Dynamic temporal change of cerebral microbleeds: long-term follow-up MRI study

Relationship between radiation dose and cerebral microbleed formation in dogs with intracranial tumors

BACKGROUND

Cerebral microbleeds (CMBs) are a possible sequela in human brain tumor patients treated with radiation therapy (RT). No such association is reported in dogs.

OBJECTIVES

To investigate whether CMBs occur in dogs after radiotherapy, and if there is an association between number and dose, and an increase over time.

ANIMALS

Thirty-four client-owned dogs irradiated for primary intracranial neoplasia. ≥2 magnetic resonance imaging (MRI) scans including susceptibility-weighted imaging (SWI) were required.

METHODS

Retrospective, observational, single-center study. Cerebral microbleeds identified on 3 T SWI were counted within the entire brain, and within low- (<20 Gy), intermediate- (20-30 Gy), and high- (>30 Gy) dose regions. A generalized linear mixed-effects model was used to analyze the relationship between the CMBs count and the predictor variables (irradiation dose, time after treatment).

RESULTS

Median follow-up time was 12.6 months (range, 1.8-37.6 months). Eighty-three MR scans were performed. In 4/15 dogs (27%, 95% CI, 10%-52%) CMBs were present at baseline. ≥1 CMBs after RT were identified in 21/34 dogs (62%, 95% CI, 45%-77%). With each month, the number of CMBs increased by 14% (95% CI, 11%-16%; P < .001). The odds of developing CMBs in the high-dose region are 4.7 times (95% CI, 3.9-5.6; P < .001) greater compared with the low-dose region.

CONCLUSION AND CLINICAL IMPORTANCE

RT is 1 possible cause of CMBs formation in dogs. Cerebral microbleeds are most likely to occur in the peritumoral high-dose volume, to be chronic, and to increase in number over time. Their clinical relevance remains unknown.

Cerebral microbleeds is a predictor of recurrent small vessel cerebrovascular disease: Evaluation based on the recurrent stroke pattern

OBJECTIVES

An increased number of cerebral microbleeds (CMBs) is considered a predictive factor for recurrent small vessel cerebrovascular diseases, including lacunar infarction and non-lobar intracerebral hemorrhage (ICH). However, it is unclear which recurrent stroke pattern is mainly reflected in the number of CMBs.

MATERIALS AND METHODS

This study enrolled 217 patients with their first stroke (148 deep lacunar infarctions and 69 non-lobar ICHs), between January 2009 and March 2015. The numbers of baseline and newly appearing CMBs in patients with recurrent stroke were compared with those in patients with non-recurrent stroke, and the dynamics of the number of CMBs was evaluated according to recurrent stroke patterns.

RESULTS

Fifty-nine patients with recurrent stroke were included in this study. A larger number of baseline and newly appearing CMBs was significantly associated with recurrent stroke (p = 0.04, p < 0.001, respectively). Recurrent stroke patterns were divided into four types: deep lacunar infarction/deep lacunar infarction (37 patients), deep lacunar infarction/non-lobar ICH (eight patients), non-lobar ICH/deep lacunar infarction (eight patients), and non-lobar ICH/non-lobar ICH (six patients). The number of newly appearing CMBs was significantly higher in patients with deep lacunar infarction/non-lobar ICH than in those with other recurrent stroke patterns (p = 0.04).

CONCLUSIONS

The number of CMBs is associated with recurrent stroke, including deep lacunar infarction and non-lobar ICH, and differs depending on the recurrent stroke patterns. The increase in the number of CMBs was strongly correlated with the deep lacunar infarction/non-lobar ICH recurrence pattern.

Association of statin use and lipid levels with cerebral microbleeds and intracranial hemorrhage in patients with atrial fibrillation: A prospective cohort study

BACKGROUND

An increased risk of intracranial hemorrhage (ICH) associated with statins has been reported, but data on the relationship between statin use and cerebral microbleeds (CMBs) in patients with atrial fibrillation (AF), a population at high bleeding and cardiovascular risk, are lacking.

AIMS

To explore the association between statin use and blood lipid levels with the prevalence and progression of CMBs in patients with AF with a particular focus on anticoagulated patients.

METHODS

Data of Swiss-AF, a prospective cohort of patients with established AF, were analyzed. Statin use was assessed during baseline and throughout follow-up. Lipid values were measured at baseline. CMBs were assessed using magnetic resonance imagining (MRI) at baseline and at 2 years follow-up. Imaging data were centrally assessed by blinded investigators. Associations of statin use and low-density lipoprotein (LDL) levels with CMB prevalence at baseline or CMB progression (at least one additional or new CMB on follow-up MRI at 2 years compared with baseline) were assessed using logistic regression models; the association with ICH was assessed using flexible parametric survival models. Models were adjusted for hypertension, smoking, body mass index, diabetes, stroke/transient ischemic attack, coronary heart disease, antiplatelet use, anticoagulant use, and education.

RESULTS

Of the 1693 patients with CMB data at baseline MRI (mean ± SD age 72.5 ± 8.4 years, 27.6% women, 90.1% on oral anticoagulants), 802 patients (47.4%) were statin users. The multivariable adjusted odds ratio (adjOR) for CMBs prevalence at baseline for statin users was 1.10 (95% CI = 0.83-1.45). AdjOR for 1 unit increase in LDL levels was 0.95 (95% CI = 0.82-1.10). At 2 years, 1188 patients had follow-up MRI. CMBs progression was observed in 44 (8.0%) statin users and 47 (7.4%) non-statin users. Of these patients, 64 (70.3%) developed a single new CMB, 14 (15.4%) developed 2 CMBs, and 13 developed more than 3 CMBs. The multivariable adjOR for statin users was 1.09 (95% CI = 0.66-1.80). There was no association between LDL levels and CMB progression (adjOR 1.02, 95% CI = 0.79-1.32). At follow-up 14 (1.2%) statin users had ICH versus 16 (1.3%) non-users. The age and sex adjusted hazard ratio (adjHR) was 0.75 (95% CI = 0.36-1.55). The results remained robust in sensitivity analyses excluding participants without anticoagulants.

CONCLUSIONS

In this prospective cohort of patients with AF, a population at increased hemorrhagic risk due to anticoagulation, the use of statins was not associated with an increased risk of CMBs.

Low-density lipoprotein cholesterol, statin therapy, and cerebral microbleeds: The CIRCLE study

BACKGROUND

Current evidence suggests a potential association between cerebral microbleeds (CMBs), low-density lipoprotein cholesterol (LDL-C) levels, and statin use, but the exact relationship remains unclear. This study aims to prospectively examine these relationships in a stroke-free population.

METHODS

From January 2010 to January 2020, we enrolled stroke-free individuals with at least one cerebral small vessel disease imaging marker from the CIRCLE study (ClinicalTrials.gov ID: NCT03542734). Participants underwent baseline and 1-year follow-up susceptibility-weighted imaging (SWI), and baseline LDL-C testing. New CMBs were categorized as strictly lobar and deep CMBs based on location.

