Periventricular White Matter Hyperintensities and Functional Decline

Alterations in structural integrity of superior longitudinal fasciculus III associated with cognitive performance in cerebral small vessel disease

BACKGROUND

This study aimed to investigate the alterations in structural integrity of superior longitudinal fasciculus subcomponents with increasing white matter hyperintensity severity as well as the relationship to cognitive performance in cerebral small vessel disease.

METHODS

110 cerebral small vessel disease study participants with white matter hyperintensities were recruited. According to Fazekas grade scale, white matter hyperintensities of each subject were graded. All subjects were divided into two groups. The probabilistic fiber tracking method was used for analyzing microstructure characteristics of superior longitudinal fasciculus subcomponents.

RESULTS

Probabilistic fiber tracking results showed that mean diffusion, radial diffusion, and axial diffusion values of the left arcuate fasciculus as well as the mean diffusion value of the right arcuate fasciculus and left superior longitudinal fasciculus III in high white matter hyperintensities rating group were significantly higher than those in low white matter hyperintensities rating group (p < 0.05). The mean diffusion value of the left superior longitudinal fasciculus III was negatively related to the Montreal Cognitive Assessment score of study participants (p < 0.05).

CONCLUSIONS

The structural integrity injury of bilateral arcuate fasciculus and left superior longitudinal fasciculus III is more severe with the aggravation of white matter hyperintensities. The structural integrity injury of the left superior longitudinal fasciculus III correlates to cognitive impairment in cerebral small vessel disease.

Baseline grey matter volumes and white matter hyperintensities predict decline in functional activities in older adults over a 5-year follow-up period

INTRODUCTION

Functional independence is an essential predictor of quality of life in aging, yet few accessible predictors of functional decline have been identified. This study examined associations between baseline structural neuroimaging markers and longitudinal functional status.

METHODS

Linear mixed effects models with follow-up time interaction terms related baseline grey matter volume and white matter hyperintensities (WMHs) to functional trajectory, adjusting for demographic and medical covariates. Subsequent models assessed interactions with cognitive status and apolipoprotein E (APOE) ε4 status.

RESULTS

Smaller baseline grey matter volumes, particularly in regions commonly affected by Alzheimer's disease (AD), and greater baseline WMHs were associated with faster functional decline over a mean 5-year follow-up. Effects were stronger in APOE-ε4 carriers on grey matter variables. Cognitive status interacted with most MRI variables.

DISCUSSION

Greater atrophy in AD-related regions and higher WMH burden at study entry were associated with faster functional decline, particularly among participants at increased risk of AD.

Periventricular rather than deep white matter hyperintensities mediate effects of hypertension on cognitive performance in the population-based 1000BRAINS study

OBJECTIVES

White matter hyperintensities (WMH) of presumed vascular origin are frequent in cerebral MRI of older people. They represent a sign of small vessel disease, are promoted by arterial hypertension, and relate to cognitive deficits. The interdependence of blood pressure and its treatment, WMH, and cognitive performance has not systematically been studied in population-based studies.

METHODS

Consequently, we analysed the interdependence of SBP, DBP, and antihypertensive medications, as well as BP/treatment category, with WMH and cognitive performance in 560 participants of the population-based 1000BRAINS study.

RESULTS

BP, its treatment, and BP/treatment category were moderately associated with cognitive performance (e.g. unadjusted β  = -0.10, 95%CI = -0.19 to -0.02 for the association of SBP (per standard deviation of 17.2 mmHg) with global cognition (per standard deviation of 0.5 z score)]. The harmful effect of BP on cognition was strongly mediated by periventricular hyperintensities (PVH), which were significantly associated with both SBP [ β  = 0.24, 95% CI = 0.14-0.34 (per 1-point-increase in Fazekas score)] and global cognition ( β  = -0.22, 95%CI =  -0.32 to -0.13). Thus, PVH mediated as much as 52% of the effects of SBP on cognitive performance. Mediation was less strong for deep white matter hyperintensities (DWMH, 16%), which showed less association with SBP ( β  = 0.14, 95% CI = 0.05-0.24) and global cognition ( β  = -0.12, 95%CI = -0.21 to -0.03). Regarding different cognitive domains, PVH most strongly mediated effects of SBP on nonverbal memory (94%) and executive function (81%).

