Heterogeneity in age-related white matter changes

Spatial Gradient of Microstructural Changes in Normal-Appearing White Matter in Tracts Affected by White Matter Hyperintensities in Older Age

Background and Purpose: White matter hyperintensities (WMH) are commonly seen on structural MRI of older adults and are a manifestation of underlying and adjacent tissue damage. WMH may contribute to cortical disconnection and cognitive dysfunction, but it is unclear how WMH affect intersecting or nearby white matter tract integrity. This study investigated the effects of WMH on tract microstructure by determining the spatial distribution of water diffusion characteristics in white matter tract areas adjacent to both intersecting and nearby WMH. Methods: We used diffusion and structural MRI data from 52 representative participants from the Lothian Birth Cohort 1936 (72.2 ± 0.7 years) including a range of WMH burden. We segmented WMH, reconstructed 18 main white mater tracts using automated quantitative tractography and identified intersections between tracts and WMH. We measured mean diffusivity (MD) and fractional anisotropy (FA) in tract tissue at 2 mm incremental distances from tract-intersecting and non-intersecting (nearby) WMH. Results: We observed a spatial gradient of FA and MD abnormalities for most white matter tracts which diminished with a similar distance pattern for tract-intersecting and nearby WMH. Overall, FA was higher, while MD was lower around nearby WMH compared with tract-intersecting WMH. However, for some tracts, FA was lower in areas immediately surrounding nearby WMH, although with faster normalization than in FA values surrounding tract-intersecting WMH. Conclusion: WMH have similar effects on tract infrastructure, whether they be intersecting or nearby. However, the observed differences in tract water diffusion properties around WMH suggest that degenerative processes in small vessel disease may propagate further along the tract for intersecting WMH, while in some areas of the brain there is a larger and more localized accumulation of axonal damage in tract tissue nearby a non-connected WMH. Longitudinal studies should address differential effects of intersecting vs. nearby WMH progression and how they contribute to cognitive aging.

Blood Pressure Control and Protection of the Aging Brain

Hypertension and dementia are both common disorders whose prevalence increases with age. There are multiple mechanisms by which hypertension affects the brain and alters cognition. These include blood flow dynamics, development of large and small vessel pathology and diverse molecular mechanisms including formation of reactive oxygen species and transcriptional cascades. Blood pressure interacts with Alzheimer disease pathology in numerous and unpredictable ways, affecting both β-amyloid and tau deposition, while also interacting with AD genetic risk factors and other metabolic processes. Treatment of hypertension may prevent cognitive decline and dementia, but methodological issues have limited the ability of randomized clinical trials to show this conclusively. Recent studies have raised hope that hypertension treatment may protect the function and structure of the aging brain from advancing to mild cognitive impairment and dementia.

Neurodegenerative Diseases and Ageing

This chapter describes the main neuropathological features of the most common age associated neurodegenerative diseases including Alzheimer's disease, Lewy body diseases, vascular dementia and the various types of frontotemporal lobar degeneration. In addition, the more recent concepts of primary age-related tauopathy and ageing-related tau astrogliopathy as well as chronic traumatic encephalopathy are briefly described. One section is dedicated to cerebral multi-morbidity as it is becoming increasingly clear that the old brain is characterised by the presence of multiple pathologies (to varying extent) rather than by one single, disease specific pathology alone. The main aim of this chapter is to inform the reader about the neuropathological basics of age associated neurodegenerative diseases as we feel this is crucial to meaningfully interpret the vast literature that is published in the broad field of dementia research.

Activated Microglia in Cortical White Matter Across Cognitive Aging Trajectories

Activation of microglia, the primary mediators of inflammation in the brain, is a major component of gliosis and neuronal loss in a number of age-related neurodegenerative disorders, such as Alzheimer’s disease (AD). The role of activated microglia in white matter, and its relationship with cognitive decline during aging are unknown. The current study evaluated microglia densities in the white matter of postmortem specimens from cognitively normal young adults, cognitively normal older adults, and cognitive “SuperAgers,” a unique group of individuals over age 80 whose memory test scores are at a level equal to or better than scores of 50-to-65-year-olds. Whole hemisphere sections from cognitively normal old, young, and “SuperAgers” were used to quantify densities of human leukocyte antigen-D related (HLA-DR)-positive activated microglia underlying five cortical regions. Statistical findings showed a significant main effect of group on differences in microglia density where cognitively normal old showed highest densities. No difference between SuperAgers and young specimens were detected. In two autopsied SuperAgers with MRI FLAIR scans available, prominent hyperintensities in periventricular regions were observed, and interestingly, examination of corresponding postmortem sections showed only sparse microglia densities. In conclusion, activated microglia appear to respond to age-related pathologic changes in cortical white matter, and this phenomenon is largely spared in SuperAgers. Findings offer insights into the relationship between white matter neuroinflammatory changes and cognitive integrity during aging.

White matter lesions and sudden sensorineural hearing loss

Aim of this paper is to investigate the presence of White Matter Lesions (WMLs) in subjects affected by Sudden Sensorineural Hearing Loss (SSNHL) and possibly to evaluate the significance of WMLs in SSNHL patients. A total of 64 patients (cases) affected by SSNHL were included in this case-control study. Hearing tests were performed at SSNHL onset, after 7 days and after 30 days. Cerebral MRI sequences were performed to rule out retrocochlear pathology, and WMLs were evaluated if present. MRI control group included 32 subjects, without hearing loss, affected by pituitary adenoma, who underwent cerebral MRI of follow-up. WML presence in those affected by SSNHL resulted having a similar distribution to that of the control group; however, we observed complete hearing recovery in 42,9% of patients without WML and in 11,6% of patients with WML >1 (p = 0,017^*). The incidence of WML in patients with SSNHL was not different compared to that of the control group; however, MRI could have a prognostic role for SSNHL patients, as the presence of WMLs can been linked to a poorer hearing recovery rate.

Increased Water Content in Periventricular Caps in Patients without Acute Hydrocephalus

BACKGROUND AND PURPOSE

Periventricular caps are a common finding on MR imaging and are believed to reflect focally increased interstitial water content due to dysfunctional transependymal transportation rather than ischemic-gliotic changes. We compared the quantitative water content of periventricular caps and microvascular white matter lesions, hypothesizing that periventricular caps associated with increased interstitial fluid content display higher water content than white matter lesions and are therefore differentiable from microvascular white matter lesions by measurement of the water content.

MATERIALS AND METHODS

In a prospective study, we compared the water content of periventricular caps and white matter lesions in 50 patients using a quantitative multiple-echo, gradient-echo MR imaging water-mapping sequence.

RESULTS

The water content of periventricular caps was significantly higher than that of white matter lesions (P = .002). Compared with normal white matter, the mean water content of periventricular caps was 17% ± 5% higher and the mean water content of white matter lesions was 11% ± 4% higher. Receiver operating characteristic analysis revealed that areas in which water content was 15% higher compared with normal white matter correspond to periventricular caps rather than white matter lesions, with a specificity of 93% and a sensitivity of 60% (P < .001). There was no significant correlation between the water content of periventricular caps and whole-brain volume (P = .275), white matter volume (P = .243), gray matter volume (P = .548), lateral ventricle volume (P = .800), white matter lesion volume (P = .081), periventricular cap volume (P = .081), and age (P = .224).

CONCLUSIONS

Quantitative MR imaging allows differentiation between periventricular caps and white matter lesions. Water content quantification of T2-hyperintense lesions may be a useful additional tool for the characterization and differentiation of T2-hyperintense diseases.

