Cerebral amyloid angiopathy in East and West

Prevalence of Cerebral Amyloid Angiopathy Pathology and Strictly Lobar Microbleeds in East-Asian Versus Western Populations: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Possible differences in the prevalence of cerebral amyloid angiopathy (CAA) in East-Asian compared to Western populations have received little attention, and results so far have been ambiguous. Our aim is to compare the prevalence of CAA neuropathology and magnetic resonance imaging markers of CAA in East-Asian and Western cohorts reflecting the general population, cognitively normal elderly, patients with Alzheimer's disease (AD), and patients with (lobar) intracerebral hemorrhage (ICH).

METHODS

We performed a systematic literature search in PubMed and Embase for original research papers on the prevalence of CAA and imaging markers of CAA published up until February 17th 2022. Records were screened by two independent reviewers. Pooled estimates were determined using random-effects models. We compared studies from Japan, China, Taiwan, South Korea (East-Asian cohorts) to studies from Europe or North America (Western cohorts) by meta-regression models.

RESULTS

We identified 12,257 unique records, and we included 143 studies on Western study populations and 53 studies on East-Asian study populations. Prevalence of CAA neuropathology did not differ between East-Asian and Western cohorts in any of the investigated patient domains. The prevalence of strictly lobar microbleeds was lower in East-Asian cohorts of population-based individuals (5.6% vs. 11.4%, P=0.020), cognitively normal elderly (2.6% vs. 11.4%, P=0.001), and patients with ICH (10.2% vs. 24.6%, P<0.0001). However, age was in general lower in the East-Asian cohorts.

CONCLUSION

The prevalence of CAA neuropathology in the general population, cognitively normal elderly, patients with AD, and patients with (lobar) ICH is similar in East-Asian and Western countries. In East-Asian cohorts reflecting the general population, cognitively normal elderly, and patients with ICH, strictly lobar microbleeds were less prevalent, likely due to their younger age. Consideration of potential presence of CAA is warranted in decisions regarding antithrombotic treatment and potential new anti-amyloid-β immunotherapy as treatment for AD in East-Asian and Western countries alike.

Underlying microangiopathy and functional outcome of simultaneous multiple intracerebral hemorrhage

Objective

To identify the predominant type of cerebral small vessel disease (SVD) and outcomes in patients with simultaneous multiple intracerebral hemorrhages (SMICH).

Methods

Consecutive patients with intracerebral hemorrhage (ICH) from a single-center prospective cohort were retrospectively reviewed. Presumed etiology was classified according to the SMASH-U criteria. Demographics, clinical and laboratory variables, and neuroimaging data were compared between patients with primary SMICH and those with single ICH. Functional outcomes were assessed using the modified Rankin scale 90 days after ICH.

Results

Of the 598 enrolled patients, 37 (6.2%) met the criteria for SMICH. Risk factors for SMICH included a high burden of deep cerebral microbleeds (CMBs) (odds ratio [OR] 1.06, 95% confidence interval [CI], 1.00–1.12; p = 0.040), white matter hyperintensity scores (OR 1.27, 95% CI 1.04–1.57; p = 0.021), history of ICH (OR 3.38, 95% CI 1.31–8.05; p = 0.008), and low serum magnesium levels (OR 0.01, 95% CI 0.00–0.25; p = 0.007). Based on the SMASH-U classification, 15(40.5%) SMICH were classified as hypertension, whereas 17 (45.9%) as undetermined-etiology. To further explore the potential microangiopathy underlying undetermined-SMICH, these patients with undetermined-etiology were compared to those with cerebral amyloid angiopathy-ICH, and were associated with a higher burden of deep CMBs but less severe centrum semiovale enlarged perivascular spaces. Likewise, compared with hypertension-ICH patients, those with undetermined SMICH were consistently associated with a higher deep CMB counts. Moreover, multivariate analysis revealed that SMICH was independently associated with poor outcomes (OR 2.23, 95%CI 1.03–4.76; p = 0.038).

Conclusion

Our results suggest that most patients with primary SMICH harbor hypertensive-SVD as principal angiopathy. Patients with SMICH are at a high risk of poor outcomes. (ClinicalTrials.gov Identifier: NCT 04803292).