CONCLUSION

Our results indicate that PVH may predispose to cognitive impairment associated with hypertension, especially in the domains of nonverbal memory and executive function.

Combined Score of Perivascular Space Dilatation and White Matter Hyperintensities in Patients with Normal Cognition, Mild Cognitive Impairment, and Dementia

Background and Objectives: Cerebral perivascular spaces (PVS) are part of the cerebral microvascular structure and play a role in lymphatic drainage and the removal of waste products from the brain. White matter hyperintensities (WMH) are hyperintense lesions on magnetic resonance imaging that are associated with cognitive impairment, dementia, and cerebral vascular disease. WMH and PVS are direct and indirect imaging biomarkers of cerebral microvascular integrity and health. In our research, we evaluated WMH and PVS enlargement in patients with normal cognition (NC), mild cognitive impairment (MCI), and dementia (D). Materials and Methods: In total, 57 participants were included in the study and divided into groups based on neurological evaluation and Montreal Cognitive Assessment results (NC group 16 participants, MCI group 29 participants, D group 12 participants). All participants underwent 3T magnetic resonance imaging. PVS were evaluated in the basal ganglia, centrum semiovale, and midbrain. WMHs were evaluated based on the Fazekas scale and the division between deep white matter (DWM) and periventricular white matter (PVWM). The combined score based on PVS and WMH was evaluated and correlated with the results of the MoCA. Results: We found statistically significant differences between groups on several measures. Centrum semiovale PVS dilatation was more severe in MCI and dementia group and statistically significant differences were found between D-MCI and D-NC pairs. PVWM was more severe in patients with MCI and dementia group, and statistically significant differences were found between D-MCI and D-NC pairs. Furthermore, we found statistically significant differences between the groups by analyzing the combined score of PVS dilatation and WMH. We did not find statistically significant differences between the groups in PVS dilation of the basal ganglia and midbrain and DWM hyperintensities. Conclusions: PVS assessment could become one of neuroimaging biomarkers for patients with cognitive decline. Furthermore, the combined score of WMH and PVS dilatation could facilitate diagnostics of cognitive impairment, but more research is needed with a larger cohort to determine the use of PVS dilatation and the combined score.

White matter hyperintensities-related cortical changes and correlation with mild behavioral impairment

PURPOSE

The aim of this study was to analyze cortical thickness and gray matter volume (GMV) changes in white matter hyperintensities (WMH) which were associated brain regions and their association with mild behavioral impairment (MBI) by means of voxel- and surface-based morphology (VBM and SBM).

METHODS

A total of 60 patients underwent 3T MRI scan and MBI checklist (MBI-C) assessment and were divided into two groups: lower WMH (LWMH) and higher WMH (HWMH). After adjusting for confounding factors i.e. age, gender, education, and total intracranial volume, we found a GMV decrease in the left anterior insula (AIns), right middle frontal gyrus, right central operculum, right fusiform gyrus, left cerebellum exterior, and thalamus proper in the HWMH group based VBM, while in the HWMH group based SBM we found cortical thickness decrease in the left lingual, right posterior cingulate cortex (rPCC), right precentral, left superior frontal, right medial orbitofrontal gyrus, and left pars opercularis.

RESULTS

The HWMH group had higher MBI-C scores. The GMV in the left AIns and thalamus proper and the thickness of rPCC negatively correlated with the MBI-C scores. The mediation analysis suggested that WMH may partially mediate MBI-C scores by reducing the GMV and cortical thickness of the mentioned brain regions.

