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Objective: To identify common genetic variants associated with the presence of brain microbleeds (BMBs)., Methods: We performed genome-wide association studies in 11 population-based cohort studies and 3 case-control or case-only stroke cohorts. Genotypes were imputed to the Haplotype Reference Consortium or 1000 Genomes reference panel. BMBs were rated on susceptibility-weighted or T2*-weighted gradient echo MRI sequences, and further classified as lobar or mixed (including strictly deep and infratentorial, possibly with lobar BMB). In a subset, we assessed the effects of APOE ε2 and ε4 alleles on BMB counts. We also related previously identified cerebral small vessel disease variants to BMBs., Results: BMBs were detected in 3,556 of the 25,862 participants, of which 2,179 were strictly lobar and 1,293 mixed. One locus in the APOE region reached genome-wide significance for its association with BMB (lead single nucleotide polymorphism rs769449; odds ratio [OR] any BMB [95% confidence interval (CI)] 1.33 [1.21-1.45]; p = 2.5 × 10 -10 ). APOE ε4 alleles were associated with strictly lobar (OR [95% CI] 1.34 [1.19-1.50]; p = 1.0 × 10 -6 ) but not with mixed BMB counts (OR [95% CI] 1.04 [0.86-1.25]; p = 0.68). APOE ε2 alleles did not show associations with BMB counts. Variants previously related to deep intracerebral hemorrhage and lacunar stroke, and a risk score of cerebral white matter hyperintensity variants, were associated with BMB., Conclusions: Genetic variants in the APOE region are associated with the presence of BMB, most likely due to the APOE ε4 allele count related to a higher number of strictly lobar BMBs. Genetic predisposition to small vessel disease confers risk of BMB, indicating genetic overlap with other cerebral small vessel disease markers., (Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Objective: To explore genetic and lifestyle risk factors of MRI-defined brain infarcts (BI) in large population-based cohorts., Methods: We performed meta-analyses of genome-wide association studies (GWAS) and examined associations of vascular risk factors and their genetic risk scores (GRS) with MRI-defined BI and a subset of BI, namely, small subcortical BI (SSBI), in 18 population-based cohorts (n = 20,949) from 5 ethnicities (3,726 with BI, 2,021 with SSBI). Top loci were followed up in 7 population-based cohorts (n = 6,862; 1,483 with BI, 630 with SBBI), and we tested associations with related phenotypes including ischemic stroke and pathologically defined BI., Results: The mean prevalence was 17.7% for BI and 10.5% for SSBI, steeply rising after age 65. Two loci showed genome-wide significant association with BI: FBN2, p = 1.77 × 10 -8 ; and LINC00539/ZDHHC20, p = 5.82 × 10 -9 . Both have been associated with blood pressure (BP)-related phenotypes, but did not replicate in the smaller follow-up sample or show associations with related phenotypes. Age- and sex-adjusted associations with BI and SSBI were observed for BP traits ( p value for BI, p [BI] = 9.38 × 10 -25 ; p [SSBI] = 5.23 × 10 -14 for hypertension), smoking ( p [BI] = 4.4 × 10 -10 ; p [SSBI] = 1.2 × 10 -4 ), diabetes ( p [BI] = 1.7 × 10 -8 ; p [SSBI] = 2.8 × 10 -3 ), previous cardiovascular disease ( p [BI] = 1.0 × 10 -18 ; p [SSBI] = 2.3 × 10 -7 ), stroke ( p [BI] = 3.9 × 10 -69 ; p [SSBI] = 3.2 × 10 -24 ), and MRI-defined white matter hyperintensity burden ( p [BI] = 1.43 × 10 -157 ; p [SSBI] = 3.16 × 10 -106 ), but not with body mass index or cholesterol. GRS of BP traits were associated with BI and SSBI ( p ≤ 0.0022), without indication of directional pleiotropy., Conclusion: In this multiethnic GWAS meta-analysis, including over 20,000 population-based participants, we identified genetic risk loci for BI requiring validation once additional large datasets become available. High BP, including genetically determined, was the most significant modifiable, causal risk factor for BI., (Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Objective: