Cortical thinning in subcortical vascular dementia with negative 11C-PiB PET

Distinct spatiotemporal patterns of cortical thinning in Alzheimer's disease-type cognitive impairment and subcortical vascular cognitive impairment

Previous studies on Alzheimer's disease-type cognitive impairment (ADCI) and subcortical vascular cognitive impairment (SVCI) has rarely explored spatiotemporal heterogeneity. This study aims to identify distinct spatiotemporal cortical atrophy patterns in ADCI and SVCI. 1,338 participants (713 ADCI, 208 SVCI, and 417 cognitively unimpaired elders) underwent brain magnetic resonance imaging (MRI), amyloid positron emission tomography, and neuropsychological tests. Using MRI, this study measures cortical thickness in five brain regions (medial temporal, inferior temporal, posterior medial parietal, lateral parietal, and frontal areas) and utilizes the Subtype and Stage Inference (SuStaIn) model to predict the most probable subtype and stage for each participant. SuStaIn identifies two distinct cortical thinning patterns in ADCI (medial temporal: 65.8%, diffuse: 34.2%) and SVCI (frontotemporal: 47.1%, parietal: 52.9%) patients. The medial temporal subtype of ADCI shows a faster decline in attention, visuospatial, visual memory, and frontal/executive domains than the diffuse subtype (p-value < 0.01). However, there are no significant differences in longitudinal cognitive outcomes between the two subtypes of SVCI. Our study provides valuable insights into the distinct spatiotemporal patterns of cortical thinning in patients with ADCI and SVCI, suggesting the potential for individualized therapeutic and preventive strategies to improve clinical outcomes.

Association of Glycemic Variability With Imaging Markers of Vascular Burden, β-Amyloid, Brain Atrophy, and Cognitive Impairment

BACKGROUND AND OBJECTIVE

We aimed to investigate the association between glycemic variability (GV) and neuroimaging markers of white matter hyperintensities (WMH), beta-amyloid (Aβ), brain atrophy, and cognitive impairment.

METHODS

This was a retrospective cohort study that included participants without dementia from a memory clinic. They all had Aβ PET, brain MRI, and standardized neuropsychological tests and had fasting glucose (FG) levels tested more than twice during the study period. We defined GV as the intraindividual visit-to-visit variability in FG levels. Multivariable linear regression and logistic regression were used to identify whether GV was associated with the presence of severe WMH and Aβ uptake with DM, mean FG levels, age, sex, hypertension, and presence of APOE4 allele as covariates. Mediation analyses were used to investigate the mediating effect of WMH and Aβ uptake on the relationship between GV and brain atrophy and cognition.

RESULTS

Among the 688 participants, the mean age was 72.2 years, and the proportion of female participants was 51.9%. Increase in GV was predictive of the presence of severe WMH (coefficient [95% CI] 1.032 [1.012-1.054]; p = 0.002) and increased Aβ uptake (1.005 [1.001-1.008]; p = 0.007). Both WMH and increased Aβ uptake partially mediated the relationship between GV and frontal-executive dysfunction (GV → WMH → frontal-executive; direct effect, -0.319 [-0.557 to -0.080]; indirect effect, -0.050 [-0.091 to -0.008]) and memory dysfunction (GV → Aβ → memory; direct effect, -0.182 [-0.338 to -0.026]; indirect effect, -0.067 [-0.119 to -0.015]), respectively. In addition, increased Aβ uptake completely mediated the relationship between GV and hippocampal volume (indirect effect, -1.091 [-2.078 to -0.103]) and partially mediated the relationship between GV and parietal thickness (direct effect, -0.00101 [-0.00185 to -0.00016]; indirect effect, -0.00016 [-0.00032 to -0.000002]).

DISCUSSION

Our findings suggest that increased GV is related to vascular and Alzheimer risk factors and neurodegenerative markers, which in turn leads to subsequent cognitive impairment. Furthermore, GV can be considered a potentially modifiable risk factor for dementia prevention.

Independent and additive contribution of white matter hyperintensities and Alzheimer's disease pathology to basal forebrain cholinergic system degeneration

OBJECTIVES

Degeneration of the cholinergic basal forebrain nuclei (CBFN) system has been studied extensively in Alzheimer's disease (AD). White matter hyperintensities are a hallmark of aging as well as a common co-morbidity of AD, but their contribution to CBFN degeneration has remained unclear. Therefore, we explored the influence of white matter hyperintensities within cholinergic subcortical-cortical projection pathways on CBFN volumes and regional gray matter volumes in AD and age- and gender-matched controls.

METHODS

We analyzed magnetic resonance images (MRI) from 42 patients with AD and 87 age- and gender-matched control subjects. We assessed the white matter hyperintensity burden within the cholinergic projection pathways using the Cholinergic Pathways Hyperintensities Scale (CHIPS), and applied probabilistic anatomical maps for the analysis of CBFN volumes, i.e. the Ch1-3 compartment and the Ch4 cell group (nucleus basalis of Meynert), by diffeomorphic anatomical registration using exponentiated lie algebra analysis of voxel-based morphometry. Using multiple linear regression analyses, we explored correlations between regional gray matter volumes and the extent of white matter hyperintensities or CBFN volumes in both groups.

