Extent and distribution of white matter hyperintensities in normal aging, MCI, and AD

Collagenosis of the Deep Medullary Veins: An Underrecognized Pathologic Correlate of White Matter Hyperintensities and Periventricular Infarction?

White matter hyperintensities (WMH) are prevalent. Although arteriolar disease has been implicated in their pathogenesis, venous pathology warrants consideration. We investigated relationships of WMH with histologic venous, arteriolar and white matter abnormalities and correlated findings with premortem neuroimaging. Three regions of periventricular white matter were sampled from archived autopsy brains of 24 pathologically confirmed Alzheimer disease (AD) and 18 age-matched nonAD patients. Using trichrome staining, venous collagenosis (VC) of periventricular veins (<150 µm in diameter) was scored for severity of wall thickening and occlusion; percent stenosis by collagenosis of large caliber (>200 µm) veins (laVS) was measured. Correlations were made between WMH in premortem neuroimaging and vascular and white matter pathology. We found greater VC (U(114) = 2092.5, p = 0.005 and U(114) = 2121.5, p = 0.002 for small and medium caliber veins, respectively) and greater laVS (t(110) = 3.46, p = 0.001) in patients with higher WMH scores; WMH scores correlated with VC (rs(114) = 0.27, p = 0.004) and laVS (rs(110) = 0.38, p < 0.001). By multiple linear regression analysis, the strongest predictor of WMH score was laVS (β = 0.338, p < 0.0001). VC was frequent in patients with periventricular infarcts identified on imaging. We conclude that periventricular VC is associated with WMH in both AD and nonAD patients and the potential roles of VC in WMH pathogenesis merit further study.

Abdominal obesity and white matter microstructure in midlife

The aging U.S. population and the recent rise in the prevalence of obesity are two phenomena of great importance to public health. In addition, research suggests that midlife body mass index (BMI) is a risk factor for dementia, a particularly costly disease, in later life. BMI could influence brain health by adversely impacting cerebral white matter. Recently, greater BMI has been associated with lower white matter fractional anisotropy (FA), an index of tissue microstructure, as measured by diffusion-tensor imaging in midlife. The aim of this study was to investigate the role of abdominal obesity, the most metabolically active adipose tissue compartment, and white matter microstructure in midlife. Community dwelling participants (N = 168) between the ages of 40-62 underwent MRI scanning at 3T and a general health assessment. Inferences were made on whole brain white matter tracts using full-tensor, high-dimension normalization, and tract-based spatial statistics. Higher waist circumference was associated with higher FA, indicating more directional diffusion in several white matter tracts controlling for age, sex, triglycerides, systolic blood pressure, fasting glucose, and HDL-cholesterol. Post hoc analysis revealed that greater waist circumference was associated with lower axial diffusivity, indicating lower parallel diffusion; lower radial diffusivity, indicating lower perpendicular diffusion; and lower mean diffusivity, indicating restricted diffusion. This is the first study to report a positive relationship between obesity and FA, indicating a more complicated view of this relationship in the aging brain. Hum Brain Mapp 38:3337-3344, 2017. © 2017 Wiley Periodicals, Inc.

Exome-sequencing in a large population-based study reveals a rare Asn396Ser variant in the LIPG gene associated with depressive symptoms

Despite a substantial genetic component, efforts to identify common genetic variation underlying depression have largely been unsuccessful. In the current study we aimed to identify rare genetic variants that might have large effects on depression in the general population. Using high-coverage exome-sequencing, we studied the exonic variants in 1265 individuals from the Rotterdam study (RS), who were assessed for depressive symptoms. We identified a missense Asn396Ser mutation (rs77960347) in the endothelial lipase (LIPG) gene, occurring with an allele frequency of 1% in the general population, which was significantly associated with depressive symptoms (P-value=5.2 × 10^-08, β=7.2). Replication in three independent data sets (N=3612) confirmed the association of Asn396Ser (P-value=7.1 × 10^-03, β=2.55) with depressive symptoms. LIPG is predicted to have enzymatic function in steroid biosynthesis, cholesterol biosynthesis and thyroid hormone metabolic processes. The Asn396Ser variant is predicted to have a damaging effect on the function of LIPG. Within the discovery population, carriers also showed an increased burden of white matter lesions (P-value=3.3 × 10^-02) and a higher risk of Alzheimer's disease (odds ratio=2.01; P-value=2.8 × 10^-02) compared with the non-carriers. Together, these findings implicate the Asn396Ser variant of LIPG in the pathogenesis of depressive symptoms in the general population.

Impact of frontal white matter hyperintensity on instrumental activities of daily living in elderly women with Alzheimer disease and amnestic mild cognitive impairment

Background

Instrumental activities of daily living (IADL) start to decline during the progression of amnestic mild cognitive impairment (aMCI) to Alzheimer disease (AD). Cognitive and physical decline are involved in the loss of functional independence. However, little is known about AD-related neural change that leads to IADL impairment. The purpose of this study was to clarify the effects of regional white matter hyperintensity (WMH) on IADL impairment in persons with AD and aMCI.

Methods

The participants were 347 female subjects aged 65–85 years diagnosed with AD (n = 227), aMCI (n = 44) or normal cognition (n = 76). IADL was assessed by the Lawton Index. Cognition, mood and mobility function were evaluated by comprehensive geriatric assessment batteries. WMH and brain atrophy were analyzed with brain magnetic resonance imaging, using an automatic segmentation program. Regional WMH was measured in the frontal, temporal, occipital and parietal lobes.

Results

Ability to carry out IADL of shopping, food preparation, mode of transportation, responsibility for own medication, and ability to handle finances was obviously impaired in the early stage of AD. Frontal WMH was specifically associated with disability to do shopping and food preparation even after adjusting for several confounders including brain atrophy.

Conclusions

IADL subcategories were differentially impaired along with cognitive status in persons with AD and aMCI. Frontal WMH was an important predictor of impaired ability to do shopping and food preparation. A preventive strategy for WMH might lead to suppression of IADL disability and slow the progression of AD.

An investigation of cerebrovascular lesions in dementia with Lewy bodies compared to Alzheimer's disease

INTRODUCTION

Cerebrovascular lesions on MRI are common in Alzheimer's disease (AD) dementia, but less is known about their frequency and impact on dementia with Lewy bodies (DLB).

METHODS

White-matter hyperintensities (WMHs) and infarcts on MRI were assessed in consecutive DLB (n = 81) and AD dementia (n = 240) patients and compared to age-matched and sex-matched cognitively normal subjects (CN) from a population-based cohort.

RESULTS

DLB had higher WMH volume compared to CN, and WMH volume was higher in the occipital and posterior periventricular regions in DLB compared to AD. Higher WMH volume was associated with history of cardiovascular disease and diabetes but not with clinical disease severity in DLB. Frequency of infarcts in DLB was not different from CN and AD dementia.

DISCUSSION

In DLB, WMH volume is higher than AD and CN and appears to be primarily associated with history of vascular disease.

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.

White matter hyperintensities correlate to cognition and fiber tract integrity in older adults with HIV

Our aim was to examine the clinical relevance of white matter hyperintensities (WMH) in HIV. We used an automated approach to quantify WMH volume in HIV seropositive (HIV+; n = 65) and HIV seronegative (HIV-; n = 29) adults over age 60. We compared WMH volumes between HIV+ and HIV- groups in cross-sectional and multiple time-point analyses. We also assessed correlations between WMH volumes and cardiovascular, HIV severity, cognitive scores, and diffusion tensor imaging variables. Serostatus groups did not differ in WMH volume, but HIV+ participants had less cerebral white matter (mean: 470.95 [43.24] vs. 497.63 [49.42] mL, p = 0.010). The distribution of WMH volume was skewed in HIV+ with a high proportion (23%) falling above the 95th percentile of WMH volume defined by the HIV- group. Serostatus groups had similar amount of WMH volume growth over time. Total WMH volume directly correlated with measures of hypertension and inversely correlated with measures of global cognition, particularly in executive functioning, and psychomotor speed. Greater WMH volume was associated with poorer brain integrity measured from diffusion tensor imaging (DTI) in the corpus callosum and sagittal stratum. In this group of HIV+ individuals over 60, WMH burden was associated with cardiovascular risk and both worse diffusion MRI and cognition. The median total burden did not differ by serostatus; however, a subset of HIV+ individuals had high WMH burden.