Microbleeds, Cerebral Hemorrhage, and Functional Outcome After Endovascular Thrombectomy

OBJECTIVE

To determine whether pretreatment cerebral microbleeds (CMBs) presence and burden are correlated with an increased risk of intracranial hemorrhage (ICH) or poor functional outcome following endovascular thrombectomy (EVT) for acute ischemic stroke (AIS).

METHODS

Consecutive patients treated by EVT for anterior circulation AIS were retrospectively analyzed. Experienced neuroradiologists blinded to functional outcomes rated CMBs on T2*-MRI using a validated scale. We investigated associations of CMB presence and burden with ICH and poor clinical outcome at 3 months (modified Rankin Scale score >2).

RESULTS

Among 513 patients, 281 (54.8%) had a poor outcome and 89 (17.3%) had ≥1 CMBs. A total of 190 (37%) patients experienced ICH; 66 (12.9%) were symptomatic. CMB burden was associated with poor outcome in a univariable analysis (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.03-1.36 per 1-CMB increase; p = 0.02), but significance was lost after adjustment for sex, age, stroke severity, hypertension, diabetes mellitus, atrial fibrillation, prior antithrombotic medication, IV thrombolysis, and reperfusion status (OR, 1.05; 95% CI, 0.92-1.20 per 1-CMB increase; p = 0.50). Results remained nonsignificant when taking into account CMB location or presumed underlying pathogenesis. CMB presence, burden, location, or presumed pathogenesis were not independently correlated with ICH.

CONCLUSIONS

Poor functional outcome or ICH were not correlated with CMB presence or burden on pre-EVT MRI after adjustment for confounding factors. Excluding such patients from reperfusion therapies is unwarranted.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with AIS undergoing EVT, after adjustment for confounding factors, the presence of CMBs is not significantly associated with clinical outcome or the risk of ICH.

Proportion of intracerebral haemorrhage due to cerebral amyloid angiopathy in the East and West: Comparison between single hospital centres in Japan and the United Kingdom

PURPOSE

We investigated whether the proportion of intracerebral haemorrhage (ICH) due to cerebral amyloid angiopathy (CAA) differs between patients admitted to hospitals in the East and the West.

METHODS

This international cross-sectional study included consecutive spontaneous ICH patients admitted to one stroke centre in the United Kingdom (Western centre origin) and one in Japan (Eastern centre origin) during the same period. We classified spontaneous ICH into "CAA-related" or "other" using the Edinburgh CT-based diagnostic criteria. We used multivariable logistic regression analyses to assess the relationship between CAA-related ICH and geographical location or ethnicity (White vs. East Asian or other ethnicities). Sensitivity analyses were performed using the modified Boston MRI-based diagnostic criteria for CAA-related ICH.

RESULTS

Of 433 patients (median age, 72 years; Western centre origin, 55%), 15% were classified as CAA-related ICH. In the multivariable logistic regression model, Eastern centre and ethnicity had a lower proportion of CAA-related ICH (odds ratio [OR] vs Western centre origin 0.55, 95%CI 0.31-0.98; OR [vs. White] 0.47, 95%CI 0.25-0.87); these findings remained robust in sensitivity analyses. The estimated incidence of "other" (non-CAA) ICH (attributed to hypertensive arteriopathy) was 2.5-fold higher in East Asian populations.

CONCLUSIONS

The proportion CAA-related ICH is lower in an Eastern compared to a Western hospital ICH population; this might be explained by a higher incidence of ICH related to hypertensive arteriopathy in East Asian populations, suggesting that optimal ICH prevention strategies might differ between the East and West.

