Circulating angiopoietin-2 and angiogenic microRNAs associate with cerebral small vessel disease and cognitive decline in older patients reaching end stage renal disease

BACKGROUND

The prevalence of end-stage renal disease (ESRD) is increasing worldwide, with the majority of new ESRD cases diagnosed in patients aged >60 years. These older patients are at increased risk for impaired cognitive functioning, potentially through cerebral small vessel disease (SVD). Novel markers of vascular integrity may be of clinical value for identifying patients at high risk for cognitive impairment.

METHODS

We aimed to associate the levels of Angiopoietin-2 (Ang-2), asymmetric dimethylarginine (ADMA), and a selection of eight circulating angiogenic miRNAs with SVD and cognitive impairment in older patients reaching ESRD that did not initiate renal replacement therapy yet (n = 129; mean age 75.3 years; mean eGFR 16.4 mL/min). We assessed brain MRI changes of SVD (white matter hyperintensity volume, microbleeds and presence of lacunes) and measures of cognition in domains of memory, psychomotor speed and executive function, comprised in a neuropsychological test battery.

RESULTS

Older patients reaching ESRD showed an unfavorable angiogenic profile, as indicated by aberrant levels of Ang-2 and five angiogenic miRNAs (miR-27a, miR-126, miR-132, miR-223, miR-326), compared to healthy persons and patients with diabetic nephropathy. Moreover, Ang-2 associated with SVD and with the domains of psychomotor speed and executive function, while miR-223 and miR-29a associated with memory function.

CONCLUSIONS

Taken together, these novel angiogenic markers might serve to identify older patients with ESRD at risk of cognitive decline, as well as give insight into the underlying (vascular) pathophysiology.

Cerebral small vessel disease genomics and its implications across the lifespan

White matter hyperintensities (WMH) are the most common brain-imaging feature of cerebral small vessel disease (SVD), hypertension being the main known risk factor. Here, we identify 27 genome-wide loci for WMH-volume in a cohort of 50,970 older individuals, accounting for modification/confounding by hypertension. Aggregated WMH risk variants were associated with altered white matter integrity (p = 2.5×10-7) in brain images from 1,738 young healthy adults, providing insight into the lifetime impact of SVD genetic risk. Mendelian randomization suggested causal association of increasing WMH-volume with stroke, Alzheimer-type dementia, and of increasing blood pressure (BP) with larger WMH-volume, notably also in persons without clinical hypertension. Transcriptome-wide colocalization analyses showed association of WMH-volume with expression of 39 genes, of which four encode known drug targets. Finally, we provide insight into BP-independent biological pathways underlying SVD and suggest potential for genetic stratification of high-risk individuals and for genetically-informed prioritization of drug targets for prevention trials.

Sensitivity of the Edinburgh Criteria for Lobar Intracerebral Hemorrhage in Hereditary Cerebral Amyloid Angiopathy

BACKGROUND AND PURPOSE

The Edinburgh computed tomography and genetic criteria enable diagnosis of cerebral amyloid angiopathy (CAA) associated lobar intracerebral hemorrhage (ICH) but have not been validated in living patients. We assessed the sensitivity of the Edinburgh criteria in patients with acute lobar ICH due to Dutch-type hereditary CAA; a genetic and pure form of CAA.

METHODS

We retrospectively analyzed computed tomography-scans from a cohort of consecutive Dutch-type hereditary CAA patients who presented with ≥1 episode(s) of acute lobar ICH at the Leiden University Medical Center. Presence of subarachnoid hemorrhage (SAH) and finger-like projections (FLP) were determined. Association of SAH and FLP with ICH volume was analyzed using multivariate linear regression.

RESULTS

We included 55 Dutch-type hereditary CAA patients (mean age 56 years, 55% men) with a total of 107 episodes of acute lobar ICH. SAH was present in 82/107 (76%) and FLP in 62/107 (58%), resulting in a sensitivity of 76% for SAH and 58% for FLP. In 56 (52%), both markers were present. Nineteen (18%) lobar ICH showed no SAH extension or FLP. ICH volume was significantly associated with presence of SAH (median volume 4 versus 28 mL; P=0.001) and presence of FLP (median volume 7 versus 39 mL; P<0.001). With an ICH volume of ≥40 mL, the sensitivity of the presence of both SAH and FLP was >81% (95% CI, 70%-92%), whereas in ICH volumes <15 mL the sensitivity was <50%.

CONCLUSIONS

The computed tomography-based Edinburgh criteria seem to be a sensitive diagnostic test for CAA-associated lobar ICH, although they should be used with caution in small-sized lobar ICH.