RESULTS

In AD, all CBFN volumes were significantly smaller than in controls, and white matter hyperintensity burden within the cholinergic projection pathways was not correlated with CBFN volume. In controls, white matter hyperintensity burden within the cholinergic projection pathways was inversely correlated with CBFN volume when corrected for sex and total intracranial volume, but this correlation was no longer significant after correction for age. Voxel-wise multiple linear regression analyses using threshold-free cluster enhancement revealed that in controls, cholinergic pathway hyperintensities correlated with gray matter loss in perisylvian areas, whereas the were no effects in AD. Moreover, we found that CBFN volumes correlated with distinct regional cortical atrophy patterns in both groups.

CONCLUSION

Our results indicate that white matter hyperintensities and AD pathology contribute independently but additively to the degeneration of cholinergic basal forebrain structures. Whereas AD is primarily associated with CBFN volume loss, cholinergic degeneration associated with white matter hyperintensities appears to involve disruption of cholinergic cortical projection fibers with less pronounced effects on CBFN volumes.

Decreased visual acuity is related to thinner cortex in cognitively normal adults: cross-sectional, single-center cohort study

Background

Decreased visual acuity (VA) is reported to be a risk factor for dementia. However, the association between VA and cortical thickness has not been established. We investigated the association between VA and cortical thickness in cognitively normal adults.

Method

We conducted a cross-sectional, single-center cohort study with cognitively normal adults (aged ≥ 45) who received medical screening examinations at the Health Promotion Center at Samsung Medical Center. Subjects were categorized as bad (VA ≤ 20/40), fair (20/40 < VA ≤ 20/25), and good (VA > 20/25) VA group by using corrected VA in the Snellen system. Using 3D volumetric brain MRI, cortical thickness was calculated using the Euclidean distance between the linked vertices of the inner and outer surfaces. We analyzed the association between VA and cortical thickness after controlling for age, sex, hypertension, diabetes, dyslipidemia, intracranial volume, and education level.

Results

A total of 2756 subjects were analyzed in this study. Compared to the good VA group, the bad VA group showed overall thinner cortex (p = 0.015), especially in the parietal (p = 0.018) and occipital (p = 0.011) lobes. Topographical color maps of vertex-wise analysis also showed that the bad VA group showed a thinner cortex in the parieto-temporo-occipital area. These results were more robust in younger adults (aged 45 to 65) as decreased VA was associated with thinner cortex in more widespread regions in the parieto-temporo-occipital area.

Conclusion

Our results suggest that a thinner cortex in the visual processing area of the brain is related to decreased visual stimuli.

Machine Learning for the Prediction of Amyloid Positivity in Amnestic Mild Cognitive Impairment

BACKGROUND

Amyloid-β (Aβ) evaluation in amnestic mild cognitive impairment (aMCI) patients is important for predicting conversion to Alzheimer's disease. However, Aβ evaluation through Aβ positron emission tomography (PET) is limited due to high cost and safety issues.

OBJECTIVE

We therefore aimed to develop and validate prediction models of Aβ positivity for aMCI using optimal interpretable machine learning (ML) approaches utilizing multimodal markers.

METHODS

We recruited 529 aMCI patients from multiple centers who underwent Aβ PET. We trained ML algorithms using a training cohort (324 aMCI from Samsung medical center) with two-phase modelling: model 1 included age, gender, education, diabetes, hypertension, apolipoprotein E genotype, and neuropsychological test scores; model 2 included the same variables as model 1 with additional MRI features. We used four-fold cross-validation during the modelling and evaluated the models on an external validation cohort (187 aMCI from the other centers).

RESULTS

Model 1 showed good accuracy (area under the receiver operating characteristic curve [AUROC] 0.837) in cross-validation, and fair accuracy (AUROC 0.765) in external validation. Model 2 led to improvement in the prediction performance with good accuracy (AUROC 0.892) in cross validation compared to model 1. Apolipoprotein E genotype, delayed recall task scores, and interaction between cortical thickness in the temporal region and hippocampal volume were the most important predictors of Aβ positivity.

CONCLUSION

Our results suggest that ML models are effective in predicting Aβ positivity at the individual level and could help the biomarker-guided diagnosis of prodromal AD.

Harmonisation of PET imaging features with different amyloid ligands using machine learning-based classifier

PURPOSE

In this study, we used machine learning to develop a new method derived from a ligand-independent amyloid (Aβ) positron emission tomography (PET) classifier to harmonise different Aβ ligands.

METHODS

We obtained 107 paired ¹⁸F-florbetaben (FBB) and ¹⁸F-flutemetamol (FMM) PET images at the Samsung Medical Centre. To apply the method to FMM ligand, we transferred the previously developed FBB PET classifier to test similar features from the FMM PET images for application to FMM, which in turn developed a ligand-independent Aβ PET classifier. We explored the concordance rates of our classifier in detecting cortical and striatal Aβ positivity. We investigated the correlation of machine learning-based cortical tracer uptake (ML-CTU) values quantified by the classifier between FBB and FMM.

RESULTS

This classifier achieved high classification accuracy (area under the curve = 0.958) even with different Aβ PET ligands. In addition, the concordance rate of FBB and FMM using the classifier (87.5%) was good to excellent, which seemed to be higher than that in visual assessment (82.7%) and lower than that in standardised uptake value ratio cut-off categorisation (93.3%). FBB and FMM ML-CTU values were highly correlated with each other (R = 0.903).