Brain White Matter Hyperintensity Lesion Characterization in T2 Fluid-Attenuated Inversion Recovery Magnetic Resonance Images: Shape, Texture, and Potential Growth

Prior methods in characterizing age-related white matter hyperintensity (WMH) lesions on T₂ fluid-attenuated inversion recovery (FLAIR) magnetic resonance images (MRI) have mainly been limited to understanding the sizes of, and occasionally the locations of WMH lesions. Systematic morphological characterization has been missing. In this work, we proposed innovative methods to fill this knowledge gap. We developed an innovative and proof-of-concept method to characterize and quantify the shape (based on Zernike transformation) and texture (based on fuzzy logic) of WMH lesions. We have also developed a multi-dimension feature vector approach to cluster WMH lesions into distinctive groups based on their shape and then texture features. We then developed an approach to calculate the potential growth index (PGI) of WMH lesions based on the image intensity distributions at the edge of the WMH lesions using a region-growing algorithm. High-quality T₂ FLAIR images containing clearly identifiable WMH lesions with various sizes from six cognitively normal older adults were used in our method development Analyses of Variance (ANOVAs) showed significant differences in PGI among WMH group clusters in terms of either the shape (P = 1.06 × 10⁻²) or the texture (P < 1 × 10⁻²⁰) features. In conclusion, we propose a systematic framework on which the shape and texture features of WMH lesions can be quantified and may be used to predict lesion growth in older adults.

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

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

White matter hyperintensities in vascular contributions to cognitive impairment and dementia (VCID): Knowledge gaps and opportunities

White matter hyperintensities (WMHs) are frequently seen on brain magnetic resonance imaging scans of older people. Usually interpreted clinically as a surrogate for cerebral small vessel disease, WMHs are associated with increased likelihood of cognitive impairment and dementia (including Alzheimer's disease [AD]). WMHs are also seen in cognitively healthy people. In this collaboration of academic, clinical, and pharmaceutical industry perspectives, we identify outstanding questions about WMHs and their relation to cognition, dementia, and AD. What molecular and cellular changes underlie WMHs? What are the neuropathological correlates of WMHs? To what extent are demyelination and inflammation present? Is it helpful to subdivide into periventricular and subcortical WMHs? What do WMHs signify in people diagnosed with AD? What are the risk factors for developing WMHs? What preventive and therapeutic strategies target WMHs? Answering these questions will improve prevention and treatment of WMHs and dementia.

Severity of White Matter Hyperintensities and Effects on All-Cause Mortality in the Mayo Clinic Florida Familial Cerebrovascular Diseases Registry

OBJECTIVE

To compare all-cause mortality rates across the severity range of white matter hyperintensities (WMH).

PATIENTS AND METHODS

Between October 26, 2010, and October 5, 2017, the ongoing Mayo Clinic Florida Familial Cerebrovascular Diseases Registry prospectively enrolled 1011 diverse participants with and without cerebrovascular disease. T2-weighted magnetic resonance imaging of the brain was used to evaluate WMH in 455 participants using the Fazekas scale. Fazekas deep WMH (FD) and periventricular WMH (FPV) scores (0-3 points) were assigned on the basis of WMH severity. Kaplan-Meier survival analyses, Cox proportional hazards models, and estimated hazard ratios compared survival rates across FD and FPV categories. The Fisher exact and χ² tests evaluated the relationship of categorical variables, and the Kruskal-Wallis test measured the relationship of continuous variables across FD and FPV categories. All tests were performed at a P<.05 significance level.

RESULTS

Over a median follow-up of 3.06 years (range, 0.00-6.96 years), 96 deaths occurred. Higher FD scores corresponded to a higher likelihood of mortality (P<.001). Participants with an FD score of 3 were 4.69 (95% CI, 2.60-8.46) times more likely to die compared with those with an FD score of 0. Participants with higher FPV scores had a higher likelihood of mortality (P<.001). Participants with an FPV score of 3 were 7.04 (95% CI, 3.39-14.62) times more likely to die compared with those with an FPV score of 0. Once adjusted, age and baseline functional status explained most of the survival differences among the FD scores.

CONCLUSION

Associations between all-cause mortality rates across the severity range of WMH were observed in the Registry. Further studies are warranted to understand the clinical importance of WMH in other clinical populations.

Spatial patterns of white matter hyperintensities associated with Alzheimer's disease risk factors in a cognitively healthy middle-aged cohort

Background

White matter hyperintensities (WMH) of presumed vascular origin have been associated with an increased risk of Alzheimer’s disease (AD). This study aims to describe the patterns of WMH associated with dementia risk estimates and individual risk factors in a cohort of middle-aged/late middle-aged individuals (mean 58 (interquartile range 51–64) years old).

Methods

Magnetic resonance imaging and AD risk factors were collected from 575 cognitively unimpaired participants. WMH load was automatically calculated in each brain lobe and in four equidistant layers from the ventricular surface to the cortical interface. Global volumes and regional patterns of WMH load were analyzed as a function of the Cardiovascular Risk Factors, Aging and Incidence of Dementia (CAIDE) dementia risk score, as well as family history of AD and Apolipoprotein E (APOE) genotype. Additional analyses were performed after correcting for the effect of age and hypertension.

Results

The studied cohort showed very low WMH burden (median 1.94 cm³) and 20-year dementia risk estimates (median 1.47 %). Even so, higher CAIDE scores were significantly associated with increased global WMH load. The main drivers of this association were age and hypertension, with hypercholesterolemia and body mass index also displaying a minor, albeit significant, influence. Regionally, CAIDE scores were positively associated with WMH in anterior areas, mostly in the frontal lobe. Age and hypertension showed significant association with WMH in almost all regions analyzed. The APOE-ε2 allele showed a protective effect over global WMH with a pattern that comprised juxtacortical temporo-occipital and fronto-parietal deep white matter regions. Participants with maternal family history of AD had higher WMH load than those without, especially in temporal and occipital lobes.

Conclusions

WMH load is associated with AD risk factors even in cognitively unimpaired subjects with very low WMH burden and dementia risk estimates. Our results suggest that tight control of modifiable risk factors in middle-age/late middle-age could have a significant impact on late-life dementia.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0460-1) contains supplementary material, which is available to authorized users.

Incidental findings on brain MRI among Chinese at the age of 55-65 years: the Taizhou Imaging Study

Asymptomatic brain abnormalities are common incidental findings on brain MRI in the elderly population and can be regarded as imaging markers of early stroke and dementia. We initiated the Taizhou Imaging Study (TIS) to examine the prevalence and correlates of incidental findings using brain MRI among an elderly population residing in a rural area of China. A total of 562 individuals, at the age of 55 to 65 years, participated in the TIS study with a response rate of 90%. The prevalence of lacunes, white matter hyperintensity (WMH), cerebral microbleeds (CMB), perivascular space, and intracranial arterial stenosis was 26.69%, 10.68%, 18.51%, 27.76%, and 12.81%, respectively. Age and hypertension were the major correlates of these incidental findings. Per each year increase in age, the risks of WMH and CMB increased by 15% and 14%. Compared to individuals with normal blood pressure, individuals with hypertension had an increased risk of all incidental findings, with the adjusted odds ratios of 2.28 to 5.45. Correlations of age, gender and body mass index with brain gray matter fraction were also observed. The high prevalence of these findings indicates a need of preventative strategy to help prevent future stroke and dementia in this population.