CONCLUSIONS

In WMH patients, the occurrence of MBI is associated with atrophy of gray matter and cortex. The occurrence of MBI may be partially mediated by WMH through gray matter and cortical atrophy. It provides a new insight into the relationship between WMH and dementia.

Amide Proton Transfer MRI Could Be Used to Evaluate the Pathophysiological Status of White Matter Hyperintensities

BACKGROUND

The pathophysiology of white matter hyperintensities (WMH) remains unclear, investigations of amide proton transfer (APT) signals in WMH disease may provide relevant pathophysiological information.

PURPOSE

To evaluate the APT signals differences and heterogeneity of WMH and adjacent normal-appearing white matter (NAWM) at different Fazekas grades and different locations.

STUDY TYPE

Prospective.

POPULATION

In all, 180 WMH patients (age, 40-76; male/female, 77/103) and 59 healthy controls (age, 42-70; male/female, 23/36).

FIELD STRENGTH/SEQUENCE

A 3 T; 3D fluid-attenuated inversion recovery (FLAIR), 3D APT-weighted (APTw).

ASSESSMENT

The mean APTw values (APTw_mean ) and the APTw signals heterogeneity (APTw_max-min ) among different grades WMH and NAWM and the APTw_mean of the same grade deep WMH (DWMH) and paraventricular WMH (PWMH) were calculated and compared. Regions of interests were delineated on WMH lesions, NAWM and healthy white matter.

STATISTICAL TESTS

One-way analysis of variance (ANOVA); independent sample t test; Chi-square test. Significance level: P < 0.05.

RESULTS

APTw_mean among different grade WMH (from grade 0 to 3, 0.58 ± 0.14% vs. 0.29 ± 0.23% vs. 0.37 ± 0.24% vs. 0.61 ± 0.22%, respectively) were significantly different except between grade 1 and 2 (P = 0.27) and between grade 0 and 3 (P = 0.97). The differences in APTw_mean between WMH and NAWM were significant (WMH vs. NAWM from grade 1 to 3, 0.29% ± 0.23% vs. 0.55% ± 0.27%; 0.37% ± 0.24% vs. 0.59% ± 0.22%; 0.61% ± 0.22% vs. 0.42% ± 0.24%, respectively). Lower APTw_mean values were found only in grade 3 NAWM than other grades NAWM and controls. The APTw_max-min values of grade 1-3 WMH (0.38% ± 0.27% vs. 0.51% ± 0.31% vs. 0.67% ± 0.34%, respectively) were significantly different. Higher APT_mean values were found only in grade 2 PWMH (0.47% ± 0.22% vs. 0.32% ± 0.24%).

DATA CONCLUSION

Significant differences of APT signals were found in WMH of different Fazekas grades and different locations.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 3.

Peak ependymal cell stretch overlaps with the onset locations of periventricular white matter lesions

Deep and periventricular white matter hyperintensities (dWMH/pvWMH) are bright appearing white matter tissue lesions in T2-weighted fluid attenuated inversion recovery magnetic resonance images and are frequent observations in the aging human brain. While early stages of these white matter lesions are only weakly associated with cognitive impairment, their progressive growth is a strong indicator for long-term functional decline. DWMHs are typically associated with vascular degeneration in diffuse white matter locations; for pvWMHs, however, no unifying theory exists to explain their consistent onset around the horns of the lateral ventricles. We use patient imaging data to create anatomically accurate finite element models of the lateral ventricles, white and gray matter, and cerebrospinal fluid, as well as to reconstruct their WMH volumes. We simulated the mechanical loading of the ependymal cells forming the primary brain-fluid interface, the ventricular wall, and its surrounding tissues at peak ventricular pressure during the hemodynamic cycle. We observe that both the maximum principal tissue strain and the largest ependymal cell stretch consistently localize in the anterior and posterior horns. Our simulations show that ependymal cells experience a loading state that causes the ventricular wall to be stretched thin. Moreover, we show that maximum wall loading coincides with the pvWMH locations observed in our patient scans. These results warrant further analysis of white matter pathology in the periventricular zone that includes a mechanics-driven deterioration model for the ventricular wall.

