AT(N) biomarker profiles and Alzheimer's disease symptomology in Down syndrome.

INTRODUCTION: Down syndrome (DS) is a genetic cause of early-onset Alzheimer's disease (AD). The National Institute on Aging-Alzheimer's Association AT(N) Research Framework is a staging model for AD biomarkers but has not been assessed in DS. METHOD: Data are from the Alzheimer's Biomarker Consortium-Down Syndrome. Positron emission tomography (PET) amyloid beta (Aß; 15 mCi of [11 C]Pittsburgh compound B) and tau (10 mCi of [18 F]AV-1451) were used to classify amyloid (A) -/+ and tau (T) +/-. Hippocampal volume classified neurodegeneration (N) -/+. The modified Cued Recall Test assessed episodic memory. RESULTS: Analyses included 162 adults with DS (aged M = 38.84 years, standard deviation = 8.41). Overall, 69.8% of participants were classified as A-/T-/(N)-, 11.1% were A+/T-/(N)-, 5.6% were A+/T+/(N)-, and 9.3% were A+/T+/(N)+. Participants deemed cognitively stable were most likely to be A-T-(N)- and A+T-(N)-. Tau PET (T+) most closely aligning with memory impairment and AD clinical status. DISCUSSION: Findings add to understanding of AT(N) biomarker profiles in DS. HIGHLIGHTS: Overall, 69.8% of adults with Down syndrome (DS) aged 25 to 61 years were classified as amyloid (A)-/tau (T)-/neurodegeneration (N)-, 11.1% were A+/T-/(N)-, 5.6% were A+/T+/(N)-, and 9.3% were A+/T+/(N)+. The AT(N) profiles were associated with clinical Alzheimer's disease (AD) status and with memory performance, with the presence of T+ aligned with AD clinical symptomology. Findings inform models for predicting the transition to the prodromal stage of AD in DS.

Presenilin-1 mutation position influences amyloidosis, small vessel disease, and dementia with disease stage.

INTRODUCTION: Amyloidosis, including cerebral amyloid angiopathy, and markers of small vessel disease (SVD) vary across dominantly inherited Alzheimer's disease (DIAD) presenilin-1 (PSEN1) mutation carriers. We investigated how mutation position relative to codon 200 (pre-/postcodon 200) influences these pathologic features and dementia at different stages. METHODS: Individuals from families with known PSEN1 mutations (n = 393) underwent neuroimaging and clinical assessments. We cross-sectionally evaluated regional Pittsburgh compound B-positron emission tomography uptake, magnetic resonance imaging markers of SVD (diffusion tensor imaging-based white matter injury, white matter hyperintensity volumes, and microhemorrhages), and cognition. RESULTS: Postcodon 200 carriers had lower amyloid burden in all regions but worse markers of SVD and worse Clinical Dementia Rating® scores compared to precodon 200 carriers as a function of estimated years to symptom onset. Markers of SVD partially mediated the mutation position effects on clinical measures. DISCUSSION: We demonstrated the genotypic variability behind spatiotemporal amyloidosis, SVD, and clinical presentation in DIAD, which may inform patient prognosis and clinical trials. HIGHLIGHTS: Mutation position influences Aß burden, SVD, and dementia. PSEN1 pre-200 group had stronger associations between Aß burden and disease stage. PSEN1 post-200 group had stronger associations between SVD markers and disease stage. PSEN1 post-200 group had worse dementia score than pre-200 in late disease stage. Diffusion tensor imaging-based SVD markers mediated mutation position effects on dementia in the late stage.

Amyloid-Related Imaging Abnormalities in the DIAN-TU-001 Trial of Gantenerumab and Solanezumab: Lessons from a Trial in Dominantly Inherited Alzheimer Disease.

