Incidence and risk factors for the growth of unruptured cerebral aneurysms: observation using serial computerized tomography angiography

Cigarette Smoking and Observed Growth of Unruptured Intracranial Aneurysms: A Systematic Literature Review and Meta-Analysis

BACKGROUND

Smoking and observed growth of intracranial aneurysms are known risk factors for rupture. The mechanism by which smoking increases this risk is not completely elucidated. Furthermore, an association between smoking and aneurysm growth has not been clearly defined in the literature. We hypothesize that smoking is associated with aneurysm growth, which, in turn, may serve as one of the mechanisms by which smoking drives rupture risk.

METHODS

We report a systematic review of the literature in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Using the R software, we performed a meta-analysis to investigate the association between smoking and the growth of unruptured intracranial aneurysms. Studies on familial aneurysms and genetic syndromes known to increase the risk of aneurysms were excluded.

RESULTS

Eighteen observational studies were included with a total of 3535 patients and 4289 aneurysms with a mean follow-up period ranging from 17 to 226 months. The mean age among the studies ranged from 38.4 to 73.9 years; 74% of patients were female. Ever-smoking status (odds ratio, 1.10 [95% CI, 0.87-1.38]) and current smoking status (odds ratio, 1.43 [95% CI, 0.84-2.43]) did not show a statistically significant association with growth of intracranial aneurysms. Patients currently smoking did not have a statistically significant association with the growth of intracranial aneurysms (odds ratio, 1.18 [95% CI, 0.72-1.93]) compared with patients without a smoking history. No significant association was found in patients who previously smoked compared with patients who never smoked (odds ratio, 1.46 [95% CI, 0.88-2.43]).

CONCLUSIONS

Smoking is not clearly associated with the growth of unruptured intracranial aneurysms, despite trends being observed, there is no statistical association. The mechanism by which smoking increases rupture risk might not be growth. In patients for whom observation is recommended, the absence of growth over time in the setting of smoking history does not, therefore, imply protection from rupture.

Obstructive Sleep Apnea and Its Influence on Intracranial Aneurysm

Obstructive sleep apnea syndrome (OSAS) is associated with cerebrovascular disease, which can lead to life-threatening outcomes. The purpose of the study was to investigate the relationship between OSAS and comorbid intracranial aneurysms. We retrospectively reviewed 564 patients who underwent a polysomnography and brain magnetic resonance angiography as part of their health checkup. We calculated the prevalence of an intracranial aneurysm and OSAS in patients and measured the size of the intracranial aneurysm if present. The mean patient age was 55.6 ± 8.5 years, and 82.3% of them were men. The prevalence of an intracranial aneurysm in patients with OSAS was 12.1%, which is significantly higher than patients with non-OSAS (5.9%, p = 0.031). Patients with OSAS had a much higher prevalence of intracranial aneurysms, after adjusting all possible confounding factors such as age, sex, smoking status, alcohol drinking, and body mass index (odds ratio: 2.32; 95% confidence interval: 1.07-5.04). Additionally, the OSAS group had noticeably larger aneurysms compared with those of the non-OSAS group (3.2 ± 2.0 mm vs. 2.0 ± 0.4 mm, p = 0.013). We found a significant association between OSAS and intracranial aneurysms. OSAS could be another risk factor for the development of intracranial aneurysms.

Numerical investigation of unruptured middle cerebral artery bifurcation aneurysms: influence of aspect ratio

An aneurysm is a disease condition, which is due to the pathological weakening of an arterial wall. These aneurysms are often found in various branch points and bifurcations of an artery in the cerebral circulation. Most aneurysms come to medical attention, either due to brain hemorrhages caused by rupture or found unruptured. To consider surgically invasive treatment modalities, clinicians need scientific methods such as, hemodynamic analysis to assess rupture risk. The arterial wall loses its structural integrity when wall shear stress (WSS) and other hemodynamic parameters exceed a certain threshold. In the present study, numerical simulations are carried out for unruptured middle cerebral artery (MCA) aneurysms. Three distinct representative sizes are chosen from a larger patient pool of 26 MCA aneurysms. Logically, these aneurysms represent three growth stages of any patient with similar anatomical structure. Simulations are performed to compare the three growth phases (with different aspect ratios) of an aneurysm and correlate their hemodynamic parameters. Simulations with patient specific boundary conditions reveal that, aneurysms with a higher aspect ratio (AR) correspond to an attendant decrease in both time-averaged wall shear stress (TAWSS) and spatial wall shear stress gradients (WSSG). Smaller MCAs were observed to have higher positive wall shear stress divergence (WSSD), exemplifying the tensile nature of arterial wall stretching. Present study identifies positive wall shear stress divergence (PWSSD) to be a potential biomarker for evaluating the growth of an aneurysm.

Dynamic evaluation of unruptured intracranial aneurysms by 4D-CT angiography: comparison with digital subtraction angiography (DSA) and surgical findings

BACKGROUND

This study was to prospectively investigate the feasibility of four-dimensional computed tomography angiography (4D-CTA) with electrocardiogram-gated (ECG) reconstruction for preoperative evaluation of morphological parameters, and compared with digital subtraction angiography (DSA). We also aimed to detect pulsation in unruptured intracranial aneurysms (UIAs) by using 4D-CTA, as a potential predicting factor of growth or rupture.

MATERIALS

64 patients with 64 UIAs underwent ECG-gated dynamic 4D-CTA imaging before treatment, of which 46 patients additionally underwent DSA. Original scanning data were reconstructed to produce 20 data sets of cardiac cycles with 5%-time intervals. The extent of agreement on UIAs morphological features assessed with 4D-CTA and DSA was estimated using the k coefficient of the Kappa test. The radiation doses were also calculated and compared between 4D-CTA and DSA. In the aneurysmal surgically treated in our institution, we were able to compare the surgical findings of the aneurysm wall with 4D-CTA images. We performed long-term follow-up on untreated patients.

RESULTS

The morphological characteristics detected by 4D-CTA and DSA were consistent in aneurysm location (k = 1.0), shape (k = 0.76), maximum diameter (k = 0.94), aneurysm neck (k = 0.79) and proximity to parent and branch vessels (k = 0.85). 4D-CTA required lower radiation doses (0.32 ± 0.11 mSv) than DSA (0.84 ± 0.37 mSv, P < 0.001). Pulsation was detected in 26 of the 64 unruptured aneurysms, and all underwent neurosurgical clipping or interventional embolization. In aneurysms surgically treated in our hospital, we observed a significant correlation between 4D-CTA findings and surgical evaluation of the aneurysmal wall, in particular the irregular pulsations detected on 4D-CTA have demonstrated to correspond to dark-reddish thinner wall at surgery.

CONCLUSIONS

In this proof-of-concept study, 4D-CTA provided real-time, non-invasive preoperative assessments of UIAs comparable to DSA. Moreover, optimal correlation between the irregular pulsation detected by 4D-CTA and the surgical findings support a possible role of this technique to identify aneurysms with a higher risk of rupture.

Endovascular and Medical Management of Unruptured Intracranial Aneurysms

Unruptured intracranial aneurysms are often discovered incidentally on noninvasive imaging. As use of noninvasive imaging has increased, our understanding of the presumed prevalence of intracranial aneurysms in adults has increased. Incidentally found aneurysms are often asymptomatic; however, they can rarely rupture and cause life-threatening illness. Elective treatment of intracranial aneurysms carries risks which need to be considered along with patient-specific factors (e.g., anatomy, medical comorbidities, personal preferences). In this article, we review the natural history, risk factors for cerebral aneurysm formation and rupture, evidence for medical management, and the safety profile and efficacy of available endovascular treatment options.

Advanced cross-sectional imaging of cerebral aneurysms

While the rupture rate of cerebral aneurysms is only 1% per year, ruptured aneurysms are associated with significant morbidity and mortality, while aneurysm treatments have their own associated risk of morbidity and mortality. Conventional markers for aneurysm rupture include patient-specific and aneurysm-specific characteristics, with the development of scoring systems to better assess rupture risk. These scores, however, rely heavily on aneurysm size, and their accuracy in assessing risk in smaller aneurysms is limited. While the individual risk of rupture of small aneurysms is low, due to their sheer number, the largest proportion of ruptured aneurysms are small aneurysms. Conventional imaging techniques are valuable in characterizing aneurysm morphology; however, advanced imaging techniques assessing the presence of inflammatory changes within the aneurysm wall, hemodynamic characteristics of blood flow within aneurysm sacs, and imaging visualization of irregular aneurysm wall motion have been used to further determine aneurysm instability that otherwise cannot be characterized by conventional imaging techniques. The current manuscript reviews conventional imaging techniques and their value and limitations in cerebral aneurysm characterization, and evaluates the applications, value and limitations of advanced aneurysm imaging and post-processing techniques including intracranial vessel wall MRA, 4D-flow, 4D-CTA, and computational fluid dynamic simulations.