Machine learning-based estimation of cognitive performance using regional brain MRI markers: the Northern Manhattan Study

High dimensional neuroimaging datasets and machine learning have been used to estimate and predict domain-specific cognition, but comparisons with simpler models composed of easy-to-measure variables are limited. Regularization methods in particular may help identify regions-of-interest related to domain-specific cognition. Using data from the Northern Manhattan Study, a cohort study of mostly Hispanic older adults, we compared three models estimating domain-specific cognitive performance: sociodemographics and APOE ε4 allele status (basic model), the basic model and MRI markers, and a model with only MRI markers. We used several machine learning methods to fit our regression models: elastic net, support vector regression, random forest, and principal components regression. Model performance was assessed with the RMSE, MAE, and R² statistics using 5-fold cross-validation. To assess whether prediction models with imaging biomarkers were more predictive than prediction models built with randomly generated biomarkers, we refit the elastic net models using 1000 datasets with random biomarkers and compared the distribution of the RMSE and R² in models using these random biomarkers to the RMSE and R² from observed models. Basic models explained ~ 31-38% of the variance in domain-specific cognition. Addition of MRI markers did not improve estimation. However, elastic net models with only MRI markers performed significantly better than random MRI markers (one-sided P < .05) and yielded regions-of-interest consistent with previous literature and others not previously explored. Therefore, structural brain MRI markers may be more useful for etiological than predictive modeling.

Predicted disconnectome associated with progressive periventricular white matter ischemia

We used a virtual lesion DTI fiber tracking approach with healthy subject DTI data and simulated periventricular white matter (PVWM) lesion masks to predict the sequence of connectivity changes associated with progressive PVWM ischemia. We found that the optic radiations, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corpus callosum, temporopontine tract and fornix were affected in early simulated ischemic injury, and that the connectivity of subcortical, cerebellar, and visual regions were significantly disrupted with increasing simulated lesion severity. The results of this study provide insights into the spatial-temporal changes of the brain structural connectome under progressive PVWM ischemia. The virtual lesion approach provides a meaningful proxy to the spatial-temporal changes of the brain's structural connectome and can be used to further characterize the cognitive sequelae of progressive PVWM ischemia in both normal aging and dementia.

Differential Effects of Serum Lipoprotein-Associated Phospholipase A2 on Periventricular and Deep Subcortical White Matter Hyperintensity in Brain

Background and Purpose: Serum level of lipoprotein-associated phospholipase A2 (Lp-PLA2) was associated with white matter hyperintensity (WMH). There were differences in the anatomical structure and pathophysiological mechanism between periventricular WMH (PVWMH) and deep subcortical WMH (DSWMH). In this study, we aimed to investigate the effects of serum Lp-PLA2 on the PVWMH and DSWMH. Methods: In total, 711 Chinese adults aged ≥45 years with cranial magnetic resonance imaging (MRI) were recruited in this cross-sectional study, who had received physical examinations in the Department of Neurology, the Affiliated Jiangning Hospital of Nanjing Medical University due to dizziness and headaches between January 2016 and July 2019. Enzyme linked immunosorbent assay (ELISA) was utilized to determine the serum Lp-PLA2. Fazekas scale was used to measure the severity of PVWMH (grade 0-3) and DSWMH (grade 0-3) on MRI scans. Ordinal regression analysis was carried out to investigate the relationship between serum Lp-PLA2 and PVWMH or DSWMH. Results: Finally, 567 cases were included in this study. The average level of serum Lp-PLA2 was 213.35±59.34 ng/ml. There were statistical differences in the age, hypertension, diabetes mellitus, atrial fibrillation, lacunar infarction, Lp-PLA2 grade, creatinine, Hcy, and H-CRP (P < 0.05) in PVWMH groups. Ordinal regression analysis indicated that there was a lower risk of PVWMH in the patients with normal and moderately elevated serum Lp-PLA2 compared with those with significantly elevated serum Lp-PLA2 after adjusting age, hypertension, diabetes mellitus, atrial fibrillation, lacunar infarction, Cr, Hcy, and H-CRP. In addition, PVWMH was correlated to advanced age, hypertension, diabetes mellitus, and lacunar infarction. After adjusting for confounding factors, DSWMH was correlated to advanced age and lacunar infarction. There was no correlation between serum Lp-PLA2 and DSWMH. Conclusions: Serum Lp-PLA2 was closely associated with the pathogenesis of PVWMH rather than DSWMH. There might be different pathological mechanisms between PVWMH and DSWMH.

