Cerebral microbleeds in acute ischemic stroke after intravenous thrombolysis and their impact on short term outcome of stroke

OBJECTIVES

Strong evidence suggests the occurrence of cerebral microbleeds (CMBs) in 5-13% of stroke patients within the first week after stroke onset. The aim of this work was to study risk factors associated with occurrence of CMBs in patients with stroke who received intravenous thrombolysis, and to clarify their impact on the clinical outcome.

METHODS

This prospective observational study was conducted on 61 acute ischemic stroke patients eligible for treatment with recombinant tissue plasminogen activator (rt-PA). Assessment of stroke-related neurologic deficit was done using National Institute of Health Stroke Scale (NIHSS). Assessment of stroke related disability after 3 months from stroke onset was done using Modified Rankin Scale (mRS). CMBs were detected by T2*-weighed gradient-recalled echo (T2*-GRE) and susceptibility-weighted imaging (SWI) magnetic resonance imaging (MRI) sequences.

RESULTS

There was a statistically significant impact of age, mean arterial pressure (MAP) at stroke onset, history of hypertension (HTN), and white matter changes assessed by Fazekas scale on the occurrence of CMBs in the included stroke patients (P-value= 0.002, <0.001, <0.001, 0.008 respectively). There was no statistically significant difference between patients with favorable and those with unfavorable outcome regarding the total number of CMBs (P-value =0.542). There was also no statistically significant difference between patients who developed complications from rt-PA and those who didn't develop regarding the total number of CMBs (P-value =0.186).

CONCLUSION

Cerebral microbleeds are more likely to occur in older stroke patients and in those who had high MAP at stroke onset, history of HTN, and white matter changes.

Critical illness-associated cerebral microbleeds involving the corpus callosum following cardiac arrest: A case report

RATIONALE

Critical illness-associated cerebral microbleeds (CI-aCMBs) are emerging as significant radiographic findings in patients with hypoxic ischemic injuries. Their occurrence, particularly in the corpus callosum, warrants a closer examination due to the potential implications for neurological outcomes in critically ill patients. We aim to describe a rare case of CI-aCMBs within the corpus callosum following cardiac arrest with the goal of bolstering the scientific literature on this topic.

PATIENT CONCERNS

A 34-year-old man with a history of polysubstance abuse was found unconscious and experienced a pulseless electrical activity (PEA) cardiac arrest after a suspected drug overdose. Post-resuscitation, the patient exhibited severe respiratory distress, acute kidney injury, and profound neurological deficits.

DIAGNOSES

Initial magnetic resonance imaging scans post-cardiac arrest showed no acute brain abnormalities. However, subsequent imaging revealed extensive cerebral microbleeds predominantly in the corpus callosum, diagnosed as CI-aCMBs. These findings were made in the absence of high signal intensity on T2-weighted images, suggesting a unique pathophysiological profile of microhemorrhages.

INTERVENTIONS

The patient underwent targeted temperature management (TTM) and supportive care in the intensive care unit after cardiac arrest.

OUTCOMES

He was subsequently extubated and had significant recovery without any neurological deficits.

LESSONS

CI-aCMBs is a rare radiographic finding after cardiac arrest. These lesions may be confined to the corpus callosum and the long-term clinical and radiographic sequelae are still largely unknown.

Cerebral Microbleeds Associate with Brain Endothelial Cell Activation-Dysfunction and Blood-Brain Barrier Dysfunction/Disruption with Increased Risk of Hemorrhagic and Ischemic Stroke

Globally, cerebral microbleeds (CMBs) are increasingly being viewed not only as a marker for cerebral small vessel disease (SVD) but also as having an increased risk for the development of stroke (hemorrhagic/ischemic) and aging-related dementia. Recently, brain endothelial cell activation and dysfunction and blood-brain barrier dysfunction and/or disruption have been shown to be associated with SVD, enlarged perivascular spaces, and the development and evolution of CMBs. CMBs are a known disorder of cerebral microvessels that are visualized as 3-5 mm, smooth, round, or oval, and hypointense (black) lesions seen only on T2*-weighted gradient recall echo or susceptibility-weighted sequences MRI images. CMBs are known to occur with high prevalence in community-dwelling older individuals. Since our current global population is the oldest recorded in history and is only expected to continue to grow, we can expect the healthcare burdens associated with CMBs to also grow. Increased numbers (≥10) of CMBs should raise a red flag regarding the increased risk of large symptomatic neurologic intracerebral hemorrhages. Importantly, CMBs are also currently regarded as markers of diffuse vascular and neurodegenerative brain damage. Herein author highlights that it is essential to learn as much as we can about CMB development, evolution, and their relation to impaired cognition, dementia, and the exacerbation of neurodegeneration.

Molecular cross-talk between long COVID-19 and Alzheimer's disease

The long COVID (coronavirus disease), a multisystemic condition following severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, is one of the widespread problems. Some of its symptoms affect the nervous system and resemble symptoms of Alzheimer's disease (AD)-a neurodegenerative condition caused by the accumulation of amyloid beta and hyperphosphorylation of tau proteins. Multiple studies have found dependence between these two conditions. Patients with Alzheimer's disease have a greater risk of SARS-CoV-2 infection due to increased levels of angiotensin-converting enzyme 2 (ACE2), and the infection itself promotes amyloid beta generation which enhances the risk of AD. Also, the molecular pathways are alike-misregulations in folate-mediated one-carbon metabolism, a deficit of Cq10, and disease-associated microglia. Medical imaging in both of these diseases shows a decrease in the volume of gray matter, global brain size reduction, and hypometabolism in the parahippocampal gyrus, thalamus, and cingulate cortex. In some studies, a similar approach to applied medication can be seen, including the use of amino adamantanes and phenolic compounds of rosemary. The significance of these connections and their possible application in medical practice still needs further study but there is a possibility that they will help to better understand long COVID.

Cerebral microbleeds and asundexian in non-cardioembolic ischemic stroke: Secondary analyses of the PACIFIC-STROKE randomized trial

BACKGROUND AND AIMS

Cerebral microbleeds are magnetic imaging resonance (MRI) markers of hemorrhage-prone cerebral small vessel disease that predict future risk of ischemic stroke and intracranial hemorrhage (ICrH). There exist concerns about the net benefit of antithrombotic therapy in patients with microbleeds. We aimed to investigate the effects of an oral factor-XIa inhibitor (asundexian), that is hypothesized to inhibit thrombosis without compromising hemostasis, on the development of new microbleeds over time and interactions between microbleeds and asundexian treatment on clinical outcomes. We additionally assessed associations between baseline microbleeds and the risks of clinical and neuroimaging outcomes in patients with non-cardioembolic ischemic stroke.

METHODS

This is a secondary analysis of the PACIFIC-STROKE, international, multi-center Phase 2b double-blind, randomized clinical trial. PACIFIC-STROKE enrolled patients aged ⩾ 45 years with mild-to-moderate non-cardioembolic ischemic stroke who presented within 48 h of symptom onset for whom antiplatelet therapy was intended. Microbleeds were centrally adjudicated, and participants with an interpretable T2*-weighted sequence at their baseline MRI were included in this analysis. Patients were randomized to asundexian (10/20/50 mg daily) versus placebo plus standard antiplatelet treatment. Regression models were used to estimate the effects of (1) all pooled asundexian doses and (2) asundexian 50 mg daily on new microbleed formation on 26-week MRIs. Cox proportional hazards or regression models were additionally used to estimate interactions between treatment assignment and microbleeds for ischemic stroke/transient ischemic attack (TIA) (primary outcome), and ICrH, all-cause mortality, hemorrhagic transformation (HT), and new microbleeds (secondary outcomes).

RESULTS

Of 1746 participants (mean age, 67.0 ± 10.0; 34% female) with baseline MRIs, 604 (35%) had microbleeds. During a median follow-up of 10.6 months, 7.0% (n = 122) had ischemic stroke/TIA, 0.5% (n = 8) ICrH, and 2.1% (n = 37) died. New microbleeds developed in 10.3% (n = 155) of participants with adequate follow-up MRIs and HT in 31.4% (n = 345). In the total sample of patients with adequate baseline and 26-week follow-up MRIs (n = 1507), new microbleeds occurred in 10.2% of patients assigned to any asundexian dose and 10.5% of patients assigned to placebo (OR, 0.96; 95% CI, 0.66-1.41). There were no interactions between microbleeds and treatment assignment for any of the outcomes (p for interaction > 0.05). The rates of new microbleeds, HT, and ICrH were numerically less in patients with microbleeds assigned to asundexian relative to placebo. The presence of microbleeds was associated with a higher risk of HT (aOR, 1.6; 95% CI, 1.2-2.1) and new microbleeds (aOR, 4.4; 95% CI, 3.0-6.3).