CONCLUSION

Our findings suggested that our novel classifier may harmonise FBB and FMM ligands in the clinical setting which in turn facilitate the biomarker-guided diagnosis and trials of anti-Aβ treatment in the research field.

Association between cortical thickness and distinct vascular cognitive impairment and dementia in patients with white matter lesions

NEW FINDINGS

What is the central question of this study? White matter lesions (WMLs) are a brain disease characterized by altered brain structural and functional connectivity, but findings have shown an inconsistent pattern: are there distinct cortical thickness changes in patients with WMLs subtypes? What is the main finding and its importance? Patients with WMLs with non-dementia vascular cognitive impairment and WMLs with vascular dementia showed distinct pathophysiology in cortical thickness. These neural correlates of WMLs should be considered in future treatment.

ABSTRACT

The effect of cortical thickness on white matter lesions (WMLs) in patients with distinct vascular cognitive impairments is relatively unknown. This study investigated the correlation between cortical thickness and vascular cognitive manifestations. WML patients and healthy controls from Beijing Tiantan Hospital between 2014 and 2018 were included. The patients were further divided into two subgroups, namely WMLs with non-dementia vascular cognitive impairment (WML-VCIND) and WMLs with vascular dementia (WML-VaD) according to the Clinical Dementia Rating (CDR) scale and the Beijing version of the Montreal Cognitive Assessment (MoCA). Changes in cortical thickness were calculated using FreeSurfer. Pearson's correlation analysis was performed to explore the relationship between cognitive manifestations and cortical thickness in WML patients. Forty-five WML patients and 23 healthy controls were recruited. The WML group exhibited significant difference in cortical thickness compared to the control group. Significantly decreased cortical thickness in the middle and superior frontal gyri, middle temporal gyrus, angular gyrus and insula was found in the WML-VaD versus WML-VCIND subgroup. Cortical thickness deficits of the left caudal middle frontal gyrus (r = 0.451, P = 0.002), left rostral middle frontal gyrus (r = 0.514, P < 0.001), left superior frontal gyrus (r = 0.410, P = 0.006), right middle temporal gyrus (r = 0.440, P = 0.003), right pars triangularis (r = 0.462, P = 0.002), right superior frontal gyrus (r = 0.434, P = 0.004) and right insula (r = 0.499, P = 0.001) were positively correlated with the MoCA score in WML patients. The specific pattern of cortical thickness deficits in the WML-VaD subgroup revealed the pathophysiology of WMLs, which should be considered in future treatment of WMLs.

The Impact of Amyloid-β or Tau on Cognitive Change in the Presence of Severe Cerebrovascular Disease

BACKGROUND

As Alzheimer's disease (AD) and cerebral small vessel disease (CSVD) commonly coexist, the interaction between two has been of the considerable interest.

OBJECTIVE

We determined whether the association of Aβ and tau with cognitive decline differs by the presence of significant CSVD.

METHODS

We included 60 subcortical vascular cognitive impairment (SVCI) from Samsung Medical Center and 82 Alzheimer's disease-related cognitive impairment (ADCI) from ADNI, who underwent Aβ (florbetaben or florbetapir) and tau (flortaucipir, FTP) PET imaging. They were retrospectively assessed for 5.0±3.9 and 5.6±1.9 years with Clinical Dementia Rating-sum of boxes (CDR-SB)/Mini-Mental State Examination (MMSE). Mixed effects models were used to investigate the interaction between Aβ/tau and group on CDR-SB/MMSE changes.

RESULTS

The frequency of Aβ positivity (45% versus 54.9%, p = 0.556) and mean global FTP SUVR (1.17±0.21 versus 1.16±0.17, p = 0.702) were not different between the two groups. We found a significant interaction effect of Aβ positivity and SVCI group on CDR-SB increase/MMSE decrease (p = 0.013/p < 0.001), and a significant interaction effect of global FTP uptake and SVCI group on CDR-SB increase/MMSE decrease (p < 0.001 and p = 0.030). Finally, the interaction effects of regional tau and group were prominent in the Braak III/IV (p = 0.001) and V/VI (p = 0.003) not in Braak I/II region (p = 0.398).

CONCLUSION

The association between Aβ/tau and cognitive decline is stronger in SVCI than in ADCI. Therefore, our findings suggested that Aβ positivity or tau burden (particularly in the Braak III/IV or V/VI regions) and CSVD might synergistically affect cognitive decline.

Neuroimaging in Vascular Cognitive Impairment and Dementia: A Systematic Review

Cerebrovascular diseases are well established causes of cognitive impairment. Different etiologic entities, such as vascular dementia (VaD), vascular cognitive impairment, subcortical (ischemic) VaD, and vascular cognitive disorder, are included in the umbrella definition of vascular cognitive impairment and dementia (VCID). Because of the variability of VCID clinical presentation, there is no agreement on criteria defining the neuropathological threshold of this disorder. In fact, VCID is characterized by cerebral hemodynamic alteration which ranges from decreased cerebral blood flow to small vessels disease and involves a multifactorial process that leads to demyelination and gliosis, including blood-brain barrier disruption, hypoxia, and hypoperfusion, oxidative stress, neuroinflammation and alteration on neurovascular unit coupling, cerebral microbleeds, or superficial siderosis. Numerous criteria for the definition of VaD have been described: the National Institute of Neurological Disorders and Stroke Association Internationale pour Recherche'-et-l'Enseignement en Neurosciences criteria, the State of California Alzheimer's Disease Diagnostic and Treatment Centers criteria, DSM-V criteria, the Diagnostic Criteria for Vascular Cognitive Disorders (a VASCOG Statement), and Vascular Impairment of Cognition Classification Consensus Study. Neuroimaging is fundamental for definition and diagnosis of VCID and should be used to assess the extent, location, and type of vascular lesions. MRI is the most sensible technique, especially if used according to standardized protocols, even if CT plays an important role in several conditions. Functional neuroimaging, in particular functional MRI and PET, may facilitate differential diagnosis among different forms of dementia. This systematic review aims to explore the state of the art and future perspective of non-invasive diagnostics of VCID.