Prospective memory impairment in patients with white matter lesions

OBJECTIVE

A vast majority of the episodic memory literature in white matter lesions (WML) had focused on "retrospective memory (RM)", little was known about prospective memory (PM) in WML patients. The aim of our study was to investigate the effect of WML patients on event-based prospective memory (EBPM) and time-based prospective memory (TBPM). In addition, our study attempted to understand the possible mechanisms of PM damage in WML patients.

METHODS

A total of 42 WML patients and 40 age and education level matched healthy controls were included. EBPM (an action whenever particular words were presented) and TBPM (an action at certain times) were performed to test the involvement of PM in WML. The extent of WML within cholinergic pathways were assessed using the cholinergic pathways hyperintensities scale (CHIPS).

RESULTS

A significant difference was found in the performance of Montreal Cognitive Assessment (MOCA) (21.8 ± 3.9 vs. 26.6 ± 1.7, p < 0.05) and TBPM (2.88 ± 1.21 vs. 4.27 ± 0.78, p < 0.05), but not Mini-Mental State Examination (MMSE) (26.9 ± 2.8 vs. 27.3 ± 1.2, p > 0.05) and EBPM (3.62 ± 1.25 vs.4.47 ± 1.11, p > 0.05) in WML patients compared with the healthy controls. Moreover, TBPM and MOCA scores were negatively correlated with CHIPS scores.

CONCLUSIONS

WML patients were impaired in TBPM but not in EBPM, supporting that EBPM and TBPM have different neural mechanisms. Our results demonstrated that WML are involved in the TBPM probably by affecting the central cholinergic pathway.

Cognitive Profiles and Atrophy Ratings on MRI in Senior Patients With Mild Cognitive Impairment

In this cross-sectional study, we sought to describe cognitive and neuroimaging profiles of Memory clinic patients with Mild Cognitive Impairment (MCI). 51 MCI patients and 51 controls, matched on age, sex, and socio-economic status (SES), were assessed with an extensive neuropsychological test battery that included a measure of intelligence (General Ability Index, "GAI," from WAIS-IV), and structural magnetic resonance imaging (MRI). MCI subtypes were determined after inclusion, and z-scores normalized to our control group were generated for each cognitive domain in each MCI participant. MR-images were scored by visual rating scales. MCI patients performed significantly worse than controls on 23 of 31 cognitive measures (Bonferroni corrected p = 0.001), and on 8 of 31 measures after covarying for intelligence (GAI). Compared to nonamnestic MCI patients, amnestic MCI patients had lower test results in 13 of 31 measures, and 5 of 31 measures after co-varying for GAI. Compared to controls, the MCI patients had greater atrophy on Schelten's Medial temporal lobe atrophy score (MTA), especially in those with amnestic MCI. The only structure-function correlation that remained significant after correction for multiple comparisons was the MTA-long delay recall domain. Intelligence operationalized as GAI appears to be an important moderator of the neuropsychological outcomes. Atrophy of the medial temporal lobe, based on MTA scores, may be a sensitive biomarker for the functional episodic memory deficits associated with MCI.

Cerebral small vessel disease and the risk of Alzheimer's disease: A systematic review

BACKGROUND

Cerebral small vessel disease (CSVD) comprises a variety of disorders affecting small arteries and microvessels of the brain, manifesting as white matter hyperintensities (WMHs), cerebral microbleeds (CMBs), and deep brain infarcts. In addition to its contribution to vascular dementia (VaD), it has also been suggested to contribute to the pathogenesis of Alzheimer's disease (AD).

METHOD

A systematic review of the literature available on Medline, Embase and Pubmed was undertaken, whereby CSVD was divided into WMHs, CMBs and deep brain infarcts. Biomarkers of AD pathology in the cerebrospinal fluid or plasma, or positron emission tomographic imaging for amyloid and/or tau deposition were used for AD pathology.

RESULTS

A total of 4117 articles were identified and 41 articles met criteria for inclusion. These consisted of 17 articles on vascular risk factors for clinical AD, 21 articles on Aβ pathology and 15 articles on tau pathology, permitting ten meta-analyses. CMBs or lobar CMBs were associated with pooled relative risk (RR) of AD at 1.546, (95%CI 0.842-2.838, z = 1.41 p = 0.160) and 1.526(95%CI 0.760-3.063, z = 1.19, p = 0.235) respectively, both non-significant. Microinfarcts were associated with significantly increased AD risk, with pooled odds ratio OR at 1.203(95%CI 1.014-1.428, 2.12 p = 0.034). Aβ pathology was significantly associated with WMHs in AD patients but not in normal age-matched controls. The pooled β (linear regression) for total WMHs with CSF Aβ42 in AD patients was -0.19(95%CI -0.26-0.11, z = 4.83 p = 0.000) and the pooled r (correlation coefficient) for WMHs and PiB in the normal population was -0.10 (95%CI -0.11-0.30, 0.93 p = 0.351). CMBs were significantly associated with Aβ pathology in AD patients. The pooled standardized mean difference (SMD) was -0.453, 95%CI -0.697- -0.208, z = 3.63 p = 0.000. There was no significant relationship between the incidence of lacunes and levels of CSFAβ, with a pooled β of 0.057 (95%CI -0.050-0.163, z = 1.05 p = 0.295). No significant relationship was found between CMBs and the levels of CSFt-tau/CSFp-tau in AD patients (-0.014, 95%CI -0.556-0.529, z = 0.05 p = 0.960; -0.058, 95%CI -0.630-0.515, z = 0.20 p = 0.844) and cortical CMBs and CSF p-tau in the normal population (0.000, 95%CI -0.706-0.706, z = 0.00 p = 0.999).

CONCLUSIONS

Some CSVD markers were significantly associated with clinical AD pathology and may be associated with Aβ/tau pathology. WMHs and microinfarcts were associated with increased risk of AD. It remains unclear whether they precede or follow AD pathology.

Pharmacological and Non-pharmacological Therapies of Cognitive Impairment in Multiple Sclerosis

Background

Cognitive impairment is one of the most important clinical features of neurodegenerative disorders including multiple sclerosis (MS). Conducted research shows that up to 65 percent of MS patients have cognitive deficits such as episodic memory, sustained attention, reduced verbal fluency; however, the cognitive MS domain is information processing speed. It is the first syndrome of cognitive dysfunction and the most widely affected in MS. Occasionally these impairments occur even before the appearance of physical symptoms.

Methods

Therefore, this review focused on the current status of our knowledge about possible methods of treatment cognitive impairment in MS patients including novel strategies. Research and online content was performed using Medline and EMBASE databases.

Results

The most recent research suggests that cognitive impairment is correlated with brain lesion volume and brain atrophy. The examination of the cognitive impairment is usually based on particular neuropsychological batteries. However, it can be not enough to make a precise diagnosis. This creates a demand to find markers that might be useful for identifying patients with risk of cognitive impairment at an early stage of the disease. Currently the most promising methods consist of neuroimaging indicators, such as diffusion tensor imaging, the magnetization transfer ratio, and N-acetyl aspartate levels. Diagnosis problems are strictly connected with treatment procedures. There are two main cognitive therapies: pharmacological (disease modifying drugs (DMD), symptomatic treatments) and non-pharmacological interventions that are focused on psychological and physical rehabilitation. Some trials have shown a positive association between physical activity and the cognitive function.

Conclusion

This article is an overview of the current state of knowledge related to cognition impairment treatment in MS. Additionally, novel strategies for cognitive impairments such as cryostimulation and other complementary methods are presented.