White matter hyperintensities are associated with disproportionate progressive hippocampal atrophy

This study investigates relationships between white matter hyperintensity (WMH) volume, cerebrospinal fluid (CSF) Alzheimer's disease (AD) pathology markers, and brain and hippocampal volume loss. Subjects included 198 controls, 345 mild cognitive impairment (MCI), and 154 AD subjects with serial volumetric 1.5‐T MRI. CSF Aβ₄₂ and total tau were measured (n = 353). Brain and hippocampal loss were quantified from serial MRI using the boundary shift integral (BSI). Multiple linear regression models assessed the relationships between WMHs and hippocampal and brain atrophy rates. Models were refitted adjusting for (a) concurrent brain/hippocampal atrophy rates and (b) CSF Aβ₄₂ and tau in subjects with CSF data. WMH burden was positively associated with hippocampal atrophy rate in controls (P = 0.002) and MCI subjects (P = 0.03), and with brain atrophy rate in controls (P = 0.03). The associations with hippocampal atrophy rate remained following adjustment for concurrent brain atrophy rate in controls and MCIs, and for CSF biomarkers in controls (P = 0.007). These novel results suggest that vascular damage alongside AD pathology is associated with disproportionately greater hippocampal atrophy in nondemented older adults. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.

White matter hyperintensity microstructure in amyloid dysmetabolism

Accumulating evidence suggests associations between cerebrovascular disease (CVD) and Alzheimer's disease (AD). White matter hyperintensities of presumed vascular origin (WMHs) are increased in subjects with mild cognitive impairment (MCI) and AD, but the exact pathomechanistic link is unknown. The current study investigated effects of amyloid dysmetabolism on the microstructure of WMHs in subjects with MCI or subjective cognitive decline (N = 51), dichotomized according to pathological or normal levels of amyloid-β peptide (Aβ42) in cerebrospinal fluid (CSF). Thirty-one subjects with low CSF Aβ42 (Aβ+) and 20 subjects with normal CSF Aβ42 (Aβ-) were assessed with magnetic resonance diffusion tensor imaging (DTI), and fractional anisotropy (FA), radial diffusivity (DR), axial diffusivity (DA), and mean diffusivity (MD) were determined. There were no significant differences in WMH volume or distribution between the groups, and neither age nor WMH volume had significant impact on the DTI indices. Nevertheless, there were significantly higher DA, DR, and MD in WMHs in Aβ+ relative to Aβ-; however, no differences in FA were found. The present results suggest that amyloid accumulation is associated with impaired structural integrity (e.g. relating to more extensive demyelination and loss of axons) in WMHs putatively adding to effects of ischemia.

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.

Amyloid Dysmetabolism Relates to Reduced Glucose Uptake in White Matter Hyperintensities

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder and cause of dementia and is characterized by amyloid plaques and neurofibrillary tangles. AD has traditionally been considered to primarily affect gray matter, but multiple lines of evidence also indicate white matter (WM) pathology and associated small-vessel cerebrovascular disease. WM glucose delivery and metabolism may have implications for local tissue integrity, and [¹⁸F]-fluorodeoxyglucose positron emission tomography (FDG-PET) may be helpful to assess neuroglial and axonal function in WM. Hypothesizing that affection of oligodendroglia will be associated with loss of glucose uptake, we aimed to investigate glucose metabolism in magnetic resonance imaging (MRI) white matter hyperintensities (WMHs) and normal-appearing WM in patients with and without evidence of amyloid plaques. Subjects with mild cognitive impairment or subjective cognitive decline were included and dichotomized according to pathological (Aβ+) or normal (Aβ−) concentrations of cerebrospinal fluid amyloid-β 1–42. A total of 50 subjects were included, of whom 30 subjects were classified as Aβ(+) and 20 subjects as Aβ(−). All subjects were assessed with MRI and FDG-PET. FDG-PET images were corrected for effects of partial voluming and normalized to cerebellar WM, before determining WMH FDG-uptake. Although there were no significant differences between the groups in terms of age, WMH volume, number of individual WMHs, or WMH distribution, we found significantly lower (p = 0.021) FDG-uptake in WMHs in Aβ(+) subjects (mean = 0.662, SD = 0.113) compared to Aβ(−) subjects (mean = 0.596, SD = 0.073). There were no significant group differences in the FDG-uptake in normal-appearing WM. Similar results were obtained without correction for effects of partial voluming. Our findings add to the evidence for a link between Aβ dysmetabolism and WM pathology in AD.

White Matter Hyperintensities in Older Adults and Motoric Cognitive Risk Syndrome

INTRODUCTION

Motoric cognitive risk (MCR) syndrome is a recently described pre-dementia syndrome characterized by slow gait and cognitive complaints that has been implicated as a predictor of cognitive decline and dementia in older adults. Previous work suggests that cerebrovascular disease is associated with MCR. White matter hyperintensities (WMH) are postulated to be a product of cerebrovascular disease, and have been associated with impaired mobility and impaired cognition. This study aimed to determine if MCR is associated with regional WMH.

METHODS

Two cross-cultural cohorts of non-demented older adults were examined: 174 from a French memory clinic (62.1% male, mean age 70.7 ± 4.3 years) and 184 from an Indian community-dwelling cohort (55.4% male, mean age 66.2 ± 5.2 years). Participants were evaluated for slow gait, cognitive complaints, and regional WMH via MRI (fluid attenuated inversion recovery) FLAIR sequence.

RESULTS

Overall, 20.7% of participants met criteria for MCR, and 72.9% of participants had WMH on FLAIR. WMH in the frontal, parieto-occipital, temporal, basal ganglia, cerebellum, or brainstem were not associated with MCR in either of the two cohorts.

CONCLUSION

WMH was not significantly associated with MCR in this studied sample of participants, suggesting that other cerebrovascular pathophysiological mechanisms, or combination of mechanisms, might underlie MCR.

Long-Term Clinical Impact of Vascular Brain Lesions on Magnetic Resonance Imaging in Older Adults in the Population

BACKGROUND AND PURPOSE

White matter hyperintensity (WMH) volume and covert brain infarcts are highly prevalent in older adults and are often asymptomatic. We compared the impact of WMH volume and brain infarcts on risk of clinical stroke and dementia in older adults in the population.

METHODS

Participants were 1677 individuals aged ≥65 years from the 3-City Dijon study, who were free of stroke and dementia at baseline, followed-up for ≤12 years.

RESULTS

Both lesion types were comparably associated with an increased risk of stroke (adjusted hazard ratio, 1.72; 95% confidence interval, 1.24-2.40 for WMH volume and hazard ratio, 2.15; 95% confidence interval, 1.18-3.93 for brain infarcts), but only WMH volume was associated with an increased risk of dementia (hazard ratio, 1.41; 95% confidence interval, 1.09-1.83).

CONCLUSIONS

The differential impact of WMH and brain infarcts on clinical stroke and dementia suggests relatively different prognostic value of the 2 lesions. WMHs may represent a particularly pertinent magnetic resonance imaging intermediate marker that can be utilized in optimizing prevention strategies for both stroke and dementia in primary care and in trials.

Inflammatory cytokines influence measures of white matter integrity in Bipolar Disorder

BACKGROUND

Bipolar Disorder (BD) is associated with elevated biomarkers of cell-mediated immune activation and inflammation and with signs of widespread disruption of white matter (WM) integrity in adult life. Consistent findings in animal models link WM damage in inflammatory diseases of the brain and serum levels of cytokines.