Hypertensive Exposure Markers by MRI in Relation to Cerebral Small Vessel Disease and Cognitive Impairment

OBJECTIVES

This study sought to investigate the extent of hypertensive exposure as assessed by cardiovascular magnetic resonance imaging (MRI) in relation to cerebral small vessel disease (CSVD) and cognitive impairment, with the aim of understanding the role of hypertension in the early stages of deteriorating brain health.

BACKGROUND

Preserving brain health into advanced age is one of the great challenges of modern medicine. Hypertension is thought to induce vascular brain injury through exposure of the cerebral microcirculation to increased pressure/pulsatility. Cardiovascular MRI provides markers of (subclinical) hypertensive exposure, such as aortic stiffness by pulse wave velocity (PWV), left ventricular (LV) mass index (LVMi), and concentricity by mass-to-volume ratio.

METHODS

A total of 559 participants from the Heart-Brain Connection Study (431 patients with manifest cardiovascular disease and 128 control participants), age 67.8 ± 8.8 years, underwent 3.0-T heart-brain MRI and extensive neuropsychological testing. Aortic PWV, LVMi, and LV mass-to-volume ratio were evaluated in relation to presence of CSVD and cognitive impairment. Effect modification by patient group was investigated by interaction terms; results are reported pooled or stratified accordingly.

RESULTS

Aortic PWV (odds ratio [OR]: 1.17; 95% confidence interval [CI]: 1.05 to 1.30 in patient groups only), LVMi (in carotid occlusive disease, OR: 5.69; 95% CI: 1.63 to 19.87; in other groups, OR: 1.30; 95% CI: 1.05 to 1.62]) and LV mass-to-volume ratio (OR: 1.81; 95% CI: 1.46 to 2.24) were associated with CSVD. Aortic PWV (OR: 1.07; 95% CI: 1.02 to 1.13) and LV mass-to-volume ratio (OR: 1.27; 95% CI: 1.07 to 1.51) were also associated with cognitive impairment. Relations were independent of sociodemographic and cardiac index and mostly persisted after correction for systolic blood pressure or medical history of hypertension. Causal mediation analysis showed significant mediation by presence of CSVD in the relation between hypertensive exposure markers and cognitive impairment.

CONCLUSIONS

The extent of hypertensive exposure is associated with CSVD and cognitive impairment beyond clinical blood pressure or medical history. The mediating role of CSVD suggests that hypertension may lead to cognitive impairment through the occurrence of CSVD.

Pre-trained MRI-based Alzheimer's disease classification models to classify memory clinic patients

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Multimodal MRI AD classification models were pre-trained on AD patients and controls.

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Generalisation of these models was tested on a multi-centre memory clinic data set.

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AD scores were assigned to AD patients, MCI patients and memory complainers.

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Anatomical MRI performed better than diffusion MRI and resting state fMRI.

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Combining imaging modalities did not improve the results over anatomical MRI only.

Anatomical magnetic resonance imaging (MRI), diffusion MRI and resting state functional MRI (rs-fMRI) have been used for Alzheimer’s disease (AD) classification. These scans are typically used to build models for discriminating AD patients from control subjects, but it is not clear if these models can also discriminate AD in diverse clinical populations as found in memory clinics.

To study this, we trained MRI-based AD classification models on a single centre data set consisting of AD patients (N = 76) and controls (N = 173), and used these models to assign AD scores to subjective memory complainers (N = 67), mild cognitive impairment (MCI) patients (N = 61), and AD patients (N = 61) from a multi-centre memory clinic data set. The anatomical MRI scans were used to calculate grey matter density, subcortical volumes and cortical thickness, the diffusion MRI scans were used to calculate fractional anisotropy, mean, axial and radial diffusivity, and the rs-fMRI scans were used to calculate functional connectivity between resting state networks and amplitude of low frequency fluctuations. Within the multi-centre memory clinic data set we removed scan site differences prior to applying the models.

For all models, on average, the AD patients were assigned the highest AD scores, followed by MCI patients, and later followed by SMC subjects. The anatomical MRI models performed best, and the best performing anatomical MRI measure was grey matter density, separating SMC subjects from MCI patients with an AUC of 0.69, MCI patients from AD patients with an AUC of 0.70, and SMC patients from AD patients with an AUC of 0.86. The diffusion MRI models did not generalise well to the memory clinic data, possibly because of large scan site differences. The functional connectivity model separated SMC subjects and MCI patients relatively good (AUC = 0.66). The multimodal MRI model did not improve upon the anatomical MRI model.

In conclusion, we showed that the grey matter density model generalises best to memory clinic subjects. When also considering the fact that grey matter density generally performs well in AD classification studies, this feature is probably the best MRI-based feature for AD diagnosis in clinical practice.

