Familial aneurysmal subarachnoid hemorrhage: a community-based study

Genetic Overlap of Thoracic Aortic Aneurysms and Intracranial Aneurysms

OBJECTIVE

Thoracic aortic aneurysms (TAAs) and intracranial aneurysms (ICAs) share overlapping genetic and pathophysiological mechanisms, yet the genetic interplay between these conditions remains insufficiently explored. This study aimed to identify common genetic factors underlying TAA and ICA.

METHODS

A comprehensive review of genome-wide association studies (GWASs) and retrospective clinical studies was conducted using PubMed, Orbis, and Web of Science. Articles addressing the genetic etiologies of TAA and ICA were analyzed. Separate lists of causative genes were compiled, and commonalities were identified. A Venn diagram was constructed to illustrate genetic overlap and shared physiological pathways.

RESULTS

We identified 24 overlapping genes associated with TAA and ICA, including LTBP2, TGFB2, TGFB3, TGFBR1, TGFBR2, SMAD2, SMAD3, COL1A2, COL3A1, COL4A1, COL5A1, COL5A2, FBN1, FBN2, ELN, LOX ACTA2, MYH11, MYLK, ABCC6, NOTCH1, MED12, PKD1, and PKD2. These genes are involved in pathways related to connective tissue biology, contractile elements, extracellular matrix components, and transforming growth factor-β signaling. While vascular endothelium and cell cycle pathways were unique to ICA, TAA pathways predominantly involved extracellular matrix remodeling.

CONCLUSIONS

This study highlights the significant genetic overlap between TAA and ICA, shedding light on shared molecular mechanisms. These findings underscore the importance of interdisciplinary awareness: neurologists, neurosurgeons, and neurointerventional radiologists should monitor ICA patients for potential TAA, while cardiologists, cardiac surgeons, vascular surgeons, and vascular interventionalists should consider ICA risks in TAA patients. Further research into these genetic pathways could enhance the understanding and management of both conditions.

Unruptured cerebral aneurysm risk stratification: Background, current research, and future directions in aneurysm assessment

Background:

The optimal management of unruptured cerebral aneurysms is widely debated in the medical field. Rapid technology advances, evolving understanding of underlying pathophysiology, and shifting practice patterns have made the cerebrovascular field particularly dynamic in recent years. Despite progress, there remains a dearth of large randomized studies to help guide the management of these controversial patients.

Methods:

We review the existing literature on the natural history of unruptured cerebral aneurysms and highlight ongoing research aimed at improving our ability to stratify risk in these patients.

Results:

Landmark natural history studies demonstrated the significance of size, location, and other risk factors for aneurysm rupture, but prior studies have significant limitations. We have begun to understand the underlying pathophysiology behind aneurysm formation and rupture and are now applying new tools such as flow dynamics simulations and machine learning to individualize rupture risk stratification.

Conclusion:

Prior studies have identified several key risk factors for aneurysmal rupture, but have limitations. New technology and research methods have enabled us to better understanding individual rupture risk for patients with unruptured cerebral aneurysms.

PPIL4 is essential for brain angiogenesis and implicated in intracranial aneurysms in humans

Intracranial aneurysm (IA) rupture leads to subarachnoid hemorrhage, a sudden-onset disease that often causes death or severe disability. Although genome-wide association studies have identified common genetic variants that increase IA risk moderately, the contribution of variants with large effect remains poorly defined. Using whole-exome sequencing, we identified significant enrichment of rare, deleterious mutations in PPIL4, encoding peptidyl-prolyl cis-trans isomerase-like 4, in both familial and index IA cases. Ppil4 depletion in vertebrate models causes intracerebral hemorrhage, defects in cerebrovascular morphology and impaired Wnt signaling. Wild-type, but not IA-mutant, PPIL4 potentiates Wnt signaling by binding JMJD6, a known angiogenesis regulator and Wnt activator. These findings identify a novel PPIL4-dependent Wnt signaling mechanism involved in brain-specific angiogenesis and maintenance of cerebrovascular integrity and implicate PPIL4 gene mutations in the pathogenesis of IA.

Preventive screening for intracranial aneurysms

Background

Subarachnoid hemorrhage from rupture of an intracranial aneurysm (aneurysmal subarachnoid hemorrhage) is a devastating subset of stroke. Since brain damage from the initial hemorrhage is a major cause for the poor outcome after aneurysmal subarachnoid hemorrhage, prevention of aneurysmal subarachnoid hemorrhage has the highest potential to prevent poor outcome from aneurysmal subarachnoid hemorrhage.

Aim

In this review, we describe the groups at high risk of aneurysmal subarachnoid hemorrhage who may benefit from preventive screening for unruptured intracranial aneurysms followed by preventive treatment of unruptured intracranial aneurysms found. Furthermore, we describe the advantages and disadvantages of screening and advise how to perform counseling on screening.

Summary of review

Modeling studies show that persons with two or more affected first-degree relatives with aneurysmal subarachnoid hemorrhage and patients with autosomal dominant polycystic kidney disease (ADPKD) are candidates for screening for unruptured intracranial aneurysms. One modeling study also suggests that persons with only one affected first-degree relative with aneurysmal subarachnoid hemorrhage are also likely candidates for screening. Another group who may benefit from screening are persons ≥35 years who smoke(d) and are hypertensive, given their high lifetime risk of aneurysmal subarachnoid hemorrhage of up to 7%, but the prevalence of unruptured intracranial aneurysms in such persons and the efficiency and cost-effectiveness of screening in this group are not yet known. The ultimate goal of screening is to increase the number of quality years of life of the screening candidates, and therefore the benefits but also many downsides of screening –such as risk of incidental findings, very small unruptured intracranial aneurysms that require regular follow-up, preventive treatment with inherent risk of complications and anxiety – should be discussed with the candidate so that an informed decision can be made before intracranial vessels are imaged.

Conclusions

Several groups of persons who may benefit from screening have been identified, but since these constitute only a minority of all aneurysmal subarachnoid hemorrhage patients, additional high-risk groups still need to be identified. Further research is also needed to identify persons at low or high risk of aneurysmal development and rupture within the groups identified thus far to improve the efficiency of screening. Moreover, if new medical treatment strategies that can reduce the risk of rupture of unruptured intracranial aneurysm become available, the groups of persons who may benefit from screening could increase considerably.

The association of CDKN2BAS gene polymorphisms and intracranial aneurysm: A meta-analysis

Intracranial aneurysm (IA) is one of the main causes of subarachnoid hemorrhage (SAH) leading to a high percentage of disability and mortality worldwide. In addition to environmental factors, the risk of rupture or prognosis of intracranial aneurysm is also closely related to gene. Thus, a lot of genetic studies have been used to explore associated risk genes as well as variant loci of intracranial aneurysm and found several chromosome variates including 9p21.3 (CDKN2BAS) related to Intracranial aneurysm. However, due to differences in population and the existence of SNP, it is still not determined that whether these genetic changes can be identified as independent risk factors for intracranial aneurysm. Therefore, we performed a meta-analysis of CDKN2BAS SNPs to explore its association with intracranial aneurysms and the results show a significance relation between rs10757272, rs1333040, and rs6475606 with intracranial aneurysm. This will open a new perspective for future intracranial aneurysm gene research and therapy.