Flexible multidentate benzyldiamine derivatives with high affinity for β-amyloid in cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) commonly found in the aged is pathologically characterized by β-amyloid (Aβ) deposition in the walls of arteries and capillaries of brain. In this study, four flexible multidentate benzyldiamine derivatives as potential probes for cerebrovascular Aβ deposition were designed and synthesized. In in vitro inhibition assays, the ligands 18-21 displayed high affinities for Aβ aggregates with K_i values of 1.45 ± 0.53 nM, 1.68 ± 0.35 nM, 1.16 ± 0.23 nM and 1.72 ± 0.19 nM, respectively. A significant improvement in the binding affinity over the monomer, compounds 9-12 or benzyldiamine derivatives, demonstrated the applicability of the multidentate approach. The underlying mechanism of these novel Aβ agents was explored by molecular docking technique, which theoretically verified the high affinities of the multidentate benzyldiamine derivatives for Aβ aggregates. Moreover, the molecular masses of the ligands 18-21 are more than 700 Dalton, which are believed to be hardly capable of penetrating blood brain barrier. In this regard, these ligands could be used to distinguish CAA from Alzheimer's disease which is another Aβ-related disorder disease. To convert these ligands to positron emission tomography imaging agents, we attempted to radiosynthesize [¹⁸F]18. Though the radiolabeling was not very successful, the preliminary results suggested that these newly proposed multidentate benzyldiamine derivatives may be used as potential Aβ imaging agents in cerebral amyloid angiopathy.

Cortical Microinfarcts on 3T Magnetic Resonance Imaging in Cerebral Amyloid Angiopathy

Background and Purpose- Cerebral microinfarcts are small ischemic lesions that are found in cerebral amyloid angiopathy (CAA) patients at autopsy. The current study aimed to detect cortical microinfarcts (CMI) on in vivo 3 Tesla (3T) magnetic resonance imaging (MRI) in CAA patients, to study the progression of CMI over a 1-year period, and to correlate CMI with markers of CAA-related vascular brain injury and cognitive functioning. Methods- Thirty-five CAA patients (mean age, 74.2±7.6 years), 13 Alzheimer disease (AD) patients (67.0±5.8 years), and 26 healthy controls (67.2±9.5 years) participated in the study. All participants underwent a standardized clinical and neuropsychological assessment as well as 3T MRI. CMI were rated according to standardized criteria. Results- CMI were present in significantly more CAA patients (57.1%; median number: 1, range 1-9) than in Alzheimer disease (7.7%) or in healthy controls (11.5%; P<0.001). Incident CMI were observed after a 1-year follow-up. CMI did not correlate with any other MRI marker of CAA nor with cognitive function. Conclusions- In vivo CMI are a frequent finding on 3T MRI in CAA patients, and incident CMI are observable after 1-year follow-up. CMI can be regarded as a new MRI marker of CAA, potentially distinct from other well-established markers. Future larger cohort studies with longitudinal follow-up are needed to elucidate the relationship between CMI and possible causes and clinical outcomes in CAA.

Frequency of Intracranial Hemorrhage With Low-Dose Aspirin in Individuals Without Symptomatic Cardiovascular Disease: A Systematic Review and Meta-analysis

Importance

Use of low-dose aspirin for the primary prevention of cardiovascular events remains controversial because increased risk of bleeding may offset the overall benefit. Among major bleeding events, intracranial hemorrhage is associated with high mortality rates and functional dependency.

Objective

To assess the risk of intracranial hemorrhage associated with low-dose aspirin among individuals without symptomatic cardiovascular disease.

Data Sources

PubMed, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov were searched from January 1966 to October 30, 2018.

Study Selection

Randomized clinical trials that compared low-dose aspirin (daily dose ≤100 mg) vs control and recorded the end points of intracranial hemorrhage separately for active treatment and control groups were included.

Data Extraction and Synthesis

A random-effect estimate was computed based on the Mantel-Haenszel method. Relative risk with 95% CI was used as a measure of aspirin vs control on risk of intracranial hemorrhage.

Main Outcomes and Measures

The main outcomes were any intracranial hemorrhage, intracerebral hemorrhage, subdural or extradural hemorrhage, and subarachnoid hemorrhage, for aspirin vs control.

Results

The search identified 13 randomized clinical trials of low-dose aspirin use for primary prevention, enrolling 134 446 patients. Pooling the results from the random-effects model showed that low-dose aspirin, compared with control, was associated with an increased risk of any intracranial bleeding (8 trials; relative risk, 1.37; 95% CI, 1.13-1.66; 2 additional intracranial hemorrhages in 1000 people), with potentially the greatest relative risk increase for subdural or extradural hemorrhage (4 trials; relative risk, 1.53; 95% CI, 1.08-2.18) and less for intracerebral hemorrhage and subarachnoid hemorrhage. Patient baseline features associated with heightened risk of intracerebral hemorrhage with low-dose aspirin, compared with control, were Asian race/ethnicity and low body mass index.

