Subarachnoid haemorrhage in first and second degree relatives of patients with subarachnoid haemorrhage

Subarachnoid haemorrhage and intracranial aneurysms in Greenland in the period 2018-2021: incidence, outcome and familial disposition

Subarachnoid haemorrhages (SAH) caused by rupture of intracranial aneurysms (IA) are a severe condition. Earlier studies found a higher incidence of SAH in Greenlandic patients compared to Danish patients, with familial aggregation also higher in Greenland. However, updated data is lacking. To investigate the contemporary incidence, outcome, and familial disposition of SAH/IA in Greenlandic patients in 2018-2021. Greenlandic patients diagnosed with ruptured or unruptured IA (UIA) during 2018-2021 were included. Data was obtained from patient files, x-ray department, and discharge registry. Incidence rates were estimated as cases/100,000/year. Direct age-standardised incidence rates were calculated using WHO 2000-2025 as standards. Of 30 SAH patients, 20 (66.7%) were females, 10 (33.3%) males. Of 36 UIA patients, 27 (75.0%) were females, 9 (25.0%) males. For SAH, crude incidence was 13.4/100,000/year, age-standardised incidence was 10.8/100,000/year. Familial history was observed in 30.0% of SAH patients. 5 patients (16.7%) died before treatment, 28-day case-fatality rate (CFR) for all patients was 23.3%. Overall and age-standardised incidence rates were similar to previous studies but higher among females and compared to neighbouring countries. A high occurrence of familial history was reported. SAH remains a serious condition in Greenland, as evidenced by five fatalities before treatment was administered.

Role of inflammatory mediators in intracranial aneurysms: A review

The formation, growth, and rupture of intracranial aneurysms (IAs) involve hemodynamics, blood pressure, external stimuli, and a series of hormonal changes. In addition, inflammatory response causes the release of a series of inflammatory mediators, such as IL, TNF-α, MCP-1, and MMPs, which directly or indirectly promote the development process of IA. However, the specific role of these inflammatory mediators in the pathophysiological process of IA remains unclear. Recently, several anti-inflammatory, lipid-lowering, hormone-regulating drugs have been found to have a potentially protective effect on reducing IA formation and rupture in the population. These therapeutic mechanisms have not been fully elucidated, but we can look for potential therapeutic targets that may interfere with the formation and breakdown of IA by studying the relevant inflammatory response and the mechanism of IA formation and rupture involved in inflammatory mediators.

Endothelial nitric oxide synthase rs1799983 gene polymorphism is associated with the risk of developing intracranial aneurysm

PURPOSE

The intracranial aneurysm (IA) rupture is associated with a subarachnoid hemorrhage. One third of patients die, and one third remain depend for daily activities. Genetic factors are crucial in the formation and clinical evolution of IAs. Multiple loci have been associated with AIs, much of them implicating multiple pathways related to vascular endothelial maintenance and extracellular matrix integrity. Thus, the aim of our study was to characterize whether polymorphisms in genes implicated in the vascular endothelial maintenance could modify the risk of developing IAs.

SUBJECTS AND METHODS

We have studied 176 patients with IA recruited in the Service of Neurosurgery at the University Hospital of Valladolid (Spain) and a control group if 150 sex-matched healthy subjects. Clinical variables were collected from each patient. We have analyzed VEGFA rs833061, VEGFR2 rs2071559, endothelin rs5370, endoglin rs3739817, and eNOS rs1799983 polymorphisms.

RESULTS

Our results showed that allele T of the eNOS rs1799983 polymorphism is correlated with decreased risk of developing the disease; thus, allele G of the eNOS rs1799983 polymorphism increased the risk of developing IA.

CONCLUSION

The association of eNOS rs1799983 polymorphism with the risk to suffer IA reinforces the hypothesis that genetic variants in eNOS gene could be crucial in the pathogenesis of IA.

Endovascular Management of Hemorrhagic Stroke

Significant advances in endovascular neurosurgery tools, devices, and techniques are changing the approach to the management of acute hemorrhagic stroke. The endovascular treatment of intracranial aneurysms emerged in the early 1990s with Guglielmi detachable coils, and since then, it gained rapid popularity that surpassed open surgery. Stent-assisted coiling and balloon remodeling techniques have made the treatment of wide-necked aneurysms more durable. With the introduction of flow diverters and flow disrupters, many aneurysms with complex geometrics can now be reliably managed. Arteriovenous malformations and fistulae can also benefit from endovascular therapy by embolization using n-butyl cyanoacrylate (NBCA), Onyx, polyvinyl alcohol (PVA), and coils. In this article, we describe the role of endovascular treatment for the most common causes of intracerebral and subarachnoid hemorrhages, particularly ruptured aneurysms and vascular malformations.

Difference in Rupture Risk Between Familial and Sporadic Intracranial Aneurysms: An Individual Patient Data Meta-analysis

BACKGROUND AND OBJECTIVES

We combined individual patient data (IPD) from prospective cohorts of patients with unruptured intracranial aneurysms (UIAs) to assess to what extent patients with familial UIA have a higher rupture risk than those with sporadic UIA.

METHODS

For this IPD meta-analysis, we performed an Embase and PubMed search for studies published up to December 1, 2020. We included studies that (1) had a prospective study design; (2) included 50 or more patients with UIA; (3) studied the natural course of UIA and risk factors for aneurysm rupture including family history for aneurysmal subarachnoid haemorrhage and UIA; and (4) had aneurysm rupture as an outcome. Cohorts with available IPD were included. All studies included patients with newly diagnosed UIA visiting one of the study centers. The primary outcome was aneurysmal rupture. Patients with polycystic kidney disease and moyamoya disease were excluded. We compared rupture rates of familial vs sporadic UIA using a Cox proportional hazard regression model adjusted for PHASES score and smoking. We performed 2 analyses: (1) only studies defining first-degree relatives as parents, children, and siblings and (2) all studies, including those in which first-degree relatives are defined as only parents and children, but not siblings.

