Aneurysm size: a prognostic factor for rupture

Trends in the Age of Patients Treated for Unruptured Intracranial Aneurysms from 1990 to 2020

BACKGROUND

The decision for treatment for unruptured intracranial aneurysms (UIAs) is often difficult. Innovation in endovascular devices have improved the benefit-to-risk profile especially for elderly patients; however, the treatment guidelines from the past decade often recommend conservative management. It is unknown how these changes have affected the overall age of the patients selected for treatment. Herein, we aimed to study potential changes in the average age of the patients that are being treated over time.

METHODS

A systematic search of the literature was performed to identify all studies describing the age of the UIAs that were treated by any modality. Scatter diagrams with trend lines were used to plot the age of the patients treated over time and assess the presence of a potential significant trend via statistical correlation tests.

RESULTS

A total of 280 studies including 83,437 UIAs treated between 1987 and 2021 met all eligibility criteria and were entered in the analysis. Mean age of the patients was 55.5 years, and 70.7% were female. There was a significant increasing trend in the age of the treated patients over time (Spearman r: 0.250; P < 0.001), with a 1-year increase in the average age of the treated patients every 5 years since 1987.

CONCLUSIONS

The present study indicates that based on the treated UIA patient data published in the literature, older UIAs are being treated over time. This trend is likely driven by safer treatments while suggesting that re-evaluation of certain UIA treatment decision scores may be of great interest.

A novel parameter for the prediction of rupture risk of cerebral aneurysms based on morphology

Neurosurgeons often encounter dilemmas in the clinical management of cerebral aneurysms owing to an uncertainty of their rupture status and rupture risk. This study evaluates the influence of natural frequency of an aneurysm, as a novel morphological parameter to understand and analyze rupture status and risk prediction. In this work, we employ the natural frequency of 20 idealized and 50 patient specific aneurysms. The natural frequency of patient specific aneurysms is then compared against their rupture status. A strong correlation was observed between various morphological indicators and natural frequency for ideal and patient specific geometries. A statistical analysis with both Mann Whitney U test and T-test for rupture status against natural frequency has given a p-value less than 0.01 indicating a strong correlation between them. The correlation of morphological parameters with natural frequency from Pearson correlation coefficient and T-test suggests a holistic reflection of their effects on the natural frequency of an aneurysm. Thus, natural frequency could be a good indicator to discern the rupture potential of an aneurysm. The correlation between rupture status and natural frequency makes it a novel parameter that can differentiate between ruptured and unruptured patient specific aneurysms.

Ruptured Distal Middle Cerebral Artery Aneurysms-Characteristics and Strategy

BACKGROUND

Distal middle cerebral artery (dMCA) aneurysms are very rare. Most ruptured dMCA aneurysms lead to subarachnoid hemorrhage (SAH) coexisting with intracerebral hematoma (ICH), resulting in a deteriorating state. The risk factors of rupture of dMCA aneurysms remain unknown. To elucidate the risk of rupture, we studied differences between 4 ruptured and eleven unruptured dMCA aneurysms.

METHODS

We retrospectively analyzed patients diagnosed with a dMCA aneurysm according to the maximum size of the aneurysm, aspect ratio, and aneurysm size to vessel size (size ratio).

RESULTS

Four patients presented with SAH coexisting with ICH, resulting in a midline shift, caused by rupture of the dMCA aneurysm. The median aspect ratio of ruptured and unruptured dMCA aneurysms was 2.38 and 1.65, respectively, with no significant difference. The median maximum diameter of ruptured and unruptured dMCA aneurysms was 2.98 and 3.78 mm, respectively, with nonsignificant difference. The median size ratio of ruptured and unruptured dMCA aneurysms was 3.13 and 1.84, respectively, being significant difference (P < 0.02). The outcomes of 4 patients having ruptured dMCA aneurysm were as follows: one patient died due to the initial attack, and the others were severely disabled due to cerebral infarction caused by vasospasm.

CONCLUSIONS

Distal MCA aneurysms, even if they are small, may be likely to rupture leading to SAH complicated by ICH and result in a poor neurological state and unfavorable outcomes. We recommend aggressive treatment for dMCA aneurysms considering morphological factors such as the size ratio even if they are small and unruptured.

Risk factors for aneurysm rupture among Kazakhs: findings from a national tertiary

BACKGROUND

Rupture of intracranial aneurysms (RIA) leads to subarachnoid hemorrhage (SAH) with severe consequences. Although risks for RIA are established, the results vary between ethnic groups and were never studied in Kazakhstan. This study aimed to establish the risk factors of RIA in the Kazakh population.  METHODS: Retrospective analysis of 762 patients with single IAs, who attended the neurosurgical center from 2008 until 2018, was conducted. Demographic characteristics, such as age, sex, smoking status, and hypertension were considered. Descriptive and bivariate analyses were performed. A multivariable logistic regression model was built to identify factors correlated with RIA.