Cerebral Microbleeds in Advanced Dementia: Clinical and Pathological Correlates

OBJECTIVE

We conducted a longitudinal study to explore the clinical and pathological correlates of cerebral microbleeds (CMBs) in institutionalized patients with dementia.

METHODS

Clinical and magnetic resonance imaging (MRI) data were extracted from 182 nursing home patients (mean age [standard deviation]: 81.3 [6.9], 78.0% female, and 83.4% moderate to severe dementia), which were divided according to the CMBs number and location. One-year follow-up data were obtained from 153 patients, and postmortem pathological diagnosis was available in 40 patients.

RESULTS

Cerebral microbleeds were observed in 42.9% of patients and were associated with MRI ischemic lesions ( P < .0005). In the adjusted analysis, lobar CMB predicted worsening of parkinsonism (standardized β: 0.43) and gait (standardized β: 0.24). A pathological diagnosis of Alzheimer's disease was less frequent in the brains of patients with lobar and deep CMB (33.3% vs 85.3%; P < .05).

CONCLUSION

Cerebral microbleeds were linked to cerebrovascular disease and predicted motor deterioration in institutionalized people with advanced dementia.

White matter lesions: Spatial heterogeneity, links to risk factors, cognition, genetics, and atrophy

OBJECTIVES

To investigate spatial heterogeneity of white matter lesions or hyperintensities (WMH).

METHODS

MRI scans of 1,836 participants (median age 52.2 ± 13.16 years) encompassing a wide age range (22-84 years) from the cross-sectional Study of Health in Pomerania (Germany) were included as discovery set identifying spatially distinct components of WMH using a structural covariance approach. Scans of 307 participants (median age 73.8 ± 10.2 years, with 747 observations) from the Baltimore Longitudinal Study of Aging (United States) were included to examine differences in longitudinal progression of these components. The associations of these components with vascular risk factors, cortical atrophy, Alzheimer disease (AD) genetics, and cognition were then investigated using linear regression.

RESULTS

WMH were found to occur nonuniformly, with higher frequency within spatially heterogeneous patterns encoded by 4 components, which were consistent with common categorizations of deep and periventricular WMH, while further dividing the latter into posterior, frontal, and dorsal components. Temporal trends of the components differed both cross-sectionally and longitudinally. Frontal periventricular WMH were most distinctive as they appeared in the fifth decade of life, whereas the other components appeared later in life during the sixth decade. Furthermore, frontal WMH were associated with systolic blood pressure and with pronounced atrophy including AD-related regions. AD polygenic risk score was associated with the dorsal periventricular component in the elderly. Cognitive decline was associated with the dorsal component.

CONCLUSIONS

These results support the hypothesis that the appearance of WMH follows age and disease-dependent regional distribution patterns, potentially influenced by differential underlying pathophysiologic mechanisms, and possibly with a differential link to vascular and neurodegenerative changes.

Neuropsychiatric symptoms of cholinergic deficiency occur with degradation of the projections from the nucleus basalis of Meynert

This study aims to evaluate the relation between a cluster of neuropsychiatric symptoms related to cholinergic deficiency and degradation of the cortical cholinergic projections which project from the nucleus basalis of Meynert to the cerebral cortex. An atlas of the pathway from the nucleus basalis to the cortex (NbM cortical pathway) was constructed using diffusion tensor imaging and tractography in 87 memory clinic patients. Structural degradation was considered to be represented by lower fractional anisotropy (FA) and higher mean diffusivity (MD). Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory. A predefined cluster including agitation, anxiety, apathy, delusions, hallucinations, and irritability was labeled as the cholinergic deficiency syndrome (CDS). In regression analyses, lower FA and higher MD in the NbM cortical pathway were associated with CDS symptoms but not with other neuropsychiatric symptoms. These associations were independent of cerebral atrophy and overall FA or MD. There was no association between interruption of the NbM cortical pathway by white matter hyperintensities and CDS symptoms. Cox regression suggested a trend for higher mortality with lower FA in the NbM cortical pathway may exist. These findings provide anatomical support for the hypothesis that degradation of the cholinergic projections from the nucleus basalis of Meynert may lead to a distinct clinical syndrome. Future studies could use our results to test the utility of assessing NbM projection integrity to identify patients who may benefit from cholinergic treatment or with a worse prognosis.

A population neuroscience approach to the study of cerebral small vessel disease in midlife and late life: an invited review

Aging in later life engenders numerous changes to the cerebral microvasculature. Such changes can remain clinically silent but are associated with greater risk for negative health outcomes over time. Knowledge is limited about the pathogenesis, prevention, and treatment of potentially detrimental changes in the cerebral microvasculature that occur with advancing age. In this review, we summarize literature on aging of the cerebral microvasculature, and we propose a conceptual framework to fill existing research gaps and advance future work on this heterogeneous phenomenon. We propose that the major gaps in this area are attributable to an incomplete characterization of cerebrovascular pathology, the populations being studied, and the temporality of exposure to risk factors. Specifically, currently available measures of age-related cerebral microvasculature changes are indirect, primarily related to parenchymal damage rather than direct quantification of small vessel damage, limiting the understanding of cerebral small vessel disease (cSVD) itself. Moreover, studies seldom account for variability in the health-related conditions or interactions with risk factors, which are likely determinants of cSVD pathogenesis. Finally, study designs are predominantly cross-sectional and/or have relied on single time point measures, leaving no clear evidence of time trajectories of risk factors or of change in cerebral microvasculature. We argue that more resources should be invested in 1) developing methodological approaches and basic science models to better understand the pathogenic and etiological nature of age-related brain microvascular diseases and 2) implementing state-of-the-science population study designs that account for the temporal evolution of cerebral microvascular changes in diverse populations across the lifespan.

Associations of CAIDE Dementia Risk Score with MRI, PIB-PET measures, and cognition

Background:

CAIDE Dementia Risk Score is the first validated tool for estimating dementia risk based on a midlife risk profile.

Objectives:

This observational study investigated longitudinal associations of CAIDE Dementia Risk Score with brain MRI, amyloid burden evaluated with PIB-PET, and detailed cognition measures.

Methods:

FINGER participants were at-risk elderly without dementia. CAIDE Risk Score was calculated using data from previous national surveys (mean age 52.4 years). In connection to baseline FINGER visit (on average 17.6 years later, mean age 70.1 years), 132 participants underwent MRI scans, and 48 underwent PIB-PET scans. All 1,260 participants were cognitively assessed (Neuropsychological Test Battery, NTB). Neuroimaging assessments included brain cortical thickness and volumes (Freesurfer 5.0.3), visually rated medial temporal atrophy (MTA), white matter lesions (WML), and amyloid accumulation.

Results:

Higher CAIDE Dementia Risk Score was related to more pronounced deep WML (OR 1.22, 95% CI 1.05–1.43), lower total gray matter (β-coefficient –0.29, p = 0.001) and hippocampal volume (β-coefficient –0.28, p = 0.003), lower cortical thickness (β-coefficient –0.19, p = 0.042), and poorer cognition (β-coefficients –0.31 for total NTB score, –0.25 for executive functioning, –0.33 for processing speed, and –0.20 for memory, all p < 0.001). Higher CAIDE Dementia Risk Score including APOE genotype was additionally related to more pronounced MTA (OR 1.15, 95% CI 1.00–1.30). No associations were found with periventricular WML or amyloid accumulation.