RESULTS

We pooled IPD from 8 cohorts with a low and moderate risk of bias. First-degree relatives were defined as parents, siblings, and children in 6 cohorts (29% Dutch, 55% Finnish, 15% Japanese), totaling 2,297 patients (17% familial, 399 patients) with 3,089 UIAs and 7,301 person-years follow-up. Rupture occurred in 10 familial cases (rupture rate: 0.89%/person-year; 95% confidence interval [CI] 0.45-1.59) and 41 sporadic cases (0.66%/person-year; 95% CI 0.48-0.89); adjusted hazard ratio (HR) for familial cases 2.56 (95% CI 1.18-5.56). After adding the 2 cohorts excluding siblings as first-degree relatives, resulting in 9,511 patients, the adjusted HR was 1.44 (95% CI 0.86-2.40).

DISCUSSION

The risk of rupture of UIA is 2.5 times higher, with a range from a 1.2 to 5 times higher risk, in familial than in sporadic UIA. When assessing the risk of rupture in UIA, family history should be taken into account.

Subarachnoid Hemorrhage

PURPOSE OF REVIEW

Subarachnoid hemorrhage (SAH) remains an important cause of mortality and long-term morbidity. This article uses a case-based approach to guide readers through the fundamental epidemiology and pathogenesis of SAH, the approach to diagnosis and management, the results of clinical trials and evidence to date, prognostic considerations, controversies, recent developments, and future directions in SAH.

RECENT FINDINGS

Historically, management of SAH focused on prevention and treatment of subsequent cerebral vasospasm, which was thought to be the primary cause of delayed cerebral ischemia. Clinical and translational studies over the past decade, including several therapeutic phase 3 randomized clinical trials, suggest that the pathophysiology of SAH-associated brain injury is multiphasic and multifactorial beyond large vessel cerebral vasospasm. The quest to reduce SAH-associated brain injury and improve outcomes is shifting away from large vessel cerebral vasospasm to a new paradigm targeting multiple brain injury mechanisms, including early brain injury, delayed cerebral ischemia, microcirculatory dysfunction, spreading cortical depolarization, inflammation, and the brain-body interaction in vascular brain injury with critical illness.Despite multiple negative randomized clinical trials in search of potential therapeutic agents ameliorating the downstream effects after SAH, the overall outcome of SAH has improved over recent decades, likely related to improvements in interventional options for ruptured cerebral aneurysms and in critical care management. Emerging clinical evidence also suggests potential harmful impact of historic empiric treatments for SAH-associated vasospasm, such as prophylactic induction of hypertension, hypervolemia, and hemodilution (triple H therapy).With decreasing mortality, long-term SAH survivorship and efforts to reduce chronic morbidity and to improve quality of life and patient-centered outcome are growing areas of unmet need. Despite existing guidelines, significant variabilities in local and regional practices and in scientific terminologies have historically limited advancement in SAH care and therapeutic development. Large global collaborative efforts developed harmonized SAH common data elements in 2019, and studies are under way to examine how existing variabilities in SAH care impact long-term SAH outcomes.

SUMMARY

Although the overall incidence and mortality of SAH is decreasing with advances in preventive and acute care, SAH remains a major cause of long-term morbidity in survivors. Significant variabilities in care settings and empiric treatment protocols and inconsistent scientific terminologies have limited advancement in patient care and therapeutic clinical studies. Large consensus efforts are under way to introduce clinical guidelines and common data elements to advance therapeutic approaches and improve patient outcome.

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.

Familial Predisposition and Differences in Radiographic Patterns in Spontaneous Nonaneurysmal Subarachnoid Hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) from an intracranial aneurysmal rupture is the most common nontraumatic etiology for SAH, but up to 15% of patients with SAH have no identifiable source.

OBJECTIVE

To assess familial predisposition to spontaneous nonaneurysmal SAH (naSAH) and to evaluate whether family history affects the severity of presentation and prognosis of this condition.

METHODS

We conducted a retrospective analysis of all spontaneous SAH with negative digital subtraction angiography from 2004 to 2018. Patients were divided into 2 groups: patients with first- or second-degree relatives with intracranial aneurysms and patients with no family history. Univariate and multivariate regression analyses were used to study patient presentation, radiographic patterns of hemorrhage, and clinical outcome.

RESULTS

A total of 100 patients met the inclusion criteria. There were no individuals with family history of naSAH. A total of 15 patients (15%) had at least one family member with an intracranial aneurysm, of which 12 (12%) presented as SAH. Patients without family history had a higher percentage of perimesencephalic presentation, whereas those with family history had a higher percentage of nonperimesencephalic SAH presentation (47% vs 13%, odds ratio [OR] 0.17 [95% CI 0.04, 0.81]).

CONCLUSION

We found a high rate of family history of intracranial aneurysms in patients who presented with naSAH. Although there was no difference in clinical outcome in patients with and without family history, there appears to be a higher percentage of nonperimesencephalic radiographic patterns of SAH in those with family history, suggesting possible different etiologies of these hemorrhages.

Screening for Intracranial Aneurysms in Individuals with a Positive First-Degree Family History: A Systematic Review

BACKGROUND

Subarachnoid hemorrhage secondary to rupture of an intracranial aneurysm (IA) is a devastating condition with high morbidity and mortality. Individuals with a positive family history of aneurysmal subarachnoid hemorrhage (aSAH) or IA can have an increased risk for aSAH or IA themselves. Screening is currently recommended in families with ≥2 affected first-degree relatives. We sought to assess the usefulness and cost-effectiveness of IA screening in individuals with a positive first-degree family history, relative to the number of family members affected.

METHODS

We performed a systematic literature search using PubMed and Google Scholar and identified additional studies by reviewing reference lists. Only original studies and review papers were considered. We excluded genetic diseases associated with IA and studies with unclear data concerning the number of first-versus second-degree relatives affected.

