Epidemiology of white matter lesions

Spontaneous white matter lesion in brain of stroke-prone renovascular hypertensive rats: a study from MRI, pathology and behavior

Hypertension is considered one of the most important controllable risk factors for white matter lesion (WML). Our previous work found that stroke-prone renovascular hypertensive rats (RHRSP) displayed a high rate of WML. This study aimed to investigate the WML in RHRSP from MRI, pathology and behavior. RHRSP model was established by two-kidney, two-clipmethod and kept for 20 weeks. WML was decteted by magnetic resonance imaging (MRI) and loyez staining. Cognition was tested by morris water maze (MWM). Vascular changes were observed by HE staining on brain and carotid sections. Ultrastucture of blood brain barrier (BBB) were observed by transmission electron microscope. Immunofluorescence was used to detect albumin leakage and cell proliferation. T(2)-weighted MRI scans of RHRSP displayed diffuse, confluent white-matter hyperintensities. Pathological examination of the same rat showed marked vacuoles, disappearence of myelin and nerve fibers in white matter, supporting the neuroimaging findings. Spatial learning and memory impairment were observed in RHRSP. The small arteries in brain exhibited fibrinoid necrosis, hyalinosis and vascular remodeling. BBB disruption and plasma albumin leakage into vascular wall was observed in RHRSP. Increased cell proliferation in subventricular zone was seen in RHRSP. RHRSP demonstrated spontaneous WML and cognitive impairment. Hypertensive small vessel lesions and BBB disruption might paly causative factors for the onset and development of WML. The characteristic features of WML in RHRSP suggested it a valid animal model for WML.

White matter changes in dementia: role of impaired drainage of interstitial fluid

White matter abnormalities on magnetic resonance imaging (MRI) are associated with dementia and include white matter hyperintensities (WMH; also termed leukoaraiosis) and visible perivascular spaces (PVS). We review the potential role of impaired drainage of interstitial fluid in the pathogenesis of WMH and PVS. Whereas the volume of extracellular space in the grey matter is tightly controlled, fluid accumulates and expands the extracellular spaces of the white matter in acute hydrocephalus, vasogenic edema and WMH. Although there are no conventional lymphatic vessels in the brain, there is very effective lymphatic drainage for fluid and solutes along restricted pathways in the basement membranes of cerebral capillaries and arteries in young individuals. Lymphatic drainage of the brain is impaired with age and in association with apolipoprotein E ε4, risk factors for Alzheimer's disease and cerebral amyloid angiopathy (CAA). Deposition of proteins in the lymphatic drainage pathways in the walls of cerebral arteries with age is recognized as protein elimination failure angiopathy (PEFA), as in CAA and cerebral autosomal dominant arteriopathy and leukoencephalopathy (CADASIL). Facilitating perivascular lymphatic drainage from the aging brain may play a significant role in the prevention of CAA, WMH and Alzheimer's disease and may enhance the efficacy of immunotherapy for Alzheimer's disease.

Hemispheric Differences in Leukoaraiosis in Patients with Carotid Artery Stenosis: A Systematic Review

PURPOSE

Despite the prevalence of leukoaraiosis in neuroimaging and its link to dementia, stroke, and death, the exact pathogenesis is still unclear. While some have postulated a link between carotid artery disease and leukoaraiosis, the exact relationship between the two common clinical findings is unknown. To determine the link between carotid disease and leukoaraiosis, we performed a systematic review of interhemispheric differences in white matter disease in patients with carotid artery disease.

METHODS

We performed a comprehensive literature search in multiple electronic databases evaluating the association of carotid artery and white matter disease using both subjective and volumetric assessment of white matter burden. The included studies examined patients with at least 30 % carotid artery stenosis for white matter burden both ipsilateral and contralateral to the site of carotid artery disease.

RESULTS

Of the 2920 manuscripts screened, five were included in the systematic review. One study used a volumetric analysis of the white matter burden and the others used various subjective methods. Four studies found no statistically significant relationship between carotid artery disease and ipsilateral white matter burden and one study found a significantly higher amount of white matter disease ipsilateral to carotid artery stenosis.

CONCLUSIONS

The mixed results in degree of hemispheric leukoaraiosis in patients with carotid artery disease indicate that no definite relationship can be established based on the existing literature. Given the complex nature of carotid artery disease, including increased risk with certain plaque components, the exact relationship requires further investigation with more rigorous research design.

Multiethnic genome-wide association study of cerebral white matter hyperintensities on MRI

BACKGROUND

The burden of cerebral white matter hyperintensities (WMH) is associated with an increased risk of stroke, dementia, and death. WMH are highly heritable, but their genetic underpinnings are incompletely characterized. To identify novel genetic variants influencing WMH burden, we conducted a meta-analysis of multiethnic genome-wide association studies.

