Hormonal factors and risk of aneurysmal subarachnoid hemorrhage: an international population-based, case-control study

Identifying novel risk factors for aneurysmal subarachnoid haemorrhage using machine learning

Aneurysmal subarachnoid haemorrhage (aSAH) is a type of stroke with high mortality and morbidity. This study aimed to identify novel aSAH risk factors by combining machine learning (ML) and traditional statistical methods. Using the UK Biobank, we identified aSAH cases via hospital-based ICD codes and analysed 618 baseline variables covering demographics, lifestyle, medical history, and physical measurements. The CatBoost ML algorithm and Shapley Additive Explanations (SHAP) identified the top 25 variables most influential in predicting aSAH. Logistic regression further described these variables while adjusting for established aSAH risk factors. Among 501,847 participants, 893 aSAH cases were identified. ML identified 214 variables with non-zero SHAP values. Logistic regression of the top 25 variables revealed four potential novel aSAH risk factors. Increased aSAH risk was associated with mean sphered cell volume (OR 1.02, 95% CI 1.00-1.03) and tea intake (OR 1.03, 95% CI 1.01-1.05). Decreased aSAH risk was associated with peak expiratory flow (OR 0.80, 95% CI 0.66-0.96), and haematocrit percentage (OR 0.97, 95% CI 0.95-1.00). Future research should validate these findings and explore the potential non-linear relationships and interactions indicated by the ML models.

Plasma Estrogen Levels and Aneurysmal Subarachnoid Hemorrhage in Women

OBJECTIVE

Aneurysmal subarachnoid hemorrhage (aSAH) is more prevalent in postmenopausal women, and it has been postulated that this relationship is hormonally driven by lower circulating levels of estrogens. We examined the association between circulating plasma estrogen levels and subsequent development of aSAH in women.

METHODS

Women from the Nurses' Health Study with confirmed aSAH (n = 38) were matched with controls (n = 38) on age, smoking, menopausal status, and other reproductive factors. Plasma estriol, estradiol, and sex hormone-binding globulin were measured at baseline, prior to the development of aSAH. Conditional logistic regressions were performed to assess the association between hormone levels and incident aSAH.

RESULTS

Plasma estradiol, estriol, and sex hormone-binding globulin were not associated with the subsequent development of aSAH. Women with a history of current or former smoking were associated with lower levels of circulating estriol (β = -0.35 ± 0.12, P = 0.004) and estradiol (β = -0.63 ± 0.16, P = 0.0002).

CONCLUSIONS

In this study, we did not find an association between estrogen levels and the incidence of aSAH in women.

Mirror Aneurysms of the Pericallosal Artery Clipped During a Single Surgical Procedure: Case Report and Literature Review

Pericallosal artery aneurysms are rare, accounting for 2-9% of all intracranial aneurysms, and mirror aneurysms in this location are exceptionally uncommon, presenting unique surgical challenges due to their deep location and proximity to critical neurovascular structures. The aim of this case report is to describe the surgical management and successful outcome of a patient with mirror pericallosal artery aneurysms and to contribute insights into the clinical and surgical considerations for this rare condition. We report the case of a 71-year-old female with multiple cardiovascular and metabolic conditions, including hypertension and smoking-well-established risk factors for intracranial aneurysm formation and rupture. She presented with a Hunt and Hess grade II subarachnoid hemorrhage resulting in communicating internal hydrocephalus. Preoperative angiography revealed mirror aneurysms of the pericallosal artery. The patient underwent a left basal paramedian frontal craniotomy, during which a ruptured aneurysm on the right A2 segment and an unruptured aneurysm on the left A2 segment were identified. Both aneurysms were successfully clipped using curved Yasargil clips. Postoperative recovery was favorable, with no neurological deficits and stable imaging findings at a three-month follow-up. This case underscores the necessity for precise microsurgical intervention and a thorough understanding of pericallosal artery anatomy to manage such rare and challenging conditions effectively. The role of hyperlipidemia and statin use in intracranial aneurysm development remains debated and warrants further investigation. Our successful management of mirror pericallosal artery aneurysms contributes to the limited literature on this rare condition and highlights the importance of meticulous surgical techniques for favorable outcomes.

Sex Differences of Hospital and Emergency Department Presentations of Stroke in Canada

We provide an updated estimate of adult stroke event rates by age group, sex, and stroke type using Canadian administrative data. In the 2017-2018 fiscal year, there were an estimated 81,781 hospital or emergency department visits for stroke events in Canada, excluding Quebec. Our findings show that overall, the event rate of stroke is similar between women and men. There were slight differences in stroke event rate at various ages by sex and stroke type and emerging patterns warrant attention in future studies. Our findings emphasize the importance of continuous surveillance to monitor the epidemiology of stroke in Canada.

Hormonal influences on cerebral aneurysms: unraveling the complex connections

INTRODUCTION

Intracranial aneurysms (IAs) occur in 3-5% of the general population and are characterized by localized structural deterioration of the arterial wall with loss of internal elastic lamina and disruption of the media. The risk of incidence and rupture of aneurysms depends on age, sex, ethnicity, and other different factors, indicating the influence of genetic and environmental factors. When an aneurysm ruptures, there is an estimated 20% mortality rate, along with an added 30-40% morbidity in survivors. The alterations in hormonal levels can influence IAs, while the rupture of an aneurysm can have various impacts on endocrine pathways and affect their outcome.

AREA COVERED

This review explores the reciprocal relationship between endocrinological changes (estrogen, growth hormone, and thyroid hormones) and IAs, as well as the effects of aneurysm ruptures on endocrine fluctuations.

EXPERT OPINION

Based on the data presented in this paper, we recommend further exploration into the influence of hormones on aneurysm formation and rupture. Additionally, we propose conducting endocrine assessments for patients who have experienced a rupture of IAs. Monitoring hormonal changes in patients with IAs could serve as a potential risk factor for rupture, leading to interventions in the approach to managing IAs.

Geometric influence of anterior cerebral artery rotation on the formation of anterior communicating artery aneurysm

OBJECTIVE

Several particular morphological factors that contribute to the hemodynamics of the anterior communicating artery (ACoA) have been documented, but no study has investigated the role of the degree of anterior cerebral artery (ACA) rotation on the presence of ACoA aneurysms (ACoAAs).

METHODS

A retrospective study of an institutional aneurysm database was performed; patients with ruptured or nonruptured ACoAAs were selected. Two sex- and age-matched control groups were identified: control Group A (nonaneurysms) and control Group B (middle cerebral artery aneurysms). Measurements of ACA rotation degree were obtained by using a three-dimensional imaging tool.

RESULTS

From 2015 to 2020, 315 patients were identified: 105 in the ACoAA group, 105 in control Group A, and 105 in control Group B. The average age at the time of presentation was 64 years, and 52.4% were female. The ACA rotation degree of the ACoAA group was significantly higher than that of control Group A (p <0.01). The A1 ratio and the A1A2 ratio of the ACoAA group were greater than those of control Group A (p <0.01 and p <0.01, respectively). The ACA rotation degree correlated insignificantly with aneurysm size in ACoAA patients (p=0.78). The ACA rotation degree in the ACoAA group was also insignificantly different from that in control B (p=0.11).

CONCLUSIONS

The degree of ACA rotation was greater in the ACoAA group than in the nonaneurysm group, and it may serve as an imaging marker for ACoAA.