RESULTS

A total of 209 individuals were included. Baseline serum LDL-C levels were divided into quartiles: Q1 (≤1.76 mmol/L), Q2 (1.77-2.36 mmol/L), Q3 (2.37-2.93 mmol/L), and Q4 (>2.93 mmol/L). The incidence of new deep CMBs was 30.0%, 11.1%, 10.9%, 8.2% in Q1, Q2, Q3, Q4, respectively. Multivariate logistic model revealed that only LDL-C in Q1 was associated with increased incidence of new deep CMBs (OR = 4.256; 95% CI: 1.156-15.666; p = 0.029). In a subset of 169 participants without prior statin use, the use of atorvastatin was associated with reduced occurrence of new deep CMBs (OR = 0.181; 95% CI: 0.035-0.928; p = 0.040), while it was not found with rosuvastatin (OR = 0.808; 95% CI: 0.174-3.741; p = 0.785).

CONCLUSIONS

While lower LDL-C levels were associated with higher CMB development, statin therapy did not increase the risk of new CMBs. Atorvastatin even demonstrated a protective effect.

Gender heterogeneity in the influencing factors for cerebral microbleeds in acute ischemic stroke patients

BACKGROUND

Cerebral microbleeds (CMBs) are common in acute ischemic stroke (AIS) patients. The presence of CMBs increases the risk of hemorrhagic transformation in AIS patients, and it is also closely associated with cognitive decline and even dementia. At present, there exist different opinions on the independent risk factors for CMBs, and there is no consensus on whether there are gender differences in -post-stroke CMB. Therefore, this study sought to investigate gender heterogeneity in the influencing factors for CMBs by studying male and female AIS patients.

METHODS

This was a China-based, Single-center, retrospective review of data from 482 AIS inpatients at the Neurology Department of Hebei General Hospital (NCT05882123). Both demographic and clinical data were collected from the study subjects. Different head magnetic resonance imaging sequences were used to assess the subjects' CMBs, white matter lesions, and old lacunar infarcts (LI). Various statistical methods, including the t-test, χ2 test, and logistic regression, were used to analyze the gender heterogeneity of the influencing factors for CMBs in AIS patients.

RESULTS

When compared with the male AIS patients, the female AIS patients were older and had higher total cholesterol, triglyceride, high-density lipoprotein, low-density lipoprotein, ApoA, ApoB, and fibrinogen levels. The female AIS patients also had higher National Institute of Health Stroke Scale scores and hypertension disease composition ratios. By contrast, the proportions of female AIS patients with a history of smoking and a history of alcohol consumption were both lower than the corresponding proportions of male AIS patients. These differences were all statistically significant (p < .05). There were no statistically significant differences in the incidence and severity of CMBs between the male and female AIS patients (χ2 ＝ 0.851, 3.092, p > .05). The univariate and multivariate stepwise logistic regression analyses confirmed that age (OR = 1.074, 95% CI: 1.013-1.139, p = .016) and old LI (OR = 4.295, 95% CI: 1.062-17.375, p = .041) were independent risk factors for comorbid CMBs in the female AIS patients, while blood glucose (OR = 0.692, 95% CI: 0.494-0.968, p = .031) was an independent protective factor for comorbid CMBs in the female AIS patients. However, these factors were not found to be independent risk or protective factors for comorbid CMBs in male AIS patients.

CONCLUSION

There are gender differences in the influencing factors for CMBs in AIS patients. Age, old LIs, and blood glucose are independent risk or protective factors for comorbid CMBs in female AIS patients, although they are not associated with the risk of developing CMBs in male AIS patients.

Association of Dilated Perivascular Spaces With Lipid Indices in Ischemic Stroke Patients

Background

Dilated perivascular spaces (dPVS) in the basal ganglia are associated with aging, vascular risk factors, and other magnetic resonance imaging (MRI) markers of cerebral small vessel disease (cSVD). While high blood lipids are a well-demonstrated risk factor for large artery atherosclerosis, their role in cSVD remains largely elusive.

Methods

We evaluated lipid profiles, cardiovascular risk factors, and brain MRI findings in patients with ischemic stroke or transient ischemic attack. We analyzed the extent of dPVS, cerebral microbleed (CMB), and cerebral white matter hyperintensities (WMHs) as MRI indices of cSVD and investigated associations of dPVS with lipid parameters and other cSVD indices.

Results

Our study enrolled 173 patients with ischemic stroke or transient ischemic attack. The mean age was 68.38±14.31 (range 35-99) years, and 57.8% (n=100) of patients were male. dPVSwere detected in 97% (n=168) of the patients. Among the whole population, half of the patients (n=87) had moderate to severe dPVS. According to the univariate analysis, age, hypertension, previous antiaggregant and/or anticoagulant use, and the high-density lipoprotein to low-density lipoprotein (HDL/LDL) ratio but not other lipid profiles, cerebral microbleed load, and cerebral white matter hyperintensities severity were found to be positively associated with dPVS number in the basal ganglia. After multivariate logistic regression analysis, only age and WMH severity remained statistically significant.

Conclusions

dPVS are closely associated with other cSVD subtypes and aging. The studied lipid indices were not independently associated with moderate to severe dPVS in basal ganglia in ischemic stroke patients. The association of each lipid and HDL/LDL ratio needs to be further studied with a larger number of participants.

Subsequent bilateral intracerebral hemorrhages in the putamen and thalamus: A report of four cases

Background:

Subsequent bilateral intracerebral hemorrhage (SBICH) in the putamen and thalamus is a rare condition. Herein, we report four such cases.

Case Description:

Case 1: A 47-year-old woman presented with the left hemiparesis and elevated blood pressure. Neuroimaging revealed a right thalamic hemorrhage and a small left thalamic hemorrhage accompanying the hyperdense rim on computed tomography (CT) and the hypointense rim on gradient-echo T2*-weighted imaging (T2*WI). Case 2: A 53-year-old man presented with a disturbance of consciousness and elevated blood pressure. Neuroimaging revealed a left putaminal hemorrhage and a small right thalamic hemorrhage that appeared hyperdense on CT and hypointense on T2*WI. Case 3: A 65-year-old woman presented with the right hemiparesis and elevated blood pressure. Neuroimaging revealed a left putaminal hemorrhage and a small right thalamic hemorrhage accompanied by a hyperdense rim on CT and a hypointense rim on T2*WI. Case 4: A 75-year-old woman presented with the right hemiparesis and elevated blood pressure. Neuroimaging revealed a left thalamic hemorrhage and small hemorrhages in the right thalamus and cerebellar hemisphere. These hemorrhages appeared hyperdense on CT and hypointense on T2*WI.

Conclusion:

SBICHs are rare bilateral hemorrhages that may present with asymptomatic microbleeds in the putamen or thalamus coupled with symptomatic, subsequent hemorrhages in the contralateral counterparts. The latter hemorrhage may develop during the subacute phase of microbleeds in the putamen or thalamus.

Association between frailty index based on routine laboratory tests and risk of cerebral small vessel disease in elderly patients: a hospital-based observational study

BACKGROUND

The association between frailty and cerebral small vessel disease (CSVD) remains controversial due to the use of different methods to assess frailty, including physical frailty phenotype and frailty scores containing measures of cognition. A frailty index based on laboratory tests (FI-Lab), which assesses frailty by the combination of routine laboratory measures and several vital signs, is independent of cognition and function status. We aimed to evaluate the association of FI-Lab with CSVD.