Artificial intelligence aneurysm measurement tool finds growth in all aneurysms that ruptured during conservative management

BACKGROUND

Cerebral aneurysm rupture is associated with high rates of morbidity and mortality. Detecting aneurysms at high risk of rupture is critical in management decision making. Rupture risk has traditionally been associated with size-measured as a maximum dimension. However, aneurysms are morphologically dynamic, a characteristic ignored by large prospective aneurysm risk studies. Manual measurement is challenging and fraught with error. We used an artificial intelligence (AI) measurement tool to study aneurysms that ruptured during conservative management to detect changes in size not appreciated by manual linear measurement.

METHODS

A single practice database with >5000 aneurysms was queried. Patients followed conservatively for an unruptured aneurysm were identified using appropriate diagnosis codes. This cohort was screened for subsequent rupture using procedure codes. Only patients with two vascular imaging studies before rupture were included.

RESULTS

Five patients met the criteria. All patients had aneurysm enlargement, two of which were not detected from manual linear measurements, including adjudication and analysis, during a multidisciplinary neurovascular conference in a high volume practice. Maximum dimension increased at a minimum of 1.8% (range 1.8-63.3%) from the first scan to the last, and aneurysm volume increased at a minimum of 5.9% (5.9-385.5%), highlighting the importance of volumetric measurement.

CONCLUSIONS

AI-enabled volumetric measurements are more sensitive to changes in size and detected enlargement in all aneurysms that ruptured during conservative management. This finding has major implications for clinical practice and methods used for interval aneurysm measurement in patients being conservatively followed.

A Meta-Analysis of Rupture Risk for Intracranial Aneurysms 10 mm or Less in Size Selected for Conservative Management Without Repair

BACKGROUND

Small unruptured intracranial aneurysms (UIAs) are considered to have low risk of rupture. The proportion of UIAs measuring 10 mm or less in size that rupture when selected for conservative management without repair is not well known. The aim of this study is to determine the proportion of UIAs that rupture by size threshold from ≤10 to ≤3 mm when selected for management without repair and to determine the level of precision and sources of heterogeneity in the rupture risk estimate.

METHODS

This study was prospectively registered with the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42019121522). The Ovid MEDLINE, EMBASE, Web of Science Core Collection, and the Cochrane Central Register of Controlled Trials were searched (inception to August 2020). Studies with longitudinal follow-up of patients with UIAs ( ≤10 mm to ≤3 mm) without endovascular or neurosurgical repair were eligible. We included studies, which provided details of aneurysm size and in which UIA rupture was reported as an outcome. The primary outcome of the pooled proportion of UIA rupture during follow-up was synthesized with random-effects meta-analysis; heterogeneity was explored using meta-regression.

RESULTS

A total of 31 studies that included 13,800 UIAs ≤10 mm in size were eligible for data synthesis. The pooled proportion of ≤10 mm UIAs that ruptured when managed without repair was 1.1% (95% CI 0.8-1.5; I 2 = 52.9%) over 3.7 years. Findings were consistent in sensitivity analyses at all the size stratified thresholds including ≤5 and ≤3 mm; rupture occurred in 1.0% (95% CI 0.8-1.3; I 2 = 0%) of 7,280 ≤5 mm UIAs and 0.8% (95% CI 0.4-1.5; I 2 = 0%) of 1,228 ≤3 mm UIAs managed without repair. In higher quality studies with lower risk of bias, rupture occurred in 1.8% (95% CI 1.5-2.0; I 2 = 0%) over 3.9 years. In meta-regression, aneurysm size, shape, anatomical location, and exposure to prior subarachnoid hemorrhage were not identified as sources of heterogeneity.

CONCLUSION

For every 1,000 UIAs that are 10 mm or less in size and selected for conservative management without repair, between 8 and 15 UIAs are estimated to rupture over 3.7 years. When stratified by size, these pooled rupture risk estimates are consistent and clinically applicable for ≤5 mm UIAs selected for management without repair.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier: CRD42019121522.

Analysis of Factors Related to Growth and Growth Patterns of Unruptured Intracranial Aneurysms

Objective

Methods

Results

Conclusion

Imaging versus Intervention in Managing Small Unruptured Intracranial Aneurysms: A Cost-Effectiveness Analysis

OBJECTIVE

Current guidelines recommend active surveillance with serial magnetic resonance angiography (MRA) for management of small, asymptomatic unruptured anterior circulation aneurysms (UIAs). We sought to determine the cost-effectiveness of active surveillance compared to immediate surgery.

METHODS

We developed a Markov cost-effectiveness model simulating patients with small (<7 mm) UIAs managed by active surveillance via MRA, immediate surgery, or watchful waiting. Inputs for the model were abstracted from the literature and used to construct a comprehensive model following persons from diagnosis to death. Outcomes were quality-adjusted life-years (QALYs), lifetime medical costs (2015 USD), and incremental cost-effectiveness ratios (ICERs). Cost-effectiveness, deterministic, and probabilistic sensitivity analyses were performed.

RESULTS

Immediate surgical treatment was the most cost-effective management strategy for small UIAs with ICER of USD 45,772 relative to active surveillance. Sensitivity analysis demonstrated immediate surgery was the preferred strategy, if rupture rate was >0.1%/year and if the diagnosis age was <70 years, while active surveillance was preferred if surgical complication risk was >11%. Probabilistic sensitivity analysis demonstrated that at a willingness-to-pay of USD 100,000/QALY, immediate surgical treatment was the most cost-effective strategy in 64% of iterations.

CONCLUSION

Immediate surgical treatment is a cost-effective strategy for initial management of small UIAs in patients <70 years of age. While more costly than MRA, surgical treatment increased QALY. The cost-effectiveness of immediate surgery is highly sensitive to diagnosis age, rupture rate, and surgical complication risk. Though there are a wide range of rupture rates and complications associated with treatment, this analysis supports the treatment of small, unruptured anterior circulation intracranial aneurysms in patients <70 years of age.

Risk factors for the progression of unruptured intracranial aneurysms in patients followed by CT/MR angiography

Background

The progression of an unruptured intracranial aneurysm (UIA) is associated with a higher rupture risk. The aim of this study was to identify the risk factors for the progression of UIAs among Chinese adults and compare them with the ELAPSS (Earlier subarachnoid hemorrhage, IA Location, Age, Population, IA Size and Shape) score.

Methods

Four hundred thirty-eight consecutive patients with 491 UIAs were followed and reviewed retrospectively from August 2011 to November 2019. Follow-up images of the UIAs were used to determine changes in IA size and shape. Patients and IAs were divided into non-progression and progression groups. In addition to the clinical characteristics of the patients, the features of the IAs (e.g., size and shape) were evaluated by computed tomography angiography (CTA) or magnetic resonance angiography (MRA). Independent risk factors for UIA progression were studied using multiple Cox proportional hazards regression analysis. In addition, the diagnostic value of the ELAPSS score for the prediction of UIA progression was calculated.

Results

Seventy-two IAs in 68 patients progressed during a mean follow-up time of 24.2±19.68 months. IAs located at the bifurcation [odds ratio (OR) 2.600], with an irregular shape (OR 2.981) or having a high aspect ratio (AR, OR 2.430) were correlated with progression. Based on these three factors, the threshold value of our predictive score was 0.5, and the area under the curve (AUC), sensitivity and specificity were 0.756, 93.1% and 40.6%, respectively, while the AUC, sensitivity and specificity of the ELAPSS score were 0.711, 55.6%, and 75.2%, respectively.

Conclusions

IAs located at the bifurcation, with an irregular shape and with an elevated AR are risk factors for UIA progression in the Chinese population. Our predictive score is of great value in predicting the risk of UIA progression.

Wall Redness of Enlarged Unruptured Cerebral Aneurysm

OBJECTIVES

The wall of enlarged unruptured cerebral aneurysm (EUCA) is thought to be reddish, thin, and fragile. This study aimed to evaluate the EUCA wall redness based on quantitative signal intensity method and to compare the clinical and radiological characteristics between EUCA and non-EUCA.

MATERIALS & METHODS

In this retrospective analysis, red (R), green (G), blue (B), and RGB signal intensities of aneurysm were quantitatively measured using an intraoperative digital picture in 150 cases. Color intensities were measured by two independent investigators. Aneurysm redness was defined as an R/RGB ratio since the brightness of the operative field differed by each surgery or angle of the microscope.