OBJECTIVE: To determine the characteristics of participants with amyloid-related imaging abnormalities (ARIA) in a trial of gantenerumab or solanezumab in dominantly inherited Alzheimer disease (DIAD). METHODS: 142 DIAD mutation carriers received either gantenerumab SC (n = 52), solanezumab IV (n = 50), or placebo (n = 40). Participants underwent assessments with the Clinical Dementia Rating® (CDR®), neuropsychological testing, CSF biomarkers, ß-amyloid positron emission tomography (PET), and magnetic resonance imaging (MRI) to monitor ARIA. Cross-sectional and longitudinal analyses evaluated potential ARIA-related risk factors. RESULTS: Eleven participants developed ARIA-E, including 3 with mild symptoms. No ARIA-E was reported under solanezumab while gantenerumab was associated with ARIA-E compared to placebo (odds ratio [OR] = 9.1, confidence interval [CI][1.2, 412.3]; p = 0.021). Under gantenerumab, APOE-ɛ4 carriers were more likely to develop ARIA-E (OR = 5.0, CI[1.0, 30.4]; p = 0.055), as were individuals with microhemorrhage at baseline (OR = 13.7, CI[1.2, 163.2]; p = 0.039). No ARIA-E was observed at the initial 225 mg/month gantenerumab dose, and most cases were observed at doses >675 mg. At first ARIA-E occurrence, all ARIA-E participants were amyloid-PET+, 60% were CDR >0, 60% were past their estimated year to symptom onset, and 60% had also incident ARIA-H. Most ARIA-E radiologically resolved after dose adjustment and developing ARIA-E did not significantly increase odds of trial discontinuation. ARIA-E was more frequently observed in the occipital lobe (90%). ARIA-E severity was associated with age at time of ARIA-E. INTERPRETATION: In DIAD, solanezumab was not associated with ARIA. Gantenerumab dose over 225 mg increased ARIA-E risk, with additional risk for individuals APOE-ɛ4(+) or with microhemorrhage. ARIA-E was reversible on MRI in most cases, generally asymptomatic, without additional risk for trial discontinuation. ANN NEUROL 2022;92:729-744.

Cerebral Microbleeds: Relationship to Antithrombotic Medications.

Background and Purpose: Cerebral microbleeds (CMBs) are represented by small areas of hemosiderin deposition, detected on brain magnetic resonance imaging (MRI), and found in ≈23% of the cognitively normal population over age of 60 years. CMBs predict risk of hemorrhagic and ischemic stroke. They correlate with increased cardiovascular mortality. In this article, we sought to determine in a population-based study whether antithrombotic medications correlate with CMBs and, if present, whether the association was direct or mediated by another variable. Methods: The study consisted of 1253 participants from the population-based Mayo Clinic Study of Aging who underwent T2* gradient-recalled echo magnetic resonance imaging. We tested the relationship between antithrombotic medications and CMB presence and location, using multivariable logistic-regression models. Ordinal logistic models tested the relationship between antithrombotics and CMB frequency. Using structural equation models, we assessed the effect of antithrombotic medications on presence/absence of CMBs and count of CMBs in the CMB-positive group, after considering the effects of age, sex, vascular risk factors, amyloid load by positron emission tomography, and apoE. Results: Two hundred ninety-five participants (26.3%) had CMBs. Among 678 participants taking only antiplatelet medications, 185 (27.3%) had CMBs. Among 95 participants taking only an anticoagulant, 43 (45.3%) had CMBs. Among 44 participants taking an anticoagulant and antiplatelet therapy, 21 (48.8%) had CMBs. Anticoagulants correlated with the presence and frequency of CMBs, whereas antiplatelet agents were not. Structural equation models showed that predictors for presence/absence of CMBs included older age at magnetic resonance imaging, male sex, and anticoagulant use. Predictors of CMB count in the CMB-positive group were male sex and amyloid load. Conclusions: Anticoagulant use correlated with presence of CMBs in the general population. Amyloid positron emission tomography correlated with the count of CMBs in the CMB-positive group.

Cardiometabolic Health and Longitudinal Progression of White Matter Hyperintensity: The Mayo Clinic Study of Aging.

Background and Purpose- White matter hyperintensity (WMH) burden is associated with stroke and cognitive decline. Risk factors associated with the longitudinal progression of WMH in the general population have not been systematically investigated. To investigate the primary midlife and current cardiometabolic risk factors associated with changes in WMH over time in a population cohort. Methods- This cohort study included participants enrolled in the Mayo Clinic Study of Aging, a longitudinal population-based study in Olmsted County, Minnesota with at least 2 consecutive WMH assessments on fluid-attenuated inversion recovery-magnetic resonance images (n=554, ≥60 years with midlife assessments) with relevant baseline laboratory measures of interest. Linear mixed model regression was used to determine the important components of cardiometabolic risk profile at baseline that were associated with future progression of WMH. These analyses were controlled for age and sex. Sensitivity analyses were conducted using stratification by sex. The main outcome measure was percent change in WMH normalized to total intracranial volume. Three sets of models were constructed to evaluate individual (1) midlife risk factors, (2) current risk factors including the presence of metabolic syndrome and its constituents, and (3) baseline measurements of continuous laboratory measures of cardiometabolic risk. Results- Age was the strongest predictor of progression in WMH (P<0.001). Baseline hypertension (P<0.001), midlife hypertension (P=0.003), and baseline fasting glucose in males (P=0.01) were predictive of WMH change. The presence of metabolic syndrome was not associated with progressive WMH. In sensitivity analyses, associations between hypertension and WMH progression were stronger in females. Baseline serum glucose was associated with increase in WMH but was not significant in females in the stratified analysis. Other continuous laboratory measures of vascular risk were not associated with progressive WMH. Conclusions- Midlife and current hypertension in all participants and fasting glucose in males were associated with quantitative changes in white matter. Prospective clinical studies should determine optimal blood pressure to reduce stroke and cognitive impairment during aging.