Multiple flow-related intracranial aneurysms in the setting of contralateral carotid occlusion: Coincidence or association?

The prevalence of intracranial aneurysms (IAs) is higher in patients with internal carotid artery (ICA) stenosis, likely due to alterations in intracranial hemodynamics. Severe stenosis or occlusion of one ICA may result in increased demand and altered hemodynamics in the contralateral ICA, thus increasing the risk of contralateral IA formation. In this article, we discuss a relevant case and a comprehensive literature review as it pertains to the association of ICA stenosis and IA. Our patient was a 50-year-old female with a chronic asymptomatic right ICA occlusion who presented with diffuse subarachnoid hemorrhage. Emergent angiography revealed left-sided A1-A2 junction, paraclinoid, left middle cerebral artery (MCA) bifurcation, and left anterior temporal artery aneurysms. Brisk filling of the right anterior circulation through the anterior communicating artery was also identified, signifying increased demand on the left ICA circulation. Complete obliteration of all aneurysms was achieved with coil embolization and clipping. For our literature review, we searched the PubMed and EMBASE databases for case reports and case series, as well as references in previously published review articles that described patients with concurrent aneurysms and ICA stenosis. We selected articles that provided adequate information about the case presentations to compare aneurysm and patient characteristics. Our review revealed a higher number of patients with multiple aneurysms contralateral (25%) to rather than ipsilateral to (6%), the ICA stenosis. We discuss the pathogenesis and management of multiple flow-related IA in the context of the existing literature related to concurrent ICA stenosis and IA.

Exome sequencing study revealed novel susceptibility loci in subarachnoid hemorrhage (SAH)

Aim

To expand our current understanding of the genetic basis of subarachnoid hemorrhage (SAH), and reveal the susceptibility genes in SAH risk.

Methods

We conducted whole-exome sequencing (WES) in a cohort of 196 individuals, including 94 SAH patients and 94 controls, as well as 8 samples that belong to two pedigrees. Systematically examination for rare variations (through direct genotyping) and common variations (through genotyping and imputation) for SAHs were performed in this study.

Results

A total of 16,029 single-nucleotide polymorphisms (SNPs) and 108,999 short indels were detected in all samples, and among them, 30 SNPs distributed on 17 genes presented a strong association signal with SAH. Two novel pathogenic gene variants were identified as associated risk loci, including mutation in TPO and PALD1. The statistical analysis for rare, damaging variations in SAHs identified several susceptibility genes which were involved in degradation of the extracellular matrix and transcription factor signal pathways. And 25 putative pathogenic genes for SAH were also identified basic on functional interaction network analysis with the published SAH-associated genes. Additionally, pedigree analysis revealed autosomal dominant inheritance of pathogenic genes.

Conclusion

Systematical analysis revealed a key role for rare variations in SAH risk and discovered SNPs in new complex loci. Our study expanded the list of candidate genes associated with SAH risk, and will facilitate the investigation of disease-related mechanisms and potential clinical therapies.

Higher risk of intracranial aneurysms and subarachnoid haemorrhage in siblings of families with intracranial aneurysms

Introduction

First-degree relatives of patients with familial aneurysmal subarachnoid hemorrhage have an increased risk of unruptured intracranial aneurysms and aneurysmal subarachnoid hemorrhage. We assessed whether the type of kinship of first-degree relatives of aneurysmal subarachnoid hemorrhage patients influences this risk.

Patients and methods

We used all available data from the prospectively collected database of families consulting our outpatient clinic between 1994-2016. We constructed pedigrees for all families with ≥2 first-degree relatives with aneurysmal subarachnoid hemorrhage or unruptured intracranial aneurysms. The proband was defined as the first family member with aneurysmal subarachnoid hemorrhage who sought medical attention. We compared both the proportion of aneurysmal subarachnoid hemorrhage and unruptured intracranial aneurysms in proband's first-degree relatives by calculating relative risks (RR) with children as the reference.

Results

We studied 154 families with 1,105 first-degree relatives of whom 146 had aneurysmalsubarachnoid hemorrhage. Unruptured intracranial aneurysms were identified in 63 (19%) of the 326 screened relatives. Siblings had a higher risk of aneurysmal subarachnoid hemorrhage (RR:1.62, 95% CI:1.12–2.38) and parents a lower risk (RR:0.44, 95% CI:0.24–0.81) than children. Siblings also had a higher risk of unruptured intracranial aneurysms (RR:2.28, 95% CI:1.23–4.07, age-adjusted RR:2.04, 95% CI:1.07–3.92) than children.

Conclusion: Siblings of patients with aneurysmal subarachnoid hemorrhage have a significanthigher risk of both unruptured intracranial aneurysms and aneurysmal subarachnoid hemorrhage and parents have a lower risk of aneurysmal subarachnoid hemorrhage than children.

Discussion: Type of kinship is a relevant factor to consider in risk prediction and screening advice in families with familial aneurysmal subarachnoid hemorrhage.

Intracranial Aneurysms: Pathology, Genetics, and Molecular Mechanisms

Intracranial aneurysms (IA) are local dilatations in cerebral arteries that predominantly affect the circle of Willis. Occurring in approximately 2-5% of adults, these weakened areas are susceptible to rupture, leading to subarachnoid hemorrhage (SAH), a type of hemorrhagic stroke. Due to its early age of onset and poor prognosis, SAH accounts for > 25% of years lost for all stroke victims under the age of 65. In this review, we describe the cerebrovascular pathology associated with intracranial aneurysms. To understand IA genetics, we summarize syndromes with elevated incidence, genome-wide association studies (GWAS), whole exome studies on IA-affected families, and recent research that established definitive roles for Thsd1 (Thrombospondin Type 1 Domain Containing Protein 1) and Sox17 (SRY-box 17) in IA using genetically engineered mouse models. Lastly, we discuss the underlying molecular mechanisms of IA, including defects in vascular endothelial and smooth muscle cells caused by dysfunction in mechanotransduction, Thsd1/FAK (Focal Adhesion Kinase) signaling, and the Transforming Growth Factor β (TGF-β) pathway. As illustrated by THSD1 research, cell adhesion may play a significant role in IA.

Patient and aneurysm characteristics in familial intracranial aneurysms. A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Patient and aneurysm characteristics have been reported to differ between patients with familial and non-familial intracranial aneurysms (IAs), although results are inconsistent. We systematically reviewed and meta-analyzed the literature to identify and quantify patient- and aneurysm characteristics associated with familial IAs.

METHODS

We searched PubMed and EMBASE for case-control and cohort studies comparing patient- and aneurysm characteristics between familial and non-familial IAs. Two observers independently assessed study eligibility and appraised quality with the Newcastle Ottawa Scale. With univariable weighted linear regression analysis we calculated β-coefficients with corresponding 95% confidence intervals (CIs) for ruptured and unruptured IAs combined and for ruptured IAs only. Heterogeneity was assessed with Higgins I2.