RESULTS

The median aneurysm size was 4.9 mm (IQR 3.9-5.9 mm). Median color intensity of R, G, B, RGB, and R/RGB ratio were 206 (185-215), 129 (107-150), 136 (115-157), 157 (140-174), and 1.26 (1.20-1.38), respectively. The intraclass correlation coefficient for R/RGB ratio was 0.73 (P<0.0001). The proportion of female sex was significantly higher for EUCA (p = 0.019). Median R/RGB ratio in GUCA was significantly larger than that of non-EUCA (OR 1.25, 95% CI 1.19-1.35) (p = 0.035). Even after adjustment of female sex, a R/RGB ratio ≧1.36 was related to EUCA (OR 3.02, 95% CI 1.30-7.02).

CONCLUSIONS

The present study showed that a R/RGB ratio could be calculated easily and a larger R/RGB ratio was related to EUCA. When EUCA is managed by surgical treatment, more careful manipulation should be needed compared to non-EUCA due to a "red" wall of EUCA.

Radiological surveillance of small unruptured intracranial aneurysms: a systematic review, meta-analysis, and meta-regression of 8428 aneurysms

With the widespread use of imaging techniques, the possibility that an asymptomatic unruptured intracranial aneurysm (UIA) is detected has increased significantly. There is no established consensus regarding follow-up, duration, and frequency of such imaging surveillance. The objectives of this study include assessing the growth rate and rupture risk of small (less than 7mm) UIAs, identifying associated risk factors and providing an aneurysm surveillance protocol in appropriately selected patients. Systematic searches of Medline, Embase, and Cochrane Central were undertaken from database inception to March 2020 for published studies reporting the growth and rupture risks of small UIAs. Twenty-one studies reporting 8428 small UIAs were included in our meta-analysis. The pooled mean age was 61 years (95% CI: 55-67). The mean follow-up period for growth and rupture ranged from 11 to 108 months, with the pooled mean follow-up period across 14 studies being 42 months (95% CI: 33-51). Pooled overall growth rate was 6.0% (95% CI: 3.8-8.7). Pooled growth rates for aneurysms < 5mm and < 3 mm were 5.2% (95% CI: 3.0-7.9) and 0.8% (95% CI: 0.0-6.1), respectively. Pooled overall rupture rate was 0.4% (95% CI: 0.2-0.7). From the meta-regression analysis, having multiple aneurysms, smoking, hypertension, and personal history of SAH did not significantly predict growth, and a personal history of SAH, smoking, hypertension, and multiple aneurysms were not statistically significant predictors of rupture. Our findings suggest that small UIAs have low growth and rupture rates and very small UIAs have little or no risk for rupture. In the setting of incidental small UIAs, patients with multiple and/or posterior circulation aneurysms require more regular radiological monitoring.

Clinical relevance of short-term follow-up of unruptured intracranial aneurysms

OBJECTIVE

Unruptured intracranial aneurysms are common incidental findings on brain imaging. Short-term follow-up for conservatively treated aneurysms is routinely performed in most cerebrovascular centers, although its clinical relevance remains unclear. In this study, the authors assessed the extent of growth as well as the rupture risk during short-term follow-up of conservatively treated unruptured intracranial aneurysms. In addition, the influence of patient-specific and aneurysm-specific factors on growth and rupture risk was investigated.

METHODS

The authors queried their prospective institutional neurovascular registry to identify patients with unruptured intracranial aneurysms and short-term follow-up imaging, defined as follow-up MRA and/or CTA within 3 months to 2 years after initial diagnosis. Medical records and questionnaires were used to acquire baseline information. The authors measured aneurysm size at baseline and at follow-up to detect growth. Rupture was defined as a CT scan-proven and/or CSF-proven subarachnoid hemorrhage (SAH).

RESULTS

A total of 206 consecutive patients with 267 conservatively managed unruptured aneurysms underwent short-term follow-up at the authors' center. Seven aneurysms (2.6%) enlarged during a median follow-up duration of 1 year (range 0.3-2.0 years). One aneurysm (0.4%) ruptured 10 months after initial discovery. Statistically significant risk factors for growth or rupture were autosomal-dominant polycystic kidney disease (RR 8.3, 95% CI 2.0-34.7), aspect ratio > 1.6 or size ratio > 3 (RR 10.8, 95% CI 2.2-52.2), and initial size ≥ 7 mm (RR 10.7, 95% CI 2.7-42.8).

CONCLUSIONS

Significant growth of unruptured intracranial aneurysms may occur in a small proportion of patients during short-term follow-up. As aneurysm growth is associated with an increased risk of rupture, the authors advocate that short-term follow-up is clinically relevant and has an important role in reducing the risk of a potential SAH.

Unruptured intracranial aneurysm growth trajectory: occurrence and rate of enlargement in 520 longitudinally followed cases

OBJECTIVE

As imaging technology has improved, more unruptured intracranial aneurysms (UIAs) are detected incidentally. However, there is limited information regarding how UIAs change over time to provide stratified, patient-specific UIA follow-up management. The authors sought to enrich understanding of the natural history of UIAs and identify basic UIA growth trajectories, that is, the speed at which various UIAs increase in size.

METHODS

From January 2005 to December 2015, 382 patients diagnosed with UIAs (n = 520) were followed up at UCLA Medical Center through serial imaging. UIA characteristics and patient-specific variables were studied to identify risk factors associated with aneurysm growth and create a predicted aneurysm trajectory (PAT) model to differentiate aneurysm growth behavior.

RESULTS

The PAT model indicated that smoking and hypothyroidism had a large effect on the growth rate of large UIAs (≥ 7 mm), while UIAs < 7 mm were less influenced by smoking and hypothyroidism. Analysis of risk factors related to growth showed that initial size and multiplicity were significant factors related to aneurysm growth and were consistent across different definitions of growth. A 1.09-fold increase in risk of growth was found for every 1-mm increase in initial size (95% CI 1.04-1.15; p = 0.001). Aneurysms in patients with multiple aneurysms were 2.43-fold more likely to grow than those in patients with single aneurysms (95% CI 1.36-4.35; p = 0.003). The growth rate (speed) for large UIAs (≥ 7 mm; 0.085 mm/month) was significantly faster than that for UIAs < 3 mm (0.030 mm/month) and for males than for females (0.089 and 0.045 mm/month, respectively; p = 0.048).

CONCLUSIONS

Analyzing longitudinal UIA data as continuous data points can be useful to study the risk of growth and predict the aneurysm growth trajectory. Individual patient characteristics (demographics, behavior, medical history) may have a significant effect on the speed of UIA growth, and predictive models such as PAT may help optimize follow-up frequency for UIA management.

Definition and Prioritization of Data Elements for Cohort Studies and Clinical Trials on Patients with Unruptured Intracranial Aneurysms: Proposal of a Multidisciplinary Research Group

INTRODUCTION

Variability in usage and definition of data characteristics in previous cohort studies on unruptured intracranial aneurysms (UIA) complicated pooling and proper interpretation of these data. The aim of the National Institute of Health/National Institute of Neurological Disorders and Stroke UIA and Subarachnoid Hemorrhage (SAH) Common Data Elements (CDE) Project was to provide a common structure for data collection in future research on UIA and SAH.

METHODS

This paper describes the development and summarization of the recommendations of the working groups (WGs) on UIAs, which consisted of an international and multidisciplinary panel of cerebrovascular specialists on research and treatment of UIAs. Consensus recommendations were developed by review of previously published CDEs for other neurological diseases and the literature on UIAs. Recommendations for CDEs were classified by priority into 'Core,' 'Supplemental-Highly Recommended,' 'Supplemental,' and 'Exploratory.'

RESULTS

Ninety-one CDEs were compiled; 69 were newly created and 22 were existing CDEs. The CDEs were assigned to eight subcategories and were classified as Core (8), Supplemental-Highly Recommended (23), Supplemental (25), and Exploratory (35) elements. Additionally, the WG developed and agreed on a classification for aneurysm morphology.

CONCLUSION

The proposed CDEs have been distilled from a broad pool of characteristics, measures, or outcomes. The usage of these CDEs will facilitate pooling of data from cohort studies or clinical trials on patients with UIAs.

Risk Factors for Intracranial Aneurysm Rupture: A Systematic Review

BACKGROUND

Intracranial aneurysm rupture prediction is poor, with only a few risk factors for rupture identified and used in clinical practice.

OBJECTIVE

To provide an overview of all the risk factors (including genetic, molecular, morphological, and hemodynamic factors) that have potential for use in clinical practice.

