Structural neuroimaging in Altheimer's disease: do white matter hyperintensities matter?

Experimental Ischemic Stroke Induces Secondary Bihemispheric White Matter Degeneration and Long-Term Cognitive Impairment

Clinical studies have identified widespread white matter degeneration in ischemic stroke patients. However, contemporary research in stroke has predominately focused on the infarct and periinfarct penumbra regions. The involvement of white matter degeneration after ischemic stroke and its contribution to post-stroke cognitive impairment and dementia (PSCID) has remained less explored in experimental models. In this study, we examined the progression of locomotor and cognitive function up to 4 months after inducing ischemic stroke by middle cerebral artery occlusion in young adult rats. Despite evident ongoing locomotor recovery, long-term cognitive and affective impairments persisted after ischemic stroke, as indicated by Morris water maze, elevated plus maze, and open field performance. At 4 months after stroke, multimodal MRI was conducted to assess white matter degeneration. T2-weighted MRI (T2WI) unveiled bilateral cerebroventricular enlargement after ischemic stroke. Fluid Attenuated Inversion Recovery MRI (FLAIR) revealed white matter hyperintensities in the corpus callosum and fornix across bilateral hemispheres. A positive association between the volume of white matter hyperintensities and total cerebroventricular volume was noted in stroke rats. Further evidence of bilateral white matter degeneration was indicated by the reduction of fractional anisotropy and quantitative anisotropy at bilateral corpus callosum in diffusion-weighted MRI (DWI) analysis. Additionally, microglia and astrocyte activation were identified in the bilateral corpus callosum after stroke. Our study suggests that experimental ischemic stroke induced by MCAO in young rat replicate long-term cognitive impairment and bihemispheric white matter degeneration observed in ischemic stroke patients. This model provides an invaluable tool for unraveling the mechanisms underlying post-stroke secondary white matter degeneration and its contribution to PSCID.

Reliability assessment of accelerated MR sequences for the estimation of structural and vascular markers in dementia

Estimating the volume of brain structures and white matter lesions has been demonstrated to be crucial as diagnostic markers of dementia. In this context, employing accelerated MR sequences could be particularly suitable for deploying comfortable imaging protocols. The aims of the study are twofold. First, the quality of accelerated structural and FLAIR sequences will be evaluated using conventional sequences as a comparative reference. Second, their concordance in the estimation of diagnostic markers will be assessed. Forty-six dementia patients underwent brain 3T MR protocol, including conventional and accelerated 3D T1w and 3D FLAIR sequences. The image quality was assessed using peak signal-to-noise ratio, structural similarity index measure, and mean squared error. The intraclass correlation and the Dice similarity coefficients were used to compare the markers. The quality assessment showed high agreement between accelerated and conventional sequences. Excellent concordance was demonstrated in the quantification of brain structures and white matter lesions. The results demonstrate the reliability of diagnostic markers of dementia derived from accelerated MR sequences, thereby supporting their use in clinical practice.

Molecular profiling of frontal and occipital subcortical white matter hyperintensities in Alzheimer's disease

White matter hyperintensities (WMHs) are commonly detected on T2-weighted magnetic resonance imaging (MRI) scans, occurring in both typical aging and Alzheimer's disease (AD). Despite their frequent appearance and their association with cognitive decline in AD, the molecular factors contributing to WMHs remain unclear. In this study, we investigated the transcriptomic profiles of two commonly affected brain regions with coincident AD pathology-frontal subcortical white matter (frontal-WM) and occipital subcortical white matter (occipital-WM)-and compared with age-matched cognitively intact controls. Through RNA-sequencing in frontal- and occipital-WM bulk tissues, we identified an upregulation of genes associated with brain vasculature function in AD white matter. To further elucidate vasculature-specific transcriptomic features, we performed RNA-seq analysis on blood vessels isolated from these white matter regions, which revealed an upregulation of genes related to protein folding pathways. Finally, comparing gene expression profiles between AD individuals with high- versus low-WMH burden showed an increased expression of pathways associated with immune function. Taken together, our study characterizes the diverse molecular profiles of white matter changes in AD and provides mechanistic insights into the processes underlying AD-related WMHs.

Marital status, brain health, and cognitive reserve among diverse older adults

OBJECTIVE

Being married may protect late-life cognition. Less is known about living arrangement among unmarried adults and mechanisms such as brain health (BH) and cognitive reserve (CR) across race and ethnicity or sex/gender. The current study examines (1) associations between marital status, BH, and CR among diverse older adults and (2) whether one's living arrangement is linked to BH and CR among unmarried adults.

METHOD

Cross-sectional data come from the Washington Heights-Inwood Columbia Aging Project (N = 778, 41% Hispanic, 33% non-Hispanic Black, 25% non-Hispanic White; 64% women). Magnetic resonance imaging (MRI) markers of BH included cortical thickness in Alzheimer's disease signature regions and hippocampal, gray matter, and white matter hyperintensity volumes. CR was residual variance in an episodic memory composite after partialing out MRI markers. Exploratory analyses stratified by race and ethnicity and sex/gender and included potential mediators.

RESULTS

Marital status was associated with CR, but not BH. Compared to married individuals, those who were previously married (i.e., divorced, widowed, and separated) had lower CR than their married counterparts in the full sample, among White and Hispanic subgroups, and among women. Never married women also had lower CR than married women. These findings were independent of age, education, physical health, and household income. Among never married individuals, living with others was negatively linked to BH.

CONCLUSIONS

Marriage may protect late-life cognition via CR. Findings also highlight differential effects across race and ethnicity and sex/gender. Marital status could be considered when assessing the risk of cognitive impairment during routine screenings.

Neuroimaging correlates of Alzheimer's disease biomarker concentrations in a racially diverse high-risk cohort of middle-aged adults

INTRODUCTION

In this study, we investigated biomarkers in a midlife, racially diverse, at-risk cohort to facilitate early identification and intervention. We examined neuroimaging measures, including resting state functional magnetic resonance imaging (fMRI), white matter hyperintensity vo (WMH), and hippocampal volumes, alongside cerebrospinal fluid (CSF) markers.

METHODS

Our data set included 76 cognitively unimpaired, middle-aged, Black Americans (N = 29, F/M = 17/12) and Non-Hispanic White (N = 47, F/M = 27/20) individuals. We compared cerebrospinal fluid phosphorylated tau141 and amyloid beta (Aβ)42 to fMRI default mode network (DMN) subnetwork connectivity, WMH volumes, and hippocampal volumes.

RESULTS

Results revealed a significant race × Aβ42 interaction in Black Americans: lower Aβ42 was associated with reduced DMN connectivity and increased WMH volumes regions but not in non-Hispanic White individuals.

DISCUSSION

Our findings suggest that precuneus DMN connectivity and temporal WMHs may be linked to Alzheimer's disease risk pathology during middle age, particularly in Black Americans.

HIGHLIGHTS

Cerebrospinal fluid (CSF) amyloid beta (Aβ)42 relates to precuneus functional connectivity in Black, but not White, Americans. Higher white matter hyperintensity volume relates to lower CSF Aβ42 in Black Americans. Precuneus may be a hub for early Alzheimer's disease pathology changes detected by functional connectivity.

Molecular profiling of frontal and occipital subcortical white matter hyperintensities in Alzheimer's disease

White matter hyperintensities (WMHs) are commonly detected on T2-weighted magnetic resonance imaging (MRI) scans, occurring in both typical aging and Alzheimer's disease. Despite their frequent appearance and their association with cognitive decline, the molecular factors contributing to WMHs remain unclear. In this study, we investigated the transcriptomic profiles of two commonly affected brain regions with coincident AD pathology-frontal subcortical white matter (frontal-WM) and occipital subcortical white matter (occipital-WM)-and compared with age-matched healthy controls. Through RNA-sequencing in frontal- and occipital-WM bulk tissues, we identified an upregulation of genes associated with brain vasculature function in AD white matter. To further elucidate vasculature-specific transcriptomic features, we performed RNA-seq analysis on blood vessels isolated from these white matter regions, which revealed an upregulation of genes related to protein folding pathways. Finally, comparing gene expression profiles between AD individuals with high- versus low-WMH burden showed an increased expression of pathways associated with immune function. Taken together, our study characterizes the diverse molecular profiles of white matter changes in AD compared to normal aging and provides new mechanistic insights processes underlying AD-related WMHs.

White matter hyperintensity patterns: associations with comorbidities, amyloid, and cognition

BACKGROUND

White matter hyperintensities (WMHs) are often measured globally, but spatial patterns of WMHs could underlie different risk factors and neuropathological and clinical correlates. We investigated the spatial heterogeneity of WMHs and their association with comorbidities, Alzheimer's disease (AD) risk factors, and cognition.