Reference standard space hippocampus labels according to the European Alzheimer's Disease Consortium-Alzheimer's Disease Neuroimaging Initiative harmonized protocol: Utility in automated volumetry.

INTRODUCTION: A harmonized protocol (HarP) for manual hippocampal segmentation on magnetic resonance imaging (MRI) has recently been developed by an international European Alzheimer's Disease Consortium-Alzheimer's Disease Neuroimaging Initiative project. We aimed at providing consensual certified HarP hippocampal labels in Montreal Neurological Institute (MNI) standard space to serve as reference in automated image analyses. METHODS: Manual HarP tracings on the high-resolution MNI152 standard space template of four expert certified HarP tracers were combined to obtain consensual bilateral hippocampus labels. Utility and validity of these reference labels is demonstrated in a simple atlas-based morphometry approach for automated calculation of HarP-compliant hippocampal volumes within SPM software. RESULTS: Individual tracings showed very high agreement among the four expert tracers (pairwise Jaccard indices 0.82-0.87). Automatically calculated hippocampal volumes were highly correlated (rL/R = 0.89/0.91) with gold standard volumes in the HarP benchmark data set (N = 135 MRIs), with a mean volume difference of 9% (standard deviation 7%). CONCLUSION: The consensual HarP hippocampus labels in the MNI152 template can serve as a reference standard for automated image analyses involving MNI standard space normalization.

Harmonized benchmark labels of the hippocampus on magnetic resonance: the EADC-ADNI project.

BACKGROUND: A globally harmonized protocol (HarP) for manual hippocampal segmentation based on magnetic resonance has been recently developed by a task force from European Alzheimer's Disease Consortium (EADC) and Alzheimer's Disease Neuroimaging Initiative (ADNI). Our aim was to produce benchmark labels based on the HarP for manual segmentation. METHODS: Five experts of manual hippocampal segmentation underwent specific training on the HarP and segmented 40 right and left hippocampi from 10 ADNI subjects on both 1.5 T and 3 T scans. An independent expert visually checked segmentations for compliance with the HarP. Descriptive measures of agreement between tracers were intraclass correlation coefficients (ICCs) of crude volumes and similarity coefficients of three-dimensional volumes. RESULTS: Two hundred labels have been provided for the 20 magnetic resonance images. Intra- and interrater ICCs were >0.94, and mean similarity coefficients were 1.5 T, 0.73 (95% confidence interval [CI], 0.71-0.75); 3 T, 0.75 (95% CI, 0.74-0.76). CONCLUSION: Certified benchmark labels have been produced based on the HarP to be used for tracers' training and qualification.

The EADC-ADNI Harmonized Protocol for manual hippocampal segmentation on magnetic resonance: evidence of validity.

BACKGROUND: An international Delphi panel has defined a harmonized protocol (HarP) for the manual segmentation of the hippocampus on MR. The aim of this study is to study the concurrent validity of the HarP toward local protocols, and its major sources of variance. METHODS: Fourteen tracers segmented 10 Alzheimer's Disease Neuroimaging Initiative (ADNI) cases scanned at 1.5 T and 3T following local protocols, qualified for segmentation based on the HarP through a standard web-platform and resegmented following the HarP. The five most accurate tracers followed the HarP to segment 15 ADNI cases acquired at three time points on both 1.5 T and 3T. RESULTS: The agreement among tracers was relatively low with the local protocols (absolute left/right ICC 0.44/0.43) and much higher with the HarP (absolute left/right ICC 0.88/0.89). On the larger set of 15 cases, the HarP agreement within (left/right ICC range: 0.94/0.95 to 0.99/0.99) and among tracers (left/right ICC range: 0.89/0.90) was very high. The volume variance due to different tracers was 0.9% of the total, comparing favorably to variance due to scanner manufacturer (1.2), atrophy rates (3.5), hemispheric asymmetry (3.7), field strength (4.4), and significantly smaller than the variance due to atrophy (33.5%, P < .001), and physiological variability (49.2%, P < .001). CONCLUSIONS: The HarP has high measurement stability compared with local segmentation protocols, and good reproducibility within and among human tracers. Hippocampi segmented with the HarP can be used as a reference for the qualification of human tracers and automated segmentation algorithms.