METHODS

With an exploratory approach, we tested the effects of 22 serum analytes, including pro- and anti-inflammatory cytokines and neurotrophic/hematopoietic factors, on DTI measures of WM microstructure in a sample of 31 patients with a major depressive episode in course of BD. We used whole brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial (AD), radial (RD), and mean diffusivity (MD), and fractional anisotropy (FA).

RESULTS

The inflammation-related cytokines TNF-α, IL-8, IFN-γ and IL-10, and the growth factors IGFBP2 and PDGF-BB, shared the same significant associations with lower FA, and higher MD and RD, in large overlapping networks of WM fibers mostly located in the anterior part of the brain and including corpus callosum, cingulum, superior and inferior longitudinal fasciculi, inferior fronto-occipital fasciculi, uncinate, forceps, corona radiata, thalamic radiation, internal capsule.

CONCLUSIONS

Higher RD is thought to signify increased space between fibers, suggesting demyelination or dysmyelination. The pattern of higher RD and MD with lower FA suggests that inflammation-related cytokine and growth factor levels inversely associate with integrity of myelin sheaths. The activated inflammatory response system might contribute to BD pathophysiology by hampering structural connectivity in critical cortico-limbic networks.

Regional Gray Matter Atrophy Coexistent with Occipital Periventricular White Matter Hyper Intensities

White matter hyperintensities (WMHs) and brain atrophy often coexist in the elderly. Additionally, WMH is often observed as occipital periventricular hyperintensities (OPVHs) with low-grade periventricular (PV) white matter (WM) lesions and is usually confined within an anatomical structure. However, the effects of OPVHs on gray matter (GM) atrophy remain largely unknown. In this study, we investigated GM atrophy in OPVHs patients and explored the relationship between such atrophy and clinical risk factors. T1-weighted and T2-weighted Magnetic resonance imaging (MRI) were acquired, and voxel-based morphometry (VBM) analysis was applied. The clinical (demographic and cardiovascular) risk factors of the OPVHs patients and healthy controls were then compared. Lastly, scatter plots and correlation analysis were applied to explore the relationship between the MRI results and clinical risk factors in the OPVHs patients. OPVHs patients had significantly reduced GM in the right supramarginal gyrus, right angular gyrus, right middle temporal gyrus, right anterior cingulum and left insula compared to healthy controls. Additionally, OPVHs patients had GM atrophy in the left precentral gyrus and left insula cortex, and such atrophy is associated with a reduction in low-density lipoprotein cholesterol (LDL-C) and apolipoprotein-B (Apo-B).

Tractography at 3T MRI of Corpus Callosum Tracts Crossing White Matter Hyperintensities

BACKGROUND AND PURPOSE

The impact of white matter hyperintensities on the diffusion characteristics of crossing tracts is unclear. This study used quantitative tractography at 3T MR imaging to compare, in the same individuals, the diffusion characteristics of corpus callosum tracts that crossed white matter hyperintensities with the diffusion characteristics of corpus callosum tracts that did not pass through white matter hyperintensities.

MATERIALS AND METHODS

Brain T2 fluid-attenuated inversion recovery-weighted and diffusion tensor 3T MR imaging scans were acquired in 24 individuals with white matter hyperintensities. Tractography data were generated by the Fiber Assignment by Continuous Tracking method. White matter hyperintensities and corpus callosum tracts were manually segmented. In the corpus callosum, the fractional anisotropy, radial diffusivity, and mean diffusivity of tracts crossing white matter hyperintensities were compared with the fractional anisotropy, radial diffusivity, and mean diffusivity of tracts that did not cross white matter hyperintensities. The cingulum, long association fibers, corticospinal/bulbar tracts, and thalamic projection fibers were included for comparison.

RESULTS

Within the corpus callosum, tracts that crossed white matter hyperintensities had decreased fractional anisotropy compared with tracts that did not pass through white matter hyperintensities (P = .002). Within the cingulum, tracts that crossed white matter hyperintensities had increased radial diffusivity compared with tracts that did not pass through white matter hyperintensities (P = .001).

CONCLUSIONS

In the corpus callosum and cingulum, tracts had worse diffusion characteristics when they crossed white matter hyperintensities. These results support a role for white matter hyperintensities in the disruption of crossing tracts.

Post-mortem assessment in vascular dementia: advances and aspirations

BACKGROUND

Cerebrovascular lesions are a frequent finding in the elderly population. However, the impact of these lesions on cognitive performance, the prevalence of vascular dementia, and the pathophysiology behind characteristic in vivo imaging findings are subject to controversy. Moreover, there are no standardised criteria for the neuropathological assessment of cerebrovascular disease or its related lesions in human post-mortem brains, and conventional histological techniques may indeed be insufficient to fully reflect the consequences of cerebrovascular disease.

DISCUSSION

Here, we review and discuss both the neuropathological and in vivo imaging characteristics of cerebrovascular disease, prevalence rates of vascular dementia, and clinico-pathological correlations. We also discuss the frequent comorbidity of cerebrovascular pathology and Alzheimer's disease pathology, as well as the difficult and controversial issue of clinically differentiating between Alzheimer's disease, vascular dementia and mixed Alzheimer's disease/vascular dementia. Finally, we consider additional novel approaches to complement and enhance current post-mortem assessment of cerebral human tissue.

CONCLUSION

Elucidation of the pathophysiology of cerebrovascular disease, clarification of characteristic findings of in vivo imaging and knowledge about the impact of combined pathologies are needed to improve the diagnostic accuracy of clinical diagnoses.

Correlating Cognitive Decline with White Matter Lesion and Brain Atrophy Magnetic Resonance Imaging Measurements in Alzheimer's Disease

BACKGROUND

Vascular risk factors are increasingly recognized as risks factors for Alzheimer's disease (AD) and early conversion from mild cognitive impairment (MCI) to dementia. While neuroimaging research in AD has focused on brain atrophy, metabolic function, or amyloid deposition, little attention has been paid to the effect of cerebrovascular disease to cognitive decline.

OBJECTIVE

To investigate the correlation of brain atrophy and white matter lesions with cognitive decline in AD, MCI, and control subjects.

METHODS

Patients with AD and MCI, and healthy subjects were included in this study. Subjects had a baseline MRI scan, and baseline and follow-up neuropsychological battery (CERAD). Regional volumes were measured, and white matter lesion segmentation was performed. Correlations between rate of CERAD score decline and white matter lesion load and brain structure volume were evaluated. In addition, voxel-based correlations between baseline CERAD scores and atrophy and white matter lesion measures were computed.

RESULTS

CERAD rate of decline was most significantly associated with lesion loads located in the fornices. Several temporal lobe ROI volumes were significantly associated with CERAD decline. Voxel-based analysis demonstrated strong correlation between baseline CERAD scores and atrophy measures in the anterior temporal lobes. Correlation of baseline CERAD scores with white matter lesion volumes achieved significance in multilobar subcortical white matter.

CONCLUSION

Both baseline and declines in CERAD scores correlate with white matter lesion load and gray matter atrophy. Results of this study highlight the dominant effect of volume loss, and underscore the importance of small vessel disease as a contributor to cognitive decline in the elderly.