Does the use of oral contraceptives or hormone replacement therapy offer protection against the formation or rupture of intracranial aneurysms in women?: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to carry out a systematic review of the literature with meta-analysis to evaluate the effect of using oral contraceptive and hormone replacement therapy as a protective factor in the formation of intracranial aneurysms and subarachnoid hemorrhage.

METHODS

This is a systematic review of the literature with meta-analysis, using PubMed and Embase as databases and the PRISMA method. Case-control and cohort studies published until December 2022 were included in this review.

RESULTS

Four studies were included in this review; three of which were eligible for meta-analysis. Regarding the use of oral contraceptive and the development of subarachnoid hemorrhage, there was a lower risk of aneurysm rupture with an odds ratio 0.65 (confidence interval 0.5-0.85). In the analysis of patients using hormone replacement therapy and developing subarachnoid hemorrhage, there was also a lower risk of aneurysm rupture with an OR 0.54 (CI 0.39-0.74). Only one article analyzed the formation of intracranial aneurysm and the use of hormone replacement therapy and oral contraceptive, and there was a protective effect with the use of these medications. oral contraceptive: OR 2.1 (CI 1.2-3.8) and hormone replacement therapy: OR 3.1 (CI 1.5-6.2).

CONCLUSION

The use of hormone replacement therapy and oral contraceptive has a protective effect in intracranial aneurysm rupture and formation.

Prevalence and risk factors of unruptured intracranial aneurysms in ischemic stroke patients - A global meta-analysis

Background

Unruptured intracranial aneurysms (UIAs) have an estimated global prevalence of 2.8% in the adult population; however, UIA was identified among more than 10% of ischemic stroke patients. Many epidemiological studies and reviews have pointed to the presence of UIA among patients with ischemic stroke; yet, the extent of this association is not fully known. We performed a systematic review and meta-analysis to determine the prevalence of UIA in patients admitted to hospitals with ischemic stroke and transient ischemic attack (TIA) at both global and continental levels and evaluate factors associated with UIA in this population.

Methods

We identified, in five databases, all studies describing UIA in ischemic stroke and TIA patients between January 1, 2000, and December 20, 2021. Included studies were of observational and experimental design.

Results

Our search yielded 3581 articles of which 23 were included, with a total of 25,420 patients. The pooled prevalence of UIA was 5% (95% confidence interval [CI] = 4-6%) with stratified results showing 6% (95% CI = 4-9%), 6% (95% CI = 5-7%), and 4% (95% CI = 2-5%) in North America, Asia, and Europe, respectively. Significant risk factors were large vessel occlusion (odds ratios [OR] = 1.22, 95% CI = 1.01-1.47) and hypertension (OR = 1.45, 95% CI = 1.24-1.69), while protective factors were male sex (OR = 0.60, 95% CI = 0.53-0.68) and diabetes (OR = 0.82, 95% CI = 0.72-0.95).

Conclusion

The prevalence of UIA is notably higher in ischemic stroke patients than the general population. Physicians should be aware of common risk factors in stroke and aneurysm formation for appropriate prevention.

Subarachnoid Hemorrhage During Pregnancy and Puerperium: A Population-Based Study

BACKGROUND

Pregnancy-related subarachnoid hemorrhage (pSAH) is rare, but it causes high mortality and morbidity. Nevertheless, data on pSAH are limited. The objectives here were to examine the incidence trends, causes, risk factors, and outcomes of pSAH in a nationwide population-based cohort study in Finland covering 30 years.

METHODS

We performed a retrospective population-based cohort study and nested case-control study in Finland for the period 1987-2016 (Stroke in Pregnancy and Puerperium in Finland). The Medical Birth Register was linked to the Hospital Discharge Register to identify women with incident stroke during pregnancy or puerperium. A subcohort of women with SAH is included in this analysis. The temporal connection of SAH to pregnancy and clinical details were verified from patient records.

RESULTS

The unadjusted incidence of pSAH was 3.21 (95% CI, 2.46-4.13) per 100 000 deliveries. No significant increase occurred in the incidence throughout the study period. However, the age of the mother had a significant increasing effect on the incidence. In total, 77% of patients suffered an aneurysmal pSAH, resulting in death in 16.3% of women and with only 68.2% achieving good recovery (modified Rankin Scale score 0-2) at 3 months. Patients with nonaneurysmal pSAH recovered well. The significant risk factors for pSAH were smoking (odds ratio, 3.27 [1.56-6.86]), prepregnancy hypertension (odds ratio, 12.72 [1.39-116.46]), and pre-eclampsia/eclampsia (odds ratio, 3.88 [1.00-15.05]).

CONCLUSIONS

The incidence of pSAH has not changed substantially over time in Finland. The majority of pSAH cases were aneurysmal and women with aneurysm had considerable mortality and morbidity. Counseling of pregnant women about smoking cessation and monitoring of blood pressure and symptoms of pre-eclampsia are important interventions to prevent pSAH.

Sex differences and risk factors for bleeding in Alagille syndrome

Spontaneous bleeds are a leading cause of death in the pediatric JAG1-related liver disease Alagille syndrome (ALGS). We asked whether there are sex differences in bleeding events in patients, whether Jag1Ndr/Ndr mice display bleeds or vascular defects, and whether discovered vascular pathology can be confirmed in patients non-invasively. We performed a systematic review of patients with ALGS and vascular events following PRISMA guidelines, in the context of patient sex, and found significantly more girls than boys reported with spontaneous intracranial hemorrhage. We investigated vascular development, homeostasis, and bleeding in Jag1Ndr/Ndr mice, using retina as a model. Jag1Ndr/Ndr mice displayed sporadic brain bleeds, a thin skull, tortuous blood vessels, sparse arterial smooth muscle cell coverage in multiple organs, which could be aggravated by hypertension, and sex-specific venous defects. Importantly, we demonstrated that retinographs from patients display similar characteristics with significantly increased vascular tortuosity. In conclusion, there are clinically important sex differences in vascular disease in ALGS, and retinography allows non-invasive vascular analysis in patients. Finally, Jag1Ndr/Ndr mice represent a new model for vascular compromise in ALGS.

Association of Reproductive Life Span and Age at Menopause With the Risk of Aneurysmal Subarachnoid Hemorrhage

BACKGROUND AND OBJECTIVES

Subarachnoid hemorrhage from cerebral aneurysm remains a devastating disease with high mortality and morbidity. Cerebral aneurysm and its rupture are more prevalent in postmenopausal women and have been postulated to be hormonally influenced. The goal of this study was to investigate the associations of female-specific factors, including reproductive life span, age at menarche, and age at menopause, with the incidence of aneurysmal subarachnoid hemorrhage (aSAH) in women.

METHODS

Participants in the Nurses' Health Study were followed up from 1980 or the time of reaching menopause until 2018. Only women with natural menopause or surgical menopause due to bilateral oophorectomy were included. Reproductive life span was defined by subtracting the age at menarche from the age at menopause. Multivariable-stratified proportional hazards models were used to study reproductive life span, age at menarche, and age at menopause with the incidence of aSAH. Multivariable models were adjusted for age, race, smoking, hysterectomy, hypertension, hyperlipidemia, body mass index, hormone therapy use, oral contraceptive use, and parity.

RESULTS

A total of 97,398 postmenopausal women with reproductive life span data were included; 138 participants developed aSAH, which was confirmed on medical record review by a physician. A shorter reproductive life span (≤35 years) was associated with a 2-fold higher incidence of aSAH after multivariable adjustment (hazard ratio [HR] 2.0 [95% CI 1.4-2.8]). Early age at menopause (age <45 years) was similarly associated with a higher risk of aSAH (HR 2.1 [95% CI 1.4-3.1]), but age at menarche was not. Use of oral contraceptives and postmenopausal hormone therapy was not associated with the incidence of aSAH.