CONCLUSION

Factor XIa inhibition with asundexian appears safe in patients with non-cardioembolic ischemic stroke and hemorrhage-prone cerebral small vessel disease marked by microbleeds on MRI. These preliminary findings will be confirmed in the ongoing OCEANIC-STROKE randomized trial.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04304508.

Statin Therapy for Secondary Prevention in Ischemic Stroke Patients With Cerebral Microbleeds

BACKGROUND AND OBJECTIVES

The association between statin use and the risk of intracranial hemorrhage (ICrH) following ischemic stroke (IS) or transient ischemic attack (TIA) in patients with cerebral microbleeds (CMBs) remains uncertain. This study investigated the risk of recurrent IS and ICrH in patients receiving statins based on the presence of CMBs.

METHODS

We conducted a pooled analysis of individual patient data from the Microbleeds International Collaborative Network, comprising 32 hospital-based prospective studies fulfilling the following criteria: adult patients with IS or TIA, availability of appropriate baseline MRI for CMB quantification and distribution, registration of statin use after the index stroke, and collection of stroke event data during a follow-up period of ≥3 months. The primary endpoint was the occurrence of recurrent symptomatic stroke (IS or ICrH), while secondary endpoints included IS alone or ICrH alone. We calculated incidence rates and performed Cox regression analyses adjusting for age, sex, hypertension, atrial fibrillation, previous stroke, and use of antiplatelet or anticoagulant drugs to explore the association between statin use and stroke events during follow-up in patients with CMBs.

RESULTS

In total, 16,373 patients were included (mean age 70.5 ± 12.8 years; 42.5% female). Among them, 10,812 received statins at discharge, and 4,668 had 1 or more CMBs. The median follow-up duration was 1.34 years (interquartile range: 0.32-2.44). In patients with CMBs, statin users were compared with nonusers. Compared with nonusers, statin therapy was associated with a reduced risk of any stroke (incidence rate [IR] 53 vs 79 per 1,000 patient-years, adjusted hazard ratio [aHR] 0.68 [95% CI 0.56-0.84]), a reduced risk of IS (IR 39 vs 65 per 1,000 patient-years, aHR 0.65 [95% CI 0.51-0.82]), and no association with the risk of ICrH (IR 11 vs 16 per 1,000 patient-years, aHR 0.73 [95% CI 0.46-1.15]). The results in aHR remained consistent when considering anatomical distribution and high burden (≥5) of CMBs.

DISCUSSION

These observational data suggest that secondary stroke prevention with statins in patients with IS or TIA and CMBs is associated with a lower risk of any stroke or IS without an increased risk of ICrH.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that for patients with IS or TIA and CMBs, statins lower the risk of any stroke or IS without increasing the risk of ICrH.

Blood-based biomarkers of cerebral small vessel disease

Age-associated cerebral small vessel disease (CSVD) represents a clinically heterogenous condition, arising from diverse microvascular mechanisms. These lead to chronic cerebrovascular dysfunction and carry a substantial risk of subsequent stroke and vascular cognitive impairment in aging populations. Owing to advances in neuroimaging, in vivo visualization of cerebral vasculature abnormities and detection of CSVD, including lacunes, microinfarcts, microbleeds and white matter lesions, is now possible, but remains a resource-, skills- and time-intensive approach. As a result, there has been a recent proliferation of blood-based biomarker studies for CSVD aimed at developing accessible screening tools for early detection and risk stratification. However, a good understanding of the pathophysiological processes underpinning CSVD is needed to identify and assess clinically useful biomarkers. Here, we provide an overview of processes associated with CSVD pathogenesis, including endothelial injury and dysfunction, neuroinflammation, oxidative stress, perivascular neuronal damage as well as cardiovascular dysfunction. Then, we review clinical studies of the key biomolecules involved in the aforementioned processes. Lastly, we outline future trends and directions for CSVD biomarker discovery and clinical validation.

Prevalence, Risk Factors, and Clinical Outcomes of New Cerebral Microbleeds After Intravenous Thrombolysis in Acute Ischemic Stroke: a Systematic Review and Meta-analysis

BACKGROUND

Cerebral microbleeds (CMBs) are common in the elderly population, and are associated with an increased risk of stroke and dementia. An acute ischemic stroke event can make CMBs develop rapidly. However, the progression of CMBs after intravenous thrombolysis is not well understood.

METHODS

Following a previously registered protocol, PubMed, Web of Science, and Embase databases were systematically searched to identify relevant literature up to August 2022. Cohort studies that reported new CMBs in patients with acute ischemic stroke undergoing intravenous thrombolysis were included. Random effects models were used to calculate the pooled estimates.

RESULTS

Seven studies with 1079 patients were included in the meta-analysis. The pooled new CMBs prevalence was 7.6% (95% CI 3.9-14.3%) and 63.6% new CMBs were located in the cerebral lobes. Compared with patients without new CMBs, those with new CMBs were older, had a higher proportion of hypertension, and had higher systolic blood pressure and baseline CMBs burden. The presence of new CMBs increased the likelihood of remote intracerebral hemorrhage (OR 28.75, 95% CI 8.58-96.38) and symptomatic intracerebral hemorrhage (OR 15.49, 95% CI 3.21-74.73) but was not related to functional outcomes or hemorrhagic transformation.

CONCLUSIONS

The prevalence of new CMBs after intravenous thrombolysis was approximately 7.6%. The presence of new CMBs is associated with remote and symptomatic intracerebral hemorrhage following intravenous thrombolysis. Considering the potential long-term adverse effects of CMBs progression, patients at a high risk of developing new CMBs should be identified based on potential risk factors.

Histopathological characterization of cerebral small vessel disease in epilepsy patients with temporal lobe epilepsy submitted to surgery: A case-control study

BACKGROUND

Cerebrovascular disease (CVD) is a major contributor to epilepsy; however, patients with epilepsy also have a significantly increased risk of stroke. The way in which epilepsy contributes to the increased risk of stroke is still uncertain and is ill-characterized in neuropathological studies. A neuropathological characterization of cerebral small vessel disease (cSVD) in patients with chronic epilepsy was performed.

METHODS

Thirty-three patients with refractory epilepsy and hippocampal sclerosis (HS) submitted to epilepsy surgery from a reference center were selected between 2010 and 2020 and compared with 19 autopsy controls. Five randomly selected arterioles from each patient were analyzed using a previously validated scale for cSVD. The presence of CVD disease imaging markers in pre-surgical brain magnetic resonance imaging (MRI) was studied.

RESULTS

There were no differences in age (43.8 vs. 41.6 years; p = 0.547) or gender distribution (female gender 60.6% vs. male gender 52.6%; p = 0.575) between groups. Most CVD findings in brain MRI were mild. Patients had a mean time between the epilepsy onset and surgery of 26 ± 14.7 years and were medicated with a median number of three antiseizure medication (ASMs) [IQR 2-3]. Patients had higher median scores in arteriolosclerosis (3 vs. 1; p < 0.0001), microhemorrhages (4 vs. 1; p < 0.0001) and total score value (12 vs. 8.9; p = 0.031) in comparison with controls. No correlation was found between age, number of years until surgery, number of ASMs or cumulative defined daily dosage of ASM.

CONCLUSION

The present study provides evidence supporting the increased burden of cSVD in the neuropathological samples of patients with chronic epilepsy.

Impact of pre-treatment cerebral microbleeds on the outcomes of endovascular thrombectomy: A systematic review and meta-analysis

OBJECTIVE/AIM

To investigate the effect of cerebral microbleeds (CMBs) on the functional and safety outcomes of endovascular thrombectomy (EVT) in patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO).

METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines for systematic review and meta-analysis. We included observational studies that recruited AIS-LVO patients, used susceptibility-sensitive magnetic resonance imaging (MRI) to detect CMBs, and examined the association between them and predefined outcome events. The extracted data included study and population characteristics, risk of bias domains, and outcome measures. The outcomes of interest included functional independence, revascularization success, procedural and hemorrhagic adverse events. We conducted a meta-analysis using the Mantel-Haenszel method and calculated the risk ratios.

RESULTS

Four studies with a total of 1,514 patients were included. A significant reduction in the likelihood of achieving a favorable functional outcome was observed in patients with CMBs (Risk ratio (RR) 0.69, 95% confidence interval (CI): 0.52 to 0.91, P=0.01). No significant differences were observed between the CMBs and no CMBs groups in terms of successful revascularization, mortality, intracranial hemorrhage (ICH), subarachnoid hemorrhage (SAH), and parenchymal hematoma.