METHODS

An observational study was carried out in a hospitalized cohort of older patients with minor ischemic stroke or TIA. The FI-Lab was constructed by 20 routine laboratory tests, plus systolic blood pressure, diastolic blood pressure, and pulse pressure. Manifestations of CSVD including white matter hyperintensity (WMH), silent lacunar infarcts, microbleed, enlarged perivascular spaces (EPVS), as well as deep brain atrophy, were measured on magnetic resonance imaging (MRI). An ordinal score system constructed by WMH, EPVS, silent lacunar infarcts, and microbleed was used to reflect the total burden of CSVD. The associations between FI-lab and CSVD were examined by logistic regression analysis and ordinal regression.

RESULTS

A total of 398 patients were recruited from January 2016 to December 2018. The mean FI-Lab value was 0.26 ± 0.11. The prevalence of extensive periventricular WMH, extensive deep WMH, extensive basal ganglia EPVS, extensive centrum semiovale EPVS, silent lacunar infarcts, and deep microbleed was 26.1, 66.6, 68.6, 80.7, 32.9, and 6.5%, respectively. A higher FI-Lab value was associated with increased risks of extensive deep WMH (OR = 1.622; 95% CI, 1.253 ~ 2.100), extensive basal ganglia EPVS (OR = 1.535; 95% CI, 1.187 ~ 1.985), extensive centrum semiovale EPVS (OR = 1.584; 95% CI, 1.167 ~ 2.151), silent lacunar infarcts (OR = 1.273; 95% CI, 1.007 ~ 1.608), and higher total burden of CSVD. These associations remained after the adjustment of potential confounding factors.

CONCLUSION

This study demonstrated that a higher FI-Lab score might be associated with the presence of WMH, EPVS, silent lacunar infarcts, as well as severe total CSVD burden in older patients with minor stroke or TIA. The FI-Lab provides a basis for the prediction of CSVD.

Low serum lipid levels, use of statin and cerebral microbleeds: A systematic review and meta-analysis

INTRODUCTION

Previous studies have shown that low serum lipids and statins may be related to cerebral hemorrhage. We made the meta-analysis to evaluate the associations between serum lipid levels or statins treatment and cerebral microbleeds (CMBs) to identify whether the similar correlation also existed.

METHOD

We comprehensively searched the Medline, Embase, Cochrane library, Web of Science, only included English journal articles, and systematically collected the observational studies and randomized controlled trials (RCTs) from September 1975 to August 2021. Random-effects model was used to pool data. Statistical heterogeneity was assessed by I² statistic and chi-square. 11 items checklists recommended by the Agency for Healthcare Research and Quality (AHRQ), Newcastle-Ottawa Scale (NOS), and Cochrane Risk of Bias tool (ROB) were used to evaluate the methodological quality of cross-sectional studies, cohort studies and randomized controlled trial, respectively.

RESULTS

Five cohort studies, two RCTs, and ten cross-sectional studies, including 16,637 subjects and 2663 CMBs patients, were included in our quantitative synthesis. Our study found that after adjusting the covariates, total cholesterol (TC) was significantly inversely correlated with the prevalent CMBs in any location, while total triglycerides (TG) and High-density lipoprotein (HDL) were significantly inversely associated with prevalent deep CMBs. Low-density lipoprotein (LDL) was negatively associated with incident CMBs after adjusted confounders. We did not found statistical differences between statin and CMBs after adjusted covariates.

CONCLUSION

Serum major lipid (TC TG HDL LDL) levels may be inversely associated with CMBs. Currently, no sufficient evidence proves that statin therapy is the risk factor of CMBs.

Comparison of Longitudinal Changes of Cerebral Small Vessel Disease Markers and Cognitive Function Between Subcortical Vascular Mild Cognitive Impairment With and Without NOTCH3 Variant: A 5-Year Follow-Up Study

No study yet has compared the longitudinal course and prognosis between subcortical vascular cognitive impairment patients with and without genetic component. In this study, we compared the longitudinal changes in cerebral small vessel disease markers and cognitive function between subcortical vascular mild cognitive impairment (svMCI) patients with and without NOTCH3 variant [NOTCH3(+) svMCI vs. NOTCH3(-) svMCI]. We prospectively recruited patients with svMCI and screened for NOTCH3 variants by sequence analysis for mutational hotspots in the NOTCH3 gene. Patients were annually followed-up for 5 years through clinical interviews, neuropsychological tests, and brain magnetic resonance imaging. Among 63 svMCI patients, 9 (14.3%) had either known mutations or possible pathogenic variants. The linear mixed effect models showed that the NOTCH3(+) svMCI group had much greater increases in the lacune and cerebral microbleed counts than the NOTCH3(-) svMCI group. However, there were no significant differences between the two groups regarding dementia conversion rate and neuropsychological score changes over 5 years.

Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) represents a cluster of various vascular disorders with different pathological backgrounds. The advanced vasculature net of cerebral vessels, including small arteries, capillaries, arterioles and venules, is usually affected. Processes of oxidation underlie the pathology of CSVD, promoting the degenerative status of the epithelial layer. There are several classifications of cerebral small vessel diseases; some of them include diseases such as Binswanger’s disease, leukoaraiosis, cerebral microbleeds (CMBs) and lacunar strokes. This paper presents the characteristics of CSVD and the impact of the current knowledge of this topic on the diagnosis and treatment of patients.

Increases in hypertension-induced cerebral microhemorrhages exacerbate gait dysfunction in a mouse model of Alzheimer's disease

Clinical studies show that cerebral amyloid angiopathy (CAA) associated with Alzheimer's disease (AD) and arterial hypertension are independent risk factors for cerebral microhemorrhages (CMHs). To test the hypothesis that amyloid pathology and hypertension interact to promote the development of CMHs, we induced hypertension in the Tg2576 mouse model of AD and respective controls by treatment with angiotensin II (Ang II) and the NO synthesis inhibitor L-NAME. The number, size, localization, and neurological consequences (gait alterations) of CMHs were compared. We found that compared to control mice, in TG2576 mice, the same level of hypertension led to significantly increased CMH burden and exacerbation of CMH-related gait alterations. In hypertensive TG2576 mice, CMHs were predominantly located in the cerebral cortex at the cortical-subcortical boundary, mimicking the clinical picture seen in patients with CAA. Collectively, amyloid pathologies exacerbate the effects of hypertension, promoting the genesis of CMHs, which likely contribute to their deleterious effects on cognitive function. Therapeutic strategies for prevention of CMHs that reduce blood pressure and preserve microvascular integrity are expected to exert neuroprotective effects in high-risk elderly AD patients.

Contrast leakage distant from the hematoma in patients with spontaneous ICH: A 7 T MRI study

Disruption of the blood-brain barrier (BBB) might play a role in the pathophysiology of cerebral small vessel disease-related ICH. The aim of this study was to assess presence and extent of contrast agent leakage distant from the hematoma as a marker of BBB disruption in patients with spontaneous ICH. We prospectively performed 7 tesla MRI in adult patients with spontaneous ICH and assessed contrast leakage distant from the hematoma on 3D FLAIR images. Thirty-one patients were included (mean age 60 years, 29% women). Median time between ICH and MRI was 20 days (IQR 9-67 days). Seventeen patients (54%; seven lobar, nine deep, one infratentorial ICH) had contrast leakage, located cortical in 16 and cortical and deep in one patient. Patients with contrast leakage more often had lobar cerebral microbleeds (CMBs; 77%) than those without (36%; RR 2.5, 95% CI 1.1-5.7) and a higher number of lobar CMBs (patients with contrast leakage: median 2, IQR 1-8 versus those without: median 0, IQR 0-2; p = 0.02). This study shows that contrast leakage distant from the hematoma is common in days to weeks after spontaneous ICH. It is located predominantly cortical and related to lobar CMBs and therefore possibly to cerebral amyloid angiopathy.

