within a hyperintense intensity distribution. Pulsed arterial spin labeling (PASL) sequences were processed to quantify CBF. Fractional anisotropy (FA) maps were obtained from diffusion weighted data. Total and regional WMH volumes were used as predictors for whole brain voxel‐wise correlation analyses in separate models for CBF and FA.ResultThere were negative associations between WMH volume and CBF in frontal, parietal, and occipital regions. Higher white matter hyperintensity volume was associated with lower FA, particularly in the periventricular region.ConclusionWe found associations of increased WMH volume with diminished blood flow and white matter microstructure. Future studies are needed to explain the relationship between these changes and the risk of cognitive impairment in middle aged adults and risk for AD.

Artificial intelligence reveals brain aging patterns in 27,402 individuals without diagnosed cognitive impairment that are linked to genetics, biomedical measures, and cognitive decline

AbstractBackgroundUnderstanding heterogeneity of structural brain changes in aging may provide insights into susceptibility to neurodegenerative diseases. We characterize the genetics underlying brain structural heterogeneity within cognitively unimpaired (CU) individuals using data‐driven machine learning applied to a diverse dataset of 27,402 individuals from 11 neuroimaging studies from the iSTAGING consortium.MethodStructural brain morphologic patterns of CU individuals were independently examined in four decade‐long intervals spanning ages 45 to 85. Within each interval, Smile‐GAN (Yang et al., 2021) was trained on baseline anatomic and white matter hyperintensity (WMH) volumes. Smile‐GAN probability scores were used as phenotypes in genome‐wide association studies (GWAS). Specifically, we performed multiple linear regressions controlling for confounders (e.g., age) via Plink (Purcell et al., 2007). We observed longitudinal clustering stability across decades, so individuals from adjacent age groups were combined into broader age groups ([45,65), [65,85)) due to the large sample requirement of GWAS. Genomic loci, represented by the top leading single nucleotide polymorphisms (SNPs), were defined considering linkage disequilibrium. We investigated associations of SNPs with clinical traits and mapped them to genes using the GWAS Catalog (Buniello et al., 2019).ResultThree structural brain aging patterns, relative to resilient agers (A0), consistent across decades, emerged: A1, or ‘typical’ aging with low atrophy and WMHs, and two ‘advanced’ aging patterns, one showing elevated WMHs and modest atrophy (A2) and the other displaying severe, widespread atrophy and moderate WMH load (A3) (Figure 1). GWAS discovered eight and six genomic loci in [45,65) and [65,85) age groups, respectively (Table 1, Figure 2). The lead SNPs for A1 and A2 were previously associated with several cardiometabolic risk factors, WMHs, and regional brain volumes. Interestingly, rs4843552, previously associated with white matter microstructure and regional brain volumes, showed opposite effects for A1 (protection) and A2 (risk), consistent with the neuroimaging patterns. WDR41 in A3 group was previously associated with the age of Alzheimer’s disease onset (Herold et al., 2016).ConclusionReproducible neuroimaging patterns defined by regional atrophy and WMH burden were identified across CU individuals and demonstrated unique genetics. Further research is needed to elucidate the neuropathological pathways that mediate these relationships.

Higher baseline cerebrospinal fluid platelet‐derived growth factor receptor‐β levels are associated with slower reductions in longitudinal cerebral blood flow among cognitively unimpaired individuals