RESULTS

The mean age of participants was 48.49 ± 0.44 years old. The majority (68.37%) of IAs have ruptured. Of the ruptured aneurysms, 43.76% were < 6 mm, and 38.39% were located on the anterior cerebral and anterior communicating arteries (ACA). Logistic regression model indicates younger age group (16-40 years), smoking, having stage 3 hypertension, smaller IA size and its location on ACA increase the odds of rupture.

CONCLUSIONS

This study has revealed that younger, smoking patients with stage 3 arterial hypertension are at higher risk for RIA. Small aneurysms (< 6 mm) and location on ACA had increased odds of rupture, while larger aneurysms on internal carotid arteries had lower odds.

Management of multiple and unruptured cerebral aneurysms

The incidence of multiple aneurysms was 10.7–34% of CA. Multiple associated factors were found; hypertension was the most significant one and others like advancing age and female sex were also documented. The estimated prevalence of UA is 5–10%. They include those aneurysms that did not rupture and discovered incidentally and those presented with symptoms rather than SAH, e.g., cranial nerve palsy or mass effect. Unruptured intracranial aneurysms are diagnosed with higher frequency nowadays as a result of imaging techniques improvement. The reported annual rate of rupture of UA is approximately 0.7–1%. The natural history of unruptured cerebral aneurysms cannot be extrapolated from the evaluation of individuals with ruptured aneurysms. Multiple cerebral aneurysms pose an even greater risk than a single aneurysm; the risk of rebleeding from the original aneurysm is larger and occurs sooner. The natural course of the disease has led to a consensus that all multiple unruptured aneurysms should be treated when technically viable. However, the prophylactic treatment of multiple unruptured is still controversial. Weighing the risk of intervention to the risk of observation is a mandatory pathway. Factors like age of patients, size and location of the aneurysms influence the decision-making and the type of therapy to be elected.

Noninvasive quantification of cerebrovascular pressure changes using 4D Flow MRI

PURPOSE

Hemodynamic alterations are indicative of cerebrovascular disease. However, the narrow and tortuous cerebrovasculature complicates image-based assessment, especially when quantifying relative pressure. Here, we present a systematic evaluation of image-based cerebrovascular relative pressure mapping, investigating the accuracy of the routinely used reduced Bernoulli (RB), the extended unsteady Bernoulli (UB), and the full-field virtual work-energy relative pressure ( ν WERP) method.

METHODS

Patient-specific in silico models were used to generate synthetic cerebrovascular 4D Flow MRI, with RB, UB, and ν WERP performance quantified as a function of spatiotemporal sampling and image noise. Cerebrovascular relative pressures were also derived in 4D Flow MRI from healthy volunteers ( n = 8 ), acquired at two spatial resolutions (dx = 1.1 and 0.8 mm).

RESULTS

The in silico analysis indicate that accurate relative pressure estimations are inherently coupled to spatial sampling: at dx = 1.0 mm high errors are reported for all methods; at dx = 0.5 mm ν WERP recovers relative pressures at a mean error of 0.02 ± 0.25 mm Hg, while errors remain higher for RB and UB (mean error of -2.18 ± 1.91 and -2.18 ± 1.87 mm Hg, respectively). The dependence on spatial sampling is also indicated in vivo, albeit with higher correlative dependence between resolutions using ν WERP (k = 0.64, R2 = 0.81 for dx = 1.1 vs. 0.8 mm) than with RB or UB (k = 0.04, R2 = 0.03, and k = 0.07, R2 = 0.07, respectively).

CONCLUSION

Image-based full-field methods such as ν WERP enable cerebrovascular relative pressure mapping; however, accuracy is directly dependent on utilized spatial resolution.

Associations between morphology and hemodynamics of intracranial aneurysms based on 4D flow and black-blood magnetic resonance imaging

Background

Previous studies have hypothesized that intracranial aneurysm (IA) morphology interacts with hemodynamic conditions. Magnetic resonance imaging (MRI) provides a single image modality solution for both morphological and hemodynamic measurements for IA. This study aimed to explore the interaction between the morphology and hemodynamics of IA using black-blood MRI (BB-MRI) and 4D flow MRI.

Methods

A total of 97 patients with unruptured IA were recruited for this study. The IA size, size ratio (SR), and minimum wall thickness (mWT) were measured using BB-MRI. Velocity, blood flow, pulsatility index (PI), and wall shear stress (WSS) were measured with 4D flow MRI. The relationship between hemodynamic parameters and morphological indices was investigated by linear regression analysis and unpaired two-sample t-test. To determine the independent interaction, multiple linear regression analysis was further performed.

Results

The findings showed that mWT was negatively correlated with IA size (r=-0.665, P<0.001). Maximum blood flow in IA (Flow_IA) was positively correlated with IA size (r=0.458, P<0.001). The average WSS (WSS_avg) was negatively correlated with IA size (r=-0.650, P<0.001). The relationships remained the same after the multivariate analysis was adjusted for hemodynamic, morphologic, and demographic confounding factors. The WSS_avg was positively correlated with mWT (r=0.528, P<0.001). In the unpaired two-sample t-test, mWT, WSS_avg, and Flow_IA were statistically significantly associated with the size and SR of IAs.