Use of anticoagulant therapy and cerebral microbleeds: a systematic review and meta-analysis

BACKGROUND

Anticoagulant therapy increases the risk that cerebral microbleeds (CMBs) progress to intracerebral hemorrhage, but whether the therapy increases risk of CMB occurrence is unclear. We performed a systematic review and meta-analysis to investigate the potential association between anticoagulant use and CMB occurrence in stroke and stroke-free individuals.

METHODS

We searched observational studies in PubMed, Ovid EMBASE, and Cochrane Library from their inception until September 2019. We calculated the pooled odds ratio (OR) and 95% confidence interval (CI) for the prevalence and incidence of CMBs in anticoagulant users relative to non-anticoagulant users.

RESULTS

Forty-seven studies with 25,245 participants were included. The pooled analysis showed that anticoagulant use was associated with CMB prevalence (OR 1.54, 95% CI 1.26-1.88). The association was observed in subgroups stratified by type of participants: stroke-free, OR 1.86, 95% CI 1.25-2.77; ischemic stroke/transient ischemic attack, OR 1.33, 95% CI 1.06-1.67; and intracerebral hemorrhage, OR 2.26, 95% CI 1.06-4.83. Anticoagulant use was associated with increased prevalence of strictly lobar CMBs (OR 1.68, 95% CI 1.22-2.32) but not deep/infratentorial CMBs. Warfarin was associated with increased CMB prevalence (OR 1.64, 95% CI 1.23-2.18), but novel oral anticoagulants were not. Anticoagulant users showed higher incidence of CMBs during long-term follow-up (OR 1.72, 95% CI 1.22-2.44).

CONCLUSION

Anticoagulant use is associated with higher prevalence and incidence of CMBs. This association appears to depend on location of CMBs and type of anticoagulants. More longitudinal investigations with adjustment for confounders are required to establish the causality.

Effectiveness of Nonvitamin K Antagonist Oral Anticoagulants and Warfarin for Preventing Further Cerebral Microbleeds in Acute Ischemic Stroke Patients with Nonvalvular Atrial Fibrillation and At Least One Microbleed: CMB-NOW Multisite Pilot Trial

BACKGROUND

Nonvitamin K antagonist oral anticoagulants (NOACs) are considered superior, or at least noninferior, to warfarin in preventing stroke or systemic embolism in patients with nonvalvular atrial fibrillation. Here, we recruited acute ischemic stroke patients with nonvalvular atrial fibrillation and at least one cerebral microbleed (CMB), and evaluated the proportion of patients who had an increased number of CMBs (%) after receiving anticoagulant therapy with NOACs or with warfarin for 12 months.

METHODS

This was a multicenter, prospective, observational cohort study at 20 centers, conducted between 2015 and 2017, in which we recruited 85 patients with at least one CMB detected by 1.5T magnetic resonance imaging (T2*WI) at baseline, who received NOACs or warfarin for at least 12 months. We compared the proportions of patients with increased numbers of CMBs in the NOACs and warfarin treatment groups.

RESULTS

The proportions of patients with increased numbers of CMBs at month 12 of treatment were 28.6% and 66.7% in the NOACs and warfarin groups, respectively. The new CMBs showed no specific regional localization in either group. In the NOACs and warfarin groups, physicians prescribed lower-than-standard dosing in 13.3% and 50% of the cases, respectively. The administration of reduced doses at physicians' discretion did not appear to alter the incidence of new CMBs.

DISCUSSION

This is the first evidence to suggest efficacy of NOACs for preventing further CMBs in patients with at least one CMB, although no statistical evaluation was carried out.

Association between Striatal Brain Iron Deposition, Microbleeds and Cognition 1 Year After a Minor Ischaemic Stroke

Brain iron deposits (IDs) are inversely associated with cognitive function in community-dwelling older people, but their association with cognition after ischemic stroke, and whether that differs from microbleeds, is unknown. We quantified basal ganglia IDs (BGID) and microbleeds (BMBs) semi-automatically on brain magnetic resonance images from patients with minor stroke (NIHSS < 7), at presentation and 12 months after stroke. We administered the National Adult Reading Test (NART, estimates premorbid or peak adult cognition) and the Revised Addenbrooke's Cognitive Examination (ACE-R; current cognition) at 1 and 12 months after stroke. We adjusted analyses for baseline cognition, age, gender, white matter hyperintensity (WMH) volume and vascular risk factors. In 200 patients, mean age 65 years, striatal IDs and BMBs volumes did not change over the 12 months. Baseline BGID volumes correlated positively with NART scores at both times (ρ = 0.19, p < 0.01). Baseline and follow-up BGID volumes correlated positively with age (ρ = 0.248, p < 0.001 and ρ = 0.271, p < 0.001 respectively), but only baseline (and not follow-up) BMB volume correlated with age (ρ = 0.129, p < 0.05). Both smoking and baseline WMH burden predicted verbal fluency and visuospatial abilities scores (B = -1.13, p < 0.02 and B = -0.22, p = 0.001 respectively) at 12 months after stroke. BGIDs and BMBs are associated differently with cognition post-stroke; studies of imaging and post-stroke cognition should adjust for premorbid cognition. The positive correlation of BGID with NART may reflect the lower premorbid cognition in patients with stroke at younger vs older ages.

A Follow-up Study of Cerebral Microbleeds in Patients Who Received Stents for Symptomatic Cerebral Artery Stenosis

BACKGROUND

The aims of this study were to explore (i) the dynamic changes in cerebral microbleeds (CMBs) in patients with symptomatic cerebral artery stenosis who received endovascular stent-assisted angioplasty and (ii) the risk factors associated with the new incidence of CMBs as well as whether CMBs increased the risk of vascular events in these patients.

METHODS

Clinical information and magnetic resonance images were collected on admission and 3 months after endovascular stent-assisted angioplasty. Based on susceptibility-weighted imaging, the patients were divided into groups with or without newly developed CMBs, and between-group differences in risk factors were compared. We also compared whether CMBs increased the risk of vascular events among those patients.

RESULTS

Seventy-three patients completed the relevant follow-up examinations. After an average follow-up period of 109 days, 7 (9.6%) patients showed new CMBs. A univariate analysis showed that the number of lacunar infarcts and the increase in systolic blood pressure were higher in patients with new CMBs than in those without new CMBs, and these differences were significant (P = 0.034, P = 0.001). Increased systolic blood pressure was an independent risk factor for developing new CMBs (P = 0.017).

CONCLUSIONS

CMBs may be a continuously progressing cerebral small-vessel disease. The newly developed CMBs in patients with intracranial and/or extracranial stents were associated with increased systolic blood pressure but not with the number of baseline CMBs.