RESULTS

This review included 37 articles. Individuals with ≥2 affected first-degree relatives had a greater prevalence of IA (average 13.1% vs. 3% in the general population). Similarly, we found a greater prevalence of IA in individuals with ≥1 affected first-degree relative (average 4.8%, up to 19% in individuals with additional risk factors). The risk of aSAH also was increased in both categories. Recent studies stressed the importance of serial screening over time and suggested that such screening can be cost-effective in persons with only one first-degree relative with IA or aSAH.

CONCLUSIONS

While current guidelines do not recommend screening individuals with ≥1 first-degree relative affected, we found strong arguments in favor of this approach.

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.

Presymptomatic Screening for Intracranial Aneurysms in Patients with Autosomal Dominant Polycystic Kidney Disease

BACKGROUND AND OBJECTIVES

Intracranial aneurysm rupture is the most devastating complication of autosomal dominant polycystic kidney disease. Whether selective or widespread intracranial aneurysm screening is indicated remains controversial.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

Records of 3010 patients with autosomal dominant polycystic kidney disease evaluated at the Mayo Clinic between 1989 and 2017 were reviewed. Those who had presymptomatic magnetic resonance angiography screening were included.

RESULTS

Ninety-four intracranial aneurysms were diagnosed in 75 of 812 (9%) patients who underwent magnetic resonance angiography screening. Sex, age, race, and genotype were similar in the groups with and without aneurysms; hypertension and history of smoking were more frequent in the aneurysm group. Twenty-nine percent of patients with aneurysms compared with 11% of those without aneurysms had a family history of subarachnoid hemorrhage (P<0.001). Most aneurysms were small (median diameter =4 mm; range, 2-12 mm); 85% were in the anterior circulation. During a total imaging follow-up of 469 patient-years, de novo intracranial aneurysms were detected in five patients; eight intracranial aneurysms grew (median =2 mm; range, 1-3 mm). During a total clinical follow-up of 668 patient-years, seven patients had preemptive clipping or coil embolization; no intracranial aneurysms ruptured. During a total clinical follow-up of 4783 patient-years in 737 patients with no intracranial aneurysm detected on the first magnetic resonance angiography screening, two patients had an intracranial aneurysm rupture (0.04 per 100 person-years; 95% confidence interval, 0 to 0.10). The rate of intracranial aneurysm rupture in large clinical trials of autosomal dominant polycystic kidney disease was 0.04 per 100 patient-years (95% confidence interval, 0.01 to 0.06).

CONCLUSIONS

Intracranial aneurysms were detected by presymptomatic screening in 9% of patients with autosomal dominant polycystic kidney disease, more frequently in those with familial history of subarachnoid hemorrhage, hypertension, or smoking. None of the patients with and two of the patients without aneurysm detection on screening suffered aneurysmal ruptures. The overall rupture rate in our autosomal dominant polycystic kidney disease cohort was approximately five times higher than that in the general population.

Replication of GWAS Loci Revealed an Increased Risk of BET1L and H19 Polymorphisms with Intracranial Aneurysm

A genome-wide association study (GWAS) identified that BET1L rs2280543 at chromosome 11p15.5 was a susceptibility loci of intracranial aneurysm (IA). Long noncoding RNA H19, located in this region, was reported to play a crucial role in the formation of IA. In this study, we aimed to examine whether BET1L rs2280543 and potentially functional polymorphisms in H19 influence the risk of IA. A hospital-based case-control study was performed involving 542 IA patients and 588 age- and gender-matched controls. The BET1L rs2280543 and H19 polymorphisms were genotyped using the TaqMan assay. The BET1L rs2280543 CT, CT/TT genotypes, and T allele were associated with an increased risk of IA (CT vs. CC, adjusted OR = 1.43, 95% CI: 1.08-1.90, P = 0.01; CT/TT vs. CC, adjusted OR = 1.48, 95% CI: 1.12-1.94, P = 0.005; and T vs. C, adjusted OR = 1.44, 95% CI: 1.13-1.83, P = 0.003). Similarly, the H19 rs217727 TT genotype and T allele were associated with an increased risk of IA (TT vs. CC, adjusted OR = 1.90, 95% CI: 1.35-2.67, P < 0.001; T vs. C, adjusted OR = 1.38, 95% CI: 1.16-1.64, P < 0.001). Combined analyses revealed that the rs2280543 CC-rs217727 CT/TT, rs2280543 CT/TT-rs2735971 GG, and rs217727 CT/TT-rs2735971 GG genotypes were related to the risk of IA. Interaction analysis showed that the 3-loci model of rs2280543-rs217727-rs2839698 contributed to an increased risk of IA. These findings suggest that the GWAS-discovered risk loci BET1L rs2280543 may increase IA susceptibility by interacting with lncRNA H19.

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.

Prospective study: Long-term outcome at 12-15 years after aneurysmal subarachnoid hemorrhage

BACKGROUND

Patients with aneurysmal subarachnoid hemorrhage (aSAH) have poor outcome. Studies on outcome beyond 1 year post-aSAH are few, and late recovery is poorly investigated, initiating this prospective outcome study on patients 12-15 years after an aSAH. We hypothesized to find; functional improvement > 1 year post-ictus; increased long-term mortality in aSAH patients vs matched controls, and finally to present; predictors of long-term favorable outcome (GOS 4-5).

METHODS

We prospectively investigated patients, admitted 2000-2003 to the Sahlgrenska University Hospital, 1 year post-ictus using Glasgow Outcome Scale (GOS). The patients were revalidated 12-15 years post-aSAH by structured-telephone interviews (GOS), followed by statistical analysis.

RESULTS

A total of 158 patients were included, (women n = 114, men n = 44), with a mean age of 55 years at aSAH. Patients treated with surgical clipping had lower mortality. At the follow-up 12-15 years post-aSAH, all 103 survivors (65.2%) were categorized as having; good recovery (39.9%), moderate disability (15.2%), or severe disability (10.1%). Within the patient cohort, 23.6% improved GOS over time. Fifty-five patients died, median at 4 years post-ictus. aSAH patients had 3.5 times increased mortality 12-15 years post-ictus vs matched controls (P < .0001). Patients with favorable outcome at 1 year (67.3%, n = 101) had similar survival probability as control patients. Prognostic indicators of long-term favorable outcome were low age and high GOS at 1-year follow-up, (AUCROC, 0.79).