Cortical neuroanatomical changes related to specific neuropsychological deficits in subcortical vascular cognitive impairment

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Poor performances in neuropsychological tests were associated with cortical atrophy.

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Neural substrates in Aβ (−) SVCI differed from those in ADCI.

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Neural substrate of episodic memory was frontal regions in Aβ (−) SVCI.

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Neural substrates of three neuropsychological tests showed laterality.

Objective

Neuropsychological test-specific neural substrates in subcortical vascular cognitive impairment (SVCI) are expected to differ from those in Alzheimer’s disease-related cognitive impairment (ADCI) but the details are unclear. To determine neural substrates related to cerebral small vessel disease, we investigated the correlations between cognitive dysfunctions measured by standardized neuropsychological tests and cortical thickness in a large sample of participants with amyloid negative (Aβ (−)) SVCI.

Methods

One hundred ninety-eight participants with Aβ (−) SVCI were recruited from the memory clinic between November 2007 to August 2018. To acquire neural substrates, we performed linear regression using the scores of each neuropsychological test as a predictor, cortical thickness as an outcome, and age, sex, education years, intracranial volume and white matter hyperintensity (WMH) as confounders.

Results

Poor performances in each neuropsychological test were associated with cortical atrophy in certain brain regions regardless of WMH. Especially, not the medial temporal but the frontal and posterior cingulate regions with cortical atrophy were mainly associated with memory impairment. Poor performance in animal fluency was more likely to be associated with cortical atrophy in the left hemisphere, while poor performance in the visuospatial memory test was more likely to be associated with cortical atrophy in the right hemisphere.

Conclusions

Our findings suggested that cortical atrophy was an important factor of cognitive impairment in Aβ (−) SVCI regardless of WMH. Furthermore, our findings might give clinicians a better understanding of specific neural substrates of neuropsychological deficits in patients with SVCI.

Preventing dementia by preventing stroke: The Berlin Manifesto

The incidence of stroke and dementia are diverging across the world, rising for those in low- and middle-income countries and falling in those in high-income countries. This suggests that whatever factors cause these trends are potentially modifiable. At the population level, neurological disorders as a group account for the largest proportion of disability-adjusted life years globally (10%). Among neurological disorders, stroke (42%) and dementia (10%) dominate. Stroke and dementia confer risks for each other and share some of the same, largely modifiable, risk and protective factors. In principle, 90% of strokes and 35% of dementias have been estimated to be preventable. Because a stroke doubles the chance of developing dementia and stroke is more common than dementia, more than a third of dementias could be prevented by preventing stroke. Developments at the pathological, pathophysiological, and clinical level also point to new directions. Growing understanding of brain pathophysiology has unveiled the reciprocal interaction of cerebrovascular disease and neurodegeneration identifying new therapeutic targets to include protection of the endothelium, the blood-brain barrier, and other components of the neurovascular unit. In addition, targeting amyloid angiopathy aspects of inflammation and genetic manipulation hold new testable promise. In the meantime, accumulating evidence suggests that whole populations experiencing improved education, and lower vascular risk factor profiles (e.g., reduced prevalence of smoking) and vascular disease, including stroke, have better cognitive function and lower dementia rates. At the individual levels, trials have demonstrated that anticoagulation of atrial fibrillation can reduce the risk of dementia by 48% and that systolic blood pressure lower than 140 mmHg may be better for the brain. Based on these considerations, the World Stroke Organization has issued a proclamation, endorsed by all the major international organizations focused on global brain and cardiovascular health, calling for the joint prevention of stroke and dementia. This article summarizes the evidence for translation into action.

Special topic section: linkages among cerebrovascular, cardiovascular, and cognitive disorders: Preventing dementia by preventing stroke: The Berlin Manifesto