Association of High-Density Lipoprotein Cholesterol With Cognitive Function: Findings From the PROspective Study of Pravastatin in the Elderly at Risk

Objective: We aimed to examine whether variability in high-density lipoprotein cholesterol (HDL-c) over time was associated with cognitive function. Method: We conducted a post hoc analysis of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) trial. Our sample included 4,428 participants with at least two repeated HDL-c measures between Months 3 and 24 postbaseline and with cognitive assessments at Month 30. HDL-c variability was defined as the intraindividual standard deviation over each person's repeated measurements. Results: Higher HDL-c variability was associated with worse performance on the Letter-Digit Coding Test (β [95% confidence interval] [CI] = -4.39 [-7.36, -1.43], p = .004), immediate recall on the 15-Picture Learning Test (β [95% CI] = -0.98 [-1.86, -0.11], p = .027), and delayed recall on the 15-Picture Learning Test (β [95% CI] = -1.90 [-3.14, -0.67], p = .002). The associations did not vary by treatment group. Discussion: Our findings suggest that variability in HDL-c may be associated with poor cognitive function among older adults.

Cerebral blood flow and cognitive functioning in patients with disorders along the heart-brain axis: Cerebral blood flow and the heart-brain axis

INTRODUCTION

We examined the role of hemodynamic dysfunction in cognition by relating cerebral blood flow (CBF), measured with arterial spin labeling (ASL), to cognitive functioning, in patients with heart failure (HF), carotid occlusive disease (COD), and patients with cognitive complaints and vascular brain injury on magnetic resonance imaging (MRI; ie, possible vascular cognitive impairment [VCI]).

METHODS

We included 439 participants (124 HF; 75 COD; 127 possible VCI; 113 reference participants) from the Dutch multi-center Heart-Brain Study. We used pseudo-continuous ASL to estimate whole-brain and regional partial volume-corrected CBF. Neuropsychological tests covered global cognition and four cognitive domains.

RESULTS

CBF values were lowest in COD, followed by VCI and HF, compared to reference participants. This did not explain cognitive impairment, as we did not find an association between CBF and cognitive functioning.

DISCUSSION

We found that reduced CBF is not the major explanatory factor underlying cognitive impairment in patients with hemodynamic dysfunction along the heart-brain axis.

MRI evaluation of the relationship between carotid artery endothelial shear stress and brain white matter lesions in migraine

Although white matter lesions are frequently detected in migraine patients, underlying mechanisms remain unclear. Low carotid artery endothelial shear stress has been associated with white matter lesions. We aimed to investigate the association between carotid artery endothelial shear stress and white matter lesions in migraine. In 40 elderly migraine patients (n = 29 females, 75 years [SD 3]) and 219 controls (n = 80 females, 74 years [SD 3]) from the PROSPER-MRI study, carotid artery endothelial shear stress was estimated on 1.5 T gradient-echo phase contrast MRI. White matter lesion volumes were calculated from structural MRI scans. Analyses were adjusted for age, sex, cardiovascular risk factors and cardiovascular disease. Migraine patients had lower mean endothelial shear stress compared to controls (0.90 [SD 0.15] vs. 0.98 [SD 0.16] Pa; P = 0.03). The association between mean endothelial shear stress and white matter lesion volume was greater for the migraine group than control group (P for interaction = 0.05). Within the migraine group, white matter lesion volume increased with decreasing endothelial shear stress (β-0.421; P = 0.01). In conclusion, migraine patients had lower endothelial shear stress which was associated with higher white matter lesion volume.

Patterns and characteristics of cognitive functioning in older patients approaching end stage kidney disease, the COPE-study

BACKGROUND

The prevalence of impaired cognitive functioning in older patients with end stage kidney disease (ESKD) is high. We aim to describe patterns of memory, executive function or psychomotor speed and to identify nephrologic, geriatric and neuroradiologic characteristics associated with cognitive impairment in older patients approaching ESKD who have not yet started with renal replacement therapy (RRT).

METHODS

The COPE-study (Cognitive Decline in Older Patients with ESRD) is a prospective cohort study including 157 participants aged 65 years and older approaching ESKD (eGFR ≤20 ml/min/1.73 m²) prior to starting with RRT. In addition to routinely collected clinical parameters related to ESKD, such as vascular disease burden and parameters of metabolic disturbance, patients received a full geriatric assessment, including extensive neuropsychological testing. In a subgroup of patients (n = 93) a brain MRI was performed.

RESULTS

The median age was 75.3 years. Compared to the normative data of neuropsychological testing participants memory performance was in the 24th percentile, executive function in the 18th percentile and psychomotor speed in the 20th percentile. Independent associated characteristics of impairment in memory, executive and psychomotor speed were high age, low educational level and low functional status (all p-values < 0.003). A history of vascular disease (p = 0.007) and more white matter hyperintensities on brain MRI (p = 0.013) were associated with a lower psychomotor speed.