Neuroimaging correlates of neuropsychiatric symptoms in Alzheimer's disease: a review of 20 years of research

Assessing morphological, perfusion and metabolic brain changes preceding or associated with neuropsychiatric symptoms (NPSs) will help in the understanding of pathophysiological underlying processes in Alzheimer's disease (AD). This review aimed to highlight the main findings on significant associations between neuroimaging and NPSs, the pathophysiology to elucidate possible underlying mechanisms, and methodological issues to aid future research. Research papers published from January 1990 to October 2015 were identified in the databases PsycInfo, Embase, PubMed and Medline, using key words related to NPSs and imaging techniques. In addition to a semi-systematic search in the databases, we also performed hand searches based on reported citations identified to be of interest. Delusions, apathy and depression symptoms were particularly associated with brain changes in AD. The majority of studies disclosed an association between frontal lobe structural and/or metabolic changes and NPSs, implicating, interestingly, for all 12 NPSs studied, the anterior cingulate cortex although temporal, subcortical and parietal regions, and insula were also involved. Given the high degree of connectivity of these brain areas, frontal change correlates of NPSs may help in the understanding of neural network participation. This review also highlights crucial methodological issues that may reduce the heterogeneity of results to enable progress on the pathophysiological mechanisms and aid research on NPS treatments in AD. Based on a broad review of the current literature, a global brain pattern to support the huge heterogeneity of neuroimaging correlates of NPSs in AD and methodological strategies are suggested to help direct future research.

Memory impairment in occipital periventricular hyperintensity patients is associated with reduced functional responses in the insula and Heschl's gyrus

OBJECTIVES

The aim of this study was to investigate the cognitive impairments of occipital periventricular hyperintensity (OPVH) patients and their brain-wide functional alterations in large scale.

METHODS

The Mini-Mental State Examination (MMSE) was performed in 15 OPVH patients and 12 age-matched healthy controls to distinguish the cognitive impairment features of OPVH. Functional magnetic resonance imaging (fMRI) was applied with a delayed digital match memory task to identify the brain-wide functional alterations in OPVH patients.

RESULTS

The two groups were not statistically different in terms of demographic or cardiovascular risk factors. The OPVH group had significantly lower scores in global cognitive abilities, immediate memory and delayed memory as determined by the MMSE (p < 0.05). The fMRI results demonstrated that the insula, precentral gyrus and Heschl's gyrus of the OPVH group had decreased activation compared to the control group (p < 0.005, uncorrected). Multivariate analysis also showed that OPVH was negatively correlated with reduced activation in the insula, precentral gyrus and Heschl's gyrus (p < 0.005).

CONCLUSION

OPVH affects the immediate and delayed memory. These changes are accompanied with decreased functional responses in the insula and Heschl's gyrus.

Differential Effect of White-Matter Lesions and Covert Brain Infarcts on the Risk of Ischemic Stroke and Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

We examined the association of white-matter hyperintensity (WMH) volume and covert brain infarcts, which are the 2 major magnetic resonance imaging markers of covert cerebrovascular disease in older adults, with long-term risk of ischemic stroke and intracerebral hemorrhage (ICH) in the general population.

METHODS

Participants were 1731 individuals aged ≥65 years from the Three-City Dijon study. We studied the association of WMH volume and brain infarct, with incident ischemic stroke overall, and by subtype, and with incident ICH.

RESULTS

High total, periventricular, and deep WMHs were associated with incident ICH. Extensive periventricular WMH volume was associated with increased risk of ischemic stroke (hazard ratio, 1.94; 95% confidence interval, 1.12-3.35), particularly cardioembolic stroke. Covert brain infarcts were associated with incident ICH but not with incident ischemic stroke or its subtypes.

CONCLUSIONS

Although of ischemic nature, both WMH volume and covert brain infarcts portend a major risk of ICH. If confirmed in independent studies, these findings could have important implications for the clinical management of covert vascular brain lesions.

Potential neuroimaging biomarkers of pathologic brain changes in Mild Cognitive Impairment and Alzheimer's disease: a systematic review

Background

Neuroimaging-biomarkers of Mild Cognitive Impairment (MCI) allow an early diagnosis in preclinical stages of Alzheimer’s disease (AD). The goal in this paper was to review of biomarkers for Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD), with emphasis on neuroimaging biomarkers.

Methods

A systematic review was conducted from existing literature that draws on markers and evidence for new measurement techniques of neuroimaging in AD, MCI and non-demented subjects. Selection criteria included: 1) age ≥ 60 years; 2) diagnosis of AD according to NIAAA criteria, 3) diagnosis of MCI according to NIAAA criteria with a confirmed progression to AD assessed by clinical follow-up, and 4) acceptable clinical measures of cognitive impairment, disability, quality of life, and global clinical assessments.

Results

Seventy-two articles were included in the review. With the development of new radioligands of neuroimaging, today it is possible to measure different aspects of AD neuropathology, early diagnosis of MCI and AD become probable from preclinical stage of AD to AD dementia and non-AD dementia.

Conclusions

The panel of noninvasive neuroimaging-biomarkers reviewed provides a set methods to measure brain structural and functional pathophysiological changes in vivo, which are closely associated with preclinical AD, MCI and non-AD dementia. The dynamic measures of these imaging biomarkers are used to predict the disease progression in the early stages and improve the assessment of therapeutic efficacy in these diseases in future clinical trials.

White matter hyperintensities are more highly associated with preclinical Alzheimer's disease than imaging and cognitive markers of neurodegeneration

INTRODUCTION

Cognitive tests and nonamyloid imaging biomarkers do not consistently identify preclinical AD. The objective of this study was to evaluate whether white matter hyperintensity (WMH) volume, a cerebrovascular disease marker, is more associated with preclinical AD than conventional AD biomarkers and cognitive tests.

METHODS

Elderly controls enrolled in the Alzheimer's Disease Neuroimaging Initiative (ADNI, n = 158) underwent florbetapir-PET scans, psychometric testing, neuroimaging with MRI and PET, and APOE genetic testing. Elderly controls the Parkinson's progression markers initiative (PPMI, n = 58) had WMH volume, cerebrospinal fluid (CSF) Aβ1-42, and APOE status measured.

RESULTS

In the ADNI cohort, only WMH volume and APOE ε4 status were associated with cerebral Aβ (standardized β = 0.44 and 1.25, P = .03 and .002). The association between WMH volume and APOE ε4 status with cerebral Aβ (standardized β = 1.12 and 0.26, P = .048 and .045) was confirmed in the PPMI cohort.

DISCUSSION

WMH volume is more highly associated with preclinical AD than other AD biomarkers.

Cerebrovascular and microglial states are not altered by functional neuroinflammatory gene variant

The translocator protein, a microglial-expressed marker of neuroinflammation, has been implicated in Alzheimer's disease, which is characterized by alterations in vascular and inflammatory states. ATSPOvariant, rs6971, determines binding affinity of exogenous radioligandsin vivo; however, the effect of these altered binding characteristics on inflammatory and cerebrovascular biomarkers has not been assessed. In 2345 living subjects (Alzheimer's Disease Neuroimaging Initiative, n = 1330) and postmortem brain samples (Religious Orders Study and Memory and Aging Project, n = 1015), we analyzed effects of rs6971 on white matter hyperintensisites, cerebral infarcts, circulating inflammatory biomarkers, amyloid angiopathy, and microglial activation. We found that rs6971 does not alter translocator protein in a way that impacts cerebrovascular and inflammatory states known to be affected in dementia.

Morphologic and neuropsychological patterns in patients suffering from Alzheimer's disease

INTRODUCTION

We conducted a retrospective study to identify morphological subgroups of patients referred for AD or aMCI and to seek for differences across neuropsychological performances.

METHODS

One hundred forty-five patients (mean age = 76.01, 88 women and 57 men) referred for AD, either at the stage of dementia or aMCI, were examined using structural MRI. Five observers reviewed blindly twice all examinations. We rated microangiopathy, hippocampal, parietal atrophies, including a gradient of fronto-parietal atrophy (GFPA). A multiple component analysis (MCA) followed by a hierarchical ascending classification was conducted to identify morphologically distinct subgroups. Among these, 76 patients completed all the neuropsychological tests. Univariate and multivariate analyses were further conducted on these data across morphological subgroups. The institutional review board approved the research protocol.