The incidence of stroke and dementia are diverging across the world, rising for those in low-and middle-income countries and falling in those in high-income countries. This suggests that whatever factors cause these trends are potentially modifiable. At the population level, neurological disorders as a group account for the largest proportion of disability-adjusted life years globally (10%). Among neurological disorders, stroke (42%) and dementia (10%) dominate. Stroke and dementia confer risks for each other and share some of the same, largely modifiable, risk and protective factors. In principle, 90% of strokes and 35% of dementias have been estimated to be preventable. Because a stroke doubles the chance of developing dementia and stroke is more common than dementia, more than a third of dementias could be prevented by preventing stroke. Developments at the pathological, pathophysiological, and clinical level also point to new directions. Growing understanding of brain pathophysiology has unveiled the reciprocal interaction of cerebrovascular disease and neurodegeneration identifying new therapeutic targets to include protection of the endothelium, the blood-brain barrier, and other components of the neurovascular unit. In addition, targeting amyloid angiopathy aspects of inflammation and genetic manipulation hold new testable promise. In the meantime, accumulating evidence suggests that whole populations experiencing improved education, and lower vascular risk factor profiles (e.g., reduced prevalence of smoking) and vascular disease, including stroke, have better cognitive function and lower dementia rates. At the individual levels, trials have demonstrated that anticoagulation of atrial fibrillation can reduce the risk of dementia by 48% and that systolic blood pressure lower than 140 mmHg may be better for the brain. Based on these considerations, the World Stroke Organization has issued a proclamation, endorsed by all the major international organizations focused on global brain and cardiovascular health, calling for the joint prevention of stroke and dementia. This article summarizes the evidence for translation into action. © 2019 the Alzheimer's Association and the World Stroke Organisation. Published by Elsevier Inc. All rights reserved.

Domain-specific cognitive effects of white matter pathology in old age, mild cognitive impairment and Alzheimer's disease

Concomitant white matter (WM) brain pathology is often present in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Cognitive effects of WM pathology on cognition in normal and pathological aging have been studied, but very little is known about possible group-specific effects in old age, MCI and AD. The purpose of the current study was to examine the relationship between WM pathology and cognitive functioning in four cognitive domains in old age, MCI and AD. The study utilized multi-domain neuropsychological data and visually rated MRI imaging data from a sample of 56 healthy older adults, 40 patients with MCI and 52 patients with AD (n = 148). After controlling for age and education, main effects of frontal WM pathology (especially in the left hemisphere) were found for cognitive performances in two domains, whereas a main effect of parieto-occipital WM pathology was only found for processing speed. In addition, with regard to processing speed, an interaction between group and WM changes was found: Patients with AD that had moderate or severe left frontal WM pathology were considerably slower than patients with AD that had milder cerebrovascular pathology. Frontal WM pathology, especially in the left hemisphere, seems to affect cognitive functions in many domains in all three groups. The results of the study increase our knowledge of cognitive repercussions stemming from frontal and/or parieto-occipital WM pathology in AD. Clinicians should be aware that patients with AD with prominent frontal cerebrovascular pathology can have considerably slowed cognitive processing.

Multimodal imaging analyses in patients with genetic and sporadic forms of small vessel disease

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is thought to be a pure genetic form of subcortical vascular cognitive impairment (SVCI). The aim of this study was to compare white matter integrity and cortical thickness between typical CADASIL, a genetic form, and two sporadic forms of SVCI (with NOTCH3 and without NOTCH3 variants). We enrolled typical CADASIL patients (N = 11) and SVCI patients [with NOTCH3 variants (N = 15), without NOTCH3 variants (N = 101)]. To adjust the age difference, which reflects the known difference in clinical and radiologic courses between typical CADASIL patients and SVCI patients, we constructed a W-score of measurement for diffusion tensor image and cortical thickness. Typical CADASIL patients showed more frequent white matter hyperintensities in the bilateral posterior temporal region compared to SVCI patients (p < 0.001, uncorrected). We found that SVCI patients, regardless of the presence of NOTCH3 variants, showed significantly greater microstructural alterations (W-score, p < 0.05, FWE-corrected) and cortical thinning (W-score, p < 0.05, FDR-corrected) than typical CADASIL patients. In this study, typical CADASIL and SVCI showed distinct anatomic vulnerabilities in the cortical and subcortical structures. However, there was no difference between SVCI with NOTCH3 variants and SVCI without NOTCH3 variants.

The impact of education on cortical thickness in amyloid-negative subcortical vascular dementia: cognitive reserve hypothesis

Background

The protective effect of education has been well established in Alzheimer’s disease, whereas its role in patients with isolated cerebrovascular diseases remains unclear. We examined the correlation of education with cortical thickness and cerebral small vessel disease markers in patients with pure subcortical vascular mild cognitive impairment (svMCI) and patients with pure subcortical vascular dementia (SVaD).

Methods

We analyzed 45 patients with svMCI and 47 patients with SVaD with negative results on Pittsburgh compound B positron emission tomographic imaging who underwent structural brain magnetic resonance imaging. The main outcome was cortical thickness measured using surface-based morphometric analysis. We also assessed the volumes of white matter hyperintensities (WMH) and numbers of lacunes as other outcomes. To investigate the correlation of education with cortical thickness, WMH volume, and number of lacunes, multiple linear regression analyses were performed after controlling for covariates, including Mini Mental State Examination, in the svMCI and SVaD groups.

Results

In the SVaD group, higher education was correlated with more severe cortical thinning in the bilateral dorsolateral frontal, left medial frontal, and parahippocampal areas, whereas there was no correlation of education with cortical thickness in the svMCI group. There was no correlation between education and cerebral small vessel disease, including WMH and lacunes, in both patients with svMCI and patients with SVaD.

Conclusions

Our findings suggest that the compensatory effects of education on cortical thinning apply to patients with SVaD, which might be explained by the cognitive reserve hypothesis.