CONCLUSION

Older patients approaching ESKD have a high prevalence of impaired memory, executive function and psychomotor speed. The patterns of cognitive impairment and brain changes on MRI are suggestive of vascular cognitive impairment. These findings could be of potentially added value in the decision-making process concerning patients with ESKD.

Multiple Approaches to Diffusion Magnetic Resonance Imaging in Hereditary Cerebral Amyloid Angiopathy Mutation Carriers

Background Cerebral amyloid angiopathy ( CAA ) is a major cause of lobar intracerebral hemorrhage in elderly adults; however, presymptomatic diagnosis of CAA is difficult. Hereditary cerebral hemorrhage with amyloidosis-Dutch type ( HCHWA -D) is a rare autosomal-dominant disease that leads to pathology similar to sporadic CAA . Presymptomatic HCHWA -D mutation carriers provide a unique opportunity to study CAA -related changes before any symptoms have occurred. In this study we investigated early CAA -related alterations in the white matter. Methods and Results We investigated diffusion magnetic resonance imaging ( dMRI ) data for 15 symptomatic and 11 presymptomatic HCHWA -D mutation carriers and 30 noncarrier control participants using 4 different approaches. We looked at (1) the relation between age and global dMRI measures for mutation carriers versus controls, (2) voxel-wise d MRI , (3) independent component-clustered dMRI measures, and (4) structural connectomics between presymptomatic or symptomatic carriers and controls. Fractional anisotropy decreased, and mean diffusivity and peak width of the skeletonized mean diffusivity increased significantly over age for mutation carriers compared with controls. In addition, voxel-wise and independent component-wise fractional anisotropy, and mean diffusivity, and structural connectomics were significantly different between HCHWA -D patients and control participants, mainly in the periventricular frontal and occipital regions and in the occipital lobe. We found no significant differences between presymptomatic carriers and control participants. Conclusions The d MRI technique is sensitive in detecting alterations in symptomatic HCHWA -d carriers but did not show alterations in presymptomatic carriers. This result indicates that d MRI may be less suitable for identifying early white matter changes in CAA .

Multimodal MRI of grey matter, white matter, and functional connectivity in cognitively healthy mutation carriers at risk for frontotemporal dementia and Alzheimer's disease

BACKGROUND

Frontotemporal dementia (FTD) and Alzheimer's disease (AD) are associated with divergent differences in grey matter volume, white matter diffusion, and functional connectivity. However, it is unknown at what disease stage these differences emerge. Here, we investigate whether divergent differences in grey matter volume, white matter diffusion, and functional connectivity are already apparent between cognitively healthy carriers of pathogenic FTD mutations, and cognitively healthy carriers at increased AD risk.

METHODS

We acquired multimodal magnetic resonance imaging (MRI) brain scans in cognitively healthy subjects with (n=39) and without (n=36) microtubule-associated protein Tau (MAPT) or progranulin (GRN) mutations, and with (n=37) and without (n=38) apolipoprotein E ε4 (APOE4) allele. We evaluated grey matter volume using voxel-based morphometry, white matter diffusion using tract-based spatial statistics (TBSS), and region-to-network functional connectivity using dual regression in the default mode network and salience network. We tested for differences between the respective carriers and controls, as well as for divergence of those differences. For the divergence contrast, we additionally performed region-of-interest TBSS analyses in known areas of white matter diffusion differences between FTD and AD (i.e., uncinate fasciculus, forceps minor, and anterior thalamic radiation).

RESULTS

MAPT/GRN carriers did not differ from controls in any modality. APOE4 carriers had lower fractional anisotropy than controls in the callosal splenium and right inferior fronto-occipital fasciculus, but did not show grey matter volume or functional connectivity differences. We found no divergent differences between both carrier-control contrasts in any modality, even in region-of-interest analyses.

CONCLUSIONS

Concluding, we could not find differences suggestive of divergent pathways of underlying FTD and AD pathology in asymptomatic risk mutation carriers. Future studies should focus on asymptomatic mutation carriers that are closer to symptom onset to capture the first specific signs that may differentiate between FTD and AD.

Advancing diagnostic criteria for sporadic cerebral amyloid angiopathy: Study protocol for a multicenter MRI-pathology validation of Boston criteria v2.0

RATIONALE

The Boston criteria are used worldwide for the in vivo diagnosis of cerebral amyloid angiopathy and are the basis for clinical decision-making and research in the field. Given substantial advances in cerebral amyloid angiopathy's clinical aspects and MRI biomarkers, we designed a multicenter study within the International cerebral amyloid angiopathy Association aimed at further validating the diagnostic accuracy of the Boston and potentially improving and updating them.