AbstractBackgroundCerebrospinal fluid (CSF) platelet‐derived growth factor receptor‐β (PDGFR‐β) is an emerging biomarker hypothesized to reflect pericyte damage. CSF PDGFR‐β levels are increased in Alzheimer’s disease (AD), but it is unknown if pericyte injury contributes to cerebrovascular changes common in AD. We examined if PDGFR‐β relates to changes in cerebral blood flow (CBF) and white matter injury in older adults.MethodVanderbilt Memory and Aging Project participants (n = 152, baseline age 73±7 years, 43% mild cognitive impairment [MCI]) underwent baseline lumbar puncture and serial brain MRI over a 7‐year (5.5±2.3) follow‐up period. CSF PDGFR‐β concentrated was measured by immunoassay. MRI included pseudo‐continuous arterial spin‐labeling to quantify CBF, T2‐FLAIR to quantify white matter hyperintensities (WMHs), and diffusion tensor imaging (DTI) to quantify white matter microstructural integrity. Ordinary least squares regression and linear mixed‐effects models related baseline CSF PDGFR‐β to baseline and longitudinal whole brain and regional CBF, WMH, and DTI metrics, adjusting for baseline demographic variables, modified Framingham Stroke Risk Profile, cognitive status, apolipoprotein‐ε4 status, and regional tissue volume. Longitudinal models adjusted for follow‐up time. Follow‐up models tested a CSF PDGFR‐β x cognitive status interaction.ResultIn main models, higher CSF PDGFR‐β levels were cross‐sectionally associated with lower mean diffusivity (indicating better microstructural integrity) in white matter tracts in the frontal, temporal, parietal, and occipital lobes (p‐values&lt;0.03) but were unrelated to WMHs (p‐values&gt;0.18). Models investigating associations with longitudinal white matter variables were null (p‐values&gt;0.35). CSF PDGFR‐β cross‐sectionally interacted with diagnosis on temporal lobe CBF, such that higher CSF PDGFR‐β related to higher CBF in MCI participants (p = 0.01). In longitudinal models, baseline CSF PDGFR‐β interacted with cognitive status on whole brain and occipital lobe CBF (p‐values&lt;0.04). Stratified models showed higher baseline CSF PDGFR‐β related slower reductions in longitudinal CBF in whole brain (p = 0.02), frontal (p = 0.04), temporal (p = 0.02), parietal (p = 0.01), and occipital lobes (p = 0.008) in cognitively unimpaired participants only.ConclusionAmong older adults, higher CSF PDGFR‐β levels are associated with better white matter integrity at study entry and predict slower reductions in longitudinal CBF among cognitively unimpaired individuals. Results suggest that higher PDGFR‐β levels may reflect subclinical vascular remodeling that provides protection to future cerebrovascular compromise.

White matter hyperintensity burden does not differentiate SuperAgers from average cognitive agers

AbstractBackgroundThe amount of white matter hyperintensity (WMH) found on T2‐weighted imaging has shown a strong relationship with age and is thought to be a marker of ischemia‐associated demyelination or secondary axonal degeneration associated with neurodegenerative disease. Previous healthy older aging studies have shown increased WMH are associated with poorer episodic memory performance and decreased volume of medial temporal lobe regions. Here, we examine if lower WMH are associated with a phenotype of successful cognitive aging, SuperAging. SuperAgers are participants over the age 80 with episodic memory at least as good as that of average middle‐aged adults.MethodWe quantified the WMH volume from T2‐FLAIR imaging with a pre‐trained Bayesian 3D U‐Net convolutional neural network in SuperAgers and cognitively healthy elderly controls (EC) of a similar age and education. All participants underwent the ADNI‐3 FLAIR on the same 3T Prisma MRI. WMH volume was square root transformed to account for the skewed distribution. A 2‐tail independent samples t‐test evaluated the difference in WMH volume between SuperAgers and EC. Additionally, we examined if there were differences within SA and EC groups by sex.Result46 SuperAgers (average age 86.3 ± 1.86; average years of education 16.9 ± 1.9) and 25 EC (average age 87.1 ± 5.17; average years of education 17.1 ± 3.1) met criteria and were included in the study. There was no significant difference in the volume of WMH between SuperAgers and ECs (t = 1.01, p = 0.32). Further, there was no significant difference in WMH by sex within the SuperAging group (t = 0.10, p = 0.92) or EC group (t = 0.82, p = 0.42).ConclusionResistance to the development of WMH, a cross‐sectional marker of cerebrovascular disease and demyelination, does not appear to be a strong discriminating factor in 80+ year‐olds with superior memory function compared to cognitively average agers. Future analyses will include longitudinal changes in WMH and examining regional WMH. Cognitive aging is associated with several underlying brain‐based etiologies, and SuperAging may be better explained by a more sophisticated multi‐modal approach.