A panel of clinical and neuropathological features of cerebrovascular disease through the novel neuroimaging methods

The last decade has witnessed substantial progress in acquiring diagnostic biomarkers for the diagnostic workup of cerebrovascular disease (CVD). Advanced neuroimaging methods not only provide a strategic contribution for the differential diagnosis of vascular dementia (VaD) and vascular cognitive impairment (VCI), but also help elucidate the pathophysiological mechanisms ultimately leading to small vessel disease (SVD) throughout its course.

OBJECTIVE

In this review, the novel imaging methods, both structural and metabolic, were summarized and their impact on the diagnostic workup of age-related CVD was analysed. Methods: An electronic search between January 2010 and 2017 was carried out on PubMed/MEDLINE, Institute for Scientific Information Web of Knowledge and EMBASE.

RESULTS

The use of full functional multimodality in simultaneous Magnetic Resonance (MR)/Positron emission tomography (PET) may potentially improve the clinical characterization of VCI-VaD; for structural imaging, MRI at 3.0 T enables higher-resolution scanning with greater imaging matrices, thinner slices and more detail on the anatomical structure of vascular lesions.

CONCLUSION

Although the importance of most of these techniques in the clinical setting has yet to be recognized, there is great expectancy in achieving earlier and more refined therapeutic interventions for the effective management of VCI-VaD.

Impact of multiple pathologies on the threshold for clinically overt dementia

Longitudinal clinical-pathological studies have increasingly recognized the importance of mixed pathologies (the coexistence of one or more neurodegenerative and cerebrovascular disease pathologies) as important factors in the development of Alzheimer's disease (AD) and other forms of dementia. Older persons with AD pathology, often have concomitant cerebrovascular disease pathologies (macroinfarcts, microinfarcts, atherosclerosis, arteriolosclerosis, cerebral amyloid angiopathy) as well as other concomitant neurodegenerative disease pathologies (Lewy bodies, TDP-43, hippocampal sclerosis). These additional pathologies lower the threshold for clinical diagnosis of AD. Many of these findings from pathologic studies, especially for CVD, have been confirmed using sophisticated neuroimaging technologies. In vivo biomarker studies are necessary to provide an understanding of specific pathologic contributions and time course relationships along the spectrum of accumulating pathologies. In this review, we provide a clinical-pathological perspective on the role of multiple brain pathologies in dementia followed by a review of the available clinical and biomarker data on some of the mixed pathologies.

Thinner temporal and parietal cortex is related to incident clinical progression to dementia in patients with subjective cognitive decline

INTRODUCTION

We aimed to investigate if thinner cortex of the Alzheimer's disease (AD)-signature region was related to clinical progression in patients with subjective cognitive decline (SCD).

METHODS

We included 302 SCD patients with clinical follow-up (≥1 year) and three-dimensional T1 magnetic resonance imaging. We estimated AD-signature cortical thickness, consisting of nine frontal, parietal, and temporal gyri and hippocampal volume. We used Cox proportional hazard models (hazard ratios and 95% confidence intervals) to evaluate cortical thickness in relation to clinical progression to mild cognitive impairment (MCI) or dementia.

RESULTS

After a follow-up of the mean (standard deviation) 3 (2) years, 49 patients (16%) showed clinical progression to MCI (n = 32), AD (n = 9), or non-AD dementia (n = 8). Hippocampal volumes, thinner cortex of the AD-signature (hazard ratio [95% confidence interval], 5 [2-17]) and various AD-signature subcomponents were associated with increased risk of clinical progression. Stratified analyses showed that thinner AD-signature cortex was specifically predictive for clinical progression to dementia but not to MCI.

DISCUSSION

In SCD patients, thinner regional cortex is associated with clinical progression to dementia.

Diffuse reduction of cerebral grey matter volumes in Erdheim-Chester disease

Background

Erdheim-Chester disease (ECD) is a rare non-Langerhans histiocytosis characterized by systemic inflammation and granulomatous infiltration of multiple organs including the central nervous system (CNS), bones, and retroperitoneum. CNS infiltration occurs in one third of patients, but cognitive changes are common in patients without CNS disease. Here we investigate whether there is a neuroanatomic basis to observed cognitive deficits, even in absence of CNS disease.

Methods

We present a volumetric analysis of eleven ECD patients without CNS tumors or prior neurotoxic treatments.

Results

Compared to age-matched controls, ECD patients have diffuse, bihemispheric reduction in cortical thickness and subcortical gray matter.

Conclusions

These findings provide the first corroborating evidence for neurologic disease in ECD patients without direct CNS infiltration.

Novel imaging techniques in cerebral small vessel diseases and vascular cognitive impairment

Dementia is a global growing concern, affecting over 35 million people with a global economic impact of over $604 billion US. With an ageing population the number of people affected is expected double over the next two decades. Vascular cognitive impairment can be caused by various types of cerebrovascular disease, including cortical and subcortical infarcts, and the more diffuse white matter injury due to cerebral small vessel disease. Although this type of cognitive impairment is usually considered the second most common form of dementia after Alzheimer's disease, there is increasing recognition of the vascular contribution to neurodegeneration, with both pathologies frequently coexisting. The aim of this review is to highlight the recent advances in the understanding of vascular cognitive impairment, with a focus on small vessel diseases of the brain. We discuss recently identified small vessel imaging markers that have been associated with cognitive impairment, namely cerebral microbleeds, enlarged perivascular spaces, cortical superficial siderosis, and microinfarcts. We will also consider quantitative techniques including diffusion tensor imaging, magnetic resonance perfusion imaging with arterial spin labelling, functional magnetic resonance imaging and positron emission tomography. As well as potentially shedding light on the mechanism by which cerebral small vessel diseases cause dementia, these novel imaging biomarkers are also of increasing relevance given their ability to guide diagnosis and reflect disease progression, which may in the future be useful for therapeutic interventions. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