AIM

We aim to derive and validate an updated "version 2.0" of the Boston criteria across the spectrum of cerebral amyloid angiopathy-related presentations and MRI biomarkers.

SAMPLE SIZE ESTIMATES

Participating centers with suitable available data (see Methods) were identified from existing collaborations and an open invitation to the International Cerebral Amyloid Angiopathy Association emailing list. Our study sample will include: (1) a derivation cohort - Massachusetts General Hospital (MGH), Boston cases from inception to 2012 (∼150 patients); (2) temporal external validation cohort - MGH, Boston cases from 2012 to 2018 (∼100 patients); and (3) geographical external validation cohort - non-Boston cases (∼85 patients).

METHODS AND DESIGN

Multicenter collaborative study. We will collect and analyze data from patients' age ≥ 50 with any potential sporadic cerebral amyloid angiopathy-related clinical presentations (spontaneous intracerebral hemorrhage, transient focal neurological episodes and cognitive impairment), available brain MRI ("index test"), and histopathologic assessment for cerebral amyloid angiopathy ("reference standard" for diagnosis). Trained raters will assess MRI for all prespecified hemorrhagic and non-hemorrhagic small vessel disease markers of interest, according to validated criteria and a prespecified protocol, masked to clinical and histopathologic features. Brain tissue samples will be rated for cerebral amyloid angiopathy, defined as Vonsattel grade ≥2 for whole brain autopsies and ≥1 for cortical biopsies or hematoma evacuation. Based on our estimated available sample size, we will undertake pre-specified cohort splitting as above. We will: (a) pre-specify variables and statistical cut-offs; (b) examine univariable and multivariable associations; and (c) then assess classification measures (sensitivity, specificity etc.) for each MRI biomarker individually, in relation to the cerebral amyloid angiopathy diagnosis reference standard on neuropathology in a derivation cohort. The MRI biomarkers strongly associated with cerebral amyloid angiopathy diagnosis will be selected for inclusion in provisional (probable and possible cerebral amyloid angiopathy) Boston criteria v2.0 and validated using appropriate metrics and models.

STUDY OUTCOMES

Boston criteria v2.0 for clinical cerebral amyloid angiopathy diagnosis.

DISCUSSION

This work aims to potentially update and improve the diagnostic test accuracy of the Boston criteria for cerebral amyloid angiopathy and to provide wider validation of the criteria in a large sample. We envision that this work will meet the needs of clinicians and investigators and help accelerate progress towards better treatment of cerebral amyloid angiopathy.

Exome Chip Analysis Identifies Low-Frequency and Rare Variants in MRPL38 for White Matter Hyperintensities on Brain Magnetic Resonance Imaging

Background and Purpose- White matter hyperintensities (WMH) on brain magnetic resonance imaging are typical signs of cerebral small vessel disease and may indicate various preclinical, age-related neurological disorders, such as stroke. Though WMH are highly heritable, known common variants explain a small proportion of the WMH variance. The contribution of low-frequency/rare coding variants to WMH burden has not been explored. Methods- In the discovery sample we recruited 20 719 stroke/dementia-free adults from 13 population-based cohort studies within the Cohorts for Heart and Aging Research in Genomic Epidemiology consortium, among which 17 790 were of European ancestry and 2929 of African ancestry. We genotyped these participants at ≈250 000 mostly exonic variants with Illumina HumanExome BeadChip arrays. We performed ethnicity-specific linear regression on rank-normalized WMH in each study separately, which were then combined in meta-analyses to test for association with single variants and genes aggregating the effects of putatively functional low-frequency/rare variants. We then sought replication of the top findings in 1192 adults (European ancestry) with whole exome/genome sequencing data from 2 independent studies. Results- At 17q25, we confirmed the association of multiple common variants in TRIM65, FBF1, and ACOX1 ( P<6×10^-7). We also identified a novel association with 2 low-frequency nonsynonymous variants in MRPL38 (lead, rs34136221; P_EA=4.5×10^-8) partially independent of known common signal ( P_{EA(conditional)}=1.4×10^-3). We further identified a locus at 2q33 containing common variants in NBEAL1, CARF, and WDR12 (lead, rs2351524; P_all=1.9×10^-10). Although our novel findings were not replicated because of limited power and possible differences in study design, meta-analysis of the discovery and replication samples yielded stronger association for the 2 low-frequency MRPL38 variants ( P_rs34136221=2.8×10^-8). Conclusions- Both common and low-frequency/rare functional variants influence WMH. Larger replication and experimental follow-up are essential to confirm our findings and uncover the biological causal mechanisms of age-related WMH.