Conclusions and Relevance

Among people without symptomatic cardiovascular disease, use of low-dose aspirin was associated with an overall increased risk of intracranial hemorrhage, and heightened risk of intracerebral hemorrhage for those of Asian race/ethnicity or people with a low body mass index.

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.

Al18F-NODA Benzothiazole Derivatives as Imaging Agents for Cerebrovascular Amyloid in Cerebral Amyloid Angiopathy

In this study, we synthesized four novel Al^18/19F-labeled 2-phenylbenzothiazole derivatives conjugated to 1,4,7-triazacyclononane-1,4-diacetic acid via alkyl linkers and evaluated them as imaging agent targets to amyloid-β (Aβ) plaques deposited in the blood vessels of cerebral amyloid angiopathy (CAA) brain. The four ligands exhibited moderate-to-high binding ability to Aβ_1-42 aggregates, of which complex 17 possessing the most potent affinity (K _i = 11.3 nM) was selected for further biological evaluations. In vitro fluorescent staining and in vitro autoradiography studies on brain sections from CAA patients proved that this ligand could label Aβ deposits in blood vessels selectively. In biodistribution study, [¹⁸F]17 can hardly penetrate the blood-brain barrier (brain_2 min = 0.3% ID/g) and displayed a rapid blood washout rate (blood_2 min/blood_60 min = 25.2), which is favorable as CAA imaging agents. In conclusion, this Al¹⁸F-labeled 2-phenylbenzothiazole complex was developed and proved to be a promising CAA positron emission tomography agent.

Total Small Vessel Disease Score in Neurologically Healthy Japanese Adults in the Kashima Scan Study

Objective We explored the association between the total small vessel disease (SVD) score obtained with magnetic resonance imaging and risk factors and outcomes in the Japanese population. Methods The presence of SVD features, including lacunes, cerebral microbleeds, white matter changes, and basal ganglia perivascular spaces on MRI, was summed to obtain a "total SVD score" (range 0-4). Ordinal and multinomial logistic regression analyses were performed to investigate the association of higher total SVD scores with vascular risk factors, the Mini-Mental State Examination (MMSE) score, and cerebral atrophy. Results We included 1,451 neurologically healthy adults (mean age, 57.1 years; 47% male). A multivariate ordinal logistic regression analysis showed that the total SVD score was associated with aging, hypertension, blood pressure (BP), diabetes mellitus, MMSE score, and deep cerebral atrophy, but the equal slopes assumption between scores did not hold. A multivariate multinomial logistic regression analysis (total SVD score 0=reference) showed that aging, hypertension, and BP were positively associated with scores of 1, 2, or ≥3. These effects, presented as odds ratios (ORs), increased as the score increased and were strongest with a score of ≥3 [aging (per 10-year increment), OR 4.00, 95% confidence interval (CI) 2.47-6.46; hypertension, OR 5.68, 95% CI 2.52-12.80; systolic BP (per standard deviation increase), OR 1.96, 95% CI 1.41-2.74, respectively]. Diabetes mellitus and deep cerebral atrophy tended to be associated with the SVD scores. The MMSE score showed no consistent associations. Conclusion The total SVD score may be a promising tool for indexing SVD, even in the Japanese population.

Brain hemorrhage recurrence, small vessel disease type, and cerebral microbleeds: A meta-analysis

OBJECTIVE

We evaluated recurrent intracerebral hemorrhage (ICH) risk in ICH survivors, stratified by the presence, distribution, and number of cerebral microbleeds (CMBs) on MRI (i.e., the presumed causal underlying small vessel disease and its severity).

METHODS

This was a meta-analysis of prospective cohorts following ICH, with blood-sensitive brain MRI soon after ICH. We estimated annualized recurrent symptomatic ICH rates for each study and compared pooled odds ratios (ORs) of recurrent ICH by CMB presence/absence and presumed etiology based on CMB distribution (strictly lobar CMBs related to probable or possible cerebral amyloid angiopathy [CAA] vs non-CAA) and burden (1, 2-4, 5-10, and >10 CMBs), using random effects models.