RESULTS

Inter- and intra-raters' agreements were excellent and very good for microangiopathy and hippocampal atrophy ratings. They were higher for GFPA than for the parietal atrophy scale. MCA without priors identified three groups: group 1 was characterized by no/discrete microangiopathy, severe hippocampal, and predominant parietal atrophy; group 2 had significant microangiopathy, severe hippocampal atrophy, and no predominant parietal atrophy; group 3 had a mild hippocampal atrophy and parietal atrophies. In group 1, working memory profile was less impaired than in group 2 (p = 0.01). Neuropsychological performances of group 3 were higher in most domains.

CONCLUSION

Combined characterization of microangiopathy, hippocampal, parietal, and GFPA allows identifying morphological subgroups among patients referred for AD and at risk. These groups have some neuropsychological differences, suggesting different pathophysiological mechanisms or co-existing conditions.

Montreal cognitive assessment and analysis of related factors for cognitive impairment in patients with chronic cerebral circulation insufficiency

BACKGROUND

Chronic cerebral circulation insufficiency (CCCI) refers to cerebral dysfunctions that lead to cerebral vascular pathological changes. Our aim is to identify factors related to cognitive impairment in CCCI.

METHODS

CCCI patients (n=102) were assessed with the Montreal cognitive assessment (MoCA) to analyze cognitive impairment. Patients were divided into two groups according to MoCA scores: (1) cognitive dysfunction and (2) normal cognitive function. We compared the clinical information with univariate and multivariate logistic regression analyses and identified major risk factors related to cognitive impairment in CCCI.

RESULTS

Age (p=0.007, OR=3.768, χ2=7.173), leukoaraiosis (p=0.002, OR=6.231, χ2=9.478), a history of hypertension (p=0.021, OR=3.078, χ2=5.307), a history of hyperlipidemia (p=0.016, OR=3.429, χ2=5.795), and the number of vascular risk factors (p=0.019, χ2=9.921) were related to cognitive impairment by univariate analysis. Age (p=0.070, OR=2.689, 95% CI=0.923±7.837) and leukoaraiosis (p=0.012, OR=4.531, 95% CI=1.401±14.667) were significant by multivariate logistic regression analysis. Age (r=-0.585, p<0.01) had a marked negative correlation with MoCA scores. There were significant differences in the MoCA subscale scores, including visuospatial and executive capacity (p<0.01), attention and calculation (p<0.01), and delayed recall (p<0.01), in patients with different degrees of leukoaraiosis. Patients with CCCI had a higher incidence of cognitive impairment (78.4%).

CONCLUSIONS

Changes in visuospatial and executive capacity, delayed recall, and language function represent cognitive manifestations in CCCI. Age and leukoaraiosis have the strongest effects on cognitive impairment morbidity and can aggravate cognitive impairment.

White matter integrity, hippocampal volume, and cognitive performance of a world-famous nonagenarian track-and-field athlete

Physical activity (PA) and cardiorespiratory fitness (CRF) are associated with successful brain and cognitive aging. However, little is known about the effects of PA, CRF, and exercise on the brain in the oldest-old. Here we examined white matter (WM) integrity, measured as fractional anisotropy (FA) and WM hyperintensity (WMH) burden, and hippocampal (HIPP) volume of Olga Kotelko (1919-2014). Olga began training for competitions at age of 77 and as of June 2014 held over 30 world records in her age category in track-and-field. We found that Olga's WMH burden was larger and the HIPP was smaller than in the reference sample (58 healthy low-active women 60-78 years old), and her FA was consistently lower in the regions overlapping with WMH. Olga's FA in many normal-appearing WM regions, however, did not differ or was greater than in the reference sample. In particular, FA in her genu corpus callosum was higher than any FA value observed in the reference sample. We speculate that her relatively high FA may be related to both successful aging and the beneficial effects of exercise in old age. In addition, Olga had lower scores on memory, reasoning and speed tasks than the younger reference sample, but outperformed typical adults of age 90-95 on speed and memory. Together, our findings open the possibility of old-age benefits of increasing PA on WM microstructure and cognition despite age-related increase in WMH burden and HIPP shrinkage, and add to the still scarce neuroimaging data of the healthy oldest-old (>90 years) adults.

White Matter Changes are Associated with Ventricular Expansion in Aging, Mild Cognitive Impairment, and Alzheimer's Disease

White matter lesions are highly prevalent in individuals with Alzheimer's disease (AD). Although these lesions are presumed to be of vascular origin and linked to small vessel disease in older adults, little information exists about their relationship to markers of classical AD neurodegeneration. Thus, we examined the link between these white matter changes (WMC) segmented on T1-weighted MRI and imaging markers presumed to be altered due to primary AD neurodegenerative processes. Tissue microstructure of WMC was quantified using diffusion tensor imaging and the relationship of WMC properties and volume to neuroimaging markers was examined in 219 cognitively healthy older adults and individuals with mild cognitive impairment and AD using data from the Alzheimer's Disease Neuroimaging Initiative. No significant group differences in WMC properties were found. However, there were strong associations between diffusivity of WMC and ventricular volume, volume of WMC and total WM volume. In comparison, group differences in parahippocampal white matter microstructure were found for all diffusion metrics and were largely explained by hippocampal volume. Factor analysis on neuroimaging markers suggested two independent sets of covarying degenerative changes, with potentially age- and vascular-mediated tissue damage contributing to one factor and classical neurodegenerative changes associated with AD contributing to a second factor. These data demonstrate two potentially distinct classes of degenerative change in AD, with one factor strongly linked to aging, ventricular expansion, and both volume and tissue properties of white matter lesions, while the other factor related to classical patterns of cortical and hippocampal neurodegeneration in AD.

Homocysteine Level Is Associated with White Matter Hyperintensity Locations in Patients with Acute Ischemic Stroke

BACKGROUND AND PURPOSE

The relationship between plasma level of total homocysteine (tHcy) and white matter hyperintensities (WMHs), especially in patients with acute ischemic stroke (AIS), is controversial. The present study investigated the association between these two as well as WMH locations in a large cohort of patients with AIS.

METHODS

Consecutive patients were reviewed from a prospective ischemic stroke database. Clinical data, including tHcy level and WMHs, were assessed. WMHs were assessed using the Fazekas scale and Age-Related White Matter Changes (ARWMC) visual grading scale. The association between tHcy and WMH locations was investigated by using multivariate logistic regression analyses.

RESULTS

A total of 923 out of 1,205 patients were examined. The average age was 58.9 ± 11.9 years; 31.6% were female. Elevated tHcy level was significantly associated with WMHs. For the highest tHcy quartile, the odds ratio (OR) (95% confidence interval; CI) was 1.891 (1.257; 2.843) according to the Fazekas scale and 1.781 (1.185; 2.767) according to the ARWMC scale when compared to the lowest quartile. However, in a subgroup analysis, only WMHs in the periventricular area and left or right frontal areas were found to be independently associated with tHcy level. For the highest tHcy quartile, the OR (95% CI) was 1.761 (1.172; 2.648) for the periventricular WMHs, 1.768 (1.134; 2.756)for the left frontal WMHs, and 1.890 (1.206; 2.960)for the right frontal WMHs.

CONCLUSIONS

In patients with AIS, plasma tHcy level is related to WMHs, especially WMHs distributed within the periventricular and frontal areas.

Periventricular white matter hyperintensities and the risk of dementia: a CREDOS study

BACKGROUND

Cerebral white matter hyperintensities (WMH) are prevalent incident findings on brain MRI scans among elderly people and have been consistently implicated in cognitive dysfunction. However, differential roles of WMH by region in cognitive function are still unclear. The aim of this study was to ascertain the differential role of regional WMH in predicting progression from mild cognitive impairment (MCI) to different subtypes of dementia.

METHODS

Participants were recruited from the Clinical Research Center for Dementia of South Korea (CREDOS) study. A total of 622 participants with MCI diagnoses at baseline and follow-up evaluations were included for the analysis. Initial MRI scans were rated for WMH on a visual rating scale developed for the CREDOS. Differential effects of regional WMH in predicting incident dementia were evaluated using the Cox proportional hazards model.