METHODS

In this cross-sectional study, we studied 171 cognitively unimpaired (CU; median age: 65 years, range: 50 to 89) and 51 mildly cognitively impaired (MCI; median age: 72, range: 53 to 89) individuals with available amyloid (18F-flutementamol) PET and FLAIR-weighted images. Comorbidities were assessed using the Cumulative Illness Rating Scale (CIRS). Each participant's white matter was segmented into 38 parcels, and WMH volume was calculated in each parcel. Correlated principal component analysis was applied to the parceled WMH data to determine patterns of WMH covariation. Adjusted and unadjusted linear regression models were used to investigate associations of component scores with comorbidities and AD-related factors. Using multiple linear regression, we tested whether WMH component scores predicted cognitive performance.

RESULTS

Principal component analysis identified four WMH components that broadly describe FLAIR signal hyperintensities in posterior, periventricular, and deep white matter regions, as well as basal ganglia and thalamic structures. In CU individuals, hypertension was associated with all patterns except the periventricular component. MCI individuals showed more diverse associations. The posterior and deep components were associated with renal disorders, the periventricular component was associated with increased amyloid, and the subcortical gray matter structures was associated with sleep disorders, endocrine/metabolic disorders, and increased amyloid. In the combined sample (CU + MCI), the main effects of WMH components were not associated with cognition but predicted poorer episodic memory performance in the presence of increased amyloid. No interaction between hypertension and the number of comorbidities on component scores was observed.

CONCLUSION

Our study underscores the significance of understanding the regional distribution patterns of WMHs and the valuable insights that risk factors can offer regarding their underlying causes. Moreover, patterns of hyperintensities in periventricular regions and deep gray matter structures may have more pronounced cognitive implications, especially when amyloid pathology is also present.

Racial and ethnic differences in the relationship between financial worry and white matter hyperintensities in Latinx, non-Latinx Black, and non-Latinx White older adults

Socioeconomic status (SES) is associated with white matter hyperintensities (WMHs) and contributes to racial and ethnic health disparities. However, traditional measures of SES may not accurately represent individual financial circumstances among non-Latinx Black and Latinx older adults due to longstanding structural inequities. This study examined associations between multiple SES indicators (education, income, subjective financial worry) and WMHs across non-Latinx Black, Latinx, and non-Latinx White older adults in the Washington Heights-Inwood Columbia Aging Project (N = 662). Latinx participants reported the lowest SES and greatest financial worry, while Black participants evidenced the most WMHs. Greater financial worry was associated with higher WMHs volume above and beyond education and income, which were not associated with WMHs. However, this association was only evident among Latinx older adults. These results provide evidence for the minority poverty hypothesis and highlight the need for systemic socioeconomic interventions to alleviate brain health disparities in older adulthood.

Complexities of cerebral small vessel disease, blood pressure, and dementia relationship: new insights from genetics

Importance

There is increasing recognition that vascular disease, which can be treated, is a key contributor to dementia risk. However, the contribution of specific markers of vascular disease is unclear and, as a consequence, optimal prevention strategies remain unclear.

Objective

To disentangle the causal relation of several key vascular traits to dementia risk: (i) white matter hyperintensity (WMH) burden, a highly prevalent imaging marker of covert cerebral small vessel disease (cSVD); (ii) clinical stroke; and (iii) blood pressure (BP), the leading risk factor for cSVD and stroke, for which efficient therapies exist. To account for potential epidemiological biases inherent to late-onset conditions like dementia.

Design Setting and Participants

This study first explored the association of genetically determined WMH, BP levels and stroke risk with AD using summary-level data from large genome-wide association studies (GWASs) in a two-sample Mendelian randomization (MR) framework. Second, leveraging individual-level data from large longitudinal population-based cohorts and biobanks with prospective dementia surveillance, the association of weighted genetic risk scores (wGRSs) for WMH, BP, and stroke with incident all-cause-dementia was explored using Cox-proportional hazard and multi-state models. The data analysis was performed from July 26, 2020, through July 24, 2022.

Exposures

Genetically determined levels of WMH volume and BP (systolic, diastolic and pulse blood pressures) and genetic liability to stroke.

Main outcomes and measures

The summary-level MR analyses focused on the outcomes from GWAS of clinically diagnosed AD (n-cases=21,982) and GWAS additionally including self-reported parental history of dementia as a proxy for AD diagnosis (ADmeta, n-cases=53,042). For the longitudinal analyses, individual-level data of 157,698 participants with 10,699 incident all-cause-dementia were studied, exploring AD, vascular or mixed dementia in secondary analyses.

Results

In the two-sample MR analyses, WMH showed strong evidence for a causal association with increased risk of ADmeta (OR, 1.16; 95%CI:1.05-1.28; P=.003) and AD (OR, 1.28; 95%CI:1.07-1.53; P=.008), after accounting for genetically determined pulse pressure for the latter. Genetically predicted BP traits showed evidence for a protective association with both clinically defined AD and ADmeta, with evidence for confounding by shared genetic instruments. In longitudinal analyses the wGRSs for WMH, but not BP or stroke, showed suggestive association with incident all-cause-dementia (HR, 1.02; 95%CI:1.00-1.04; P=.06). BP and stroke wGRSs were strongly associated with mortality but there was no evidence for selective survival bias during follow-up. In secondary analyses, polygenic scores with more liberal instrument definition showed association of both WMH and stroke with all-cause-dementia, AD, and vascular or mixed dementia; associations of stroke, but not WMH, with dementia outcomes were markedly attenuated after adjusting for interim stroke.

Conclusion

These findings provide converging evidence that WMH is a leading vascular contributor to dementia risk, which may better capture the brain damage caused by BP (and other etiologies) than BP itself and should be targeted in priority for dementia prevention in the population.

The association between white matter hyperintensities and amyloid and tau deposition

White matter hyperintensities (WMHs) frequently occur in Alzheimer's Disease (AD) and have a contribution from ischemia, though their relationship with β-amyloid and cardiovascular risk factors (CVRFs) is not completely understood. We used AT classification to categorize individuals based on their β-amyloid and tau pathologies, then assessed the effects of β-amyloid and tau on WMH volume and number. We then determined regions in which β-amyloid and WMH accumulation were related. Last, we analyzed the effects of various CVRFs on WMHs. As secondary analyses, we observed effects of age and sex differences, atrophy, cognitive scores, and APOE genotype. PET, MRI, FLAIR, demographic, and cardiovascular health data was collected from the Alzheimer's Disease Neuroimaging Initiative (ADNI-3) (N = 287, 48 % male). Participants were categorized as A + and T + if their Florbetapir SUVR and Flortaucipir SUVR were above 0.79 and 1.25, respectively. WMHs were mapped on MRI using a deep convolutional neural network (Sepehrband et al., 2020). CVRF scores were based on history of hypertension, systolic and diastolic blood pressure, pulse rate, respiration rate, BMI, and a cumulative score with 6 being the maximum score. Regression models and Pearson correlations were used to test associations and correlations between variables, respectively, with age, sex, years of education, and scanner manufacturer as covariates of no interest. WMH volume percent was significantly associated with global β-amyloid (r = 0.28, p < 0.001), but not tau (r = 0.05, p = 0.25). WMH volume percent was higher in individuals with either A + or T + pathology compared to controls, particularly within in the A+/T + group (p = 0.007, Cohen's d = 0.4, t = -2.5). Individual CVRFs nor cumulative CVRF scores were associated with increased WMH volume. Finally, the regions where β-amyloid and WMH count were most positively associated were the middle temporal region in the right hemisphere (r = 0.18, p = 0.002) and the fusiform region in the left hemisphere (r = 0.017, p = 0.005). β-amyloid and WMH have a clear association, though the mechanism facilitating this association is still not fully understood. The associations found between β-amyloid and WMH burden emphasizes the relationship between β-amyloid and vascular lesion formation while factors like CVRFs, age, and sex affect AD development through various mechanisms. These findings highlight potential causes and mechanisms of AD as targets for future preventions and treatments. Going forward, a larger emphasis may be placed on β-amyloid's vascular effects and the implications of impaired brain clearance in AD.

Longitudinal associations between racial discrimination and hippocampal and white matter hyperintensity volumes among older Black adults

RATIONALE

Non-Hispanic Black older adults are at higher risk of Alzheimer's disease and related dementias (ADRD) than non-Hispanic Whites, which reflects racial disparities in both brain and cognitive health. Discrimination may contribute to these disparities, but much of the research on discrimination and ADRD outcomes is cross-sectional and/or does not disaggregate experiences of discrimination by attribution. Focusing specifically on racial discrimination and considering longitudinal brain outcomes may advance our understanding of the role of discrimination in explaining disproportionate rates of ADRD among non-Hispanic Black older adults.

METHODS

In total, 221 non-Hispanic Black participants in the Washington Heights-Inwood Columbia Aging Project completed multiple measures of discrimination at one time point and structural magnetic resonance imaging (MRI) scans at two time points. Everyday discrimination and lifetime discrimination were operationalized first as aggregate experiences of discrimination (regardless of identity attributions) and then as racial discrimination per se. MRI outcomes included hippocampal and white matter hyperintensity (WMH) volumes. Latent difference score models estimated associations between the discrimination measures and each MRI outcome over four years.

