Roles of hypertension in the rupture of intracranial aneurysms

Correlation of periodontal diseases with intracranial aneurysm formation: novel predictive indicators

Background

We investigated whether periodontal diseases, specifically, periodontitis and gingivitis, could be risk factors of the incidence of intracranial aneurysms (IAs).

Methods

We performed a case–control study to compare the differences in the periodontal disease parameters of 281 cases that were divided into the IAs group and non-IAs group. All cases underwent complete radiographic examination for IAs and examination for periodontal health.

Results

Comparing with those in the non-IAs group, the cases in the IAs group were older (53.95 ± 8.56 vs 47.79 ± 12.33, p < 0.001) and had a higher incidence of hypertension (76 vs 34, p = 0.006). Univariate logistic regression analysis revealed that age (> 50 years) and hypertension were predictive risk factors of aneurysm formation (odds ratio [OR] 1.047, 95% confidence interval [95% CI] 1.022–1.073, p < 0.001 and OR 2.047, 95% CI 1.232–3.401, p = 0.006). In addition, univariate and multivariate logistic regression analyses showed that the parameters of periodontal diseases, including gingival index, plaque index, clinical attachment loss, and alveolar bone loss, were significantly associated with the occurrence of IAs (all p < 0.05). For further statistical investigation, the parameters of periodontal diseases were divided into four layers based on the quartered data. Poorer periodontal health condition (especially gingival index > 1.1 and plaque index > 1.5) had the correlation with IAs formation (p = 0.007 and p < 0.001).

Conclusion

Severe gingivitis or periodontitis, combining with hypertension, is significantly associated with the incidence of IAs.

Association between longitudinal blood pressure and prognosis after treatment of cerebral aneurysm: A nationwide population-based cohort study

BACKGROUND

High blood pressure is a major risk factor for the development and rupture of cerebral aneurysm. Endovascular coil embolization and surgical clipping are established procedures to treat cerebral aneurysm. However, longitudinal data of blood pressure after the treatment of cerebral aneurysm and its impact on long-term prognosis are not well known.

METHODS

This retrospective cohort study included 1275 patients who underwent endovascular coil embolization (n = 558) or surgical clipping (n = 717) of cerebral aneurysm in 2002-2015 using the nationwide health screening database of Korea. Systolic and diastolic blood pressure of patients were repeatedly obtained from the nationwide health screening program. We performed a multivariate time-dependent Cox regression analysis of the primary composite outcome of stroke, myocardial infarction, and all-cause death.

RESULTS

During the mean follow-up period of 6.13 ± 3.41 years, 89 patients suffered the primary outcome. Among the total 3546 times of blood pressure measurement, uncontrolled high blood pressure (systolic ≥140 mmHg or diastolic ≥90 mmHg) was 22.9%. There was a significantly increased risk of primary outcome with high systolic (adjusted HR [95% CI] per 10 mmHg, 1.16 [1.01-1.35]) and diastolic (adjusted HR [95% CI] per 10 mmHg, 1.32 [1.06-1.64]) blood pressure.

CONCLUSIONS

High blood pressure is prevalent even in patients who received treatment for cerebral aneurysm, which is significantly associated with poor outcome. Strict control of high blood pressure may further improve the prognosis of patients with cerebral aneurysm.

Non-coding RNAs role in intracranial aneurysm: General principles with focus on inflammation

Intracranial aneurysm (IA) is one of the most challenging vascular lesions in the brain for clinicians. It was reported that 1%-6% of the world's population is affected by IAs. Owing to serious complications arising from these lesions, much attention has been paid to better understand their pathophysiology. Non-coding RNAs including short non-coding RNAs and long non-coding RNAs, have critical roles in modulating physiologic and pathological processes. These RNAs are emerging as new fundamental regulators of gene expression, are related with the progression of IA. Non-coding RNAs act via multiple mechanisms and be involved in vascular development, growth and remodeling. Furthermore, these molecules are involved in the regulation of inflammation, a key process in the formation and rupture of IA. Studying non-coding RNAs can yield a hypothetical mechanism for better understanding IA. The present study aims to focus on the role of these non-coding RNAs in the pathogenesis of IA.

Neutrophil Extracellular Traps Promote the Development of Intracranial Aneurysm Rupture

[Figure: see text].

Candidate drugs for preventive treatment of unruptured intracranial aneurysms: A cross-sectional study

Background and purpose

Establishment of drug therapy to prevent rupture of unruptured intracranial aneurysms (IAs) is needed. Previous human and animal studies have gradually clarified candidate drugs for preventive treatment of IA rupture. However, because most of these candidates belong to classes of drugs frequently co-administered to prevent cardiovascular diseases, epidemiological studies evaluating these drugs simultaneously should be performed. Furthermore, because drugs included in the same class may have different effects in terms of disease prevention, drug-by-drug assessments are important for planning intervention trials.

Materials and methods

We performed a cross-sectional study enrolling patients diagnosed with IAs between July 2011 and June 2019 at our institution. Patients were divided into ruptured or unruptured groups. The drugs investigated were selected according to evidence suggested by either human or animal studies. Univariate and multivariate logistic regression analyses were performed to assess the association of drug treatment with rupture status. We also performed drug-by-drug assessments of the association, including dose-response relationships, with rupture status.

Results

In total, 310 patients with ruptured and 887 patients with unruptured IAs were included. Multivariate analysis revealed an inverse association of statins (odds ratio (OR), 0.54; 95% confidence interval (CI) 0.38–0.77), calcium channel blockers (OR, 0.41; 95% CI 0.30–0.58), and angiotensin II receptor blockers (ARBs) (OR, 0.67; 95% CI 0.48–0.93) with ruptured IAs. Moreover, inverse dose-response relationships with rupture status were observed for pitavastatin and rosuvastatin among statins, benidipine, cilnidipine, and amlodipine among calcium channel blockers, and valsartan, azilsartan, candesartan, and olmesartan among ARBs. Only non-aspirin non-steroidal anti-inflammatory drugs were positively associated with ruptured IAs (OR, 3.24; 95% CI 1.71–6.13).

Conclusions

The present analysis suggests that several types of statins, calcium channel blockers, and ARBs are candidate drugs for preventive treatment of unruptured IAs.

Endogenous animal models of intracranial aneurysm development: a review

The pathogenesis and natural history of intracranial aneurysm (IA) remains poorly understood. To this end, animal models with induced cerebral vessel lesions mimicking human aneurysms have provided the ability to greatly expand our understanding. In this review, we comprehensively searched the published literature to identify studies that endogenously induced IA formation in animals. Studies that constructed aneurysms (i.e., by surgically creating a sac) were excluded. From the eligible studies, we reported information including the animal species, method for aneurysm induction, aneurysm definitions, evaluation methods, aneurysm characteristics, formation rate, rupture rate, and time course. Between 1960 and 2019, 174 articles reported endogenous animal models of IA. The majority used flow modification, hypertension, and vessel wall weakening (i.e., elastase treatment) to induce IAs, primarily in rats and mice. Most studies utilized subjective or qualitative descriptions to define experimental aneurysms and histology to study them. In general, experimental IAs resembled the pathobiology of the human disease in terms of internal elastic lamina loss, medial layer degradation, and inflammatory cell infiltration. After the early 2000s, many endogenous animal models of IA began to incorporate state-of-the-art technology, such as gene expression profiling and 9.4-T magnetic resonance imaging (MRI) in vivo imaging, to quantitatively analyze the biological mechanisms of IA. Future studies aimed at longitudinally assessing IA pathobiology in models that incorporate aneurysm growth will likely have the largest impact on our understanding of the disease. We believe this will be aided by high-resolution, small animal, survival imaging, in situ live-cell imaging, and next-generation omics technology.