METHODS

We systematically searched PubMed and EMBASE and focused on factors that can be easily assessed in clinical practice, might be used for rupture prediction in clinical practice, and/or are potential targets for further research. Studies were categorized according to methodological quality, and a meta-analysis was performed, if possible.

RESULTS

We included 102 studies describing 144 risk factors that fulfilled predefined criteria. There was strong evidence for the morphological factors irregular shape (studied in 4 prospective cohort studies of high-quality, pooled odds ratio [OR] of 4.8 [95% confidence interval 2.7-8.7]), aspect ratio (pooled OR 10.2 [4.3-24.6]), size ratio, bottleneck factor, and height-to-width ratio to increase rupture risk. Moderate level of evidence was found for presence of contact with the perianeurysmal environment (pooled OR 3.5 [1.4-8.4]), unbalanced nature of this contact (pooled OR 17.8 [8.3-38.5]), volume-to-ostium ratio, and direction of the aneurysm dome (pooled OR 1.5 [1.2-1.9]).

CONCLUSION

Irregular aneurysm shape was identified as a risk factor with potential for use in clinical practice. The risk factors aspect ratio, size ratio, bottleneck factor, height-to-width ratio, contact with the perianeurysmal environment, volume-to-ostium ratio, and dome-direction should first be confirmed in multivariate analysis and incorporated in prediction models.

A systematic review and meta-analysis of risk factors for unruptured intracranial aneurysm growth

BACKGROUND

Many risk factors are associated with the growth of unruptured intracranial aneurysm; however, the effects of these risk factors on intracranial aneurysm growth remain poorly understood. Here, we performed a meta-analysis to evaluate the effects of these risk factors on intracranial aneurysm growth, incorporating different data types to provide comprehensive estimates of individual effects.

METHODS

We searched the Cochrane Library, PubMed, Embase, and Web of Science for cohort studies analyzing risk factors for aneurysm growth prior to January 10, 2019. The hazard ratio (HR) and odds ratio (OR) with its 95% confidence interval (CI) were calculated to assess the effect of individual risk factors on intracranial aneurysm growth. Both univariate analysis (UVA) and multivariate analysis (MVA) were performed. Two reviewers independently assessed the quality of the trials and the associated data. All statistical analyses were performed using standard statistical procedures provided in Review Manager 5.2.

RESULTS

We included 23 studies (N = 7208 participants) in this meta-analysis. A total of 944 patients (13.1%) experienced intracranial aneurysm growth during their follow-up times. Aneurysm size and smoking may have significant effects on the growth of intracranial aneurysm, with pooled ORs of 2.73 (95% CI 2.21-3.36; P < 0.00001) and 1.45 (95% CI 1.07-1.98; P = 0.02) respectively. However, our results indicated that subarachnoid hemorrhage (SAH) had a negative effect on the growth of intracranial aneurysm (OR 0.64; 95% CI 0.48-0.86; P = 0.003). Other risk factors such as irregular shape of intracranial aneurysm, female sex, and multiple aneurysms were inconsistent across studies due to differences in data types and effect estimates.

CONCLUSIONS

Our meta-analysis identified aneurysm size and smoking as independent risk factors for the growth of intracranial aneurysm, while prior SAH had a negative effect on the growth of intracranial aneurysm. The roles of other risk factors for intracranial aneurysm growth were inconsistent, with further research necessary to assess fully the roles of these factors in disease outcomes.

Small Aneurysms Should Be Clipped?

Background:

Cerebral aneurysm prevalence may vary from 0.4% to 10%. The decision to treat or not incidental aneurysms remains controversial, especially when the lesions are small (<5 mm). Many recent publications are demonstrating that these lesions often bleed.

Methods:

We reviewed admitted patients with angiographic studies submitted to intracranial aneurysm surgical treatment from April 2012 to July 2013 in the Neurosurgery Department of São Paulo Medical School University (15 months), to define the rate and risk of bleeding. In addition, we proceeded literature review with collected 357 papers (past 5 years) which were selected 50 that were focused on our research. Clinical patients’ status at the time of discharge was evaluated with the modified Rankin scale.

Results:

A series of 118 cases of surgically clipped aneurysms was analyzed: 73.7% woman; Ruptured (61 cases, 51%); middle cerebral artery (51 cases, 43%) was the more common aneurysm. Small size (<5 mm) was 25 cases (21%); that 2 died (16%), 3 (25%) with severe disability,restricted to bed and dependent on nursing care; blood pressure was the main risk factors (56%); and an aneurysm <2 mm (100%) was ruptured.

Conclusion:

The number of small aneurysms in our series was significant (25 cases, 21%), and its rate of bleeding was high (25 cases, 48%), resulting in death and disability in a significant number of cases. Our tendency is for surgical treatment when it is associated with risk factors.

MR Angiography Screening and Surveillance for Intracranial Aneurysms in Autosomal Dominant Polycystic Kidney Disease: A Cost-effectiveness Analysis

Background Autosomal dominant polycystic kidney disease (ADPKD) affects one in 400 to one in 1000 individuals; 10%-11% of these individuals have intracranial aneurysms. The frequency and patterns of screening for intracranial aneurysms have not been defined. Purpose To evaluate different MR angiography screening and surveillance strategies for unruptured intracranial aneurysms in patients with ADPKD. Materials and Methods A Markov decision-analytic model was constructed accounting for both costs and outcomes from a societal perspective. Five different management strategies were evaluated: (a) no screening for intracranial aneurysm, (b) one-time screening with annual MR angiography follow-up in patients with intracranial aneurysm, (c) MR angiographic screening every 5 years with endovascular treatment in detected intracranial aneurysm, (d) MR angiography screening every 5 years with annual MR angiography follow-up in patients with intracranial aneurysm, and (e) MR angiography screening every 5 years with biennial follow-up in patients with intracranial aneurysm. One-way, two-way, and probabilistic sensitivity analyses were performed. Results Base case calculation shows that MR angiography screening of patients with ADPKD every 5 years and annual follow-up in patients with detected intracranial aneurysm is the optimal strategy (cost, $19 839; utility, 25.86 quality-adjusted life years), which becomes more favorable as the life expectancy increases beyond 6 years. The conclusion remains robust in probabilistic and one-way sensitivity analyses. When the prevalence of intracranial aneurysms is greater than 10%, annual rupture risk is 0.35%-2.5%, and the rate of de novo aneurysm detection is lower than 1.8%, MR angiography screening every 5 years with annual MR angiography follow-up is the favorable strategy. Conclusion Screening for intracranial aneurysms with MR angiography in patients with autosomal dominant polycystic kidney disease is cost-effective. Repeat screening every 5 years should be performed after a negative initial study. Annual surveillance MR angiography is optimal in patients with detected, incidental intracranial aneurysm, and treatment may be considered in patients with growing, high-risk aneurysms. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Anzai in this issue.

Accuracy of detecting enlargement of aneurysms using different MRI modalities and measurement protocols

OBJECTIVE

Aneurysm growth is considered predictive of future rupture of intracranial aneurysms. However, how accurately neuroradiologists can reliably detect incremental aneurysm growth using clinical MRI is still unknown. The purpose of this study was to assess the agreement rate of detecting aneurysm enlargement employing generally used MRI modalities.

METHODS

Three silicone flow phantom models, each with 8 aneurysms of various sizes at different sites, were used in this study. The aneurysm models were identical except for an incremental increase in the sizes of the 8 aneurysms, which ranged from 0.4 mm to 2 mm. The phantoms were imaged on 1.5-T and 3-T MRI units with both time-of-flight (TOF) and contrast-enhanced MR angiography. Three independent expert neuroradiologists measured the aneurysms in a blinded manner using different measurement approaches. The individual and agreement detection rates of aneurysm enlargement among the 3 experts were calculated.

RESULTS

The mean detection rate of any increase in any aneurysmal dimension was 95.7%. The detection rates of the 3 observers (observers A, B, and C) were 98.0%, 96.6%, and 92.7%, respectively (p = 0.22). The detection rates of each MRI modality were 91.3% using 1.5-T TOF, 97.2% using 1.5-T with Gd, 95.8% using 3.0-T TOF, and 97.2% using 3.0-T with Gd (p = 0.31). On the other hand, the mean detection rate for aneurysm enlargement was 54.8%. Specifically, the detection rates of observers A, B, and C were 49.0%, 46.1%, and 66.7%, respectively (p = 0.009). As the incremental enlargement value increased, the detection rate for aneurysm enlargement increased. The use of 1.5-T Gd improved the detection rate for small incremental enlargement (e.g., 0.4–1 mm) of the aneurysm (p = 0.04). The location of the aneurysm also affected the detection rate for aneurysm enlargement (p < 0.0001).