RESULTS

Aggregate discrimination (regardless of attributions) was not associated with either outcome. Lifetime racial discrimination was associated with lower initial hippocampal volume. Everyday racial discrimination was associated with faster accumulation of WMH over time.

CONCLUSIONS

Racial discrimination may be detrimental for brain aging among non-Hispanic Black older adults, which may contribute to their disproportionate dementia burden. Disaggregating discrimination by attribution may clarify research on racial inequalities in brain and cognitive aging, as racial discrimination appears to be particularly toxic.

Brain Aging Among Racially and Ethnically Diverse Middle-Aged and Older Adults

Importance

Neuroimaging studies have documented racial and ethnic disparities in brain health in old age. It remains unclear whether these disparities are apparent in midlife.

Objective

To assess racial and ethnic disparities in magnetic resonance imaging (MRI) markers of cerebrovascular disease and neurodegeneration in midlife and late life.

Design, Setting, and Participants

Data from 2 community-based cohort studies, Washington Heights-Inwood Columbia Aging Project (WHICAP) and the Offspring Study of Racial and Ethnic Disparities in Alzheimer Disease (Offspring), were used. Enrollment took place from March 2011 and June 2017, in WHICAP and Offspring, respectively, to January 2021. Of the 822 Offspring and 1254 WHICAP participants approached for MRI scanning, 285 and 176 refused participation in MRI scanning, 36 and 76 were excluded for contraindications/ineligibility, and 4 and 32 were excluded for missing key variables, respectively.

Main Outcomes and Measures

Cortical thickness in Alzheimer disease-related regions, white matter hyperintensity (WMH) volume.

Results

The final sample included 1467 participants. Offspring participants (497 [33.9%]) had a mean (SD) age of 55 (10.7) years, had a mean (SD) of 13 (3.5) years of education, and included 117 Black individuals (23.5%), 348 Latinx individuals (70%), 32 White individuals (6.4%), and 324 women (65.2%). WHICAP participants (970 [66.1%]) had a mean (SD) age of 75 (6.5) years, had a mean (SD) of 12 (4.7) years of education, and included 338 Black individuals (34.8%), 389 Latinx individuals (40.1%), 243 White individuals (25.1%), and 589 women (65.2%). Racial and ethnic disparities in cerebrovascular disease were observed in both midlife (Black-White: B = 0.357; 95% CI, 0.708-0.007; P = .046) and late life (Black-Latinx: B = 0.149, 95% CI, 0.068-0.231; P < .001; Black-White: B = 0.166; 95% CI, 0.254-0.077; P < .001), while disparities in cortical thickness were evident in late life only (Black-Latinx: B = -0.037; 95% CI, -0.055 to -0.019; P < .001; Black-White: B = -0.064; 95% CI -0.044 to -0.084; P < .001). Overall, Black-White disparities were larger than Latinx-White disparities for cortical thickness and WMH volume. Brain aging, or the association of age with MRI measures, was greater in late life compared with midlife for Latinx (cortical thickness: B = 0.006; 95% CI, 0.004-0.008; P < .001; WMH volume: B = -0.010; 95% CI, -0.018 to -0.001; P = .03) and White (cortical thickness: B = 0.005; 95% CI, 0.002-0.008; P = .001; WMH volume: B = -0.021; 95% CI -0.043 to 0.002; P = .07) participants but not Black participants (cortical thickness: B = 0.001; 95% CI, -0.002 to 0.004; P =.64; WMH volume: B = 0.003; 95% CI, -0.010 to 0.017; P = .61), who evidenced a similarly strong association between age and MRI measures in midlife and late life.

Conclusions and Relevance

In this study, racial and ethnic disparities in small vessel cerebrovascular disease were apparent in midlife. In Latinx and White adults, brain aging was more pronounced in late life than midlife, whereas Black adults showed accelerated pattern of brain aging beginning in midlife.

Multi-Site Cross-Site Inter-Rater and Test-Retest Reliability and Construct Validity of the MarkVCID White Matter Hyperintensity Growth and Regression Protocol

BACKGROUND

White matter hyperintensities (WMH) that occur in the setting of vascular cognitive impairment and dementia (VCID) may be dynamic increasing or decreasing volumes or stable over time. Quantifying such changes may prove useful as a biomarker for clinical trials designed to address vascular cognitive-impairment and dementia and Alzheimer's Disease.

OBJECTIVE

Conducting multi-site cross-site inter-rater and test-retest reliability of the MarkVCID white matter hyperintensity growth and regression protocol.

METHODS

The NINDS-supported MarkVCID Consortium evaluated a neuroimaging biomarker developed to track WMH change. Test-retest and cross-site inter-rater reliability of the protocol were assessed. Cognitive test scores were analyzed in relation to WMH changes to explore its construct validity.

RESULTS

ICC values for test-retest reliability of WMH growth and regression were 0.969 and 0.937 respectively, while for cross-site inter-rater ICC values for WMH growth and regression were 0.995 and 0.990 respectively. Word list long-delay free-recall was negatively associated with WMH growth (p < 0.028) but was not associated with WMH regression.

CONCLUSIONS

The present data demonstrate robust ICC validity of a WMH growth/regression protocol over a one-year period as measured by cross-site inter-rater and test-retest reliability. These data suggest that this approach may serve an important role in clinical trials of disease-modifying agents for VCID that may preferentially affect WMH growth, stability, or regression.

Vigilant Attention, Cerebral Blood Flow and Grey Matter Volume Change after 36 h of Acute Sleep Deprivation in Healthy Male Adults: A Pilot Study

It is commonly believed that alertness and attention decrease after sleep deprivation (SD). However, there are not enough studies on the changes in psychomotor vigilance testing (PVT) during SD and the corresponding changes in brain function and brain structure after SD. Therefore, we recruited 30 healthy adult men to perform a 36 h acute SD experiment, including the measurement of five indicators of PVT every 2 h, and analysis of cerebral blood flow (CBF) and grey matter volume (GMV) changes, before and after SD by magnetic resonance imaging (MRI). The PVT measurement found that the mean reaction time (RT), fastest 10% RT, minor lapses, and false starts all increased progressively within 20 h of SD, except for major lapses. Subsequently, all indexes showed a significant lengthening or increasing trend, and the peak value was in the range of 24 h-32 h and decreased at 36 h, in which the number of major lapses returned to normal. MRI showed that CBF decreased in the left orbital part of the superior frontal gyrus, the left of the rolandic operculum, the left triangular part, and the right opercular part of the inferior frontal gyrus, and CBF increased in the left lingual gyrus and the right superior gyrus after 36 h SD. The left lingual gyrus was negatively correlated with the major lapses, and both the inferior frontal gyrus and the superior frontal gyrus were positively correlated with the false starts. Still, there was no significant change in GMV. Therefore, we believe that 36 h of acute SD causes alterations in brain function and reduces alert attention, whereas short-term acute SD does not cause changes in brain structure.

The Cognitive Effects of Radiotherapy for Brain Metastases

Brain metastases are the most common intracranial neoplasm and are seen in upwards of 10-30% of patients with cancer. For decades, whole brain radiation therapy (WBRT) was the mainstay of treatment in these patients. While WBRT is associated with excellent rates of intracranial tumor control, studies have demonstrated a lack of survival benefit, and WBRT is associated with higher rates of cognitive deterioration and detrimental effects on quality of life. In recent years, strategies to mitigate this risk, such as the incorporation of memantine and hippocampal avoidance have been employed with improved results. Furthermore, stereotactic radiosurgery (SRS) has emerged as an appealing treatment option over the last decade in the management of brain metastases and is associated with superior cognitive preservation and quality of life when compared to WBRT. This review article evaluates the pathogenesis and impact of cranial irradiation on cognition in patients with brain metastases, as well as current and future risk mitigation techniques.

White-Matter Hyperintensity Load and Differences in Resting-State Network Connectivity Based on Mild Cognitive Impairment Subtype

"Mild cognitive impairment" (MCI) is a diagnosis characterised by deficits in episodic memory (aMCI) or in other non-memory domains (naMCI). Although the definition of subtypes is helpful in clinical classification, it provides little insight on the variability of neurofunctional mechanisms (i.e., resting-state brain networks) at the basis of symptoms. In particular, it is unknown whether the presence of a high load of white-matter hyperintensities (WMHs) has a comparable effect on these functional networks in aMCI and naMCI patients. This question was addressed in a cohort of 123 MCI patients who had completed an MRI protocol inclusive of T1-weighted, fluid-attenuated inversion recovery (FLAIR) and resting-state fMRI sequences. T1-weighted and FLAIR images were processed with the Lesion Segmentation Toolbox to quantify whole-brain WMH volumes. The CONN toolbox was used to preprocess all fMRI images and to run an independent component analysis for the identification of four large-scale haemodynamic networks of cognitive relevance (i.e., default-mode, salience, left frontoparietal, and right frontoparietal networks) and one control network (i.e., visual network). Patients were classified based on MCI subtype (i.e., aMCI vs. naMCI) and WMH burden (i.e., low vs. high). Maps of large-scale networks were then modelled as a function of the MCI subtype-by-WMH burden interaction. Beyond the main effects of MCI subtype and WMH burden, a significant interaction was found in the salience and left frontoparietal networks. Having a low WMH burden was significantly more associated with stronger salience-network connectivity in aMCI (than in naMCI) in the right insula, and with stronger left frontoparietal-network connectivity in the right frontoinsular cortex. Vice versa, having a low WMH burden was significantly more associated with left-frontoparietal network connectivity in naMCI (than in aMCI) in the left mediotemporal lobe. The association between WMH burden and strength of connectivity of resting-state functional networks differs between aMCI and naMCI patients. Although exploratory in nature, these findings indicate that clinical profiles reflect mechanistic interactions that may play a central role in the definition of diagnostic and prognostic statuses.