Conclusions

There is potential for BB-MRI and 4D flow MRI to provide morphological and hemodynamic information regarding IA. Blood flow, WSS, and mWT may serve as non-invasive biomarkers for IA assessments, and may contribute to a more comprehensive understanding of the mechanism of IA.

A Simple Flow Classification Parameter Can Discriminate Rupture Status in Intracranial Aneurysms

BACKGROUND

A simple dimensionless aneurysm number ($An$), which depends on geometry and flow pulsatility, was previously shown to distinguish the flow mode in intracranial aneurysms (IA): vortex mode with a dynamic vortex formation/evolution if $An > 1$, and cavity mode with a steady shear layer if $An < 1$.

OBJECTIVE

To hypothesize that $An\ > \ 1$ can distinguish rupture status because vortex mode is associated with high oscillatory shear index, which, in turn, is statistically associated with rupture.

METHODS

The above hypothesis is tested on a retrospective, consecutively collected database of 204 patient-specific IAs. The first 119 cases are assigned to training and the remainder to testing dataset. $An$ is calculated based on the pulsatility index (PI) approximated either from the literature or solving an optimization problem (denoted as$\ \widehat {PI}$). Student's t-test and logistic regression (LR) are used for hypothesis testing and data fitting, respectively.

RESULTS

$An$ can significantly discriminate ruptured and unruptured status with 95% confidence level (P < .0001). $An$ (using PI) and $\widehat {An}$ (using $\widehat {PI}$) significantly predict the ruptured IAs (for training dataset $An\!:\ $AUC = 0.85, $\widehat {An}\!:\ $AUC = 0.90, and for testing dataset $An\!:\ $sensitivity = 94%, specificity = 33%, $\widehat {An}\!:\ $sensitivity = 93.1%, specificity = 52.85%).

CONCLUSION

$An > 1$ predicts ruptured status. Unlike traditional hemodynamic parameters such as wall shear stress and oscillatory shear index, $An$ has a physical threshold of one (does not depend on statistical analysis) and does not require time-consuming flow simulations. Therefore, $An$ is a simple, practical discriminator of IA rupture status.

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.

Identification of vortex structures in a cohort of 204 intracranial aneurysms

An intracranial aneurysm (IA) is a cerebrovascular pathology that can lead to death or disability if ruptured. Abnormal wall shear stress (WSS) has been associated with IA growth and rupture, but little is known about the underlying flow physics related to rupture-prone IAs. Previous studies, based on analysis of a few aneurysms or partial views of three-dimensional vortex structures, suggest that rupture is associated with complex vortical flow inside IAs. To further elucidate the relevance of vortical flow in aneurysm pathophysiology, we studied 204 patient IAs (56 ruptured and 148 unruptured). Using objective quantities to identify three-dimensional vortex structures, we investigated the characteristics associated with aneurysm rupture and if these features correlate with previously proposed WSS and morphological characteristics indicative of IA rupture. Based on the Q-criterion definition of a vortex, we quantified the degree of the aneurysmal region occupied by vortex structures using the volume vortex fraction (vVF) and the surface vortex fraction (sVF). Computational fluid dynamics simulations showed that the sVF, but not the vVF, discriminated ruptured from unruptured aneurysms. Furthermore, we found that the near-wall vortex structures co-localized with regions of inflow jet breakdown, and significantly correlated to previously proposed haemodynamic and morphologic characteristics of ruptured IAs.

Size and location correlations with higher rupture risk of intracranial aneurysms

AIM

The purpose of this study was to investigate the impact of size and location of the intracranial aneurysm on rupture probability.

MATERIAL AND METHODS

265 patients with diagnosis of intracranial aneurysms were admitted to the department from January 2012 to December 2013. The characteristic of aneurysm, such as median size, location, single and multiple aneurysms and presentation were retrospectively reviewed using cerebral angiography reports.

RESULTS

There were 265 patients admitted with the diagnosis of intracranial aneurysms, 193 with single and 72 with multiple aneurysms. Among them there were 197 women (74,3%) and 68 men (25,7%). The total number of aneurysms harbored by the patients with multiple aneurysms were 184. Among all patients 96 had ruptured aneurysm, most of them located at the AComA and the minority of ruptured aneurysms were located at the ICA and MCA, In most cases the size of ruptured aneurysm was smaller than 10 mm.

CONCLUSION

The location of an aneurysm is an important factor allowing to predict the rupture probability and to plan proper treatment. The size of the aneurysm is also very useful predictor especially correlated with the location but the impact on rupture probability still needs further examination.

The Incidence and Characteristics of Patients with Small Ruptured Aneurysms (<5 mm) in Subarachnoid Hemorrhage

OBJECTIVE

Small unruptured aneurysms (<5 mm) are known for their very low risk of rupture, and are recommended to be treated conservatively. However, we encounter many patients with small ruptured aneurysms in the clinical practice. We aimed to investigate the incidence and characteristics of patients with small ruptured aneurysms.