The neural correlates of motor intentional disorders in patients with subcortical vascular cognitive impairment

Subcortical vascular cognitive impairment (SVCI) refers to cognitive impairment associated with small vessel disease. Motor intentional disorders (MID) have been reported in patients with SVCI. However, there are no studies exploring the neuroanatomical regions related to MID in SVCI patients. The aim of this study, therefore, was to investigate the neural correlates of MID in SVCI patients. Thirty-one patients with SVCI as well as 10 healthy match control participants were included. A "Pinch-Grip" apparatus was used to quantify the force control capabilities of the index finger in four different movement phases including initiation, development, maintenance, and termination. All participants underwent magnetic resonance imaging (MRI). Topographical cortical areas and white matter tracts correlated with the performances of the four different movement phases were assessed by the surface-based morphometry and tract-based spatial statistics analyses. Poorer performance in the maintenance task was related to cortical thinning in bilateral dorsolateral prefrontal, orbitofrontal and parietal cortices, while poorer performance in the termination task was associated with the disruption of fronto-parietal cortical areas as well as the white matter tracts including splenium and association fibers such as superior longitudinal fasciculus. Our study demonstrates that cortical areas and underlying white matter tracts associated with fronto-parietal attentional system play an important role in motor impersistence and perseveration in SVCI patients.

White matter microstructural changes in pure Alzheimer's disease and subcortical vascular dementia

BACKGROUND AND PURPOSE

Recent studies have demonstrated that Alzheimer's disease (AD) and subcortical vascular dementia (SVaD) have white matter (WM) microstructural changes. However, previous studies on AD and SVaD rarely eliminated the confounding effects of patients with mixed Alzheimer's and cerebrovascular disease pathologies. Therefore, our aim was to evaluate the divergent topography of WM microstructural changes in patients with pure AD and SVaD.

METHODS

Patients who were clinically diagnosed with AD and SVaD were prospectively recruited. Forty AD patients who were Pittsburgh compound B (PiB) positive [PiB(+) AD] without WM hyperintensities and 32 SVaD patients who were PiB negative [PiB(-) SVaD] were chosen. Fifty-six cognitively normal individuals were also recruited (NC). Tract-based spatial statistics of diffuse tensor imaging were used to compare patterns of fractional anisotropy (FA) and mean diffusivity (MD).

RESULTS

Compared with the NC group, the PiB(+) AD group showed decreased FA in the bilateral frontal, temporal and parietal WM regions and the genu and splenium of the corpus callosum as well as increased MD in the left frontal and temporal WM region. PiB(-) SVaD patients showed decreased FA and increased MD in all WM regions. Direct comparison between PiB(+) AD and PiB(-) SVaD groups showed that the PiB(-) SVaD group had decreased FA across all WM regions and increased MD in all WM regions except occipital regions.

CONCLUSION

Our findings suggest that pure AD and pure SVaD have divergent topography of WM microstructural changes including normal appearing WM.

Analysis of Cerebral Blood Flow with Single Photon Emission Computed Tomography in Mild Subcortical Ischemic Vascular Dementia

PURPOSE

The mechanism of cognitive dysfunction of subcortical ischemic vascular dementia (SIVaD) is not yet fully understood. The objective of this study was to investigate and compare the distribution of regional cerebral perfusion (CP) change in the mild forms of SIVaD, a relatively homogeneous subtype of vascular dementia, using statistical parametric mapping (SPM) analysis of the technetium-99m hexamethylproplyeneamineoxime (Tc-99m HMPAO) single photon emission computed tomography (SPECT).

MATERIALS AND METHODS

A total of 28 patients with mild SIVaD and 33 healthy controls were prospectively recruited and underwent SPECT imaging studies between January 2012 and May 2013. SPECT was performed to measure the regional CP, and SPM was applied to the analysis of the SPECT data.

RESULTS

The regional CP was significantly decreased in the bilateral insula, anterior and posterior cingulated gyrus, precentral gyrus, and subcallosal gyrus as well as the right inferior parietal lobule in the SIVaD patients compared to the controls (corrected p = 0.01). The pattern of CP abnormality correlated well with those previously reported in later forms of SIVaD.

CONCLUSIONS

Reduction of CP in the brain areas mentioned was present earlier on in the natural course of SIVaD pathophysiology. Our study suggests that cognitive dysfunction of SIVaD may be related to these regional CP deficits.

Vascular risk and Aβ interact to reduce cortical thickness in AD vulnerable brain regions

OBJECTIVE

The objective of this study was to define whether vascular risk factors interact with β-amyloid (Aβ) in producing changes in brain structure that could underlie the increased risk of Alzheimer disease (AD).

METHODS

Sixty-six cognitively normal and mildly impaired older individuals with a wide range of vascular risk factors were included in this study. The presence of Aβ was assessed using [(11)C]Pittsburgh compound B-PET imaging, and cortical thickness was measured using 3-tesla MRI. Vascular risk was measured with the Framingham Coronary Risk Profile Index.