CONCLUSIONS

The detection rate and interobserver agreement were very high for aneurysm enlargement of 0.4–2 mm. The detection rate for at least 1 increase in any aneurysm dimension did not depend on the choice of MRI modality or measurement protocol. Use of Gd improved the accuracy of measurement. Aneurysm location may influence the accuracy of detecting enlargement.

New Pathophysiological Considerations on Cerebral Aneurysms

Cerebral aneurysm is a common cerebrovascular disease that is sometimes complicated by rupture or an enlarged mass. We are now aggressively evaluating and managing unruptured cerebral aneurysms based on a significant concern for the high morbidity and mortality related to its associated complications. However, the actual rupture rate is very low and the diagnostic and treatment modalities are expensive and invasive, which may lead to unnecessary costs and potential medical complications. This disproportionate situation is related to a poor understanding of the natural course and pathophysiology of cerebral aneurysms. In consideration of the concept that not all cerebral aneurysms must be removed, we need to examine their course and progression more accurately. Cerebral aneurysms may follow a variety of pathophysiological scenarios over their lifetime, from formation to growth and rupture. The disease course and the final outcome can differ depending on the timing and intensity of the pathological signals acting on the cerebral vessel wall. We should delineate a method of predicting the stability and risk of rupture of the lesion based on a comprehensive knowledge of the vessel wall integrity. This review deals with the basic knowledge and advanced concepts underlying the pathophysiology of cerebral aneurysms.

Influence of aging-induced flow waveform variation on hemodynamics in aneurysms present at the internal carotid artery: A computational model-based study

The variation of blood flow waveform in the internal carotid artery (ICA) with age is a well-documented hemodynamic phenomenon, but little is known about how such variation affects the characteristics of blood flow in aneurysms present in the region. In the study, hemodynamic simulations were conducted for 26 ICA aneurysms, with flow waveforms measured in the ICAs of young and older adults being used respectively to set the inflow boundary conditions. Obtained results showed that replacing the young-adult flow waveform with the older-adult one led to little changes (<10%) in simulated time-averaged wall shear stress (WSS), transient maximum WSS, relative residence time and trans-aneurysm pressure loss coefficient, but resulted in a marked increase (32.36 ± 17.24%) in oscillatory shear index (OSI). Frequency-domain wave analysis revealed that the progressive enhancement of low-frequency harmonics dominated the observed flow waveform variation with age and was a major factor contributing to the increase in OSI. Cross-sectional comparisons among the aneurysms further revealed that the degree of increase in OSI correlated positively with some specific morphological features of aneurysm, such as aspect ratio and size ratio. In summary, the study demonstrates that the variation in flow waveform with age augments the oscillation of WSS in ICA aneurysms, which underlies the importance of setting patient-specific boundary conditions in hemodynamic studies on cerebral aneurysms, especially those involving long-term patient follow-up or cross-sectional comparison among patients of different ages.

Aneurysm Size is the Strongest Risk Factor for Intracranial Aneurysm Growth in the Eastern Finnish Population

BACKGROUND

Saccular intracranial aneurysm (sIA) growth during follow-up is associated with high risk for subsequent rupture. Finnish patients have been suggested to have higher risk for subarachnoid hemorrhage, but follow-up studies of sIA growth in the Finnish population are scarce.

OBJECTIVE

To identify the strongest risk factors for sIA growth in Eastern Finnish population by studying 205 patients with 350 unruptured sIAs with angiographic follow-up imaging.

METHODS

In this population-based cohort study, we included unruptured sIA patients from the Kuopio University Hospital Intracranial Aneurysm Patient and Family database with at least 6 mo of angiographic follow-up after the diagnosis of sIAs. Angiograms were re-evaluated to detect aneurysms with growth of at least 1.0 mm. Cox regression analysis with patient- and aneurysm-related risk factors was used to calculate hazard ratios with 95% confidence intervals for growth. In addition, we tested the diagnostic value of previously introduced PHASES score for the prediction of sIA growth in Eastern Finnish population.

RESULTS

Of the 350 unruptured aneurysms, 36 (10.3%) showed growth during median follow-up of 1.7 yr and total follow-up of 790 yr. In the multivariate Cox regression analysis, sIA size and location in the middle cerebral artery were significant risk factors for sIA growth. In receiver operator characteristic curves, both PHASES score and sIA size had relatively low areas under the curve.

CONCLUSION

Our study indicates that aneurysm size is the strongest risk factor for aneurysm growth in Eastern Finnish population. Further studies are required to identify new risk factors for aneurysm growth.

Subarachnoid hemorrhage after surgical treatment of unruptured intracranial aneurysms

OBJECTIVE Only a few previous studies have investigated subarachnoid hemorrhage (SAH) after surgical treatment in patients with unruptured intracranial aneurysms (UIAs). Given the improvement in long-term outcomes of embolization, more extensive data are needed concerning the true rupture rates after microsurgery in order to provide reliable information for treatment decisions. The purpose of this study was to investigate the incidence of and risk factors for postoperative SAH in patients with surgically treated UIAs. METHODS Data from 702 consecutive patients harboring 852 surgically treated UIAs were evaluated. Surgical treatments included neck clipping (complete or incomplete), coating/wrapping, trapping, proximal occlusion, and bypass surgery. Clippable UIAs were defined as UIAs treated by complete neck clipping. The annual incidence of postoperative SAH and risk factors for SAH were studied using Kaplan-Meier survival analysis and Cox proportional hazards regression models. RESULTS The patients' median age was 64 years (interquartile range [IQR] 56-71 years). Of 852 UIAs, 767 were clippable and 85 were not. The mean duration of follow-up was 731 days (SD 380 days). During 1708 aneurysm years, there were 4 episodes of SAH, giving an overall average annual incidence rate of 0.23% (95% CI 0.12%-0.59%) and an average annual incidence rate of 0.065% (95% CI 0.0017%-0.37%) for clippable UIAs (1 episode of SAH, 1552 aneurysm-years). Basilar artery location (adjusted hazard ratio [HR] 23, 95% CI 2.0-255, p = 0.0012) and unclippable UIA status (adjusted HR 15, 95% CI 1.1-215, p = 0.046) were significantly related to postoperative SAH. An excellent outcome (modified Rankin Scale score of 0 or 1) was achieved in 816 (95.7%) of 852 cases overall and in 748 (98%) of 767 clippable UIAs at 12 months. CONCLUSIONS In this large case series, microsurgical treatment of UIAs was found to be safe and effective. Aneurysm location and unclippable morphologies were related to postoperative SAH in patients with surgically treated UIAs.

Cerebral vasculitis and intracranial multiple aneurysms in a child with Lyme neuroborreliosis

Introduction. Lyme borreliosis is a multisystem tick-borne disease caused by Borrelia burgdorferi. Neurological manifestations are reported in up to 15 % of adult patients with Lyme disease, while the frequency among children is higher. The most common manifestations are painful radiculopathy, facial nerve paresis and lymphocytic meningitis. Epileptic seizures and cerebral vasculitis with stroke or aneurysms are very rare complications.

Case presentation. We describe a paediatric patient with sensorineural auditory dysfunction, headache, fatigue and epileptic seizures as sequelae of meningoencephalitis/Lyme neuroborreliosis (LNB) caused by B. burgdorferi. Brain magnetic resonance imaging revealed widespread enhancement of the leptomeninges, cranial nerves and artery walls compatible with vasculitis and disturbances in cerebrospinal fluid (CSF) circulation. The patient was treated with ceftriaxone for 2 weeks. Two years later, the patient had an ischemic stroke. Brain magnetic resonance angiography revealed multiple aneurysms, which were not present previously. The largest aneurysm was operated rapidly. The patient was treated with another course of intravenous ceftriaxone for 4 weeks and pulse therapy with corticosteroids. He recovered well.

Comparison of Rates of Growth between Unruptured and Ruptured Aneurysms Using Magnetic Resonance Angiography

BACKGROUND AND PURPOSE

Growth is a key risk factor for rupture of unruptured cerebral aneurysms. There are few reports of investigations into the actual growth of ruptured intracranial aneurysms. The aim of the present study was to ascertain the risk of rupture of aneurysms based on the growth of unruptured and ruptured aneurysms.

METHODS

Changes in size on magnetic resonance angiography (MRA) were examined in 50 patients with ruptured cerebral aneurysms. Images obtained before and after subarachnoid hemorrhage were used. Moreover, changes in aneurysm size were retrospectively examined in 73 patients with 100 unruptured cerebral aneurysms that were followed serially with MRA that was performed using a 1.5-T or 3-T system. The size of the aneurysm was determined by measuring the maximum diameter on maximum intensity projection MRA images. Based on these data, the annual growth rates (mm growth/year) of unruptured and ruptured aneurysms were calculated and compared.