Differences in pathology, brain atrophy, and WMHs across APOE subtypes

AbstractBackgroundThe apolipoprotein (APOE) e4 allele is a known risk factor for Alzheimer’s disease (AD), while the e2 allele is thought to be protective. As few studies have examined the relationship between brain pathologies, atrophy, and white matter hyperintensities (WMHs) and APOE status in those with the e2e4 genotype, we do so here.MethodsWe analyzed Alzheimer’s Disease Neuro Imaging participants that had APOE genotyping and at least one of the following metrics: regional WMH load (obtained using Dadar 2018); ventricle size, hippocampal (HC) and entorhinal cortex (EC) volume, amyloid level (i.e., AV‐45), and phosphorylated tau (pTau), all downloaded from LONI. Participants were divided into one of four APOE allele profiles (E4 = e4e4 or e3e4; E2 = e2e2 or e2e3; E3 = e3e3; or E24 = e2e4, Fig.1). Linear mixed effects models examined the relationship between APOE profiles and each pathology while controlling for age, sex, education, and diagnostic status.ResultsAt baseline (Fig.2), E4 exhibited increased pTau (p&lt;.001) compared to E2 and E3 and smaller HC and EC volumes than all other APOE profiles (p&lt;.01). The E24 group exhibited smaller ventricles than E3 and E4 (p&lt;.05). The E2 group exhibited less amyloid than all other APOE profiles (p&lt;.001), while E4 and E24 had more amyloid compared to E3 (p&lt;.001).Longitudinally (Fig.3), ventricular enlargement and HC atrophy significantly differed between all profiles (p&lt;.001). Furthermore, E2 was observed to have slower WMH accumulation compared to all other profiles (p&lt;.001), while E4 exhibited faster accumulation compared to E3 (p&lt;.001). The E4 group exhibited increased EC atrophy compared to E3 and E2 (p&lt;.001), and E24 exhibited more atrophy than E2 (p = .015). Amyloid increased faster in the E4 group compared to E3 and E2 (p&lt;.001), while E2 amyloid progressed slower than E3 (p = .005).ConclusionsAPOE E4 positivity is associated with increased baseline and greater accumulation of pathologies and rates of neurodegeneration. APOE E2 positivity is associated with reduced pathology burden (i.e., WMH and amyloid) and less neurodegeneration as measured by ventricle size and hippocampal and entorhinal cortex volume over time. APOE E2E4 is similar to E4 (i.e., increased neurodegeneration and pathology burden) but with a slightly slower rate of change.

A Twin Analysis of AD Brain Signatures and Abnormal White Matter

AbstractBackgroundAlzheimer’s disease (AD) and vascular disease frequently co‐occur and may interact additively or synergistically on risk for cognitive decline, though the degree of shared overlap between these pathologies remains unclear. Our group has demonstrated the utility of AD signatures, or composite MRI metrics in brain regions associated with AD pathology, for prediction of AD‐related changes beginning in midlife. Our novel signature based on gray matter mean diffusivity (MD) aided 12‐year prediction of incident mild cognitive impairment among cognitively unimpaired adults in their 50s, captured unique phenotypic and genetic variance not otherwise explained by an AD signature based on cortical thickness/volume or general brain aging, and robustly predicted thickness/volume signatures over a decade later. Here, we leveraged twin data from the Vietnam Era Twin Study of Aging (VETSA) to delineate shared and unique genetic and environmental influences on two AD signatures and white matter hyperintensities (WMHs), which have been consistently linked to vascular origin.MethodParticipants were 512 men from the VETSA (age = 67.52, SD = 2.60). Our validated thickness/volume signature, novel MD signature based on the same brain regions as the thickness/volume signature, and WMH volume were used in biometrical twin analyses to examine their phenotypic, genetic, and environmental relationships. We adjusted each AD signature for an MRI‐based measure of brain age to detect associations with WMH that were specific to AD‐related brain regions versus general brain aging. We also examined regional WMH parcellations.ResultPhenotypic and genetic correlations demonstrated significant associations between the MD signature and WMH (rp = 0.26 [95% CI: 0.15, 0.36]; rg = 0.34 [95% CI: 0.10, 0.57]). In contrast, phenotypic and genetic correlations between the thickness/volume signature and WMHs were nonsignificant. Environmental correlations between each AD signature and WMH were similarly nonsignificant. Results were similar for each WMH parcellation, suggesting global WMH effects.ConclusionA gray matter MD signature and WMHs share significant genetic influences, whereas a thickness/volume signature was not associated with WMHs. AD signatures based on brain microstructure, such as the MD signature, may capture very early AD‐related and vascular‐related changes that are not captured by a macrostructural signature at the same timepoint.