DISCUSSION

An earlier age at menopause and a shorter reproductive life span duration (≤35 years) were associated with a higher risk of incident aSAH in women. No associations were noted for age at menarche, parity, oral contraceptive use, or postmenopausal therapy use.

What Are the Predictors of Intracranial Aneurysm Rupture in Indonesian Population Based on Angiographic Findings? Insight from Intracranial Aneurysm Registry on Three Comprehensive Stroke Centres in Indonesia

Objectives

What are the Predictors of Intracranial Aneurysm (IA) Rupture based on angiographic findings among patients in Indonesia's Population Based on Angiographic Findings.

Materials and Methods

We conducted a cross-sectional study on subjects with IA not caused by congenital aetiologies or other vascular malformations with cerebral angiography performed from January 2017 to January 2021. Demographic data and aneurysm profile, which include aneurysm count, size, location, and rupture event, were collected. The correlation between risk factors and IA rupture events was determined using bivariate and multivariate analysis.

Results

From 100 angiography data (33 males and 67 females), the mean subject age is 51.94 ± 10.78. We observe a total of 121 IAs from all subjects. Most of the IAs are in the anterior circulation (104 aneurysms, 85.96%), have small size (77 aneurysms, 63.64%), and are found in ruptured conditions (90 aneurysms, 74.38%). Males have a greater aneurysm count (1.36 ± 0.74 vs. 1.13 ± 0.55, p = 0.036) and larger aneurysm size (p = 0.002). Aneurysm size is significantly correlated with its location (p = 0.008). Medium size (p = 0.019; OR 2.62, 95% CI 1.08-6.36) and location other than the internal carotid artery are associated with increased rupture event. Multivariate analysis revealed that gender (p = 0.031; aOR 5.37, 95% CI 1.17-24.70) is a significant risk factor of IA rupture event.

Conclusion

IA profiling will enable clinicians to determine the risk of rupture and treatment plans for the Indonesian population. Further studies with a larger sample size are required to confirm these findings.

Why Are Women Predisposed to Intracranial Aneurysm?

Intracranial aneurysm (IA) is a frequent and generally asymptomatic cerebrovascular abnormality characterized as a localized dilation and wall thinning of intracranial arteries that preferentially arises at the arterial bifurcations of the circle of Willis. The devastating complication of IA is its rupture, which results in subarachnoid hemorrhage that can lead to severe disability and death. IA affects about 3% of the general population with an average age for detection of rupture around 50 years. IAs, whether ruptured or unruptured, are more common in women than in men by about 60% overall, and more especially after the menopause where the risk is double-compared to men. Although these data support a protective role of estrogen, differences in the location and number of IAs observed in women and men under the age of 50 suggest that other underlying mechanisms participate to the greater IA prevalence in women. The aim of this review is to provide a comprehensive overview of the current data from both clinical and basic research and a synthesis of the proposed mechanisms that may explain why women are more prone to develop IA.

Diagnosis and Risk Factors for Intracranial Aneurysms in Autosomal Polycystic Kidney Disease: A cross-sectional study from the Genkyst Cohort

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is associated with an increased risk for developing intracranial aneurysms (IAs). We aimed to evaluate the frequency of diagnosis of IAs in the cross-sectional, population-based, Genkyst cohort, to describe ADPKD-associated IAs and to analyze the risk factors associated with the occurrence of IAs in ADPKD patients.

METHODS

Cross-sectional study performed in 26 nephrology centers from the Western part of France. All patients underwent genetic testing for PKD1/PKD2 and other cystogenes.

RESULTS

Among the 2449 Genkyst participants, 114 (4.65%) had a previous diagnosis of ruptured or unruptured IAs at inclusion, and ∼47% of them had a positive familial history for IAs. Most aneurysms were small and saccular and located in the anterior circulation; 26.3% of the patients had multiple IAs. The cumulative probabilities of a previous diagnosis of IAs were 3.9, 6.2 and 8.1% at 50, 60 and 70 y, respectively. While this risk appeared to be similar in male and female individuals <50 y, after that age, the risk continued to increase more markedly in female patients, reaching 10.8% vs 5.4% at 70 y. The diagnosis rate of IAs was more than twofold higher in PKD1 compared to PKD2 with no influence of PKD1 mutation type or location. In multivariate analysis, female sex, hypertension <35 y, smoking and PKD1 genotype were associated with an increased risk for diagnosis of IAs.

CONCLUSIONS

This study presents epidemiological data reflecting real-life clinical practice. The increased risk for IAs in postmenopausal women suggests a possible protective role of estrogen.

Helicobacter pylori Infection Acts as an Independent Risk Factor for Intracranial Atherosclerosis in Women Less Than 60 Years Old

Background: Studies show inconsistent results regarding the relationship between Helicobacter pylori (H. pylori) infection and stroke. The present study assessed a potential association between H. pylori infection and an important risk factor for stroke, intracranial atherosclerosis.

Methods: In total, 15,798 subjects with transcranial Doppler (TCD) and 13C-urea breath test (13C-UBT) were enrolled from March 2012 to March 2017. Intracranial atherosclerosis was further measured using intracranial carotid artery calcification (ICAC) on past or recent head CT, and 14,084 subjects were ultimately included in the study. Baseline demographics, atherosclerosis risk factors, and laboratory results were investigated. Since endothelial dysfunction is critical to the development of atherosclerosis, the role of H. pylori in migration, tube formation, and proliferation of human brain microvascular endothelial cells (HBMECs) was assessed in vitro.

Results: The intracranial atherosclerosis group had a higher proportion of women and a greater rate of H. pylori infection than those without intracranial atherosclerosis. H. pylori infection was significantly more common in women with intracranial atherosclerosis than males. In addition, the incidence of intracranial atherosclerosis was significantly higher in women with H. pylori infection than uninfected women (53.8 vs. 46.4%, p &lt; 0.001). In an adjusted model, H. pylori was shown to be an independent risk factor for intracranial atherosclerosis in women ≤ 60 years of age [odds ratio (OR) = 2.261, 95% CI = 1.839–2.780, p &lt; 0.001]. Serum exosomes from patients with H. pylori infection had significantly reduced brain endothelial cell migration, tube formation, and proliferation in vitro.

Conclusion:Helicobacter pylori infection may be an important independent risk factor for intracranial atherosclerosis in women ≤ 60 years of age.

Epidemiological Characteristics and Surgical Outcomes of Unruptured Intracranial Aneurysms: A Real-world Study

BACKGROUND: This study was aimed at epidemiological analysis of unruptured intracranial aneurysms (IAs) regarding their location, size, multiplicity, type of intervention provided, and associated complications in the Kazakhstani population. METHODS: We performed a retrospective analysis of a cohort of 400 patients diagnosed with IA admitted to the Central Clinical Hospital of Almaty, Republic of Kazakhstan, a referral hospital for the treatment of cerebrovascular disease. Patients admitted between January 1, 2019 and December 31, 2019 with radiologically confirmed diagnosis of unruptured IA were included in the study. RESULTS: Overall, there were 400 patients with a 2.8 female/male ratio. The bulk of aneurisms – 96.0% – were of size <25 mm in diameter and single. Median age of patients was 55 years and the youngest patient was 22-years-old, while the oldest patient aged 83 years. The left internal carotid artery (ICA) was the most common site if IA localization followed by the right ICA. The left and right middle cerebral arteries were the second most common localization sites. More than a half of patients presented with aneurysm-related complications before the intervention, of which subarachnoid hemorrhage was the most common type. Embolization with or without stenting was performed in more than 50% of patients and 96.5% of all surgeries were not associated with complications. CONCLUSION: There is a need for careful consideration of clinical characteristics and surgical outcomes of patients with unruptured IA in a real-world practice as these data are needed for the development of management strategies.