Can white matter hyperintensities based Fazekas visual assessment scales inform about Alzheimer's disease pathology in the population?

Background: White matter hyperintensities (WMH) are considered hallmark features of cerebral small vessel disease and have recently been linked to Alzheimer's disease pathology. Their distinct spatial distributions, namely periventricular versus deep WMH, may differ by underlying age-related and pathobiological processes contributing to cognitive decline. We aimed to identify the spatial patterns of WMH using the 4-scale Fazekas visual assessment and explore their differential association with age, vascular health, Alzheimer's imaging markers, namely amyloid and tau burden, and cognition. Because our study consisted of scans from GE and Siemens scanners with different resolutions, we also investigated inter-scanner reproducibility and combinability of WMH measurements on imaging. Methods: We identified 1144 participants from the Mayo Clinic Study of Aging consisting of older adults from Olmsted County, Minnesota with available structural magnetic resonance imaging (MRI), amyloid, and tau positron emission tomography (PET). WMH distribution patterns were assessed on FLAIR-MRI, both 2D axial and 3D, using Fazekas ratings of periventricular and deep WMH severity. We compared the association of periventricular and deep WMH scales with vascular risk factors, amyloid-PET and tau-PET standardized uptake value ratio, WMH volume, and cognition using Pearson partial correlation after adjusting for age. We also evaluated vendor compatibility and reproducibility of the Fazekas scales using intraclass correlations (ICC). Results: Periventricular and deep WMH measurements showed similar correlations with age, cardiometabolic conditions score (vascular risk), and cognition, (p < 0.001). Both periventricular WMH and deep WMH showed weak associations with amyloidosis (R = 0.07, p = < 0.001), and none with tau burden. We found substantial agreement between data from the two scanners for Fazekas measurements (ICC = 0.78). The automated WMH volume had high discriminating power for identifying participants with Fazekas ≥ 2 (area under curve = 0.97). Conclusion: Our study investigates risk factors underlying WMH spatial patterns and their impact on global cognition, with no discernible differences between periventricular and deep WMH. We observed minimal impact of amyloidosis on WMH severity. These findings, coupled with enhanced inter-scanner reproducibility of WMH data, suggest the combinability of inter-scanner data assessed by harmonized protocols in the context of vascular contributions to cognitive impairment and dementia biomarker research.

Can white matter hyperintensities based Fazekas visual assessment scales inform about Alzheimer's disease pathology in the population?

BACKGROUND: White matter hyperintensities (WMH) are considered hallmark features of cerebral small vessel disease and have recently been linked to Alzheimer's disease (AD) pathology. Their distinct spatial distributions, namely periventricular versus deep WMH, may differ by underlying age-related and pathobiological processes contributing to cognitive decline. We aimed to identify the spatial patterns of WMH using the 4-scale Fazekas visual assessment and explore their differential association with age, vascular health, AD imaging markers, namely amyloid and tau burden, and cognition. Because our study consisted of scans from GE and Siemens scanners with different resolutions, we also investigated inter-scanner reproducibility and combinability of WMH measurements on imaging. METHODS: We identified 1144 participants from the Mayo Clinic Study of Aging consisting of a population-based sample from Olmsted County, Minnesota with available structural magnetic resonance imaging (MRI), amyloid, and tau positron emission tomography (PET). WMH distribution patterns were assessed on FLAIR-MRI, both 2D axial and 3D, using Fazekas ratings of periventricular and deep WMH severity. We compared the association of periventricular and deep WMH scales with vascular risk factors, amyloid-PET, and tau-PET standardized uptake value ratio, automated WMH volume, and cognition using Pearson partial correlation after adjusting for age. We also evaluated vendor compatibility and reproducibility of the Fazekas scales using intraclass correlations (ICC). RESULTS: Periventricular and deep WMH measurements showed similar correlations with age, cardiometabolic conditions score (vascular risk), and cognition, (p < 0.001). Both periventricular WMH and deep WMH showed weak associations with amyloidosis (R = 0.07, p = < 0.001), and none with tau burden. We found substantial agreement between data from the two scanners for Fazekas measurements (ICC = 0.82 and 0.74). The automated WMH volume had high discriminating power for identifying participants with Fazekas ≥ 2 (area under curve = 0.97) and showed poor correlation with amyloid and tau PET markers similar to the visual grading. CONCLUSION: Our study investigated risk factors underlying WMH spatial patterns and their impact on global cognition, with no discernible differences between periventricular and deep WMH. We observed minimal impact of amyloidosis on WMH severity. These findings, coupled with enhanced inter-scanner reproducibility of WMH data, suggest the combinability of inter-scanner data assessed by harmonized protocols in the context of vascular contributions to cognitive impairment and dementia biomarker research.