Cholinergic White Matter Lesions, AD-Signature Cortical Thickness, and Change in Cognition: The Northern Manhattan Study

BACKGROUND

How cerebrovascular disease and neurodegeneration affect each other to impact cognition is not yet known. We aimed to test whether Alzheimer's disease-signature (AD) cortical thickness mediates the association between cholinergic white matter lesion load and change in domain-specific cognition.

METHODS

Clinically stroke-free participants from the Northern Manhattan Study with both regional white matter hyperintensity volume (WMHV) and gray matter measurements were included (N = 894). Tract-specific WMHVs were quantified through FSL using the Johns Hopkins University white matter tract atlas. We used Freesurfer 5.1 to estimate regional cortical thickness. We fit structural equation models, including multiple indicator latent change score models, to examine associations between white matter hyperintensity volume (WMHV) in cholinergic tracts, AD-signature region cortical thickness (CT), and domain-specific cognition.

RESULTS

Our sample (N = 894) had a mean (SD) age = 70 (9) years, years of education = 10 (5), 63% women, and 67% Hispanics/Latinos. Greater cholinergic WMHV was significantly related to worse processing speed at baseline (standardized β = -0.17, SE = 0.05, p = .001) and over time (standardized β = -0.28, SE = 0.09, p = .003), with a significant indirect effect of AD-signature region CT (baseline: standardized β = -0.02, SE = 0.01, p = .023; change: standardized β = -0.03, SE = 0.02, p = .040).

CONCLUSIONS

Cholinergic tract WMHV is associated with worse processing speed, both directly and indirectly through its effect on AD-signature region CT.

Elevated Circulating Microparticle Subpopulations in Incidental Cerebral White Matter Hyperintensities: A Multimodal Study

Asymptomatic (or "silent") manifestations of cerebral small vessel disease (CSVD) are widely recognized through incidental findings of white matter hyperintensities (WMHs) as a result of magnetic resonance imaging (MRI). This study aims to examine the potential associations of surrogate markers for the evaluation of white matter integrity in CSVD among asymptomatic individuals through a battery of profiling involving QRISK2 cardiocerebrovascular risk prediction, neuroimaging, neurocognitive evaluation, and microparticles (MPs) titers. Sixty asymptomatic subjects (mean age: 39.83 ± 11.50 years) with low to moderate QRISK2 scores were recruited and underwent neurocognitive evaluation for memory and cognitive performance, peripheral venous blood collection for enumeration of selected MPs subpopulations, and 3T MRI brain scan with specific diffusion MRI (dMRI) sequences inclusive of diffusion tensor imaging (DTI). WMHs were detected in 20 subjects (33%). Older subjects (mean age: 46.00 ± 12.00 years) had higher WMHs prevalence, associated with higher QRISK2 score and reduced processing speed. They also had significantly higher mean percentage of platelet (CD62P)- and leukocyte (CD62L)-derived MPs. No association was found between reduced white matter integrity-especially at the left superior longitudinal fasciculus (LSLF)-with age and neurocognitive function; however, LSLF was associated with higher QRISK2 score, total MPs, and CD62L- and endothelial cell-derived MPs (CD146). Therefore, this study establishes these multimodal associations as potential surrogate markers for "silent" CSVD manifestations in the well-characterized cardiocerebrovascular demographic of relatively young, neurologically asymptomatic adults. Furthermore, to the best of our knowledge, this study is the first to exhibit elevated MP counts in asymptomatic CSVD (i.e., CD62P and CD62L), which warrants further delineation.