METHODS AND RESULTS

We included 21 079 middle-aged to elderly individuals from 29 population-based cohorts, who were free of dementia and stroke and were of European (n=17 936), African (n=1943), Hispanic (n=795), and Asian (n=405) descent. WMH burden was quantified on MRI either by a validated automated segmentation method or a validated visual grading scale. Genotype data in each study were imputed to the 1000 Genomes reference. Within each ethnic group, we investigated the relationship between each single-nucleotide polymorphism and WMH burden using a linear regression model adjusted for age, sex, intracranial volume, and principal components of ancestry. A meta-analysis was conducted for each ethnicity separately and for the combined sample. In the European descent samples, we confirmed a previously known locus on chr17q25 (P=2.7×10(-19)) and identified novel loci on chr10q24 (P=1.6×10(-9)) and chr2p21 (P=4.4×10(-8)). In the multiethnic meta-analysis, we identified 2 additional loci, on chr1q22 (P=2.0×10(-8)) and chr2p16 (P=1.5×10(-8)). The novel loci contained genes that have been implicated in Alzheimer disease (chr2p21 and chr10q24), intracerebral hemorrhage (chr1q22), neuroinflammatory diseases (chr2p21), and glioma (chr10q24 and chr2p16).

CONCLUSIONS

We identified 4 novel genetic loci that implicate inflammatory and glial proliferative pathways in the development of WMH in addition to previously proposed ischemic mechanisms.

The relationship of leukoaraiosis and the clinical severity of vascular Parkinsonism

Vascular Parkinsonism (VP) is referred to as secondary Parkinsonian syndrome. It occurs with lacunar state or sub-cortical white matter micro-angiopathy and is highly associated with vascular risk factors and leukoaraiosis, also known as cerebral white matter lesions (WML). This study aimed to assess the prevalence of different vascular risk factors and WML in patients with VP, and their impact on clinical features. Sixty-two consecutive VP patients (70.2 ± 9.2 years) were evaluated for clinical severity using the Unified Parkinson's Disease Rating Scale (UPDRS). WML was assessed and scored on fluid-attenuated inversion recovery T2-weighted (FLAIR) magnetic resonance imaging (MRI). Cerebro-vascular risk factors, WML severity, and the UPDRS for clinical disability were analyzed statistically. There were no associations between WML score and age, sex, hypertension, diabetes, previous stroke, cardiac disease, cigarette smoking, or serum levels of cholesterol and triglyceride. The WML score positively correlated with UPDRS part I (p = 0.035) and part III (p = 0.041) scores. After adjustments for age, gender, stroke history, and use of levodopa, the WML score was associated with the UPDRS total (p = 0.020), part I (p = 0.012), part II (p = 0.039), and part III (p = 0.019) scores. The severity of WML is not associated with conventional vascular risk factors in VP patients but is significantly correlated with the UPDRS total and all sub-scores, which suggests that disruption of the cortico-sub-cortical circuits may lead to impaired mentation, behavior and mood, activities of daily living, and motor performance in these patients.

Stroke subtype, vascular risk factors, and total MRI brain small-vessel disease burden

Objectives:

In this cross-sectional study, we tested the construct validity of a “total SVD score,” which combines individual MRI features of small-vessel disease (SVD) in one measure, by testing associations with vascular risk factors and stroke subtype.

Methods:

We analyzed data from patients with lacunar or nondisabling cortical stroke from 2 prospective stroke studies. Brain MRI was rated for the presence of lacunes, white matter hyperintensities, cerebral microbleeds, and perivascular spaces independently. The presence of each SVD feature was summed in an ordinal “SVD score” (range 0–4). We tested associations with vascular risk factors, stroke subtype, and cerebral atrophy using ordinal regression analysis.

Results:

In 461 patients, multivariable analysis found that age (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.08–1.12), male sex (OR 1.58, 95% CI 1.10–2.29), hypertension (OR 1.50, 95% CI 1.02–2.20), smoking (OR 2.81, 95% CI 1.59–3.63), and lacunar stroke subtype (OR 2.45, 95% CI 1.70–3.54) were significantly and independently associated with the total SVD score. The score was not associated with cerebral atrophy.

Conclusions:

The total SVD score may provide a more complete estimate of the full impact of SVD on the brain, in a simple and pragmatic way. It could have potential for patient or risk stratification or early efficacy assessment in clinical trials of interventions to prevent SVD progression and may (after further testing) have a useful role in clinical practice.