White matter hyperintensity burden does not differentiate SuperAgers from average cognitive agers

AbstractBackgroundThe amount of white matter hyperintensity (WMH) found on T2‐weighted imaging has shown a strong relationship with age and is thought to be a marker of ischemia‐associated demyelination or secondary axonal degeneration associated with neurodegenerative disease. Previous healthy older aging studies have shown increased WMH are associated with poorer episodic memory performance and decreased volume of medial temporal lobe regions. Here, we examine if lower WMH are associated with a phenotype of successful cognitive aging, SuperAging. SuperAgers are participants over the age 80 with episodic memory at least as good as that of average middle‐aged adults.MethodWe quantified the WMH volume from T2‐FLAIR imaging with a pre‐trained Bayesian 3D U‐Net convolutional neural network in SuperAgers and cognitively healthy elderly controls (EC) of a similar age and education. All participants underwent the ADNI‐3 FLAIR on the same 3T Prisma MRI. WMH volume was square root transformed to account for the skewed distribution. A 2‐tail independent samples t‐test evaluated the difference in WMH volume between SuperAgers and EC. Additionally, we examined if there were differences within SA and EC groups by sex.Result46 SuperAgers (average age 86.3 ± 1.86; average years of education 16.9 ± 1.9) and 25 EC (average age 87.1 ± 5.17; average years of education 17.1 ± 3.1) met criteria and were included in the study. There was no significant difference in the volume of WMH between SuperAgers and ECs (t = 1.01, p = 0.32). Further, there was no significant difference in WMH by sex within the SuperAging group (t = 0.10, p = 0.92) or EC group (t = 0.82, p = 0.42).ConclusionResistance to the development of WMH, a cross‐sectional marker of cerebrovascular disease and demyelination, does not appear to be a strong discriminating factor in 80+ year‐olds with superior memory function compared to cognitively average agers. Future analyses will include longitudinal changes in WMH and examining regional WMH. Cognitive aging is associated with several underlying brain‐based etiologies, and SuperAging may be better explained by a more sophisticated multi‐modal approach.

A Twin Analysis of AD Brain Signatures and Abnormal White Matter

AbstractBackgroundAlzheimer’s disease (AD) and vascular disease frequently co‐occur and may interact additively or synergistically on risk for cognitive decline, though the degree of shared overlap between these pathologies remains unclear. Our group has demonstrated the utility of AD signatures, or composite MRI metrics in brain regions associated with AD pathology, for prediction of AD‐related changes beginning in midlife. Our novel signature based on gray matter mean diffusivity (MD) aided 12‐year prediction of incident mild cognitive impairment among cognitively unimpaired adults in their 50s, captured unique phenotypic and genetic variance not otherwise explained by an AD signature based on cortical thickness/volume or general brain aging, and robustly predicted thickness/volume signatures over a decade later. Here, we leveraged twin data from the Vietnam Era Twin Study of Aging (VETSA) to delineate shared and unique genetic and environmental influences on two AD signatures and white matter hyperintensities (WMHs), which have been consistently linked to vascular origin.MethodParticipants were 512 men from the VETSA (age = 67.52, SD = 2.60). Our validated thickness/volume signature, novel MD signature based on the same brain regions as the thickness/volume signature, and WMH volume were used in biometrical twin analyses to examine their phenotypic, genetic, and environmental relationships. We adjusted each AD signature for an MRI‐based measure of brain age to detect associations with WMH that were specific to AD‐related brain regions versus general brain aging. We also examined regional WMH parcellations.ResultPhenotypic and genetic correlations demonstrated significant associations between the MD signature and WMH (rp = 0.26 [95% CI: 0.15, 0.36]; rg = 0.34 [95% CI: 0.10, 0.57]). In contrast, phenotypic and genetic correlations between the thickness/volume signature and WMHs were nonsignificant. Environmental correlations between each AD signature and WMH were similarly nonsignificant. Results were similar for each WMH parcellation, suggesting global WMH effects.ConclusionA gray matter MD signature and WMHs share significant genetic influences, whereas a thickness/volume signature was not associated with WMHs. AD signatures based on brain microstructure, such as the MD signature, may capture very early AD‐related and vascular‐related changes that are not captured by a macrostructural signature at the same timepoint.

A multi‐center pooled analysis of individual imaging data of 14,876 non‐demented participants to create normative data for total and regional white matter hyperintensity volumes to support dementia diagnosis.