Characteristics of Cerebral Microbleeds

Cerebral microbleeds (CMBs) are increasingly recognized neuroimaging findings, occurring with cerebrovascular disease, dementia, and aging. CMBs are associated with subsequent hemorrhagic and ischemic stroke, and also with an increased risk of cognitive deterioration and dementia. They occur in the setting of impaired small vessel integrity due to hypertension or cerebral amyloid angiopathy. This review summarizes the concepts, cause or risk factors, histopathological mechanisms, and clinical consequences of CMBs.

Considerations on accuracy, pattern and possible underlying factors of brain microbleed progression in older adults with absence or mild presence of vascular pathology

Objective To analyse brain microbleed (BMB) progression, its possible underlying factors, and the influence of inter-observer differences, in older individuals with none or mild vascular pathology. Methods This study analysed magnetic resonance images, cognitive, demographic and laboratory data from all individuals from the Alzheimer's Disease (AD) Neuroimaging Initiative database who had the required sequences for identifying BMBs over three consecutive years at the time the database was accessed (January 2016). BMBs were assessed independently by two observers with similar levels of experience. Results A total of 291 patients were included in the study. The number of individuals with BMBs and the number of BMBs per individual slightly and nonsignificantly increased across three consecutive years (Y1: 55/291 [19%]; Y2: 61/291 [21%]; Y3: 66/291 [23%]) with 1-2 BMBs and (Y1: 11/291 [4%]; Y2: 12/291 [4%]; Y3: 14/291 [5%]) with ≥ 3 BMBs. Both observers identified a similar pattern of BMB prevalence and progression in each cognitive group (normal < early/late mild cognitive impairment (MCI) > AD patients) despite inter-observer differences (1.5 BMBs, 95% confidence interval -3.7, 6.2], κ=0.543), which were mainly in the cortex. Serum cholesterol was the main predictor of change in BMB count between time-points but did not predict overall progression. Conclusions Inter-observer differences are always present and it is difficult to ascertain their influence in the analysis of BMB progression, which was observed in cognitively normal and MCI individuals, but not in AD patients. This should be confirmed in further studies.

Microbleeds in fronto-subcortical circuits are predictive of dementia conversion in patients with vascular cognitive impairment but no dementia

Cerebral small vessel disease (CSVD) is a common etiology of vascular cognitive impairment with no dementia (V-CIND). Studies have revealed that cerebral microbleeds (CMBs), a feature of CSVD, contribute to cognitive impairment. However, the association between CMBs and dementia conversion in individuals with V-CIND is still unclear. Here, we analyzed the predictive role of CMBs in the conversion from V-CIND to dementia in CSVD patients. We recruited and prospectively assessed 85 patients with CSVD and V-CIND. V-CIND was evaluated using a series of comprehensive neuropsychological scales, including the Chinese version of the Montreal Cognitive Assessment and the Clinical Dementia Rating. MRI assessments were used to quantify lacunar infarcts, white matter hyperintensities, CMBs, and medial temporal lobe atrophy. Eighty-two of the 85 patients completed the assessment for dementia conversion at a 1-year follow-up assessment. Multivariate logistic regression analyses were conducted to examine independent clinical and MRI variables associated with dementia conversion. Twenty-four patients (29.3%) had converted to dementia at the 1-year follow-up, and these individuals had significantly more CMBs in the fronto-subcortical circuits. Multivariate logistic regression analyses revealed that the patients with CMBs in the fronto-subcortical circuits (odds ratio = 4.4; 95% confidence interval: 1.602–12.081, P = 0.004) and 5 or more CMBs overall (odds ratio = 17.6, 95% confidence interval: 3.23–95.84, P = 0.001) had a significantly increased risk of dementia at the 1-year follow-up. These findings indicate that CMBs in the fronto-subcortical circuits may be predictive of dementia conversion in CSVD patients with V-CIND, and thus extend the clinical significance of CMBs. This trial was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR1800017077). Protocol version: 1.0.

Incident risk and progression of cerebral microbleeds in healthy adults: a multi-occasion longitudinal study

Decline in cerebrovascular health complicates brain aging, and development of cerebral microbleeds (CMBs) is one of its prominent indicators. In a large sample of healthy adults (N = 251, age 18-78 years at baseline, 70% women), the contributions of chronological age and vascular health indicators to the risk of developing a CMB, as well as the change in CMB size and iron content, were examined in a prospective 8-year longitudinal study using susceptibility weighted imaging. Twenty-six persons (10.4%), most of whom were 40 years of age or older, had at least 1 CMB during the study. Older age was associated with greater risk for developing a CMB (odds ratio 1.03). Elevation of combined metabolic syndrome indicators (b = 0.15, p = 0.001) conferred additional risk (odds ratio 1.02). High body mass index exacerbated the risk associated with poor vascular health (b = 0.75, p < 0.001) and frequent exercise mitigated it (b = -0.46, p = 0.03). CMBs persisted over time, yet their volume decreased (mean change = -0.32, p < 0.05), whereas their relative iron content remained stable (mean change = -0.14, p = 0.05). We conclude that although developing a CMB is unlikely during normal aging, risk increases with declining vascular health, which is modifiable via behavioral and pharmaceutical intervention.

Nonlinear temporal dynamics of cerebral small vessel disease: The RUN DMC study

OBJECTIVE

To investigate the temporal dynamics of cerebral small vessel disease (SVD) by 3 consecutive assessments over a period of 9 years, distinguishing progression from regression.

METHODS

Changes in SVD markers of 276 participants of the Radboud University Nijmegen Diffusion Tensor and Magnetic Resonance Imaging Cohort (RUN DMC) cohort were assessed at 3 time points over 9 years. We assessed white matter hyperintensities (WMH) volume by semiautomatic segmentation and rated lacunes and microbleeds manually. We categorized baseline WMH severity as mild, moderate, or severe according to the modified Fazekas scale. We performed mixed-effects regression analysis including a quadratic term for increasing age.

RESULTS

Mean WMH progression over 9 years was 4.7 mL (0.54 mL/y; interquartile range 0.95-5.5 mL), 20.3% of patients had incident lacunes (2.3%/y), and 18.9% had incident microbleeds (2.2%/y). WMH volume declined in 9.4% of the participants during the first follow-up interval, but only for 1 participant (0.4%) throughout the whole follow-up. Lacunes disappeared in 3.6% and microbleeds in 5.7% of the participants. WMH progression accelerated over time: including a quadratic term for increasing age during follow-up significantly improved the model (p < 0.001). SVD progression was predominantly seen in participants with moderate to severe WMH at baseline compared to those with mild WMH (odds ratio [OR] 35.5, 95% confidence interval [CI] 15.8-80.0, p < 0.001 for WMH progression; OR 5.7, 95% CI 2.8-11.2, p < 0.001 for incident lacunes; and OR 2.9, 95% CI 1.4-5.9, p = 0.003 for incident microbleeds).

CONCLUSIONS

SVD progression is nonlinear, accelerating over time, and a highly dynamic process, with progression interrupted by reduction in some, in a population that on average shows progression.