Rupture Risk Assessment for Cerebral Aneurysm Using Interpretable Machine Learning on Multidimensional Data

Background: Assessment of cerebral aneurysm rupture risk is an important task, but it remains challenging. Recent works applying machine learning to rupture risk evaluation presented positive results. Yet they were based on limited aspects of data, and lack of interpretability may limit their use in clinical setting. We aimed to develop interpretable machine learning models on multidimensional data for aneurysm rupture risk assessment. Methods: Three hundred seventy-four aneurysms were included in the study. Demographic, medical history, lifestyle behaviors, lipid profile, and morphologies were collected for each patient. Prediction models were derived using machine learning methods (support vector machine, artificial neural network, and XGBoost) and conventional logistic regression. The derived models were compared with the PHASES score method. The Shapley Additive Explanations (SHAP) analysis was applied to improve the interpretability of the best machine learning model and reveal the reasoning behind the predictions made by the model. Results: The best machine learning model (XGBoost) achieved an area under the receiver operating characteristic curve of 0.882 [95% confidence interval (CI) = 0.838-0.927], significantly better than the logistic regression model (0.779; 95% CI = 0.729-0.829; P = 0.002) and the PHASES score method (0.758; 95% CI = 0.713-0.800; P = 0.001). Location, size ratio, and triglyceride level were the three most important features in predicting rupture. Two typical cases were analyzed to demonstrate the interpretability of the model. Conclusions: This study demonstrated the potential of using machine learning for aneurysm rupture risk assessment. Machine learning models performed better than conventional statistical model and the PHASES score method. The SHAP analysis can improve the interpretability of machine learning models and facilitate their use in a clinical setting.

Aneurysmal subarachnoid hemorrhage during pregnancy: a comprehensive and systematic review of the literature

Aneurysmal subarachnoid hemorrhage (aSAH) is an emergent condition requiring rapid intervention and prolonged monitoring. There are few recommendations regarding the management of aSAH in pregnancy. We identified all available literature and compiled management decisions as well as reported outcomes through a systematic literature review without meta-analysis to provide recommendations for management of aSAH during pregnancy. We included a total of 23 articles containing 54 cases of pregnancy-related aSAH in our review. From these reports and other literature, we evaluated information on aSAH pathophysiology, diagnosis, and management with respect to pregnancy. Early transfer to an appropriate facility with neurocritical care, a high-risk obstetric service, and a neurosurgery team available is crucial for the management of aSAH in pregnancy. Intensive monitoring and a multidisciplinary approach remain fundamental to ensure maternal and fetal health.

A preliminary investigation of radiomics differences between ruptured and unruptured intracranial aneurysms

OBJECTIVES

Prediction of intracranial aneurysm rupture is important in the management of unruptured aneurysms. The application of radiomics in predicting aneurysm rupture remained largely unexplored. This study aims to evaluate the radiomics differences between ruptured and unruptured aneurysms and explore its potential use in predicting aneurysm rupture.

METHODS

One hundred twenty-two aneurysms were included in the study (93 unruptured). Morphological and radiomics features were extracted for each case. Statistical analysis was performed to identify significant features which were incorporated into prediction models constructed with a machine learning algorithm. To investigate the usefulness of radiomics features, three models were constructed and compared. The baseline model A was constructed with morphological features, while model B was constructed with addition of radiomics shape features and model C with more radiomics features. Multivariate analysis was performed for the ten most important variables in model C to identify independent risk factors. A simplified model based on independent risk factors was constructed for clinical use.

RESULTS

Five morphological features and 89 radiomics features were significantly associated with rupture. Model A, model B, and model C achieved the area under the receiver operating characteristic curve of 0.767, 0.807, and 0.879, respectively. Model C was significantly better than model A and model B (p < 0.001). Multivariate analysis identified two radiomics features which were used to construct the simplified model showing an AUROC of 0.876.

CONCLUSIONS

Radiomics signatures were different between ruptured and unruptured aneurysms. The use of radiomics features, especially texture features, may significantly improve rupture prediction performance.

KEY POINTS

• Significant radiomics differences exist between ruptured and unruptured intracranial aneurysms. • Radiomics shape features can significantly improve rupture prediction performance over conventional morphology-based prediction model. The inclusion of histogram and texture radiomics features can further improve the performance. • A simplified model with two variables achieved a similar level of performance as the more complex ones. Our prediction model can serve as a promising tool for the risk management of intracranial aneurysms.

Sphenopalatine ganglion block: Intranasal transmucosal approach for anterior scalp blockade - A prospective randomized comparative study

Background and Aims:

Peripheral nerve blocks in neurosurgical practice attenuate most stressful responses like pin insertion, skin, and dural incision. Scalp block is conventionally the blockade of choice. Further studies for less invasive techniques are required. Intranasal transmucosal block of the sphenopalatine ganglion has shown promising results in patients with chronic headache and facial pain. The primary objective of our study was to compare the gold standard scalp block and bilateral sphenopalatine ganglion block (nasal approach) for attenuation of hemodynamic response to pin insertion. Secondary objectives included hemodynamic response to skin and dural incision.

Material and Methods:

After IRB approval and informed consent, a prospective randomized comparative study was carried out on 50 adult patients undergoing elective supratentorial surgery. The hemodynamic response to pin insertion, skin incision, and dural incision was noted in both the groups. The data was analyzed with NCSS version 9.0 statistical software.

Results:

The HR and MAP were comparable between the groups. Following dural incision MAP was significantly lower at 1,2,3,4,5 and 10 min in group SPG whereas in group S it was significantly lower at 1 and 2min. (P = 0.02 at T1, P = 0.03 at T2).

Conclusions:

Concomitant use of bilateral SPG block with general anesthesia is an effective and safe alternative technique to scalp blockade for obtundation of hemodynamic responses due to noxious stimulus during craniotomy surgeries.

Mast Cell Promotes the Development of Intracranial Aneurysm Rupture

BACKGROUND AND PURPOSE

Inflammation has emerged as a key component of the pathophysiology of intracranial aneurysms. Mast cells have been detected in human intracranial aneurysm tissues, and their presence was associated with intramural microhemorrhage and wall degeneration. We hypothesized that mast cells play a critical role in the development of aneurysmal rupture, and that mast cells can be used as a therapeutic target for the prevention of aneurysm rupture.

METHODS

Intracranial aneurysms were induced in adult mice using a combination of induced systemic hypertension and a single injection of elastase into the cerebrospinal fluid. Aneurysm formation and rupture were assessed over 3 weeks. Roles of mast cells were assessed using a mast cell stabilizer (cromolyn), a mast cell activator (C48/80), and mice that are genetically lacking mature mast cells (Kit^W-sh/W-sh mice).