METHODS

We reviewed all patients admitted to our hospital with subarachnoid hemorrhage from January 2005 to December 2015. The patients were divided into two groups: those with aneurysms <5 mm (group S) and those with aneurysms ≥5 mm (group L). The patient's age and sex, size and location of aneurysms, and risk factors such as hypertension, diabetes, alcohol use, and smoking were compared between the two groups.

RESULTS

Eight-hundred eleven patients were diagnosed with ruptured aneurysms, and 337 (41.6%) were included in group S. The mean size of all aneurysms was 6.10±2.99 mm (range, 0.7-37.7); aneurysms with a diameter of 4-5 mm accounted for the largest subgroup of all aneurysms. Female sex was significantly associated with the incidence of small ruptured aneurysms (odds ratio [OR] 1.50, 95% confidence intervals [CI] 1.02-2.19, p=0.037). Despite female predominance in the incidence of small ruptured aneurysms, the proportion of small ruptured aneurysms in young (<50 years) men was high. In men, there were no significant differences regarding the location of the aneurysms between group S and group L (p=0.267), with the most frequent location being the anterior communicating artery (ACoA) in both group S (50.9%) and group L (51.4%). However, in women, there were significant differences regarding the location of the aneurysms between group S and group L (p=0.023), with the most frequent locations being the ACoA (33.0%) in group S, and the posterior communicating artery (30.6%) in group L. In women, two locations were significantly associated with small (<5 mm) ruptured aneurysms: the ACoA (OR 2.14, 95% CI 1.01-4.54, p=0.047) and anterior cerebral artery (OR 3.54, 95% CI 1.19-10.54, p=0.023). Multiplicity and smoking were significantly associated with large (≥5 mm) ruptured aneurysms in women. The use of alcohol was related to small ruptured aneurysms in men over 50 years of age (OR 2.23, 95% CI 1.03-4.84, p=0.042).

CONCLUSION

In this study, small (<5 mm) ruptured aneurysms exhibited different incidences by age, sex, location, and risk factors such as multiplicity, smoking, and alcohol use.

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.

Proposed Parent Vessel Geometry Based Classification of Anterior Communicating Artery-Located Aneurysms

BACKGROUND AND OBJECTIVES

The present study is focused on correlation of parent vessels and neck diameters with anterior communicating artery (AComA) aneurysmal depth and growth direction. The study principally aims to suggest a new classification of AComA-located aneurysms based on the physical characteristics of parent vessels.

METHODS

A retrospective analysis was performed of 155 patients with ruptured AComA-located aneurysms. The percentage of difference between both A1 arteries was measured on computed tomography angiography images and neck locations were determined. Accordingly, AComA-located aneurysms were classified into 2 groups. In both groups, A1 and A2 arteries and neck size diameters were measured and their relation with aneurysmal depth was studied. The aspect ratio was calculated.

RESULTS

Eleven patients in which the aneurysm neck originates from the AComA proper with almost equal A1s were classified as the true AComA aneurysm group whereas 144 patients in whom the aneurysm neck originates at the dominant A1 bifurcation into the AComA and A2 with the average difference between both A1s of about 84.44% were classified as the dominant A1-bifurcation group. There is significant correlation between aneurysmal depth and neck diameter in both groups (P ≤ 0.05, P < 0.001). The aspect ratio was calculated as equal to 1.166.

CONCLUSIONS

The dominant A1 bifurcation type is the most common type of AComA-located aneurysm. The present classification provides clinical value in understanding how AComA aneurysms grow and behave. It helps to understand the geometry of multilobulated aneurysms such as ruptured blebs locations during treatment procedures respecting the direction of the dominant A1 axis in group II. Multiple anatomic variations of this complex AComA area can clarify future subtypes of these 2 groups. Thus, further investigation of more patients is needed.

Size and location of ruptured intracranial aneurysms: consecutive series of 1993 hospital-admitted patients

OBJECTIVE Large consecutive series on the size and location of ruptured intracranial aneurysms (RIAs) are limited, and therefore it has been difficult to estimate population-wide effects of size-based treatment strategies of unruptured intracranial aneurysms. The authors' aim was to define the size and location of RIAs in patients diagnosed with subarachnoid hemorrhage due to aneurysm rupture in a high-volume academic center. METHODS Consecutive patients admitted to a large nonprofit academic hospital with saccular RIAs between 1995 and 2009 were identified, and the size, location, and multiplicity of RIAs were defined and reported by patient sex. RESULTS In the study cohort of 1993 patients (61% women) with saccular RIAs, the 4 most common locations of RIAs were the middle cerebral (32%), anterior communicating (32%), posterior communicating (14%), and pericallosal arteries (5%). However, proportional distribution of RIAs varied considerably by sex; for example, RIAs of the anterior communicating artery were more frequently found in men than in women. Anterior circulation RIAs accounted for 90% of all RIAs, and 30% of the patients had multiple intracranial aneurysms. The median size (measured as maximum diameter) of all RIAs was 7 mm (range 1-43 mm), but the size varied considerably by location. For example, RIAs of the ophthalmic artery had a median size of 11 mm, whereas the median size of RIAs of the pericallosal artery was 6 mm. Of all RIAs, 68% were smaller than 10 mm in maximum diameter. CONCLUSIONS In this large consecutive series of RIAs, 83% of all RIAs were found in 4 anterior circulation locations. The majority of RIAs were small, but the size and location varied considerably by sex. The presented data may be of help in defining effective prevention strategies.