CONCLUSIONS

The presence of CMBs significantly reduced the likelihood of achieving functional independence post-EVT in AIS-LVO patients. However, CMBs did not impact the rates of successful revascularization, mortality, or the occurrence of various hemorrhagic events. Future research should explore the mechanisms of this association and strategies to mitigate its impact.

The Venular Side of Cerebral Amyloid Angiopathy: Proof of Concept of a Neglected Issue

Small vessel diseases (SVD) is an umbrella term including several entities affecting small arteries, arterioles, capillaries, and venules in the brain. One of the most relevant and prevalent SVDs is cerebral amyloid angiopathy (CAA), whose pathological hallmark is the deposition of amyloid fragments in the walls of small cortical and leptomeningeal vessels. CAA frequently coexists with Alzheimer's Disease (AD), and both are associated with cerebrovascular events, cognitive impairment, and dementia. CAA and AD share pathophysiological, histopathological and neuroimaging issues. The venular involvement in both diseases has been neglected, although both animal models and human histopathological studies found a deposition of amyloid beta in cortical venules. This review aimed to summarize the available information about venular involvement in CAA, starting from the biological level with the putative pathomechanisms of cerebral damage, passing through the definition of the peculiar angioarchitecture of the human cortex with the functional organization and consequences of cortical arteriolar and venular occlusion, and ending to the hypothesized links between cortical venular involvement and the main neuroimaging markers of the disease.

Relation of MRI-Visible Perivascular Spaces and Other MRI Markers of Cerebral Small Vessel Disease

Perivascular spaces (PVS) visible on brain MRI signal cerebral small vessel disease (CSVD). The coexistence of PVS with other CSVD manifestations likely increases the risk of adverse neurological outcomes. We related PVS to other CSVD manifestations and brain volumes that are markers of vascular brain injury and neurodegeneration. Framingham Heart Study (FHS) participants with CSVD ratings on brain MRI were included. PVS were rated in the basal ganglia (BG) and centrum semiovale (CSO) into grades I-IV and a category reflecting high burden in single or mixed CSO-BG regions. We related PVS to covert brain infarcts (CBI), white matter hyperintensities (WMH), cerebral microbleeds (CMB), total brain, hippocampal, and cortical gray matter volumes using adjusted multivariable regression analyses. In 2454 participants (mean age 54 ± 12 years), we observed that higher PVS burden in both BG and CSO was related to CMB in lobar and deep brain regions and increased WMH. Greater CSO PVS burden was associated with decreased total cortical gray volumes. PVS are associated with ischemic markers of CSVD and neurodegeneration markers. Further studies should elucidate the causality between PVS and other CSVD manifestations.

Design and Harmonization Approach for the Multi-Institutional Neurocognitive Discovery Study (MINDS) of Adult Congenital Heart Disease (ACHD) Neuroimaging Ancillary Study: A Technical Note

Dramatic advances in the management of congenital heart disease (CHD) have improved survival to adulthood from less than 10% in the 1960s to over 90% in the current era, such that adult CHD (ACHD) patients now outnumber their pediatric counterparts. ACHD patients demonstrate domain-specific neurocognitive deficits associated with reduced quality of life that include deficits in educational attainment and social interaction. Our hypothesis is that ACHD patients exhibit vascular brain injury and structural/physiological brain alterations that are predictive of specific neurocognitive deficits modified by behavioral and environmental enrichment proxies of cognitive reserve (e.g., level of education and lifestyle/social habits). This technical note describes an ancillary study to the National Heart, Lung, and Blood Institute (NHLBI)-funded Pediatric Heart Network (PHN) "Multi-Institutional Neurocognitive Discovery Study (MINDS) in Adult Congenital Heart Disease (ACHD)". Leveraging clinical, neuropsychological, and biospecimen data from the parent study, our study will provide structural-physiological correlates of neurocognitive outcomes, representing the first multi-center neuroimaging initiative to be performed in ACHD patients. Limitations of the study include recruitment challenges inherent to an ancillary study, implantable cardiac devices, and harmonization of neuroimaging biomarkers. Results from this research will help shape the care of ACHD patients and further our understanding of the interplay between brain injury and cognitive reserve.

De novo appearance of cerebral microbleeds in community-dwelling older adults. Neuroimaging and clinical correlates

BACKGROUND AND PURPOSE

Prospective studies on cerebral microbleeds (CMB) have departed from individuals who already have CMB at baseline. Therefore, main outcomes have usually been the composite of new lesions appearing on the follow-up among patients who already had CMB together with those who de novo developed CMB. Using the Atahualpa Project Cohort, we aimed to assess correlates of incident CMB in community-dwelling older adults free of CMB at baseline.

METHODS

Atahualpa residents aged ≥ 60 years received baseline clinical interviews and a brain MRI. Those who were free of CMB at baseline and received follow-up brain MRI at the end of the study were included. Multivariate logistic and Poisson regression models were fitted to assess the association and the incidence rate ratio (IRR) of incident CMB according to clinical and neuroimaging variables.

RESULTS

The mean age of 241 study participants was 65.6 ± 6.1 years (57% women). After 6.5 years of follow-up, 25 subjects (10.4%) developed incident CMB. A total of 37 CMB were noticed in these 25 patients. A parsimonious logistic regression model demonstrated an association between the Edmonton Frail Scale (EFS) and incident CMB (p = .043). Multivariate logistic regression models showed an association between WMH progression and incident CMB (p = .011). Using Poisson regression models, the IRR for WMH progression at follow-up was increased in subjects with incident CMB (p = .029).

CONCLUSIONS

Study results show a significant relationship between the EFS, WMH progression, and incident CMB. This knowledge will allow the implementation of preventive policies to reduce incident CMB and its consequences.

[Neuroimaging Characteristics of Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) in Korean Based on Jeju Cohort: A Pictorial Essay]

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small artery vasculopathy caused by mutations in the NOTCH3 gene on chromosome 19. Jeju Island has the highest reported prevalence of CADASIL patients in the world. Even though most studies on the neuroimaging characteristics of CADASIL have focused on Western populations, there are notable differences in Korean CADASIL patients compared to those in Western countries, which may impact their clinical manifestations and prognosis. Herein, this pictorial essay presents the neuroimaging patterns of CADASIL in patients in Korea, with an emphasis on the differences observed from previous reports based on a Western patient population.

Asymmetry of Lacunae between Brain Hemispheres Is Associated with Atherosclerotic Occlusions of Middle Cerebral Artery

Cerebral small vessel disease (CSVD) commonly coexists with intracranial atherosclerotic stenosis (ICAS). Previous studies have tried to evaluate the relationship between ICAS and CSVD; however, they have yielded varied conclusions. Furthermore, the methodology of these studies is not very rigorous, as they have evaluated the association between ICAS and CSVD of bilateral hemispheres rather than the affected hemisphere. Unilateral middle cerebral artery atherosclerotic occlusion (uni-MCAO) is a favorable model to solve this problem.

MATERIAL AND METHODS

Patients with uni-MCAO were retrospectively observed. Imaging characteristics, including lacunae, white matter hyperintensities (WMH), enlarged perivascular spaces (EPVS), and cerebral microbleeds (CMBs), were compared between the hemisphere ipsilateral to the MCAO and the contralateral hemisphere.

RESULTS

A total of 219 patients (median age 57 years; 156 males) were enrolled. Compared with the contralateral side, increased quality of lacunae (median, IQR, 0, 2 vs. 0, 1; p < 0.001) and elevated CSVD score (median, IQR, 0, 1 vs. 0, 1; p = 0.004) were found in the occluded hemisphere. No significant differences were shown for WMH, EPVS, and CMBs.

CONCLUSIONS

Uni-MCAO has a higher prevalence of lacunae in the ipsilateral hemisphere. However, no interhemispheric differences in WMH, EPVS, or CMBs were found.

Basal Ganglia and Brainstem Located Cerebral Microbleeds Contributed to Gait Impairment in Patients with Cerebral Small Vessel Disease

BACKGROUND

The mechanism of gait disorder in patients with cerebral small vessel disease (CSVD) remains unclear. Limited studies have compared the effect of cerebral microbleeds (CMBs) and lacunes on gait disturbance in CSVD patients in different anatomical locations.

OBJECTIVE

To investigate the relationship of quantitative gait parameters with varied anatomically located MRI imaging markers in patients with CSVD.

METHODS

Quantitative gait tests were performed on 127 symptomatic CSVD patients all with diffuse distributed white matter hyperintensities (WMHs). CMBs and lacunes in regard to anatomical locations and burdens were measured. The correlation between CSVD imaging markers and gait parameters was evaluated using general linear model analysis.