AbstractBackgroundWhite matter hyperintensities (WMH) are a common manifestation of cerebral small vessel disease and a major cause of cognitive decline and dementia. Recent studies show that the cognitive impact of WMH depends on their location in strategic white matter regions. WMH are highly prevalent among asymptomatic individuals and increase with age. For dementia diagnosis, identifying patients with excessive total and regional (strategic) WMH therefore requires age‐ and sex specific norms, which are currently lacking. We aimed to obtain normative data for both total and regional WMH volumes in non‐demented community‐dwelling individuals.MethodWe harmonized individual person data from 15 cohorts, through the Meta VCI Map consortium (www.metavcimap.org). Cohorts were eligible for inclusion if participants were recruited from the population, underwent brain MRI (with availability of FLAIR and T1 sequences) and cognitive testing. Cohorts that recruited patients based on the presence of cognitive symptoms were not eligible for inclusion. Individuals fulfilling criteria for dementia were excluded. WMH were segmented and registered to the MNI‐152 template. WMH maps were used to calculate total WMH volume and regional WMH volumes in 20 pre‐specified white matter tracts. Normative data on WMH volumes were derived from observed values in 5‐years age bands and reported as cut‐off values for percentiles. All volumes are normalized WMH volumes (i.e. calculated on the MNI‐152 template).ResultWe analyzed 14,876 individuals with a mean age of 63.9 years (SD 11.9), 52% of whom were female. Median WMH volume was 2.0 mL (normalized, IQR 3.9) for the total sample. Median WMH volume increased with age, from 0.25 mL (&lt;45 years) to 7.3 and 12.8 mL (&gt;85 years) for men and women respectively. The table shows total WMH volume cut‐off values for percentiles, stratified for age and sex (cut‐off values for regional WMH volumes not shown due to abstract size constraints).ConclusionThis study provides age‐ and sex‐specific normative data on total and regional WMH volumes. This enables an individualized approach to interpreting total and regional WMH burden to support diagnosis in clinical practice.

Characterization of various type of cognitive impairment using multiomics – a pilot imaging study from a local institution

AbstractBackgroundIn addition to clinical diagnosis, multi‐modal imaging has been employed for early detection of various types of dementia. Image features from various types of images provided information for accurate diagnosis. This study aimed to evaluate the role of multiple imaging, including MRI T1W, T2W, resting state functional MRI (rs‐fMRI) and 18‐F Flutemetamol PET image in diagnosis of various types of cognitive impairments.Methods56 participants (16 Alzheimer’s Disease (AD), 10 AD type Mild Cognitive impairment (A‐MCI), 18 vascular type MCI (V‐MCI), 12 Vascular dementia (VD) and 25 Healthy Control (HC) were recruited in an local memory clinic. All types of images were re‐orientated, segmentation and normalized to the whole brain mask template. 45 brain regional volumes (Vol) were calculated from T1w using Freesurfer. Brain regional white matter hyperintensities (WMH) were obtained from T2w images. Interhemispheric functional connectivity (IFC) of brain regions were measured from rs‐fMRI. Standard uptake value (SUV) were measured and calculated from the PET images. Also, patient demographics including age, sex and HK‐MoCa score (Demo) were recorded. 70% of each group of participants were assigned to the training group, whereas the rest 30% were assigned to test group. The neural network toolbox of MATLAB was employed to build four characterization models: Model 1 based Vol and WMH; Model 2 based on Vol, WMH and IFC; Model 3 based on Vol, WMH, IFC, and demo; Model 4 based on Vol, WMH, IFC, demo and SUV.ResultsThe receiver operating characteristics (ROC) curves showed that the Model 1, 2 and 3 achieved satisfactory accuracy, with 79%, 68% and 70% respectively. While Model 4 achieved excellent accuracy of 100%. The sensitivity and specificity of each model for each group was over 75% to 100%. The model with more image features attained higher accuracy in dementia diagnosis.ConclusionArtificial neural network model with multiomics can accurately differentiate AD, A‐MCI, V‐MCI, VD and HC. Further study is suggested with more participants for models verification.

Differences in Alzheimer's Disease-Related Pathology Profiles Across Apolipoprotein Groups.