Disease progression and regression in sporadic small vessel disease-insights from neuroimaging

Cerebral small vessel disease (SVD) is considered the most important vascular contributor to the development of dementia. Comprehensive characterization of the time course of disease progression will result in better understanding of aetiology and clinical consequences of SVD. SVD progression has been studied extensively over the years, usually describing change in SVD markers over time using neuroimaging at two time points. As a consequence, SVD is usually seen as a rather linear, continuously progressive process. This assumption of continuous progression of SVD markers was recently challenged by several studies that showed regression of SVD markers. Here, we provide a review on disease progression in sporadic SVD, thereby taking into account both progression and regression of SVD markers with emphasis on white matter hyperintensities (WMH), lacunes and microbleeds. We will elaborate on temporal dynamics of SVD progression and discuss the view of SVD progression as a dynamic process, rather than the traditional view of SVD as a continuous progressive process, that might better fit evidence from longitudinal neuroimaging studies. We will discuss possible mechanisms and clinical implications of a dynamic time course of SVD, with both progression and regression of SVD markers.

Insulin-like growth factor 1 deficiency exacerbates hypertension-induced cerebral microhemorrhages in mice, mimicking the aging phenotype

Clinical and experimental studies show that aging exacerbates hypertension‐induced cerebral microhemorrhages (CMHs), which progressively impair neuronal function. There is growing evidence that aging promotes insulin‐like growth factor 1 (IGF‐1) deficiency, which compromises multiple aspects of cerebromicrovascular and brain health. To determine the role of IGF‐1 deficiency in the pathogenesis of CMHs, we induced hypertension in mice with liver‐specific knockdown of IGF‐1 (Igf1^f/f + TBG‐Cre‐AAV8) and control mice by angiotensin II plus l‐NAME treatment. In IGF‐1‐deficient mice, the same level of hypertension led to significantly earlier onset and increased incidence and neurological consequences of CMHs, as compared to control mice, as shown by neurological examination, gait analysis, and histological assessment of CMHs in serial brain sections. Previous studies showed that in aging, increased oxidative stress‐mediated matrix metalloprotease (MMP) activation importantly contributes to the pathogenesis of CMHs. Thus, it is significant that hypertension‐induced cerebrovascular oxidative stress and MMP activation were increased in IGF‐1‐deficient mice. We found that IGF‐1 deficiency impaired hypertension‐induced adaptive media hypertrophy and extracellular matrix remodeling, which together with the increased MMP activation likely also contributes to increased fragility of intracerebral arterioles. Collectively, IGF‐1 deficiency promotes the pathogenesis of CMHs, mimicking the aging phenotype, which likely contribute to its deleterious effect on cognitive function. Therapeutic strategies that upregulate IGF‐1 signaling in the cerebral vessels and/or reduce microvascular oxidative stress, and MMP activation may be useful for the prevention of CMHs, protecting cognitive function in high‐risk elderly patients.

Anticoagulation for Atrial Fibrillation in Patients with Cerebral Microbleeds

Intracranial haemorrhage (ICH) is the most feared and devastating complication of oral anticoagulation, with high mortality and disability in survivors. Oral anticoagulant-related ICH is increasing in incidence, most likely in part due to the increased use of anticoagulation for atrial fibrillation in the elderly populations with a high prevalence of bleeding-prone cerebral small vessel diseases. Risk scores have been developed to predict bleeding, including ICH, as well as the risk of ischaemic stroke. Recently, attention has turned to brain imaging, in particular, MRI detection of potential prognostic biomarkers, which may help better predict outcomes and individualize anticoagulant decisions. Cerebral microbleeds (CMBs)--small, round areas of signal loss on blood-sensitive MR sequences--have been hypothesized to be a marker for bleeding-prone small vessel pathology, and thus, future symptomatic ICH risk. In this review, we outline the prevalence and prognostic value of CMBs in populations affected by AF for whom anticoagulation decisions are relevant, including healthy older individuals and survivors of ischaemic stroke or ICH. We consider the limitations of currently available evidence, and discuss future research directions in relation to both prognostic markers and treatment options for atrial fibrillation.

An Up-to-Date Review on Cerebral Microbleeds

BACKGROUND

Cerebral microbleeds (CMBs) are small cerebrovascular lesions. More and more CMBs have been found in patients with ischemic stroke, dementia, and cerebral amyloid angiopathy, as well as some normal elderly populations. The objective of this study is to summarize the main risk factor, impairment, and therapy of CMBs.

METHODS

We searched and scanned all the literature with the keyword "cerebral microbleeds" or "CMBs" in the database of PubMed and Elsevier.

RESULTS

The risks factors for CMBs are complicated, including those that cause large-vessel disease, such as hypertension and old age, and those that cause small-vessel disease, such as amyloid deposits, endothelial lesions, and atrial fibrillation. Moreover, drugs and therapies used to treat cerebrovascular diseases such as statin, intravenous thrombolysis, and coumarin may also increase risk of CMBs. The relationship between antiplatelet treatment and CMBs is now unclear. Gene polymorphisms have been considered to be associated with CMBs. Gene mutations involving collagen type IV alpha 1 and collagen type IV alpha 2, sortilin-related receptor gene, forkhead box C1, and paired-like homeodomain 2 were reported to affect CMBs with the modification of corresponding proteins and functions. The cognition impairment caused by CMBs draws great attention. White matter deterioration is the possible answer. However, different studies could not reach the same conclusion on the damage of cognition of CMBs.

CONCLUSIONS

Further research is needed to provide effectual therapeutic proposals for CMBs, which differ from the treatment for large-artery disease and dementia.

The clinical significance of brain microbleeds in patients with Alzheimer's disease: Preliminary study

Background:

Microbleeds (MBs) are observed frequently in Alzheimer's disease (AD) and suggested to play a crucial role in the pathophysiology, but their clinical significance remains unclear.

Materials and Methods:

The study recruited 100 patients with AD who were diagnosed at the memory clinic in Seoul Medical Center in 2014. For each patient, baseline characteristics, neuropsychological tests, cerebrovascular risk factors, medial temporal lobe atrophy (MTLA), and severity of small vessel disease (SVD) according to the existence of MBs were evaluated.

Results:

The prevalence of MBs in patients with AD was 33%. The percentage of male gender, the severity of SVD and MTLA were significantly increased in MB(+) group. The MB(+) group showed more severe MTLA and SVD than MB(−) group.

Conclusions:

These results suggested that MBs might reflect the burden of amyloid and ischemic vascular pathology.

Longitudinal change of small-vessel disease-related brain abnormalities

Knowledge about the longitudinal change of cerebral small-vessel disease–related magnetic resonance imaging abnormalities increases our pathophysiologic understanding of cerebral microangiopathy. The change of specific lesion types may also serve as secondary surrogate endpoint in clinical trials. A surrogate endpoint needs to progress fast enough to allow monitoring of treatment effects within a reasonable time period, and change of the brain abnormality needs to be correlated with clinical change. Confluent white matter lesions show fast progression and correlations with cognitive decline. Thus, the change of confluent white matter lesions may be used as a surrogate marker in proof-of-concept trials with small patient numbers needed to show treatment effects on lesion progression. Nonetheless if the expected change in cognitive performance resulting from treatment effects on lesion progression is used as outcome, the sample size needed to show small to moderate treatment effects becomes very large. Lacunes may also fulfill the prerequisites of a surrogate marker, but in the general population the incidence of lacunes over short observational periods is small. For other small-vessel disease–related brain abnormalities including microbleeds and microstructural changes in normal-appearing white matter longitudinal change and correlations with clinical decline is not yet fully determined.