RESULTS

The median annual growth rate of ruptured aneurysms was significantly greater than that of unruptured aneurysms (.69 versus .077 mm/year, P < .01). The annual growth rates of ruptured aneurysms showed a negative correlation between the duration from initial MRA to the time of rupture.

CONCLUSION

A high annual growth rate is a key risk factor for aneurysm rupture. This finding provides strong evidence for the treatment of unruptured cerebral aneurysms.

Growth and Rupture Risk of Small Unruptured Intracranial Aneurysms: A Systematic Review

BACKGROUND

Small unruptured intracranial aneurysms (UIAs) are increasingly diagnosed. Management depends on growth and rupture risks, which may vary by aneurysm size.

PURPOSE

To summarize evidence about the growth and rupture risk of UIAs 7 mm and smaller and to explore differences in growth and rupture risks of very small (≤3 mm) and small (≤5 mm) aneurysms.

DATA SOURCES

MEDLINE, EMBASE, Scopus, and the Cochrane Library from inception to 2017 (with no language restrictions).

STUDY SELECTION

Published case series and observational studies that reported natural history data on UIAs 7 mm and smaller.

DATA EXTRACTION

2 reviewers abstracted study information, evaluated study quality, and graded strength of evidence.

DATA SYNTHESIS

Of 26 studies, 5, 10, and 8 described the growth rate of aneurysms 3 mm and smaller, 5 mm and smaller, and 7 mm and smaller, respectively, whereas rupture rates were reported in 7, 11, and 13 studies for aneurysms 3 mm and smaller, 5 mm and smaller, and 7 mm and smaller, respectively. The annualized growth rate was less than 3% in all but 1 study for all 3 size categories. The annualized rupture rate was 0%, less than 0.5%, and less than 1% for the 3 size categories, respectively. Strength of evidence was very low quality for growth rates and low quality for rupture rates.

LIMITATION

Heterogeneous definitions of growth; heterogeneous and selective treatment and follow-up methods, particularly in high-risk patients.

CONCLUSION

Poor-quality evidence suggests that small UIAs have low growth and rupture rates and very small UIAs have little or no risk for rupture.

PRIMARY FUNDING SOURCE

None.

The Rupture Risk of Aneurysm in the Anterior Communicating Artery: A Single Center Study

Objective

The aim of this study was to evaluate the characteristics of ruptured aneurysms at anterior communicating artery (A com) with an analysis of clinical and morphological data, which could further our understanding of the risks of ruptured A com aneurysms.

Materials and Methods

An analysis of data with 86 ruptured and 44 unruptured A com aneurysms were analyzed using a digital subtraction angiography or 3-dimensional computed tomography angiography between January 2010 and December 2015 in a single center.

Results

Fifty-five percent of ruptured A com aneurysms were smaller than 4 mm in size. They had a smooth wall (44%), with a mean size ratio of 4.22 (range: 0.7-14.3) and mean height/width ratio of 1.48 (range: 0.5-2.9); 23 patients of A1 positive difference. Unruptured aneurysms were mostly 2-10 mm in size (94%) and had an irregular wall (43%), with a mean size ratio of 4.1 (range: 0.8-9.1) and mean height/width ratio of 1.2 (range: 0.1-2.6); 6 patients of A1 positive difference. In terms of the morphology of aneurysms, size of A com, maximum aneurysm size, neck width, aneurysm wall morphology, and size ratio were not different with statistical significance. However, dominance of A1 (p = 0.01) and height/width ratio (p = 0.03) were found to be a significant predictive factor for rupture of A com aneurysms.

Conclusion

To better understand the rupture risk of A com aneurysms, a large, multicenter, collaborative, and prospective study should be performed in the future.

Is Regular Screening for Intracranial Aneurysm Necessary in Patients with Autosomal Dominant Polycystic Kidney Disease? A Systematic Review and Meta-analysis

BACKGROUND

The prevalence of intracranial aneurysm in patients with autosomal dominant polycystic kidney disease (ADPKD) is higher than that among the general population. We performed a systematic review and meta-analysis on the prevalence and natural history of intracranial aneurysm among patients with ADPKD.

METHODS

Medline, Embase, Web of Science and Scopus, from inception to July 2016, were searched for studies reporting the occurrence of intracranial aneurysms among participants with ADPKD. Two authors independently assessed the eligibility of all retrieved studies and extracted data. Information on the prevalence of intracranial aneurysms and their natural history in participants with ADPKD was collected from all included studies.

RESULTS

Fifteen studies with 1,490 participants with ADPKD were pooled to study about the prevalence of intracranial aneurysm in participants with ADPKD, and the prevalence rate was found to be 10% (95% CI 7-13%). Studies from China, Japan and Europe (Germany, Poland) reported a higher prevalence of intracranial aneurysm. Having a family history of haemorrhagic stroke or intracranial aneurysm was a risk factor for aneurysm occurrence. Twenty-three percent (95% CI 15-31%) of the participants had multiple aneurysms. Most of the aneurysms were small (<6 mm) and located in the anterior circulation. Five studies with 171 participants (83 with 106 aneurysms at baseline and 88 without) were analyzed to understand the natural history of aneurysms, with an incidence of aneurysm growth, new aneurysm and aneurysm rupture of 1.84% (followed up for 435 person-years), 0.57% (1,227 person-years) and 0.13% (792 person-years) respectively.

CONCLUSIONS

Screening for intracranial aneurysm is recommended in patients with ADPKD when there is a family history of haemorrhagic stroke or intracranial aneurysm and when they are from China, Japan or Europe (Germany, Poland). Based on existing data, regular imaging follow-up is not supported. High-quality, prospective studies are needed in the future.

Growth and subsequent disappearance of a ruptured small saccular intracranial aneurysm: A morphometric and flow-dynamic analysis

The growth of a ruptured small saccular aneurysm has rarely been documented. Also rare are reports of spontaneous thrombosis of ruptured small intracranial saccular aneurysms. However, there are no reported instances of ruptured small saccular aneurysms that have demonstrated an increase in size after rupture, subsequently thrombosed and disappeared from circulation. We report one such aneurysm in a patient who presented with subarachnoid hemorrhage from a ruptured small saccular aneurysm of the anterior communicating artery. The possible reasons for the initial growth and subsequent thrombosis of the aneurysm from morphometric and flow dynamic points of view are discussed.

Experimental Induction of Cerebral Aneurysms by Developmental Low Copper Diet

Optimal models are needed to understand the pathophysiology of human cerebral aneurysms (CA). We investigated the development of experimental CA by decreasing the activity of lysyl oxidases by dietary copper deficiency from the time of gestation and then augmenting vascular stress by angiotensin II infusion in adulthood. Rats were fed copper-free, low-copper, or normal diets at different time periods from gestation to adulthood. The incidences of CAs were evaluated and autopsies performed to determine the coexistence of cardiovascular diseases. A copper-free diet from gestation was associated with high mortality rates (79.1%) resulting from rupture of ascending aorta aneurysms; a low-copper diet led to acceptable mortality rates (13.6%) and produced CAs and subarachnoid hemorrhage in 46.4% and 3.6% of animals, respectively. Higher proportions of CAs (up to 33.3%) in the rats primed for copper deficiency from gestation ruptured following angiotensin II infusion from adulthood. Gene expression array analyses of the CAs indicated that genes involving extracellular matrix and vascular remodeling were altered in this model. This model enables future research to understand the entire pathogenetic basis of CA development and rupture in association with systemic vasculopathies.

Aneurysm growth and de novo aneurysms during aneurysm surveillance

OBJECTIVE Many low-risk unruptured intracranial aneurysms (UIAs) are followed for growth with surveillance imaging. Growth of UIAs likely increases the risk of rupture. The incidence and risk factors of UIA growth or de novo aneurysm formation require further research. The authors retrospectively identify risk factors and annual risk for UIA growth or de novo aneurysm formation in an aneurysm surveillance protocol. METHODS Over an 11.5-year period, the authors recommended surveillance imaging to 192 patients with 234 UIAs. The incidence of UIA growth and de novo aneurysm formation was assessed. With logistic regression, risk factors for UIA growth or de novo aneurysm formation and patient compliance with the surveillance protocol was assessed. RESULTS During 621 patient-years of follow-up, the incidence of aneurysm growth or de novo aneurysm formation was 5.0%/patient-year. At the 6-month examination, 5.2% of patients had aneurysm growth and 4.3% of aneurysms had grown. Four de novo aneurysms formed (0.64%/patient-year). Over 793 aneurysm-years of follow-up, the annual risk of aneurysm growth was 3.7%. Only initial aneurysm size predicted aneurysm growth (UIA < 5 mm = 1.6% vs UIA ≥ 5 mm = 8.7%, p = 0.002). Patients with growing UIAs were more likely to also have de novo aneurysms (p = 0.01). Patient compliance with this protocol was 65%, with younger age predictive of better compliance (p = 0.01). CONCLUSIONS Observation of low-risk UIAs with surveillance imaging can be implemented safely with good adherence. Aneurysm size is the only predictor of future growth. More frequent (semiannual) surveillance imaging for newly diagnosed UIAs and UIAs ≥ 5 mm is warranted.