Formation, Growth, or Rupture of De Novo Intracranial Aneurysms: Long-Term Follow-up Study of Subarachnoid Hemorrhage Survivors

BACKGROUND

The survival rate of aneurysmal subarachnoid hemorrhage (aSAH) has gradually increased, leading to more clinical cases of de novo intracranial aneurysms (DNIAs).

OBJECTIVE

To identify the characteristics of patients with DNIA growth or rupture.

METHODS

We included 1601 patients with aSAH treated by clipping from January 1993 to May 2010. According to the inclusion and exclusion criteria, 233 patients had no DNIAs, and 63 patients had 77 DNIAs. We assessed the incidence rate of DNIAs and risk factors for DNIA formation. After dichotomizing the DNIA group into the heed (patients with DNIA rupture or growth) and stable groups (patients without DNIA growth), we assessed the risk factors for DNIA growth or rupture.

RESULTS

The total follow-up period was 4427.9 patient-years. The incidence rate per patient-year was 1.42%. Age ≤50 yr, family history of aneurysm, and multiplicity at initial aSAH were significant risk factors for DNIA formation. Multivariate regression analysis revealed that female sex (odds ratio [OR], 5.566; 95% confidence interval [CI], 1.241-24.952), duration from initial aSAH to DNIA detection <120 mo (OR, 5.043; 95% CI, 1.362-18.668), multiplicity at initial aSAH (OR, 4.859; 95% CI, 1.207-19.563), and maximum DNIA diameter ≥4 mm (OR, 11.104; 95% CI, 2.337-52.772) were significant risk factors for DNIA growth or rupture.

CONCLUSION

DNIAs had a higher incidence rate than expected. Taking into account the presented incidence rate and risk factors, long-term surveillance in aSAH survivors for more than a decade may be worth considering, at least on a case-by-case basis.

A Sinister Gut Feeling

Women are generally spared from abdominal aortic aneurysm (AAA) formation by the immunomodulating effects of estrogen. However, once they develop it, especially in the postmenopausal group, its behavior is more sinister with rapid expansion, a higher tendency to rupture, and higher mortality as compared to the male counterparts. Reported here is a case of AAA in a postmenopausal woman who came to the outpatient department with low backache, vague abdominal pain, and dysuria which initially gave a picture of pelvic inflammation with urinary tract infection but was later found out to be aortic aneurysm.

Roles of Phytoestrogen in the Pathophysiology of Intracranial Aneurysm

[Figure: see text].

Sex-related differences in wall remodeling and intraluminal thrombus resolution in a rat saccular aneurysm model

OBJECTIVE

Intracranial aneurysms (IAs) are more often diagnosed in women. Hormones and vessel geometry, which influences wall shear stress, may affect pathophysiological processes of the arterial wall. Here, the authors investigated sex-related differences in the remodeling of the aneurysm wall and in intraluminal thrombus resolution.

METHODS

A well-characterized surgical side-wall aneurysm model was used in female, male, and ovariectomized rats. Decellularized grafts were used to model highly degenerated and decellularized IA walls and native grafts to model healthy IA walls. Aneurysm growth and thrombus composition were analyzed at 1, 7, 14, and 28 days. Sex-related differences in vessel wall remodeling were compared with human IA dome samples of men and pre- and postmenopausal women.

RESULTS

At 28 days, more aneurysm growth was observed in ovariectomized rats than in males or non-ovariectomized female rats. The parent artery size was larger in male rats than in female or ovariectomized rats, as expected. Wall inflammation increased over time in all groups and was most severe in the decellularized female and ovariectomized groups at 28 days compared with the male group. Likewise, in these groups the most elastin fragmentation was seen at 28 days. In female rats, on days 1, 7, and 14, the intraluminal thrombus was mainly composed of red blood cells and fibrin. On days 14 and 28, macrophage and smooth muscle cell invasion inside the thrombus was shown, leading to the removal of red blood cells and deposition of collagen and elastin. On days 14 and 28, similar profiles of thrombus reorganization were observed in male and ovariectomized female rats. However, collagen content in thrombi and vessel wall macrophage content were higher in aneurysms of male rats at 28 days than in those of female rats. On day 28, thrombus coverage by endothelial cells was lower in ovariectomized than in female or male rats. Finally, analysis of human IA domes showed that endothelial cell coverage was lower in men and postmenopausal women than in younger women.

CONCLUSIONS

Aneurysm growth and intraluminal thrombus resolution show sex-dependent differences. While certain processes (endothelial cell coverage and collagen deposition) point to a strong hormonal dependence, others (wall inflammation and aneurysm growth) seem to be influenced by both hormones and parent artery size.

Roles of inflammation in the natural history of intracranial saccular aneurysms

Aneurysmal subarachnoid hemorrhage is caused by intracranial aneurysm (IA) rupture and results in high rates of mortality and morbidity. Factors contributing to IA generation, growth and rupture can involve genetics, injury, hemodynamics, environmental factors, and inflammation, in which inflammatory factors are believed to play central roles in the whole natural history. Inflammatory reactions that contribute to IA development may involve synthesis of many functional proteins and expression of genes induced by changes of blood flow, external stimuli such as smoking, internal balance such as hormonal status changes, and blood pressure. Meanwhile, inflammatory reactions itself can evoke inflammatory cytokines release and aggregation such as MMPs, MCP-1, TNF-α and ZO-1, directly or indirectly promoting aneurysm growth and rupture. However, the details of these inflammatory reactions and their action on inflammatory chemokines are still unknown. Moreover, some agents with the function of anti-inflammation, lipid-lowering, antihypertension or inflammatory factor inhibition may have the potential benefit to reduce the risk of aneurysm development or rupture in a group of population despite the underlying mechanism remains unclear. Consequently, we reviewed the potential inflammatory responses and their mechanisms contributing to aneurysm development and rupture and sought intervention targets that may prevent IA rupture or generation.

Risk factors involved in the formation of multiple intracranial aneurysms

BACKGROUND

Although several risk factors of the multiple intracranial aneurysms (MIAs) formation has been reported, the results are controversial. We aimed to find out the risk factors of MIAs formation by analyzing our clinic data combined with a meta-analysis.

MATERIAL AND METHODS

A retrospective review work of medical records for the patients with aneurysms was undertaken. Univariate analysis was used to examine all mentioned variables. Binary logistic regression analysis was used to identify the risk factors of MIAs formation.

RESULTS

In the retrospective review work, a total of 565 patients with aneurysm were included in this study. Of these 565 participants, 449 patients suffered SIAs and 116 patients suffered MIAs. Univariate analysis showed a significant difference in terms of female, cigarette smoking, family history of hypertension, and primary hypertension between the SIAs and MIAs group. The binary logistic regression analysis showed that the female (OR = 1.624), primary hypertension (OR = 1.563), and family history of hypertension (OR = 2.496) were independent risk factors of the formation of MIAs (for each P < 0.05). With regard to the meta-analysis results, it revealed that there was significant difference in the rates of female (P < 0.001), cigarette smoking (P < 0.001), primary hypertension (P = 0.001), and higher age (P = 0.011) among the MIAs patients.