RESULTS

Pharmacological stabilization of mast cells with cromolyn markedly decreased the rupture rate of aneurysms (80% versus 19%, n=10 versus n =16) without affecting the aneurysm formation. The activation of mast cells with C48/80 significantly increased the rupture rate of aneurysms (25% versus 100%, n=4 versus n=5) without affecting the overall rate of aneurysm formation. Furthermore, the genetic deficiency of mast cells significantly prevented aneurysm rupture (80% versus 25%, n=10 versus n=8, wild-type versus Kit^W-sh/W-sh mice).

CONCLUSIONS

These results suggest that mast cells play a key role in promoting aneurysm rupture but not formation. Stabilizers of mast cells may have a potential therapeutic value in preventing intracranial aneurysm rupture in patients.

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.

The Role of Sartans in the Treatment of Stroke and Subarachnoid Hemorrhage: A Narrative Review of Preclinical and Clinical Studies

Background: Delayed cerebral vasospasm (DCVS) due to aneurysmal subarachnoid hemorrhage (aSAH) and its sequela, delayed cerebral ischemia (DCI), are associated with poor functional outcome. Endothelin-1 (ET-1) is known to play a major role in mediating cerebral vasoconstriction. Angiotensin-II-type-1-receptor antagonists such as Sartans may have a beneficial effect after aSAH by reducing DCVS due to crosstalk with the endothelin system. In this review, we discuss the role of Sartans in the treatment of stroke and their potential impact in aSAH. Methods: We conducted a literature research of the MEDLINE PubMed database in accordance with PRISMA criteria on articles published between 1980 to 2019 reviewing: "Sartans AND ischemic stroke". Of 227 studies, 64 preclinical and 19 clinical trials fulfilled the eligibility criteria. Results: There was a positive effect of Sartans on ischemic stroke in both preclinical and clinical settings (attenuating ischemic brain damage, reducing cerebral inflammation and infarct size, increasing cerebral blood flow). In addition, Sartans reduced DCVS after aSAH in animal models by diminishing the effect of ET-1 mediated vasoconstriction (including cerebral inflammation and cerebral epileptogenic activity reduction, cerebral blood flow autoregulation restoration as well as pressure-dependent cerebral vasoconstriction). Conclusion: Thus, Sartans might play a key role in the treatment of patients with aSAH.

Neurosurgery and Manned Spaceflight

There has been a renewed interest in manned spaceflight due to endeavors by private and government agencies. Publicized goals include manned trips to or colonization of Mars. These missions will likely be of long duration, exceeding existing records for human exposure to extra-terrestrial conditions. Participants will be exposed to microgravity, temperature extremes, and radiation, all of which may adversely affect their physiology. Moreover, pathological mechanisms may differ from those of a terrestrial nature. Known central nervous system (CNS) changes occurring in space include rises in intracranial pressure and spinal unloading. Intracranial pressure increases are thought to occur due to cephalad re-distribution of body fluids secondary to microgravity exposure. Spinal unloading in microgravity results in potential degenerative changes to the bony vertebrae, intervertebral discs, and supportive musculature. These phenomena are poorly understood. Trauma is of highest concern due to its potential to seriously incapacitate crewmembers and compromise missions. Traumatic pathology may also be exacerbated in the setting of altered CNS physiology. Though there are no documented instances of CNS pathologies arising in space, existing diagnostic and treatment capabilities will be limited relative to those on Earth. In instances where neurosurgical intervention is required in space, it is not known whether open or endoscopic approaches are feasible. It is obvious that prevention of trauma and CNS pathology should be emphasized. Further research into neurosurgical pathology, its diagnosis, and treatment in space are required should exploratory or colonization missions be attempted.

Preclinical Intracranial Aneurysm Models: A Systematic Review

Intracranial aneurysms (IA) are characterized by weakened cerebral vessel walls that may lead to rupture and subarachnoid hemorrhage. The mechanisms behind their formation and progression are yet unclear and warrant preclinical studies. This systematic review aims to provide a comprehensive, systematic overview of available animal models for the study of IA pathobiology. We conducted a systematic literature search using the PubMed database to identify preclinical studies employing IA animal models. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies were reviewed and categorized according to the experimental animal and aneurysm model. Of 4266 returned results, 3930 articles were excluded based on the title and/or abstract and further articles after screening the full text, leaving 123 studies for detailed analysis. A total of 20 different models were found in rats (nine), mice (five), rabbits (four), and dogs (two). Rat models constituted the most frequently employed intracranial experimental aneurysm model (79 studies), followed by mice (31 studies), rabbits (12 studies), and two studies in dogs. The most common techniques to induce cerebral aneurysms were surgical ligation of the common carotid artery with subsequent induction of hypertension by ligation of the renal arteries, followed by elastase-induced creation of IAs in combination with corticosterone- or angiotensin-induced hypertension. This review provides a comprehensive summary of the multitude of available IA models to study various aspects of aneurysm formation, growth, and rupture. It will serve as a useful reference for researchers by facilitating the selection of the most appropriate model and technique to answer their scientific question.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental-Clinical Disconnect and the Unmet Need

BACKGROUND

Delayed cerebral ischemia (DCI) is among the most dreaded complications following aneurysmal subarachnoid hemorrhage (SAH). Despite advances in neurocritical care, DCI remains a significant cause of morbidity and mortality, prolonged intensive care unit and hospital stay, and high healthcare costs. Large artery vasospasm has classically been thought to lead to DCI. However, recent failure of clinical trials targeting vasospasm to improve outcomes has underscored the disconnect between large artery vasospasm and DCI. Therefore, interest has shifted onto other potential mechanisms such as microvascular dysfunction and spreading depolarizations. Animal models can be instrumental in dissecting pathophysiology, but clinical relevance can be difficult to establish.

METHODS

Here, we performed a systematic review of the literature on animal models of SAH, focusing specifically on DCI and neurological deficits.

RESULTS

We find that dog, rabbit and rodent models do not consistently lead to DCI, although some degree of delayed vascular dysfunction is common. Primate models reliably recapitulate delayed neurological deficits and ischemic brain injury; however, ethical issues and cost limit their translational utility.

CONCLUSIONS

To facilitate translation, clinically relevant animal models that reproduce the pathophysiology and cardinal features of DCI after SAH are urgently needed.

Iris aneurysm in feline hypertensive oculopathy

OBJECTIVE

To describe and document the prevalence and cause of iris aneurysm in feline hypertensive oculopathy.

ANIMALS STUDIED

Privately owned cats with systemic hypertension presented for sudden visual deficits and/or hyphema.

PROCEDURES

A retrospective search of medical records of cats with systemic hypertension was performed in a specialized eye practice from October 2001 to August 2016. Inclusion criteria used for further evaluation were (1) systolic blood pressure exceeding 170 mm Hg measured by Doppler ultrasound, (2) typical fundus changes consistent with systemic hypertension (retinal folds, retinal edema, intraretinal bullous fluid accumulation, retinal detachment-partial or total, intra-/preretinal bleeding) in at least one eye, and (3) at least one follow-up visit with documented response to therapy with amlodipine. Cats with bilateral hyphema were excluded.