Association between brain health outcomes and metabolic risk factors in persons with diabetes.

We performed a cross-sectional study to determine associations between cognition and MRI-derived brain outcomes, with obesity, diabetes duration, and metabolic risk factors in 51 Pima American Indians with longstanding type 2 diabetes (T2d) (mean [SD] age: 48.4 [11.3] years, T2d duration: 20.1 [9.1] years). Participants had similar cognition (NIH Toolbox Cognition Battery composite: 45.3 [9.8], p = 0.64, n = 51) compared to normative data. T2d duration, but not other metabolic risk factors, associated with decreased cortical thickness (Point Estimate (PE): -0.0061, 95%CI: -0.0113, -0.0009, n = 45), gray matter volume (PE: -830.39, 95%CI: -1503.14, -157.64, n = 45), and increased white matter hyperintensity volume (PE: 0.0389, 95%CI: 0.0049, 0.0729, n = 45).

Etiology of White Matter Hyperintensities in Autosomal Dominant and Sporadic Alzheimer Disease.

Importance: Increased white matter hyperintensity (WMH) volume is a common magnetic resonance imaging (MRI) finding in both autosomal dominant Alzheimer disease (ADAD) and late-onset Alzheimer disease (LOAD), but it remains unclear whether increased WMH along the AD continuum is reflective of AD-intrinsic processes or secondary to elevated systemic vascular risk factors. Objective: To estimate the associations of neurodegeneration and parenchymal and vessel amyloidosis with WMH accumulation and investigate whether systemic vascular risk is associated with WMH beyond these AD-intrinsic processes. Design, Setting, and Participants: This cohort study used data from 3 longitudinal cohort studies conducted in tertiary and community-based medical centers-the Dominantly Inherited Alzheimer Network (DIAN; February 2010 to March 2020), the Alzheimer's Disease Neuroimaging Initiative (ADNI; July 2007 to September 2021), and the Harvard Aging Brain Study (HABS; September 2010 to December 2019). Main Outcome and Measures: The main outcomes were the independent associations of neurodegeneration (decreases in gray matter volume), parenchymal amyloidosis (assessed by amyloid positron emission tomography), and vessel amyloidosis (evidenced by cerebral microbleeds [CMBs]) with cross-sectional and longitudinal WMH. Results: Data from 3960 MRI sessions among 1141 participants were included: 252 pathogenic variant carriers from DIAN (mean [SD] age, 38.4 [11.2] years; 137 [54%] female), 571 older adults from ADNI (mean [SD] age, 72.8 [7.3] years; 274 [48%] female), and 318 older adults from HABS (mean [SD] age, 72.4 [7.6] years; 194 [61%] female). Longitudinal increases in WMH volume were greater in individuals with CMBs compared with those without (DIAN: t = 3.2 [P = .001]; ADNI: t = 2.7 [P = .008]), associated with longitudinal decreases in gray matter volume (DIAN: t = -3.1 [P = .002]; ADNI: t = -5.6 [P < .001]; HABS: t = -2.2 [P = .03]), greater in older individuals (DIAN: t = 6.8 [P < .001]; ADNI: t = 9.1 [P < .001]; HABS: t = 5.4 [P < .001]), and not associated with systemic vascular risk (DIAN: t = 0.7 [P = .40]; ADNI: t = 0.6 [P = .50]; HABS: t = 1.8 [P = .06]) in individuals with ADAD and LOAD after accounting for age, gray matter volume, CMB presence, and amyloid burden. In older adults without CMBs at baseline, greater WMH volume was associated with CMB development during longitudinal follow-up (Cox proportional hazards regression model hazard ratio, 2.63; 95% CI, 1.72-4.03; P < .001). Conclusions and Relevance: The findings suggest that increased WMH volume in AD is associated with neurodegeneration and parenchymal and vessel amyloidosis but not with elevated systemic vascular risk. Additionally, increased WMH volume may represent an early sign of vessel amyloidosis preceding the emergence of CMBs.