Development of a protocol to assess within-subject, regional white matter hyperintensity changes in aging and dementia

BACKGROUND

White matter hyperintensities (WMH), associated with both dementia risk and progression, can individually progress, remain stable, or even regress influencing cognitive decline related to specific cerebrovascular-risks. This study details the development and validation of a registration protocol to assess regional, within-subject, longitudinal WMH changes (ΔWMH) that is currently lacking in the field.

NEW METHOD

3D-FLAIR images (baseline and one-year-visit) were used for protocol development and validation. The method was validated by assessing the correlation between forward and reverse longitudinal registration, and between summated regional progression-regression volumes and Global ΔWMH. The clinical relevance of growth-regression ΔWMH were explored in relation to an executive function test.

RESULTS

MRI scans for 79 participants (73.5 ± 8.8 years) were used in this study. Global ΔWMH vs. summated regional progression-regression volumes were highly associated (r2 = 0.90; p-value < 0.001). Bi-directional registration validated the registration method (r2 = 0.999; p-value < 0.001). Growth and regression, but not overall ΔWMH, were associated with one-year declines in performance on Trial-Making-Test-B.

COMPARISON WITH EXISTING METHOD(S)

This method presents a unique registration protocol for maximum tissue alignment, demonstrating three distinct patterns of longitudinal within-subject ΔWMH (stable, growth and regression).

CONCLUSIONS

These data detail the development and validation of a registration protocol for use in assessing within-subject, voxel-level alterations in WMH volume. The methods developed for registration and intensity correction of longitudinal within-subject FLAIR images allow regional and within-lesion characterization of longitudinal ΔWMH. Assessing the impact of associated cerebrovascular-risks and longitudinal clinical changes in relation to dynamic regional ΔWMH is needed in future studies.

Bootstrap approach for meta-synthesis of MRI findings from multiple scanners

BACKGROUND

Neuroimaging data from large epidemiologic cohort studies often come from multiple scanners. The variations of MRI measurements due to differences in magnetic field strength, image acquisition protocols, and scanner vendors can influence the interpretation of aggregated data. The purpose of the present study was to compare methods that meta-analyze findings from a small number of different MRI scanners.

METHODS

We proposed a bootstrap resampling method using individual participant data and compared it with two common random effects meta-analysis methods, DerSimonian-Laird and Hartung-Knapp, and a conventional pooling method that combines MRI data from different scanners. We first performed simulations to compare the power and coverage probabilities of the four methods in the absence and presence of scanner effects on measurements. We then examined the association of age with white matter hyperintensity (WMH) volumes from 787 participants.

RESULTS

In simulations, the bootstrap approach performed better than the other three methods in terms of coverage probability and power when scanner differences were present. However, the bootstrap approach was consistent with pooling, the optimal approach, when scanner differences were absent. In the association of age with WMH volume, we observed that age was significantly associated with WMH volumes using the bootstrap approach, pooling, and the DerSimonian-Laird method, but not using the Hartung-Knapp method (p < 0.0001 for the bootstrap approach, DerSimonian-Laird, and pooling but p = 0.1439 for the Hartung-Knapp approach).

CONCLUSION

The bootstrap approach using individual participant data is suitable for integrating outcomes from multiple MRI scanners regardless of absence or presence of scanner effects on measurements.

White matter hyperintensities and cognition across different Alzheimer's biomarker profiles

BACKGROUND/OBJECTIVES

To examine the association between white matter hyperintensities (WMH) and cognitive domains such as memory and executive function (EF) across different clinical and biomarker categories of Alzheimer's disease (AD).

DESIGN

Cross-sectional study.

SETTING

Alzheimer's Disease Neuroimaging Initiative.

PARTICIPANTS

A total of 216 cognitively normal (CN) participants and 407 participants with mild cognitive impairment (MCI) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) at baseline.

MEASUREMENTS

Based on the 2018 research framework, participants were classified using AT(N) (amyloid-β deposition [A], pathologic tau [T], and neurodegeneration [(N)]) biomarkers into one of three categories: biomarker negative [A - T- (N)-], amyloid negative but other biomarker positive [A - T ± (N)+ or A - T + (N)±] or amyloid positive [A + T ± (N)±]. Linear regression models were then used to examine the association between WMH and memory composite scores and EF composite scores.

RESULTS

Higher WMH burden was associated with worse EF in both CN and MCI subgroups while a significant association between WMH and memory was only found in the MCI subgroup. Furthermore, WMH was associated with EF in the group with A - T ± (N)+ or A - T + (N)± biomarker category, but not for A - T - (N)- (normal biomarker) and A + T ± (N) ± (AD pathology). The association between higher WMH and worse memory was independent of amyloid levels in individuals with MCI with evidence of AD pathology.

CONCLUSION

Vascular disease, as indexed by WMH, independent of AD pathology affects cognitive function in both CN and MCI subgroups. Future studies using the AT(N) research framework should consider white matter lesions as a key biomarker contributing to the clinical presentation of AD.

Subclinical Cognitive and Neuropsychiatric Correlates and Hippocampal Volume Features of Brain White Matter Hyperintensity in Healthy People

White matter hyperintensities (WMH) are associated with brain aging and behavioral symptoms as a possible consequence of disrupted white matter pathways. In this study, we investigated, in a cohort of asymptomatic subjects aged 50 to 80, the relationship between WMH, hippocampal atrophy, and subtle, preclinical cognitive and neuropsychiatric phenomenology. Thirty healthy subjects with WMH (WMH+) and thirty individuals without (WMH−) underwent comprehensive neuropsychological and neuropsychiatric evaluations and 3 Tesla Magnetic Resonance Imaging scan. The presence, degree of severity, and distribution of WMH were evaluated with a semi-automated algorithm. Volumetric analysis of hippocampal structure was performed through voxel-based morphometry. A multivariable logistic regression analysis indicated that phenomenology of subclinical apathy and anxiety was associated with the presence of WMH. ROI-based analyses showed a volume reduction in the right hippocampus of WMH+. In healthy individuals, WMH are associated with significant preclinical neuropsychiatric phenomenology, as well as hippocampal atrophy, which are considered as risk factors to develop cognitive impairment and dementia.

Cerebral white matter diffusion properties and free-water with obstructive sleep apnea severity in older adults

Characterizing the effects of obstructive sleep apnea (OSA) on the aging brain could be key in our understanding of neurodegeneration in this population. Our objective was to assess white matter properties in newly diagnosed and untreated adults with mild to severe OSA. Sixty‐five adults aged 55 to 85 were recruited and divided into three groups: control (apnea‐hypopnea index ≤5/hr; n = 18; 65.2 ± 7.2 years old), mild (>5 to ≤15 hr; n = 27; 64.2 ± 5.3 years old) and moderate to severe OSA (>15/hr; n = 20; 65.2 ± 5.5 years old). Diffusion tensor imaging metrics (fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity, and mean diffusivity) were compared between groups with Tract‐Based Spatial Statistics within the white matter skeleton created by the technique. Groups were also compared for white matter hyperintensities volume and the free‐water (FW) fraction. Compared with controls, mild OSA participants showed widespread areas of lower diffusivity (p < .05 corrected) and lower FW fraction (p < .05). Participants with moderate to severe OSA showed lower AD in the corpus callosum compared with controls (p < .05 corrected). No between‐group differences were observed for FA or white matter hyperintensities. Lower white matter diffusivity metrics is especially marked in mild OSA, suggesting that even the milder form may lead to detrimental outcomes. In moderate to severe OSA, competing pathological responses might have led to partial normalization of diffusion metrics.