CONCLUSIONS

A higher rate of the formation of MIAs is closely associated with the elder and female. Patients with hypertension history, cigarette smoking, and family primary hypertension history also affected the formation of MIAs, these risk factors should be a guard against.

Risk factors for subarachnoid haemorrhage: a nationwide cohort of 950 000 adults

BACKGROUND

Subarachnoid haemorrhage (SAH) is a devastating disease, with high mortality rate and substantial disability among survivors. Its causes are poorly understood. We aimed to investigate risk factors for SAH using a novel nationwide cohort consortium.

METHODS

We obtained individual participant data of 949 683 persons (330 334 women) between 25 and 90 years old, with no history of SAH at baseline, from 21 population-based cohorts. Outcomes were obtained from the Swedish Patient and Causes of Death Registries.

RESULTS

During 13 704 959 person-years of follow-up, 2659 cases of first-ever fatal or non-fatal SAH occurred, with an age-standardized incidence rate of 9.0 [95% confidence interval (CI) (7.4-10.6)/100 000 person-years] in men and 13.8 [(11.4-16.2)/100 000 person-years] in women. The incidence rate increased exponentially with higher age. In multivariable-adjusted Poisson models, marked sex interactions for current smoking and body mass index (BMI) were observed. Current smoking conferred a rate ratio (RR) of 2.24 (95% CI 1.95-2.57) in women and 1.62 (1.47-1.79) in men. One standard deviation higher BMI was associated with an RR of 0.86 (0.81-0.92) in women and 1.02 (0.96-1.08) in men. Higher blood pressure and lower education level were also associated with higher risk of SAH.

CONCLUSIONS

The risk of SAH is 45% higher in women than in men, with substantial sex differences in risk factor strengths. In particular, a markedly stronger adverse effect of smoking in women may motivate targeted public health initiatives.

The Bilateral Ovariectomy in a Female Animal Exacerbates the Pathogenesis of an Intracranial Aneurysm

Considering the poor outcome of subarachnoid hemorrhage (SAH) due to the rupture of intracranial aneurysms (IA), mechanisms underlying the pathogenesis of IAs, especially the rupture of lesions, should be clarified. In the present study, a rat model of IAs in which induced lesions spontaneously ruptured resulting in SAH was used. In this model, the combination of the female sex and the bilateral ovariectomy increased the incidence of SAH, similar to epidemiological evidence in human cases. Importantly, unruptured IA lesions induced in female animals with bilateral ovariectomy were histopathologically similar to ruptured ones in the presence of vasa vasorum and the accumulation of abundant inflammatory cells, suggesting the exacerbation of the disease. The post-stenotic dilatation of the carotid artery was disturbed by the bilateral ovariectomy in female rats, which was restored by hormone replacement therapy. The in vivo study thus suggested the protective effect of estrogen from the ovary on endothelial cells loaded by wall shear stress. β-estradiol or dihydrotestosterone also suppressed the lipopolysaccharide-induced expression of pro-inflammatory genes in cultured macrophages and neutrophils. The results of the present study have thus provided new insights about the process regulating the progression of the disease.

Estrogen receptor alpha gene variant, PvuII (rs2234693), as a potential pharmacogenetic biomarker for aneurysmal subarachnoid hemorrhage in postmenopausal women

Aneurysmal subarachnoid hemorrhage (aSAH) occurs more often in postmenopausal women than in men. Estrogen plays an important role in vascular homeostasis. Our aim was to elucidate whether a drop in circulating estradiol in conjunction with variants of estrogen receptor genes have a role in female gender susceptibility to aSAH. A total of 709 subjects were enrolled (349 aSAH patients, 360 controls) and genotyped for rs2234693 or PvuII (intron 1, T>C) in the ESR1 gene and rs4986938 or AluI (exon 8, 1730G>A) of ESR2 gene by PCR-RFLP. Serum estradiol was estimated by ELISA. Estrogen receptor gene expression was studied by qRT-PCR. Logistic regression analysis indicated a significant recessive effect of the T allele of PvuII on aSAH in females, and this association remained statistically significant even after adjusting for confounders (OR 1.702, CI 95% 1.062, 2.726, P value = 0.027). ESR1 gene expression was significantly reduced (P value = 0.0089) in subjects carrying PvuII T allele. In postmenopausal women with TT genotype and low serum estradiol, the odds for developing aSAH were found to be 3.5-fold increase compared with premenopausal women (CI 95% 1.424-8.828, P value = 0.0074). However, this variant showed no significant association with aSAH in men. No significant difference was found in genotype and allelic distribution of AluI polymorphism in ESR2 gene, between patients and controls. We propose that the PvuII T allele could be a potential pharmacogenetic marker for strategizing personal medicine for preventing aSAH in postmenopausal women with low circulating estradiol. Further larger studies in other population are warranted.

Epidemiological analysis of 1404 patients with intracranial aneurysm followed in a single Brazilian institution

Background:

We sought to evaluate the epidemiology of intracranial aneurysms in relation to location, gender, age, presence of multiple aneurysms, and comorbidities in the Brazilian population.

Methods:

We performed a prospective analysis of a cohort of 1404 patients diagnosed with intracranial aneurysm admitted to the Hospital das Clinicas of the University of Sao Paulo, a referral hospital for the treatment of cerebrovascular diseases in Brazil. Patients admitted between September 2009 and September 2018 with radiological diagnosis of intracranial aneurysm were included in the study.

Results:

A total of 2251 aneurysms were diagnosed. Females accounted for 1090 aneurysms (77.6%) and the mean age at diagnosis was 54.9 years (ranging 15–88). The most common location was middle cerebral artery (MCA) with 593 aneurysms (26.3%) followed by anterior cerebral artery (ACA) with 417 aneurysms (18.5%) and internal carotid artery in the posterior communicating segment with 405 aneurysms (18.0%). Males had higher rates of ACA aneurysms (29.7%) while females had higher rates of MCA aneurysms (26.1%). Sorting by size, 492 aneurysms were <5 mm (21.8%), 1524 measured 5–10 mm (67.7%), 119 size 11–24 mm (5.3%), and 116 were >24 mm (5.2%). The occurrence of multiple aneurysms was associated with female gender (P < 0.001) and smoking (P < 0.001), but not with hypertension (P = 0.121).

Conclusion:

In this population, the occurrence of intracranial aneurysm is related to several factors, including gender, age, smoking, and hypertension. Our study brought to light important characteristics of a large number of Brazilian patients regarding epidemiology, location, size, and multiplicity of intracranial aneurysms.

Sex differences in risk factors for aneurysmal subarachnoid haemorrhage: Systematic review and meta-analysis

BACKGROUND

Aneurysmal subarachnoid haemorrhage (aSAH) disproportionally affects women. We conducted a systematic review and meta-analysis to explore sex differences in aSAH risk factors.

METHODS

Case-control/cohort studies were searched to November 2017 with sex-specific risk factors for aSAH. Meta-analysis was performed when a risk factor was reported in ≥2 studies.