Relationships between Personality Traits, Medial Temporal Lobe Atrophy, and White Matter Lesion in Subjects Suffering from Mild Cognitive Impairment

Mild cognitive impairment (MCI) is a heterogeneous cognitive status that can be a prodromal stage of Alzheimer's disease (AD). It is particularly relevant to focus on prodromal stages of AD such as MCI, because patho-physiological abnormalities of AD start years before the dementia stage. Medial temporal lobe (MTL) atrophy resulting from AD lesions and cerebrovascular lesions [i.e., white matter lesions (WML), lacunar strokes, and strokes] are often revealed concurrently on magnetic resonance imaging (MRI) in MCI subjects. Personality changes have been reported to be associated with MCI status and early AD. More specifically, an increase in neuroticism and a decrease in conscientiousness have been reported, suggesting that higher and lower scores, respectively, in neuroticism and conscientiousness are associated with an increased risk of developing the disease. However, personality changes have not been studied concomitantly with pathological structural brain alterations detected on MRI in patients suffering from MCI. Therefore, the objective of the present study was to assess the relationship between MTL atrophy, WML, lacunar strokes, and personality traits in such patients. The severity of WML was strongly associated with lower levels of conscientiousness and higher levels of neuroticism. Conversely, no association was detected between personality traits and the presence of lacunar strokes or MTL atrophy. Altogether, these results strongly suggest that personality changes occurring in a MCI population, at high risk of AD, are associated with WML, which can induce executive dysfunctions, rather than with MTL atrophy.

Contemplating Alzheimer's disease and the contribution of white matter hyperintensities

As the older adult segment of the population increases, Alzheimer's disease (AD) has emerged as a significant public health epidemic. Over the past 3 decades, advances in the understanding of the biology of AD have led to a somewhat unified hypothesis of disease pathogenesis that emphasizes the precipitating role of beta amyloid protein. However, several lines of evidence suggest that multiple pathologies are necessary for clinical manifestation of the disease. Our focus over the past several years has been on the contribution of small vessel cerebrovascular disease, visualized as white matter hyperintensities (WMH) on magnetic resonance imaging, to AD. White matter hyperintensity volume, particularly in parietal regions, is elevated among individuals with and at risk for AD, predicts future diagnosis of AD, predicts the rate of progression of cognitive symptoms among individuals with AD, and increases over time among individuals destined to develop AD. White matter hyperintensities may represent an independent source of impairment and/or may interact more fundamentally with "primary" AD pathology. Future work should focus on more inclusive models of that better define "normal" vs "pathological" aging.

Relation of subclinical coronary artery atherosclerosis to cerebral white matter disease in healthy subjects from families with early-onset coronary artery disease

White matter disease (WMD) of the brain is associated with incident stroke. Similarly, subclinical calcified coronary artery plaque has been associated with incident coronary artery disease (CAD) events. Although atherogenesis in both vascular beds may share some common mechanisms, the extent to which subclinical CAD is associated with WMD across age ranges in subjects with a family history of early-onset CAD remains unknown. We screened 405 apparently healthy participants in the Genetic Study of Atherosclerotic Risk for CAD risk factors and for the presence of noncalcified and calcified coronary plaque using dual-source multidetector cardiac computed tomographic angiography. The presence and volumes of WMD were assessed by 3-Tesla brain magnetic resonance imaging. Participants were 60% women, 36% African-American, mean age 51.6 ± 10.6 years. The overall prevalence of coronary plaque was 43.0%. Subjects with coronary plaque had significantly greater WMD volumes (median 1,222 mm³, interquartile range 448 to 3,871) compared with those without coronary plaque (median 551 mm³, interquartile range 105 to 1,523, p <0.001). In multivariate regression analysis, adjusting for age, gender, race, traditional risk factors, total brain volume, and intrafamilial correlations, the presence of coronary plaque was independently associated with WMD volume (p = 0.05). This study shows a significant association between WMD and noncalcified and calcified coronary plaque in healthy subjects, independent of age and risk factors. In conclusion, these findings support the premise of possible shared causal pathways in 2 vascular beds in families at increased risk for early-onset vascular disease.

Risk estimations, risk factors, and genetic variants associated with Alzheimer's disease in selected publications from the Framingham Heart Study

The study of Alzheimer's disease (AD) in the Framingham Heart Study (FHS), a multi-generational, community-based population study, began nearly four decades ago. In this overview, we highlight findings from seven prior publications that examined lifetime risk estimates for AD, environmental risk factors for AD, circulating and imaging markers of aging-related brain injury, and explorations on the genetics underlying AD. First, we describe estimations of the lifetime risk of AD. These estimates are distinguished from other measures of disease burden and have substantial public health implications. We then describe prospective studies of environmental AD risk factors: one examined the association between plasma levels of omega-3 fatty-acid and risk of incident AD, the other explored the association of diabetes to this risk in subsamples with specific characteristics. With evidence of inflammation as an underlying mechanism, we also describe findings from a study that compared the effects of serum cytokines and spontaneous production of peripheral blood mononuclear cell cytokines on AD risk. Investigating AD related endophenotypes increases sensitivity in identifying risk factors and can be used to explore pathophysiologic pathways between a risk factor and the disease. We describe findings of an association between large volume of white matter hyperintensities and a specific pattern of cognitive deficits in non-demented participants. Finally, we summarize our findings from two genetic studies: The first used genome-wide association (GWA) and family-based association methods to explore the genetic basis of cognitive and structural brain traits. The second is a large meta-analysis GWA study of AD, in which novel loci of AD susceptibility were found. Together, these findings demonstrate the FHS multi-directional efforts in investigating dementia and AD.