RESULTS

A total of 15 articles were included in the meta-analysis in which 16,346 patients were analyzed with a total of 14,225 IAs. For ruptured and unruptured IAs combined, multiple IAs were more prevalent in familial (28.5%) than in non-familial IAs (20.4%; β = 0.10, 95% CI, 0.04 to 0.16; I2 0%). For ruptured IAs only, in familial patients IAs were more prevalent on the middle cerebral artery (41.1% versus 29.5%; β = 0.12, 95% CI, 0.01 to 0.24; I2 12%) and ruptured at a younger age (46.5 years versus 50.8 years; β = -5.00, 95% CI, -9.31 to -0.69; I2 98%) than in non-familial patients. No significant differences were found for the proportion of women, size of the aneurysm at time of rupture, smoking or hypertension.

CONCLUSION

These results suggest that characteristics of familial and non-familial IAs show considerable overlap, yet differ on specific aspects. However, results for age at rupture showed considerable heterogeneity. These findings should be taken into consideration for future etiological research into IAs.

Matrix metalloproteinase-9 gene polymorphisms and their interaction with environment on subarachnoid hemorrhage risk

The current study aimed to investigate the relations of three single nucleotide polymorphisms of matrix metalloproteinase-9 gene, and single nucleotide polymorphisms-smoking interaction to subarachnoid hemorrhage risk. The optimal pattern of the interaction among single nucleotide polymorphisms and smoking was selected by generalized multifactor dimensionality reduction. The association between the three single nucleotide polymorphisms within the matrix metalloproteinase-9 gene was analyzed by logistic regression test. As well as genetic risk of subarachnoid hemorrhage interactions with smoking, the risk of subarachnoid hemorrhage in carriers with the rs3918242 (T) was significantly higher than in carriers carrying CC (genotype: CT + TT vs. CC), adjusted OR (95% CI) = 1.58 (1.25-2.03), and in carriers carrying rs17576- (genotype: AG + GG vs. AA), adjust OR (95% CI) = 1.62 (1.19-2.13). However, after adjusting for covariates, we did not find any direct association between rs17577 and subarachnoid hemorrhage risk. The generalized multifactor dimensionality reduction model shows a potential relation between rs3918242 and smoking risk for subarachnoid hemorrhage ( P = 0.0010). After covariates adjustment, current smokers with rs3918242-CT or TT genotype, compared to never-smokers with rs3918242-CC genotype, OR (95% CI) = 2.57 (1.74-3.46), have a higher subarachnoid hemorrhage risk. Our study showed that the rs3918242 (T) and rs17576 (G), the cross reaction between rs3918242 and smoking increased the risk of subarachnoid hemorrhage. Impact statement Matrix metalloproteinase-9 ( MMP-9) is a possible candidate gene for some diseases, including metabolic syndrome, stroke, coronary artery disease (CAD). But to date, limited data focused on the relationship between MMP-9 gene SNPs and SAH susceptibility. The purpose of this study was to evaluate SNPs of MMP-9 gene and their interaction with environmental factors with SAH risk based on a Chinese population.

Cerebrovascular disorders associated with genetic lesions

Cerebrovascular disorders are underlain by perturbations in cerebral blood flow and abnormalities in blood vessel structure. Here, we provide an overview of the current knowledge of select cerebrovascular disorders that are associated with genetic lesions and connect genomic findings with analyses aiming to elucidate the cellular and molecular mechanisms of disease pathogenesis. We argue that a mechanistic understanding of genetic (familial) forms of cerebrovascular disease is a prerequisite for the development of rational therapeutic approaches, and has wider implications for treatment of sporadic (non-familial) forms, which are usually more common.

Radiographic and microsurgical characteristics of proximal (A1) segment aneurysms of the anterior cerebral artery

BACKGROUND

Proximal A1 segment aneurysms of the anterior cerebral artery (ACA) radiologically resemble internal carotid artery bifurcation (ICBIF) aneurysms because of their anatomical proximity. However, proximal A1 aneurysms exhibit distinguishing features, relative to ICBIF aneurysms. We report our experience of managing proximal A1 aneurysms, then compare them to ICBIF aneurysms.

METHODS

Among 2191 aneurysms treated between 2000 and 2016 in a single institution, we retrospectively reviewed 100 cases categorized as ICBIF or A1 aneurysms. We included aneurysms originating from the ICBIF and ACA, proximal to the anterior communicating artery (A1 segment) and divided them into two groups: proximal A1 (n = 32) and ICBIF (n = 50). If any portion of the aneurysm involved the ICBIF, it was classified as ICBIF. Aneurysms wholly located in the A1 segment were classified as proximal A1. Patient factors and angiographic factors were evaluated and compared.

RESULTS

The proximal A1 group exhibited differences in aneurysm size (p = 0.013), posterior aneurysm direction (p = 0.001), and A1 perforators as incorporating vessels (p = 0.001). The proximal A1 group tended to rupture more frequently when the aneurysm was smaller (p = 0.046). One case of morbidity occurred in the proximal A1 group.

CONCLUSION

Compared to ICBIF aneurysms, proximal A1 aneurysms were smaller and directed posteriorly, with incorporating perforators. Because of these characteristics, it may be difficult to perform clipping with 360° view in microsurgical field. Therefore, when planning to treat proximal A1 aneurysms, different treatment strategies may be necessary, relative to those used for ICBIF aneurysms.

Korean Clinical Practice Guidelines for Aneurysmal Subarachnoid Hemorrhage

Despite advancements in treating ruptured cerebral aneurysms, an aneurysmal subarachnoid hemorrhage (aSAH) is still a grave cerebrovascular disease associated with a high rate of morbidity and mortality. Based on the literature published to date, worldwide academic and governmental committees have developed clinical practice guidelines (CPGs) to propose standards for disease management in order to achieve the best treatment outcomes for aSAHs. In 2013, the Korean Society of Cerebrovascular Surgeons issued a Korean version of the CPGs for aSAHs. The group researched all articles and major foreign CPGs published in English until December 2015 using several search engines. Based on these articles, levels of evidence and grades of recommendations were determined by our society as well as by other related Quality Control Committees from neurointervention, neurology and rehabilitation medicine. The Korean version of the CPGs for aSAHs includes risk factors, diagnosis, initial management, medical and surgical management to prevent rebleeding, management of delayed cerebral ischemia and vasospasm, treatment of hydrocephalus, treatment of medical complications and early rehabilitation. The CPGs are not the absolute standard but are the present reference as the evidence is still incomplete, each environment of clinical practice is different, and there is a high probability of variation in the current recommendations. The CPGs will be useful in the fields of clinical practice and research.

A Novel Association between Lysyl Oxidase Gene Polymorphism and Intracranial Aneurysm in Koreans

PURPOSE

Lysyl oxidase (LOX) controls the cross-linking and maturation of elastin and collagen fibers. In this study, we investigated the association between LOX gene polymorphisms and intracranial aneurysm (IA) formation in a homogeneous Korean population.