RESULTS

Of 31 studies, 22 were eligible for meta-analysis. Female sex was associated with greater odds of aSAH (HR_adjusted 1.90 [1.47-2.46]. There was no detectable difference between the sexes for hypertension (OR_adjusted: men 3.13 [2.26-4.34]; women 3.65 [2.87-4.63], p = .18), smoking (OR_adjusted: men 2.96 [1.68-5.21]; women 3.11 [1.21-7.97], p = .95), aSAH family history, systolic blood pressure, age and some genetic variations. Alcohol (OR_adjusted: men 1.50 [1.04-2.17]; women 0.83 [0.48-1.45], p = .003), high alanine aminotransferase levels, and some gene variants increased the risk of aSAH in men. Reproductive factors, divorce and some genetic variations increased the risk in women. High aspartate aminotransferase levels in men and, diabetes (OR_adjusted: men 0.57 [0.32-1.01]; women 0.24 [0.13-0.43], p = .01) and parity in women reduced aSAH risk.

CONCLUSION

We recommend sex-specific re-analysis of existing studies of aSAH risk factors. Known aSAH risk factors (hypertension, smoking and alcohol consumption) should be targeted to prevent aSAH in men and women. Registration PROSPERO (ID: CRD42018091521).

Influence of sex and hormonal status on initial impact and neurocognitive outcome after subarachnoid haemorrhage in rats

The aim of this study was to detect differences in functional outcome after experimental subarachnoid haemorrhage (SAH) in rodents with different hormonal status. For this purpose, the endovascular perforation model was applied to four groups of Sprague-Dawley-Rats: male intact, male neutered, female intact and female neutered animals. Initial impact was measured by ICP, CPP and cerebral blood flow in the first hour after SAH. From day 4-14, the modified hole board test was applied to assess functional and neuro-cognitive outcome. Histological outcome was examined in the motor cortex and hippocampus of each hemisphere. Mortality was highest in the female intact group albeit not statistically significant. Physiologic parameters did not differ significantly between groups either. In the modified hole board test, male intact animals showed a greater impairment of declarative memory than the female intact and neutered groups. However, male intact animals showed greater avoidance behaviour and male animals revealed higher anxiety levels independent of hormonal status. No differences in histological damage of hippocampus and motor cortex between groups could be shown. We therefore speculate that the marginal deficits in cognitive performance that are shown by the male intact group in the modified hole board test are mostly caused by higher anxiety levels and cannot be interpreted as pure cognitive impairment.

Associations of hemodynamics, morphology, and patient characteristics with aneurysm rupture stratified by aneurysm location

PURPOSE

The mechanisms of cerebral aneurysm rupture are not fully understood. We analyzed the associations of hemodynamics, morphology, and patient age and gender with aneurysm rupture stratifying by location.

METHODS

Using image-based models, 20 hemodynamic and 17 morphological parameters were compared in 1931 ruptured and unruptured aneurysms with univariate logistic regression. Rupture rates were compared between males and females as well as younger and older patients and bifurcation versus sidewall aneurysms for different aneurysm locations. Subsequently, associations between hemodynamics and morphology and patient as well as aneurysm characteristics were analyzed for aneurysms at five locations.

RESULTS

Compared to unruptured aneurysms, ruptured aneurysms were characterized by a more irregular shape and were exposed to a more adverse hemodynamic environment described by faster flow, higher wall shear stress, more oscillatory shear, and more unstable and complex flows. These associations with rupture status were consistent for different aneurysm locations. Rupture rates were significantly higher in males at the internal carotid artery (ICA) bifurcation, ophthalmic ICA, and the middle cerebral artery (MCA) bifurcation. At the anterior communicating artery (ACOM) and MCA bifurcation, they were significantly higher for younger patients. Bifurcation aneurysms had significantly larger rupture rates at the MCA and posterior communicating artery (PCOM). In these groups with higher rupture rates, aneurysms were characterized by adverse hemodynamics and more complex shapes.

CONCLUSION

Hemodynamic and morphological differences between ruptured and unruptured aneurysms are consistent across locations. Adverse morphology and hemodynamics are related to rupture as well as younger age, male gender, and bifurcation aneurysms.

Cerebral Aneurysms Differ in Patients with Hysterectomies

OBJECTIVE

Female sex is a well-known risk factor for aneurysm formation. Although the role of the ovaries and estrogen in aneurysm development has been supported, other organ-hormone pairs unique between sexes also may be implicated. In this study, we aimed to determine whether intracranial aneurysms microsurgically clipped in patients with previous hysterectomies exhibit any unique aneurysm characteristics from those without hysterectomies.

METHODS

Solitary aneurysms microsurgically treated by the senior author (M.T.L.) were included from a database of patients treated between January 2010 and April 2013 at a tertiary academic medical center. Only female patients and patients equal or older in age to the youngest patient in the hysterectomy group were included in the control group. Patient and aneurysm characteristics were compared using the χ² test for categorical variables and the independent t test analysis for continuous variables.

RESULTS

A total 233 patients were included in the study. Forty-three patients (19%) had undergone a previous hysterectomy; none had oophorectomies recorded. No difference in mean age (P = 0.89), hypertension (P = 0.38), alcohol use (P = 0.87), tobacco use (P = 0.22), or aneurysm location (P = 1) existed. However, patients in the hysterectomy group more often presented in a good neurologic condition before surgery (88% vs. 74%, P = 0.04) and had fewer large aneurysms (8% vs. 24%, P = 0.03). Also, fewer presented with a ruptured aneurysm (28%) then the nonhysterectomy group (51%) (P = 0.004).

CONCLUSIONS

Female patients with a surgical history of a hysterectomy have a lower rate of large aneurysms, present in better neurologic condition, and are less likely to present with a ruptured aneurysm than females without a hysterectomy.

The role of inflammation and potential pharmacological therapy in intracranial aneurysms

Intracranial aneurysms remain important clinical concern. There is relatively low risk of rupture of symptomless aneurysms incidentally found in MRA or CTA performed due to other indications. Not all of the intracranial aneurysms should or can be treated with neurosurgery intervention or endovascular embolization. Clinical strategy for small, symptomless, unruptured aneurysms is still questionable. Mechanisms underlying aneurysms formation, progression and rupture are poorly understood. Inflammation is one of the factors suspected to participate in these processes. Therefore the aim of this manuscript is to present current state of knowledge about the role of inflammation in the formation and progression of intracranial aneurysms and in their rupture process. Current knowledge about possible pharmacological treatment of intracranial aneurysms will also be presented. Macrophages infiltration seems to participate in the formation of intracranial aneurysms. Inhibition of signals sent by macrophages may prevent the aneurysms formation. Inflammation present in the wall of the aneurysm seems to be also related to the aneurysm's rupture risk. However it does not seem to be the only cause of the degeneration, but it can be a possible target of drug therapy. Some preliminary studies in humans indicate the potential role of aspirin as a factor that decrease the level of inflammation and lower the risk of rupture of intracranial aneurysms. However further research including a greater number of subjects and a prospective randomized design are necessary to assess the role of aspirin in preventing strategy for small, symptomless, unruptured intracranial aneurysms.

Sex differences in delayed cerebral ischemia after subarachnoid hemorrhage

OBJECTIVE

In this study the authors sought to investigate the sex differences in the risk of delayed cerebral ischemia (DCI), delayed cerebral infarction, and the role of hormonal status.

METHODS

Ten studies included in the SAHIT (SAH International Trialists) repository were analyzed using a fitting logistic regression model. Heterogeneity between the studies was tested using I2 statistics, and the results were pooled using a random-effects model. Multivariable analysis was adjusted for the effects of neurological status and fixed effect of study. An additional model was examined in which women and men were split into groups according to an age cut point of 55 years, as a surrogate to define hormonal status.