Risk Factors for Growth of Intracranial Aneurysms: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Understanding risk factors for intracranial aneurysm growth is important for patient management. We performed a meta-analysis examining risk factors for intracranial aneurysm growth in longitudinal studies and examined the association between aneurysm growth and rupture.

MATERIALS AND METHODS

We searched the literature for longitudinal studies of patients with unruptured aneurysms. We examined the associations of demographics, multiple aneurysms, prior subarachnoid hemorrhage, family history of aneurysm or subarachnoid hemorrhage, smoking, and hypertension; and aneurysm shape, size, and location with aneurysm growth. We studied the association between aneurysm growth and rupture. A meta-analysis was performed by using a random-effects model by using summary statistics from included studies.

RESULTS

Twenty-one studies including 3954 patients with 4990 aneurysms with 13,294 aneurysm-years of follow-up were included. The overall proportion of growing aneurysms was 3.0% per aneurysm-year (95% CI, 2.0%-4.0%). Patient risk factors for growth included age older than 50 years (3.8% per year versus 0.9% per year, P < .01), female sex (3.2% per year versus 1.3% per year, P < .01), and smoking history (5.5% per year versus 3.5% per year, P < .01). Characteristics associated with higher growth rates included cavernous carotid artery location (14.4% per year), nonsaccular shape (14.7% per year versus 5.2% per year for saccular, P < .01), and aneurysm size (P < .01). Aneurysm growth was associated with a rupture rate of 3.1% per year compared with 0.1% per year for stable aneurysms (P < .01).

CONCLUSIONS

Observational evidence provided multiple clinical and anatomic risk factors for aneurysm growth, including age older than 50 years, female sex, smoking history, and nonsaccular shape. These findings should be considered when counseling patients regarding the natural history of unruptured intracranial aneurysms.

Changes of size and shape of small, unruptured intracranial aneurysms in repeated computed tomography angiography studies

Introduction

Unruptured intracranial aneurysms (UIAs) are frequently detected in noninvasive imaging studies such as computed tomography angiography (CTA) or magnetic resonance angiography (MRA). If small, UIAs are observed in these modalities in order to detect growth or shape change, but there are many questions about proper protocol of the follow-up.

Aim

To assess changes of small (< 7 mm) UIAs dome size and shape in repeated CTA studies as predictors of growth and rupture.

Material and methods

One hundred and ten UIAs (10 posterior circulation) in 70 patients (55 women) were observed, with a cumulative observation time of 333.32 years. Aneurysms’ dome and neck perpendicular dimensions were measured in the first and the last CTA study at least twice with the developed application. Confidence intervals (CI) for measurements and dome shape parameters were calculated. For aneurysms ruptured during follow-up intermediate studies were analyzed. Patients’ clinical information was recorded. The aneurysm growth detection algorithm integrated CI and spatial resolution of the CT scanner.

Results

Twenty-three aneurysms increased in volume, 10 in height and 14 in dome width. Volume increased in 90% of cases of height and 93% of width increase. Posterior circulation aneurysms grew faster than anterior ones (p < 0.003), but calculated time to significant size increase (eT) did not differ between the groups due to higher CI in the posterior circulation. Analysis of eT with Kaplan-Meier curves showed that 75% of growing aneurysms could be detected in the first 3 years of observation. During the follow-up 3 aneurysms bled, and they grew faster than other growing aneurysms. Two of the bleeding aneurysms formed daughter sacs.

Conclusions

Dome volume assessment is superior to single dimension assessment in aneurysm growth detection. Confidence intervals assessment helps to avoid overestimation of growth. Seventy-five percent of growing aneurysms could be detected in the first 3 years of observation. Daughter sac formation and fast increase in size are strong predictors of aneurysm rupture.

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

PURPOSE

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

METHODS

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

RESULTS

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

Unruptured Cerebral Aneurysms: Evaluation and Management

The evolution of imaging techniques and their increased use in clinical practice have led to a higher detection rate of unruptured intracranial aneurysms. The diagnosis of an unruptured intracranial aneurysm is a source of significant stress to the patient because of the concerns for aneurysmal rupture, which is associated with substantial rates of morbidity and mortality. Therefore, it is important that decisions regarding optimum management are made based on the comparison of the risk of aneurysmal rupture with the risk associated with intervention. This review provides a comprehensive overview of the epidemiology, pathophysiology, natural history, clinical presentation, diagnosis, and management options for unruptured intracranial aneurysms based on the current evidence in the literature. Furthermore, the authors discuss the genetic abnormalities associated with intracranial aneurysm and current guidelines for screening in patients with a family history of intracranial aneurysms. Since there is significant controversy in the optimum management of small unruptured intracranial aneurysms, we provided a systematic approach to their management based on patient and aneurysm characteristics as well as the risks and benefits of intervention.

PHASES Score for Prediction of Intracranial Aneurysm Growth

BACKGROUND AND PURPOSE

Growth of an intracranial aneurysm occurs in around 10% of patients at 2-year follow-up imaging and may be associated with aneurysm rupture. We investigated whether PHASES, a score providing absolute risks of aneurysm rupture based on 6 easily retrievable risk factors, also predicts aneurysm growth.

METHODS

In a multicenter cohort of patients with unruptured intracranial aneurysms and follow-up imaging with computed tomography angiography or magnetic resonance angiography, we performed univariable and multivariable Cox regression analyses for the predictors of the PHASES score at baseline, with aneurysm growth as outcome. We calculated hazard ratios and corresponding 95% confidence intervals (CI), with the PHASES score as continuous variable and after division into quartiles.

RESULTS

We included 557 patients with 734 unruptured aneurysms. Eighty-nine (12%) aneurysms in 87 patients showed growth during a median follow-up of 2.7 patient-years (range 0.5-10.8). Per point increase in PHASES score, hazard ratio for aneurysm growth was 1.32 (95% CI, 1.22-1.43). With the lowest quartile of the PHASES score (0-1) as reference, hazard ratios were for the second (PHASES 2-3) 1.07 (95% CI, 0.49-2.32), the third (PHASES 4) 2.29 (95% CI, 1.05-4.95), and the fourth quartile (PHASES 5-14) 2.85 (95% CI, 1.43-5.67).

CONCLUSIONS

Higher PHASES scores were associated with an increased risk of aneurysm growth. Because higher PHASES scores also predict aneurysm rupture, our findings suggest that aneurysm growth can be used as surrogate outcome measure of aneurysm rupture in follow-up studies on risk prediction or interventions aimed to reduce the risk of rupture.

Rapid aneurysm growth and rupture in systemic lupus erythematosus

BACKGROUND

Subarachnoid hemorrhage (SAH) due to intracranial aneurysm rupture is a major neurosurgical emergency associated with significant morbidity and mortality. Rapid aneurysm growth is associated with rupture. Systemic lupus erythematosus (SLE) is a multi-system autoimmune disorder whose complications can include cerebral vasculitis and vasculopathy. Intracranial aneurysms are not known to occur more frequently in SLE patients than the general population; however, aneurysm growth rates have not been studied in SLE.

CASE DESCRIPTION

We present a 43-year-old female with SLE on prednisone, hydroxychloroquine, and azathioprine with moderate disease activity who presented with severe, acute-onset headache and was found to have Hunt and Hess grade II SAH due to rupture of an 8 mm saccular anterior communicating artery (ACoA) aneurysm. The patient developed severe vasospasm, re-ruptured, and was taken for angiography and embolization, which was challenging due to a high degree of vasospasm and arterial stenosis. Review of imaging from less than 2 years prior demonstrated a normal ACoA complex without evidence of an aneurysm.

CONCLUSION

We review the literature and discuss the risk factors and pathophysiology of rapid aneurysm growth and rupture, as well as the pathologic vascular changes associated with SLE. Although SLE patients do not develop intracranial aneurysm at an increased rate, these changes may predispose them to higher incidence of growth and rupture. This possibility-coupled with increased morbidity and mortality of SAH in SLE-suggests that SAH should be considered in SLE patients presenting with headache, and advocates for more aggressive treatment of SLE patients with unruptured aneurysms.