MATERIALS AND METHODS

This cross-sectional study involved 80 age-sex matched patients with IA and controls. Fisher's exact test was performed to analyze allelic associations between ten single nucleotide polymorphisms (SNPs) and IA, including 41 ruptured and 39 unruptured cases. Haplotype-specific associations were analyzed using the omnibus test estimating asymptotic chi-square statistics.

RESULTS

Of ten SNPs, three SNPs (rs2303656, rs3900446, and rs763497) were significantly associated with IA (p<0.01). The C allele of rs3900446 was significantly related to increased IA risk with a significant threshold [odds ratio (OR)=20.15, p=4.8×10⁻⁵]. Meanwhile, the A allele of rs2303656 showed a preventive effect against IA formation (p=8.2×10⁻⁴). Seventeen of 247 haplotype structures showed a suggestive association with IA (asymptotic p<0.001). Of ten SNP haplotype combinations, the CG combination of rs3900446 and rs763497 reached Bonferroni-adjusted significant threshold in IA patients (minor haplotype frequency=0.113, asymptotic p=1.3×10⁻⁵). However, there was no association between aneurysm rupture and the LOX gene.

CONCLUSION

This preliminary study indicated that LOX gene polymorphisms, such as rs2303656, rs3900446, and rs763497, may play crucial roles in IA formation in the Korean population. Our novel findings need to be validated in a large-scale independent population.

Collagen Type I Alpha 2 (COL1A2) Polymorphism Contributes to Intracranial Aneurysm Susceptibility: A Meta-Analysis

Background

COL1A2, which encodes collagen type I alpha2, has long been suggested to be a potential positional and functional candidate gene for intracranial aneurysm. We performed a meta-analysis to assess the association between COL1A2 rs42524 polymorphism and the risk of intracranial aneurysm.

Material/Methods

We conducted a systematic search for relevant literature from the following databases up to 22 July 2016: PubMed, Embase, Web of Science, and China National Knowledge Infrastructure. The strength of association between gene and disease was estimated using odds ratios (ORs) with 95% confidence intervals (CIs) under 5 genetic models.

Results

A total of 6 qualified studies were enrolled in this meta-analysis. Pooling results indicated a significant association between COL1A2 rs42524 polymorphism and intracranial aneurysm risk under 4 genetic models (C vs. G: OR=1.74, 95%CI=1.34–2.26; GC vs. GG: OR=1.81, 95%CI=1.37–2.41; CC+GC vs. GG: OR=1.74, 95%CI=1.28–2.36; CC vs. GC+GG: OR=1.76, 95%CI=1.02–3.04). This association was still robust when stratified by ethnicity, intracranial aneurysm type, or Hardy-Weinberg Equilibrium, which was stronger in Asian than in Caucasians. No publication bias was observed.

Conclusions

This meta-analysis suggests COL1A2 rs42524 is a significant risk factor for IA susceptibility, with an especially strong effect in Asian people. Further larger-scale epidemiological studies among different ethnicities are warranted to confirm our findings.

Unruptured intracranial aneurysms: An updated review of current concepts for risk factors, detection and management

The management of patients with unruptured intracranial aneurysms (UIAs) is a complex clinical challenge and constitutes an immense field of research. While a preponderant proportion of these aneurysms never rupture, the consequences of such an event are severe and represent an important healthcare problem. To date, however, the natural history of UIAs is not completely understood and there is no accurate means to discriminate the UIAs that will rupture from those that will not. Yet, a good understanding of the recent evidence and future perspectives is needed when advising a patient with IA to tailor any information to the given patient's level of risk and psychoaffective status. Thus, this review addresses the current concepts of epidemiology, risk factors, detection and management of UIAs.

THSD1 (Thrombospondin Type 1 Domain Containing Protein 1) Mutation in the Pathogenesis of Intracranial Aneurysm and Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

A ruptured intracranial aneurysm (IA) is the leading cause of a subarachnoid hemorrhage. This study seeks to define a specific gene whose mutation leads to disease.

METHODS

More than 500 IA probands and 100 affected families were enrolled and clinically characterized. Whole exome sequencing was performed on a large family, revealing a segregating THSD1 (thrombospondin type 1 domain containing protein 1) mutation. THSD1 was sequenced in other probands and controls. Thsd1 loss-of-function studies in zebrafish and mice were used for in vivo analyses and functional studies performed using an in vitro endothelial cell model.

RESULTS

A nonsense mutation in THSD1 was identified that segregated with the 9 affected (3 suffered subarachnoid hemorrhage and 6 had unruptured IA) and was absent in 13 unaffected family members (LOD score 4.69). Targeted THSD1 sequencing identified mutations in 8 of 507 unrelated IA probands, including 3 who had suffered subarachnoid hemorrhage (1.6% [95% confidence interval, 0.8%-3.1%]). These THSD1 mutations/rare variants were highly enriched in our IA patient cohort relative to 89 040 chromosomes in Exome Aggregation Consortium (ExAC) database (P<0.0001). In zebrafish and mice, Thsd1 loss-of-function caused cerebral bleeding (which localized to the subarachnoid space in mice) and increased mortality. Mechanistically, THSD1 loss impaired endothelial cell focal adhesion to the basement membrane. These adhesion defects could be rescued by expression of wild-type THSD1 but not THSD1 mutants identified in IA patients.

CONCLUSIONS

This report identifies THSD1 mutations in familial and sporadic IA patients and shows that THSD1 loss results in cerebral bleeding in 2 animal models. This finding provides new insight into IA and subarachnoid hemorrhage pathogenesis and provides new understanding of THSD1 function, which includes endothelial cell to extracellular matrix adhesion.

A Potential Polymorphism in the Promoter of Let-7 is Associated With an Increased Risk of Intracranial Aneurysm: A Case-Control Study

Let-7 family plays a key role in the progression of atherosclerosis and intracranial aneurysm (IA). We hypothesized that rs10877887 and rs13293512 polymorphisms in the promoters of let-7 family may be associated with the susceptibility of IA. We genotyped the 2 single nucleotide polymorphisms (SNPs) in 305 patients with IA and 401 healthy controls. The rs10877887 was analyzed using a polymerase chain reaction-restriction fragment length polymorphism assay, and the rs13293512 was analyzed using a TaqMan SNP genotyping method. The relative expression of let-7 family was measured in plasma of cases and controls using real-time PCR. We found that the rs13293512CT genotype was associated with a significantly increased risk of developing IA in a heterozygote comparison (adjusted OR = 1.43, 95% CI, 1.00-2.05, P = 0.048) and dominant comparison (adjusted OR = 1.44, 95% CI, 1.02-2.03, P = 0.04). Combined analysis showed that the rs10877887TT and rs13293512CC/CT genotypes had a significantly increased risk of IA (OR = 1.67, 95% CI, 1.04-2.68, P = 0.03). Moreover, the levels of let-7a, let-7d, and let-7f were downregulated in IA patients, and patients with the rs13293512CC/CT genotypes had a lower level of let-7a than those with rs13293512TT genotype (P = 0.03). These findings indicate that the rs13293512CC/CT is a risk factor for the development of IA, possibly because of the genotypes resulting in a lower level of let-7a.