CONCLUSIONS

Individual functional improvement was found >1 year post-ictus. Patients with favorable outcome at 1 year had similar long-term life expectancy as the general population. Indicators of long-term favorable prognosis were low age at ictus and high GOS at 1-year follow-up.

TLR4 gene polymorphisms rs11536889 is associated with intracranial aneurysm susceptibility

Intracranial aneurysm (IA) is a common lesion which often present asymptomatic until the time of rupture and result in subarachnoid hemorrhage (SAH). The pathogenesis of IA formation is complex and is influenced by both genetic and environmental risk factors. For exploring the detailed molecular and cellular mechanisms involved in the pathogenesis of IA, recent studies indicated inflammatory pathways and their genetic variants may as potential biomarkers. In this study, functionally relevant polymorphisms in the toll-like receptor 4 (TLR4) were screened in 330 IA patients and 313 controls from a Han Chinese population. Eight single nucleotide gene polymorphisms (SNPs) genotyped by the Improved Multiple Ligase Detection Reaction (iMLDR) method. Our results indicated that the presence of the minor allele (C) of the TLR4 SNP rs11536889 was associated with a decreased risk of IA (C vs. G, OR = 0.731; 95% CI 0.567-0.943; P = 0.017). This association was also present at the genotype level in a codominant model (GC vs. GG, OR = 0.447; 95% CI 0.226-0.884; P = 0.020) and a recessive model (CC vs. GG + GC, OR = 0.489; 95% CI 0.250-0.955; P = 0.035). In summary, we firstly found that the TLR4 SNP rs11536889 was significantly associated with the susceptibility of IA. Our results indicated TLR4 SNP rs11536889 may be a marker for IA risk, though the exact functional roles of TLR4 SNP rs11536889 in IA formation are still not very clear.

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.

Circulating microRNAs in patients with intracranial aneurysms

Introduction

We compared circulating microRNA (miRNA) levels in plasma of patients with intracranial aneurysms (IA) to those of controls as a first step towards finding potential biomarkers for individuals at high risk of IA development and its subsequent rupture.

Patients and methods

Using a PCR array we measured 370 miRNAs in plasma of 15 patients with prior aneurysmal subarachnoid hemorrhage (aSAH), of whom 11 had an additional unruptured IA (UIA), and of 15 controls. MiRNAs with a difference in levels with an absolute fold change (FC) > 1.2 and p<0.01 were further tested using real-time (RT) PCR in an additional independent set of 15 aSAH patients, 15 untreated UIA patients and 15 controls for replication (absolute FC >1.2 and p<0.05). We used receiver operating characteristic (ROC) curves to illustrate the diagnostic potential of these miRNAs.

Results

Three of five miRNAs with a difference in levels in the PCR array study were replicated with miRNA-183-5p decreased in all patients (FC = -2.2, p = 1.7x10^-3), miRNA-200a-3p increased in aSAH patients (FC = 1.8, p = 2.8x10^-2) and miRNA-let7b-5p decreased in UIA patients (FC = -1.7, p = 1.27x10^-3) as compared to controls. In distinguishing aSAH patients from controls, the area under the ROC curve (AUC) was 0.80 (95% confidence interval (95% CI) 0.63–0.97) for miRNA-183-5p, and 0.74 (95% CI 0.55–0.94) for miRNA-200a-3p. In distinguishing untreated UIA patients from controls, AUC was 0.83 (95% CI 0.69–0.98) for miRNA-183-5p and 0.92 (95% CI 0.81–1) for miRNA-let-7b.

Discussion/Conclusions

We identified three specific circulating miRNAs that are able to discriminate between IA patients and controls. Follow-up studies should assess if these miRNAs may be used biomarkers for identifying individuals at high risk of IA development and its subsequent rupture.

Spontaneous subarachnoid haemorrhage

Subarachnoid haemorrhage is an uncommon and severe subtype of stroke affecting patients at a mean age of 55 years, leading to loss of many years of productive life. The rupture of an intracranial aneurysm is the underlining cause in 85% of cases. Survival from aneurysmal subarachnoid haemorrhage has increased by 17% in the past few decades, probably because of better diagnosis, early aneurysm repair, prescription of nimodipine, and advanced intensive care support. Nevertheless, survivors commonly have cognitive impairments, which in turn affect patients' daily functionality, working capacity, and quality of life. Additionally, those deficits are frequently accompanied by mood disorders, fatigue, and sleep disturbances. Management requires specialised neurological intensive care units and multidisciplinary clinical expertise, which is better provided in high-volume centres. Many clinical trials have been done, but only two interventions are shown to improve outcome. Challenges that remain relate to prevention of subarachnoid haemorrhage by improved screening and development of lower-risk methods to repair or stabilise aneurysms that have not yet ruptured. Multicentre cooperative efforts might increase the knowledge that can be gained from clinical trials, which is often limited by small studies with differing criteria and endpoints that are done in single centres. Outcome assessments that incorporate finer assessment of neurocognitive function and validated surrogate imaging or biomarkers for outcome could also help to advance the specialty.

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 cost-effectiveness analysis of screening for intracranial aneurysms in persons with one first-degree relative with subarachnoid haemorrhage

Introduction

Although persons with one first-degree relative with aneurysmal subarachnoid haemorrhage have an increased risk of aneurysm formation and aneurysmal subarachnoid haemorrhage, screening them for unruptured intracranial aneurysms was not beneficial in a modelling study from the 1990s. New data on the risk of aneurysmal subarachnoid haemorrhage in these persons and improved treatment techniques call for reassessment of the cost-effectiveness of screening.