Clinical, Radiological, and Flow-Related Risk Factors for Growth of Untreated, Unruptured Intracranial Aneurysms

Background and Purpose—

Unruptured intracranial aneurysms are frequently followed to monitor aneurysm growth. We studied the yield of follow-up imaging and analyzed risk factors for aneurysm growth.

Methods—

We included patients with untreated, unruptured intracranial aneurysms and ≥6 months of follow-up imaging from 2 large prospectively collected databases. We assessed the proportion of patients with aneurysm growth and performed univariable and multivariable Cox regression analyses to calculate hazard ratios with corresponding 95% confidence intervals (CI) for clinical and radiological risk factors for aneurysm growth. We repeated these analyses for the subset of small (<7 mm) aneurysms.

Results—

Fifty-seven (12%) of 468 aneurysms in 363 patients grew during a median follow-up of 2.1 years (total follow-up, 1372 patient-years). In multivariable analysis, hazard ratios for aneurysm growth were as follows: 1.1 (95% CI, 1.0–1.2) per each additional mm of initial aneurysm size; 2.7 (95% CI, 1.2–6.4) for dome > neck ratio; 2.1 (95% CI, 0.9–4.9) for location in the posterior circulation; and 2.0 (95% CI, 0.8–4.8) for multilobarity. In the subset of aneurysms <7 mm, 37 of 403 (9%) enlarged. In multivariable analysis, hazard ratios for aneurysm growth were 1.1 (95% CI, 0.8–1.5) per each additional mm of initial aneurysm size, 2.2 (95% CI, 1.0–4.8) for smoking, 2.9 (95% CI, 1.0–8.5) for multilobarity, 2.4 (95% CI, 1.0–5.8) for dome/neck ratio, and 2.0 (95% CI, 0.6–7.0) for location in the posterior circulation.

Conclusions—

Initial aneurysm size, dome/neck ratio, and multilobarity are risk factors for aneurysm growth. Cessation of smoking is pivotal because smoking is a modifiable risk factor for growth of small aneurysms.

Female sex as a risk factor for the growth of asymptomatic unruptured cerebral saccular aneurysms in elderly patients

Object

The prevalence of patients with asymptomatic unruptured intracranial aneurysms (UIAs) increases with the advancing age of the general population. The goal of the present study was to identify risk factors for the growth of UIAs detected with serial MR angiography (MRA) in patients 70 years of age or older.

Methods

This prospective study enrolled 79 patients (age range 70–84 years) with 98 UIAs. Patients were followed up every 4 months, including an assessment of the aneurysm diameter and morphological changes on MRA, neurological status, and other medical conditions. Aneurysm growth was categorized into two different patterns on the basis of the MRA findings: 1) maximum increase in aneurysm diameter of 2 mm or more; and 2) obvious morphological change, such as the appearance of a bleb.

Results

The mean duration of follow-up was 38.5 months (250.2 patient-years). Aneurysm rupture did not occur, but aneurysm growth was observed in 8 aneurysms (8 patients) during the study period. Univariate analysis showed that female sex, patient age ≥ 75 years, and an aneurysm location in the internal carotid artery (ICA) or middle cerebral artery (MCA) were associated with aneurysm growth (p = 0.04, p = 0.04, and p < 0.001, respectively). Multivariate analysis demonstrated that female sex was the only independent predictor of aneurysm growth (p = 0.0313, OR 2.3, 95% CI 1.3–30.2).

Conclusions

Female sex is an independent risk factor for the growth of UIAs in elderly patients. In addition, an age ≥ 75 years and aneurysm location in the ICA or MCA are characteristics that may warrant additional attention during follow-up imaging.

Aneurysms of the anterior and posterior cerebral circulation: comparison of the morphometric features

Background

Intracranial aneurysms (IAs) located in the posterior circulation are considered to have higher annual bleed rates than those in the anterior circulation. The aim of the study was to compare the morphometric factors differentiating between IAs located in the anterior and posterior cerebral circulation.

Methods

A total number of 254 IAs diagnosed between 2009 and 2012 were retrospectively analyzed. All patients qualified for diagnostic, three-dimensional rotational angiography. IAs were assigned to either the anterior or posterior cerebral circulation subsets for the analysis. Means were compared with a t-test. The univariate and stepwise logistic regression analyses were used to determine the predictors of morphometric differences between the groups. For the defined predictors, ROC (receiver-operating characteristic) curves and interactive dot diagrams were calculated with the cutoff values of the morphometric factors.

Results

The number of anterior cerebral circulation IAs was 179 (70.5 %); 141 (55.5 %) aneurysms were ruptured. Significant differences between anterior and posterior circulation IAs were found for: the parent artery size (5.08 ± 1.8 mm vs. 3.95 ± 1.5 mm; p < 0.05), size ratio (2.22 ± 0.9 vs. 3.19 ± 1.8; p < 0.045) and aspect ratio (AR) (1.91 ± 0.8 vs. 2.75 ± 1.8; p = 0.02). Predicting factors differentiating anterior and posterior circulation IAs were: the AR (OR = 2.20; 95 % CI 1.80–270; Is 270 correct or should it be 2.70 and parent artery size (OR = 0.44; 95 % CI 0.38–0.54). The cutoff point in the ROC curve was 2.185 for the AR and 4.89 mm for parent artery size.

Conclusions

Aspect ratio and parent artery size were found to be predictive morphometric factors in differentiating between anterior and posterior cerebral IAs.

Intracranial aneurysmal pulsatility as a new individual criterion for rupture risk evaluation: biomechanical and numeric approach (IRRAs Project)

BACKGROUND AND PURPOSE

The present study follows an experimental work based on the characterization of the biomechanical behavior of the aneurysmal wall and a numerical study where a significant difference in term of volume variation between ruptured and unruptured aneurysm was observed in a specific case. Our study was designed to highlight by means of numeric simulations the correlation between aneurysm sac pulsatility and the risk of rupture through the mechanical properties of the wall.

MATERIALS AND METHODS

In accordance with previous work suggesting a correlation between the risk of rupture and the material properties of cerebral aneurysms, 12 fluid-structure interaction computations were performed on 12 "patient-specific" cases, corresponding to typical shapes and locations of cerebral aneurysms. The variations of the aneurysmal volume during the cardiac cycle (ΔV) are compared by using wall material characteristics of either degraded or nondegraded tissues.

RESULTS

Aneurysms were located on 6 different arteries: middle cerebral artery (4), anterior cerebral artery (3), internal carotid artery (1), vertebral artery (1), ophthalmic artery (1), and basilar artery (1). Aneurysms presented different shapes (uniform or multilobulated) and diastolic volumes (from 18 to 392 mm3). The pulsatility (ΔV/V) was significantly larger for a soft aneurysmal material (average of 26%) than for a stiff material (average of 4%). The difference between ΔV, for each condition, was statistically significant: P=.005.

CONCLUSIONS

The difference in aneurysmal pulsatility as highlighted in this work might be a relevant patient-specific predictor of aneurysm risk of rupture.

Hypertension predisposes to the formation of saccular intracranial aneurysms in 467 unruptured and 1053 ruptured patients in Eastern Finland

OBJECTIVE

Hypertension associates with subarachnoid hemorrhage from saccular intracranial aneurysm (sIA-SAH) when compared to matched controls or general population. Few series compare hypertension in unruptured sIA versus sIA-SAH, so its impact on the sIA disease remains uncertain.

METHODS

Kuopio sIA Database ( www.uef.fi/ns ) contains all cases of unruptured and ruptured sIAs admitted to Kuopio University Hospital from its Eastern Finnish catchment population. We compared the age-adjusted incidence of drug-treated hypertension in 467 unruptured and 1053 ruptured sIA patients admitted to Kuopio University Hospital from 1995 to 2007, using the national registry of prescribed medicines.

RESULTS

Antihypertensive medication was more frequent in the unruptured (73% versus 62%) with higher age-adjusted incidence. At sIA diagnosis, the sIA-SAH group had more often untreated hypertension (29% versus 23%). The size of unruptured sIAs increased with age at sIA diagnosis, independently of hypertension. Multiple sIAs, familial sIA, and sIA-SAH were not associated with hypertension in multivariate analysis. Results indicate that drug-treated hypertension associates with the formation of sIAs rather than their growth or rupture.

CONCLUSION

Hypertension is highly prevalent in the carriers of unruptured sIAs when compared to those with ruptured sIA. Hypertension may associate with the sIA formation, and may predispose to the rupture of sIA if untreated.

Factors affecting formation and rupture of intracranial saccular aneurysms

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