Longitudinal Accumulation of Cerebral Microhemorrhages in Dominantly Inherited Alzheimer Disease.

OBJECTIVE: To investigate the inherent clinical risks associated with the presence of cerebral microhemorrhages (CMHs) or cerebral microbleeds and characterize individuals at high risk for developing hemorrhagic amyloid-related imaging abnormality (ARIA-H), we longitudinally evaluated families with dominantly inherited Alzheimer disease (DIAD). METHODS: Mutation carriers (n = 310) and noncarriers (n = 201) underwent neuroimaging, including gradient echo MRI sequences to detect CMHs, and neuropsychological and clinical assessments. Cross-sectional and longitudinal analyses evaluated relationships between CMHs and neuroimaging and clinical markers of disease. RESULTS: Three percent of noncarriers and 8% of carriers developed CMHs primarily located in lobar areas. Carriers with CMHs were older, had higher diastolic blood pressure and Hachinski ischemic scores, and more clinical, cognitive, and motor impairments than those without CMHs. APOE ε4 status was not associated with the prevalence or incidence of CMHs. Prevalent or incident CMHs predicted faster change in Clinical Dementia Rating although not composite cognitive measure, cortical thickness, hippocampal volume, or white matter lesions. Critically, the presence of 2 or more CMHs was associated with a significant risk for development of additional CMHs over time (8.95 ± 10.04 per year). CONCLUSION: Our study highlights factors associated with the development of CMHs in individuals with DIAD. CMHs are a part of the underlying disease process in DIAD and are significantly associated with dementia. This highlights that in participants in treatment trials exposed to drugs, which carry the risk of ARIA-H as a complication, it may be challenging to separate natural incidence of CMHs from drug-related CMHs.

Prevalence and Heterogeneity of Cerebrovascular Disease Imaging Lesions.

OBJECTIVE: To report population age-specific prevalence of core cerebrovascular disease lesions (infarctions, cerebral microbleeds, and white-matter hyperintensities detected with magnetic resonance imaging); estimate cut points for white-matter hyperintensity positivity; investigate sex differences in prevalence; and estimate prevalence of any core cerebrovascular disease features. PATIENTS AND METHODS: Participants in the population-based Mayo Clinic Study of Aging aged 50 to 89 years underwent fluid-attenuated inversion recovery and T2* gradient-recalled echo magnetic resonance imaging to assess cerebrovascular disease between October 10, 2011, and September 29, 2017. We characterized each participant as having infarct, normal versus abnormal white-matter hyperintensity, cerebral microbleed, or a combination of lesions. Prevalence of cerebrovascular disease biomarkers was derived through adjustment for nonparticipation and standardization to the population of Olmsted County, Minnesota. RESULTS: Among 1462 participants without dementia (median [range] age, 68 [50 to 89] y; men, 52.7%), core cerebrovascular disease features increased with age. Prevalence (95% CI) of cerebral microbleeds was 13.6% (11.6%-15.6%); infarcts, 11.7% (9.7%-13.8%); and abnormal white-matter hyperintensity, 10.7% (8.7%-12.6%). Infarcts and cerebral microbleeds were more common among men. In contrast, abnormal white-matter hyperintensity was more common among women ages 60 to 79 y and men, ages 80 y and older. Prevalence of any core cerebrovascular disease feature determined by presence of at least one cerebrovascular disease feature increased from 9.5% (ages 50 to 59 y) to 73.8% (ages 80 to 89 y). CONCLUSION: Whereas this study focused on participants without dementia, the high prevalence of cerebrovascular disease imaging lesions in elderly persons makes assignment of clinical relevance to cognition and other downstream manifestations more probabilistic than deterministic.

Cerebral microbleeds: Prevalence and relationship to amyloid burden.