RESULTS

A total of 206 cats fulfilled the inclusion criteria. Twenty-eight cats (14%) showed an aneurysm of the iridal vessels, 21 75% with some amount of hyphema. In total, hyphema was present in 62 cats (30%). Pearson correlation of fundus changes, hyphema, and aneurysm was performed. A high correlation between fundus changes without posterior segment hemorrhage and hyphema was found. The histopathology of one eye showed iridial vascular changes compatible with an aneurysm. In 75 cats, additional blood analysis was performed. Presumed chronic kidney disease (80%) was the most common cause of systemic hypertension with eye disease, followed by hyperthyroidism (20%).

CONCLUSION

Vascular changes of the iris compatible with aneurysms were seen in 14% of cats with systemic hypertension and may result in vascular rupture and acute hyphema.

Noninvasive Vagus Nerve Stimulation Prevents Ruptures and Improves Outcomes in a Model of Intracranial Aneurysm in Mice

Background and Purpose- Inflammation is a critical determinant of aneurysmal wall destabilization, growth, and rupture risk. Targeting inflammation may suppress aneurysm rupture. Vagus nerve stimulation (VNS) has been shown to suppress inflammation both systemically and in the central nervous system. Therefore, we tested the effect of a novel noninvasive transcutaneous VNS approach on aneurysm rupture and outcome in a mouse model of intracranial aneurysm formation with wall inflammation. Methods- Aneurysms were induced by a single stereotaxic injection of elastase into the cerebrospinal fluid at the skull base, combined with systemic deoxycorticosterone-salt hypertension, without or with high-salt diet, for mild or severe outcomes, respectively. Cervical VNS (two 2-minute stimulations 5 minutes apart) was delivered once a day starting from the day after elastase injection for the duration of follow-up. Transcutaneous stimulation of the femoral nerve (FNS) served as control. Multiple aneurysms developed in the circle of Willis and its major branches, resulting in spontaneous ruptures and subarachnoid hemorrhage, neurological deficits, and mortality. Results- In the milder model, VNS significantly reduced aneurysm rupture rate compared with FNS (29% versus 80%, respectively). Subarachnoid hemorrhage grades were also lower in the VNS group. In the more severe model, both VNS and FNS arms developed very high rupture rates (77% and 85%, respectively). However, VNS significantly improved the survival rate compared with FNS after rupture (median survival 13 versus 6 days, respectively), without diminishing the subarachnoid hemorrhage grades. Chronic daily VNS reduced MMP-9 (matrix metalloproteinase-9) expression compared with FNS, providing a potential mechanism of action. As an important control, chronic daily VNS did not alter systemic arterial blood pressure compared with FNS. Conclusions- VNS can reduce aneurysm rupture rates and improve the outcome from ruptured aneurysms.

TLR4 (Toll-Like Receptor 4) Mediates the Development of Intracranial Aneurysm Rupture

Inflammation is emerging as a critical factor in the pathophysiology of intracranial aneurysm. TLR4 (toll-like receptor 4) contributes not only to the innate immune responses but also to the inflammatory processes associated with vascular disease. Therefore, we examined the contribution of the TLR4 pathway to the development of the rupture of intracranial aneurysm. We used a mouse model of intracranial aneurysm. TLR4 inhibition significantly reduced the development of aneurysmal rupture. In addition, the rupture rate and levels of proinflammatory cytokines were lower in TLR4 knockout mice than the control littermates. Macrophage/monocyte-specific TLR4 knockout mice had a lower rupture rate than the control littermate mice. Moreover, the deficiency of MyD88 (myeloid differentiation primary-response protein 88), a key mediator of TLR4, reduced the rupture rate. These findings suggest that the TLR4 pathway promotes the development of intracranial aneurysmal rupture by accelerating inflammation in aneurysmal walls. Inhibition of the TLR4 pathway in inflammatory cells may be a promising approach for the prevention of aneurysmal rupture and subsequent subarachnoid hemorrhage.

The Relationship Between Obstructive Sleep Apnea and Ruptured Intracranial Aneurysms

STUDY OBJECTIVES

The role of obstructive sleep apnea (OSA) in the overall outcome of ruptured intracranial aneurysms (RIAs) is unknown. We have investigated the role of OSA in overall outcome of RIAs.

METHODS

Data from 159 consecutive patients were retrospectively reviewed. A chi-square test and regression analysis were performed to determine the significant difference. A value of P < .05 was considered significant.

RESULTS

The prevalence of OSA in RIAs was fivefold higher in the nonaneurysm patient group, P = .002. The number of patients with hypertension (P < .0001), body mass index ≥ 30 (P < .0001), hyperlipidemia (P = .018), chronic heart disease (P = .002) or prior ischemic stroke (P = .001) was significantly higher in the OSA group. Similarly, the number of wide-neck aneurysms (P < .0001) and aneurysm > 7 mm (P = .004), poor Hunt and Hess grade IV-V (P = .005), vasospasms, (P = .03), and patients with poor Modified Rankin Scale scores (3-6) was significantly higher in the OSA group (P < .0001). Interestingly, for the first time in univariate (P = .01) and multivariate (P = .003) regression analysis, OSA was identified as an individual predictor of unfavorable outcome of RIAs. In addition, hypertension (P = .04), smoking (P = .049), chronic heart disease (P = .01), and Hunt and Hess grade IV-V (P = .04) were revealed as predictors of poor outcome of RIAs.

CONCLUSIONS

This is a novel study to determine the association between OSA and ruptured cerebral aneurysm in terms of comorbidities, size of aneurysm, severity of symptoms, and outcomes after treatment. In addition, for the first time, OSA is identified as a positive predictor of unfavorable outcome of RIAs.

Animal Models of Hypertension: A Scientific Statement From the American Heart Association

Hypertension is the most common chronic disease in the world, yet the precise cause of elevated blood pressure often cannot be determined. Animal models have been useful for unraveling the pathogenesis of hypertension and for testing novel therapeutic strategies. The utility of animal models for improving the understanding of the pathogenesis, prevention, and treatment of hypertension and its comorbidities depends on their validity for representing human forms of hypertension, including responses to therapy, and on the quality of studies in those models (such as reproducibility and experimental design). Important unmet needs in this field include the development of models that mimic the discrete hypertensive syndromes that now populate the clinic, resolution of ongoing controversies in the pathogenesis of hypertension, and the development of new avenues for preventing and treating hypertension and its complications. Animal models may indeed be useful for addressing these unmet needs.

Characteristics of Unruptured Compared to Ruptured Intracranial Aneurysms: A Multicenter Case-Control Study

BACKGROUND

Only a minority of intracranial aneurysms rupture to cause subarachnoid hemorrhage.

OBJECTIVE

To test the hypothesis that unruptured aneurysms have different characteristics and risk factor profiles compared to ruptured aneurysms.

METHODS

We recruited patients with unruptured aneurysms or aneurysmal subarachnoid hemorrhages at 22 UK hospitals between 2011 and 2014. Demographic, clinical, and imaging data were collected using standardized case report forms. We compared risk factors using multivariable logistic regression.