Patients and methods

We used a cost-effectiveness analysis using a Markov model and Monte Carlo simulation comparing screening and preventive aneurysm treatment with no screening in persons with one first-degree relative with aneurysmal subarachnoid haemorrhage. We analyzed the impact on quality-adjusted life years, costs and net health benefit of single screening (at varying screening age) and serial screening (with varying screening age and intervals) using a cost-effectiveness threshold of €20,000/quality-adjusted life year.

Results

In 17 of the 24 strategies assessed, additional costs for screening for unruptured intracranial aneurysm were <€20,000 per quality-adjusted life year gained. The strategy with highest net health benefit was screening at age 40 and 55. Screening every five years from age 20 to 70 yielded the highest health benefits at the highest additional costs.

Discussion

Based on current risks of aneurysmal subarachnoid haemorrhage and complications of preventive treatment, several strategies to screen for unruptured intracranial aneurysm in persons with one first-degree relative with aneurysmal subarachnoid haemorrhage are cost effective compared with no screening, when applying a cost-effectiveness threshold of €20,000/quality-adjusted life year.

Conclusion

We recommend discussing with persons at risk the option of screening twice, at age 40 and 55, which will result overall in substantial health benefits at acceptable additional costs.

Biology of Saccular Cerebral Aneurysms: A Review of Current Understanding and Future Directions

Understanding the biology of intracranial aneurysms is a clinical quandary. How these aneurysms form, progress, and rupture is poorly understood. Evidence indicates that well-established risk factors play a critical role, along with immunologic factors, in their development and clinical outcomes. Much of the expanding knowledge of the inception, progression, and rupture of intracranial aneurysms implicates inflammation as a critical mediator of aneurysm pathogenesis. Thus, therapeutic targets exploiting this arm of aneurysm pathogenesis have been implemented, often with promising outcomes.

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.

Whole Blood Gene Expression Profiles of Patients with a Past Aneurysmal Subarachnoid Hemorrhage

Background

The pathogenesis of development and rupture of intracranial aneurysms (IA) is largely unknown. Also, screening for IA to prevent aneurysmal subarachnoid hemorrhage (aSAH) is inefficient, as disease markers are lacking. We investigated gene expression profiles in blood of previous aSAH patients, who are still at risk for future IA, aiming to gain insight into the pathogenesis of IA and aSAH, and to make a first step towards improvement of aSAH risk prediction.

Methods and Results

We collected peripheral blood of 119 patients with aSAH at least two years prior, and 118 controls. We determined gene expression profiles using Illumina HumanHT-12v4 BeadChips. After quality control, we divided the dataset in a discovery (2/3) and replication set (1/3), identified differentially expressed genes, and applied (co-)differential co-expression to identify disease-related gene networks. No genes with a significant (false-discovery rate <5%) differential expression were observed. We detected one gene network with significant differential co-expression, but did not find biologically meaningful gene networks related to a history of aSAH. Next, we applied prediction analysis of microarrays to find a gene set that optimally predicts absence or presence of a history of aSAH. We found no gene sets with a correct disease state prediction higher than 40%.

Conclusions

No gene expression differences were present in blood of previous aSAH patients compared to controls, besides one differentially co-expressed gene network without a clear relevant biological function. Our findings suggest that gene expression profiles, as detected in blood of previous aSAH patients, do not reveal the pathogenesis of IA and aSAH, and cannot be used for aSAH risk prediction.

Lessons learned from whole exome sequencing in multiplex families affected by a complex genetic disorder, intracranial aneurysm

Genetic risk factors for intracranial aneurysm (IA) are not yet fully understood. Genomewide association studies have been successful at identifying common variants; however, the role of rare variation in IA susceptibility has not been fully explored. In this study, we report the use of whole exome sequencing (WES) in seven densely-affected families (45 individuals) recruited as part of the Familial Intracranial Aneurysm study. WES variants were prioritized by functional prediction, frequency, predicted pathogenicity, and segregation within families. Using these criteria, 68 variants in 68 genes were prioritized across the seven families. Of the genes that were expressed in IA tissue, one gene (TMEM132B) was differentially expressed in aneurysmal samples (n=44) as compared to control samples (n=16) (false discovery rate adjusted p-value=0.023). We demonstrate that sequencing of densely affected families permits exploration of the role of rare variants in a relatively common disease such as IA, although there are important study design considerations for applying sequencing to complex disorders. In this study, we explore methods of WES variant prioritization, including the incorporation of unaffected individuals, multipoint linkage analysis, biological pathway information, and transcriptome profiling. Further studies are needed to validate and characterize the set of variants and genes identified in this study.

Familial perimesencephalic subarachnoid hemorrhage: two case reports

Introduction

Non-aneurysmal spontaneous subarachnoid hemorrhage is characterized by an accumulation of a limited amount of subarachnoid hemorrhage, predominantly around the midbrain, and a lack of blood in the brain parenchyma or ventricular system. It represents 5% of all spontaneous subarachnoid hemorrhage cases. In spite of extensive investigation, understanding of the mechanisms leading to perimesencephalic non-aneurysmal subarachnoid hemorrhage remains incompletely defined. A growing body of evidence has supported a familial predisposition for non-aneurysmal spontaneous subarachnoid hemorrhage.

Case presentation

A 39-year-old Caucasian man presented with sudden onset headache associated with diplopia. His computed tomography scan revealed perimesencephalic subarachnoid hemorrhage. A cerebral angiogram showed no apparent source of bleeding. He was treated conservatively and discharged after 1 week without any neurological deficits. The older brother of the first case, a 44-year-old Caucasian man, presented 1.5 years later with acute onset of headache and his computed tomography scan also showed perimesencephalic non-aneurysmal subarachnoid hemorrhage. He was discharged home with normal neurological examination 1 week later. Follow-up angiograms did not reveal any source of bleeding in either patient.