RESULTS

Individuals with high levels of vascular risk factors have thinner frontotemporal cortex independent of Aβ. These frontotemporal regions are also affected in individuals with Aβ deposition, but the latter show additional thinning in parietal cortices. Aβ and vascular risk were found to interact in posterior (especially in parietal) brain regions, where Aβ has its greatest effect. In this way, the negative effect of Aβ in posterior regions is increased by the presence of vascular risk.

CONCLUSION

Aβ and vascular risk interact to enhance cortical thinning in posterior brain regions that are particularly vulnerable to AD. These findings give insight concerning the mechanisms whereby vascular risk increases the likelihood of developing AD and supports the therapeutic intervention of controlling vascular risk for the prevention of AD.

The pattern of brain gray matter impairments in patients with subcortical vascular dementia

Though subcortical ischemic vascular dementia (SIVD) is known to initially affect subcortical regions, numerous brain imaging studies have also documented the widespread cortical alternations. Here we collected brain structural magnetic resonance imaging data from 34 SIVD patients and 35 healthy controls. Voxel-based morphometry (VBM), cortical thickness (and surface area) analysis and deep gray matter volume measurements were performed. VBM analysis showed gray matter volume reduction in lateral and medial temporal lobes, as well as orbitofrontal cortex in SIVD patients. The surface-based analyses revealed more subtle structural differences in the perisylvian area, medial temporal lobe, anterior and posterior cingulate, as well as prefrontal areas. Furthermore, analyses of deep gray matter demonstrated significant atrophy of the hippocampus, amygdala, nucleus accumbens and other nuclei. Finally, we found that thinning in the hippocampus and anterior cingulate cortex, as well as the volume decline in thalamus, caudate nucleus and amygdala was correlated with the cognitive impairment in patients. In conclusion, our study showed the structural abnormalities of the hippocampus and its associated outflow areas, as well as cortices implicated in cholinergic circuits in SIVD. These findings may bring new insights into the dysfunction of brain gray matter in SIVD.

Cortical thickness and hippocampal shape in pure vascular mild cognitive impairment and dementia of subcortical type

BACKGROUND AND PURPOSE

The progression pattern of brain structural changes in patients with isolated cerebrovascular disease (CVD) remains unclear. To investigate the role of isolated CVD in cognitive impairment patients, patterns of cortical thinning and hippocampal atrophy in pure subcortical vascular mild cognitive impairment (svMCI) and pure subcortical vascular dementia (SVaD) patients were characterized.

METHODS

Forty-five patients with svMCI and 46 patients with SVaD who were negative on Pittsburgh compound B (PiB) positron emission tomography imaging and 75 individuals with normal cognition (NC) were recruited.

RESULTS

Compared with NC, patients with PiB(-) svMCI exhibited frontal, language and retrieval type memory dysfunctions, which in patients with PiB(-) SVaD were further impaired and accompanied by visuospatial and recognition memory dysfunctions. Compared with NC, patients with PiB(-) svMCI exhibited cortical thinning in the frontal, perisylvian, basal temporal and posterior cingulate regions. This atrophy was more prominent and extended further toward the lateral parietal and medial temporal regions in patients with PiB(-) SVaD. Compared with NC subjects, patients with PiB(-) svMCI exhibited hippocampal shape deformities in the lateral body, whilst patients with PiB(-) SVaD exhibited additional deformities within the lateral head and inferior body.

CONCLUSIONS

Our findings suggest that patients with CVD in the absence of Alzheimer's disease pathology can be demented, showing cognitive impairment in multiple domains, which is consistent with the topography of cortical thinning and hippocampal shape deformity.

Abnormalities of cortical thickness, subcortical shapes, and white matter integrity in subcortical vascular cognitive impairment

Subcortical vascular cognitive impairment (sVCI) is caused by lacunar infarcts or extensive and/or diffuse lesions in the white matter that may disrupt the white matter circuitry connecting cortical and subcortical regions and result in the degeneration of neurons in these regions. This study used structural magnetic resonance imaging (MRI) and high angular resolution diffusion imaging (HARDI) techniques to examine cortical thickness, subcortical shapes, and white matter integrity in mild vascular cognitive impairment no dementia (VCIND Mild) and moderate-to-severe VCI (MSVCI). Our study found that compared to controls (n = 25), VCIND Mild (n = 25), and MSVCI (n = 30) showed thinner cortex predominantly in the frontal cortex. The cortex in MSVCI was thinner in the parietal and lateral temporal cortices than that in VCIND Mild. Moreover, compared to controls, VCIND Mild and MSVCI showed smaller shapes (i.e., volume reduction) in the thalamus, putamen, and globus pallidus and ventricular enlargement. Finally, compared to controls, VCIND Mild, and MSVCI showed an increased mean diffusivity in the white matter, while decreased generalized fractional anisotropy was only found in the MSVCI subjects. The major axonal bundles involved in the white matter abnormalities were mainly toward the frontal regions, including the internal capsule/corona radiata, uncinate fasciculus, and anterior section of the inferior fronto-occipital fasciculus, and were anatomically connected to the affected cortical and subcortical structures. Our findings suggest that abnormalities in cortical, subcortical, and white matter morphology in sVCI occur in anatomically connected structures, and that abnormalities progress along a similar trajectory from the mild to moderate and severe conditions.