RESULTS

A pooled cohort of 6713 patients was analyzed. The risk of DCI was statistically significantly higher in women than in men (OR 1.29, 95% CI 1.12–1.48); no difference was found with respect to cerebral infarction (OR 1.17, 95% CI 0.98–1.40). No difference was found in the risk of DCI when comparing women ≤ 55 and > 55 years (OR 0.87, 95% CI 0.74–1.02; p = 0.08) or when comparing men ≤ 55 and > 55 years (p = 0.38). Independent predictors of DCI were World Federation of Neurosurgical Societies (WFNS) grade, Fisher grade, age, and sex. Independent predictors of infarction included WFNS grade, Fisher grade, and aneurysm size.

CONCLUSIONS

Female sex is associated with a higher risk of DCI. Sex differences may play a role in the pathogenesis of DCI but are not associated with menopausal status. The predictors of DCI and cerebral infarction were identified in a very large cohort and reflect experience from multiple institutions.

The role of inflammation and potential use of sex steroids in intracranial aneurysms and subarachnoid hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (aSAH) continues to be a devastating neurological condition with a high risk of associated morbidity and mortality. Inflammation has been shown to increase the risk of complications associated with aSAH such as vasospasm and brain injury in animal models and humans. The goal of this review is to discuss the inflammatory mechanisms of aneurysm formation, rupture and vasospasm and explore the role of sex hormones in the inflammatory response to aSAH.

Methods

A literature review was performed using PubMed using the following search terms: "intracranial aneurysm," "cerebral aneurysm," "dihydroepiandrosterone sulfate" "estrogen," "hormone replacement therapy," "inflammation," "oral contraceptive," "progesterone," "sex steroids," "sex hormones" "subarachnoid hemorrhage," "testosterone." Only studies published in English language were included in the review.

Results

Studies have shown that administration of sex hormones such as progesterone and estrogen at early stages in the inflammatory cascade can lower the risk and magnitude of subsequent complications. The exact mechanism by which these hormones act on the brain, as well as their role in the inflammatory cascade is not fully understood. Moreover, conflicting results have been published on the effect of hormone replacement therapy in humans. This review will scrutinize the variations in these studies to provide a more detailed understanding of sex hormones as potential therapeutic agents for intracranial aneurysms and aSAH.

Conclusion

Inflammation may play a role in the pathogenesis of intracranial aneurysm formation and subarachnoid hemorrhage, and administration of sex hormones as anti-inflammatory agents has been associated with improved functional outcome in experimental models. Further studies are needed to determine the therapeutic role of these hormones in the intracranial aneurysms and aSAH.

Intracranial aneurysms: Review of current science and management

Unruptured intracranial aneurysms often have a relatively benign clinical course. Frequently, they are found incidentally during workup for an underlying, possibly related or unrelated, symptom or condition. Overall, brain aneurysms are considered to have a relatively low annual risk of rupture. However, should it occur, aneurysmal subarachnoid hemorrhage can lead to significant morbidity and mortality. Our understanding of the natural history and treatment outcomes of cerebral aneurysms has significantly increased over the last few decades, but choosing the optimal management for each patient requires the careful consideration of numerous medical, clinical and anatomic factors. The purpose of this review is to help physicians and caregivers, who may participate in the diagnosis, counseling and triage of patients with brain aneurysms, understand the basic elements of decision making. We discuss natural history, risk factors, screening, presentation, diagnosis, and their implications on aneurysm management and long-term follow-up. We also provide an overview of the risks and benefits of currently available treatment options.

Apolipoprotein E polymorphism and the risk of aneurysmal subarachnoid hemorrhage in a South Indian population

Background

The rupture of a brain aneurysm causes bleeding in the subarachnoid space. This is known as aneurysmal subarachnoid hemorrhage (aSAH). We evaluated the association of apolipoprotein E (APOE) polymorphism and the risk of aSAH in a South Indian population.

Methods

The study was performed on 200 subjects with aSAH and 253 healthy control subjects. Blood samples (5 ml) were used to isolate DNA and genotyping was performed for rs7412 and rs429358 using a Taqman allelic discrimination assay. Statistical software R.3.0.11 was used to statistically analyze the data and a p value < 0.05 was considered as statistically significant.

Results

We found a significant association with the risk of aSAH in ε3/ ε4 genetic model (OR = 1.91, 95% CI = 1.16-3.14, p = 0.01). However, in the other genetic models and allele frequency, there was no significant association with the risk of aSAH. In subtyping, we found a significant association of ε2 allele frequency with posterior communicating artery (PCOM) aneurysm (OR = 3.59, 95% CI = 1.11-11.64, p = 0.03).

Conclusion

Our results suggest that APOE polymorphism has an influence on the risk of aSAH in this South Indian population, specifically in the PCOM subtype.

Bazedoxifene, a selective estrogen receptor modulator, reduces cerebral aneurysm rupture in Ovariectomized rats

Background

Estrogen deficiency is thought to be responsible for the higher frequency of aneurysmal subarachnoid hemorrhage in post- than premenopausal women. Estrogen replacement therapy appears to reduce this risk but is associated with significant side effects. We tested our hypothesis that bazedoxifene, a clinically used selective estrogen receptor (ER) modulator with fewer estrogenic side effects, reduces cerebral aneurysm rupture in a new model of ovariectomized rats.

Methods

Ten-week-old female Sprague-Dawley rats were subjected to ovariectomy, hemodynamic changes, and hypertension to induce aneurysms (ovariectomized aneurysm rats) and treated with vehicle or with 0.3 or 1.0 mg/kg/day bazedoxifene. They were compared with sham-ovariectomized rats subjected to hypertension and hemodynamic changes (HT rats). The vasoprotective effects of bazedoxifene and the mechanisms underlying its efficacy were analyzed.

Results

During 12 weeks of observation, the incidence of aneurysm rupture was 52% in ovariectomized rats. With no effect on the blood pressure, treatment with 0.3 or 1.0 mg/kg/day bazedoxifene lowered this rate to 11 and 17%, almost the same as in HT rats (17%). In ovariectomized rats, the mRNA level of ERα, ERβ, and the tissue inhibitor of metalloproteinase-2 was downregulated in the cerebral artery prone to rupture at 5 weeks after aneurysm induction; the mRNA level of interleukin-1β and the matrix metalloproteinase-9 was upregulated. In HT rats, bazedoxifene restored the mRNA level of ERα and ERβ and decreased the level of interleukin-1β and matrix metalloproteinase-9. These findings suggest that bazedoxifene was protective against aneurysmal rupture by alleviating the vascular inflammation and degradation exacerbated by the decrease in ERα and ERβ.