Conclusions

We report the cases of two siblings with perimesencephalic non-aneurysmal subarachnoid hemorrhage, which may further suggest a familial predisposition of non-aneurysmal spontaneous subarachnoid hemorrhage and may also point out the possible higher risk of perimesencephalic non-aneurysmal subarachnoid hemorrhage in the first-degree relatives of patients with perimesencephalic non-aneurysmal subarachnoid hemorrhage.

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.

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.

Genetic risk factors for intracranial aneurysms: a meta-analysis in more than 116,000 individuals

OBJECTIVE

There is an urgent need to identify risk factors for sporadic intracranial aneurysm (IA) development and rupture. A genetic component has long been recognized, but firm conclusions have been elusive given the generally small sample sizes and lack of replication. Genome-wide association studies have overcome some limitations, but the number of robust genetic risk factors for IA remains uncertain.

METHODS

We conducted a comprehensive systematic review and meta-analysis of all genetic association studies (including genome-wide association studies) of sporadic IA, conducted according to Strengthening the Reporting of Genetic Association Studies and Human Genome Epidemiology Network guidelines. We tested the robustness of associations using random-effects and sensitivity analyses.

RESULTS

Sixty-one studies including 32,887 IA cases and 83,683 controls were included. We identified 19 single nucleotide polymorphisms associated with IA. The strongest associations, robust to sensitivity analyses for statistical heterogeneity and ethnicity, were found for the following single nucleotide polymorphisms: on chromosome 9 within the cyclin-dependent kinase inhibitor 2B antisense inhibitor gene (rs10757278: odds ratio [OR] 1.29; 95% confidence interval [CI] 1.21-1.38; and rs1333040: OR 1.24; 95% CI 1.20-1.29), on chromosome 8 near the SOX17 transcription regulator gene (rs9298506: OR 1.21; 95% CI 1.15-1.27; and rs10958409: OR 1.19; 95% CI 1.13-1.26), and on chromosome 4 near the endothelin receptor A gene (rs6841581: OR 1.22; 95% CI 1.14-1.31).

CONCLUSIONS

Our comprehensive meta-analysis confirms a substantial genetic contribution to sporadic IA, implicating multiple pathophysiologic pathways, mainly relating to vascular endothelial maintenance. However, the limited data for IA compared with other complex diseases necessitates large-scale replication studies in a full spectrum of populations, with investigation of how genetic variants relate to phenotype (e.g., IA size, location, and rupture status).

European Stroke Organization guidelines for the management of intracranial aneurysms and subarachnoid haemorrhage

BACKGROUND

Intracranial aneurysm with and without subarachnoid haemorrhage (SAH) is a relevant health problem: The overall incidence is about 9 per 100,000 with a wide range, in some countries up to 20 per 100,000. Mortality rate with conservative treatment within the first months is 50-60%. About one third of patients left with an untreated aneurysm will die from recurrent bleeding within 6 months after recovering from the first bleeding. The prognosis is further influenced by vasospasm, hydrocephalus, delayed ischaemic deficit and other complications. The aim of these guidelines is to provide comprehensive recommendations on the management of SAH with and without aneurysm as well as on unruptured intracranial aneurysm.

METHODS

We performed an extensive literature search from 1960 to 2011 using Medline and Embase. Members of the writing group met in person and by teleconferences to discuss recommendations. Search results were graded according to the criteria of the European Federation of Neurological Societies. Members of the Guidelines Committee of the European Stroke Organization reviewed the guidelines.

RESULTS

These guidelines provide evidence-based information on epidemiology, risk factors and prognosis of SAH and recommendations on diagnostic and therapeutic methods of both ruptured and unruptured intracranial aneurysms. Several risk factors of aneurysm growth and rupture have been identified. We provide recommendations on diagnostic work up, monitoring and general management (blood pressure, blood glucose, temperature, thromboprophylaxis, antiepileptic treatment, use of steroids). Specific therapeutic interventions consider timing of procedures, clipping and coiling. Complications such as hydrocephalus, vasospasm and delayed ischaemic deficit were covered. We also thought to add recommendations on SAH without aneurysm and on unruptured aneurysms.

CONCLUSION

Ruptured intracranial aneurysm with a high rate of subsequent complications is a serious disease needing prompt treatment in centres having high quality of experience of treatment for these patients. These guidelines provide practical, evidence-based advice for the management of patients with intracranial aneurysm with or without rupture. Applying these measures can improve the prognosis of SAH.

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.

The genetics of vascular complications in autosomal dominant polycystic kidney disease (ADPKD)

The most important extra-renal manifestation of autosomal dominant polycystic kidney disease (ADPKD) in terms of debilitating injury and premature death is the development of intracranial aneurysms (IAs) and other vascular complications, resulting in subarachnoid hemorrhage (SAH). IAs are found at a rate approximately five times higher in ADPKD patients than in the general population and in patients with a family history of SAH/IAs the frequency is elevated further three to five times, indicating the importance of genetic factors in its etiology. Expression of the ADPKD gene products, polycystin-1 (PKD1) and polycystin-2 (PKD2), in vascular smooth muscle and the endothelium, and evidence that reduced levels of these proteins leads to IA development in mouse models, suggests a direct role of these proteins in the vascular disease. PKD1 and PKD2 patients seem equally likely to develop IAs, while patients with mutations to the 5' half of PKD1 may more likely have vascular complications. Genome wide association and candidate studies of multiplex families with IAs without ADPKD have identified a number of genes/proteins that may be risk factors for the development of IAs. These candidate proteins largely have roles in the maintenance and remodeling of the arterial wall of small brain arteries. The development of the genetic methodologies of massively parallel sequencing mean it is now possible to test these and other candidates in ADPKD families with multiplex and singleton IA cases. Identifying strong modifiers of this phenotype will be important for prioritizing patients for presymptomatic screening and interventions.

Annual rupture risk of growing unruptured cerebral aneurysms detected by magnetic resonance angiography

Object

In this paper, the authors' goals were to clarify the characteristics of growing unruptured cerebral aneurysms detected by serial MR angiography and to establish the recommended follow-up interval.