Conclusions:

The CAIDE Dementia Risk Score was related to indicators of cerebrovascular changes and neurodegeneration on MRI, and cognition. The lack of association with brain amyloid accumulation needs to be verified in studies with larger sample sizes.

The effect of white matter hyperintensities on cognition is mediated by cortical atrophy

White matter hyperintensities (WMH) have been linked to cognitive dysfunction and dementia, although the reasons are unclear. One possibility is that WMH promote neurodegeneration, which, in turn, affects cognition. We examined whether cortical thickness, a marker of neurodegeneration, mediates the relationship between WMH and cognition among 519 older adults. Using conditional process analysis modeling techniques, we examined the association between WMH volume and global cognition and tested whether cortical thickness mediates this relationship statistically. We also tested specific regional hypotheses to determine whether cortical thickness or volume in the medial temporal lobe mediates the relationship between WMH volume and memory. Increased total WMH volume was associated with poorer global cognition and memory. Global cortical thickness and medial temporal lobe thickness/volume mediated the relationship of WMH volume on global cognition and memory functioning. The mediating relationship was similar across racial and ethnic groups and across diagnostic groups (i.e., mild cognitive impairment/Alzheimer's disease). The findings suggest that WMH promote atrophy, which, in turn, drives cognitive decline and highlight a potential pathway in which small vessel cerebrovascular disease affects cognition by promoting neurodegenerative changes directly.

Longitudinal microstructural changes of cerebral white matter and their association with mobility performance in older persons

Mobility impairment in older persons is associated with brain white matter hyperintensities (WMH), a common finding in magnetic resonance images and one established imaging biomarker of small vessel disease. The contribution of possible microstructural abnormalities within normal-appearing white matter (NAWM) to mobility, however, remains unclear. We used diffusion tensor imaging (DTI) measures, i.e. fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), to assess microstructural changes within supratentorial NAWM and WMH sub-compartments, and to investigate their association with changes in mobility performance, i.e. Tinetti assessment and the 2.5-meters walk time test. We analyzed baseline (N = 86, age ≥75 years) and 4-year (N = 41) follow-up data. Results from cross-sectional analysis on baseline data showed significant correlation between WMH volume and NAWM-FA (r = -0.33, p = 0.002), NAWM-AD (r = 0.32, p = 0.003) and NAWM-RD (r = 0.39, p = 0.0002). Our longitudinal analysis showed that after 4-years, FA and AD decreased and RD increased within NAWM. In regional tract-based analysis decrease in NAWM-FA and increase in NAWM-RD within the genu of the corpus callosum correlated with slower walk time independent of age, gender and WMH burden. In conclusion, global DTI indices of microstructural integrity indicate that significant changes occur in the supratentorial NAWM over four years. The observed changes likely reflect white matter deterioration resulting from aging as well as accrual of cerebrovascular injury associated with small vessel disease. The observed association between mobility scores and regional measures of NAWM microstructural integrity within the corpus callosum suggests that subtle changes within this structure may contribute to mobility impairment.

Patterns of progressive atrophy vary with age in Alzheimer's disease patients

Age is not only the greatest risk factor for Alzheimer's disease (AD) but also a key modifier of disease presentation and progression. Here, we investigate how longitudinal atrophy patterns vary with age in mild cognitive impairment (MCI) and AD. Data comprised serial longitudinal 1.5-T magnetic resonance imaging scans from 153 AD, 339 MCI, and 191 control subjects. Voxel-wise maps of longitudinal volume change were obtained and aligned across subjects. Local volume change was then modeled in terms of diagnostic group and an interaction between group and age, adjusted for total intracranial volume, white-matter hyperintensity volume, and apolipoprotein E genotype. Results were significant at p < 0.05 with family-wise error correction for multiple comparisons. An age-by-group interaction revealed that younger AD patients had significantly faster atrophy rates in the bilateral precuneus, parietal, and superior temporal lobes. These results suggest younger AD patients have predominantly posterior progressive atrophy, unexplained by white-matter hyperintensity, apolipoprotein E, or total intracranial volume. Clinical trials may benefit from adapting outcome measures for patient groups with lower average ages, to capture progressive atrophy in posterior cortices.

Bullseye's representation of cerebral white matter hyperintensities

BACKGROUND AND PURPOSE

Visual rating scales have limited capacities to depict the regional distribution of cerebral white matter hyperintensities (WMH). We present a regional-zonal volumetric analysis alongside a visualization tool to compare and deconstruct visual rating scales.

MATERIALS AND METHODS

3D T1-weighted, T2-weighted spin-echo and FLAIR images were acquired on a 3T system, from 82 elderly participants in a population-based study. Images were automatically segmented for WMH. Lobar boundaries and distance to ventricular surface were used to define white matter regions. Regional-zonal WMH loads were displayed using bullseye plots. Four raters assessed all images applying three scales. Correlations between visual scales and regional WMH as well as inter and intra-rater variability were assessed. A multinomial ordinal regression model was used to predict scores based on regional volumes and global WMH burdens.

RESULTS

On average, the bullseye plot depicted a right-left symmetry in the distribution and concentration of damage in the periventricular zone, especially in frontal regions. WMH loads correlated well with the average visual rating scores (e.g. Kendall's tau [Volume, Scheltens]=0.59 CI=[0.53 0.62]). Local correlations allowed comparison of loading patterns between scales and between raters. Regional measurements had more predictive power than global WMH burden (e.g. frontal caps prediction with local features: ICC=0.67 CI=[0.53 0.77], global volume=0.50 CI=[0.32 0.65], intra-rater=0.44 CI=[0.23 0.60]).

CONCLUSION

Regional-zonal representation of WMH burden highlights similarities and differences between visual rating scales and raters. The bullseye infographic tool provides a simple visual representation of regional lesion load that can be used for rater calibration and training.

Higher prevalence of cerebral white matter hyperintensities in homozygous APOE-ɛ4 allele carriers aged 45-75: Results from the ALFA study

Cerebral white matter hyperintensities are believed the consequence of small vessel disease and are associated with risk and progression of Alzheimer's disease. The ɛ4 allele of the APOE gene is the major factor accountable for Alzheimer's disease heritability. However, the relationship between white matter hyperintensities and APOE genotype in healthy subjects remains controversial. We investigated the association between APOE-ɛ4 and vascular risk factors with white matter hyperintensities, and explored their interactions, in a cohort of cognitively healthy adults (45-75 years). White matter hyperintensities were assessed with the Fazekas Scale from magnetic resonance images (575 participants: 74 APOE-ɛ4 homozygotes, 220 heterozygotes and 281 noncarriers) and classified into normal (Fazekas < 2) and pathological (≥2). Stepwise logistic regression was used to study the association between pathological Fazekas and APOE genotype after correcting for cardiovascular and sociodemographic factors. APOE-ɛ4 homozygotes, but not heterozygotes, bear a significantly higher risk (OR 3.432; 95% CI [1.297-9.082]; p = 0.013) of displaying pathological white matter hyperintensities. As expected, aging, hypertension and cardiovascular and dementia risk scales were also positively associated to pathological white matter hyperintensities, but these did not modulate the effect of APOE-ɛ4/ɛ4. In subjects at genetic risk of developing Alzheimer's disease, the control of modifiable risk factors of white matter hyperintensities is of particular relevance to reduce or delay dementia's onset.