Guidelines for the Management of Patients With Unruptured Intracranial Aneurysms: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association

PURPOSE

The aim of this updated statement is to provide comprehensive and evidence-based recommendations for management of patients with unruptured intracranial aneurysms.

METHODS

Writing group members used systematic literature reviews from January 1977 up to June 2014. They also reviewed contemporary published evidence-based guidelines, personal files, and published expert opinion to summarize existing evidence, indicate gaps in current knowledge, and when appropriate, formulated recommendations using standard American Heart Association criteria. The guideline underwent extensive peer review, including review by the Stroke Council Leadership and Stroke Scientific Statement Oversight Committees, before consideration and approval by the American Heart Association Science Advisory and Coordinating Committee.

RESULTS

Evidence-based guidelines are presented for the care of patients presenting with unruptured intracranial aneurysms. The guidelines address presentation, natural history, epidemiology, risk factors, screening, diagnosis, imaging and outcomes from surgical and endovascular treatment.

Mouse models of intracranial aneurysm

Subarachnoid hemorrhage secondary to rupture of an intracranial aneurysm is a highly lethal medical condition. Current management strategies for unruptured intracranial aneurysms involve radiological surveillance and neurosurgical or endovascular interventions. There is no pharmacological treatment available to decrease the risk of aneurysm rupture and subsequent subarachnoid hemorrhage. There is growing interest in the pathogenesis of intracranial aneurysm focused on the development of drug therapies to decrease the incidence of aneurysm rupture. The study of rodent models of intracranial aneurysms has the potential to improve our understanding of intracranial aneurysm development and progression. This review summarizes current mouse models of intact and ruptured intracranial aneurysms and discusses the relevance of these models to human intracranial aneurysms. The article also reviews the importance of these models in investigating the molecular mechanisms involved in the disease. Finally, potential pharmaceutical targets for intracranial aneurysm suggested by previous studies are discussed. Examples of potential drug targets include matrix metalloproteinases, stromal cell-derived factor-1, tumor necrosis factor-α, the renin-angiotensin system and the β-estrogen receptor. An agreed clear, precise and reproducible definition of what constitutes an aneurysm in the models would assist in their use to better understand the pathology of intracranial aneurysm and applying findings to patients.

Molecular mechanisms of the formation and progression of intracranial aneurysms

Until recently, only a little was understood about molecular mechanisms of the development of an intracranial aneurysm (IA). Recent advancements over the last decade in the field of genetics and molecular biology have provided us a wide variety of evidences supporting the notion that chronic inflammation is closely associated with the pathogenesis of IA development. In the field of genetics, large-scale Genome-wide association studies (GWAS) has identified some IA susceptible loci and genes related to cell cycle and endothelial function. Researches in molecular biology using human samples and animal models have revealed the common pathway of the initiation, progression, and rupture of IAs. IA formation begins with endothelial dysfunction followed by pathological remodeling with degenerative changes of vascular walls. Medical treatments inhibiting inflammatory cascades in IA development are likely to prevent IA progression and rupture. Statins and aspirin are expected to suppress IA progression by their anti-inflammatory effects. Decoy oligodeoxynucleotides (ODNs) inhibiting inflammatory transcription factors such as nuclear factor kappa-B (NF-κB) and Ets-1 are the other promising choice of the prevention of IA development. Further clarification of molecular mechanisms of the formation and progression of IAs will shed light to the pathogenesis of IA development and provide insight into novel diagnostic and therapeutic strategies for IAs.

Gender differences in neurologic emergencies part I: a consensus summary and research agenda on cerebrovascular disease

Cerebrovascular neurologic emergencies including ischemic and hemorrhagic stroke, subarachnoid hemorrhage (SAH), and migraine are leading causes of death and disability that are frequently diagnosed and treated in the emergency department (ED). Although sex and gender differences in neurologic emergencies are beginning to become clearer, there are many unanswered questions about how emergency physicians should incorporate sex and gender into their research initiatives, patient evaluations, and overall management plans for these conditions. After evaluating the existing gaps in the literature, a core group of ED researchers developed a draft of future research priorities. Participants in the 2014 Academic Emergency Medicine consensus conference neurologic emergencies working group then discussed and approved the recommended research agenda using a standardized nominal group technique. Recommendations for future research on the role of sex and gender in the diagnosis, treatment, and outcomes pertinent to ED providers are described for each of three diagnoses: stroke, SAH, and migraine. Recommended future research also includes investigation of the biologic and pathophysiologic differences between men and women with neurologic emergencies as they pertain to ED diagnoses and treatments.

Genome-wide association study of intracranial aneurysm identifies a new association on chromosome 7

BACKGROUND AND PURPOSE

Common variants have been identified using genome-wide association studies which contribute to intracranial aneurysms (IA) susceptibility. However, it is clear that the variants identified to date do not account for the estimated genetic contribution to disease risk.

METHODS

Initial analysis was performed in a discovery sample of 2617 IA cases and 2548 controls of white ancestry. Novel chromosomal regions meeting genome-wide significance were further tested for association in 2 independent replication samples: Dutch (717 cases; 3004 controls) and Finnish (799 cases; 2317 controls). A meta-analysis was performed to combine the results from the 3 studies for key chromosomal regions of interest.

RESULTS

Genome-wide evidence of association was detected in the discovery sample on chromosome 9 (CDKN2BAS; rs10733376: P<1.0×10(-11)), in a gene previously associated with IA. A novel region on chromosome 7, near HDAC9, was associated with IA (rs10230207; P=4.14×10(-8)). This association replicated in the Dutch sample (P=0.01) but failed to show association in the Finnish sample (P=0.25). Meta-analysis results of the 3 cohorts reached statistical significant (P=9.91×10(-10)).

CONCLUSIONS

We detected a novel region associated with IA susceptibility that was replicated in an independent Dutch sample. This region on chromosome 7 has been previously associated with ischemic stroke and the large vessel stroke occlusive subtype (including HDAC9), suggesting a possible genetic link between this stroke subtype and IA.

Gene expression profiles in intracranial aneurysms

In this study, we extracted total RNA from 15 intracranial aneurysms and 17 superficial temporal artery samples, then performed genome-wide expression profiling using the Affymetrix U133 Plus 2.0 GeneChip. Genes that were differentially expressed between intracranial aneurysms and arterial samples were identified using significance analysis for microarrays, and the expression patterns of three randomly-selected genes were verified by real-time polymerase chain reaction analysis. We identified 3 736 differentially-expressed genes out of the 47,000 assayed transcripts. A total of 179 genes showed a >10-fold change in expression between the aneurysms and the arterial samples. Genes involved in the proliferation, migration, and apoptosis of vascular muscle cells, atherosclerosis, extracellular matrix disruption, and inflammatory reactions were associated with the formation of intracranial aneurysms. There were no significant differences in gene expression profile between unruptured and ruptured aneurysms.