Incidence of cerebrovascular lesions in pure autonomic failure

In pure autonomic failure (PAF) - a rare form of primary dysautonomia - some patients show cerebrovascular lesions usually found in hypertensive subjects. In an autonomic laboratory records of patients with a definitive diagnosis of PAF having had cerebral imaging (cMRI, cCT) were analysed retrospectively. Tilt table data (supine/tilted), 24 hour blood pressure recordings (day/night) and serum catecholamine levels were correlated with cerebrovascular lesions and also compared to published normal values. 50 PAF patients (23 female, 27 male) were identified, mean age 67 years (sd 9.5). Out of these 35 (70%) had pathologic cerebral scans showing white matter lesions (WML) in 30, lacunar strokes in 5 and hemispheric stroke and microbleeds each in 1. Age and supine systolic blood pressure were significantly elevated in patients with pathologic scans (70 compared to 61 years [p=0.007], and 170 compared to 154 mmHg [p=0.045]). Out of 28 patients with WML and ambulatory blood pressure recordings available 24 were non-dippers. The data show that the frequency of WML is lower in PAF patients aged 60 to 80 years compared to age matched community based samples. Although PAF usually results in hypotension, a frequent complication is supine hypertension. Although the overall frequency of WML seems to be reduced in PAF, a number of patients with elevated supine systolic blood pressure (>160 mmHg) develop WML and some of these suffer stroke.

Do brain T2/FLAIR white matter hyperintensities correspond to myelin loss in normal aging? A radiologic-neuropathologic correlation study

Background

White matter hyperintensities (WMH) lesions on T2/FLAIR brain MRI are frequently seen in healthy elderly people. Whether these radiological lesions correspond to irreversible histological changes is still a matter of debate. We report the radiologic-histopathologic concordance between T2/FLAIR WMHs and neuropathologically confirmed demyelination in the periventricular, perivascular and deep white matter (WM) areas.

Results

Inter-rater reliability was substantial-almost perfect between neuropathologists (kappa 0.71 - 0.79) and fair-moderate between radiologists (kappa 0.34 - 0.42). Discriminating low versus high lesion scores, radiologic compared to neuropathologic evaluation had sensitivity / specificity of 0.83 / 0.47 for periventricular and 0.44 / 0.88 for deep white matter lesions. T2/FLAIR WMHs overestimate neuropathologically confirmed demyelination in the periventricular (p < 0.001) areas but underestimates it in the deep WM (0 < 0.05). In a subset of 14 cases with prominent perivascular WMH, no corresponding demyelination was found in 12 cases.

Conclusions

MRI T2/FLAIR overestimates periventricular and perivascular lesions compared to histopathologically confirmed demyelination. The relatively high concentration of interstitial water in the periventricular / perivascular regions due to increasing blood–brain-barrier permeability and plasma leakage in brain aging may evoke T2/FLAIR WMH despite relatively mild demyelination.

Aortic pulse wave velocity predicts focal white matter hyperintensities in a biracial cohort of older adults

Although the cross-sectional relationship of arterial stiffness with cerebral small vessel disease is consistently shown in middle-aged and young-old adults, it is less clear whether these associations remain significant over time in very old adults. We hypothesize that arterial stiffness is longitudinally associated with white matter characteristics, and associations are stronger within watershed areas. Neuroimaging was obtained in 2006-2008 from 303 elderly (mean age 82.9 years, 59% women, 41% black) with pulse wave velocity (PWV) measures in 1997-1998. Multivariable regression models estimated the coefficients for PWV (cm/sec) in relationship to presence, severity, and spatial distribution of white matter hyperintensities (WMH), gray matter volume, and fractional anisotropy from diffusion tensor, adjusting for demographic, cardiovascular risk factors, and diseases from 1997-1998 to 2006-2008. Higher PWV in 1997-1998 was associated with greater WMH volume in 2006-2008 within the left superior longitudinal fasciculus (age and total brain WMH adjusted, P=0.023), but not with WMH in other tracts or with fractional anisotropy or gray matter volume from total brain (P>0.2). Associations were stronger in blacks than in whites, remaining significant in fully adjusted models. Elderly with WMH in tracts related to processing speed and memory are more likely to have had higher PWV values 10 years prior, before neuroimaging data being available. Future studies should address whether arterial stiffness can serve as an early biomarker of covert brain structural abnormalities and whether early arterial stiffness control can promote successful brain aging, especially in black elderly.

Protocol for a randomized controlled trial evaluating the effect of physical activity on delaying the progression of white matter changes on MRI in older adults with memory complaints and mild cognitive impairment: the AIBL Active trial

BACKGROUND

Older adults free of dementia but with subjective memory complaints (SMC) or mild cognitive impairment (MCI) are considered at increased risk of cognitive decline. Vascular risk factors (VRF), including hypertension, heart disease, smoking, hypercholesterolemia and lack of physical activity (PA) have been identified as modifiable risk factors contributing to cognitive decline, and white matter hyperintensities (WMH) are associated with VRF, SMC and cognitive impairment. Findings from a growing number of clinical trials with older adults are providing strong evidence for the benefits of physical activity for maintaining cognitive function, but few studies are investigating these benefits in high-risk populations. The aim of AIBL Active is to determine whether a 24-month physical activity program can delay the progression of white matter changes on magnetic resonance imaging (MRI).