White matter hyperintensity shape and location feature analysis on brain MRI; proof of principle study in patients with diabetes

Cerebral small vessel disease is a heterogeneous disease in which various underlying etiologies can lead to different types of white matter hyperintensities (WMH). WMH shape features might aid in distinguishing these different types. In this proof of principle study in patients with type 2 diabetes mellitus (T2DM), we present a novel approach to assess WMH using shape features. Our algorithm determines WMH volume and different WMH shape and location features on 3T MRI scans. These features were compared between patients with T2DM (n = 60) and a matched control group (n = 54). Although a more traditional marker (WMH volume) was not significantly different between groups (natural log transformed Beta (95% CI): 0.07 (-0.11↔0.24)), patients with T2DM showed a larger number of non-punctuate WMH (median (10^th-90^th percentile), patients: 40 lesions per person (16-86); controls: 26 (5-58)) and a different shape (eccentricity) of punctuate deep WMH (Beta (95% CI): 0.40 (0.23↔0.58)) compared to controls. In conclusion, our algorithm identified WMH features that are not part of traditional WMH assessment, but showed to be distinguishing features between patients with T2DM and controls. Future studies could address these features to further unravel the etiology and functional impact of WMH.

Structural Connectivity Alterations Along the Alzheimer's Disease Continuum: Reproducibility Across Two Independent Samples and Correlation with Cerebrospinal Fluid Amyloid-β and Tau

BACKGROUND

Gray matter changes associated with the progression of Alzheimer's disease (AD) have been thoroughly studied. However, alterations in white matter tracts have received less attention, particularly during early or preclinical stages of the disease.

OBJECTIVE

To identify the structural connectivity changes across the AD continuum.

METHODS

We performed probabilistic tractography in a total of 183 subjects on two independent samples that include control (n = 68) and preclinical AD individuals (n = 28), patients diagnosed with mild cognitive impairment (MCI) due to AD (n = 44), and AD patients (n = 43). We compared the connectivity between groups, and with CSF Aβ42 and tau biomarkers.

RESULTS

We observed disconnections in preclinical individuals, mainly located in the temporal lobe. This pattern of disconnection spread to the parietal and frontal lobes at the MCI stage and involved almost all the brain in AD. These findings were not driven by gray matter atrophy.

DISCUSSION

Using tractography, we were able to identify white matter changes between subsequent disease stages and, notably, also in preclinical AD. Therefore, this method may be useful for detecting early and specific brain structural changes during preclinical AD stage.

Relationship between the severity of cerebral white matter hyperintensities and sympathetic nervous activity in older adults

AIM

White matter hyperintensities (WMH), visualized on brain magnetic resonance imaging, represent an abnormality related to the development of geriatric syndromes. Recently, it has been found that low sympathetic nervous activity might be associated with physical and cognitive dysfunction in older adults. Therefore, we investigated the relationship between the severity of cerebral WMH and sympathetic nervous activity, measured by the heart rate variability.

METHODS

We carried out a cross-sectional study of 39 older patients. Holter recording was carried out for 30 min. From the RR intervals on the electrocardiogram, the standard deviation of the normal-to-normal intervals, the standard deviation of all normal-to-normal intervals in all the five segments of the entire recording, low frequency (LF), high frequency (HF) and LF/HF were calculated. In regard to the WMH, periventricular hyperintensities and deep white matter hyperintensities (DWMH) were rated according to the Fazekas classification. The WMH were also rated semiquantitatively according to the methods developed by Junque (periventricular hyperintensities) and de Groot (DWMH).

RESULTS

The LF/HF showed significant negative correlations with the total and regional periventricular hyperintensities, as well as DWMH. Multiple regression analysis showed that the negative associations remained significant between the LF/HF and DWMH (total, temporal, occipital). Furthermore, fall risk index significantly correlated with the LF/HF, total and the occipital DWMH.

CONCLUSIONS

The severity of the DWMH was associated with the LF/HF and the fall risk, one of the important geriatric syndromes, suggesting that WMH, sympathetic nervous dysfunction and geriatric syndrome are interrelated to each other. Geriatr Gerontol Int 2018; 18: 569-575.

Association between hemostatic markers, serum lipid fractions and progression of cerebral small vessel disease: A 2-year follow-up study

INTRODUCTION

Little is known if hemostatic markers and serum lipid fractions can predict further radiological progression beyond vascular risk factors in cerebral small vessel disease (SVD). We investigated whether they are associated with SVD radiological progression and if they are related to different SVD clinical manifestations.

METHODS

A single-center, prospective, cohort study with 2 years of radiological follow-up was performed in consecutive patients with different SVD manifestations. The study group consisted of 123 patients: 49 with lacunar stroke (LS), 48 with vascular dementia (VaD) and 26 with vascular parkinsonism (VaP). We assessed SVD progression by a visual SVD scale. We determined the relationship between serum or plasma concentrations of tissue factor (TF), thrombomodulin, beta-thromboglobulin (BTG), fibrinogen, D-dimer and total cholesterol, HDL-C, LDL-C, triglycerides and SVD progression by logistic regression analysis.

RESULTS

34.9% patients had SVD radiological progression: 43% had isolated WMLs progression, 23.2% had new lacunes, 34.8% had both WMLs progression and new lacunes. Fibrinogen [OR 1.02 (95% CI 1.006-1.011] was significantly associated with risk of new lacunes or WMLs progression regardless of the clinical SVD manifestation. While low HDL [OR 0.96 (0.93-1)] and TF [OR 1.07 (0.99-1.1)] were marginally associated with new lacunes, BTG [OR 1.005 (0.99-1.01)] was associated with WMLs progression.

CONCLUSION

We found a relationship between fibrinogen and risk of radiological progression of SVD regardless of the clinical SVD manifestation. In addition, lower HDL and increased TF predicted development of new lacunes, and higher BTG was associated with risk of WMLs progression.

Recent Advances in Leukoaraiosis: White Matter Structural Integrity and Functional Outcomes after Acute Ischemic Stroke

Leukoaraiosis, a radiographic marker of cerebral small vessel disease detected on T2-weighted brain magnetic resonance imaging (MRI) as white matter hyperintensity (WMH), is a key contributor to the risk and severity of acute cerebral ischemia. Prior investigations have emphasized the pathophysiology of WMH development and progression; however, more recently, an association between WMH burden and functional outcomes after stroke has emerged. There is growing evidence that WMH represents macroscopic injury to the white matter and that the extent of WMH burden on MRI influences functional recovery in multiple domains following acute ischemic stroke (AIS). In this review, we discuss the current understanding of WMH pathogenesis and its impact on AIS and functional recovery.

The role of exercise in mitigating subcortical ischemic vascular cognitive impairment

Subcortical ischemic vascular cognitive impairment (SIVCI) is the most preventable form of cognitive dysfunction. There is converging evidence from animal and human studies that indicate vascular injury as the primary cause of SIVCI. Currently, there are no curative pharmaceutical treatments for vascular dementia; however, exercise may be a promising strategy to combat SIVCI. This review will focus on the role of exercise as a strategy to prevent or slow the progression of SIVCI, with particular emphasis on the mechanisms by which exercise may improve cerebrovascular function. We propose that exercise may be an effective strategy to combat SIVCI by improving cognitive function, increasing the bioavailability of neurotrophins, stimulating endothelial function, and controlling vascular risk factors. This article is part of the Special Issue "Vascular Dementia".