Perioperative Cardiac Complications and 30-Day Mortality in Patients Undergoing Intracranial Aneurysmal Surgery With Adenosine-Induced Flow Arrest

BACKGROUND:

Adenosine-induced flow arrest is a technique used to assist in the surgical clipping of complex aneurysms.

OBJECTIVE:

To assess the safety associated with adenosine-assisted intracranial aneurysm surgery.

METHODS:

Medical records of all patients presenting between January 1, 2009, and December 31, 2012, for intracranial aneurysm surgery were analyzed. Patients were divided into 2 groups based on the intraoperative administration of adenosine: the nonadenosine group (n = 262) and the adenosine group (n = 64). The primary outcome compared between groups included a composite of 30-day mortality and incidences of perioperative cardiac complications (perioperative myocardial infarction or perioperative cardiac arrhythmias).

RESULTS:

The study groups were statistically similar except for a difference in the size and location of cerebral aneurysms and the incidence of coronary artery disease. The primary composite outcome occurred in 4.6% and 9.4% of patients in the nonadenosine and adenosine groups, respectively (P = .13). After adjustment for differences in the incidence of coronary artery disease between the 2 groups, the odds of the primary outcome were not significantly different between the groups (adjusted odds ratio = 2.12; 95% confidence interval, 0.76-5.93; P = .15). There were also no significant differences in the durations of hospital and intensive care unit stay between the study groups.

CONCLUSION:

Our results suggest that adenosine-assisted intracranial aneurysm surgery is not associated with an increase in perioperative cardiac complications or mortality in patients with low risk of coronary artery disease and may be considered a safe technique to assist clipping of complex aneurysms.

Factors affecting formation and rupture of intracranial saccular aneurysms

Unruptured intracranial aneurysms represent a decisional challenge. Treatment risks have to be balanced against an unknown probability of rupture. A better understanding of the physiopathology is the basis for a better prediction of the natural history of an individual patient. Knowledge about the possible determining factors arises from a careful comparison between ruptured versus unruptured aneurysms and from the prospective observation and analysis of unbiased series with untreated, unruptured aneurysms. The key point is the correct identification of the determining variables for the fate of a specific aneurysm in a given individual. Thus, the increased knowledge of mechanisms of formation and eventual rupture of aneurysms should provide significant clues to the identification of rupture-prone aneurysms. Factors like structural vessel wall defects, local hemodynamic stress determined also by peculiar geometric configurations, and inflammation as trigger of a wall remodeling are crucial. In this sense the study of genetic modifiers of inflammatory responses together with the computational study of the vessel tree might contribute to identify aneurysms prone to rupture. The aim of this article is to underline the value of a unifying hypothesis that merges the role of geometry, with that of hemodynamics and of genetics as concerns vessel wall structure and inflammatory pathways.

Cerebral aneurysms: formation, progression, and developmental chronology

The prevalence of unruptured intracranial aneurysms (UIAs) in the general population is up to 3%. Existing epidemiological data suggests that only a small fraction of UIAs progress towards rupture over the lifetime of an individual, but the surrogates for subsequent rupture and the natural history of UIAs are discussed very controversially at present. In case of rupture of an UIA, the case fatality is up to 50%, which therefore continues to stimulate interest in the pathogenesis of cerebral aneurysm formation and progression. Actual data on the chronological development of cerebral aneurysm has been especially difficult to obtain and, until recently, the existing knowledge in this respect is mainly derived from animal or mathematical models or short-term observational studies. Here, we review the current data on cerebral aneurysm formation and progression as well as a novel approach to investigate the developmental chronology of cerebral aneurysms.

Endovascular methods for the treatment of intracranial cerebral aneurysms

This article briefly discusses the clinical features, natural history, and epidemiology of intracranial cerebral aneurysms, along with current diagnostic imaging techniques for their detection. The main focus is on the basic techniques used in endovascular coiling of ruptured and nonruptured saccular intracranial cerebral aneurysms. After a discussion of each technique, a short review of the results of each form of treatment is given, concentrating on reported large case series. Specific complications related to the endovascular treatment of saccular intracranial aneurysms are then discussed.

Aneurysm formation in proinflammatory, transgenic haptoglobin 2-2 mice

BACKGROUND

Inflammation and macrophages in particular are believed to play a role in aneurysm formation. The haptoglobin (Hp) 2-2 genotype is associated with a proinflammatory state.

OBJECTIVE

To investigate the role of inflammation in the formation of aneurysms using a murine model of aneurysm formation in transgenic, proinflammatory Hp2-2 mice and wild-type Hp1-1 mice.

METHODS

Carotid artery aneurysms were induced in the left common carotid artery of wild-type Hp1-1 mice and transgenic Hp2-2 mice using elastase to degrade the arterial wall of the common carotid artery and angiotensin II to induce hypertension. There were 4 experimental groups: (1) sham surgery (n = 11); (2) angiotensin II only (n = 10); (3) elastase only (n = 20); and (4) elastase + angiotensin II (n = 20). Aneurysm size was determined by measuring the outer circumference and luminal circumference of the blood vessel. Macrophages that infiltrated the aneurysm wall were quantified by immunohistochemistry. Results were analyzed using 2-way analysis of variance with a Bonferroni post-test.

RESULTS

Aneurysms in Hp2-2 mice were significantly larger than aneurysms in Hp1-1 mice in the setting of vessel wall degradation and hypertension (P = .02 for outer circumference, P = .01 for luminal circumference). Furthermore, the number of macrophages infiltrating the aneurysm wall was significantly increased in Hp2-2 mice (P < .001).

CONCLUSION

Hp2-2 mice formed aneurysms that were significantly larger and had a significantly greater number of macrophages in the aneurysm wall compared with Hp1-1 mice. This suggests that the proinflammatory state associated with the Hp2-2 protein is involved in aneurysm formation and that the Hp genotype may be a useful biomarker in predicting aneurysm progression.

A combination of genetic, molecular and haemodynamic risk factors contributes to the formation, enlargement and rupture of brain aneurysms

Many people carry cerebral aneurysms but are generally unaware of their presence until they rupture, resulting in high morbidity or mortality. The pathogenesis and aetiology of aneurysms are largely unknown; however, a greater understanding, by analysing the genetic, molecular and haemodynamic risk factors involved in the initiation, enlargement, and rupture of aneurysms, could lead to effective prevention, early diagnosis and more effective treatment. The risk of aneurysm is increased by a family history of aneurysms, and amongst certain populations, namely in Japan and Finland. Several other risk factors are documented, including hypertension, smoking, alcohol consumption, and female sex. Studies indicate a higher occurrence of cerebral aneurysms in females compared to males. Oestrogen protects several components within the artery wall, and inhibits some of the inflammatory molecules that could cause aneurysms. At menopause, the oestrogen level decreases and the incidence of aneurysm increases. Haemodynamic stresses have been shown to be involved in the formation, growth and rupture of aneurysms. This is often associated with hypertension, which also increases the risk of aneurysm rupture. When an unruptured aneurysm is detected the decision to treat can be complicated, since only 1-2% of aneurysms eventually rupture. Haemodynamic simulation software offers an effective tool for the consideration of treatment options for patients who carry unruptured aneurysms. The assessment must consider the risks of interventional treatments versus non-interventional management options, such as controlling blood pressure.