OBJECTIVE: To describe the prevalence of cerebral microbleeds (CMBs) and determine the association between CMBs and ß-amyloid burden on PET. METHODS: From the population-based Mayo Clinic Study of Aging, 1,215 participants (53% male) underwent 3-tesla MRI scans with T2* gradient recalled echo sequences from October 2011 to February 2017. A total of 1,123 participants (92%) underwent 11C-Pittsburgh compound B (PiB)-PET scans. The prevalence of CMBs was derived by adjusting for nonparticipation and standardizing to the Olmsted County, MN, population. The relationship between ß-amyloid burden and CMB presence and location was tested using logistic regression models. Ordinal logistic models tested the relationship between CMB frequency and ß-amyloid burden. RESULTS: Two hundred seventy-four participants (22.6%) had at least one CMB. CMB frequency increased with age by decade (11% aged 60-69 years, 22% 70-79 years, and 39% 80 years and older). After adjusting for age, sex, and hypertension, PiB standardized uptake value ratio (SUVR) was associated with increased odds of a CMB. The association between PiB SUVR and CMBs was location-specific; PiB SUVR was associated with lobar CMBs but not deep CMBs. Age, hypertension, and PiB SUVR were associated with increasing CMB count. CMB density was greatest in parietal and occipital regions; ß-amyloid burden correlated with concentration of CMBs in all lobar regions. Among participants with multiple CMBs, greater PiB uptake occurred in the pre- and postcentral gyri superiorly, the superior parietal lobe and precuneus, the angular gyrus, inferior temporal gyrus, and temporal poles. CONCLUSIONS: The prevalence of CMBs increases with age. In this population-based sample, ß-amyloid load was associated with lobar but not with deep CMBs.

Sex differences in cerebrovascular pathologies on FLAIR in cognitively unimpaired elderly.

OBJECTIVE: To examine sex differences in cerebrovascular pathologies (CVPs) as seen on fluid-attenuated inversion recovery (FLAIR) MRI and in cardiovascular and metabolic risk factors in a population-based cognitively unimpaired cohort and to examine whether sex is independently associated with FLAIR findings after accounting for differences in important midlife risk factors. METHODS: We identified 1,301 cognitively normal participants (663 men and 638 women) enrolled in the Mayo Clinic Study of Aging (age ≥70 years) who had FLAIR MRI and ascertained total burden of white matter (WM) hyperintensities (WMH), subcortical infarctions, and cortical infarctions. We compared CVPs and midlife and late-life vascular risk factors between men and women. We fit regression models with each CVP as an outcome, treating age, sex, and midlife risk factors as predictors. RESULTS: Women had significantly greater WMH volume relative to their WM volume compared to men (2.8% vs 2.4% of WM, p < 0.001), while men had a greater frequency of cortical infarctions compared to women (9% vs 4%, p < 0.001). Subcortical infarctions were equally common in men and women (20%). In regression modeling after adjustment for WM volume, the mean WMH volume difference between men and women was of the same magnitude as a 7-year difference in age. In contrast, men had 2.2-greater relative odds of having a cortical infarction compared to women. These sex differences persisted even after adjustment for midlife vascular risk factors. CONCLUSIONS: There were important sex differences in CVP findings on FLAIR in cognitively unimpaired elderly. Understanding these sex differences could aid in the development of sex-specific preventive strategies.

Magnetic resonance imaging of Alzheimer's pathology in the brains of living transgenic mice: a new tool in Alzheimer's disease research.

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Cardinal pathologic features of AD are amyloid plaques and neurofibrillary tangles, and most in the field believe that the initiating events ultimately leading to clinical AD center on disordered metabolism of amyloid beta protein. Mouse models of AD have been created by inserting one or more human mutations associated with disordered amyloid metabolism and that cause early onset familial AD into the mouse genome. Human-like amyloid plaque formation increases dramatically with age in these transgenic mice. Amyloid reduction in humans is a major therapeutic objective, and AD transgenic mice allow controlled study of this biology. Recent work has shown that amyloid plaques as small as 35 microm can be detected using in vivo magnetic resonance microimaging (MRMI) at high magnetic field (9.4 T). In addition, age-dependent changes in metabolite concentration analogous to those that have been identified in human AD patients can be detected in these transgenic mice using single-voxel (1)H magnetic resonance spectroscopy ((1)H MRS) at high magnetic field. These MR-based techniques provide a new set of tools to the scientific community engaged in studying the biology of AD in transgenic models of the disease. For example, an obvious application is evaluating therapeutic modification of disease progression. Toward the end of this review, the authors include results from a pilot study demonstrating feasibility of using MRMI to detect therapeutic modification of plaque progression in AD transgenic mice.

In vivo magnetic resonance microimaging of individual amyloid plaques in Alzheimer's transgenic mice.

The ability to detect individual Alzheimer's amyloid plaques in vivo by magnetic resonance microimaging (MRI) should improve diagnosis and also accelerate discovery of effective therapeutic agents for Alzheimer's disease (AD). Here, we perform in vivo and ex vivo MRI on double transgenic AD mice as well as wild-type mice at varying ages and correlate these with thioflavin-S and iron staining histology. Quantitative counts of individual plaques on MRI increase with age and correlate with histologically determined plaque burden. Plaques 20 microm in diameter can be detected in AD mice as young as 3 months of age with ex vivo MRI. Plaques 35 microm in diameter can be detected by 9 months of age with in vivo MRI. In vivo MRI of individual Alzheimer's amyloid plaques provides a noninvasive estimate of plaque burden in transgenic AD mice that might be useful in assessing the efficacy of amyloid reduction therapies.