Amyloid imaging of dutch-type hereditary cerebral amyloid angiopathy carriers

OBJECTIVE

To determine whether amyloid imaging with the positron emission tomography (PET) agent Pittsburgh compound B (PiB) can detect vascular β-amyloid (Aβ) in the essentially pure form of cerebral amyloid angiopathy associated with the Dutch-type hereditary cerebral amyloid angiopathy (D-CAA) mutation.

METHODS

PiB retention in a cortical composite of frontal, lateral, and retrosplenial regions (FLR) was measured by PiB-PET in 19 D-CAA mutation carriers (M⁺ ; 13 without neurologic symptoms, 6 with prior lobar intracerebral hemorrhage) and 17 mutation noncarriers (M^- ). Progression of PiB retention was analyzed in a subset of 18 serially imaged individuals (10 asymptomatic M⁺ , 8 M^- ). We also analyzed associations between PiB retention and cerebrospinal fluid (CSF) Aβ concentrations in 17 M⁺ and 11 M^- participants who underwent lumbar puncture and compared the findings to PiB-PET and CSF Aβ in 37 autosomal dominant Alzheimer disease (ADAD) mutation carriers.

RESULTS

D-CAA M⁺ showed greater age-dependent FLR PiB retention (p < 0.001) than M^- , and serially imaged asymptomatic M⁺ demonstrated greater longitudinal increases (p = 0.004). Among M⁺ , greater FLR PiB retention associated with reduced CSF concentrations of Aβ40 (r = -0.55, p = 0.021) but not Aβ42 (r = 0.01, p = 0.991). Despite comparably low CSF Aβ40 and Aβ42, PiB retention was substantially less in D-CAA than ADAD (p < 0.001).

INTERPRETATION

Increased PiB retention in D-CAA and correlation with reduced CSF Aβ40 suggest this compound labels vascular amyloid, although to a lesser degree than amyloid deposits in ADAD. Progression in PiB signal over time suggests amyloid PET as a potential biomarker in trials of candidate agents for this untreatable cause of hemorrhagic stroke. ANN NEUROL 2019;86:616-625.

Microstructural white matter changes preceding white matter hyperintensities in migraine

OBJECTIVE

We used magnetization transfer imaging to assess white matter tissue integrity in migraine, to explore whether white matter microstructure was more diffusely affected beyond visible white matter hyperintensities (WMHs), and to explore whether focal invisible microstructural changes precede visible focal WMHs in migraineurs.

METHODS

We included 137 migraineurs (79 with aura, 58 without aura) and 74 controls from the Cerebral Abnormalities in Migraine, an Epidemiological Risk Analysis (CAMERA) study, a longitudinal population-based study on structural brain lesions in migraine patients, who were scanned at baseline and at a 9-year follow-up. To assess microstructural brain tissue integrity, baseline magnetization transfer ratio (MTR) values were calculated for whole brain white matter. Baseline MTR values were determined for areas of normal-appearing white matter (NAWM) that had progressed into MRI-detectable WMHs at follow-up and compared to MTR values of contralateral NAWM.

RESULTS

MTR values for whole brain white matter did not differ between migraineurs and controls. In migraineurs, but not in controls, NAWM that later progressed to WMHs at follow-up had lower mean MTR (mean [SD] 0.354 [0.009] vs 0.356 [0.008], p = 0.047) at baseline as compared to contralateral white matter.

CONCLUSIONS

We did not find evidence for widespread microstructural white matter changes in migraineurs compared to controls. However, our findings suggest that a gradual or stepwise process might be responsible for evolution of focal invisible microstructural changes into focal migraine-related visible WMHs.

Distribution of cerebral microbleeds in the East and West: Individual participant meta-analysis

OBJECTIVE

We investigated differences in the anatomical distribution of cerebral microbleeds (CMBs) on MRI, hypothesized to indicate the type of underlying cerebral small vessel disease (SVD), between Eastern and Western general populations.

METHODS

We analyzed data from 11 studies identified by a PubMed search between 1996 and April 2014 according to the Preferred Reporting Items for a Systematic Review and Meta-analysis of Individual Participant Data. Study quality measures indicated low or medium risk of bias. We included stroke-free participants from populations aged between 55 and 75 years, categorized by geographic location (Eastern or Western). We categorized CMB distribution (strictly lobar, deep and/or infratentorial [D/I], or mixed [i.e., CMBs located in both lobar and D/I regions]). We tested the hypothesis that Eastern and Western populations have different anatomical distributions of CMBs using multivariable mixed effects logistic regression analyses adjusted for age, sex, and hypertension and clustering by institution.