RESULTS

Of the 622 participants with MCI at baseline, 139 patients (22.3%) converted to all-cause dementia over a median of 14.3 (range 6.0-36.5) months. Severe periventricular WMH (PWMH) predicted incident all-cause dementia (Hazard ratio (HR) 2.22; 95% confidence interval (CI) 1.43-3.43) and Alzheimer's disease (AD) (HR 1.86; 95% CI 1.12-3.07). Subcortical vascular dementia (SVD) was predicted by both PWMH (HR 16.14; 95% CI 1.97-132.06) and DWMH (HR 8.77; 95% CI 1.77-43.49) in more severe form (≥ 10 mm).

CONCLUSIONS

WMH differentially predict dementia by region and severity. Our findings suggest that PWMH may play an independent role in the pathogenesis of dementia, especially in AD.

Cerebral Amyloid and Hypertension are Independently Associated with White Matter Lesions in Elderly

In cognitively normal (CN) elderly individuals, white matter hyperintensities (WMH) are commonly viewed as a marker of cerebral small vessel disease (SVD). SVD is due to exposure to systemic vascular injury processes associated with highly prevalent vascular risk factors (VRFs) such as hypertension, high cholesterol, and diabetes. However, cerebral amyloid accumulation is also prevalent in this population and is associated with WMH accrual. Therefore, we examined the independent associations of amyloid burden and VRFs with WMH burden in CN elderly individuals with low to moderate vascular risk. Participants (n = 150) in the Alzheimer’s Disease Neuroimaging Initiative (ADNI) received fluid attenuated inversion recovery (FLAIR) MRI at study entry. Total WMH volume was calculated from FLAIR images co-registered with structural MRI. Amyloid burden was determined by cerebrospinal fluid Aβ_1-42 levels. Clinical histories of VRFs, as well as current measurements of vascular status, were recorded during a baseline clinical evaluation. We tested ridge regression models for independent associations and interactions of elevated blood pressure (BP) and amyloid to total WMH volume. We found that greater amyloid burden and a clinical history of hypertension were independently associated with greater WMH volume. In addition, elevated BP modified the association between amyloid and WMH, such that those with either current or past evidence of elevated BP had greater WMH volumes at a given burden of amyloid. These findings are consistent with the hypothesis that cerebral amyloid accumulation and VRFs are independently associated with clinically latent white matter damage represented by WMHs. The potential contribution of amyloid to WMHs should be further explored, even among elderly individuals without cognitive impairment and with limited VRF exposure.

Hippocampal atrophy but not white-matter changes predicts the long-term cognitive response to cholinesterase inhibitors in Alzheimer's disease

INTRODUCTION

This study aimed to investigate the feasibility of predicting the long-term effects of cholinesterase inhibitors (ChEI) with common clinical neuroimaging parameters of Alzheimer's disease, including medial temporal lobe atrophy (MTA) and white matter hyperintensity (WMH).

METHOD

A cohort of 353 patients with very mild to moderate Alzheimer's disease received cholinesterase inhibitors and were followed for a median of 46.6 months. Baseline clinical data, including age, educational level, Clinical Dementia Rating (CDR), Taiwanese Mental State Examination (TMSE), and visual scoring for MTA and WMH were tested as possible predictive factors that influence the survival from a TMSE decline of at least 3 points.

RESULTS

During the follow-up period, 162(46%) patients had a significant TMSE decline. Patients with age-adjusted prominent MTA had a significantly shorter TMSE-decline free interval than those without (43.4 ± 4.5 months vs. 68.2 ± 9.5 months, log rank test p-value =0.001). However, the severity of WMH does not significantly influence cognitive outcomes. Cox regression analysis identified that younger age at the time of starting ChEI (p < 0.0005) and higher total MTA scores (p = 0.002) predict a more rapid TMSE decline under ChEI therapy.

CONCLUSIONS

Younger age at the time of starting ChEI and higher visual scoring of MTA may imply a more advanced Alzheimer's pathology. WMH load is not a prognostic indicator of treatment response to ChEI.

Cortical tau load is associated with white matter hyperintensities

INTRODUCTION

Cerebral white matter lesions (WML), visualized as white matter hyperintensities (WMH) on T2-weighted MRI, encompass structural damage and loss of integrity of the cerebral white matter (WM) and are commonly assumed to be associated with small vessel disease (SVD). However, it has been suggested that WM damage may also be the result of degenerative axonal loss that is secondary to cortical Alzheimer's disease (AD) pathologies i.e., hyperphosphorylated tau (HPτ) and amyloid-beta (Aβ). Here we investigate the influence of HPτ, Aβ and SVD on WMH severity.

RESULTS

36 human post-mortem right fixed cerebral hemispheres (mean age 84.4 ± 7.7 years; male: 16, female: 20) containing varying amounts of AD-pathology (AD: 23, controls: 13) underwent T2- weighted MRI with WMH assessed according to the age related white matter change scale (ARWMC). After dissection, using tissue samples from the frontal, temporal, parietal and occipital regions from the right hemisphere, we quantitatively assessed cortical HPτ and Aβ pathology burden by measuring the percentage area covered by AT8 immunoreactivity (HPτ-IR) and 4G8 immunoreactivity (Aβ-IR), and assessed the severity of WM SVD by calculating the sclerotic index (SI) of WM arteries/arterioles. HPτ-IR, Aβ-IR, and SI were compared with ARWMC scores. HPτ-IR, Aβ-IR and WM ARWMC scores were all significantly higher in AD cases compared to controls, while SI values were similar between groups. ARWMC scores correlated with HPτ-IR, Aβ-IR and SI in various regions, however, linear regression revealed that only HPτ-IR was a significant independent predictor of ARWMC scores.

CONCLUSIONS

Here we have shown that increasing cortical HPτ burden independently predicted the severity of WMH indicating its potentially important role in the pathogenesis of WM damage. Moreover, our findings suggest that in AD patients the presence of WMH may indicate cortical AD-associated pathology rather than SVD. Further studies are warranted to elucidate the pathological processes that lead to WM damage and to clarify if WMH may serve as a general biomarker for cortical AD-associated pathology.

Reduced binding of Pittsburgh Compound-B in areas of white matter hyperintensities

The amyloid imaging agent, Pittsburgh Compound-B, binds with high affinity to β-amyloid (Aβ) in the brain, and it is well established that PiB also shows non-specific retention in white matter (WM). However, little is known about retention of PiB in areas of white matter hyperintensities (WMH), abnormalities commonly seen in older adults. Further, it is hypothesized that WMH are related to both cognitive dysfunction and Aβ deposition. The goal of the present study was to explore PiB retention in both normal-appearing WM (NAWM) and WMH in a group of elderly, cognitively normal individuals. In a group of cognitively normal elderly (n = 64; 86.5 ± 2.6 years) two analyses were applied: (1) ROIs were placed over periventricular areas in which WMH caps are commonly seen on all subjects, regardless of WMH burden or size. (2) Subject-specific maps of NAWM and WMH were co-registered with the PiB-PET images and mean SUVR values were calculated in these NAWM and WMH maps. PiB retention was significantly reduced in the ROIs of subjects with high WMH compared to subjects with low WMH. Additionally, in subjects with high WMH, there was significantly lower PiB retention in subject-specific maps of WMH compared to NAWM, which was not observed in subjects with low WMH, likely because of the small size of WMH maps in this group. These data suggest that WM in areas of WMH binds PiB less effectively than does normal WM. Further exploration of this phenomenon may lead to insights about the molecular basis of the non-specific retention of amyloid tracers in white matter.

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PiB retention was significantly reduced in the “typical-WMH” ROIs of subjects with high WMH compared to subjects with low WMH.

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In subjects with high WMH, there was significantly lower PiB retention in subject-specific maps of WMH compared to NAWM.

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These data suggest that WM in areas of WMH binds PiB less effectively than does normal WM.