The association of white matter hyperintensities with stroke outcomes and antiplatelet therapy in minor stroke patients

Background

To characterize the severity and distribution of white matter hyperintensities (WMHs) and to assess the relationship of WMHs with initial stroke severity, 3-month functional outcome, stroke recurrence and response to antiplatelet therapies.

Methods

In Clopidogrel High-risk Patients with Acute Nondisabling Cerebrovascular Events (CHANCE) trial, 787 minor stroke patients with baseline magnetic resonance imaging (MRI) information were included in this analysis. Deep and periventricular WMHs (DWMHs and PVWMHs) were rated using the Fazekas scale and categorized into mild (grades 0–2), moderate (grades 3–4) and severe (grades 5–6). Multivariable logistic regression was used to examine the associations between WMHs severities and outcomes, including initial stroke severity by the National Institutes of Health Stroke Scale (NIHSS) scores, 3-month functional outcome by modified Rankin Scale (mRS), and stroke recurrence. Cox proportional hazards model was used to assess the treatment-by-subgroup interaction effect.

Results

Among the 787 patients in this analysis, 432 (54.9%) had moderate or severe WMHs (3-6). Compared with mild WMHs, the adjusted odds ratio (OR) of severe WMHs for risk of higher NIHSS was 2.10, 95% confidence interval (CI), 1.26–3.48 (P=0.004). Both severities of SDWMHs (OR 1.66; 95% CI, 1.15–2.40; P=0.007) and PVWMHs (OR 1.47; 95% CI, 1.02–2.10; P=0.04) were associated with higher NIHSS scores. There were no statistically significant associations of WMHs with 3-month functional outcome and stroke recurrence. There were no significant interactions between WMHs and antiplatelet therapy.

Conclusions

In patients with minor stroke, both SDWMHs and PVWMHs might related with initial stroke severity. No interaction was detected between the severity of WMHs and antiplatelet treatment.

Diastolic Blood Pressure Is Associated With Regional White Matter Lesion Load: The Northern Manhattan Study

Background and Purpose- Few studies have examined the separate contributions of systolic blood pressure and diastolic blood pressures (DBP) on subclinical cerebrovascular disease, especially using the 2017 American College of Cardiology/American Heart Association Blood Pressure Guidelines. Furthermore, associations with region-specific white matter hyperintensity volume (WMHV) are underexplored. Methods- Using data from the NOMAS (Northern Manhattan Study), a prospective cohort study of stroke risk and cognitive aging, we examined associations between systolic blood pressure and DBP, defined by the 2017 American College of Cardiology/American Heart Association guidelines, with regional WMHV. We used a linear mixed model approach to account for the correlated nature of regional brain measures. Results- The analytic sample (N=1205; mean age 64±8 years) consisted of 61% women and 66% Hispanics/Latinos. DBP levels were significantly related to WMHV differentially across regions (P for interaction<0.05). Relative to those with DBP 90+ mm Hg, participants with DBP <80 mm Hg had 13% lower WMHV in the frontal lobe (95% CI, -21% to -3%), 11% lower WMHV in the parietal lobe (95% CI, -19% to -1%), 22% lower WMHV in the anterior periventricular region (95% CI, -30% to -14%), and 16% lower WMHV in the posterior periventricular region (95% CI, -24% to -6%). Participants with DBP 80 to 89 mm Hg also exhibited about 12% (95% CI, -20% to -3%) lower WMHV in the anterior periventricular region and 9% (95% CI, -18% to -0.4%) lower WMHV in the posterior periventricular region, relative to participants with DBP 90≥ mm Hg. Post hoc pairwise t tests showed that estimates for periventricular WMHV were significantly different from estimates for temporal WMHV (Holms stepdown-adjusted P<0.05). Systolic blood pressure was not strongly related to regional WMHV. Conclusions- Lower DBP levels, defined by the 2017 American College of Cardiology/American Heart Association guidelines, were related to lower white matter lesion load, especially in the periventricular regions relative to the temporal region.