Size and Location of Ruptured Intracranial Aneurysms: A 5-Year Clinical Survey

BACKGROUND

Prospective international cohort trials have suggested that incidental cerebral aneurysms with diameters less than 10 mm are unlikely to rupture. Consequently, small ruptured cerebral aneurysms should rarely be seen in clinical practice. To verify this theory, dimensions and locations of ruptured cerebral aneurysms were analyzed across the state of Tasmania, Australia.

METHODS

We retrospectively reviewed medical records and diagnostic tests of all patients admitted with ruptured cerebral aneurysms during a 5-year interval. Aneurysm location, maximum size, dome-to-neck ratio, volume, and presence of daughter sacs were determined by preoperative digital subtraction angiography or computed tomography angiography.

RESULTS

A total of 131 ruptured cerebral aneurysms were encountered and treated by microsurgical clipping (n = 59) or endovascular techniques (n = 72). The mean maximum aneurysm diameter was 6.4 ± 3.7 mm, dome-to-neck ratio 2 ± 0.8, aneurysm volume 156 ± 372 mm(3), and daughter sacs were present in 70 aneurysms (53.4%). The anterior communicating artery was the most common location (37.4%). Cumulative maximum diameters of ruptured aneurysms were ≤5 mm in 49%, ≤7 mm in 73%, and ≤10 mm in 90%.

CONCLUSIONS

Despite findings from prospective international cohort trials, small ruptured intracranial aneurysms are common in clinical practice. In consequence, it seems important to identify those patients with small but vulnerable unruptured aneurysms before conservative management is considered.

Sex differences in aneurysm morphologies and clinical outcomes in ruptured anterior communicating artery aneurysms: a retrospective study

OBJECTIVES

Ruptured anterior communicating artery (ACoA) aneurysms occur more frequently in men. The purpose of the study was to investigate sex difference in aneurysm morphologies and clinical outcomes in patients with ruptured ACoA aneurysms.

SETTING

A tertiary referral hospital.

PARTICIPANTS

A total of 574 consecutive patients with ACoA aneurysms were admitted to our hospital from December 2007 to February 2015. In all, 474 patients (257 men and 217 women) with ruptured ACoA aneurysms were included in the study.

MAIN OUTCOME MEASURES

Aneurysm morphologies were measured using computed tomographic angiography and clinical outcomes were measured with Glasgow coma score at discharge.

RESULTS

The aneurysm sizes (p=0.001), aneurysm heights (p=0.011), size ratios (p<0.001), flow angles (p=0.047) and vessel angles (p=0.046) were larger in the male patients than in the females. The female patients more often had larger vessel sizes (p=0.002). Multivariate logistic analysis revealed that significant differences in aneurysm morphologies between men and women were aneurysm size (OR 1.1, 95% CI 1.0 to 1.3; p=0.036), aneurysm height (OR 0.8, 95% CI 0. to 0.9; p=0.006) and size ratio (OR 1.4, 95% CI 0.5 to 1.7; p=0.001). There were no statistically significant differences in the outcomes between men and women (OR 1.0, 95% CI 0.6 to 1.7, p=0.857).

CONCLUSIONS

The men were independently associated with larger aneurysm sizes, greater aneurysm heights and larger size ratios. Sex was not a risk factor for poor outcome in patients with ruptured ACoA aneurysms.

The Frequency of Subarachnoid Hemorrhage from Very Small Cerebral Aneurysms (< 5 mm): A Population-Based Study

Background: The prevailing view amongst neurosurgeons is that the larger the aneurysm, the higher the chance of rupture. This implies that very small aneurysms rarely rupture. To investigate this theory, we conducted a cross-sectional hospital-based study of aneurysmal subarachnoid hemorrhage, with an emphasis on aneurysm size at the time of rupture.

Methods: We retrospectively reviewed hospital records and radiological tests of all patients admitted to Foothills Medical Center, Calgary, Alberta, with a ruptured saccular aneurysm from January 2008 to January 2012. The size of the dome and neck (in millimeters), the aspect ratio (aneurysm depth to aneurysm neck), and location of the aneurysms were determined using preoperative computed tomography angiography and digital subtraction angiography.

Findings: One hundred and twenty-three patients with a ruptured saccular aneurysm were identified. The average size of the dome, neck, and the aspect ratio was 6.6±4.4 mm (range: 1.5-26 mm), 3.1 mm, and 2.6±0.9, respectively. Forty-six patients (37%) had a ruptured aneurysm with dome size < 5 mm (range: 1.5-4.9 mm). For these small aneurysms, the average size of the dome, neck, and the aspect ratio was 3.9+1.1 mm, 1.6 mm, and 2.1+0.6, respectively. The anterior communicating artery was the most common location regardless of size.