METHODS/DESIGN

This single-blind randomized controlled trial (RCT) is offered to 156 participants, aged 60 and older, in the Melbourne arm of the Australian Imaging Biomarkers and Lifestyle Flagship Study of Aging (AIBL). Participants must have SMC with or without MCI and at least one VRF. The PA intervention is a modification of the intervention previously trialed in older adults with SMC and MCI (Fitness for the Ageing Brain Study). It comprises 24 months of moderate, home-based PA (150 minutes per week) and a behavioral intervention package. The primary outcome measure will be change in WMH after 24 months on MRI. Cognition, quality of life, functional fitness, level of physical activity, plasma biomarkers for cerebrovascular disease and amyloid positron emission tomography (PET) imaging comprise secondary measures.

DISCUSSION

Currently, there is no effective pharmacological treatment available to delay cognitive decline and dementia in older adults at risk. Should our findings show that physical activity can slow down the progression of WMH, this RCT would provide an important proof of concept. Since imbedded in AIBL this RCT will also be able to investigate the interaction between vascular and Alzheimer's disease pathologies.

TRIAL REGISTRATION

Australia New Zealand Clinical Trials Registry ACTRN12611000612910.

Genetic risk factors for longitudinal changes in structural MRI in former organolead workers

This study examined associations between polymorphisms in three genes, apolipoprotein E (APOE), angiotensin converting enzyme (ACE), and vitamin D receptor (VDR), and longitudinal change in brain volumes and white matter lesions (WML) as well as effect modification by cardiovascular factors and tibia lead concentrations. Two MRIs, an average of 5 years apart, were obtained for 317 former organolead workers and 45 population-based controls. Both regions-of-interest and voxel-wise analyses were conducted. APOE ε3/ε4 and ε4/ε4 genotypes were associated with less decline in white matter volumes. There was some evidence of interaction between genetic polymorphisms and cardiovascular risk factors (ACE and high-density lipoprotein; VDR and diabetes) on brain volume decline. The VDR FokI ff genotype was associated with an increase in WML (no association for APOE or ACE). This study expands our understanding of how genetic precursors of dementia and cardiovascular diseases are related to changes in brain structure.

The Rotterdam Scan Study: design and update up to 2012

Neuroimaging plays an important role in etiologic research on neurological diseases in the elderly. The Rotterdam Scan Study was initiated as part of the ongoing Rotterdam Study with the aim to unravel causes of neurological disease by performing neuroimaging in a population-based longitudinal setting. In 1995 and 1999 random subsets of the Rotterdam Study underwent neuroimaging, whereas from 2005 onwards MRI has been implemented into the core protocol of the Rotterdam Study. In this paper, we discuss the background and rationale of the Rotterdam Scan Study. We also describe the imaging protocol and post-processing techniques, and highlight the main findings to date. Finally, we make recommendations for future research, which will also be the main focus of investigation in the Rotterdam Scan Study.

Connecting cerebral white matter lesions and hypertensive target organ damage

Chronic hypertension leads to concomitant remodeling of the cardiac and vascular systems and various organs, especially the brain, kidney, and retina. The brain is an early target of organ damage due to high blood pressure, which is the major modifiable risk factor for stroke and small vessel disease. Stroke is the second leading cause of death and the number one cause of disability worldwide and over 80% of strokes occur in the elderly. Preclinical hypertensive lesions in most target organs are clearly identified: left ventricular hypertrophy for the heart, microalbuminuria for the kidney, fundus abnormalities for the eye, and intima-media thickness and pulse wave velocity for the vessels. However, early hypertensive brain damage is not fully studied due to difficulties in access and the expense of techniques. After age, hypertension is the most-important risk factor for cerebral white matter lesions, which are an important prognostic factor for stroke, cognitive impairment, dementia, and death. Studies have shown an association between white matter lesions and a number of extracranial systems affected by high BP and also suggest that correct antihypertensive treatment could slow white matter lesions progression. There is strong evidence that cerebral white matter lesions in hypertensive patients should be considered a silent early marker of brain damage.

Genome-wide association studies of cerebral white matter lesion burden: the CHARGE consortium

OBJECTIVE

White matter hyperintensities (WMHs) detectable by magnetic resonance imaging are part of the spectrum of vascular injury associated with aging of the brain and are thought to reflect ischemic damage to the small deep cerebral vessels. WMHs are associated with an increased risk of cognitive and motor dysfunction, dementia, depression, and stroke. Despite a significant heritability, few genetic loci influencing WMH burden have been identified.

METHODS

We performed a meta-analysis of genome-wide association studies (GWASs) for WMH burden in 9,361 stroke-free individuals of European descent from 7 community-based cohorts. Significant findings were tested for replication in 3,024 individuals from 2 additional cohorts.