White matter hyperintensities and their relationship to cognition: Effects of segmentation algorithm

White matter hyperintensities (WMHs) are brain white matter lesions that are hyperintense on fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) scans. Larger WMH volumes have been associated with Alzheimer's disease (AD) and with cognitive decline. However, the relationship between WMH volumes and cross-sectional cognitive measures has been inconsistent. We hypothesize that this inconsistency may arise from 1) the presence of AD-specific neuropathology that may obscure any WMH effects on cognition, and 2) varying criteria for creating a WMH segmentation. Manual and automated programs are typically used to determine segmentation boundaries, but criteria for those boundaries can differ. It remains unclear whether WMH volumes are associated with cognitive deficits, and which segmentation criteria influence the relationships between WMH volumes and clinical outcomes. In a sample of 260 non-demented participants (ages 55-90, 141 males, 119 females) from the Alzheimer's Disease Neuroimaging Initiative (ADNI), we compared the performance of five WMH segmentation methods, by relating the WMH volumes derived using each method to both clinical diagnosis and composite measures of executive function and memory. To separate WMH effects on cognition from effects related to AD-specific processes, we performed analyses separately in people with and without abnormal cerebrospinal fluid amyloid levels. WMH volume estimates that excluded more diffuse, lower-intensity lesions were more strongly correlated with clinical diagnosis and cognitive performance, and only in those without abnormal amyloid levels. These findings may inform best practices for WMH segmentation, and suggest that AD neuropathology may mask WMH effects on clinical diagnosis and cognition.

White Matter Regions With Low Microstructure in Young Adults Spatially Coincide With White Matter Hyperintensities in Older Adults

Microstructural and macrostructural white matter damage occurs frequently with aging, is associated with negative health outcomes, and can be imaged non-invasively as fractional anisotropy (FA) and white matter hyperintensities (WMH), respectively. The extent to which diminished microstructure precedes or results from macrostructural white matter damage is poorly understood. This study evaluated the hypothesis that white matter areas with normatively lower microstructure in young adults are most susceptible to develop WMH in older adults. Forty-nine younger participants (age = 25.8 ± 2.8 years) underwent diffusion-weighted imaging (DWI), and 557 older participants (age = 73.9 ± 5.7 years) underwent DWI and T2-weighted magnetic resonance imaging (MRI). In older adults, WMH had a mostly periventricular distribution with higher frequency in frontal regions. We found lower FA in areas of frank WMH compared to normal-appearing white matter (NAWM) in older adults. Then, to determine if areas of normatively lower white matter microstructure spatially overlap with areas that frequently develop macrostructural damage in older age, we created a WMH frequency map in which each voxel represented the percentage of older adults with a WMH in that voxel. We found lower normative FA in young adults with regions frequently segmented as WMH in older adults. We conclude that low white matter microstructure is observed in areas of white matter macrostructural damage, but white matter microstructure is also normatively low (i.e., at ages 20-30) in regions with high WMH frequency, prior to white matter macrostructural damage.

The relationship between white matter hyperintensities and cognitive reference abilities across the life span

We examined the relationship between white matter hyperintensities (WMH) burden and performance on 4 reference abilities: episodic memory, perceptual speed, fluid reasoning, and vocabulary. Cross-sectional data of 486 healthy adults from 20 to 80 years old enrolled in an ongoing longitudinal study were analyzed. A piecewise regression across age identified an inflection point at 43 years old, where WMH total volume began to increase with age. Subsequent analyses focused on participants above that age (N = 351). WMH total volume had significant inverse correlations with perceptual speed and memory. Regional measures of WMH showed inverse correlations with all reference abilities. We performed principal component analysis of the regional WMH data to create a model of principal components regression. Parietal WMH regional volume burden mediated the relationship between age and perceptual speed in simple and multiple mediation models. The principal components regression pattern associated with perceptual speed also mediated the relationship between age and perceptual speed performance. These results across the extended adult life span help clarify the influence of WMH on cognitive aging.

Regional White Matter Hyperintensity Influences Grey Matter Atrophy in Mild Cognitive Impairment

The association between cerebrovascular disease pathology (measured by white matter hyperintensities, WMH) and brain atrophy in early Alzheimer's disease (AD) remain to be elucidated. Thus, we investigated how WMH influence neurodegeneration and cognition in prodromal and clinical AD. We examined 51 healthy controls, 35 subjects with mild cognitive impairment (MCI), and 30 AD patients. We tested how total and regional WMH is related to specific grey matter volume (GMV) reductions in MCI and AD compared to controls. Stepwise regression analysis was further performed to investigate the association of GMV and regional WMH volume with global cognition. We found that total WMH volume was highest in AD but showed the strongest association with lower GMV in MCI. Frontal and parietal WMH had the most extensive influence on GMV loss in MCI. Additionally, parietal lobe WMH volume (but not hippocampal atrophy) was significantly associated with global cognition in MCI while smaller hippocampal volume (but not WMH volume) was associated with lower global cognition in AD. Thus, although WMH volume was highest in AD subjects, it had a more pervasive influence on brain structure and cognitive impairment in MCI. Our study thus highlights the importance of early detection of cerebrovascular disease, as its intervention at the MCI stage might potentially slow down neurodegeneration.

Cross-sectional and prospective inter-relationships between depressive symptoms, vascular disease and cognition in older adults

BACKGROUND

It has been proposed that vascular disease is the mechanism linking depression and cognition, but prospective studies have not supported this hypothesis. This study aims to investigate the inter-relationships between depressive symptoms, cognition and cerebrovascular disease using a well-characterised prospective cohort.

METHOD

Data came from waves 1 (2005-2007) and 2 (2007-2009) of the Sydney Memory and Ageing Study (n = 462; mean age = 78.3 years).

RESULTS

At wave 1, there was an association between depressive symptoms and white matter hyperintensity (WMH) volume [b = 0.016, t(414) = 2.34, p = 0.020]. Both depressive symptoms [b = -0.058, t(413) = -2.64, p = 0.009] and WMH volume [b = -0.011, t(413) = -3.77, p < 0.001], but not stroke/transient ischaemic attack (TIA) [b = -0.328, t(413) = -1.90, p = 0.058], were independently associated with lower cognition. Prospectively, cerebrovascular disease was not found to predict increasing depressive symptoms [stroke/TIA: b = -0.349, t(374.7) = -0.76, p = 0.448; WMH volume: b = 0.007, t(376.3) = 0.875, p = 0.382]. Depressive symptoms predicted increasing WMH severity [b = 0.012, t(265.9) = -3.291, p = 0.001], but not incident stroke/TIA (odds ratio = 0.995; CI 0.949-1.043; p = 0.820). When examined in separate models, depressive symptoms [b = -0.027, t(373.5) = -2.16, p = 0.032] and a history of stroke/TIA [b = -0.460, t(361.2) = -4.45, p < 0.001], but not WMH volume [b = 0.001, t(362.3) = -0.520, p = 0.603], predicted declines in cognition. When investigated in a combined model, a history of stroke/TIA remained a predictor of cognitive decline [b = -0.443, t(360.6) = -4.28, p < 0.001], whilst depressive symptoms did not [b = -0.012, t(359.7) = -0.96, p = 0.336].

CONCLUSIONS

This study is contrasted with previous prospective studies which indicate that depressive symptoms predict cognitive decline independently of vascular disease. Future research should focus on further exploring the vascular mechanisms underpinning the relationship between depressive symptoms and cognition.

Increased Diameters of the Internal Cerebral Veins and the Basal Veins of Rosenthal Are Associated with White Matter Hyperintensity Volume

BACKGROUND AND PURPOSE

White matter hyperintensities on T2-weighted MR imaging are typical in older adults and have been linked to several poor health outcomes, including cognitive impairment and Alzheimer disease. The presence and severity of white matter hyperintensities have traditionally been attributed to occlusive arteriopathy, but recent evidence also implicates deep medullary venule collagenosis and associated vasogenic edema. Historically, postmortem analyses have been the sole way to analyze cerebral veins, but SWI can be now used to examine cortical veins in vivo. The aim of the current study was to determine whether there is an association between the diameters of the large draining cerebral veins/sinuses and white matter hyperintensity volume.

MATERIALS AND METHODS

T2-weighted FLAIR and SWI were performed in 682 older adults without dementia (mean age, 73.9 ± 5.9 years; 59.1% women). Total and regional white matter hyperintensity volume was derived. We measured the diameters of 5 regions of the cerebral venous draining system: internal cerebral veins, basal veins of Rosenthal, superior sagittal sinus, vein of Galen, and straight sinus terminus.

RESULTS

Increased diameter of the internal cerebral veins was associated with greater total white matter hyperintensity volume (β = 0.09, P = .02) and regionally in the parietal (β = 0.10, P = .006), frontal (β = 0.09, P = .02), and temporal (β = 0.09, P = .02) lobes. Increased diameter of the basal veins of Rosenthal was associated with greater total (β = 0.10, P = .01), frontal (β = 0.11, P = .003), and temporal (β = 0.09, P = .02) white matter hyperintensity volume.

CONCLUSIONS

Our results suggest that the caliber of the internal cerebral veins and of the basal veins of Rosenthal relates to regional white matter disease.

The role of education in a vascular pathway to episodic memory: brain maintenance or cognitive reserve?