Conclusion: Small aneurysms (< 5 mm) are a common cause of aneurysmal subarachnoid hemorrhage. When unruptured, looking for other risk factors for rupture is highly recommended before simply leaving them alone.

The impact of size and location on rupture of intracranial aneurysms

Objective:

For effective management of patients with unruptured intracranial aneurysms, prognostic criteria for rupture, of which aneurysm size, location, and multiplicity are key factors. The aim of this study is to determine the correlation between the aneurysm size, location, and multiplicity, and their effect on aneurysmal rupture.

Materials and Methods:

Eighty one patients with diagnosis of intracranial aneurysms were managed at our center from January 2008 through July 2011. The characteristics of aneurysms, such as size, location, multiplicity, and presentation were retrospectively reviewed from their charts and radiological findings.

Results:

Eighty one patients harboring 104 aneurysms were diagnosed, of them 45 were males (55.5%) and 36 were females (44.5%). Seventy-six patients (94%) presented with subarachnoid hemorrhage (SAH) due to ruptured aneurysm. Thirty-three patients who were presented with SAH (43%) had their ruptured aneurysm located at the anterior communicating artery with a mean size 5.8 mm. Most of the small (<7 mm) ruptured aneurysms were located at the anterior communicating artery, distal anterior cerebral arteries, posterior communicating arteries, and internal carotid artery bifurcation (51%, 13%, 11%, and 11%), respectively. There were 24 small unruptured aneurysms, 10 of them (42%) located at the middle cerebral arteries, while only 2 of them (8%) located at the anterior communicating artery.

Conclusions:

The aneurysm size and location play a substantial role in determining the risk of rupture. The most common location of rupture of small aneurysms was the anterior communicating artery, while the middle cerebral artery was the commonest site for small unrupured aneurysms.

Determining the critical size of intracranial aneurysm predisposing to subarachnoid hemorrhage in the Saudi population

Introduction:

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating event with a high rate of morbidity and mortality. With the improvement of diagnostic modalities and the adoption of different screening strategies, more aneurysms are being diagnosed prior to rupture. Based on large multi-center trials, size has become the most important determinant of treatment decisions. Unfortunately, these studies did not take into account the regional and racial variations, challenging the generalizability of their results.

Material and Methods:

We conducted a retrospective analysis on a series of 192 patients harboring 213 aneurysms.

Results:

The critical finding in our study is that the majority of patients presenting with SAH due to ruptured aneurysms are <10 mm in size.

Conclusion:

Decision to treatment of a given unruptured intracranial aneurysm should be individually assessed and not taken from general international literature as this may mistakenly apply factors from one population to another.

Bare platinum coils vs. HydroCoil in the treatment of unruptured intracranial aneurysms-A single center randomized controlled study

PURPOSE

The HydroCoil Embolic System (HES) was developed to improve aneurysm filling to provide superior occlusion efficacy, reduce retreatment rates and enhance long-term durability. We performed a randomized clinical trial to compare the effectiveness of bare platinum coils (BPC) vs. HES for unruptured intracranial aneurysms.

METHODS

Ninety-six patients underwent endovascular coiling of unruptured intracranial aneurysms. The aneurysms were randomized equally to receive BPC or HES. Immediate angiographic results, number of coils used and complications were evaluated and all cases had 12-month follow-up angiography.

RESULTS

Immediate angiographic results demonstrated that 84.0% of aneurysms treated with HES were completely occluded compared to 76.1% of aneurysms treated with BPC (p=0.3310). The mean number of coils utilized to fill the aneurysm was significantly lower in the HES arm (5.04 vs. 6.93). Additional adjunctive techniques were performed in 51.1% of all cases. There were seven patients (7.3%) with postoperative complications during the study period. The coil type used during the treatment did not demonstrate any significant differences on the overall recurrence rate (HES - 18.0%, BPC - 17.4%, p=0.9712). There was a statistically significant difference in the aneurysm size and the neck width between completely occluded aneurysms and aneurysms with residual flow in both immediate angiographic and mid-term follow-up.

CONCLUSIONS

Overall, aneurysm size and neck width are the main risk factors associated with aneurysm recurrence. HES compared to BPC required less total number of coils to provide a denser aneurysm filling. However, there were equivocal results with both devices, at the mid-term angiographic follow-up.

Anatomic risk factors for middle cerebral artery aneurysm rupture: computed tomography angiography study of 1009 consecutive patients

BACKGROUND

The middle cerebral artery (MCA) is the most frequent location for unruptured intracranial aneurysms. Controversy remains as to which unruptured MCA aneurysms should be treated prophylactically.

OBJECTIVE

To identify independent topographical and morphological variables that could predict increased rupture risk of MCA aneurysms.

METHODS

A retrospective analysis of computed tomography angiography data of 1009 consecutive patients with 1309 MCA aneurysms, referred between 2000 and 2009 to Helsinki University Hospital, was carried out. Morphological and topographical parameters examined for MCA aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, bottleneck factor, height-width ratio, location along the MCA, side, distance from the internal carotid artery bifurcation, and dome projection in axial and coronal computed tomography angiography views. Univariate and multivariate logistic regression analyses were performed to determine independent risk factors for rupture.