Establishing magnetic resonance images orientation for the EADC-ADNI manual hippocampal segmentation protocol.

BACKGROUND AND PURPOSE: An effort to define and validate a Harmonized Protocol for standard hippocampal segmentation is being carried out. We wished to estimate the effect of magnetic resonance image (MRI) spatial orientation on manual hippocampal segmentations to define optimal standard orientation of MRIs for hippocampal volumetry. METHODS: Three expert tracers segmented twice the hippocampi of 10 ADNI subjects on MRI slices oriented perpendicular to the anterior-posterior commissure (AC-PC) line and the long hippocampal axes plane, following internationally harmonized landmarks. We computed intra and interrater reliability figures for total volumes and similarity coefficients. RESULTS: Total volume reliability was similar for both orientations. Similarity coefficients were significantly higher for the AC-PC orientation (exact P = 0.002). DISCUSSION: These data show that AC-PC orientation is slightly more reliable for manual segmentations, possibly due to better visualization of the cerebrospinal fluid spaces separating hippocampal head and amygdala. A Delphi panel of experts has used these data to decide on the optimal orientation for a Harmonized Protocol for hippocampal segmentation.

Age-specific population frequencies of cerebral ß-amyloidosis and neurodegeneration among people with normal cognitive function aged 50-89 years: a cross-sectional study.

BACKGROUND: As preclinical Alzheimer's disease becomes a target for therapeutic intervention, the overlap between imaging abnormalities associated with typical ageing and those associated with Alzheimer's disease needs to be recognised. We aimed to characterise how typical ageing and preclinical Alzheimer's disease overlap in terms of ß-amyloidosis and neurodegeneration. METHODS: We measured age-specific frequencies of amyloidosis and neurodegeneration in individuals with normal cognitive function aged 50-89 years. Potential participants were randomly selected from the Olmsted County (MN, USA) population-based study of cognitive ageing and invited to participate in cognitive and imaging assessments. To be eligible for inclusion, individuals must have been judged clinically to have no cognitive impairment and have undergone amyloid PET, (18)F-fluorodeoxyglucose ((18)F-FDG) PET, and MRI. Imaging results were obtained from March 28, 2006, to Dec 3, 2013. Amyloid status (positive [A(+)] or negative [A(-)]) was determined by amyloid PET with (11)C Pittsburgh compound B. Neurodegeneration status (positive [N(+)] or negative [N(-)]) was determined by an Alzheimer's disease signature (18)F-FDG PET or hippocampal volume on MRI. We determined age-specific frequencies of the four groups (amyloid negative and neurodegeneration negative [A(-)N(-)], amyloid positive and neurodegeneration negative [A(+)N(-)], amyloid negative and neurodegeneration positive [A(-)N(+)], or amyloid positive and neurodegeneration positive [A(+)N(+)]) cross-sectionally using multinomial regression models. We also investigated associations of group frequencies with APOE ɛ4 status (assessed with DNA extracted from blood) and sex by including these covariates in the multinomial models. FINDINGS: The study population consisted of 985 eligible participants. The population frequency of A(-)N(-) was 100% (n=985) at age 50 years and fell to 17% (95% CI 11-24) by age 89 years. The frequency of A(+)N(-) increased to 28% (24-32) at age 74 years, then decreased to 17% (11-25) by age 89 years. The frequency of A(-)N(+) increased from age 60 years, reaching 24% (16-34) by age 89 years. The frequency of A(+)N(+) increased from age 65 years, reaching 42% (31-52) by age 89 years. The results from our multinomial models suggest that A(+)N(-) and A(+)N(+) were more frequent in APOE ɛ4 carriers than in non-carriers and that A(+)N(+) was more, and A(+)N(-) less frequent in men than in women. INTERPRETATION: Accumulation of amyloid and neurodegeneration are nearly inevitable by old age, but many people are able to maintain normal cognitive function despite these imaging abnormalities. Changes in the frequency of amyloidosis and neurodegeneration with age, which seem to be modified by APOE ɛ4 and sex, suggest that pathophysiological sequences might differ between individuals. FUNDING: US National Institute on Aging and Alexander Family Professorship of Alzheimer's Disease Research.