RESULTS

We pooled data from 10 studies including 1,306 patients: 325 with CAA-related and 981 CAA-unrelated ICH. The annual recurrent ICH risk was higher in CAA-related ICH vs CAA-unrelated ICH (7.4%, 95% confidence interval [CI] 3.2-12.6 vs 1.1%, 95% CI 0.5-1.7 per year, respectively; p = 0.01). In CAA-related ICH, multiple baseline CMBs (versus none) were associated with ICH recurrence during follow-up (range 1-3 years): OR 3.1 (95% CI 1.4-6.8; p = 0.006), 4.3 (95% CI 1.8-10.3; p = 0.001), and 3.4 (95% CI 1.4-8.3; p = 0.007) for 2-4, 5-10, and >10 CMBs, respectively. In CAA-unrelated ICH, only >10 CMBs (versus none) were associated with recurrent ICH (OR 5.6, 95% CI 2.1-15; p = 0.001). The presence of 1 CMB (versus none) was not associated with recurrent ICH in CAA-related or CAA-unrelated cohorts.

CONCLUSIONS

CMB burden and distribution on MRI identify subgroups of ICH survivors with higher ICH recurrence risk, which may help to predict ICH prognosis with relevance for clinical practice and treatment trials.

Serum Lipid Fractions and Cerebral Microbleeds in a Healthy Japanese Population

Background: Cerebral microbleeds (CMBs) are associated with focal hemosiderin deposits and represent a form of cerebral small vessel disease. To date, indefinite and inconsistent reports are available regarding the association between serum lipid fractions and CMBs. In addition, these previous studies did not include Asian populations, who may have a higher risk of cerebral hemorrhage. The purpose of this study was to examine the associations between serum lipid fractions and CMBs in healthy Japanese subjects. Methods: We performed a cross-sectional study involving 4,024 neurologically normal Japanese subjects (mean age 61.6 years). All the participants underwent 1.5-Tesla magnetic resonance imaging scan, and CMBs were classified into 3 groups based on their locations. The concentrations of lipid fractions were categorized into quartiles and the association between the lipid fractions and CMBs were investigated using logistic regression analysis. Results: CMBs were observed in 164 (4.1%) of participants. Of these participants with CMBs, 33 (20.1%) had lobar CMBs and 91 (55.5%) had deep CMBs. Subjects with deep CMBs had lower total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels. After adjusting for confounding factors, lower TC and HDL-C levels were still associated with the presence of deep CMBs (OR for the highest vs. the lowest quartiles of TC and HDL-C was 2.28 [95% CI 1.05-4.94], and 1.93 [95% CI 1.02-3.65], respectively). The presence of subcortical infarcts and periventricular hyperintensities was more frequently observed in deep CMBs, whereas white matter hyperintensities were more frequently observed in lobar CMBs. Conclusions: Our results suggest that low serum TC and HDL-C levels are closely associated with deep CMBs.

Cerebral microbleeds and white matter hyperintensities in cardioembolic stroke patients due to atrial fibrillation: single-centre longitudinal study

Cerebral microbleeds (CMBs) are a potential predictor of future stroke risk with clinical relevance for antithrombotic treatments, especially in ischaemic stroke patients with atrial fibrillation. However, prospective data on CMBs and risk of stroke in this particular stroke population remain scarce. We therefore performed a single centre longitudinal study to investigate CMBs and white matter hyperintensities (WMH) and the risk of future stroke. Consecutive acute stroke patients, admitted during 2008-2012 for presumed cardioembolic stroke due to non-valvular atrial fibrillation with available follow-up for the occurrence of recurrent stroke were included in our study. The rate of future stroke between patients with vs. without CMBs and moderate to severe WMH at baseline MRI was compared in separate survival and multivariable Cox regression analyses. A total of 119 cardioembolic stroke patients (49% female, median age: 76; IQR: 68-82years) were included. CMBs were found at baseline in 26/119 (21.8%; 95% CI: 14.8-30.4%) patients. Moderate to severe WMH were present in 27/119 (22.7%; 95% CI: 15.5-31.3%) cases. During a median follow-up time of 17months (IQR: 3-50months), 17 of 119 patients experienced a symptomatic stroke: 14 patients had an ischaemic stoke and 3 had intracerebral haemorrhage. The overall incidence rate for ischaemic stroke and intracerebral haemorrhage was 4.2 (95% CI: 2.3-7.1) and 0.9 (95% CI: 0.5-2.6) per 1000 patient-year of follow-up respectively. In multivariable Cox regression analysis the hazard ratio for total CMB number and the risk of stroke during follow-up was 1.05 (95% CI: 0.99-1.11; p=0.137, per each additional CMB increase), after adjusting for CHAD2S. A similar regression analysis demonstrated that moderate to severe WMHs were independently associated with increased risk of symptomatic stroke at follow-up, after adjusting for CHAD2S (HR: 2.99; 95% CI: 1.01-8.30; p=0.036). Despite the small sample size, our study provides useful data to guide power calculations and likely effect sizes relevant for ongoing and future larger studies and clinical trials.