RESULTS

We identified 6 novel risk-associated single nucleotide polymorphisms (SNPs) in 1 locus on chromosome 17q25 encompassing 6 known genes including WBP2, TRIM65, TRIM47, MRPL38, FBF1, and ACOX1. The most significant association was for rs3744028 (p(discovery) = 4.0 × 10(-9) ; p(replication) = 1.3 × 10(-7) ; p(combined) = 4.0 × 10(-15) ). Other SNPs in this region also reaching genome-wide significance were rs9894383 (p = 5.3 × 10(-9) ), rs11869977 (p = 5.7 × 10(-9) ), rs936393 (p = 6.8 × 10(-9) ), rs3744017 (p = 7.3 × 10(-9) ), and rs1055129 (p = 4.1 × 10(-8) ). Variant alleles at these loci conferred a small increase in WMH burden (4-8% of the overall mean WMH burden in the sample).

INTERPRETATION

This large GWAS of WMH burden in community-based cohorts of individuals of European descent identifies a novel locus on chromosome 17. Further characterization of this locus may provide novel insights into the pathogenesis of cerebral WMH.

The clinical importance of white matter hyperintensities on brain magnetic resonance imaging: systematic review and meta-analysis

OBJECTIVES

To review the evidence for an association of white matter hyperintensities with risk of stroke, cognitive decline, dementia, and death.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed from 1966 to 23 November 2009.

STUDY SELECTION

Prospective longitudinal studies that used magnetic resonance imaging and assessed the impact of white matter hyperintensities on risk of incident stroke, cognitive decline, dementia, and death, and, for the meta-analysis, studies that provided risk estimates for a categorical measure of white matter hyperintensities, assessing the impact of these lesions on risk of stroke, dementia, and death.

DATA EXTRACTION

Population studied, duration of follow-up, method used to measure white matter hyperintensities, definition of the outcome, and measure of the association of white matter hyperintensities with the outcome.

DATA SYNTHESIS

46 longitudinal studies evaluated the association of white matter hyperintensities with risk of stroke (n=12), cognitive decline (n=19), dementia (n=17), and death (n=10). 22 studies could be included in a meta-analysis (nine of stroke, nine of dementia, eight of death). White matter hyperintensities were associated with an increased risk of stroke (hazard ratio 3.3, 95% confidence interval 2.6 to 4.4), dementia (1.9, 1.3 to 2.8), and death (2.0, 1.6 to 2.7). An association of white matter hyperintensities with a faster decline in global cognitive performance, executive function, and processing speed was also suggested.

CONCLUSION

White matter hyperintensities predict an increased risk of stroke, dementia, and death. Therefore white matter hyperintensities indicate an increased risk of cerebrovascular events when identified as part of diagnostic investigations, and support their use as an intermediate marker in a research setting. Their discovery should prompt detailed screening for risk factors of stroke and dementia.

Functional consequences of subcortical white matter lesions and MRI-defined brain infarct in an elderly general population

The impact of single and combined effects of subcortical white matter lesions (WMLs) and magnetic resonance imaging (MRI)-defined brain infarct on activities of daily living (ADL), depression, and health status perception was analyzed in community-dwelling elderly individuals. The study included 268 participants from the Memory and Morbidity in Augsburg Elderly (MEMO) project, a population-based study on individuals aged 65 to 83 years, conducted in Augsburg, Germany. Cerebral MRI was performed, and 2 geriatric performance tests, scales to assess ADL, depressive symptoms, and self-perceived health status were assessed. The prevalence of large (>10 mm) subcortical WML was 37.7% and of MRI-defined infarct-like lesions was 15.3%. Both vascular lesion types combined were found in 9% of the participants. Large WMLs were associated with significantly more impairments in basic ADL, inferior results in the performance tests, and a worse self-perceived health status compared to those without large WML. Magnetic resonance imaging-defined brain infarct was associated with impairments in performance tests. Participants with both lesion types were limited in all domains and were 2 to 3 times more likely to have impairments in all examined functions. Their risk of impairment in a specific function was considerably higher than the sum of the single risks associated with each lesion type alone. This study suggests that the single and especially the combined occurrence of common vascular brain lesions are associated with functional impairment. Identifying individuals with severe WML combined with MRI-defined brain infarct can help better understand the development of marked impairments in old age.

Microvascular lesions in the brain and retina: The age, gene/environment susceptibility-Reykjavik study

OBJECTIVE

To investigate whether the severity and location of cerebral white matter hyperintensities (WMHs) and brain infarcts are correlated with the signs of retinal microvascular abnormalities in the elderly.

METHODS

The study included 4,176 men and women (mean age, 76 years) who participated in the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study. Digital retinal images of both dilated eyes were taken and evaluated for the presence of retinal focal arteriolar signs (focal arteriolar narrowing and arteriovenous nicking) and retinopathy lesions (retinal blot hemorrhages and microaneurysms). Brain magnetic resonance imaging scans were acquired and evaluated for the presence and distribution of cerebral infarcts and WMHs. Logistic and multinomial logistic models were constructed to estimate the association of retinal microvascular signs to brain lesions.