Conclusions

Our observation that bazedoxifene decreased the incidence of aneurysmal rupture in ovariectomized rats warrants further studies to validate this response in humans.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-0966-7) contains supplementary material, which is available to authorized users.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

MRI Characterization in the Acute Phase of Experimental Subarachnoid Hemorrhage

A number of mechanisms have been proposed for the early brain injury after subarachnoid hemorrhage (SAH). In this study, we investigated the radiographic characteristics and influence of gender on early brain injury after experimental SAH. SAH was induced by endovascular perforation in male and female rats. Magnetic resonance imaging was performed in a 7.0-T Varian MR scanner at 24 h after SAH. The occurrence and size of T2 lesions, ventricular dilation, and white matter injury (WMI) were determined on T2-weighted images (T2WI). The effects of SAH on heme oxygenase-1 and fibrin/fibrinogen were examined by Western blotting and immunohistochemistry. SAH severity was assessed using a MRI grading system, and neurological function was evaluated according to a modified Garcia's scoring system. T2 hyperintensity areas and enlarged ventricles were observed in T2WI coronal sections 24 h after SAH. The overall incidence of T2 lesions, WMI, and hydrocephalus was 54, 20, and 63%, respectively. Female rats had a higher incidence of T2 hyperintensity lesions and hydrocephalus, as well as larger T2 lesion volumes and higher average ventricular volume. SAH rats graded at 3-4 (our previously validated MRI grading scale) had larger T2 lesion volumes, more hydrocephalus, and worse neurological function compared with those graded at 0-2. In conclusion, T2 lesion, WMI, and hydrocephalus were the most prevalent MRI characteristics 24 h after experimental SAH. The T2 lesion area matched with fibrinogen/fibrin positive staining in the acute phase of SAH. SAH induced more severe brain injury in females compared to males in the acute phase of SAH.

Diabetes mellitus and the risk of aneurysmal subarachnoid haemorrhage: A systematic review and meta-analysis of current evidence

Objective

This systematic review aimed to define the relationship between diabetes mellitus (DM) and the risk of aneurysmal subarachnoid haemorrhage (aSAH).

Methods

Studies associated with DM and aSAH published until March 2016 were retrieved from Pubmed, Embase, Web of Science, and Cochrane Library databases. A random-effects model was used to calculate the relative risks (RRs) with 95% confidence intervals (CIs).

Results

Eighteen observational studies were retrieved. The overall RRs for DM and aSAH were RRs = 0.59 (0.44, 0.79), with moderate heterogeneity (I²= 55.7%, P_{heterogeneity} = 0.000). Subgroup analysis by study quality revealed a reduced association between DM and aSAH risk in high quality studies only (RRs = 0.40, 95% CI: 0.29, 0.56; I²= 0.0%, P_{heterogeneity} = 0.549), therefore study quality may be a source of heterogeneity.

Conclusion

A potential decreased risk of aSAH in DM patients was found in high quality studies. Further studies are required to confirm this causal relationship and to investigate the biological mechanisms.

A higher aneurysmal subarachnoid hemorrhage incidence in women prior to menopause: a retrospective analysis of 4,895 cases from eight hospitals in China

BACKGROUND

Subarachnoid hemorrhage (SAH) from a ruptured cerebral aneurysm is a devastating disease. Despite the risk factors, including hypertension, cigarette smoking and alcohol use, are more common in men, aneurysmal SAH belongs to a few diseases which the incidence is higher in women than in men. Sex hormones, especially estrogen, might be protective against this condition. Hormone replacement therapy (HRT) seems to be associated with a reduced risk for aneurysmal SAH. This study aims to know the prevalence of aneurysmal SAH of men and women at different ages.

METHODS

The age and gender information of 4,895 case of aneurysmal SAH (3,016 females, 1,879 males) were collected retrospectively from eight institutions in mainland China. The prevalence of aneurysmal SAH of men and women at different ages was analyzed.

RESULTS

The data showed women had a higher incidence of aneurysmal SAH than men starting at late thirties, and men might have a higher incidence of aneurysmal SAH than women only before 37-year-old.

CONCLUSIONS

Menopause may not be the only dominant factor causing higher incidence of aneurysmal SAH in women than in men.

Aneurysmal Subarachnoid Hemorrhage in Pregnancy-Case Series, Review, and Pooled Data Analysis

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) during pregnancy represents an important cause of maternal and fetal morbidity and mortality. Approaches to diagnostics and treatment are still controversial, and there are only a limited number of cases described in the literature. Our study examines the management of aSAH in pregnant patients, creating a case series by combining patients from our hospital records with those from the limited available literature.

METHODS

Data collected from Addenbrooke's Hospital records and cases published between January 1995 and January 2015 were studied. Chi-square test, exact Fisher's test, and chi-square test for trend were used for analyzing categorical data, while the t-test and Mann-Whitney-Wilcoxon test were used for continuous data.

RESULTS

Fifty-two patients were included. The mean age was 31.47 ± 5.80, and most patients were in their third trimester. A univariate pooled data analysis suggested that the maternal outcome may depend on the mother's age, mother's Hunt and Hess scale score, Glasgow Coma Scale at arrival, treatment modality for the aneurysm, mode, and timing of delivery. However, at the multivariate analysis only the presence of general complications resulted in a significant impact on maternal outcome.

CONCLUSIONS

Ruptured aneurysms in pregnant patients with aSAH may be safely secured in a timely manner. The diagnostic and treatment strategy for each of these patients should consider peculiar maternal and obstetric factors and requires a multidisciplinary assessment involving obstetrics, neurosurgeons, and intensivists. Considering the observed statistical power of our series, our findings should be taken with caution and should be supported by further systematic data collection.

Parity and Risk of Stroke among Chinese Women: Cross-sectional Evidence from the Dongfeng-Tongji Cohort Study

Epidemiological studies have investigated the association between parity and the risk of stroke, but the results have been inconsistent. The objective of this study was to assess the association among middle-aged and older Chinese women. We used data from the Dongfeng-Tongji Cohort Study. In total, 14,277 women were included in the analysis. Participants were classified into four groups according to parity. Stroke cases were self-reported during face-to-face interviews. Multivariable logistic regression models were used to investigate the association between parity and the risk of stroke while controlling for potential confounders. The prevalence of stroke among the study subjects was 2.7% (380 of 14,277). In the fully adjusted model, women who had experienced two, three, or four or more live births had 1.24 times (95% CI, 0.85-1.81), 1.97 times (95% CI, 1.30-2.98) and 1.86 times (95% CI, 1.14-3.03), higher risk of stroke, respectively, compared with women who had experienced one live birth. High parity was associated with an increasing risk of stroke in the present study. Further longitudinal studies are needed to confirm the association and to explore the unclear mechanism underlying the link between parity and stroke risk.

Sex Differences in the Formation of Intracranial Aneurysms and Incidence and Outcome of Subarachnoid Hemorrhage: Review of Experimental and Human Studies

Intracranial aneurysms are defined as pathological dilatations of cerebral arteries and rupture of intracranial aneurysms leads to subarachnoid hemorrhage (SAH). The goal of this review was to outline the sex differences in the formation and progression of intracranial aneurysms as well as sex-related differences in incidence and outcome of SAH. The literature review was performed using PubMed with a combination of these search terms: "subarachnoid hemorrhage," "incidence," "outcome," "sex," "gender," "male," "female," "experimental," "mice," and "rats." Studies written in English were used. Female sex is thought to be a risk factor for aneurysm formation, especially in postmenopausal age populations, suggesting the potential protective involvement of sex steroids. Female sex is also considered a risk factor for SAH occurrence. Although incidence and mortality are confirmed to be higher in females in most studies, they elucidated no clear differences in the functional outcome among SAH survivors. The effect of gender on the pathophysiology of SAH is not very well understood; nevertheless, the majority of pre-clinical studies suggest a beneficial effect of sex steroids in experimental SAH. Moreover, conflicting results exist on the role and effect of hormone replacement therapies and oral contraceptive pills on the incidence and outcome of human SAH. Sex differences exist in the formation of aneurysms as well as the incidence and mortality of SAH. Potential therapeutic effects of sex steroids have been replicated in many animal studies, but their potential use in the treatment of acute SAH in human populations needs more future study.