RESULTS

Of the 1309 MCA aneurysms, 69% were unruptured and 31% were ruptured. Most unruptured MCA aneurysms were smaller than 7 mm (78%), with a smooth wall (80%) and a height-width ratio of 1 (47%) and were located at the main bifurcation (57%). Ruptured MCA aneurysms, mostly 7 to 14 mm in size (55%), had an irregular wall (78%) and a height-width ratio greater than 1 (72%) and were located at the main bifurcation (77%). Thirty-eight percent of MCA bifurcation aneurysms, 74% of large aneurysms, 64% of aneurysms with an irregular wall, and 49% of aneurysms with a height-width ratio greater than 1 were ruptured.

CONCLUSION

Location at the main MCA bifurcation, wall irregularity, and less spherical geometry were independently associated with rupture of MCA aneurysms with a correlation with aneurysm size. artery.

Re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms

BACKGROUND

Unplanned re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms (UIAs) is sometimes required, but the underlying causes and rates of these procedures are seldom reported. This study retrospectively analyzed the causes of such re-explorations to identify methods for decreasing their necessity.

METHOD

From January 2000 to December 2011, 1,720 patients with a total of 1,938 UIAs underwent surgical treatment at our institution. From this cohort, 26 patients (1.5 %) with 38 UIAs required re-exploration. Clinical data, aneurysm characteristics, treatment methods, and the incidence and causes of re-exploration of the craniotomy were analyzed for these 26 patients.

RESULTS

Several causes of re-exploration were identified: compromised distal blood flow (eight patients, 0.47 %), hemorrhagic venous infarction (four patients, 0.23 %), brain retraction injury (three patients, 0.17 %), newly identified aneurysms (three patients, 0.17 %), bleeding from an incompletely clipped aneurysm (two patients, 0.12 %), epidural hematoma (two patients, 0.12 %), failed aneurysm clipping (two patients, 0.12 %) and other causes (two patients, 0.12 %). Annual re-exploration incidence rates ranged from 0 to 3.1 %. Annual incidence rates gradually decreased following the introduction of several intraoperative monitoring systems.

CONCLUSIONS

Precise surgical planning and careful operative techniques can reduce the incidence of unplanned re-exploration of the craniotomy. The introduction of various intraoperative monitoring systems can also contribute to a reduction in this incidence.

Size ratio: a morphological factor predictive of the rupture of cerebral aneurysm?

BACKGROUND

Determining factors predictive of the natural risk of rupture of cerebral aneurysms is difficult. We studied morphological factors associated with rupture in a study model of patients with mirror location intracranial aneurysms, one aneurysm that had ruptured and one that had not, each patient served as their own control attempting to eliminate confounding variables.

METHODS

We collected five one-dimensional measurements and four two-dimensional indices from three-dimensional rotational digital subtraction angiography images of patients in the proposed study model and explored their correlation with aneurysm rupture. Parameters were analyzed with a paired Student's t test for significance and significant parameters were further examined by multivariate conditional logistic regression analysis.

RESULTS

Fifty-two patients with 52 pairs of intracranial aneurysms in a mirror location were studied. The maximum perpendicular height, neck diameter, maximum width, maximum height, aspect ratio, size ratio, and bottleneck factor were significantly associated with ruptured aneurysms on bivariate analysis. A logistic regression analysis showed that only size ratio, which was defined as the ratio of the maximal height to parent artery average diameter, is independently correlated with ruptured intracranial aneurysms.

CONCLUSIONS

In a case-control study of patients with mirror location intracranial aneurysms, size ratio was identified as the unique morphological factor associate with the rupture of cerebral aneurysms.

Flow-induced wall mechanics of patient-specific aneurysmal cerebral arteries: Nonlinear isotropic versus anisotropic wall stress

Fluid-structure interaction simulations of three patient-specific models of cerebral aneurysms were carried out with the objective of quantifying the effects of non-Newtonian blood flow and the vessel mechanical behavior on the time-dependent fluid shear and normal stresses, and structural stress and stretch. The average wall shear stress at peak systole was found to be approximately one order of magnitude smaller than the shear stresses in the proximal communicating arteries, regardless of the shape or size of the aneurysms. Spatial distributions of oscillatory shear index were consistent with the reciprocal of wall shear stress distributions at peak systole for all aneurysm geometries, demonstrating that oscillatory shear index correlates inversely with wall shear at this time point in the cardiac cycle. An aneurysm wall modeled with an isotropic material resulted in an underestimation of both the maximum principal stress and stretch, compared to the anisotropic material model. For the three aneurysm geometries, anisotropic peak wall stresses were approximately 50% higher than for an isotropic material. Regardless of the constitutive material, the maximum stresses were consistently located at the aneurysm neck; stresses in the dome were 30% of those in the neck.

Size ratio can highly predict rupture risk in intracranial small (<5 mm) aneurysms

BACKGROUND AND PURPOSE

Management strategies for unruptured intracranial aneurysms (UIAs) are controversial. This study aimed to identify surrogate parameters that highly predict the rupture risk of small (<5 mm) UIAs.