Differential Impact of Plasma Homocysteine Levels on the Periventricular and Subcortical White Matter Hyperintensities on the Brain

Background: The clinical significance of cerebral white matter hyperintensities (WMH) on brain magnetic resonance imaging (MRI) has recently increased, and recognized now as a risk factor for future stroke and dementia. High levels of plasma homocysteine (Hcyt) are associated with cerebral WMH. Recent studies suggest a different anatomy and physiology in the arteriolar system may be supplied to the periventricular and deep subcortical white matter. We hypothesize that plasma Hcyt levels have differing impacts on periventricular WMH (PVWMH) than on deep subcortical WMH (DSWMH).

Methods: We evaluated plasma Hcyt levels from 937 neurologically healthy participants. The severity of PVWMH and DSWMH was evaluated by the use of a manual grading scale. Moderate to severe PVWMH and DSWMH levels were defined when the Fazekas score was two or three, respectively. Predominant PVWMH (pred-PVWMH) and predominant DSWMH (pred-DSWMH) were defined as having a difference of Fazekas score between PVWMH and DSWMH of two or more. Other confounding variables including age, sex, vascular risk factors, and estimated glomerular filtration rate (eGFR) were also analyzed.

Results: Logistic regression revealed that, after adjusting for the confounding variables, PVWMH was associated with old age, hypertension, diabetes mellitus, low eGFR, and high plasma Hcyt levels. DSWMH was associated with old age, hypertension, and hypercholesterolemia but not with plasma Hcyt levels. Plasma Hcyt levels were associated with pred-PVWMH but not with pred-DSWMH.

Conclusions: High plasma Hcyt levels are strongly associated with the development of PVWMH but not DSWMH. Our results suggest the possibility that different pathogeneses exist for PVWMH and DSWMH and that dysregulated Hcyt metabolism associated with the development of PVWMH.

Neuroimaging of Cerebral Small Vessel Disease and Age-Related Cognitive Changes

Subclinical cerebrovascular disease is frequently identified in neuroimaging studies and is thought to play a role in the pathogenesis of cognitive disorders. Identifying the etiologies of different types of lesions may help investigators differentiate between age-related and pathological cerebrovascular damage in cognitive aging. In this review article, we aim to describe the epidemiology and etiology of various brain magnetic resonance imaging (MRI) measures of vascular damage in cognitively normal, older adult populations. We focus here on population-based prospective cohort studies of cognitively unimpaired older adults, as well as discuss the heterogeneity of MRI findings and their relationships with cognition. This review article emphasizes the need for a better understanding of subclinical cerebrovascular disease in cognitively normal populations, in order to more effectively identify and prevent cognitive decline in our rapidly aging population.

Characterizing the Penumbras of White Matter Hyperintensities and Their Associations With Cognitive Function in Patients With Subcortical Vascular Mild Cognitive Impairment

Normal-appearing white matter (NAWM) surrounding white matter hyperintensities (WMHs), frequently known as the WMH penumbra, is associated with subtle white matter injury and has a high risk for future conversion to WMHs. The goal of this study was to define WMH penumbras and to further explore whether the diffusion and perfusion parameters of these penumbras could better reflect cognitive function alterations than WMHs in subjects with subcortical vascular mild cognitive impairment (svMCI). Seventy-three svMCI subjects underwent neuropsychological assessments and 3T MRI scans, including diffusion tensor imaging (DTI) and arterial spin labeling (ASL). To determine the extent of cerebral blood flow (CBF) and DTI penumbras. A NAWM layer mask was generated for periventricular WMHs (PVWMHs) and deep WMHs (DWMHs) separately. Mean values of CBF, fractional anisotropy (FA), mean diffusivity (MD) within the WMHs and their corresponding NAWM layer masks were computed and compared using paired t-tests. Pearson's partial correlations were used to assess the relations of the mean CBF, FA, and MD values within the corresponding penumbras with composite z-scores of global cognition and four cognitive domains controlling for age, sex, and education. For both PVWMHs and DWMHs, the CBF penumbras were wider than the DTI penumbras. Only the mean FA value of the PVWMH-FA penumbra was correlated with the composite z-scores of global cognition before correction (r = 0.268, p = 0.024), but that correlation did not survive after correcting the p-value for multiple comparisons. Our findings showed extensive white matter perfusion disturbances including white matter tissue, both with and without microstructural alterations. The imaging parameters investigated, however, did not correlate to cognition.