RESULTS

A total of 2334 patients (1729 with aneurysmal subarachnoid hemorrhage, 605 with unruptured aneurysms) were included (mean age 54.22 yr). In multivariable analyses, the following variables were independently associated with rupture status: black ethnicity (odds ratio [OR] 2.42; 95% confidence interval [CI] 1.29-4.56, compared to white) and aneurysm location (anterior cerebral artery/anterior communicating artery [OR 3.21; 95% CI 2.34-4.40], posterior communicating artery [OR 3.92; 95% CI 2.67-5.74], or posterior circulation [OR 3.12; 95% CI 2.08-4.70], compared to middle cerebral artery). The following variables were inversely associated with rupture status: antihypertensive medication (OR 0.65; 95% CI 0.49-0.84), hypercholesterolemia (0.64 OR; 95% CI 0.48-0.85), aspirin use (OR 0.28; 95% CI 0.20-0.40), internal carotid artery location (OR 0.53; 95% CI 0.38-0.75), and aneurysm size (per mm increase; OR 0.76; 95% CI 0.69-0.84).

CONCLUSION

We show substantial differences in patient and aneurysm characteristics between ruptured and unruptured aneurysms. These findings support the hypothesis that different pathological mechanisms are involved in the formation of ruptured aneurysms and incidentally detected unruptured aneurysms. The potential protective effect of aspirin might justify randomized prevention trials in patients with unruptured aneurysms.

Does Systemic Hypertension Impact Recanalization of Coiled Aneurysms?

PURPOSE

It is well known that hypertension is a significant factor in the formation, growth, and rupture of aneurysms and recanalization of coiled aneurysms is affected by hemodynamic stress. At present, however, the impact of hypertension on recanalization of coiled aneurysms has not been adequately investigated. This study examined the relation between hypertension and subsequent outcomes of coiled aneurysms, using a matched patient analysis.

METHODS

A total of 715 subjects undergoing coil embolization of intracranial aneurysms between 2011 and 2013 were selected for study. Time-of-flight magnetic resonance or conventional angiography was used (singly or together) to gauge degrees of occlusion after coiling, applying the Raymond classification in grading recanalization. Patients with hypertension were grouped as controlled or uncontrolled, based on blood pressure readings at outpatient clinics. Hypertensive and non-hypertensive subjects were matched (1:1) for several relevant variables.

RESULTS

Overall, 484 patients (67.7%) were hypertensive (controlled 338; uncontrolled 146). During the follow-up period (28.6 ± 9.7 months), 129 aneurysms (18.0%) displayed recanalization (minor 58; major 71). Patient age, concomitant diabetes, hyperlipidemia, aneurysm size, neck size, depth-to-neck ratio, and aneurysm type differed significantly in hypertensive and non-hypertensive groups; however, group incidences of cumulative recanalization were similar (p = 0.297). After 1:1 matching the cumulative recanalization rate (13.5%) in hypertensive and non-hypertensive counterparts (14.3%) again proved similar (p = 0.578). In the hypertensive group, in addition, recanalization showed no relation to controlled and uncontrolled subgroup (odds ratio, OR = 1.000, p > 0.999).

CONCLUSION

Unlike other aspects of evolving aneurysms (e.g. formation, growth, or rupture), recanalization of coiled aneurysms seems to be unaffected by systemic hypertension.

Aneurysmal Subarachnoid Hemorrhage Associated with Small Aneurysms in Smokers and Women: A Retrospective Analysis

Background

Previous studies have shown low rupture rates for small aneurysms (<10 mm), suggesting that the risk of treatment could exceed the benefits. However, evidence has changed, showing crescent rates of aneurysmal subarachnoid hemorrhage (aSAH) associated with small aneurysms. We report trends in size, localization, clinical characteristics, and outcomes of intracranial aneurysms (IAs).

Methods

In this retrospective study, a total of 200 clinical histories of patients diagnosed with IAs over an 8-year period were analyzed. Variables considered included age, sex, tobacco consumption, morphological characteristics of the aneurysm, complications, vasospasm, and mortality. Qualitative variables were assessed by measurements of absolute and relative frequency. Smoking behavior, aneurysm size, and aneurysm rupture (AR) were compared using 1-way analysis of variance. Categorical variables were analyzed using Pearson's χ² test.

Results

The average age at presentation was 58 years. The average size of ruptured aneurysms in the general group was 2.5–7.5 mm, and AR was most common in women (76%) and in patients age 50–60 years (33%). The rate of vasospasm was 19%, and mortality was 37%. Smokers composed 32% of the cohort. Heavy smokers had a 57% rate of aSAH, with an average size of rupture of 5 mm. The most common location of aneurysms and AR was the AComA (33%).

Conclusions

Our results suggest increasing AR rates in aneurysms smaller than 10 mm. This trend is seen especially in individuals with heavy tobacco consumption and in women of perimenopausal age. Our findings show a tendency of AR in accordance with previous results and are expected to serve as basis for further research on aneurysm management.

A Re-Engineered Software Interface and Workflow for the Open-Source SimVascular Cardiovascular Modeling Package

Patient-specific simulation plays an important role in cardiovascular disease research, diagnosis, surgical planning and medical device design, as well as education in cardiovascular biomechanics. simvascular is an open-source software package encompassing an entire cardiovascular modeling and simulation pipeline from image segmentation, three-dimensional (3D) solid modeling, and mesh generation, to patient-specific simulation and analysis. SimVascular is widely used for cardiovascular basic science and clinical research as well as education, following increased adoption by users and development of a GATEWAY web portal to facilitate educational access. Initial efforts of the project focused on replacing commercial packages with open-source alternatives and adding increased functionality for multiscale modeling, fluid-structure interaction (FSI), and solid modeling operations. In this paper, we introduce a major SimVascular (SV) release that includes a new graphical user interface (GUI) designed to improve user experience. Additional improvements include enhanced data/project management, interactive tools to facilitate user interaction, new boundary condition (BC) functionality, plug-in mechanism to increase modularity, a new 3D segmentation tool, and new computer-aided design (CAD)-based solid modeling capabilities. Here, we focus on major changes to the software platform and outline features added in this new release. We also briefly describe our recent experiences using SimVascular in the classroom for bioengineering education.

Prediction of Aneurysm Stability Using a Machine Learning Model Based on PyRadiomics-Derived Morphological Features