RESULTS

Presence of CMBs was significantly associated with stride length (β= -0.098, p = 0.0272) and right step length (β= -0.054, p = 0.0206). Presence of CMBs in basal ganglia (BG) was significantly associated with stride length and step length. Presence of CMBs in brainstem was significantly associated with gait parameters including stride length, step length, step height, and step width. Presence of lacunes in brainstem was significantly associated with gait speed (β= -0.197, p = 0.0365). However, presence of lacunes in the other areas was not associated with worse gait performances.

CONCLUSION

BG and brain stem located CMBs contributed to gait impairment in symptomatic CSVD patients.

Vascular contributions to Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia and is characterized by progressive neurodegeneration and cognitive decline. Understanding the pathophysiology underlying AD is paramount for the management of individuals at risk of and suffering from AD. The vascular hypothesis stipulates a relationship between cardiovascular disease and AD-related changes although the nature of this relationship remains unknown. In this review, we discuss several potential pathological pathways of vascular involvement in AD that have been described including dysregulation of neurovascular coupling, disruption of the blood brain barrier, and reduced clearance of metabolite waste such as beta-amyloid, a toxic peptide considered the hallmark of AD. We will also discuss the two-hit hypothesis which proposes a 2-step positive feedback loop in which microvascular insults precede the accumulation of Aß and are thought to be at the origin of the disease development. At neuroimaging, signs of vascular dysfunction such as chronic cerebral hypoperfusion have been demonstrated, appearing early in AD, even before cognitive decline and alteration of traditional biomarkers. Cerebral small vessel disease such as cerebral amyloid angiopathy, characterized by the aggregation of Aß in the vessel wall, is highly prevalent in vascular dementia and AD patients. Current data is unclear whether cardiovascular disease causes, precipitates, amplifies, precedes, or simply coincides with AD. Targeted imaging tools to quantitatively evaluate the intracranial vasculature and longitudinal studies in individuals at risk for or in the early stages of the AD continuum could be critical in disentangling this complex relationship between vascular disease and AD.

Neuropathology of microbleeds in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)

Cerebral microbleeds (CMBs) detected on magnetic resonance imaging are common in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). The neuropathologic correlates of CMBs are unclear. In this study, we characterized findings relevant to CMBs in autopsy brain tissue of 8 patients with genetically confirmed CADASIL and 10 controls within the age range of the CADASIL patients by assessing the distribution and extent of hemosiderin/iron deposits including perivascular hemosiderin leakage (PVH), capillary hemosiderin deposits, and parenchymal iron deposits (PID) in the frontal cortex and white matter, basal ganglia and cerebellum. We also characterized infarcts, vessel wall thickening, and severity of vascular smooth muscle cell degeneration. CADASIL subjects had a significant increase in hemosiderin/iron deposits compared with controls. This increase was principally seen with PID. Hemosiderin/iron deposits were seen in the majority of CADASIL subjects in all brain areas. PVH was most pronounced in the frontal white matter and basal ganglia around small to medium sized arterioles, with no predilection for the vicinity of vessels with severe vascular changes or infarcts. CADASIL subjects have increased brain hemosiderin/iron deposits but these do not occur in a periarteriolar distribution. Pathogenesis of these lesions remains uncertain.

Implications of quantitative susceptibility mapping at 7 Tesla MRI for microbleeds detection in cerebral small vessel disease

Background

Cerebral microbleeds (MBs) are a hallmark of cerebral small vessel disease (CSVD) and can be found on T2*-weighted sequences on MRI. Quantitative susceptibility mapping (QSM) is a postprocessing method that also enables MBs identification and furthermore allows to differentiate them from calcifications.

Aims

We explored the implications of using QSM at submillimeter resolution for MBs detection in CSVD.

Methods

Both 3 and 7 Tesla (T) MRI were performed in elderly participants without MBs and patients with CSVD. MBs were quantified on T2*-weighted imaging and QSM. Differences in the number of MBs were assessed, and subjects were classified in CSVD subgroups or controls both on 3T T2*-weighted imaging and 7T QSM.

Results

48 participants [mean age (SD) 70.9 (8.8) years, 48% females] were included: 31 were healthy controls, 6 probable cerebral amyloid angiopathy (CAA), 9 mixed CSVD, and 2 were hypertensive arteriopathy [HA] patients. After accounting for the higher number of MBs detected at 7T QSM (Median = Mdn; Mdn7T−QSM = 2.5; Mdn3T−T2 = 0; z = 4.90; p &lt; 0.001) and false positive MBs (6.1% calcifications), most healthy controls (80.6%) demonstrated at least one MB and more MBs were discovered in the CSVD group.

Conclusions

Our observations suggest that QSM at submillimeter resolution improves the detection of MBs in the elderly human brain. A higher prevalence of MBs than so far known in healthy elderly was revealed.

Classification of white matter lesions and characteristics of small vessel disease markers

OBJECTIVES

Radiological markers for cerebral small vessel disease (SVD) may have different biological underpinnings in their development. We attempted to categorize SVD burden by integrating white matter signal abnormalities (WMSA) features and secondary presence of lacunes, microbleeds, and enlarged perivascular spaces.

METHODS

Data were acquired from 610 older adults (aged > 40 years) who underwent brain magnetic resonance imaging exam as part of a health checkup. The WMSA were classified individually by the number and size of non-contiguous lesions, distribution, and contrast. Age-detrended lacunes, microbleeds, and enlarged perivascular space were quantified to further categorize individuals. Clinical and laboratory values were compared across the individual classes.

RESULTS

Class I was characterized by multiple, small, deep WMSA but a low burden of lacunes and microbleeds; class II had large periventricular WMSA and a high burden of lacunes and microbleeds; and class III had limited juxtaventricular WMSA and lacked lacunes and microbleeds. Class II was associated with older age, diabetes, and a relatively higher neutrophil-to-lymphocyte ratio. Smoking and higher uric acid levels were associated with an increased risk of class I.

CONCLUSION

The heterogeneity of SVD was categorized into three classes with distinct clinical correlates. This categorization will improve our understanding of SVD pathophysiology, risk stratification, and outcome prediction.

KEY POINTS

• Classification of white matter signal abnormality (WMSA) features was associated with different characteristic of lacunes, microbleeds, and enlarged perivascular space and clinical variability. • Class I was characterized by multiple, small, deep WMSA but a low burden of lacunes and microbleeds. Class II had large periventricular WMSA and a high burden of lacunes and microbleeds. Class III had limited juxtaventricular WMSA and lacked lacunes and microbleeds. • Class II was associated with older age, diabetes, and higher neutrophil-to-lymphocyte ratio. Smoking and higher uric acid levels were associated with an increased risk of class I.

Cerebral microbleeds in dementia with Lewy bodies

INTRODUCTION

Cerebral microbleeds (CMB) are associated with cognitive impairment and hypertensive or cerebral amyloid angiopathy. The pathophysiology and clinical significance of CMB in dementia with Lewy bodies (DLB) are not well understood. Our study aimed to investigate the prevalence of CMB in DLB and to estimate the magnitudes of their clinical associations.

METHODS

Twenty participants with DLB (mean age 74 ± 5 years) were included in this cross-sectional study. All participants underwent 3 T magnetic resonance imaging. CMB number and location were assessed on susceptibility-weighted imaging or quantitative susceptibility mapping. Amyloid-beta (Aβ) positron emission tomography (PET) scans were also performed. Between-group comparisons were estimated using risk ratios (RR) for categorical variables, and mean differences or median regression coefficients for continuous variables.

RESULTS

CMB were present in 30% of the DLB participants, with a lobar predominance observed. DLB with CMB were more likely to be on antithrombotic therapy (100%), compared to those without CMB (43%; RR 2.33 [95% CI 1.27, 4.27]). Those with CMB were also more likely to report a history of hypertension (100%) compared to those without (70%; RR 1.75 [95% CI 1.11, 2.75]). DLB core clinical features, cognition and functional status did not differ between the two groups. There was no association found between the presence of CMB and cortical Aβ deposition on PET imaging.

CONCLUSION

CMB are not uncommon in DLB and may be associated with hypertensive small vessel disease. Further studies into the pathophysiology and clinical implications of CMB in DLB are needed.