Silent New Brain Lesions: Innocent Bystander or Guilty Party?

With the advances in magnetic resonance imaging, previously unrecognized small brain lesions, which are mostly asymptomatic, have been increasingly detected. Diffusion-weighted imaging can identify small ischemic strokes, while gradient echo T2* imaging and susceptibility-weighted imaging can reveal tiny hemorrhagic strokes (microbleeds). In this article, we review silent brain lesions appearing soon after acute stroke events, including silent new ischemic lesions and microbleeds appearing 1) after acute ischemic stroke and 2) after acute intracerebral hemorrhage. Moreover, we briefly discuss the clinical implications of these silent new brain lesions.

Endothelial depletion of murine SRF/MRTF provokes intracerebral hemorrhagic stroke

Intracerebral hemorrhagic stroke and vascular dementia are age- and hypertension-associated manifestations of human cerebral small vessel disease (SVD). Cerebral microvessels are formed by endothelial cells (ECs), which are connected through tight junctions, adherens junctions, and stabilizing basement membrane structures. These endothelial connections ensure both vessel stability and blood-brain barrier (BBB) functions, the latter enabling selective exchange of ions, bioactive molecules, and cells between the bloodstream and brain tissue. Srf(iECKO) mice, permitting conditional EC-specific depletion of the transcription factor Serum Response Factor (SRF), suffer from loss of BBB integrity and intracerebral hemorrhaging. Cerebral microbleeds and larger hemorrhages developed upon postnatal and adult depletion of either SRF or its cofactors Myocardin Related Transcription Factor (MRTF-A/-B), revealing essential requirements of ongoing SRF/MRTF activity for maintenance of cerebral small vessel integrity. In vivo magnetic resonance imaging allowed detection, localization, and time-resolved quantification of BBB permeability and hemorrhage formation in Srf(iECKO) brains. At the molecular level, direct and indirect SRF/MRTF target genes, encoding structural components of tight junctions (Claudins and ZO proteins), adherens junctions (VE-cadherin, α-Actinin), and the basement membrane (Collagen IV), were down-regulated upon SRF depletion. These results identify SRF and its MRTF cofactors as major transcriptional regulators of EC junctional stability, guaranteeing physiological functions of the cerebral microvasculature. We hypothesize that impairments in SRF/MRTF activity contribute to human SVD pathology.

Clinical significance of cerebral microbleeds locations in CADASIL with R544C NOTCH3 mutation

Background and Purpose

Although cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common single-gene disorder of cerebral small blood vessels caused by NOTCH3 mutations, little has been described about the variation in the clinical findings between its underlying types of mutations. In particular, the presence of cerebral microbleeds (CMBs) has been an increasingly recognized magnetic resonance imaging finding in CADASIL, but their clinical significance is not clear. The purpose of this study is to assess whether CMBs are associated with symptomatic stroke in the CADASIL patients with R544C mutation and to compare the cerebral distribution of CMBs between CADASIL patients with and without symptomatic stroke.

Methods

This is a cohort study of patients who were diagnosed with genotype-confirmed R544C-mutation CADASIL. Primary neurologic symptoms were recorded. Symptomatic strokes were defined as transient ischemic attack, ischemic strokes and hemorrhagic strokes. CMBs were defined as focal areas of round signal loss on T2*-weighted gradient echo planar images with a diameter of less than 10 mm. The locations of CMBs were divided into lobar, basal ganglia, thalamus, brain stem and cerebellum. Multiple logistic regressions were performed to identify the epidemiologic or vascular risk factors associated with symptomatic stroke in patients with CADASIL.

Results

Among total of 51 subjects in this cohort, CMBs were present in 20 of 32 patients (64.5%) in the symptomatic stroke-group and in 8 of 19 patients (42.1%) in the non-stroke group (p = 0.16). CMBs were observed more frequently in the basal ganglia (p<0.001) and the cerebellum (p<0.018) in the symptomatic stoke group compared to the non-stroke group. The mean number of CMBs was significantly higher in the symptomatic stroke group (15.4±18.0 lesions per patients with CMBs) versus those without symptomatic stroke (3.3±3.0 lesions per patients with CMBs) (p = 0.003). Hypertension was an independent risk factor for symptomatic stroke in CADASIL (p = 0.014). It was independently associated with CMBs locations as basal ganglia (p = 0.016), thalamus (p = 0.010), brainstem (p = 0.044), and cerebellum (p = 0.049). However, It was not independently associated with CMBs on lobar lesion (p = 0.152).

Conclusions

In this study hypertension was an independent predictor of CMBs presence in specific brain locations, as well as symptomatic stroke in the CADASIL patients. The distribution and burden of CMBs might be a clinically useful marker for the risk of symptomatic stroke. However, further prospective studies on the relationship between CMBs distribution and symptomatic stroke are required in order to support these preliminary findings.

Incidence of cerebral microbleeds in preclinical Alzheimer disease

OBJECTIVE

We sought to determine the incidence and associations of lobar microbleeds (LMBs) in a longitudinal cohort with (11)C-Pittsburgh compound B (PiB) PET imaging.

METHODS

One hundred seventy-four participants from the observational Australian Imaging, Biomarkers and Lifestyle Study of Ageing (97 with normal cognition [NC], 37 with mild cognitive impairment [MCI], and 40 with Alzheimer disease [AD] dementia) were assessed at 3 time points over 3 years with 3-tesla susceptibility-weighted MRI and (11)C-PiB PET. MRIs were inspected for microbleeds, siderosis, infarction, and white matter hyperintensity severity, blind to clinical and PiB findings. Neocortical PiB standardized uptake value ratio, normalized to cerebellar cortex, was dichotomized as positive or negative (PiB+/-, standardized uptake value ratio >1.5). Annualized LMB incidence was calculated, and logistic regression was used to determine the association of incident LMBs with PiB, APOE ε4+ status, and cerebrovascular disease.

RESULTS

LMBs were present in 18.6% of NC, 24.3% of MCI, and 40% of AD participants (p < 0.05 vs NC). LMB incidence was 0.2 ± 0.6 per year in NC participants, 0.2 ± 0.5 in MCI, and 0.7 ± 1.4 in AD (p < 0.03 vs NC) and was 6-fold higher in PiB+ than PiB-NC. Incident LMBs were associated with age, APOE ε4+, PiB+, and baseline LMBs. Incidence of multiple LMBs was also associated with lacunar infarction and white matter hyperintensity severity.

CONCLUSIONS

Older age, baseline LMBs, higher β-amyloid burden, and concomitant cerebrovascular disease may all confer higher risk of incident LMBs. This should be considered when designing protocols for amyloid-modifying clinical trials.