Background and Purpose- Discrimination of the stability of intracranial aneurysms is critical for determining the treatment strategy, especially in small aneurysms. This study aims to evaluate the feasibility of applying machine learning for predicting aneurysm stability with radiomics-derived morphological features. Methods- Morphological features of 719 aneurysms were extracted from PyRadiomics, of which 420 aneurysms with Maximum3DDiameter ranging from 4 mm to 8 mm were enrolled for analysis. The stability of these aneurysms and other clinical characteristics were reviewed from the medical records. Based on the morphologies with/without clinical features, machine learning models were constructed and compared to define the morphological determinants and screen the optimal model for predicting aneurysm stability. The effect of clinical characteristics on the morphology of unstable aneurysms was analyzed. Results- Twelve morphological features were automatically extracted from PyRadiomics implemented in Python for each aneurysm. Lasso regression defined Flatness as the most important morphological feature to predict aneurysm stability, followed by SphericalDisproportion, Maximum2DDiameterSlice, and SurfaceArea. SurfaceArea (odds ratio [OR], 0.697; 95% CI, 0.476-0.998), SphericalDisproportion (OR, 1.730; 95% CI, 1.143-2.658), Flatness (OR, 0.584; 95% CI, 0.374-0.894), Hyperlipemia (OR, 2.410; 95% CI, 1.029-5.721), Multiplicity (OR, 0.182; 95% CI, 0.082-0.380), Location at middle cerebral artery (OR, 0.359; 95% CI, 0.134-0.902), and internal carotid artery (OR, 0.087; 95% CI, 0.030-0.211) were enrolled into the final prediction model. In terms of performance, the area under curve of the model reached 0.853 (95% CI, 0.767-0.940). For unstable aneurysms, Compactness1 (P=0.035), Compactness2 (P=0.036), Sphericity (P=0.035), and Flatness (P=0.010) were low, whereas SphericalDisproportion (P=0.034) was higher in patients with hypertension. Conclusions- Morphological features extracted from PyRadiomics can be used for aneurysm stratification. Flatness is the most important morphological determinant to predict aneurysm stability. Our model can be used to predict aneurysm stability. Unstable aneurysm is more irregular in patients with hypertension.

In vivo cerebral aneurysm models

Cerebral aneurysm rupture is a devastating event resulting in subarachnoid hemorrhage and is associated with significant morbidity and death. Up to 50% of individuals do not survive aneurysm rupture, with the majority of survivors suffering some degree of neurological deficit. Therefore, prior to aneurysm rupture, a large number of diagnosed patients are treated either microsurgically via clipping or endovascularly to prevent aneurysm filling. With the advancement of endovascular surgical techniques and devices, endovascular treatment of cerebral aneurysms is becoming the first-line therapy at many hospitals. Despite this fact, a large number of endovascularly treated patients will have aneurysm recanalization and progression and will require retreatment. The lack of approved pharmacological interventions for cerebral aneurysms and the need for retreatment have led to a growing interest in understanding the molecular, cellular, and physiological determinants of cerebral aneurysm pathogenesis, maturation, and rupture. To this end, the use of animal cerebral aneurysm models has contributed significantly to our current understanding of cerebral aneurysm biology and to the development of and training in endovascular devices. This review summarizes the small and large animal models of cerebral aneurysm that are being used to explore the pathophysiology of cerebral aneurysms, as well as the development of novel endovascular devices for aneurysm treatment.

Intracranial Aneurysm as a Macrophage-mediated Inflammatory Disease

Subarachnoid hemorrhage (SAH) is mainly attributable to the rupture of intracranial aneurysms (IAs). Although the outcome of SAH is considerably poor in spite of the recent intensive medical care, mechanisms regulating the progression of IAs or triggering rupture remain to be clarified, making the development of effective preemptive medicine to prevent SAH difficult. However, a series of recent studies have been expanding our understanding of the pathogenesis of IAs. These studies have suggested the crucial role of macrophage-mediated chronic inflammation in the pathogenesis of IAs. In histopathological analyses of IA lesions in humans and induced in animal models, the number of macrophages infiltrating in lesions is positively correlated with enlargement or rupture of IAs. In animal models, a genetic deletion or an inhibition of monocyte chemotactic protein-1, a major chemoattractant for macrophages, or a pharmacological depletion of macrophages consistently suppresses the development and progression of IAs. Furthermore, a macrophage-specific deletion of Ptger2 (gene for prostaglandin E receptor subtype 2) or a macrophage-specific expression of a mutated form of IκBα which inhibits nuclear translocation of nuclear factor κB significantly suppress the development of IAs, supporting the role of macrophages and the inflammatory signaling functioning there in the pathogenesis of IAs. The development of drug therapies suppressing macrophage-mediated inflammatory responses in situ can thus be a potential strategy in the pre-emptive medicine targeting SAH. In this manuscript, we summarize the experimental evidences about the pathogenesis of IAs focused on inflammatory responses and propose the definition of IAs as a macrophage-mediated inflammatory disease.

Small ruptured intracranial aneurysms: the risk of massive bleeding and rebleeding

OBJECTIVE

The risk of hemorrhagic events in small ruptured aneurysms remains unclear. Due to less arterial wall, small ruptured aneurysms may be correlated with massive bleeding and rebleeding. Therefore, it may contribute to treatment to evaluate the amount of bleeding and the risk of rebleeding in small ruptured aneurysms.

METHODS

A retrospective cohort study of all consecutive patients with intracranial aneurysms admitted to our hospital from February 2013 to December 2017 was carried out. Ruptured aneurysms were divided into small ruptured aneurysm (0-5 mm) group and large ruptured aneurysm (5 mm) group for analysis. The difference of bleeding volume, rebleeding and clinical outcome were analyzed between the two groups.

RESULTS

A total of 738 patients with aneurysmal subarachnoid hemorrhage (SAH) were included in this study and small ruptured aneurysms accounted for 49.2% of all ruptured aneurysms. Univariate analysis showed that the amount of bleeding (14.5 ± 7.1 vs. 14.4 ± 7.3; P = 0.867), rebleeding (8.3% vs. 10.9%; P = 0.261) and poor outcome (29.6% vs. 23.1%; P = 0.055) were similar between the two groups. Multivariable analysis showed that hypertension was obviously associated with the amount of bleeding (adjusted odds ratio (aOR), 3.25 [1.81-4.69]; P < 0.001) and rebleeding (aOR, 3.31 [1.10-9.99]; P = 0.034) in small ruptured aneurysms, and its effect on rebleeding of small ruptured aneurysms is greater than that of large ruptured aneurysms.

CONCLUSIONS

The risk of hemorrhagic events in small ruptured aneurysms is similar to that in large ruptured aneurysms, especially those patients with small ruptured aneurysms that complicated with hypertension are at an increased risk of massive SAH and rebleeding.

Effect of premorbid hypertension control on outcome of patients with aneurysmal subarachnoid hemorrhage

OBJECTIVE

Hypertension is common in patients with aneurysmal subarachnoid hemorrhage (SAH). However, it is still unclear whether premorbid antihypertensive therapy can help to reduce the risk of severe aneurysmal bleeding. Therefore, this study aims to assess the effect of premorbid hypertension control on outcome of patients with aneurysmal SAH.

METHODS

We retrospectively reviewed the clinical data of patients with intracranial aneurysms admitted to our institution from February 2012 to December 2017. Based on premorbid hypertension history and use of antihypertensive agents, all patients with aneurysmal SAH were divided into antihypertensive group and uncontrolled group. Patient characteristics, imaging features, clinical complication, and outcome were analyzed between the two groups.

RESULTS

A total of 348 patients with ruptured aneurysms were included in this study. Compared to those with premorbid controlled hypertension, patients with premorbid uncontrolled hypertension presented worse clinical grade, with more severe aneurysmal SAH and more frequent intracerebral hematoma. Patients receiving a treatment for ACEI type or ARB type of drugs in the antihypertensive group suffered from less amount of aneurysmal bleeding, while patients with grade 3 hypertension in the uncontrolled group suffered from more amount of aneurysmal bleeding. Patients with premorbid controlled hypertension had a lower incidence of rebleeding, hydrocephalus, and cerebral vasospasm, and had a lower rate of disability and mortality.