Educational attainment is associated with cognition among older adults, but this association is complex and not well understood. While associated with better cognition among healthy adults, more education predicts faster decline in older adults with cognitive impairment. Education may influence cognitive functioning through mechanisms involving brain maintenance (BM: reduced age-related pathology) or cognitive reserve (CR: altered pathology-cognition association). We examined evidence for each mechanism by quantifying main and interaction effects of education within a well-studied pathway involving systolic blood pressure, white matter hyperintensities (WMH), and episodic memory in 2 samples without dementia at the baseline (total N = 1136). There were no effects of education on systolic blood pressure or WMH, suggesting a lack of evidence for BM. In the sample less likely to progress to dementia, education attenuated the effect of WMH on memory at the baseline. In the sample more likely to progress to dementia, education exacerbated this effect at the baseline. These moderations provide evidence for a CR mechanism and are consistent with previous findings of faster decline once CR is depleted.

A Clinicopathological Investigation of White Matter Hyperintensities and Alzheimer's Disease Neuropathology

BACKGROUND

White matter hyperintensities (WMH) on magnetic resonance imaging (MRI) have been postulated to be a core feature of Alzheimer's disease. Clinicopathological studies are needed to elucidate and confirm this possibility.

OBJECTIVE

This study examined: 1) the association between antemortem WMH and autopsy-confirmed Alzheimer's disease neuropathology (ADNP), 2) the relationship between WMH and dementia in participants with ADNP, and 3) the relationships among cerebrovascular disease, WMH, and ADNP.

METHODS

The sample included 82 participants from the National Alzheimer's Coordinating Center's Data Sets who had quantitated volume of WMH from antemortem FLAIR MRI and available neuropathological data. The Clinical Dementia Rating (CDR) scale (from MRI visit) operationalized dementia status. ADNP+ was defined by moderate to frequent neuritic plaques and Braak stage III-VI at autopsy. Cerebrovascular disease neuropathology included infarcts or lacunes, microinfarcts, arteriolosclerosis, atherosclerosis, and cerebral amyloid angiopathy.

RESULTS

60/82 participants were ADNP+. Greater volume of WMH predicted increased odds for ADNP (p = 0.037). In ADNP+ participants, greater WMH corresponded with increased odds for dementia (CDR≥1; p = 0.038). WMH predicted cerebral amyloid angiopathy, microinfarcts, infarcts, and lacunes (ps < 0.04). ADNP+ participants were more likely to have moderate-severe arteriolosclerosis and cerebral amyloid angiopathy compared to ADNP-participants (ps < 0.04).

CONCLUSIONS

This study found a direct association between total volume of WMH and increased odds for having ADNP. In patients with Alzheimer's disease, FLAIR MRI WMH may be able to provide key insight into disease severity and progression. The association between WMH and ADNP may be explained by underlying cerebrovascular disease.

Validation of an Magnetic Resonance Imaging Acquisition and Review Protocol for Alzheimer's Disease and Related Disorders

Purpose

Magnetic resonance imaging (MRI) of the brain allows for the identification of structural lesions typical of Alzheimer's disease (AD), the main cause of dementia. However, to have a clinical impact, it is imperative that acquisition and reporting of this MRI-based evidence be standardized, ensuring the highest possible reliability and reproducibility. Our objective was to validate a systematic radiological MRI acquisition and review process in the context of AD.

Methods

We included 100 individuals with a suspicion of dementia due to AD for whom MRI were acquired using our proposed protocol of clinically achievable acquisitions and used a unified reading grid to gather semi-quantitative evidence guiding diagnostic. MRIs were read by 3 raters with different experience levels. Interrater reliability was measured using Cohen's kappa statistic.

Results

Interrater reliability average for lesions occupying space, hemorrhage, or ischemia, was respectively 0.754, 0.715, and 0.501. Average reliability of white matter hyperintensity burden (Fazekas), global cortical atrophy, and temporal lobe atrophy (Scheltens) scales was 0.687, 0.473, and 0.621 (right)/0.599 (left), respectively. The kappas for regional cortical atrophy (frontal, parietal, occipital, temporal, and posterior cingulum) varied from 0.281–0.678. The average MRI reading time varied between 1.43-5.22 minutes.

Conclusions

The presence of space occupying lesions, hemorrhagic or ischemic phenomena, and radiological scales have a good interrater reproducibility in MRI. Coupled with standardized acquisitions, such a protocol should be used when evaluating possible dementias, especially those due to probable AD.

Treatment of Radiation-Induced Cognitive Decline in Adult Brain Tumor Patients

OPINION STATEMENT

Patients with either primary or metastatic brain tumors quite often have cognitive impairment. Maintaining cognitive function is important to brain tumor patients and a decline in cognitive function is generally accompanied by a decline in functional independence and performance status. Cognitive decline can be a result of tumor progression, depression/anxiety, fatigue/sleep dysfunction, or the treatments they have received. It is our opinion that providers treating brain tumor patients should obtain pre-treatment and serial cognitive testing in their patients and offer mitigating and therapeutic interventions when appropriate. They should also support cognition-focused clinical trials.

Genetic influences on white matter and metabolism abnormal change in Alzheimer's disease: Meta-analysis for neuroimaging research on presenilin 1 mutation

Mutations in the presenilin1 (PSEN1) cause familial Alzheimer's disease (FAD), providing a special opportunity to study pre-symptomatic individuals who would be predicted to develop Alzheimer's disease (AD) in the future. However, whether presenilin1 (PSEN1) genotype and neuroimaging markers is a harbinger of AD remains controversial. We aimed to explore the association of PSEN1 genotype with neuroimaging markers of AD: white matter integrity, cerebral amyloid deposition and brain metabolism. We reviewed studies of diffusion tensor imaging (DTI), amyloid deposition and cerebral metabolism in patients with AD and control, in order to address the relative change of white matter microstructural associated with PSEN1 genotype. We performed a systematic meta-analysis and review of 11 cross-sectional studies identified in several database from 2008 to 2018 (n = 165). The pooled standard mean difference (SMD) value was calculated to estimate the association between PSEN1 and white matter change and brain metabolism. PSEN1 mutation carrier status was associated with mean diffusivity (MD) change (pooled SMD: 2.29; 95% CI 1.04 to 3.53; p < 0.001) and increased cerebral amyloid positron emission tomography tracer (pooled SMD: 3.78, 95% CI 1.04 to 6.53, p = 0.007). PSEN1 was not associated with white matter metabolism change (p = 0.069). PSEN1 was associated with mean diffusivity (MD) increase in DTI markers and decreased brain metabolism. Theses associations may suggest the potential role of the PSEN1 gene and imaging marker in Alzheimer's disease.

Interplay Between Macular Retinal Changes and White Matter Integrity in Early Alzheimer's Disease

This study aims to investigate the relationship between structural changes in the retina and white matter in the brain, in early Alzheimer's disease (AD). Twenty-three healthy controls (mean age = 63.4±7.5 years) and seventeen AD patients (mean age = 66.5±6.6 years) were recruited for this study. By combining two imaging techniques-optical coherence tomography and diffusion tensor imaging (DTI)-the association between changes in the thickness of individual retinal layers and white matter dysfunction in early AD was assessed. Retinal layers were segmented, and thickness measurements were obtained for each layer. DTI images were analyzed with a quantitative data-driven approach to evaluating whole-brain diffusion metrics, using tract-based spatial statistics. Diffusion metrics, such as fractional anisotropy, are markers for white matter integrity. Multivariate and partial correlation analyses evaluating the association between individual retinal layers thickness and diffusion metrics were performed. We found that axial diffusivity, indexing axonal integrity, was significantly reduced in AD (p = 0.016, Cohen's d = 1.004) while in the retina, only a marginal trend for significance was found for the outer plexiform layer (p = 0.084, Cohen's d = 0.688). Furthermore, a positive association was found in the AD group between fractional anisotropy and the inner nuclear layer thickness (p < 0.05, r = 0.419, corrected for multiple comparisons by controlling family-wise error rate). Our findings suggest that axonal damage in the brain dominates early on in this condition and shows an association with retinal structural integrity already at initial stages of AD. These findings are consistent with an early axonal degeneration mechanism in AD.

Differential Associations of Diastolic and Systolic Pressures With Cerebral Measures in Older Individuals With Mild Cognitive Impairment

BACKGROUND

Reports on the relative importance of the diastolic and systolic blood pressures (DBP and SBP) in age-related cognitive decline are mixed. Investigating the relation between DBP/SBP and functional and structural brain changes could elucidate which of the 2 measures is more critically important for brain function and, consequently, cognitive impairment.

METHODS

We investigated the association of SBP and DBP with cortical volume, cerebral blood flow (CBF), and white matter lesions (WML), in nondemented older adults with and without mild cognitive impairment (MCI; N = 265, 185 MCI, mean age = 64 years). Brachial blood pressure was measured twice while seated, and the average of the 2 measures was used. Cortical volume, gray matter (GM) CBF, and WML were estimated using T1-weighted imaging, arterial spin labeling, and fluid attenuation inversion recovery, respectively.