The effect of white matter hyperintensities on statistical analysis of diffusion tensor imaging in cognitively healthy elderly and prodromal Alzheimer's disease

Diffusion tensor imaging (DTI) has been used to study microstructural white matter alterations in a variety of conditions including normal aging and Alzheimer's disease (AD). White matter hyperintensities (WMH) are common in cognitively healthy elderly as well as in AD and exhibit elevated mean diffusivity (MD) and reduced fractional anisotropy (FA). However, the effect of WMH on statistical analysis of DTI estimates has not been thoroughly studied. In the present study we address this in two ways. First, we investigate the effect of WMH on MD and FA in the dorsal and ventral cingulum, the superior longitudinal fasciculus, and the corticospinal tract, by comparing two matched groups of cognitively healthy elderly (n = 21 + 21) with unequal WMH load. Second, we assess the effects of adjusting for WMH load when comparing MD and FA in prodromal AD subjects (n = 83) to cognitively healthy elderly (n = 132) in the abovementioned white matter tracts. Results showed the WMH in cognitively healthy elderly to have a generally large effect on DTI estimates (Cohen’s d = 0.63 to 1.27 for significant differences in MD and −1.06 to −0.69 for FA). These effect sizes were comparable to those of various neurological and psychiatric diseases (Cohen’s d = 0.57 to 2.20 for differences in MD and −1.76 to −0.61 for FA). Adjusting for WMH when comparing DTI estimates in prodromal AD subjects to cognitively healthy elderly improved the explanatory power as well as the outcome of the analysis, indicating that some of the differences in MD and FA were largely driven by unequal WMH load between the groups rather than alterations in normal-appearing white matter (NAWM). Thus, our findings suggest that if the purpose of a study is to compare alterations in NAWM between two groups using DTI it may be necessary to adjust the statistical analysis for WMH.

White Matter Diseases with Radiologic-Pathologic Correlation

White matter diseases include a wide spectrum of disorders that have in common impairment of normal myelination, either by secondary destruction of previously myelinated structures (demyelinating processes) or by primary abnormalities of myelin formation (dysmyelinating processes). The pathogenesis of many white matter diseases remains poorly understood. Demyelinating disorders are the object of this review and will be further divided into autoimmune, infectious, vascular, and toxic-metabolic processes. Autoimmune processes include multiple sclerosis and related diseases: tumefactive demyelinating lesions, Balo concentric sclerosis, Marburg and Schilder variants, neuromyelitis optica (Devic disease), acute disseminated encephalomyelitis, and acute hemorrhagic leukoencephalopathy (Hurst disease). Infectious processes include Lyme disease (neuroborreliosis), progressive multifocal leukoencephalopathy, and human immunodeficiency virus (HIV) encephalopathy. Vascular processes include different types of small-vessel disease: arteriolosclerosis, cerebral amyloid angiopathy, cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), primary angiitis of the central nervous system, Susac syndrome, and neurolupus. Toxic-metabolic processes include osmotic myelinolysis, methotrexate leukoencephalopathy, and posterior reversible encephalopathy syndrome. The imaging spectrum can vary widely from small multifocal white matter lesions to confluent or extensive white matter involvement. Understanding the pathologic substrate is fundamental for understanding the radiologic manifestations, and a systematic approach to the radiologic findings, in correlation with clinical and laboratory data, is crucial for narrowing the differential diagnosis. (©)RSNA, 2016.

Prediction of Cognitive Decline from White Matter Hyperintensity and Single-Photon Emission Computed Tomography in Alzheimer's Disease

BACKGROUND

While several studies support an association of white matter hyperintensity (WMH) volume and regional cerebral blood flow (rCBF) with cognitive decline in Alzheimer's disease (AD), no reports have simultaneously considered the effects of both factors on cognitive decline.

OBJECTIVE

The purpose of the present study was to compare WMH volume and rCBF in relation to cognitive function by developing a new software program to fuse magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) data.

METHOD

We used MRI, SPECT, and neuropsychological data from 182 serial outpatients treated at the memory clinic of our hospital.

RESULTS

Twenty-nine AD patients fulfilled the inclusion criteria (18 females, mean age: 73.1 ± 7.9 years, mean Mini-Mental State Examination: 23.1 ± 3.0). Analysis of variance revealed that posterior deep WMH (DWMH) volume was significantly larger than both anterior periventricular hyperintensity (PVH) and DWMH, and posterior PVH volumes. Multivariate regression analysis showed that increased volumes of the anterior PVH and the posterior DWMH and decreased rCBF of the parietal cortex negatively affected cognitive function. The other areas had no significant negative effects on cognitive function.

CONCLUSION

Our findings show that the volume of the posterior WMH was significantly larger than that of other areas, and the increased posterior WMH volume and decreased rCBF of the parietal cortex negatively affected cognitive function. Therefore, the posterior WMH volume and the parietal rCBF are key parameters of cognitive decline in AD patients.

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.

Lesion location and cognitive impact of cerebral small vessel disease

Cerebral small vessel disease (SVD) is an important cause of cognitive impairment. Important MRI manifestations of SVD include white matter hyperintensities (WMH) and lacunes. This narrative review addresses the role of anatomical lesion location in the impact of SVD on cognition, integrating findings from early autopsy studies with emerging findings from recent studies with advanced image analysis techniques. Early autopsy and imaging studies of small case series indicate that single lacunar infarcts in, for example the thalamus, caudate nucleus or internal capsule can cause marked cognitive impairment. However, the findings of such case studies may not be generalizable. Emerging location-based image analysis approaches are now being applied to large cohorts. Recent studies show that WMH burden in strategic white matter tracts, such as the forceps minor or anterior thalamic radiation (ATR), is more relevant in explaining variance in cognitive functioning than global WMH volume. These findings suggest that the future diagnostic work-up of memory clinic patients could potentially be improved by shifting from a global assessment of WMH and lacune burden towards a quantitative assessment of lesion volumes within strategic brain regions. In this review, a summary of currently known strategic regions for SVD-related cognitive impairment is provided, highlighting recent technical developments in SVD research. The potential and challenges of location-based approaches for diagnostic purposes in clinical practice are discussed, along with their potential prognostic and therapeutic applications.

Endothelial cell-oligodendrocyte interactions in small vessel disease and aging

Cerebral small vessel disease (SVD) is a prevalent, neurological disease that significantly increases the risk of stroke and dementia. The main pathological changes are vascular, in the form of lipohyalinosis and arteriosclerosis, and in the white matter (WM), in the form of WM lesions. Despite this, it is unclear to what extent the key cell types involved–the endothelial cells (ECs) of the vasculature and the oligodendrocytes of the WM–interact. Here, we describe the work that has so far been carried out suggesting an interaction between ECs and oligodendrocytes in SVD. As these interactions have been studied in more detail in other disease states and in development, we explore these systems and discuss the role these mechanisms may play in SVD.

Subclinical white matter lesions and medial temporal lobe atrophy are associated with EEG slowing in a memory clinic cohort

OBJECTIVE

The aim of the study was to describe the relationship between electroencephalographic (EEG) findings obtained by standardized visual analysis, subclinical white matter lesions (WML) and brain atrophy in a large memory clinic population.

METHODS

Patients with Alzheimer's disease (AD, n=58), mild cognitive impairment (MCI, n=141), subjective cognitive impairment (SCI, n=194) had clinical, MRI based WML severity and regional atrophy assessments, and routine resting EEG recording. Background activity (BA) and episodic and continuous abnormalities were assessed visually in EEG.