Using transfer learning for automated microbleed segmentation

INTRODUCTION

Cerebral microbleeds are small perivascular hemorrhages that can occur in both gray and white matter brain regions. Microbleeds are a marker of cerebrovascular pathology and are associated with an increased risk of cognitive decline and dementia. Microbleeds can be identified and manually segmented by expert radiologists and neurologists, usually from susceptibility-contrast MRI. The latter is hard to harmonize across scanners, while manual segmentation is laborious, time-consuming, and subject to interrater and intrarater variability. Automated techniques so far have shown high accuracy at a neighborhood ("patch") level at the expense of a high number of false positive voxel-wise lesions. We aimed to develop an automated, more precise microbleed segmentation tool that can use standardizable MRI contrasts.

METHODS

We first trained a ResNet50 network on another MRI segmentation task (cerebrospinal fluid vs. background segmentation) using T1-weighted, T2-weighted, and T2* MRIs. We then used transfer learning to train the network for the detection of microbleeds with the same contrasts. As a final step, we employed a combination of morphological operators and rules at the local lesion level to remove false positives. Manual segmentation of microbleeds from 78 participants was used to train and validate the system. We assessed the impact of patch size, freezing weights of the initial layers, mini-batch size, learning rate, and data augmentation on the performance of the Microbleed ResNet50 network.

RESULTS

The proposed method achieved high performance, with a patch-level sensitivity, specificity, and accuracy of 99.57, 99.16, and 99.93%, respectively. At a per lesion level, sensitivity, precision, and Dice similarity index values were 89.1, 20.1, and 0.28% for cortical GM; 100, 100, and 1.0% for deep GM; and 91.1, 44.3, and 0.58% for WM, respectively.

DISCUSSION

The proposed microbleed segmentation method is more suitable for the automated detection of microbleeds with high sensitivity.

Number of cerebral microbleeds after intracranial/extracranial stenting and dual antiplatelet therapy

BACKGROUND

Cerebral microbleeds (CMBs) are small (<1 cm) perivascular hemosiderin depositions. They may be visible in T2* or susceptibility-weighted magnetic resonance imaging (MRI) sequences. CMBs may indicate an increased risk of intracerebral hemorrhage (ICH) or vascular disease. Cerebral white matter changes indicate small vessel disease (SVD), which is also related to CMBs. In cerebral vascular treatment, dual antiplatelet therapy (DAPT) is routinely used after stenting. We surveyed our cerebral stenting case series for changes in the number of CMBs.

METHODS

Patients receiving extracranial or intracranial stenting between 2018 and 2020 were included. All patients received DAPT after stenting. Changes in CMBs, SVD degree, and other findings from pretreatment to follow-up MRI were recorded. Differences between stented artery supplying territory and other territories were compared.

RESULTS

The average age of the 75 enrolled patients was 65.37 years ± 11.53 (50 male and 25 female patients); 84 extracranial or intracranial stentings were performed. The average Fazekas scale score was 1.32 ± 0.77. Significantly more CMBs developed in the initial ≥6 CMB group than in the initial 0 and 1-5 CMB groups (7 ± 3.6 vs 0.56 ± 1.06, 1.45 ± 3.32, p < 0.001). No significant difference in increased CMBs was observed between the initial 0 and 1-5 CMB groups. Significantly more CMBs developed in the stented artery supplying territory than elsewhere (0.6 ± 0.13 vs 0.44 ± 0.17, p < 0.05). No ICH was noted in our case series.

CONCLUSION

Preexisting CMB was a risk factor for the onset of new CMBs after stenting and DAPT. Poststenting and DAPT statistically increased CMBs in stented artery supplying territories at short-term follow-up.

[Brain Iron Imaging in Aging and Cognitive Disorders: MRI Approaches]

Iron has a vital role in the human body, including the central nervous system. Increased deposition of iron in the brain has been reported in aging and important neurodegenerative diseases. Owing to the unique magnetic resonance properties of iron, MRI has great potential for in vivo assessment of iron deposition, distribution, and non-invasive quantification. In this paper, we will review the MRI methods for iron assessment and their changes in aging and neurodegenerative diseases, focusing on Alzheimer's disease. In addition, we will summarize the limitations of current approaches and introduce new areas and MRI methods for iron imaging that are expected in the future.

New Insights Into Cerebrovascular Pathophysiology and Hypertension

Despite advances in acute management and prevention of cerebrovascular disease, stroke and vascular cognitive impairment together remain the world's leading cause of death and neurological disability. Hypertension and its consequences are associated with over 50% of ischemic and 70% of hemorrhagic strokes but despite good control of blood pressure (BP), there remains a 10% risk of recurrent cerebrovascular events, and there is no proven strategy to prevent vascular cognitive impairment. Hypertension evolves over the lifespan, from predominant sympathetically driven hypertension with elevated mean BP in early and mid-life to a late-life phenotype of increasing systolic and falling diastolic pressures, associated with increased arterial stiffness and aortic pulsatility. This pattern may partially explain both the increasing incidence of stroke in younger adults as well as late-onset, chronic cerebrovascular injury associated with concurrent systolic hypertension and historic mid-life diastolic hypertension. With increasing arterial stiffness and autonomic dysfunction, BP variability increases, independently predicting the risk of ischemic and intracerebral hemorrhage, and is potentially modifiable beyond control of mean BP. However, the interaction between hypertension and control of cerebral blood flow remains poorly understood. Cerebral small vessel disease is associated with increased pulsatility in large cerebral vessels and reduced reactivity to carbon dioxide, both of which are being targeted in early phase clinical trials. Cerebral arterial pulsatility is mainly dependent upon increased transmission of aortic pulsatility via stiff vessels to the brain, while cerebrovascular reactivity reflects endothelial dysfunction. In contrast, although cerebral autoregulation is critical to adapt cerebral tone to BP fluctuations to maintain cerebral blood flow, its role as a modifiable risk factor for cerebrovascular disease is uncertain. New insights into hypertension-associated cerebrovascular pathophysiology may provide key targets to prevent chronic cerebrovascular disease, acute events, and vascular cognitive impairment.

Cerebral Microbleed Automatic Detection System Based on the “Deep Learning”

Objective

To validate the reliability and efficiency of clinical diagnosis in practice based on a well-established system for the automatic segmentation of cerebral microbleeds (CMBs).

Method

This is a retrospective study based on Magnetic Resonance Imaging-Susceptibility Weighted Imaging (MRI-SWI) datasets from 1,615 patients (median age, 56 years; 1,115 males, 500 females) obtained between September 2018 and September 2019. All patients had been diagnosed with cerebral small vessel disease (CSVD) with clear cerebral microbleeds (CMBs) on MRI-SWI. The patients were divided into training and validation cohorts of 1,285 and 330 patients, respectively, and another 30 patients were used for internal testing. The model training and validation data were labeled layer by layer and rechecked by two neuroradiologists with 15 years of work experience. Afterward, a three-dimensional convolutional neural network (CNN) was applied to the MRI data from the training and validation cohorts to construct a deep learning system (DLS) that was tested with the 72 patients, independent of the aforementioned MRI cohort. The DLS tool was used as a segmentation program for these 72 patients. These results were evaluated and revised by five neuroradiologists and subjected to an output analysis divided into the missed label, incorrect label, and correct label. The interneuroradiologists DLS agreement rate, which was assessed using the interrater agreement kappas test, was used for the quality analysis.

Results

In the detection and segmentation of the CMBs, the DLS achieved a Dice coefficient of 0.72. In the evaluation of the independent clinical data, the neuroradiologists reported that more than 90% of the lesions were directly detected and less than 10% of lesions were incorrectly labeled or the label was missed by our DLS. The kappa value for interneuroradiologist DLS agreement reached 0.79 on average.

Conclusion

Based on the results, the automatic detection and segmentation of CMBs are feasible. The proposed well-trained DLS system might represent a trusted tool for the segmentation and detection of CMB lesions.

New cerebral microbleeds in AF patients on non-vitamin K oral anticoagulants or warfarin: One-year follow-up

Anticoagulant treatment increases the risk of intracerebral hemorrhage (ICH), but whether the treatment, more specifically non-vitamin K oral anticoagulants (NOACs), increases the risk of cerebral microbleeds (CMBs) remains uncertain. We performed this study to investigate the development of new CMBs due to NOACs or warfarin treatment in patients with atrial fibrillation (AF).We prospectively recruited AF patients before anticoagulation from June 2016 to June 2018. We performed susceptibility-weighted imaging (SWI) examinations on all enrolled AF patients and re-examined SWI 1 year later. We compared demographic features and new CMBs between the NOACs group and the warfarin group. Univariate analysis of clinical factors was performed according to the development of new CMBs; and age, a HAS-B(L)ED score, warfarin use, and the presence of baseline CMBs were then selected for inclusion in the multivariate logistic regression model.A total of 72 AF patients were recruited, 29 of whom were assigned to the NOACs group and 43 to the warfarin group. Finally, 1 patient in the NOACs group (3.4%) and 9 patients (20.9%) in the warfarin group developed new CMBs after 1 year follow-up (P = .08). Univariate analysis showed that age, a HAS-B(L)ED score ≥4, the presence of baseline CMBs were associated with the development of new CMBs (P < .05). And multivariate regression analysis showed baseline CMBs (P = .03, odds ratio = 6.37, 95% confidence interval 1.15-35.36) was independently related to the increase in new CMBs.AF patients treated with NOACs may have a decreased trend in the development of new CMBs compared with those treated with warfarin. Baseline CMBs increased the frequency of new CMBs during anticoagulant treatment. The development of new CMBs in AF patients with anticoagulation requires further longitudinal studies with longer follow-up in larger samples.