Cerebral microbleeds: a review of clinical, genetic, and neuroimaging associations

Cerebral microbleeds (microbleeds) are small, punctuate hypointense lesions seen in T2* Gradient-Recall Echo (GRE) and Susceptibility-Weighted (SWI) Magnetic Resonance Imaging (MRI) sequences, corresponding to areas of hemosiderin breakdown products from prior microscopic hemorrhages. They occur in the setting of impaired small vessel integrity, commonly due to either hypertensive vasculopathy or cerebral amyloid angiopathy. Microbleeds are more prevalent in individuals with Alzheimer’s disease (AD) dementia and in those with both ischemic and hemorrhagic stroke. However they are also found in asymptomatic individuals, with increasing prevalence with age, particularly in carriers of the Apolipoprotein (APOE) ε4 allele. Other neuroimaging findings that have been linked with microbleeds include lacunar infarcts and white matter hyperintensities on MRI, and increased cerebral β-amyloid burden using ¹¹C-PiB Positron Emission Tomography. The presence of microbleeds has been suggested to confer increased risk of incident intracerebral hemorrhage – particularly in the setting of anticoagulation – and of complications of immunotherapy for AD. Prospective data regarding the natural history and sequelae of microbleeds are currently limited, however there is a growing evidence base that will serve to inform clinical decision-making in the future.

Cerebral microbleeds: their associated factors, radiologic findings, and clinical implications

Cerebral microbleeds (CMBs) are tiny, round dark-signal lesions that are most often detected on gradient-echo MR images. CMBs consist of extravasations of blood components through fragile microvascular walls characterized by lipohyalinosis and surrounding macrophages. The prevalence of CMBs in elderly subjects with no history of cerebrovascular disease is around 5%, but is much higher in patients with ischemic or hemorrhagic stroke. Development of CMBs is closely related to various vascular risk factors; in particular, lobar CMBs are thought to be associated with cerebral amyloid angiopathy. The presence of CMBs has been hypothesized to reflect cerebral-hemorrhage-prone status in patients with hypertension or amyloid microangiopathy. Stroke survivors with CMBs have been consistently found to have an elevated risk of subsequent hemorrhagic stroke or an antithrombotic-related hemorrhagic complication, although studies have failed to establish a link between CMBs and hemorrhagic transformation after thrombolytic treatment. A large prospective study is required to clarify the clinical significance of CMBs and their utility in a decision-making index.

Micro-MRI study of cerebral aging: ex vivo detection of hippocampal subfield reorganization, microhemorrhages and amyloid plaques in mouse lemur primates

Mouse lemurs are non-human primate models of cerebral aging and neurodegeneration. Much smaller than other primates, they recapitulate numerous features of human brain aging, including progressive cerebral atrophy and correlation between regional atrophy and cognitive impairments. Characterization of brain atrophy in mouse lemurs has been done by MRI measures of regional CSF volume and by MRI measures of regional atrophy. Here, we further characterize mouse lemur brain aging using ex vivo MR microscopy (31 µm in-plane resolution). First, we performed a non-biased, direct volumetric quantification of dentate gyrus and extended Ammon's horn. We show that both dentate gyrus and Ammon's horn undergo an age-related reorganization leading to a growth of the dentate gyrus and an atrophy of the Ammon's horn, even in the absence of global hippocampal atrophy. Second, on these first MR microscopic images of the mouse lemur brain, we depicted cortical and hippocampal hypointense spots. We demonstrated that their incidence increases with aging and that they correspond either to amyloid deposits or to cerebral microhemorrhages.

Cerebral microbleeds: a new dilemma in stroke medicine

Cerebral microbleeds (CMBs) are an increasingly common neuroimaging finding in the context of ageing, cerebrovascular disease and dementia, with potentially important clinical relevance. Perhaps the most pressing clinical question is whether CMBs are associated with a clinically important increase in the risk of intracerebral haemorrhage (ICH), the most feared complication in patients treated with thrombolytic or antithrombotic (antiplatelet and anticoagulant) drugs. This review will summarize the evidence available regarding CMBs as an indicator of future ICH risk in stroke medicine clinical practice.

Cerebral microbleeds on magnetic resonance imaging and anticoagulant-associated intracerebral hemorrhage risk

The increasing use of antithrombotic drugs in an aging population [including anticoagulants to prevent future ischemic stroke in individuals with atrial fibrillation (AF)] has been associated with a dramatic increase in the incidence of intracerebral hemorrhage (ICH) in users of antithrombotic drugs. Several lines of evidence suggest that cerebral small vessel disease (particularly sporadic cerebral amyloid angiopathy) is a risk factor for this rare but devastating complication of these commonly used treatments. Cerebral microbleeds (CMBs) have emerged as a key MRI marker of small vessel disease and a potentially powerful marker of future ICH risk, but adequately powered, high quality prospective studies of CMBs and ICH risk on anticoagulation are not available. Further data are urgently needed to determine how neuroimaging and other biomarkers may contribute to individualized risk prediction to make anticoagulation as safe and effective as possible. In this review we discuss the available evidence on cerebral small vessel disease and CMBs in the context of antithrombotic treatments, especially regarding their role as a predictor of future ICH risk after ischemic stroke, where risk-benefit judgments can be a major challenge for physicians. We will focus on patients with AF because these are frequently treated with anticoagulation. We briefly describe the rationale and design of a new prospective observational inception cohort study (Clinical Relevance of Microbleeds in Stroke; CROMIS-2) which investigates the value of MRI markers of small vessel disease (including CMBs) and genetic factors in assessing the risk of oral anticoagulation-associated ICH.

Differential risk factors for lacunar stroke depending on the MRI (white and red) subtypes of microangiopathy

Background

Leukoaraiosis and cerebral microbleeds (CMB), which represent cerebral microangiopathy, commonly coexist in patients with acute lacunar stroke. Since they may have different impacts on stroke prognosis and treatment, it is important to know the factors associated with leukoaraiosis-predominant vs. CMB-predominant microangiopathies.

Methods

We prospectively recruited 226 patients with acute lacunar infarction and divided them into four groups according to the Fazekas’ score and the presence of CMB: mild, red (predominant CMB), white (predominant leukoaraiosis) and severe microangiopathy groups. For comparison, we also evaluated 50 patients with intracerebral hemorrhage (ICH). We evaluated the clinical and laboratory findings of microangiopathy subtypes in patients with acute lacunar stroke and then compared them with those of primary ICH.

Results

The risk factor profile was different among the groups. Patients with acute lacunar infarct but mild microangiopathy were younger, predominantly male, less hypertensive, and more frequently had smoking and heavy alcohol habits than other groups. The risk factor profile of red microangiopathy was similar to that of ICH but differed from that of white microangiopathy. The subjects in the white microangiopathy group were older and more frequently had diabetes than those in the red microangiopathy or ICH group. After adjustments for other factors, age [odds ratio (OR) 1.13; 95% confidence interval (CI) 1.08–1.18; p<0.001] and diabetes (OR 2.28; 95% CI 1.02–5.13; p = 0.045) were independently associated with white microangiopathy, and age (OR 1.05; 95% CI 1.01–1.08; p = 0.010) was independent predictor for red microangiopathy compared to mild microangiopathy.

Conclusion

Patients with acute lacunar infarction have a different risk factor profile depending on microangiopathic findings. Our results indicate that diabetes may be an one of determinants of white (leukoaraiosis-predominant) microangiopathy, whereas smoking and alcohol habits in relatively young people may be a determinants of mild microangiopahic changes in patients with lacunar infarction.