CONCLUSIONS

Premorbid hypertension control is associated with favorable clinical outcome of patients with aneurysmal SAH. Besides, the ACEI type or ARB type of antihypertensive agents is associated with the less amount of bleeding after aneurysm rupture.

Comparison of Supraorbital and Pterional Keyhole Approach for Clipping Middle Cerebral Artery Aneurysm: A Chinese Population-Based Study

OBJECTIVE

Keyhole craniotomy is a minimally invasive approach for the treatment of middle cerebral artery (MCA) aneurysms. The aim of this study was to compare the clinical outcome between supraorbital keyhole approach and pterional keyhole approach (PKA) in Chinese patients with MCA aneurysm.

METHODS

Consecutive patients with MCA aneurysms were reviewed between January 2013 and December 2017. Efficacy and safety between PKA and supraorbital keyhole approach were compared. Poor outcome was defined as modified Rankin Scale score of 3-6 at discharge.

RESULTS

This study enrolled 260 patients; 222 (85.4%) had ruptured aneurysm, and 183 (70.4%) received PKA. The distribution of PKA in unruptured and ruptured aneurysms showed no significant difference (P > 0.05). In subgroup analyses, PKA was more likely associated with poor outcome at discharge in patients with unruptured aneurysms (odds ratio = 5.500, 95% confidence interval = 1.013-29.850, P = 0.048), whereas approach selection was not an independent factor predicting poor outcome in patients with ruptured aneurysms (P > 0.05).

CONCLUSIONS

In a Chinese population, supraorbital keyhole approach was superior to PKA in improving outcome in patients with unruptured MCA aneurysms, but the 2 approaches showed comparable outcomes at discharge in patients with ruptured aneurysms.

Protective Effect of Mesenchymal Stem Cells Against the Development of Intracranial Aneurysm Rupture in Mice

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem or stromal cells found in multiple tissues. Intravenous MSC injections have been used to treat various diseases with an inflammatory component in animals and humans. Inflammation is emerging as a key component of pathophysiology of intracranial aneurysms. Modulation of inflammation by MSCs may affect sustained inflammatory processes that lead to aneurysmal rupture.

OBJECTIVE

To assess the effect of MSCs on the development of aneurysm rupture using a mouse model.

METHODS

Intracranial aneurysms were induced with a combination of a single elastase injection into the cerebrospinal fluid and deoxycorticosterone acetate salt-induced hypertension in mice. We administered allogeneic bone marrow-derived MSCs or vehicle, 6 and 9 d after aneurysm induction.

RESULTS

MSC administration significantly reduced rupture rate (vehicle control vs MSCs, 90% vs 36%; P < .05). In cell culture experiments with an MSC and mast cell coculture, MSCs stabilized mast cells through cyclooxygenase-2 (COX-2)-dependent production of prostaglandin E2, thereby reducing the release of proinflammatory cytokines from mast cells. Pretreatment of MSCs with COX-2 inhibitor, NS-398, abolished the protective effect of MSCs against the development of aneurysm rupture.

CONCLUSION

Intravenous administration of MSCs after aneurysm formation prevented aneurysmal rupture in mice. The protective effect of MSCs against the development of aneurysm rupture appears to be mediated in part by the stabilization of mast cells by MSCs.

Morphological parameters and anatomical locations associated with rupture status of small intracranial aneurysms

Characterization of the rupture risk factors for small intracranial aneurysms (SIAs, ≤5 mm) is clinically valuable. The present study aims to identify image-based morphological parameters and anatomical locations associated with the rupture status of SIAs. Two hundred and sixty-three patients with single SIAs (128 ruptured, 135 unruptured) were included, and six morphological parameters, including size, aspect ratio (AR), size ratio (SR), height–width ratio (H/W), flow angle (FA) and aneurysm width–parent artery diameter ratio, and the aneurysm locations were evaluated using three-dimensional geometry, and were used to identify a correlation with aneurysm rupture. Statistically significant differences were observed between ruptured and unruptured groups for AR, SR, H/W, FA, and aneurysm locations, from univariate analyses. Logistic regression analysis further revealed that AR (p = 0.034), SR (p = 0.004), H/W (p = 0.003), and FA (p < 0.001) had the strongest independent correlation with ruptured SIAs after adjustment for age, gender and other clinical risk factors. A future study on a larger SIA cohort need to establish to what extent the AR, SR, H/W and FA increase the risk of rupture in patients with unruptured SIAs in terms of absolute risks.

Intracranial Arterial Fenestration and Risk of Aneurysm: A Systematic Review and Meta-Analysis

BACKGROUND

Previous studies have been inconsistent regarding risk for intracranial aneurysm related to intracranial arterial fenestration. We conducted a meta-analysis to examine the association between intracranial arterial fenestration and risk of aneurysm.

METHODS

We performed a systematic review of PubMed and Embase through August 2017 for potentially relevant articles. Summary odds ratios with 95% confidence intervals were pooled using a random-effects model.

RESULTS

Of 446 articles found, 7 were selected for meta-analysis. Pooled odds ratios revealed an increased risk of aneurysm owing to fenestration of 1.50 (95% confidence interval, 0.61-3.71; P = 0.38). Subgroup analyses based on the population presenting with various indications suggested that pooled odds ratios indicated a significant increase in risk for aneurysm of 2.43 (95% confidence interval, 1.04-5.69; P = 0.04).

CONCLUSIONS

Our findings indicate that intracranial arterial fenestration may be associated with increased risk for aneurysm formation.

A Comparison of Pathophysiology in Humans and Rodent Models of Subarachnoid Hemorrhage

Non-traumatic subarachnoid hemorrhage (SAH) affects an estimated 30,000 people each year in the United States, with an overall mortality of ~30%. Most cases of SAH result from a ruptured intracranial aneurysm, require long hospital stays, and result in significant disability and high fatality. Early brain injury (EBI) and delayed cerebral vasospasm (CV) have been implicated as leading causes of morbidity and mortality in these patients, necessitating intense focus on developing preclinical animal models that replicate clinical SAH complete with delayed CV. Despite the variety of animal models currently available, translation of findings from rodent models to clinical trials has proven especially difficult. While the explanation for this lack of translation is unclear, possibilities include the lack of standardized practices and poor replication of human pathophysiology, such as delayed cerebral vasospasm and ischemia, in rodent models of SAH. In this review, we summarize the different approaches to simulating SAH in rodents, in particular elucidating the key pathophysiology of the various methods and models. Ultimately, we suggest the development of standardized model of rodent SAH that better replicates human pathophysiology for moving forward with translational research.

DOCA-Salt Hypertension: an Update

Hypertension is a multifaceted disease that is involved in ∼40% of cardiovascular mortalities and is the result of both genetic and environmental factors. Because of its complexity, hypertension has been studied by using various models and approaches, each of which tends to focus on individual organs or tissues to isolate the most critical and treatable causes of hypertension and the related damage to end-organs. Animal models of hypertension have ranged from Goldblatt's kidney clip models in which the origin of the disease is clearly renal to animals that spontaneously develop hypertension either through targeted genetic manipulations, such as the TGR(mRen2)27, or selective breeding resulting in more enigmatic origins, as exemplified by the spontaneously hypertensive rat (SHR). These two genetically derived models simulate the less-common human primary hypertension in which research has been able to define a Mendelian linkage. Several models are more neurogenic or endocrine in nature and illustrate that crosstalk between the nervous system and hormones can cause a significant rise in blood pressure (BP). This review will examine one of these neurogenic models of hypertension, i.e., the deoxycorticosterone acetate (DOCA), reduced renal mass, and high-salt diet (DOCA-salt) rodent model, one of the most common experimental models used today. Although the DOCA-salt model is mainly believed to be neurogenic and has been shown to impact the central and peripheral nervous systems, it also significantly involves many other body organs.