Detecting Small Vessel Pathology in Cocaine Use Disorder

Background

Cocaine use is associated with an increased risk of cerebrovascular accidents. Small vessel pathology has been linked to the risk of stroke in cocaine users, but can be challenging to detect on conventional magnetic resonance (MR) scans. Fluid-attenuated inversion recovery (FLAIR) scans permit better resolution of small vessel lesions.

Objectives

FLAIR scans are currently only acquired based on the subjective judgement of abnormalities on MR scans at face value. We sought to evaluate this practice and the added value of FLAIR scans for patients with cocaine use disorder (CUD), by comparing microbleeds detected by MR and FLAIR scans. We hypothesised that microbleeds are more pronounced in CUD patients, particularly so in participants who had been selected for a FLAIR scan by radiographers.

Methods

Sixty-four patients with CUD and 60 control participants underwent a brain scan. The MR of 20 CUD patients and 16 control participants showed indicators of cerebral infarction at face value and were followed up by a FLAIR scan. We determined the volume of microbleeds in both MR and FLAIR scans and examined associations with various risk factors.

Results

While MR lesion volumes were significantly increased in CUD patients, no significant differences in lesion volume were found in the subgroup of individuals who received a FLAIR.

Conclusion

The current practice of subjectively evaluating MR scans as a basis for the follow-up FLAIR scans to detect vascular pathology may miss vulnerable individuals. Hence, FLAIR scans should be included as a routine part of research studies.

Neuropathology of Vascular Brain Health: Insights From Ex Vivo Magnetic Resonance Imaging-Histopathology Studies in Cerebral Small Vessel Disease

Sporadic cerebral small vessel disease (SVD) is a major contributor to vascular cognitive impairment and dementia in the aging human brain. On neuropathology, sporadic SVD is characterized by abnormalities to the small vessels of the brain predominantly in the form of cerebral amyloid angiopathy and arteriolosclerosis. These pathologies frequently coexist with Alzheimer disease changes, such as plaques and tangles, in a single brain. Conversely, during life, magnetic resonance imaging (MRI) only captures the larger manifestations of SVD in the form of parenchymal brain abnormalities. There appears to be a major knowledge gap regarding the underlying neuropathology of individual MRI-detectable SVD abnormalities. Ex vivo MRI in postmortem human brain tissue is a powerful tool to bridge this gap. This review summarizes current insights into the histopathologic correlations of MRI manifestations of SVD, their underlying cause, presumed pathophysiology, and associated secondary tissue injury. Moreover, we discuss the advantages and limitations of ex vivo MRI-guided histopathologic investigations and make recommendations for future studies.

Automated Detection of Candidate Subjects With Cerebral Microbleeds Using Machine Learning

Cerebral microbleeds (CMBs) appear as small, circular, well defined hypointense lesions of a few mm in size on T2^*-weighted gradient recalled echo (T2^*-GRE) images and appear enhanced on susceptibility weighted images (SWI). Due to their small size, contrast variations and other mimics (e.g., blood vessels), CMBs are highly challenging to detect automatically. In large datasets (e.g., the UK Biobank dataset), exhaustively labelling CMBs manually is difficult and time consuming. Hence it would be useful to preselect candidate CMB subjects in order to focus on those for manual labelling, which is essential for training and testing automated CMB detection tools on these datasets. In this work, we aim to detect CMB candidate subjects from a larger dataset, UK Biobank, using a machine learning-based, computationally light pipeline. For our evaluation, we used 3 different datasets, with different intensity characteristics, acquired with different scanners. They include the UK Biobank dataset and two clinical datasets with different pathological conditions. We developed and evaluated our pipelines on different types of images, consisting of SWI or GRE images. We also used the UK Biobank dataset to compare our approach with alternative CMB preselection methods using non-imaging factors and/or imaging data. Finally, we evaluated the pipeline's generalisability across datasets. Our method provided subject-level detection accuracy > 80% on all the datasets (within-dataset results), and showed good generalisability across datasets, providing a consistent accuracy of over 80%, even when evaluated across different modalities.

The influence of cerebrovascular disease in dementia with Lewy bodies and Parkinson's disease dementia

INTRODUCTION

Lewy body dementia (LBD), including dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), is a common form of neurodegenerative dementia. The frequency and influence of comorbid cerebrovascular disease is not understood but has potentially important clinical management implications.

METHODS

A systematic literature search was conducted (Medline and Embase) for studies including participants with DLB and/or PDD assessing cerebrovascular lesions (imaging and pathological studies). They included white matter changes, cerebral amyloid angiopathy (CAA), cerebral microbleeds (CMB), macroscopic infarcts, micro-infarcts and intracerebral haemorrhage.

RESULTS

Of 4411 articles, 63 studies were included. Cerebrovascular lesions commonly studied included white matter changes (41 studies) and CMB (18 studies). There was an increased severity of white matter changes on magnetic resonance imaging (visualized as white matter hyperintensities, WMH), but not neuropathology, in LBD compared to PD without dementia and age-matched controls. CMB prevalence in DLB was highly variable but broadly similar to Alzheimer's disease (AD) (0-48%), with a lobar predominance. No relationship was found between large cortical or small subcortical infarcts or intracerebral haemorrhage and presence of LBD.

CONCLUSION

The underlying mechanisms of WMH in LBD require further exploration, as their increased severity in LBD was not supported by neuropathological examination of white matter. CMB in LBD had a similar prevalence as AD. There is a need for larger studies assessing the influence of cerebrovascular lesions on clinical symptoms, disease progression and outcomes.

Assessing cortical cerebral microinfarcts on iron-sensitive MRI in cerebral small vessel disease

Recent studies suggest that a subset of cortical microinfarcts may be identifiable on T2* but invisible on T1 and T2 follow-up images. We aimed to investigate whether cortical microinfarcts are associated with iron accumulation after the acute stage. The RUN DMC - InTENse study is a serial MRI study including individuals with cerebral small vessel disease (SVD). 54 Participants underwent 10 monthly 3 T MRIs, including diffusion-weighted imaging, quantitative R1 (=1/T1), R2 (=1/T2), and R2* (=1/T2*) mapping, from which MRI parameters within areas corresponding to microinfarcts and control region of interests (ROIs) were retrieved within 16 participants. Finally, we compared pre- and post-lesional values with repeated measures ANOVA and post-hoc paired t-tests using the mean difference between lesion and control ROI values. We observed 21 acute cortical microinfarcts in 7 of the 54 participants (median age 69 years [IQR 66-74], 63% male). R2* maps demonstrated an increase in R2* values at the moment of the last available follow-up MRI (median [IQR], 5 [5-14] weeks after infarction) relative to prelesional values (p = .08), indicative of iron accumulation. Our data suggest that cortical microinfarcts are associated with increased R2* values, indicative of iron accumulation, possibly due to microhemorrhages, neuroinflammation or neurodegeneration, awaiting histopathological verification.

Dysfunction of the Blood-brain Barrier in Cerebral Microbleeds: from Bedside to Bench

Cerebral microbleeds (CMBs) are a disorder of cerebral microvessels that are characterized as small (<10 mm), hypointense, round or ovoid lesions seen on T2*-weighted gradient echo MRI. There is a high prevalence of CMBs in community-dwelling healthy older people. An increasing number of studies have demonstrated the significance of CMBs in stroke, dementia, Parkinson's disease, gait disturbances and late-life depression. Blood-brain barrier (BBB) dysfunction is considered to be the event that initializes CMBs development. However, the pathogenesis of CMBs has not yet been clearly elucidated. In this review, we introduce the pathogenesis of CMBs, hypertensive vasculopathy and cerebral amyloid angiopathy, and review recent research that has advanced our understanding of the mechanisms underlying BBB dysfunction and CMBs presence. CMBs-associated risk factors can exacerbate BBB breakdown through the vulnerability of BBB anatomical and functional changes. Finally, we discuss potential pharmacological approaches to target the BBB as therapy for CMBs.