RESULTS

Reduced cortical volume was associated with elevated DBP (β= -0.18, P = 0.034) but not with SBP (β = -0.10, P = 0.206). GM CBF was associated with DBP (β = -0.13, P = 0.048) but not with SBP (β = -0.07, P = 0.275). Likewise, CBF within brain regions where MCI patients showed hypoperfusion were only associated with DBP (DBP: β = -0.17, P = 0.005; SBP: β = -0.09, P = 0.120). WML volume was associated with both DBP (β = 0.20, P = 0.005) and SBP (β = 0.30, P < 0.001). For all measures, there was no interaction between DBP/SBP and cognitive status, indicating that these associations were independent of the cognitive status.

CONCLUSIONS

Independently of the cognitive status, DBP is more critically important for GM volume and perfusion, whereas WML is associated with both blood pressures, likely reflecting long-term effect of hypertension and autoregulation dysfunction.

Using high-dimensional machine learning methods to estimate an anatomical risk factor for Alzheimer's disease across imaging databases

INTRODUCTION

The main goal of this work is to investigate the feasibility of estimating an anatomical index that can be used as an Alzheimer's disease (AD) risk factor in the Women's Health Initiative Magnetic Resonance Imaging Study (WHIMS-MRI) using MRI data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), a well-characterized imaging database of AD patients and cognitively normal subjects. We called this index AD Pattern Similarity (AD-PS) scores. To demonstrate the construct validity of the scores, we investigated their associations with several AD risk factors. The ADNI and WHIMS imaging databases were collected with different goals, populations and data acquisition protocols: it is important to demonstrate that the approach to estimating AD-PS scores can bridge these differences.

METHODS

MRI data from both studies were processed using high-dimensional warping methods. High-dimensional classifiers were then estimated using the ADNI MRI data. Next, the classifiers were applied to baseline and follow-up WHIMS-MRI GM data to generate the GM AD-PS scores. To study the validity of the scores we investigated associations between GM AD-PS scores at baseline (Scan 1) and their longitudinal changes (Scan 2 -Scan 1) with: 1) age, cognitive scores, white matter small vessel ischemic disease (WM SVID) volume at baseline and 2) age, cognitive scores, WM SVID volume longitudinal changes respectively. In addition, we investigated their associations with time until classification of independently adjudicated status in WHIMS-MRI.

RESULTS

Higher GM AD-PS scores from WHIMS-MRI baseline data were associated with older age, lower cognitive scores, and higher WM SVID volume. Longitudinal changes in GM AD-PS scores (Scan 2 - Scan 1) were also associated with age and changes in WM SVID volumes and cognitive test scores. Increases in the GM AD-PS scores predicted decreases in cognitive scores and increases in WM SVID volume. GM AD-PS scores and their longitudinal changes also were associated with time until classification of cognitive impairment. Finally, receiver operating characteristic curves showed that baseline GM AD-PS scores of cognitively normal participants carried information about future cognitive status determined during follow-up.

DISCUSSION

We applied a high-dimensional machine learning approach to estimate a novel AD risk factor for WHIMS-MRI study participants using ADNI data. The GM AD-PS scores showed strong associations with incident cognitive impairment and cross-sectional and longitudinal associations with age, cognitive function, cognitive status and WM SVID volume lending support to the ongoing validation of the GM AD-PS score.

Connectome-derived diffusion characteristics of the fornix in Alzheimer's disease

The fornix bundle is a major white matter pathway of the hippocampus. While volume of the hippocampus has been a primary imaging biomarker of Alzheimer's disease progression, recent research has suggested that the volume and microstructural characteristics of the fornix bundle connecting the hippocampus could add relevant information for diagnosing and staging Alzheimer's disease. Using a robust fornix bundle isolation technique in native diffusion space, this study investigated whether diffusion measurements of the fornix differed between normal older adults and Alzheimer's disease patients when controlling for volume measurements. Data were collected using high gradient multi-shell diffusion-weighted MRI from a Siemens CONNECTOM scanner in 23 Alzheimer's disease and 23 age- and sex-matched control older adults (age range = 53–92). These data were used to reconstruct a continuous fornix bundle in every participant's native diffusion space, from which tract-derived volumetric and diffusion metrics were extracted and compared between groups. Diffusion metrics included those from a tensor model and from a generalized q-sampling imaging model. Results showed no significant differences in tract-derived fornix volumes but did show altered diffusion metrics within tissue classified as the fornix in the Alzheimer's disease group. Comparisons to a manual tracing method indicated the same pattern of results and high correlations between the methods. These results suggest that in Alzheimer's disease, diffusion characteristics may provide more sensitive measures of fornix degeneration than do volume measures and may be a potential early marker for loss of medial temporal lobe connectivity.

•

An enhanced method for measurement of continuous fornix bundles is described.

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Diffusion characteristics of the fornix were degraded in Alzheimer's disease.

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Alzheimer's disease primarily affected the crus and body of the fornix.

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Diffusion differences were observed controlling for fornix volume differences.

Low carotid wall shear stress independently accelerates the progression of cognitive impairment and white matter lesions in the elderly

The association of hemodynamics with cognitive impairment and white matter lesions (WMLs) has come to the foreground in recent years. Six hundred eighty-nine elderly participants aged ≥60 years were eligible enrolled. After an average of 5.4 years follow-up, there was a significant decline in Mini-Mental State Examination (MMSE) scores and increases in total white matter hyperintensities (WMH), periventricular (P)WMH, and deep (D)WMH (P < 0.001). The participants were grouped by the tertiles of carotid mean wall shear stress (WSS). The decline in MMSE scores and the increases in total WMH, PWMH, and DWMH decreased from the lowest group to the highest group. There were significant differences between each group comparison (all P <0.05). Mean WSS was an independent and significant factor for the changes in MMSE scores, total WMH, PWMH, and DWMH after adjustment for confounders (P <0.001). The risk of developing cognitive impairment was higher in the lowest (hazard ratio: 2.753; 95% CI: 1.945 to 3.895; P < 0.001) and intermediate (hazard ratio: 1.531; 95% CI: 1.084 to 2.162; P = 0.015) groups than in the highest group after adjustment for confounders. Similar associations were yielded between peak WSS and the changes in MMSE scores, total WMH, PWMH, and DWMH. Our results indicated that carotid WSS is an independent factor for the progression of cognitive impairment and WMLs in the elderly. Low WSS significantly deteriorates the progression of cognitive impairment and WMLs.

Executive Functions in Healthy Older Adults Are Differentially Related to Macro- and Microstructural White Matter Characteristics of the Cerebral Lobes

Aging is associated with microstructural white matter (WM) changes. WM microstructural characteristics, measured with diffusion tensor imaging (DTI), are different in normal appearing white matter (NAWM) and WM hyperintensities (WMH). It is largely unknown how the microstructural properties of WMH are associated with cognition and if there are regional effects for specific cognitive domains. We therefore examined within 200 healthy older participants (a) differences in microstructural characteristics of NAWM and WMH per cerebral lobe; and (b) the association of macrostructural (WMH volume) and microstructural characteristics (within NAWM and WMH separately) of each lobe with measures of executive function and processing speed. Multi-modal imaging (i.e., T1, DTI, and FLAIR) was used to assess WM properties. The Stroop and the Trail Making Test were used to measure inhibition, task-switching (both components of executive function), and processing speed. We observed that age was associated with deterioration of white matter microstructure of the NAWM, most notably in the frontal lobe. Older participants had larger WMH volumes and lowest fractional anisotropy values within WMH were found in the frontal lobe. Task-switching was associated with cerebral NAWM volume and NAWM volume of all lobes. Processing speed was associated with total NAWM volume, and microstructural properties of parietal NAWM, the parietal WMH, and the temporal NAWM. Task-switching was related to microstructural properties of WMH of the frontal lobe and WMH volume of the parietal lobe. Our results confirm that executive functioning and processing speed are uniquely associated with macro- and microstructural properties of NAWM and WMH. We further demonstrate for the first time that these relationships differ by lobar region. This warrants the consideration of these distinct WM indices when investigating cognitive function.

Cognitive performance in patients with Mild Cognitive Impairment and Alzheimer's disease with white matter hyperintensities: An exploratory analysis

BACKGROUND

White matter hyperintensities (WMH) are commonly associated with vascular dementia and poor executive functioning. Notwithstanding, recent findings have associated WMH with Alzheimer's disease as well as other cognitive functions, but there is no consensus.

OBJECTIVE

This study aimed to verify the relationship between WMH and cognitive performance in Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) patients. The study also sought to identify cognitive and demographic/cultural factors that might explain variability of WMH.

METHODS

The sample was composed of 40 participants (18 MCI and 22 AD patients) aged ≥ 65 years. Spearman's correlation was performed among cognitive performance (memory, language, visuospatial ability, and executive function) and WMH evaluated by the Fazekas and ARWMC scales. Two stepwise linear regressions were carried out, one with cognitive and the other with demographic/cultural variables as predictors.