A balanced translocation truncates Neurotrimin in a family with intracranial and thoracic aortic aneurysm

BACKGROUND

Balanced chromosomal rearrangements occasionally have strong phenotypic effects, which may be useful in understanding pathobiology. However, conventional strategies for characterising breakpoints are laborious and inaccurate. We present here a proband with a thoracic aortic aneurysm (TAA) and a balanced translocation t(10;11) (q23.2;q24.2). Our purpose was to sequence the chromosomal breaks in this family to reveal a novel candidate gene for aneurysm.

METHODS AND RESULTS

Intracranial aneurysm (IA) and TAAs appear to run in the family in an autosomal dominant manner: After exploring the family history, we observed that the proband's two siblings both died from cerebral haemorrhage, and the proband's parent and parent's sibling died from aortic rupture. After application of a genome-wide paired-end DNA sequencing method for breakpoint mapping, we demonstrate that this translocation breaks intron 1 of a splicing isoform of Neurotrimin at 11q25 in a previously implicated candidate region for IAs and AAs (OMIM 612161).

CONCLUSIONS

Our results demonstrate the feasibility of genome-wide paired-end sequencing for the characterisation of balanced rearrangements and identification of candidate genes in patients with potentially disease-associated chromosome rearrangements. The family samples were gathered as a part of our recently launched National Registry of Reciprocal Balanced Translocations and Inversions in Finland (n=2575), and we believe that such a registry will be a powerful resource for the localisation of chromosomal aberrations, which can bring insight into the aetiology of related phenotypes.

Epidemiology and genetics of intracranial aneurysms

Intracranial aneurysms are acquired lesions (5-10% of the population), a fraction of which rupture leading to subarachnoid hemorrhage with devastating consequences. Until now, the exact etiology of intracranial aneurysms formation remains unclear. The low incidence of subarachnoid hemorrhage in comparison with the prevalence of unruptured IAs suggests that the vast majority of intracranial aneurysms do not rupture and that identifying those at highest risk is important in defining the optimal management. The most important factors predicting rupture are aneurysm size and site. In addition to ambiental factors (smoking, excessive alcohol consumption and hypertension), epidemiological studies have demonstrated a familiar influence contributing to the pathogenesis of intracranial aneurysms, with increased frequency in first- and second-degree relatives of people with subarachnoid hemorrhage. In comparison to sporadic aneurysms, familial aneurysms tend to be larger, more often located at the middle cerebral artery, and more likely to be multiple. Other than familiar occurrence, there are several heritable conditions associated with intracranial aneurysm formation, including autosomal dominant polycystic kidney disease, neurofibromatosis type I, Marfan syndrome, multiple endocrine neoplasia type I, pseudoxanthoma elasticum, hereditary hemorrhagic telangiectasia, and Ehlers-Danlos syndrome type II and IV. The familial occurrence and the association with heritable conditions indicate that genetic factors may play a role in the development of intracranial aneurysms. Genome-wide linkage studies in families and sib pairs with intracranial aneurysms have identified several loci on chromosomes showing suggestive evidence of linkage, particularly on chromosomes 1p34.3-p36.13, 7q11, 19q13.3, and Xp22. For the loci on 1p34.3-p36.13 and 7q11, a moderate positive association with positional candidate genes has been demonstrated (perlecan gene, elastin gene, collagen type 1 A2 gene). Moreover, 3 of the polymorphisms analyzed in 2 genes (endothelial nitric oxide synthase T786C, interleukin-6 G572C, and interleukin-6 G174C) were found to be significantly associated with ruptured/unruptured aneurysms: the endothelial nitric oxide synthase gene single-nucleotide polymorphisms increased the risk, while IL-6 G174C seemed protective. More recently, two genomic loci (endothelin receptor A and cyclin-dependent kinase inhibitor 2BAS) have been found to be significantly associated with intracranial aneurysms in the Japanese population; endothelin-1 is a potent vasoconstrictor produced by the endothelial cells. Until now, there are no diagnostic tests for specific genetic risk factors to identify patients who are at a high risk of developing intracranial aneurysms. Knowledge of the genetic determinants may be useful in order to allow clues on stopping aneurysm formation and obtain diagnostic tools for identifying individuals at increased risk. Further multicenter studies have to be carried out.

Interactions of interleukin-12A and interleukin-12B polymorphisms on the risk of intracranial aneurysm

Several lines of evidence indicate that inflammatory processes play pivotal role in the development of intracranial aneurysm (IA). Recently, polymorphisms in the interleukin-12 (IL-12) gene were shown to be associated with immune-mediated inflammatory disease. The aim of this study was to investigate the interactions of IL-12A and IL-12B polymorphisms on the risk of IA in a Chinese population. A total of 422 individuals (including 164 patients with IA and 258 controls) were involved in the study. The polymorphisms (i.e., rs2243115 and rs568408 in IL-12A and rs3212227 in IL-12B) were genotyped by polymerase chain reaction-restriction fragment length polymorphism assay and DNA sequencing. We found an association of the AC/CC genotypes and C allele of IL-12B rs3212227 with an increased risk of IA, compared with the AA genotype and A allele (AC/CC vs. AA: OR = 2.09, 95 % CI: 1.29-3.38; C vs. A: OR = 1.45, 95 % CI: 1.10-1.91). Moreover, a significant gene interaction of IL-12A and IL-12B was evident on the risk of IA, and subjects carrying variant genotypes of IL-12B rs3212227 had an increased risk of IA. In the stratified analysis by gender, the IL-12B rs3212227 AC/CC genotypes had an increased risk of IA compared with the AA genotype in male patients (AC/CC vs. AA: OR = 4.63, 95 % CI: 1.92-11.16). These findings suggest that the IL-12A and IL-12B independently and jointly be involved in the susceptibility to IA.

Mortality and causes of death in the Familial Intracranial Aneurysm study

BACKGROUND

Higher mortality for patients with aneurysmal subarachnoid haemorrhage has been reported.

AIMS

In families with intracranial aneurysms, we sought to determine whether mortality among subjects with intracranial aneurysm (affected) was higher and related to rupture, compared with unaffected family members.

METHODS

Subjects enrolled in the Familial Intracranial Aneurysm protocol were contacted yearly and their status was obtained. If reported to be deceased, the cause of death was verified by available records. A Cox proportional hazards model was utilized to compare mortality rates.