RESULTS

Among 8,595 stroke-free individuals (mean age [SD] 66.7 [5.6] years; 48% male; 42% from a Western population), 624 (7.3%) had CMBs (strictly lobar in 3.1%; D/I or mixed in 4.2%). In multivariable mixed effects models, Eastern populations had higher odds of D/I or mixed CMBs (adjusted odds ratio 2.78, 95% confidence interval [CI] 1.77-4.35) compared to Western populations. Eastern populations had a higher number of D/I or mixed CMBs (adjusted prevalence ratio 2.83, 95% CI 1.27-6.31).

CONCLUSIONS

Eastern and Western general populations have different anatomical distributions of CMBs, suggesting differences in the spectrum of predominant underlying SVDs, with potential implications for SVD diagnosis and treatment.

Vascular dysfunction-The disregarded partner of Alzheimer's disease

Increasing evidence recognizes Alzheimer's disease (AD) as a multifactorial and heterogeneous disease with multiple contributors to its pathophysiology, including vascular dysfunction. The recently updated AD Research Framework put forth by the National Institute on Aging-Alzheimer's Association describes a biomarker-based pathologic definition of AD focused on amyloid, tau, and neuronal injury. In response to this article, here we first discussed evidence that vascular dysfunction is an important early event in AD pathophysiology. Next, we examined various imaging sequences that could be easily implemented to evaluate different types of vascular dysfunction associated with, and/or contributing to, AD pathophysiology, including changes in blood-brain barrier integrity and cerebral blood flow. Vascular imaging biomarkers of small vessel disease of the brain, which is responsible for >50% of dementia worldwide, including AD, are already established, well characterized, and easy to recognize. We suggest that these vascular biomarkers should be incorporated into the AD Research Framework to gain a better understanding of AD pathophysiology and aid in treatment efforts.

Laboratory and Neuroimaging Biomarkers in Neuropsychiatric Systemic Lupus Erythematosus: Where Do We Stand, Where To Go?

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by multi-systemic involvement. Nervous system involvement in SLE leads to a series of uncommon and heterogeneous neuropsychiatric (NP) manifestations. Current knowledge on the underlying pathogenic processes and their subsequent pathophysiological changes leading to NP-SLE manifestations is incomplete. Several putative laboratory biomarkers have been proposed as contributors to the genesis of SLE-related nervous system damage. Alongside the laboratory biomarkers, several neuroimaging tools have shown to reflect the nature of tissue microstructural damage associated with SLE, and thus were suggested to contribute to the understanding of the pathophysiological changes and subsequently help in clinical decision making. However, the number of useful biomarkers in NP-SLE in clinical practice is disconcertingly modest. In some cases it is not clear whether the biomarker is truly involved in pathogenesis, or the result of non-specific pathophysiological changes in the nervous system (e.g., neuroinflammation) or whether it is the consequence of a concomitant underlying abnormality related to SLE activity. In order to improve the diagnosis of NP-SLE and provide a better targeted care to these patients, there is still a need to develop and validate a range of biomarkers that reliably capture the different aspects of disease heterogeneity. This article critically reviews the current state of knowledge on laboratory and neuroimaging biomarkers in NP-SLE, discusses the factors that need to be addressed to make these biomarkers suitable for clinical application, and suggests potential future research paths to address important unmet needs in the NP-SLE field.

The AGES-Reykjavik Study suggests that change in kidney measures is associated with subclinical brain pathology in older community-dwelling persons

Decreased glomerular filtration rate (GFR) and albuminuria may be accompanied by brain pathology. Here we investigated whether changes in these kidney measures are linked to development of new MRI-detected infarcts and microbleeds, and progression of white matter hyperintensity volume. The study included 2671 participants from the population-based AGES-Reykjavik Study (mean age 75, 58.7% women). GFR was estimated from serum creatinine, and albuminuria was assessed by urinary albumin-to-creatinine ratio. Brain MRI was acquired at baseline (2002-2006) and 5 years later (2007-2011). New MRI-detected infarcts and microbleeds were counted on the follow-up scans. White matter hyperintensity progression was estimated as percent change in white matter hyperintensity volumes between the two exams. Participants with a large eGFR decline (over 3 ml/min/1.73m2 per year) had more incident subcortical infarcts (odds ratio 1.53; 95% confidence interval 1.05, 2.22), and more marked progression of white matter hyperintensity volume (difference: 8%; 95% confidence interval: 4%, 12%), compared to participants without a large decline. Participants with incident albuminuria (over 30 mg/g) had 21% more white matter hyperintensity volume progression (95% confidence interval: 14%, 29%) and 1.86 higher odds of developing new deep microbleeds (95% confidence interval 1.16, 2.98), compared to participants without incident albuminuria. The findings were independent of cardiovascular risk factors. Changes in kidney measures were not associated with occurrence of cortical infarcts. Thus, larger changes in eGFR and albuminuria are associated with increased risk for developing manifestations of cerebral small vessel disease. Individuals with larger changes in these kidney measures should be considered as a high risk population for accelerated brain pathology.