RESULTS

Controlling for demographic and major cardiovascular risk factors, we found that retinal focal arteriolar signs, but not retinopathy lesions, were significantly associated with an increasing load of subcortical and periventricular WMHs. The strongest association was found between retinal arteriolar signs and a heavier WMH load, specifically in the subcortical frontal lobe, and periventricular frontal and parietal caps. There was a tendency toward bilateral retinal focal arteriolar narrowing being more strongly associated with the heavier load of subcortical WMHs. Arteriovenous nicking was significantly associated with subcortical infarcts.

INTERPRETATION

In older adults, retinal focal arteriolar signs, but not retinopathy lesions, are correlated with the load of diffuse WMHs, particularly those located in the subcortical frontal lobe, and the periventricular frontal and parietal caps of the brain.

Prefrontal myo-inositol concentration and visuospatial functioning among diabetic depressed patients

Patients with diabetes mellitus are reported to be at higher risk for developing neuropsychiatric disorders such as dementia and depression. Myo-inositol (mI), a neuronal/glial metabolite associated with multiple functions in the brain, has been shown to be increased in cognitive disorders, depression and diabetes. This study examined whether elevations in dorsolateral (DL) mI of diabetic patients with depression were associated with visuospatial deficits. Diabetic and depressed patients (n=18) were matched with patients with diabetes but without depression (n=20) and control subjects (n=19). Subjects were scored on both the recall and recognition tasks of the Rey-Osterreith Complex Figure (ROCF). Proton magnetic spectroscopy spectra from bilateral prefrontal white matter voxels were used to obtain concentrations of mI. Controls showed negative correlations between mI in right DL white matter and recall and recognition subtests. No correlation was observed for depressed diabetic patients. Correlations for diabetic controls fell midway between the comparison and depressed diabetic groups. The expected pattern of association between mI and visuospatial impairment in the right DL prefrontal region was seen among healthy controls. Progressive weakening of this association across both diabetic groups might be related to progressive changes in neural activity that underlies visuospatial function.

Retinal and cerebral microvascular signs and diabetes: the age, gene/environment susceptibility-Reykjavik study

OBJECTIVE

Diabetes increases the risk for microvascular disease. The retina and the brain both have intricate microvascular systems that are developmentally similar. We sought to examine whether microvascular lesions in the retina and in the brain are associated and whether this association differs among people with and without diabetes.

RESEARCH DESIGN AND METHODS

The analysis included 4,218 participants of the Icelandic population-based Age, Gene/Environment Susceptibility-Reykjavik Study who were born in 1907-1935 and who were previously followed as a part of the Reykjavik Study. Retinal focal arteriolar narrowing, arteriovenous (AV) nicking, and microaneurysms/hemorrhages were evaluated on digital retinal images of both eyes. Cerebral microbleeds (CMBs) were evaluated from magnetic resonance images. Data were analyzed with logistic and multinomial logistic regression models controlling for demographics, major cardiovascular risk factors, cerebral infarcts, and white matter lesions.

RESULTS

Evidence of brain microbleeds was found in 485 (11.5%) people, including 192 with multiple (>or=2) microbleeds. Subjects with signs of retinal microvascular lesions were at a significantly increased likelihood for having multiple CMBs. People with diabetes in combination with the presence of either retinal AV nicking (odds ratio [OR] 2.47 [95% CI 1.42-4.31]) or retinal microaneurysms/hemorrhages (2.28 [1.24-4.18]) were significantly more likely to have multiple CMBs.

CONCLUSIONS

Retinal microvascular abnormalities and brain microbleeds may occur together in older adults. People with both diabetes and signs of retinal microvascular lesions (AV nicking and microaneurysms/hemorrhages) are more likely to have multiple microbleeds in the brain. Microvascular disease in diabetes extends to the brain.

Selective reduction of blood flow to white matter during hypercapnia corresponds with leukoaraiosis

BACKGROUND AND PURPOSE

Age-related white matter disease (leukoaraiosis) clusters in bands in the centrum semiovale, about the occipital and frontal horns of the lateral ventricles, in the corpus callosum, and internal capsule. Cerebrovascular anatomy suggests that some of these locations represent border zones between arterial supply territories. We hypothesized that there are zones of reduced cerebrovascular reserve (susceptible to selective reductions in blood flow, ie, steal phenomenon) in the white matter of young, healthy subjects, the physiological correlate of these anatomically defined border zones. Furthermore, we hypothesized that these zones spatially correspond with the regions where the elderly develop leukoaraiosis.