Management of Unruptured Intracranial Aneurysms

Unruptured intracranial aneurysms (UIA) occur in approximately 2-3 % of the population. Most of these lesions are incidentally found, asymptomatic and typically carry a benign course. Although the risk of aneurysmal subarachnoid hemorrhage is low, this complication can result in significant morbidity and mortality, making assessment of this risk the cornerstone of UIA management. This article reviews important factors to consider when managing unruptured intracranial aneurysms including patient demographics, comorbidities, family history, symptom status, and aneurysm characteristics. It also addresses screening, monitoring, medical management and current surgical and endovascular therapies.

The Siesta Habit is Associated with a Decreased Risk of Rupture of Intracranial Aneurysms

BACKGROUND

Previous studies have examined an association between the siesta habit and hypertension, as well as coronary heart disease. However, the relationship between a siesta and the risk of rupture of an intracranial aneurysm (IA) has not yet been established. We aimed to investigate the effects of a siesta on the risk of rupture of IAs.

METHODS

We prospectively enrolled consecutive patients diagnosed with IAs at our hospital between January 2016 and December 2016. Univariate and multivariate logistic regression analysis were performed to identify independent risk factors associated with IA rupture.

RESULTS

We studied 581 consecutive patients with 514 unruptured and 120 ruptured aneurysms. Univariate analysis demonstrated that hypertension, hyperlipidemia, diabetes mellitus, cigarette smoking, location, size, as well as shape and aspect ratio were associated with the risk of rupture of IAs. Multivariate analysis identified hypertension [odds ratio (OR) 1.68, 95% confidence interval (CI) 1.03-2.73], hyperlipidemia (OR 0.25, 95% CI 0.08-0.72), current cigarette smoking ≥20 cigarettes/day (d) (OR 3.48, 95% CI 1.63-7.47), siesta (siesta time <1 h, OR 0.49, 95% CI 0.24-0.98 and siesta time ≥1 h, OR 0.32, 95% CI 0.19-0.57), location of largest aneurysm on the anterior communicating and internal carotid-posterior communicating artery (PCOM) (anterior communicating artery OR 16.27, 95% CI 7.40-35.79 and PCOM OR 11.21, 95% CI 5.15-24.43), and size of aneurysm ≥7 mm (OR 2.19, 95% CI 1.21-3.97) as independent strong risk factors associated with risk of aneurysm rupture.

CONCLUSION

In the present study, we found that a habitual siesta is a new predictive factor to assess the risk of rupture of an IA. We found the siesta habit may reduce the risk of aneurysm rupture. We also found that hypertension, hyperlipidemia, cigarette smoking, location, and size of aneurysm were associated with the risk of rupture of IAs.

WHICH MORPHOLOGIC AND HEMODYNAMIC CHARACTERISTICS PREDICT INTRACRANIAL FUSIFORM ANEURYSMS RUPTURE? A PATIENT-SPECIFIC COMPUTATIONAL FLUID DYNAMICS STUDY

To identify hemodynamic and morphological parameters leading to increased risk of intracranial fusiform aneurysms (IFA) rupture using computational fluid dynamics (CFDs). A total of 24 patient-specific fusiform aneurysms models on vertebral artery were reconstructed from 3D angiography images. 11 ruptured cases and 13 unruptured cases were included. Morphologic parameters were measured and CFD parameters were calculated using CFD simulation. The length of the aneurysm is significantly shorter in ruptured group than in unruptured group. The ratio of the width to the length of an aneurysm (WLR) and the ratio of the cross-section area to the length of an aneurysm (ALR) to the averaged cross sectional areas of the inlet and outlet of the parent artery (ALaR) were significantly higher in ruptured group compared with unruptured group. Wall shear stress (WSS) of the aneurysm was normalized to the WSS of the parent artery. Hemodynamically, only low WSS was associated with higher risk of rupture. Ruptured IFAs are shorter, have bigger WLR, ALaR, and lower WSS, compared with unruptured IFAs.

Treatment of unruptured intracranial aneurysms: a review

INTRODUCTION

Unruptured brain aneurysms (UIAs) present a challenge due to the lack of definitive understanding of their natural history and treatment outcomes. As the treatment of UIAs is aimed at preventing the possibility of rupture, the immediate risk of treatment must be weighed against the risk of rupture in the future. As such, treatment for a large proportion of UIAs is currently individualized.

AREAS COVERED

In this article, we discuss the important natural history studies of UIAs and discuss the existing scientific evidence and recent advances that help identify the rupture risk guide management of UIAs. We also address the recent advances in pharmacological therapy of UIAs. Expert commentary: In the recent years, there have been great advances in understanding the pathophysiology of UIAs and determining the rupture risk going beyond the traditional parameter of aneurysm size. Aneurysm morphology and hemodynamics play a pivotal role in growth and rupture. A true randomized trial for the management of UIAs is the need of the hour.

Diabetes may affect intracranial aneurysm stabilization in older patients: Analysis based on intraoperative findings

BACKGROUND

Only a small proportion of aneurysms progress to rupture. Previous studies have focused on predicting the rupture risk of intracranial aneurysms. Atherosclerotic aneurysm wall appears resistant to rupture. The purpose of this study was to evaluate clinical and morphological factors affecting atherosclerosis of an aneurysm and identify the parameters that predict aneurysm stabilization.

METHODS

We conducted a retrospective analysis of 253 consecutive patients with 291 unruptured aneurysms who underwent clipping surgery in a single institution between January 2012 and October 2013. Aneurysms were categorized based on intraoperative video findings and assessed morphologic and demographic data. Aneurysms which had the atherosclerotic wall without any super thin and transparent portion were defined as stabilized group and the others as a not-stabilized group.

RESULTS

Of the 207 aneurysms, 176 (85.0%) were assigned to the not-stabilized group and 31 (15.0%) to the stabilized group. The relative proportion of stabilized aneurysms increased significantly as the age increased (P < 0.001). Univariate logistic analysis showed that age ≥65 years (P < 0.001), hypertension (P = 0.012), diabetes (P = 0.007), and height ≥3 mm (P = 0.007) were correlated with stabilized aneurysms. Multivariate logistic analysis showed that age ≥65 years (P = 0.009) and hypertension (P = 0.041) were strongly correlated with stable aneurysms. In older patients (≥65 years of age), multivariate logistic regression revealed that only diabetes was associated with stabilized aneurysms (P = 0.027).

CONCLUSIONS

In patients ≥65 years of age, diabetes mellitus may highly predict the stabilized aneurysms. These results provide useful information in determining treatment and follow-up strategies, especially in older patients.