Methods

A total of 1002 patients with 1325 unruptured cerebral aneurysms were retrospectively identified. These patients had undergone follow-up evaluation at least twice. Aneurysm growth was defined as an increase in maximum aneurysm diameter by 1.5 times or the appearance of a bleb.

Results

Aneurysm growth was observed in 18 patients during the period of this study (1.8%/person-year). The annual rupture risk after growth was 18.5%/person-year. The proportion of females among patients with growing aneurysms was significantly larger than those without growing aneurysms (p = 0.0281). The aneurysm wall was reddish, thin, and fragile on intraoperative findings. Frequent follow-up examination is recommended to detect aneurysm growth before rupture.

Conclusions

Despite the relatively short period, the annual rupture risk of growing unruptured cerebral aneurysms detected by MR angiography was not as low as previously reported. Surgical or endovascular treatment can be considered if aneurysm growth is detected during the follow-up period.

Cerebral vasospasm after sub-arachnoid hemorrhage as a clinical predictor and phenotype for genetic association study

BACKGROUND

A typology of cerebral vasospasm has been proposed based on distinct clinical manifestations: delayed cerebral ischemia, symptomatic 'vasospasm', angiographic vasospasm, and transcranial Doppler vasospasm. We examined each distinct clinical manifestation in a nonparametric genetic association study.

AIMS

The purpose of this study was to examine and compare each four distinct acute clinical manifestations and test its perspectives in genetic association studies.

METHODS

Two hundred forty-five Caucasian patients with sub-arachnoid hemorrhage were evaluated for these four distinct clinical manifestations along with 906 600 single-nucleotide polymorphisms across the human genome.

RESULTS

The four clinical manifestations were significantly associated with each other as P-values ranged from 3·31 × 10(-4) to 8·10 × 10(-15) . Transcranial Doppler vasospasm showed significant genetic association with single nucleotide polymorphism (SNP) (rs999662, P = 3·39 × 10(-8) ). Statistical P-value of rs999662 in association with delayed cerebral ischemia, symptomatic 'vasospasm', and angiographic vasospasm was 0·0017, 0·0017, and 0·19, respectively.

CONCLUSIONS

Despite different criteria for each of the four clinical manifestations, they are significantly associated with each other. Our results suggest transcranial Doppler vasospasm may be an appropriate intermediate but still clinically relevant phenotype for genetic association studies. Association with SNP rs999662 indicates a potential role for the region containing the solute carrier family 12 member 3 (SLC12A3) gene in transcranial Doppler vasospasm following sub-arachnoid hemorrhage.

The case for family screening for intracranial aneurysms

Given that relatives of patients with intracranial aneurysms (IAs) or subarachnoid hemorrhage have a greater risk of harboring an aneurysm, family screening has become a common practice in neurosurgery. Unclear data exist regarding who should be screened and at what age and interval screening should occur. Multiple factors including the natural history of IAs, the risk of treatment, the cost of screening, and the psychosocial impact of finding an aneurysm should be taken into account when family screening is considered. In this paper, the authors review the current literature regarding risk factors and natural history of sporadic and familial aneurysms. Based on these data the authors assess current recommendations for screening and propose their own recommendations.

Genome-wide association analysis of copy number variations in subarachnoid aneurysmal hemorrhage

Subarachnoid aneurysmal hemorrhage (SAH) due to cerebral aneurysm rupture is a very serious disease resulting in high mortality rate. It has been known that genetic factors are involved in the risk of SAH. A recent breakthrough in genomic variation called copy number variation (CNV) has been revealed to be involved in risks of human diseases. In this study, we hypothesized that CNVs can predict the risk of SAH. We used the Illumina HumanHap300 BeadChip (317 503 markers) to genotype 497 individuals in a Japanese population. Furthermore, individual CNVs were identified using signal and allelic intensities. The genetic effect of CNV on the risk of SAH was evaluated using multivariate logistic regression controlling for age and gender in 187 common CNV regions (frequency >1%). From a total of 4574 individual CNVs identified in this study (9.7 CNVs per individual), we were able to discover 1644 unique CNV regions containing 1232 genes. The identified variations were validated using visual examination of the genoplot image, overlapping analysis with the Database of Genomic Variants (73.2%), CNVpartition (72.4%) and quantitative PCR. Interestingly, two CNV regions, chr4:153210505-153212191 (deletion, 4q31.3, P=0.0005, P(corr) (corrected P-value)=0.04) and chr10:6265006-6267388 (duplication, 10p15.1, P=0.0006, P(corr)=0.05), were significantly associated with the risk of SAH after multiple testing corrections. Our results suggest that the newly identified CNV regions may contribute to SAH disease susceptibility.

Spontaneous arterial dissection: phenotype and molecular pathogenesis

Arterial dissection (AD) is defined as the longitudinal splitting up of the arterial wall caused by intramural bleeding. It can occur as a spontaneous event in all large and medium sized arteries. The histological hallmark of AD is medial degeneration. Histological investigations, gene expression profiling and proteome studies of affected arteries reveal disturbances in many different biological processes including inflammation, proteolytic activity, cell proliferation, apoptosis and smooth muscle cell (SMC) contractile function. Medial degeneration can be caused by various rare dominant Mendelian disorders. Genetic linkage analysis lead to the identification of mutations in different disease-causing genes involved in the biosynthesis of the extracellular matrix (FBN1, COL3A1), in transforming growth factor (TGF) beta signaling (FBN1, TGFBR1, TGFBR2) and in the SMC contractile system (ACTA2, MYH11). Genome wide association studies suggest that the CDKN2A/CDKN2B locus plays a role in the etiology AD and other arterial diseases.