METHODS

Twenty-eight healthy volunteers underwent functional MR mapping of the cerebrovascular response to hypercapnia. We studied 18 subjects by blood oxygen level-dependent MRI and 10 subjects by arterial spin labeling MRI. We controlled both end-tidal pCO(2) and pO(2). All functional data was registered in Montreal Neurological Institute space and generated composite blood oxygen level-dependent MR and arterial spin labeling MR maps of cerebrovascular reserve. We compared these maps with frequency maps of leukoaraiosis published previously.

RESULTS

Composite maps demonstrated significant (90% CI excluding the value zero) steal phenomenon in the white matter. This steal was induced by relatively small changes in end-tidal pCO(2). It occurred precisely in those locations where elderly patients develop leukoaraiosis.

CONCLUSIONS

This steal phenomenon likely represents the physiological correlate of the previously anatomically defined internal border zones. Spatial concordance with white matter changes in the elderly raises the possibility that this steal phenomenon may have a pathogenetic role.

Total cerebral blood flow, white matter lesions and brain atrophy: the SMART-MR study

We investigated whether total cerebral blood flow (CBF) was associated with brain atrophy, and whether this relation was modified by white matter lesions (WML). Within the Second Manifestations of ARTerial disease-magnetic resonance (SMART-MR) study, a prospective cohort study among patients with arterial disease, cross-sectional analyses were performed in 828 patients (mean age 58+/-10 years, 81% male) with quantitative flow, atrophy, and WML measurements on magnetic resonance imaging (MRI). Total CBF was measured with MR angiography and was expressed per 100 mL brain volume. Total brain volume and ventricular volume were divided by intracranial volume to obtain brain parenchymal fraction (BPF) and ventricular fraction (VF). Lower BPF indicates more global brain atrophy, whereas higher VF indicates more subcortical brain atrophy. Mean CBF was 52.0+/-10.2 mL/min per 100 mL, mean BPF was 79.2+/-2.9%, and mean VF was 2.03+/-0.96%. Linear regression analyses showed that lower CBF was associated with more subcortical brain atrophy, after adjusting for age, sex, vascular risk factors, intima-media thickness, and lacunar infarcts, but only in patients with moderate to severe WML (upper quartile of WML): Change in VF per s.d. decrease in CBF 0.18%, 95% CI: 0.02 to 0.34%. Our findings suggest that cerebral hypoperfusion in the presence of WML may be associated with subcortical brain atrophy.

Caudate nucleus hypointensity in the elderly is associated with markers of neurodegeneration on MRI

In this study we investigated patterns of hypointense basal ganglia on T2*-weighted magnetic resonance imaging (MRI) in 413 non-demented elderly (range: 70-82 years, mean 77 years; male/female: 177/239). In addition, we assessed associations between these patterns and age-related changes in the brain. Three patterns were noted: hypointensity limited to the globus pallidus (group I; n=30; 7%), hypointensity of both globus pallidus and putamen (group II; n=272; 66%), and hypointensity of globus pallidus, putamen and caudate nucleus (group III; n=111; 27%). Group III demonstrated a higher volume of white matter hyperintensities, more atrophy, decreased whole brain magnetization transfer ratios and increased T2-values compared to groups I and II. No differences were observed between groups I and II. From this study we conclude that hypointensity of the caudate nucleus is associated with a higher load of age-related cerebral changes. These data suggest that hypointensity of the caudate nucleus could be a new biomarker of age-related changes in the brain.

Brain Lesions on MRI in Elderly Patients with Type 2 Diabetes Mellitus

BACKGROUND AND PURPOSE

Diabetes mellitus (DM) type 2 has been associated with poor cognitive performance and dementia, particularly in elderly patients. The exact mechanisms underlying the cognitive dysfunction in DM remain unclear. Imaging studies of the brain could be helpful to give more insight into possible structural brain lesions underlying these cognitive dysfunctions. Therefore, we performed a study in independently living patients with DM type 2 in order to investigate the association between DM and brain imaging abnormalities.

METHODS

The study population consisted of 45 patients with DM type 2 without hypertension (mean age 73.4 +/- 5.1 years, mean duration 16.5 +/- 11.5 years), 45 patients with DM type 2 and hypertension (mean age 73.5 +/- 6.1 years, mean duration 11.9 +/- 9.2 years) and 44 control subjects (mean age 73.1 +/- 5.4 years). All patients and control subjects underwent an MRI of the brain. White matter lesions (WML), cerebral atrophy and medial temporal lobe atrophy were rated by a standardized visual rating scale. Lacunar infarcts were defined as focal hypo-intensities on fluid-attenuated inversion recovery sequences with a hyperintense rim around it.

RESULTS

WML occurred more frequently in diabetic patients with hypertension as well as without hypertension. Significantly more deep WML were found in DM patients with and without hypertension when compared to control subjects, whereas no difference was found in the occurrence of periventricular hyperintensities. In all 3 groups, lacunar infarcts occurred sporadically. A trend towards higher atrophy scores was seen in patients with DM compared to control subjects.

CONCLUSIONS

The data of this cross-sectional study suggest that type 2 DM is an independent risk factor for deep WML in the independently living elderly patients.