Cortical Iron Reflects Severity of Alzheimer's Disease

Abnormal iron distribution in the isocortex is increasingly recognized as an in vivo marker for Alzheimer’s disease (AD). However, the contribution of iron accumulation to the AD pathology is still poorly understood. In this study, we investigated: 1) frontal cortical iron distribution in AD and normal aging and 2) the relation between iron distribution and degree of AD pathology. We used formalin fixed paraffin embedded frontal cortex from 10 AD patients, 10 elder, 10 middle aged, and 10 young controls and visualized iron with a modified Perl’s histochemical procedure. AD and elderly subjects were not different with respect to age and sex distribution. Iron distribution in the frontal cortex was not affected by normal aging but was clearly different between AD and controls. AD showed accumulation of iron in plaques, activated microglia, and, in the most severe cases, in the mid-cortical layers along myelinated fibers. The degree of altered iron accumulations was correlated to the amount of amyloid-β plaques and tau pathology in the same block, as well as to Braak stage (p < 0.001). AD and normal aging show different iron and myelin distribution in frontal cortex. These changes appear to occur after the development of the AD pathological hallmarks. These findings may help the interpretation of high resolution in vivo MRI and suggest the potential of using changes in iron-based MRI contrast to indirectly determine the degree of AD pathology in the frontal cortex.

Clinical significance of cerebral microbleeds on MRI: A comprehensive meta-analysis of risk of intracerebral hemorrhage, ischemic stroke, mortality, and dementia in cohort studies (v1)

Background Cerebral microbleeds can confer a high risk of intracerebral hemorrhage, ischemic stroke, death and dementia, but estimated risks remain imprecise and often conflicting. We investigated the association between cerebral microbleeds presence and these outcomes in a large meta-analysis of all published cohorts including: ischemic stroke/TIA, memory clinic, "high risk" elderly populations, and healthy individuals in population-based studies. Methods Cohorts (with > 100 participants) that assessed cerebral microbleeds presence on MRI, with subsequent follow-up (≥3 months) were identified. The association between cerebral microbleeds and each of the outcomes (ischemic stroke, intracerebral hemorrhage, death, and dementia) was quantified using random effects models of (a) unadjusted crude odds ratios and (b) covariate-adjusted hazard rations. Results We identified 31 cohorts ( n = 20,368): 19 ischemic stroke/TIA ( n = 7672), 4 memory clinic ( n = 1957), 3 high risk elderly ( n = 1458) and 5 population-based cohorts ( n = 11,722). Cerebral microbleeds were associated with an increased risk of ischemic stroke (OR: 2.14; 95% CI: 1.58-2.89 and adj-HR: 2.09; 95% CI: 1.71-2.57), but the relative increase in future intracerebral hemorrhage risk was greater (OR: 4.65; 95% CI: 2.68-8.08 and adj-HR: 3.93; 95% CI: 2.71-5.69). Cerebral microbleeds were an independent predictor of all-cause mortality (adj-HR: 1.36; 95% CI: 1.24-1.48). In three population-based studies, cerebral microbleeds were independently associated with incident dementia (adj-HR: 1.35; 95% CI: 1.00-1.82). Results were overall consistent in analyses stratified by different populations, but with different degrees of heterogeneity. Conclusions Our meta-analysis shows that cerebral microbleeds predict an increased risk of stroke, death, and dementia and provides up-to-date effect sizes across different clinical settings. These pooled estimates can inform clinical decisions and trials, further supporting cerebral microbleeds role as biomarkers of underlying subclinical brain pathology in research and clinical settings.

Aging modifies the effect of cardiac output on middle cerebral artery blood flow velocity

An association between cerebral blood flow (CBF) and cardiac output (CO) has been established in young healthy subjects. As of yet it is unclear how this association evolves over the life span. To that purpose, we continuously recorded mean arterial pressure (MAP; finger plethysmography), CO (pulse contour; CO‐trek), mean blood flow velocity in the middle cerebral artery (MCAV; transcranial Doppler ultrasonography), and end‐tidal CO₂ partial pressure (PetCO₂) in healthy young (19–27 years), middle‐aged (51–61 years), and elderly subjects (70–79 years). Decreases and increases in CO were accomplished using lower body negative pressure and dynamic handgrip exercise, respectively. Aging in itself did not alter dynamic cerebral autoregulation or cerebrovascular CO₂ reactivity. A linear relation between changes in CO and MCAV_mean was observed in middle‐aged (P < 0.01) and elderly (P = 0.04) subjects but not in young (P = 0.45) subjects, taking concurrent changes in MAP and PetCO₂ into account. These data imply that with aging, brain perfusion becomes increasingly dependent on CO.