Prevalence and Risk Factors of Silent Cerebral Microbleeds in Patients with Coronary Artery Disease

OBJECTIVES

Cerebral microbleeds (CMBs), which can be detected by gradient-echo T2*-weighted magnetic resonance imaging (MRI), represent small chronic brain hemorrhages caused by structural abnormalities in cerebral small vessels. CMBs are known to be a potential predictor of future stroke, and are associated with age, various cardiovascular risk factors, cognitive impairment, and the use of antithrombotic drugs. Patients with coronary artery disease (CAD) are at potentially high risk of CMBs due to the presence of coexistent conditions. However, little is known about CMBs in patients with CAD. We aimed to identify the factors associated with the presence of CMBs among patients with CAD.

METHODS

We evaluated 356 consecutive patients [mean age, 72 ± 10 years; men = 276 (78%)] with angiographically proven CAD who underwent T2*-weighted brain MRI. The brain MRI was assessed by researchers blinded to the patients' clinical details.

RESULTS

CMBs were found in 128 (36%) patients. Among 356 patients, 119 (33%) had previously undergone percutaneous coronary intervention (PCI), and 26 (7%) coronary artery bypass grafting (CABG). There was no significant relationship between CMBs and sex, hypertension, dyslipidemia, diabetes mellitus, anticoagulation therapy, antiplatelet therapy, or prior PCI. CMBs were significantly associated with advanced age, previous CABG, eGFR, non-HDL cholesterol, carotid artery disease, long-term antiplatelet therapy, and long-term dual antiplatelet therapy (DAPT) using univariate logistic regression analysis. The multivariate logistic regression analysis showed that long-term antiplatelet therapy (odds ratio, 1.73; 95% CI, 1.06 - 2.84; P = 0.03) or long-term DAPT (odds ratio, 2.92; 95% CI, 1.39 - 6.17; P = 0.004) was significantly associated with CMBs after adjustment for confounding variables.

CONCLUSIONS

CMBs were frequently observed in patients with CAD and were significantly associated with long-term antiplatelet therapy, especially long-term DAPT.

Cerebral Microbleeds Load and Long-Term Outcomes in Minor Ischemic Stroke

BACKGROUND AND PURPOSE

The association between the cerebral microbleed (CMB) count and outcomes in ischemic stroke has not been fully clarified. The aim of this study was to investigate the relationship between the CMBs count and functional outcomes in patients with a minor ischemic stroke treated with antiplatelet therapy METHODS: Non-cardiogenic minor ischemic stroke (NIHSS score < 4 on admission) patients who were treated with antiplatelet therapy were enrolled. The patients were divided into four groups based on the number of CMBs (absent, 1, 2-4, and > 4), and their clinical outcomes were compared. A poor outcome was defined as a modified Rankin scale (mRS) score of 3-6 90 days after symptom onset. Logistic regression analysis was performed to evaluate whether the CMBs count contributes to poor outcomes with well-known risk factors such as age, NIHSS score on admission, ischemic stroke recurrence, large artery atherosclerosis stroke subtype, and DWMHs.

RESULTS

A total of 240 patients were enrolled, and their pre mRS scores were matched based on CMB presence. A higher burden of CMBs was linearly correlated with the incidence of poor outcomes (4% in the absent group, 8% in the 1 CMB group, 13% in the 2-4 CMB group, and 20% in the > 4 CMB group, P = 0.002). Multivariate logistic regression analysis showed that CMBs count was one of the independent factor associated with poor outcomes (odds ratio 1.07, 95% confidence interval 1.02-1.12, P = 0.003).

CONCLUSION

The CMBs count contributes independently to poor outcomes in minor ischemic stroke patients treated with antiplatelet therapy.

Amylin Dyshomeostasis Hypothesis: Small Vessel-Type Ischemic Stroke in the Setting of Type-2 Diabetes

Recent histological analyses of human brains show that small vessel-type injuries in the setting of type-2 diabetes colocalize with deposits of amylin, an amyloid-forming hormone secreted by the pancreas. Amylin inclusions are also identified in circulating red blood cells in people with type-2 diabetes and stroke or cardiovascular disease. In laboratory models of type-2 diabetes, accumulation of aggregated amylin in blood and the cerebral microvasculature induces brain microhemorrhages and reduces cerebral blood flow leading to white matter ischemia and neurological deficits. At the cellular level, aggregated amylin causes cell membrane lipid peroxidation injury, downregulation of tight junction proteins, and activation of proinflammatory signaling pathways which, in turn, induces macrophage activation and macrophage infiltration in vascular areas positive for amylin deposition. We review each step of this cascade based on experimental and clinical evidence and propose the hypothesis that systemic amylin dyshomeostasis may underlie the disparity between glycemic control and stroke risk and may be a therapeutic target to reduce the risk of small vessel ischemic stroke in patients with type-2 diabetes.

Cerebral microbleeds in vascular dementia from clinical aspects to host-microbial interaction

Vascular dementia is the second leading cause of dementia after Alzheimer's disease in the elderly population worldwide. Cerebral microbleeds (CMBs) are frequently observed in MRI of elderly subjects and considered as a possible surrogate marker. The number and location of CMBs reflect the severity of diseases and the underlying pathologies may involve cerebral amyloid angiopathy or hypertensive vasculopathy. Accumulating evidence demonstrated the clinicopathological discrepancies of CMBs, the clinical significance of CMBs associated with other MRI markers of cerebral small vessel disease, cognitive impairments, serum, and cerebrospinal fluid biomarkers. Moreover, emerging evidence has shown that genetic factors and gene-environmental interactions might shed light on the underlying etiologies of CMBs, focusing on blood-brain-barrier and inflammation. In this review, we introduce recent genetic and microbiome studies as a cutting-edge approach to figure out the etiology of CMBs through the "microbe-brain-oral axis" and "microbiome-brain-gut axis." Finally, we propose novel concepts, "microvascular matrisome" and "imbalanced proteostasis," which may provide better perspectives for elucidating the pathophysiology of CMBs and future development of therapeutics for vascular dementia using CMBs as a surrogate marker.

Detection of Cerebral Microbleeds With Venous Connection at 7-Tesla MRI

OBJECTIVE

Cerebral microbleeds (MBs) are a common finding in patients with cerebral small vessel disease (CSVD) and Alzheimer disease as well as in healthy elderly people, but their pathophysiology remains unclear. To investigate a possible role of veins in the development of MBs, we performed an exploratory study, assessing in vivo presence of MBs with a direct connection to a vein.

METHODS

7-Tesla (7T) MRI was conducted and MBs were counted on quantitative susceptibility mapping (QSM). A submillimeter resolution QSM-based venogram allowed identification of MBs with a direct spatial connection to a vein.

RESULTS

A total of 51 people (mean age [SD] 70.5 [8.6] years, 37% female) participated in the study: 20 had CSVD (cerebral amyloid angiopathy [CAA] with strictly lobar MBs [n = 8], hypertensive arteriopathy [HA] with strictly deep MBs [n = 5], or mixed lobar and deep MBs [n = 7], 72.4 [6.1] years, 30% female) and 31 were healthy controls (69.4 [9.9] years, 42% female). In our cohort, we counted a total of 96 MBs with a venous connection, representing 14% of all detected MBs on 7T QSM. Most venous MBs (86%, n = 83) were observed in lobar locations and all of these were cortical. Patients with CAA showed the highest ratio of venous to total MBs (19%) (HA = 9%, mixed = 18%, controls = 5%).

CONCLUSION

Our findings establish a link between cerebral MBs and the venous vasculature, pointing towards a possible contribution of veins to CSVD in general and to CAA in particular. Pathologic studies are needed to confirm our observations.

Do Imaging Markers of Cerebral Small Vessel Disease Predict Hematoma Volume and Outcome in Acute Intracerebral Hemorrhage?

BACKGROUND AND PURPOSE

Cerebral small vessel disease (CSVD) markers have not been widely studied in relation to hematoma volume and growth in hypertensive intracerebral hemorrhage (ICH). The objectives to assess the relationship of white matter hyperintense lesions (WMHL), microbleeds (MBs), and cortical siderosis (CSS) with hematoma volume, hematoma expansion (HE), and 3 months outcome in patients with hypertensive ICH.

METHODS

All consecutive acute hypertensive supratentorial ICH presenting to the emergency were prospectively recruited. Baseline and 24 hours computed tomography (CT) to assess hematoma volume and magnetic resonance imaging (MRI) for CSVD markers were performed in all subjects. WMHL (graded using Fazekas's scale), MBs, and CSS were assessed and compared with baseline variables and outcomes. All the images were assessed by an experienced stroke neurologist/neuroradiologist.