Comparing Risk Factor Profiles between Intracerebral Hemorrhage and Ischemic Stroke in Chinese and White Populations: Systematic Review and Meta-Analysis

BACKGROUND

Chinese populations have a higher proportion of intracerebral hemorrhage (ICH) in total strokes. However, the reasons are not fully understood.

METHODS

To assess the differences in frequency of major risk factors between ICH and ischemic stroke (IS) in Chinese versus white populations of European descent, we systematically sought studies conducted since 1990 that compared frequency of risk factors between ICH and IS in Chinese or white populations. For each risk factor, in Chinese and Whites separately, we calculated study-specific and random effects pooled prevalence and odds ratios (ORs) for ICH versus IS.

RESULTS

Six studies among 36,190 Chinese, and seven among 52,100 white stroke patients studied hypertension, diabetes, atrial fibrillation (AF), ischemic heart disease (IHD), hypercholesterolemia, smoking and alcohol. Pooled prevalence of AF was significantly lower in Chinese. Pooled ORs for ICH versus IS were mostly similar in Chinese and Whites. However, in Chinese--but not Whites--mean age was lower (62 versus 69 years), while hypertension and alcohol were significantly more frequent in ICH than IS (ORs 1.38, 95% CI 1.18-1.62, and 1.46, 1.12-1.91). Hypercholesterolemia and smoking were significantly less frequent in ICH in Whites, but not Chinese, while IHD, AF and diabetes were less frequent in ICH in both.

CONCLUSIONS

Different risk factor distributions in ICH and IS raise interesting possibilities about variation in mechanisms underlying the different distributions of pathological types of stroke between Chinese and Whites. Further analyses in large, prospective studies, including adjustment for potential confounders, are needed to consolidate and extend these findings.

The APOE4 allele shows opposite sex bias in microbleeds and Alzheimer's disease of humans and mice

The apolipoprotein APOE4 allele confers greater risk of Alzheimer's disease (AD) for women than men, in conjunction with greater clinical deficits per unit of AD neuropathology (plaques, tangles). Cerebral microbleeds, which contribute to cognitive dysfunctions during AD, also show APOE4 excess, but sex-APOE allele interactions are not described. We report that elderly men diagnosed for mild cognitive impairment and AD showed a higher risk of cerebral cortex microbleeds with APOE4 allele dose effect in 2 clinical cohorts (ADNI and KIDS). Sex-APOE interactions were further analyzed in EFAD mice carrying human APOE alleles and familial AD genes (5XFAD (+/-) /human APOE(+/+)). At 7 months, E4FAD mice had cerebral cortex microbleeds with female excess, in contrast to humans. Cerebral amyloid angiopathy, plaques, and soluble Aβ also showed female excess. Both the cerebral microbleeds and cerebral amyloid angiopathy increased in proportion to individual Aβ load. In humans, the opposite sex bias of APOE4 allele for microbleeds versus the plaques and tangles is the first example of organ-specific, sex-linked APOE allele effects, and further shows AD as a uniquely human condition.

Cerebral Microbleeds Are Associated With an Increased Risk of Stroke: The Rotterdam Study

BACKGROUND

Cerebral microbleeds are highly prevalent in people with clinically manifest cerebrovascular disease and have been shown to increase the risk of stroke recurrence. Microbleeds are also frequently found in healthy elderly, a population in which the clinical implication of microbleeds is unknown.