RESULTS

Of the 2794 subjects, 1073 were affected and 1721 were unaffected. There were 8525 person-years of follow-up (mean 3·05 ± 1·73 years) and 85 deaths. Age at study entry for the affected (58·4 ± 11·9 years) was significantly older (P < 0·0001) than for the unaffected (52·2 ± 16·1). After adjusting for age, the overall mortality rate for the affected subjects was not significantly different from that for the unaffected (Rate Ratio [RR] 1·26, 95% confidence interval 0·82-1·93, P = 0·292). There was a strong effect modification due to age. The mortality rate ratio of the affected to the unaffected who were ≤60 years of age was RR = 3·48 (95% confidence interval: 1·59-7·63, P = 0·002), the rate for the affected subjects who were ≥60 was less than the rate for the unaffected (RR = 0·69, 95% confidence interval: 0·404-1·19, P = 0·178). The affected who had ruptures had 2·62 times the mortality rate as those without ruptures (95% confidence interval 1·43-4·80, P = 0·002).

CONCLUSION

The overall mortality was similar for the affected and unaffected subjects in this cohort. Among the affected only, those with ruptured intracranial aneurysm had a higher mortality rate than those without ruptured.

Interactions of miR-34b/c and TP53 polymorphisms on the risk of intracranial aneurysm

Several lines of evidence indicate that inflammatory processes play a key role in the happening and development of intracranial aneurysm (IA). Recently, polymorphisms in the TP53 gene were shown to be associated with inflammation and inflammatory disease. The aim of this study was to investigate the interactions of miR-34b/c and TP53 Arg72-Pro polymorphisms on the risk of IA in a Chinese population. A total of 590 individuals (including 164 patients with IA and 426 controls) were involved in this study. The polymorphisms (i.e., miR-34b/c rs4938723 and TP53 Arg72-Pro) were genotyped by polymerase chain reaction-restriction fragment length polymorphism assay and DNA sequencing. We found that the CC genotype of miR-34b/c rs4938723 was significantly associated with a decreased risk of IA compared with the TT genotype. Moreover, a significant gene interaction of the carriers with the combined genotypes of miR-34b/c rs4938723CC and TP53 Arg72Pro CG/CC/GG had a decreased risk of IA, compared with those carrying miR-34b/c rs4938723CT/TT+TP53 Arg72Pro GG/CG/CC combined genotypes. These findings suggest that the miR-34b/c rs4938723CC and TP53 Arg72-Pro polymorphisms may be involved in the susceptibility to IA.

Saccular intracranial aneurysm: pathology and mechanisms

Saccular intracranial aneurysms (sIA) are pouch-like pathological dilatations of intracranial arteries that develop when the cerebral artery wall becomes too weak to resist hemodynamic pressure and distends. Some sIAs remain stable over time, but in others mural cells die, the matrix degenerates, and eventually the wall ruptures, causing life-threatening hemorrhage. The wall of unruptured sIAs is characterized by myointimal hyperplasia and organizing thrombus, whereas that of ruptured sIAs is characterized by a decellularized, degenerated matrix and a poorly organized luminal thrombus. Cell-mediated and humoral inflammatory reaction is seen in both, but inflammation is clearly associated with degenerated and ruptured walls. Inflammation, however, seems to be a reaction to the ongoing degenerative processes, rather than the cause. Current data suggest that the loss of mural cells and wall degeneration are related to impaired endothelial function and high oxidative stress, caused in part by luminal thrombosis. The aberrant flow conditions caused by sIA geometry are the likely cause of the endothelial dysfunction, which results in accumulation of cytotoxic and pro-inflammatory substances into the sIA wall, as well as thrombus formation. This may start the processes that eventually can lead to the decellularized and degenerated sIA wall that is prone to rupture.

Genome-wide association study for intracranial aneurysm in the Japanese population identifies three candidate susceptible loci and a functional genetic variant at EDNRA

Aneurysmal subarachnoid hemorrhage (aSAH) is the most serious subtype of stroke. Genetic factors have been known to play an important role in the development of intracranial aneurysm (IA), some of which further progress to subarachnoid hemorrhage (SAH). In this study, we conducted a genome-wide association study (GWAS) to identify common genetic variants that are associated with the risk of IA, using 1383 aSAH subjects and 5484 control individuals in the Japanese population. We selected 36 single-nucleotide polymorphisms (SNPs) that showed suggestive association (P <1 × 10(-4)) in the GWAS as well as additional 7 SNPs that were previously reported to be associated with IA, and further genotyped an additional set of 1048 IA cases and 7212 controls. We identified an SNP, rs6842241, near EDNRA at chromosome 4q31.22 (combined P-value = 9.58 × 10(-9); odds ratio = 1.25), which was found to be significantly associated with IA. Additionally, we successfully replicated and validated rs10757272 on CDKN2BAS at chromosome 9p21.3 (combined P-value = 1.55 × 10(-7); odds ratio = 1.21) to be significantly associated with IA as previously reported. Furthermore, we performed functional analysis with the associated genetic variants on EDNRA, and identified two alleles of rs6841581 that have different binding affinities to a nuclear protein(s). The transcriptional activity of the susceptible allele of this variant was significantly lower than the other, suggesting that this functional variant might affect the expression of EDNRA and subsequently result in the IA susceptibility. Identification of genetic variants on EDNRA is of clinical significance probably due to its role in vessel hemodynamic stress. Our findings should contribute to a better understanding of physiopathology of IA.

Guidelines for the primary prevention of stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

This guideline provides an overview of the evidence on established and emerging risk factors for stroke to provide evidence-based recommendations for the reduction of risk of a first stroke.

METHODS

Writing group members were nominated by the committee chair on the basis of their previous work in relevant topic areas and were approved by the American Heart Association (AHA) Stroke Council Scientific Statement Oversight Committee and the AHA Manuscript Oversight Committee. The writing group used systematic literature reviews (covering the time since the last review was published in 2006 up to April 2009), reference to previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and when appropriate, formulate recommendations using standard AHA criteria (Tables 1 and 2). All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. The guideline underwent extensive peer review by the Stroke Council leadership and the AHA scientific statements oversight committees before consideration and approval by the AHA Science Advisory and Coordinating Committee.

RESULTS

Schemes for assessing a person's risk of a first stroke were evaluated. Risk factors or risk markers for a first stroke were classified according to potential for modification (nonmodifiable, modifiable, or potentially modifiable) and strength of evidence (well documented or less well documented). Nonmodifiable risk factors include age, sex, low birth weight, race/ethnicity, and genetic predisposition. Well-documented and modifiable risk factors include hypertension, exposure to cigarette smoke, diabetes, atrial fibrillation and certain other cardiac conditions, dyslipidemia, carotid artery stenosis, sickle cell disease, postmenopausal hormone therapy, poor diet, physical inactivity, and obesity and body fat distribution. Less well-documented or potentially modifiable risk factors include the metabolic syndrome, excessive alcohol consumption, drug abuse, use of oral contraceptives, sleep-disordered breathing, migraine, hyperhomocysteinemia, elevated lipoprotein(a), hypercoagulability, inflammation, and infection. Data on the use of aspirin for primary stroke prevention are reviewed.

CONCLUSIONS

Extensive evidence identifies a variety of specific factors that increase the risk of a first stroke and that provide strategies for reducing that risk.