RESULTS

Only naming showed significant correlation with ARWMC. Fazekas score exhibited significant correlation with all cognitive domains evaluated. Fazekas score was better predicted by episodic visual memory and age.

CONCLUSION

This study found that the most relevant cognitive profile in MCI and AD patients with WMH was related to episodic memory. And, without taking clinical aspects into consideration, age was the best predictor of WMH.

Empty-nest-related psychological distress is associated with progression of brain white matter lesions and cognitive impairment in the elderly

This study evaluated the association between empty-nest-related psychological distress and the progression of white matter lesions (WMLs) and cognitive impairment in 219 elderly subjects aged 60 years or over. Psychological distress was assessed using the University of California at Los Angeles Loneliness Scale (UCLA-LS) and Geriatric Depression Scale (GDS) Short-Form. Cognitive function was evaluated using the MMSE and MoCA. White matter hyperintensities (WMH) were assessed using magnetic resonance imaging. After 5.2-year follow-up, the reductions in MMSE and MoCA scores and the increases in periventricular (P)WMH, deep (D)WMH, and total WMH volumes in the empty-nest elderly were greater than those in the non-empty-nest elderly (P < 0.05). The reduced MMSE and MoCA scores and increased volumes of PWMH and total WMH in the empty-nest elderly living alone were greater than those in the empty-nest elderly living with a spouse (P < 0.05). UCLA-LS and GDS scores were significantly and independently associated with reduced MMSE and MoCA scores and the increased volumes of PWMH, DWMH, and total WMH. The results indicate that empty-nest-related psychological distress is associated with progression of WMLs and cognitive impairment in the elderly.

Regional staging of white matter signal abnormalities in aging and Alzheimer's disease

White matter lesions, quantified as 'white matter signal abnormalities' (WMSA) on neuroimaging, are common incidental findings on brain images of older adults. This tissue damage is linked to cerebrovascular dysfunction and is associated with cognitive decline. The regional distribution of WMSA throughout the cerebral white matter has been described at a gross scale; however, to date no prior study has described regional patterns relative to cortical gyral landmarks which may be important for understanding functional impact. Additionally, no prior study has described how regional WMSA volume scales with total global WMSA. Such information could be used in the creation of a pathologic 'staging' of WMSA through a detailed regional characterization at the individual level. Magnetic resonance imaging data from 97 cognitively-healthy older individuals (OC) aged 52-90 from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study were processed using a novel WMSA labeling procedure described in our prior work. WMSA were quantified regionally using a procedure that segments the cerebral white matter into 35 bilateral units based on proximity to landmarks in the cerebral cortex. An initial staging was performed by quantifying the regional WMSA volume in four groups based on quartiles of total WMSA volume (quartiles I-IV). A consistent spatial pattern of WMSA accumulation was observed with increasing quartile. A clustering procedure was then used to distinguish regions based on patterns of scaling of regional WMSA to global WMSA. Three patterns were extracted that showed high, medium, and non-scaling with global WMSA. Regions in the high-scaling cluster included periventricular, caudal and rostral middle frontal, inferior and superior parietal, supramarginal, and precuneus white matter. A data-driven staging procedure was then created based on patterns of WMSA scaling and specific regional cut-off values from the quartile analyses. Individuals with Alzheimer's disease (AD) and mild cognitive impairment (MCI) were then additionally staged, and significant differences in the percent of each diagnostic group in Stages I and IV were observed, with more AD individuals residing in Stage IV and more OC and MCI individuals residing in Stage I. These data demonstrate a consistent regional scaling relationship between global and regional WMSA that can be used to classify individuals into one of four stages of white matter disease. White matter staging could play an important role in a better understanding and the treatment of cerebrovascular contributions to brain aging and dementia.

Differential Regional Distribution of Juxtacortical White Matter Signal Abnormalities in Aging and Alzheimer's Disease

BACKGROUND

White matter signal abnormalities (WMSA) (also known as 'hyperintensities') on MRI are commonly seen in normal aging and increases have been noted in Alzheimer's disease (AD), but whether there is a spatial specificity to these increases is unknown.

OBJECTIVE

To discern whether or not there is a spatial pattern of WMSA in the brains of individuals with AD that differs from those who exhibit cognitively healthy aging.

METHOD

Structural MRI data from the Alzheimer's Disease Neuroimaging Initiative public database were used to quantify WMSA in 35 regions of interest (ROIs). Regional measures were compared between cognitively healthy older controls (OC; n = 107) and individuals with a clinical diagnosis of AD (n = 127). Regional WMSA volume was also assessed in individuals with mild cognitive impairment (MCI; n = 74) who were 6, 12, and 24 months away from AD conversion.

RESULTS

WMSA volume was significantly greater in AD compared to OC in 24 out of 35 ROIs after controlling for age, and nine were significantly higher after normalizing for total WMSA. Regions with greater WMSA volume in AD included rostral frontal, inferior temporal, and inferior parietal WM. In MCI, frontal and temporal regions demonstrated significantly greater WMSA volume with decreasing time-to-AD-conversion.

DISCUSSION

Individuals with AD have greater regional volume of WMSA compared to OC regardless of age or total WMSA volume. Accumulation of regional WMSA is linked to time to AD conversion in individuals with MCI. These findings indicate WMSA is an important pathological component of AD development.

Structural MR Imaging in the Diagnosis of Alzheimer's Disease and Other Neurodegenerative Dementia: Current Imaging Approach and Future Perspectives

With the rise of aging population, clinical concern and research attention has shifted towards neuroimaging of dementia. The advent of 3T, magnetic resonance imaging (MRI) has permitted the anatomical imaging of neurodegenerative disease, specifically dementia, with improved resolution. Furthermore, more powerful techniques such as diffusion tensor imaging, quantitative susceptibility mapping, and magnetic transfer imaging have successfully emerged for the detection of micro-structural abnormalities. In the present review article, we provide a brief overview of Alzheimer's disease and explore recent neuroimaging developments in the field of dementia with an emphasis on structural MR imaging in order to propose a simple and easily applicable systematic approach to the imaging diagnosis of dementia.

Visceral adiposity predicts subclinical white matter hyperintensities in middle-aged adults

OBJECTIVE

Growing prevalence of neuropathology and cognitive impairment are emerging consequences of the obesity epidemic. Adiposity indices used in examining the relationships between obesity, neuropathology, and cognition vary substantially in the literature leading to incongruent findings. Our aim was to determine the anthropometric measures most strongly associated with early white matter disease and cognitive function at midlife.

METHOD

Multiple adiposity indices were measured in 126 adults aged 40-62 who also completed a magnetic resonance imaging (MRI) scan to quantify white matter disease and a cognitive test battery. Anthropometric indices of obesity were compared to image-based estimates of visceral adipose tissue with dual-energy X-ray absorptiometry (DEXA) as predictors of current white matter disease and cognitive function. We also explored sex as a potential moderator of these relationships.

RESULTS

Waist circumference (WC) was most strongly correlated with DEXA estimates of visceral adipose tissue (r=0.871, p<0.001). Increasing WC (β=0.231, p=0.034), percent body fat (β=0.230, p=0.045), and VAT (β=0.247, p=0.027) significantly predicted subclinical white matter hyperintensities in the absence of cognitive impairment after accounting for age, sex, years of education, and cardiovascular risk factors. Sex was not a significant moderator of any of the observed relationships.

CONCLUSIONS

Of the anthropometric indices used in this study, WC, BF, and VAT successfully predicted subclinical white matter disease in cognitively normal adults at midlife. Increasing VAT may independently insidiously affect cerebral white matter prior to detectable cognitive changes, necessitating early intervention.

Sleep Disordered Breathing and White Matter Hyperintensities in Community-Dwelling Elders

STUDY OBJECTIVES

To examine the association between markers of sleep-disordered breathing (SDB) and white matter hyperintensity (WMH) volume in an elderly, multiethnic, community-dwelling cohort.

METHODS

This is a cross-sectional analysis from the Washington Heights-Inwood Columbia Aging Project (WHICAP), a community-based epidemiological study of older adults. Structural magnetic resonance imaging was obtained starting in 2004; the Medical Outcomes Study-Sleep Scale (MOS-SS) was administered to participants starting in 2007. Linear regression models were used to assess the relationship between the two MOS-SS questions that measure respiratory dysfunction during sleep and quantified WMH volume among WHICAP participants with brain imaging.

RESULTS

A total of 483 older adults had both structural magnetic resonance imaging and sleep assessment. Self-reported SDB was associated with WMH. After adjusting for demographic and vascular risk factors, WMH volumes were larger in individuals with frequent snoring (β = 2.113, P = 0.004) and among those who reported waking short of breath or with headache (β = 1.862, P = 0.048).

CONCLUSIONS

In community-dwelling older adults, self-reported measures of SDB are associated with larger WMH volumes. The cognitive effects of SDB that are increasingly being recognized may be mediated at the small vessel level.