RESULTS

One hundred and fifty-seven patients were screened and 60 were included. Mean age was 54.08 ± 11.57 years and 47 (78%) were males. Of 60, 19 (28.1%) had HE, 31 (51.6%) had major bleed (>30 ml), and 28 (47.46%) had poor 3 month outcome (mRS 4-6). On univariate analysis, high grade WMHL was associated with greater HE [odds ratio (OR): 2.65, confidence interval (CI) 1.48-4.72, P = 0.001), greater proportion with volume >30 ml (OR: 7.16, CI: 1.09-47.13, P = 0.001) and poor outcome (OR: 2.1, CI: 0.05-3.27, P = 0.001). MBs were associated with poor outcome (P = 0.029) but not with HE/volume. CSS was related to HE (P = 0.031), a large volume bleed (P = 0.023), and poor outcome (P = 0.021). On multivariate model, only WMHL independently predicted HE (P = 0.034), greater proportion with bleed volume >30 ml (P = 0.041), and poor outcome (P = 0.042).

CONCLUSIONS

WMHL in MRI serves as a predictor of hematoma expansion, a large volume bleed, and poor outcome in hypertensive ICH and may be incorporated into existing prediction models.

Cerebral microbleeds: from depiction to interpretation

Cerebral microbleeds (CMBs) are defined as hypointense foci visible on T2*-weighted and susceptible-weighted MRI sequences. CMBs are increasingly recognised with the widespread use of MRI in healthy individuals as well as in the context of cerebrovascular disease or dementia. They can also be encountered in major critical medical conditions such as in patients requiring extracorporeal mechanical oxygenation. The advent of MRI-guided postmortem neuropathological examinations confirmed that, in the context of cerebrovascular disease, the vast majority of CMBs correspond to recent or old microhaemorrhages. Detection of CMBs is highly influenced by MRI parameters, in particular field strength, postprocessing methods used to enhance T2* contrast and three dimensional sequences. Despite recent progress, harmonising imaging parameters across research studies remains necessary to improve cross-study comparisons. CMBs are helpful markers to identify the nature and the severity of the underlying chronic small vessel disease. In daily clinical practice, presence and numbers of CMBs often trigger uncertainty for clinicians especially when antithrombotic treatments and acute reperfusion therapies are discussed. In the present review, we discuss those clinical dilemmas and address the value of CMBs as diagnostic and prognostic markers for future vascular events.

Quantitative susceptibility mapping of the rat brain after traumatic brain injury

The primary lesion arising from the initial insult after traumatic brain injury (TBI) triggers a cascade of secondary tissue damage, which may also progress to connected brain areas in the chronic phase. The aim of this study was, therefore, to investigate variations in the susceptibility distribution related to these secondary tissue changes in a rat model after severe lateral fluid percussion injury. We compared quantitative susceptibility mapping (QSM) and R₂ * measurements with histological analyses in white and grey matter areas outside the primary lesion but connected to the lesion site. We demonstrate that susceptibility variations in white and grey matter areas could be attributed to reduction in myelin, accumulation of iron and calcium, and gliosis. QSM showed quantitative changes attributed to secondary damage in areas located rostral to the lesion site that appeared normal in R₂ * maps. However, combination of QSM and R₂ * was informative in disentangling the underlying tissue changes such as iron accumulation, demyelination, or calcifications. Therefore, combining QSM with R₂ * measurement can provide a more detailed assessment of tissue changes and may pave the way for improved diagnosis of TBI, and several other complex neurodegenerative diseases.

Longitudinal Magnetic Resonance Imaging of Cerebral Microbleeds in Multiple Sclerosis Patients

We hypothesized that cerebral microbleeds (CMBs) in multiple sclerosis (MS) patients will be detected with higher prevalence compared to healthy controls (HC) and that quantitative susceptibility mapping (QSM) will help remove false positives seen in susceptibility weighted imaging (SWI). A cohort of 100 relapsing remitting MS subjects scanned at 3T were used to validate a set of CMB detection guidelines specifically using QSM. A second longitudinal cohort of 112 MS and 25 HCs, also acquired at 3T, was reviewed across two time points. Both cohorts were imaged with SWI and fluid attenuated inversion recovery. Fourteen subjects in the first cohort (14%, 95% CI 8-21%) and twenty-one subjects in the second cohort (18.7%, 95% CI 11-27%) had at least one CMB. The combined information from SWI and QSM allowed us to discern stable CMBs and new CMBs from potential mimics and evaluate changes over time. The longitudinal results demonstrated that longer disease duration increased the chance to develop new CMBs. Higher age was also associated with increased CMB prevalence for MS and HC. We observed that MS subjects developed new CMBs between time points, indicating the need for longitudinal quantitative imaging of CMBs.

Cerebral Microbleeds - To Treat or Not to Treat, That Is the Question: A Case Report With a Note on Its Radiologic Deconstruction and Therapeutic Nuances

With the ubiquity of susceptibility weighted imaging (SWI), cerebral microbleeds (CMBs) are fast becoming a prevalent phenomenon. They are tightly associated with age, neurodegeneration and diverse vascular etiologies. CMBs have a unique radiological signature. Their morphology, number and topology are quite informative. They also pose a therapeutic conundrum, as they are associated with the risk of cerebral hemorrhage. We present the case of an 86-year-old woman who has a vascular dementia, Binswanger's syndrome, and coronary artery disease, who presented with more than five CMBs. We present this case in order to highlight the dilemma of anti-platelet therapy in this group of patients and we demonstrate the cardinal radiologic features of CMBs. We then segue into the pathologic correlates of CMBs and associated risk factors. We finally analyze the risk of anti-platelet therapy in the presence of CMBs, and we unfold the latest data on CMB number and anti-platelet therapy.

A Review of Translational Magnetic Resonance Imaging in Human and Rodent Experimental Models of Small Vessel Disease

Cerebral small vessel disease (SVD) is a major health burden, yet the pathophysiology remains poorly understood with no effective treatment. Since much of SVD develops silently and insidiously, non-invasive neuroimaging such as MRI is fundamental to detecting and understanding SVD in humans. Several relevant SVD rodent models are established for which MRI can monitor in vivo changes over time prior to histological examination. Here, we critically review the MRI methods pertaining to salient rodent models and evaluate synergies with human SVD MRI methods. We found few relevant publications, but argue there is considerable scope for greater use of MRI in rodent models, and opportunities for harmonisation of the rodent-human methods to increase the translational potential of models to understand SVD in humans. We summarise current MR techniques used in SVD research, provide recommendations and examples and highlight practicalities for use of MRI SVD imaging protocols in pre-selected, relevant rodent models.

Cerebral Small Vessel Disease and Alzheimer's Disease: A Review

Alzheimer's disease (AD) is the most common cause of dementia. Despite this, clear pathophysiology for AD has not been confirmed, and effective treatments are still not available. As AD results in a complex disease process for cognitive decline, various theories have been suggested as the cause of AD. Recently, cerebral small vessel disease (SVD) has been suggested to contribute to the pathogenesis of AD, as well as contributing to vascular dementia. Cerebral SVD refers to a varied group of diseases that affect cerebral small arteries and microvessels. These can be seen as white matter hyperintensities, cerebral microbleeds, and lacunes on magnetic resonance imaging. Data from epidemiological and clinical-pathological studies have found evidence of the relationship between cerebral SVD and AD. This review aims to discuss the complex relationship between cerebral SVD and AD. Recent reports that evaluate the association between these diseases will be reviewed.

Small vessel disease lesion type and brain atrophy: The role of co-occurring amyloid

INTRODUCTION

It is unknown whether different types of small vessel disease (SVD), differentially relate to brain atrophy and if co-occurring Alzheimer's disease pathology affects this relation.

METHODS

In 725 memory clinic patients with SVD (mean age 67 ± 8 years, 48% female) we compared brain volumes of those with moderate/severe white matter hyperintensities (WMHs; n = 326), lacunes (n = 132) and cerebral microbleeds (n = 321) to a reference group with mild WMHs (n = 197), also considering cerebrospinal fluid (CSF) amyloid status in a subset of patients (n = 488).

RESULTS

WMHs and lacunes, but not cerebral microbleeds, were associated with smaller gray matter (GM) volumes. In analyses stratified by CSF amyloid status, WMHs and lacunes were associated with smaller total brain and GM volumes only in amyloid-negative patients. SVD-related atrophy was most evident in frontal (cortical) GM, again predominantly in amyloid-negative patients.

DISCUSSION

Amyloid status modifies the differential relation between SVD lesion type and brain atrophy in memory clinic patients.