RESULTS

WML (p=0.006) and atrophy in medial temporal regions (MTA) (p=<0.001) were associated with slower BA in all diagnoses. WML were associated in SCI with total episodic EEG abnormalities (p=0.03).

CONCLUSIONS

EEG is associated with subclinical WML burden and cortical brain atrophy in a memory clinic population.

SIGNIFICANCE

Even the standard visually assessed EEG can complement a memory clinic diagnostic workup.

The neurology of ageing: what is normal?

Ageing is associated with changes in the nervous system with consequent alterations in some neurological examination findings: understanding what is 'normal' at different ages is essential when evaluating patients. In seminal papers published in 1931, Dr MacDonald Critchley summarised his observations and the prevailing evidence on the effects of ageing on, among others, sensation, reflexes, ocular function, olfaction, movement and cognition. In this review, these observations are re-evaluated in light of contemporary evidence. Factors influencing the measurement and interpretation of these clinical findings are then discussed, including reproducibility, the influence of comorbidities, secular trends, how 'normality' should best be defined, the problems of extrapolating group data to individuals and the influence of presymptomatic neurodegenerative disease states. The case is made that context is critical, and that combining life course data with detailed clinical and biomarker phenotyping is required to understand the determinants of normal neurological function associated with ageing.

Cognitive reserve moderates the relationship between neuropsychological performance and white matter fiber bundle length in healthy older adults

Recent work using novel neuroimaging methods has revealed shorter white matter fiber bundle length (FBL) in older compared to younger adults. Shorter FBL also corresponds to poorer performance on cognitive measures sensitive to advanced age. However, it is unclear if individual factors such as cognitive reserve (CR) effectively moderate the relationship between FBL and cognitive performance. This study examined CR as a potential moderator of cognitive performance and brain integrity as defined by FBL. Sixty-three healthy adults underwent neuropsychological evaluation and 3T brain magnetic resonance imaging. Cognitive performance was measured using the Repeatable Battery of Assessment of Neuropsychological Status (RBANS). FBL was quantified from tractography tracings of white matter fiber bundles, derived from the diffusion tensor imaging. CR was determined by estimated premorbid IQ. Analyses revealed that lower scores on the RBANS were associated with shorter whole brain FBL (p = 0.04) and lower CR (p = 0.01) CR moderated the relationship between whole brain FBL and RBANS score (p < 0.01). Tract-specific analyses revealed that CR also moderated the association between FBL in the hippocampal segment of the cingulum and RBANS performance (p = 0.03). These results demonstrate that lower cognitive performance on the RBANS is more common with low CR and short FBL. On the contrary, when individuals have high CR, the relationship between FBL and cognitive performance is attenuated. Overall, CR protects older adults against lower cognitive performance despite age-associated reductions in FBL.

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Zusammenfassung. Unser Gehirn verändert sich mit zunehmendem Alter. Dieser physiologische Prozess kann mithilfe von Magnetresonanztomografie (MRT) beschrieben werden. Im Laufe des Lebens kommt es zu Atrophie (Schrumpfen von Hirnstrukturen) sowie Auftreten von charakteristischen MRT-Signal-Hyperintensitäten in der weissen Substanz. Eine besonders starke oder frühe Ausprägung dieser Veränderungen kann pathologisch sein. Die Abgrenzung zwischen gesundem Altern und Prozessen mit Krankheitswert ist dabei nicht einfach. In diesem Mini-Review sollen normale Alterungsprozesse des Gehirns beschrieben und krankhafte Veränderungen aufgezeigt werden, die weiterer Abklärung und Behandlung bedürfen.

Pathogenesis of white matter changes in cerebral small vessel diseases: beyond vessel-intrinsic mechanisms

Cerebral small vessel diseases (SVDs) are a leading cause of age and hypertension-related stroke and dementia. The salient features of SVDs visible on conventional brain magnetic resonance images include white matter hyperintensities (WMHs) on T2-weighted images, small infarcts, macrohemorrhages, dilated perivascular spaces, microbleeds and brain atrophy. Among these, WMHs are the most common and often the earliest brain tissue changes. Moreover, over the past two decades, large population- and patient-based studies have established the clinical importance of WMHs, notably with respect to cognitive and motor disturbances. Here, we seek to provide a new and critical look at the pathogenesis of SVD-associated white matter (WM) changes. We first review our current knowledge of WM biology in the healthy brain, and then consider the main clinical and pathological features of WM changes in SVDs. The most widely held view is that SVD-associated WM lesions are caused by chronic hypoperfusion, impaired cerebrovascular reactivity (CVR) or blood–brain barrier (BBB) leakage. Here, we assess the arguments for and against each of these mechanisms based on population, patient and experimental model studies, and further discuss other potential mechanisms. Specifically, building on two recent seminal studies that have uncovered an anatomical and functional relationship between oligodendrocyte progenitor cells and blood vessels, we elaborate on how small vessel changes might compromise myelin remodelling and cause WM degeneration. Finally, we propose new directions for future studies on this hot research topic.

Classification and characterization of periventricular and deep white matter hyperintensities on MRI: A study in older adults

White matter hyperintensities (WMH) are frequently divided into periventricular (PWMH) and deep (DWMH), and the two classes have been associated with different cognitive, microstructural, and clinical correlates. However, although this distinction is widely used in visual ratings scales, how to best anatomically define the two classes is still disputed. In fact, the methods used to define PWMH and DWMH vary significantly between studies, making results difficult to compare. The purpose of this study was twofold: first, to compare four current criteria used to define PWMH and DWMH in a cohort of healthy older adults (mean age: 69.58 ± 5.33 years) by quantifying possible differences in terms of estimated volumes; second, to explore associations between the two WMH sub-classes with cognition, tissue microstructure and cardiovascular risk factors, analysing the impact of different criteria on the specific associations. Our results suggest that the classification criterion used for the definition of PWMH and DWMH should not be considered a major obstacle for the comparison of different studies. We observed that higher PWMH load is associated with reduced cognitive function, higher mean arterial pressure and age. Higher DWMH load is associated with higher body mass index. PWMH have lower fractional anisotropy than DWMH, which also have more heterogeneous microstructure. These findings support the hypothesis that PWMH and DWMH are different entities and that their distinction can provide useful information about healthy and pathological aging processes.

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.

Abnormal cortical functional activity in patients with ischemic white matter lesions: A resting-state functional magnetic resonance imaging study

There is increasing evidence that white matter lesions (WMLs) are associated with cognitive impairments. The purpose of this study was to explore the relationship of WMLs with cognitive impairments from the aspect of cortical functional activity. Briefly, Sixteen patients with ischemic WMLs and 13 controls participated in this study. A regional homogeneity (ReHo) approach was used to investigate altered neural coherence in patients with ischemic WMLs during the resting state. A correlation analysis was further performed between regions with altered ReHo and cognitive test scores, including Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA), in the patient group. Finally, we found regions with altered ReHo values in patients with ischemic WMLs to be involved in default mode network (DMN), frontal-parietal control network (FPCN), dorsal attention network (DAN), motor network and right temporal cortex. Moreover, some altered regions belonging to DMN, FPCN and motor network were significantly correlated with cognitive test scores. Our results provide neuroimaging evidence for the impairments of memory, attention, executive and motor function in patients with ischemic WMLs. It is interesting to note that the decreased ReHo was mainly in the anterior brain regions, while increased ReHo in the posterior brain regions, which may indicate a failure down regulation of spontaneous activity in posterior regions. In summary, this study indicates an important role of specific cortical dysfunction in cognitive associated with WMLs.