METHODS AND RESULTS

In the population-based Rotterdam Study, the presence, number, and location of microbleeds were assessed at baseline on brain MRI of 4759 participants aged ≥45 years. Participants were followed for incident stroke throughout the study period (2005-2013). We used Cox proportional hazards to investigate if people with microbleeds were at increased risk of stroke in comparison with those without microbleeds, adjusting for demographic, genetic, and cardiovascular risk, and cerebrovascular imaging markers. Microbleed prevalence was 18.7% (median count 1 [1-111]). During mean follow-up of 4.9 years (standard deviation, 1.6) 93 strokes occurred (72 ischemic, 11 hemorrhagic, and 10 unspecified). Microbleed presence was associated with an increased risk of all strokes (hazard ratio, 1.93; 95% confidence interval, 1.25-2.99). The risk increased with greater microbleed count. In comparison with those without microbleeds, participants with microbleeds in locations suggestive of cerebral amyloid angiopathy (lobar with or without cerebellar microbleeds) were at increased risk of intracerebral hemorrhage (hazard ratio, 5.27; 95% confidence interval, 1.38-20.23). Microbleeds at other locations were associated with an increased risk of both ischemic stroke and intracerebral hemorrhage.

CONCLUSIONS

Microbleeds on MRI are associated with an increased risk of stroke in the general population. Our results strengthen the notion that microbleeds mark progression of cerebrovascular pathology and represent a precursor of stroke.

99mTc(CO)3-Labeled Benzothiazole Derivatives Preferentially Bind Cerebrovascular Amyloid: Potential Use as Imaging Agents for Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a disorder affecting the elderly that is characterized by amyloid-β (Aβ) deposition in blood vessel walls of the brain. A series of 99mTc(CO)3-labeled benzothiazole derivatives as potential SPECT imaging probes for cerebrovascular Aβ deposition is reported. Rhenium surrogate displayed high affinities to Aβ aggregates with Ki values ranging from 106 to 42 nM, and they strongly stained Aβ deposits in transgenic mice (Tg) and Alzheimer's disease (AD) patients. In vitro autoradiography on brain sections of Tg and AD patients confirmed that [99mTc]24 possessed sufficient affinity for Aβ plaques, and [99mTc]24 could only label Aβ deposition in blood vessels but not Aβ plaques in the parenchyma of the brain of AD patients. Moreover, [99mTc]24 possessed favorable initial uptake (1.21% ID/g) and fast blood washout (blood2 min/blood60 min=23) in normal mice. These preliminary results suggest that [99mTc]24 may be used as an Aβ imaging probe for the detection of CAA.

Genetics of cerebral amyloid angiopathy: systematic review and meta-analysis

BACKGROUND AND PURPOSE

Cerebral amyloid angiopathy (CAA) is common in the ageing brain and is associated with dementia and lobar intracerebral haemorrhage. We systematically reviewed genetic associations with CAA to better understand its pathogenesis.

METHODS

We comprehensively sought and critically appraised published studies of associations between any genetic polymorphism and histopathologically confirmed CAA. We assessed the effects of genotype by calculating study specific and pooled odds ratios (ORs) in meta-analyses, and assessed small study bias.

RESULTS

58 studies (6855 participants) investigated apolipoprotein E (APOE) genotype and sporadic CAA. Meta-analysis of 24 (3520 participants) of these showed an association of APOE ε4 with CAA (ε4 present vs absent, pooled OR 2.7, 95% CI 2.3 to 3.1, p<0.00001), which was dose dependent, robust to potential small study biases and occurred irrespective of dementia status. There was no significant association between APOE ε2 and CAA. Among 24 studies (4703 participants) of other genetic polymorphisms, there was preliminary evidence of an association with CAA of polymorphisms in the transforming growth factor β1 gene (two studies, 449 participants), translocase of outer mitochondrial membrane 40 gene (one study, 723 participants) and the complement component receptor 1 gene (one study, 544 participants). There were insufficient data to draw conclusions from 24 studies (∼200 participants) of APOE and hereditary CAA or familial Alzheimer's disease.

CONCLUSIONS

There is convincing evidence for a dose dependent association between APOE ε4 and sporadic CAA. Further work is needed to better understand the mechanism of this association and to further investigate other genetic associations with CAA.