Reduced perfusion in normal-appearing white matter in mild to moderate hypertension as revealed by 3D pseudocontinuous arterial spin labeling

PURPOSE

To investigate the hemodynamic changes of normal-appearing white matter (NAWM) in hypertension using the 3D pseudocontinuous arterial spin labeling (pCASL) technique.

MATERIALS AND METHODS

Seventy-three subjects, including a patient group (n = 41; 30 males; age = 47.7 ± 8.3 years; test-time blood pressure [BP] = 155 ± 23/98 ± 11 mmHg) and an age-matched control group (n = 32; 14 males; age = 46 ± 8.3 years; test-time BP = 117 ± 8/76 ± 10 mmHg), were recruited and scanned on a 3.0T magnetic resonance imaging (MRI) system using routine MRI sequences and 3D pCASL sequence. The routine MRI sequences were used to further define the NAWM. The cerebral blood flow (CBF) values in various regions of interest (ROIs) were extracted. One-way analysis of variance (ANOVA) and unpaired t-test were performed to evaluate the significance of the intergroup difference in CBF modifications.

RESULTS

Compared to healthy volunteers, CBF values in global gray matter (GM) and various NAWM regions were found to be lower (P < 0.05) in hypertensive patients, except for genu of corpus callosum (CC), cingulate gyrus, amygdala, pallidum, putamen, and thalamus (P > 0.05). Furthermore, compared to the control group, mild hypertension showed significantly reduced CBF in various ROIs (P < 0.05), but no intergroup differences in GM, R anterior horn of periventricular WM, and genu of CC (P > 0.05), while moderate hypertension showed reduced CBF in all ROIs (P < 0.05). However, it was observed that, between mild and moderate hypertensive patients, there were no statistically significant difference in CBF values except for genu of CC (P < 0.05).

CONCLUSION

3D pCASL has the ability to detect subtle hemodynamic abnormalities in NAWM regions at relatively early stages of hypertension. The observed decreases in CBF in these regions may suggest an increased risk of cerebral small vessel diseases.

Cerebrospinal fluid biomarkers of neurovascular dysfunction in mild dementia and Alzheimer's disease

Alzheimer's disease (AD) is the most common form of age-related dementias. In addition to genetics, environment, and lifestyle, growing evidence supports vascular contributions to dementias including dementia because of AD. Alzheimer's disease affects multiple cell types within the neurovascular unit (NVU), including brain vascular cells (endothelial cells, pericytes, and vascular smooth muscle cells), glial cells (astrocytes and microglia), and neurons. Thus, identifying and integrating biomarkers of the NVU cell-specific responses and injury with established AD biomarkers, amyloid-β (Aβ) and tau, has a potential to contribute to better understanding of the disease process in dementias including AD. Here, we discuss the existing literature on cerebrospinal fluid biomarkers of the NVU cell-specific responses during early stages of dementia and AD. We suggest that the clinical usefulness of established AD biomarkers, Aβ and tau, could be further improved by developing an algorithm that will incorporate biomarkers of the NVU cell-specific responses and injury. Such biomarker algorithm could aid in early detection and intervention as well as identify novel treatment targets to delay disease onset, slow progression, and/or prevent AD.

Treatment of Vascular Cognitive Impairment

OPINION STATEMENT

Cerebrovascular disease (CVD) is an important cause of cognitive dysfunction and dementia. The term vascular cognitive impairment (VCI) is used to describe the entire spectrum of cognitive dysfunction-ranging from mild impairment to dementia-attributable to all forms of cerebrovascular disease. Accurate assessment and management of vascular risk factors are a top priority in the treatment of VCI, particularly early in the disease when prevention strategies may prove to be more effective. There are limited treatment options to improve cognition and function in VCI. Several acetylcholinesterase inhibitors and the NMDA receptor antagonist memantine have been studied in large, well-designed trials. These agents are safe and provide modest cognitive benefits in vascular dementia (VaD) but have demonstrated inconsistent efficacy on functional measures. Other therapies, such as aspirin, calcium channel blockers, and vitamin supplementation, have less evidence to support their use in improving cognition in VCI. Although primary prevention trials suggest that treatment of hypertension, adherence to a Mediterranean diet, physical activity, and smoking cessation may reduce the risk of cognitive decline, there is limited evidence regarding these interventions in helping improve cognition in VCI. The pathophysiology and treatment of cerebral autosomal dominant arteriopathy with subcortical infarcts (CADASIL), cerebral amyloid angiopathy (CAA), and subcortical white matter disease (SWMD) deserves special consideration.

White matter signal abnormality quality differentiates mild cognitive impairment that converts to Alzheimer's disease from nonconverters

The objective of this study was to assess how longitudinal change in the quantity and quality of white matter signal abnormalities (WMSAs) contributes to the progression from mild cognitive impairment (MCI) to Alzheimer's disease (AD). The Mahalanobis distance of WMSA from normal-appearing white matter using T1-, T2-, and proton density-weighted MRI was defined as a quality measure for WMSA. Cross-sectional analysis of WMSA volume in 104 cognitively healthy older adults, 116 individuals with MCI who converted to AD within 3 years (mild cognitive impairment converter [MCI-C]), 115 individuals with MCI that did not convert in that time (mild cognitive impairment nonconverter [MCI-NC]), and 124 individuals with AD from the Alzheimer's Disease Neuroimaging Initiative revealed that WMSA volume was substantially greater in AD relative to the other groups but did not differ between MCI-NC and MCI-C. Longitudinally, MCI-C exhibited faster WMSA quality progression but not volume compared with matched MCI-NC beginning 18 months before MCI-C conversion to AD. The strongest difference in rate of change was seen in the time period starting 6 months before MCI-C conversion to AD and ending 6 months after conversion (p < 0.001). The relatively strong effect in this time period relative to AD conversion in the MCI-C was similar to the relative rate of change in hippocampal volume, a traditional imaging marker of AD pathology. These data demonstrate changes in white matter tissue properties that occur within WMSA in individuals with MCI that will subsequently obtain a clinical diagnosis of AD within 18 months. Individuals with AD have substantially greater WMSA volume than all MCI suggesting that there is a progressive accumulation of WMSA with progressive disease severity, and that quality change predates changes in this total volume. Given the timing of the changes in WMSA tissue quality relative to the clinical diagnosis of AD, these findings suggest that WMSAs are a critical component for this conversion and are a critical component of this clinical syndrome.

Tract-based analysis of white matter degeneration in Alzheimer's disease

Although much prior work has focused on the known cortical pathology that defines Alzheimer's disease (AD) histologically, recent work has additionally demonstrated substantial damage to the cerebral white matter in this condition. While there is large evidence of diffuse damage to the white matter in AD, it is unclear whether specific white matter tracts exhibit a more accelerated pattern of damage and whether the damage is associated with the classical neurodegenerative changes of AD. In this study, we investigated microstructural differences in the large fascicular bundles of the cerebral white matter of individuals with AD and mild cognitive impairment (MCI), using recently developed automated diffusion tractography procedures in the Alzheimer's disease Neuroimaging Initiative (ADNI) dataset. Eighteen major fiber bundles in a total of 36 individuals with AD, 81 MCI and 60 control participants were examined with the TRActs Constrained by UnderLying Anatomy (TRACULA) procedure available as part of the FreeSurfer image processing software package. For each fiber bundle, the mean fractional anisotropy (FA), and mean, radial and axial diffusivities were calculated. Individuals with AD had increased diffusivities in both left and right cingulum-angular bundles compared to control participants (p<0.001). Individuals with MCI also had increased axial and mean diffusivities and increased FA in both cingulum-angular bundles compared to control participants (p<0.05) and decreased radial diffusivity compared to individuals with AD (p<0.05). We additionally examined how white matter deterioration relates to hippocampal volume, a traditional imaging measure of AD pathology, and found the strongest negative correlations in AD patients between hippocampal volume and the diffusivities of the cingulum-angular and cingulum-cingulate gyrus bundles and of the corticospinal tracts (p<0.05). However, statistically controlling for hippocampal volume did not remove all group differences in white matter measures, suggesting a unique contribution of white matter damage to AD unexplained by this disease biomarker. These results suggest that (1) AD-associated deterioration of white matter fibers is greatest in tracts known to be connected to areas of pathology in AD and (2) lower white matter tract integrity is more diffusely associated with lower hippocampal volume indicating that the pathology in the white matter follows to some degree the neurodegenerative staging and progression of this condition.