Unruptured intracranial aneurysms: initial and follow-up screening

Subarachnoid hemorrhage (SAH) from a ruptured intracranial aneurysm is a devastating disease that causes death or severe disability in half of patients. Intracranial aneurysms are not present at birth but develop during life. Actively searching and treating intracranial aneurysms before rupture may prevent SAH as a result of these aneurysms. The prevalence of intracranial aneurysms is approximately 2% in the general population, but higher in subgroups such as patients who have survived an episode of SAH, persons with a family history of SAH and patients with polycystic kidney disease. Screening for intracranial aneurysms should be considered in these high-risk groups. Some of the intracranial aneurysms detected with screening will be too small to be treated, and may therefore be followed over time, which can cause anxiety in the patient. In this article, we discuss current knowledge, remaining questions and future perspectives in screening and follow-up imaging for unruptured intracranial aneurysms.

The genetics of sporadic ruptured and unruptured intracranial aneurysms: a genetic meta-analysis of 8 genes and 13 polymorphisms in approximately 20,000 individuals

Object

Intracranial aneurysms (IAs) are thought to have a multifactorial origin. The authors undertook a comprehensive meta-analysis on all genes investigated using a case-control model in ruptured (subarachnoid hemorrhage) and unruptured aneurysms.

Methods

Electronic databases were searched until and including July 2008 for any candidate gene studied in IA or subarachnoid hemorrhage using a case-control model. The ORs and 95% CIs were determined for each gene-disease association using fixed and random effect models.

Results

Thirty studies of 8 genes and 13 polymorphisms were analyzed among 19,961 individuals (6622 cases and 13,339 controls). Two genes and 3 polymorphisms were associated with IA. The eNOS gene T786C polymorphism (OR 1.24, 95% CI 1.0–1.54; p = 0.05) and IL-6 gene G572C polymorphism (OR 7.08, 95% CI 2.85–17.57; p < 0.0001) both showed a significant association with ruptured/unruptured IA. The IL-6/G174C polymorphism exerted a significant protective effect against IA (OR 0.49, 95% CI 0.25–0.95; p = 0.04). The other candidate genes investigated (ACE, endoglin, APOE, elastin, MMP-3, and SERPINA3) showed no significant associations.

Conclusions

There is a likely genetic basis to sporadic IAs. However, the evidence base is small when compared against other complex disorders.

The intracranial aneurysm susceptibility genes HSPG2 and CSPG2 are not associated with abdominal aortic aneurysm

BACKGROUND

A genetic variant on chromosome 9p21 associates with abdominal aortic aneurysm (AAA) and intracranial aneurysm (IA), indicating that despite the differences in pathology there are shared genetic risk factors. We investigated whether the IA susceptibility genes heparan sulfate proteoglycan 2 (HSPG2) and chondroitin sulfate proteoglycan 2 (CSPG2) associate with AAA as well.

METHODS

Using tag single nucleotide polymorphisms (SNPs), all common variants were analyzed in a Dutch AAA case-control population in a 2-stage genotyping approach. In stage 1, 12 tag SNPs in HSPG2 and 22 tag SNPs in CSPG2 were genotyped in 376 patients and 648 controls. Genotyping of significantly associated SNPs was replicated in a second independent cohort of 360 cases and 376 controls.

RESULTS

In stage 1, no HSPG2 SNPs and 1 CSPG2 SNP associated with AAA (rs2652106, P = .019). Association of this SNP was not replicated (P = .342).

CONCLUSIONS

Our findings demonstrate that, in contrast to IA, HSPG2 and CSPG2 do not associate with AAA.

Sequencing of TGF-beta pathway genes in familial cases of intracranial aneurysm

BACKGROUND AND PURPOSE

Familial aggregation of intracranial aneurysms (IA) strongly suggests a genetic contribution to pathogenesis. However, genetic risk factors have yet to be defined. For families affected by aortic aneurysms, specific gene variants have been identified, many affecting the receptors to transforming growth factor-beta (TGF-beta). In recent work, we found that aortic and intracranial aneurysms may share a common genetic basis in some families. We hypothesized, therefore, that mutations in TGF-beta receptors might also play a role in IA pathogenesis.

METHODS

To identify genetic variants in TGF-beta and its receptors, TGFB1, TGFBR1, TGFBR2, ACVR1, TGFBR3, and ENG were directly sequenced in 44 unrelated patients with familial IA. Novel variants were confirmed by restriction digestion analyses, and allele frequencies were analyzed in cases versus individuals without known intracranial disease. Similarly, allele frequencies of a subset of known SNPs in each gene were also analyzed for association with IA.

RESULTS

No mutations were found in TGFB1, TGFBR1, TGFBR2, or ACVR1. Novel variants identified in ENG (p.A60E) and TGFBR3 (p.W112R) were not detected in at least 892 reference chromosomes. ENG p.A60E showed significant association with familial IA in case-control studies (P=0.0080). No association with IA could be found for any of the known polymorphisms tested.

CONCLUSIONS

Mutations in TGF-beta receptor genes are not a major cause of IA. However, we identified rare variants in ENG and TGFBR3 that may be important for IA pathogenesis in a subset of families.

Genomewide Linkage in a Large Caucasian Family Maps a New Locus for Intracranial Aneurysms to Chromosome 13q

Background and Purpose— Familial aggregation of intracranial aneurysms (IAs) indicates a genetic role in the pathogenesis of this disease. Despite a number of reported susceptibility loci, no disease-causing gene variants have been identified. In this study, we used a parametric genomewide linkage approach to search for new IA susceptibility loci in a large Caucasian family.

Methods— The affection status of family members with clinical signs of IA was confirmed with medical records or through radiological or surgical examinations. All other relatives were screened using MR angiography. Genomewide linkage analysis was performed on 35 subjects using approximately 250 000 single nucleotide polymorphic markers.

Results— Ten individuals had an IA. Linkage analysis using a dominant model showed significant linkage to a 7-cM region in 13q14.12–21.1 with a maximum logarithm of odds score of 4.56.

Conclusion— A new IA susceptibility locus on 13q was identified, adding to the number of IA loci already reported. Given that no coding variants have been reported to date, it is possible that alternative genetic variants such as regulatory elements or copy number variation are important in IA pathogenesis. We are proceeding with attempts to identify such variants in our locus.