To investigate CSF biomarkers in presymptomatic and symptomatic mutation carriers with hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D), a model for sporadic cerebral amyloid angiopathy, and to determine the earliest deposited form of β-amyloid (Aβ)., Methods: HCHWA-D mutation carriers and controls were enrolled in the cross-sectional EDAN (Early Diagnosis of Amyloid Angiopathy Network) study. The HCHWA-D group was divided into symptomatic carriers with a previous intracerebral hemorrhage and presymptomatic carriers. CSF concentrations of Aβ 40 , Aβ 42 , total tau, and phosphorylated tau 181 proteins were compared to those of controls of a similar age. Correlations between CSF biomarkers, MRI markers, and age were investigated with multivariate linear regression analyses., Results: We included 10 symptomatic patients with HCHWA-D (mean age 55 ± 6 years), 5 presymptomatic HCHWA-D carriers (mean age 36 ± 13 years), 31 controls <50 years old (mean age 31 ± 7 years), and 50 controls ≥50 years old (mean age 61 ± 8 years). After correction for age, CSF Aβ 40 and Aβ 42 were significantly decreased in symptomatic carriers vs controls (median Aβ 40 1,386 vs 3,867 ng/L, p < 0.001; median Aβ 42 289 vs 839 ng/L, p < 0.001) and in presymptomatic carriers vs controls (median Aβ 40 3,501 vs 4,684 ng/L, p = 0.011; median Aβ 42 581 vs 1,058 ng/L, p < 0.001). Among mutation carriers, decreasing CSF Aβ 40 was associated with higher lobar microbleed count (p = 0.010), increasing white matter hyperintensity volume (p = 0.008), and presence of cortical superficial siderosis (p = 0.02)., Conclusions: Decreased levels of CSF Aβ 40 and Aβ 42 occur before HCHWA-D mutation carriers develop clinical symptoms, implicating vascular deposition of both Aβ species as early steps in cerebral amyloid angiopathy pathogenesis. CSF Aβ 40 and Aβ 42 may serve as preclinical biomarkers of cerebral amyloid angiopathy pathology., (© 2016 American Academy of Neurology.)

Objective: To determine whether hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D), a monogenetic disease model for the sporadic variant of amyloid angiopathy (sCAA), has a comparable recurrent intracerebral hemorrhage (ICH) risk and mortality after a first symptomatic ICH., Methods: We included patients with HCHWA-D from the Leiden University Medical Center and patients with sCAA from the Massachusetts General Hospital in a cohort study. Baseline characteristics, hemorrhage recurrence, and short- and long-term mortality were compared. Hazard ratios (HRs) adjusted for age and sex were calculated with Cox regression analyses., Results: We included 58 patients with HCHWA-D and 316 patients with sCAA. Patients with HCHWA-D had fewer cardiovascular risk factors (≥1 risk factor 24% vs 70% in sCAA) and were younger at the time of presenting hemorrhage (mean age 54 vs 72 years in sCAA). Eight patients (14%) with HCHWA-D and 46 patients (15%) with sCAA died before 90 days. During a mean follow-up time of 5 ± 4 years (total 1,550 person-years), the incidence rate of recurrent ICH in patients with HCHWA-D was 20.9 vs 8.9 per 100 person-years in sCAA. Patients with HCHWA-D had a long-term mortality of 8.2 vs 8.4 per 100 person-years in patients with sCAA. After adjustments, patients with HCHWA-D had a higher risk of recurrent ICH (HR 2.8; 95% confidence interval 1.6-4.9; p < 0.001) and a higher long-term mortality (HR 2.8; 95% confidence interval 1.5-5.2; p = 0.001)., Conclusions: Patients with HCHWA-D have worse long-term prognosis after a first ICH than patients with sCAA. The absence of cardiovascular risk factors in most patients with HCHWA-D suggests that vascular amyloid is responsible for the recurrent hemorrhages. HCHWA-D is therefore a pure form of cerebral amyloid angiopathy with an accelerated clinical course and provides a good model to study the pathophysiology and future therapeutic interventions of amyloid-related hemorrhages., (© 2016 American Academy of Neurology.)