Strategic lesions in the anterior thalamic radiation and apathy in early Alzheimer's disease

BACKGROUND

Behavioural disorders and psychological symptoms of Dementia (BPSD) are commonly observed in Alzheimer's disease (AD), and strongly contribute to increasing patients' disability. Using voxel-lesion-symptom mapping (VLSM), we investigated the impact of white matter lesions (WMLs) on the severity of BPSD in patients with amnestic mild cognitive impairment (a-MCI).

METHODS

Thirty-one a-MCI patients (with a conversion rate to AD of 32% at 2 year follow-up) and 26 healthy controls underwent magnetic resonance imaging (MRI) examination at 3T, including T2-weighted and fluid-attenuated-inversion-recovery images, and T1-weighted volumes. In the patient group, BPSD was assessed using the Neuropsychiatric Inventory-12. After quantitative definition of WMLs, their distribution was investigated, without an a priori anatomical hypothesis, against patients' behavioural symptoms. Unbiased regional grey matter volumetrics was also used to assess the contribution of grey matter atrophy to BPSD.

RESULTS

Apathy, irritability, depression/dysphoria, anxiety and agitation were shown to be the most common symptoms in the patient sample. Despite a more widespread anatomical distribution, a-MCI patients did not differ from controls in WML volumes. VLSM revealed a strict association between the presence of lesions in the anterior thalamic radiations (ATRs) and the severity of apathy. Regional grey matter atrophy did not account for any BPSD.

CONCLUSIONS

This study indicates that damage to the ATRs is strategic for the occurrence of apathy in patients with a-MCI. Disconnection between the prefrontal cortex and the mediodorsal and anterior thalamic nuclei might represent the pathophysiological substrate for apathy, which is one of the most common psychopathological symptoms observed in dementia.

Vascular risk factor burden correlates with cerebrovascular reactivity but not resting state coactivation in the default mode network

PURPOSE

White matter hyperintensities (WMH) are prevalent among older adults and are often associated with cognitive decline and increased risk of stroke and dementia. Vascular risk factors (VRFs) are linked to WMH, yet the impact of multiple VRFs on gray matter function is still unclear. The goal of this study was to test for associations between the number of VRFs and cerebrovascular reactivity (CVR) and resting state (RS) coactivation among individuals with WMH.

MATERIALS AND METHODS

Twenty-nine participants with suspected WMH were grouped based on the number of VRFs (subgroups: 0, 1, or ≥2). CVR and RS coactivation were measured with blood oxygenation level-dependent (BOLD) imaging on a 3T magnetic resonance imaging (MRI) system during hypercapnia and rest, respectively. Default-mode (DMN), sensory-motor, and medial-visual networks, generated using independent component analysis of RS-BOLD, were selected as networks of interest (NOIs). CVR-BOLD was analyzed using two methods: 1) a model-based approach using CO2 traces, and 2) a dual-regression (DR) approach using NOIs as spatial inputs. Average CVR and RS coactivations within NOIs were compared between VRF subgroups. A secondary analysis investigated the correlation between CVR and RS coactivation.

RESULTS

VRF subgroup differences were detected using DR-based CVR in the DMN (F20,2  = 5.17, P = 0.015) but not the model-based CVR nor RS coactivation. DR-based CVR was correlated with RS coactivation in the DMN (r(2)  = 0.28, P = 0.006) but not the sensory-motor nor medial-visual NOIs.

CONCLUSION

In individuals with WMH, CVR in the DMN was inversely associated with the number of VRFs and correlated with RS coactivation.

Association of white matter hyperintensities and gray matter volume with cognition in older individuals without cognitive impairment

Both presence of white matter hyperintensities (WMH) and smaller total gray matter volume on brain magnetic resonance imaging (MRI) are common findings in old age, and contribute to impaired cognition. We tested whether total WMH volume and gray matter volume had independent associations with cognition in community-dwelling individuals without dementia or mild cognitive impairment (MCI). We used data from participants of the Rush Memory and Aging Project. Brain MRI was available in 209 subjects without dementia or MCI (mean age 80; education = 15 years; 74 % women). WMH and gray matter were automatically segmented, and the total WMH and gray matter volumes were measured. Both MRI-derived measures were normalized by the intracranial volume. Cognitive data included composite measures of five different cognitive domains, based on 19 individual tests. Linear regression analyses, adjusted for age, sex, and education, were used to examine the relationship of logarithmically-transformed total WMH volume and of total gray matter volume to cognition. Larger total WMH volumes were associated with lower levels of perceptual speed (p < 0.001), but not with episodic memory, semantic memory, working memory, or visuospatial abilities (all p > 0.10). Smaller total gray matter volumes were associated with lower levels of perceptual speed (p = 0.013) and episodic memory (p = 0.001), but not with the other three cognitive domains (all p > 0.14). Larger total WMH volume was correlated with smaller total gray matter volume (p < 0.001). In a model with both MRI-derived measures included, the relation of WMH to perceptual speed remained significant (p < 0.001), while gray matter volumes were no longer related (p = 0.14). This study of older community-dwelling individuals without overt cognitive impairment suggests that the association of larger total WMH volume with lower perceptual speed is independent of total gray matter volume. These results help elucidate the pathological processes leading to lower cognitive function in aging.

Blood-brain barrier breakdown in the aging human hippocampus

The blood-brain barrier (BBB) limits entry of blood-derived products, pathogens, and cells into the brain that is essential for normal neuronal functioning and information processing. Post-mortem tissue analysis indicates BBB damage in Alzheimer's disease (AD). The timing of BBB breakdown remains, however, elusive. Using an advanced dynamic contrast-enhanced MRI protocol with high spatial and temporal resolutions to quantify regional BBB permeability in the living human brain, we show an age-dependent BBB breakdown in the hippocampus, a region critical for learning and memory that is affected early in AD. The BBB breakdown in the hippocampus and its CA1 and dentate gyrus subdivisions worsened with mild cognitive impairment that correlated with injury to BBB-associated pericytes, as shown by the cerebrospinal fluid analysis. Our data suggest that BBB breakdown is an early event in the aging human brain that begins in the hippocampus and may contribute to cognitive impairment.

VIDEO ABSTRACT

Classifying dementia using local binary patterns from different regions in magnetic resonance images

Dementia is an evolving challenge in society, and no disease-modifying treatment exists. Diagnosis can be demanding and MR imaging may aid as a noninvasive method to increase prediction accuracy. We explored the use of 2D local binary pattern (LBP) extracted from FLAIR and T1 MR images of the brain combined with a Random Forest classifier in an attempt to discern patients with Alzheimer's disease (AD), Lewy body dementia (LBD), and normal controls (NC). Analysis was conducted in areas with white matter lesions (WML) and all of white matter (WM). Results from 10-fold nested cross validation are reported as mean accuracy, precision, and recall with standard deviation in brackets. The best result we achieved was in the two-class problem NC versus AD + LBD with total accuracy of 0.98 (0.04). In the three-class problem AD versus LBD versus NC and the two-class problem AD versus LBD, we achieved 0.87 (0.08) and 0.74 (0.16), respectively. The performance using 3DT1 images was notably better than when using FLAIR images. The results from the WM region gave similar results as in the WML region. Our study demonstrates that LBP texture analysis in brain MR images can be successfully used for computer based dementia diagnosis.