Prospective Memory Loss and Related White Matter Changes in Patients with Amnestic Mild Cognitive Impairment

Background and Purpose

Prospective memory (PM) has a known relationship with frontal function, and PM decline has been observed in amnestic mild cognitive impairment (aMCI). Cerebral small vessel disease, as evidenced by white matter hyperintensities (WMHs), is linked to frontal dysfunction. This study was undertaken to evaluate the relationship between PM decline and WMHs in patients with aMCI.

Methods

Of 74 enrollees with aMCI, 69 completed this prospective study. We compared total scores and sub-scores of the Prospective and Retrospective Memory Questionnaire (PRMQ) administered at baseline and 3 months later, stratifying patients by degree of WMHs.

Results

A significant decline was seen in PRMQ total scores and PM scores at the 3-month mark in patients with moderate (vs. mild) degrees of WMHs (-2.8±7.2 vs. 0.2±7.1; p=0.032). In addition, patients with moderate (vs. mild) degrees of deep WMHs (DWMHs) showed greater PM decline, whereas PM loss in patients with mild, moderate, or severe degrees of periventricular WMHs (PVWMHs) did not differ significantly.

Conclusions

Findings of this study indicate that the burden of WMHs is consistently implicated in PM deterioration experienced by patients with aMCI, and signifies greater PM decline, especially in instances of extensive DWMHs. Greater attention to the change of PM is therefore needed in aMCI patients with WMHs.

Functional Trajectories, Cognition, and Subclinical Cerebrovascular Disease

BACKGROUND AND PURPOSE

Cognition and education influence functional trajectories, but whether associations differ with subclinical brain infarcts (SBI) or white matter hyperintensity volume (WMHV) is unknown. We hypothesized that SBI and WMHV moderated relationships between cognitive performance and education and functional trajectories.

METHODS

A total of 1290 stroke-free individuals underwent brain magnetic resonance imaging and were followed for 7.3 years (mean) with annual functional assessments with the Barthel index (range, 0-100). Magnetic resonance imaging measurements included pathology-informed SBI (PI-SBI) and WMHV (% total cranial volume). Generalized estimating equation models tested associations between magnetic resonance imaging variables and baseline Barthel index and change in Barthel index, adjusting for demographic, vascular, cognitive, and social risk factors, and stroke and myocardial infarction during follow-up. We tested interactions among education level, baseline cognitive performance (Mini-Mental State score), and functional trajectories and ran models stratified by levels of magnetic resonance imaging variables.

RESULTS

Mean age was 70.6 (SD, 9.0) years; 19% had PI-SBI, and mean WMHV was 0.68%. Education did not modify associations between cognition and functional trajectories. PI-SBI modified associations between cognition and functional trajectories (P=0.04) with a significant protective effect of better cognition on functional decline seen only in those without PI-SBI. There was no significant interaction for WMHV (P=0.8). PI-SBI, and greater WMHV, were associated with 2- to 3-fold steeper functional decline, holding cognition constant.

CONCLUSIONS

PI-SBI moderated the association between cognition and functional trajectories, with 3-fold greater decline among those with PI-SBI (compared with no PI-SBI) and normal baseline cognition. This highlights the strong and independent association between subclinical markers and patient-centered trajectories over time.