The apolipoprotein (APOE) ɛ4 allele is a risk factor for Alzheimer's disease (AD), whereas the ɛ2 allele is thought to be protective against AD. Few studies have examined the relationship between brain pathologies, atrophy, white matter hyperintensities (WMHs) and APOE status in those with the ɛ2ɛ4 genotype and results are inconsistent for those with an ɛ2 allele. Alzheimer's disease neuroimaging participants were divided into 1 of 4 APOE allele profiles (E4 = ɛ4ɛ4 or ɛ3ɛ4; E2 = ɛ2ɛ2 or ɛ2ɛ3; E3 = ɛ3ɛ3; or E24 = ɛ2ɛ4). Linear mixed models examined the relationship between APOE profiles and brain changes (i.e., regional WMHs, ventricle size, hippocampal and entorhinal cortex volume, amyloid level, and phosphorylated tau measures), while controlling for age, sex, education, and diagnostic status at baseline and over time. APOE ɛ4 was associated with increased pathology, whereas ɛ2 positivity is associated with reduced baseline and lower accumulation of pathologies and neurodegeneration. APOE ɛ2ɛ4 was similar to ɛ4 (increased neurodegeneration) but with a slower rate of change. The strong associations observed between APOE and pathology show the importance of how genetic factors influence structural brain changes. These findings suggest that ɛ2ɛ4 genotype is related to increased declines associated with the ɛ4 as opposed to the protective effects of the ɛ2. These findings have important implications for initiating treatments and interventions. Given that people with the ɛ2ɛ4 genotype can expect to have increased atrophy, they should be considered (alongside those with an ɛ4) in targeted interventions to reduce brain changes that occur with AD.

6 Posterior cerebral artery-defined white matter hyperintensities are associated with object domain memory and transentorhinal volume independently of global beta-amyloid burden

Objective:White matter hyperintensities (WMH) are a radiological marker of small vessel cerebrovascular disease that are related to cognition and memory decline in aging and Alzheimer’s disease (AD). However, the mechanisms that link WMH to memory impairment and whether they interact with or act independently of AD pathophysiology are unclear. The transentorhinal cortex (BA35) is among the earliest anatomical regions to show tau deposition and subsequent atrophy, and baseline posterior WMH is related to longitudinal cortical thinning of the entorhinal cortex. However, it is unclear whether regional WMH are related to BA35 volume specifically, and whether this relationship is influenced by amyloid-β (Aβ) burden. We hypothesized that WMH in the vascular territory of the posterior cerebral artery (PCA), which perfuses both posterior and medial temporal lobe regions, would be associated with reduced BA35 volume and with lower memory in older adults independently of Aβ.Participants and Methods:114 older adults without dementia, aged 60 to 98 years (mean (SD) = 78.31 (11.02), 71 (62.8%) women), were included. Regional WMH volumes were derived from T2-FLAIR images using ANTs, a vascular territory atlas and manual editing. Global Aβ was assessed with 18F-florbetapir PET, using SUVR of a cortical composite region (FBP mean SUVR) with a cerebellar reference region. Total transentorhinal (BA35) volume was derived using T1 and T2-weighted images using ASHS. To assess hippocampal pattern separation ability, an index of episodic memory, participants completed both object (MDT-O) and spatial (MDT-S) versions of a mnemonic discrimination task, with the lure discrimination index as the outcome. Using linear regressions, we first tested for associations among PCA-defined WMH, Aβ, BA35 volume, and MDT-S and MDT-O scores. We then tested whether the relationship between PCA-defined WMH and MDT-O performance was mediated by BA35 volume and whether this mediation was moderated by Aβ. All models adjusted for age, sex, and education.Results:PCA-defined WMH were related to higher FBP mean SUVR (b=0.287, p=0.042) and lower BA35 volume (b=-0.222, p=0.038). PCA-defined WMH were also negatively related to MDT-O performance (b=-0.229, p=0.044), but not to MDT-S (b=-0.171, p=0.118). FBP mean SUVR was not related to BA35 volume (b=-0.131, p=0.344) or MDT performance (MDT-S: b=-0.138, p=0.348; MDT-O: b=0.059, p=0.690). Furthermore, FBP mean SUVR did not interact with PCA-defined WMH to predict memory performance (interaction b=-0.039, p=0.973), nor BA35 volume (interaction b=-0.140, p=0.894). The association of PCA-defined WMH to MDT-O was fully mediated by BA35 volume (indirect effect b=-0.0005, 95% CI (-0.0014, -0.0003)). This mediation was not moderated by FBP mean SUVR (indirect effect b=-0.00001, 95% CI (-0.001, 0.001)).Conclusions:We found that PCA-defined WMH were related to memory performance in older adults, and this association is fully mediated by transentorhinal volume. While PCA-defined WMH are related to higher global Aβ burden, there is no interaction between PCA-defined WMH and Aβ on BA35 volume. These findings point to an amyloid-independent vascular pathway towards memory decline in aging and AD. Future work should examine whether the pathway linking PCA-defined WMH to transentorhinal cortex atrophy and subsequent memory decline is mediated by regional tau pathology.