METHODS

Radiological data were collected from 854 patients with aneurysmal subarachnoid hemorrhages who were enrolled in the Sapporo SAH Study. They had a total of 854 ruptured intracranial aneurysms and 180 UIAs. The size, aneurysm-to-vessel size ratio, and distribution were precisely compared between ruptured intracranial aneurysms and UIAs.

RESULTS

For all aneurysms, the size was significantly larger in ruptured intracranial aneurysms (7.0±1.3 mm) than in the UIAs (3.7±1.2 mm; P<0.001). Size ratio was also significantly higher in ruptured intracranial aneurysms (4.3±1.9) than in the UIAs (2.2±1.6; P<0.001). Multivariate logistic analysis showed that size and size ratio were correlated with aneurysm rupture. However, in small aneurysms, multivariate logistic regression revealed that only size ratio was associated with ruptured aneurysms (P=0.008; odds ratio, 9.1). There were no significant differences in size or aneurysm location. A receiver operating characteristic analysis was performed for size ratio in small aneurysms, and the threshold separating ruptured and unruptured groups was 3.12 and the area under the curve was 0.801.

CONCLUSIONS

This study revealed that the size ratio, and not the absolute size, may highly predict the risk of rupture in small UIAs. Size ratio measurements are very simple and provide useful information for determining treatment and follow-up strategies for patients with small UIAs.

Association of morphologic and demographic features of intracranial aneurysms with their rupture: a retrospective analysis

BACKGROUND

In spite of its common occurrence, the factors predictive of the rupture of intracranial aneurysms (IAs) remain poorly defined.

METHOD

A retrospective analysis of patients admitted with a primary diagnosis of cerebral aneurysm in a single institution was done. The factors studied were age, sex, size, site, side, multiplicity, neck type, aspect ratio, positive family history, smoking and drinking habits, and hypertension. The morphological parameters were evaluated for a total of 5,138 aneurysms obtained from the 2,347 patients. Factors found significant on univariate analysis were further tested on a multivariate model.

FINDINGS

We found 1,088 patients (46.36%) had at least a single aneurysmal rupture. Among the morphologic factors, size greater than 10 mm, right sidedness, aspect ratio greater than 1.6, deviated neck type, and multiplicity were found to be associated with higher incidences of rupture. Aneurysms on posterior communicating and middle cerebral arteries were found to be more prone to rupture. The demographic factors that were more linked with the ruptured aneurysms were positive family history, smoking, and hypertension.

CONCLUSIONS

Relevant cases should be started on intensive lifestyle modification, and extensive screening of those with a positive family history is highly warranted. All "at-risk" patients should be evaluated for early surgical intervention.

Assessment of the Risk of Rupture of Intracranial Aneurysms using Three-Dimensional Cerebral Digital Subtraction Angiography

The aim of this study was to develop an improved binary logistic regression model for predicting the risk of intracranial aneurysm rupture. A cohort of patients ( n = 37) with aneurysms underwent three-dimensional digital subtraction angiography examination to measure several morphological parameters of the aneurysm. The aspect ratio (height/neck size) and the size ratio (length/mean diameter of parent vessel) were also calculated. All the morphological parameters combined with the aneurysm location and the patient's baseline data were used to derive a backward binary logistic regression model. In order to validate the model, it was applied to another independent cohort of 19 patients with aneurysms. The model had sensitivity, specificity and accuracy of 84.6%, 66.7% and 78.9%, respectively. This binary logistic regression model of aneurysm rupture risk identified the status of an aneurysm with high accuracy and could form the basis of more complex models in the future.

Size ratio for clinical assessment of intracranial aneurysm rupture risk

OBJECTIVES

We previously used three-dimensional (3D) volumetric analysis to identify a novel intracranial aneurysm (IA) morphological metric, aneurysm-to-parent vessel size ratio (SR), which strongly correlated with aneurysm rupture. However, complex 3D analysis is not easily obtained, and ubiquitous IA risk assessment is traditionally performed with two-dimensional (2D) imaging, typically with size being the sole considered morphometric. Because only easily applicable 2D measurements will be of clinical value, we sought to investigate the correlation of SR determined from 2D angiography with IA rupture status.

METHODS

SR and traditional aspect ratio (AR) and aneurysm size parameters were measured in a retrospective cohort of 38 IA cases (16 ruptured) with 2D rotational angiographic images. These parameters were analysed for correlation with IA rupture status. Student's t-test or Wilcoxon rank-sum test was used for normally or non-normally distributed data respectively. Logistic regression was performed for independently statistically significant parameters to generate an effect size estimate (odds ratio). Area-under-the-curve (AUC) calculated from the receiver-operating-characteristic curve was additionally obtained for each index to describe differentiating capabilities.

RESULTS

Only SR achieved statistical significance (p=0.05) in Wilcoxon rank-sum test. Logistic regression generated an SR odds ratio of 3.52 (p=0.04; 95% confidence interval: 1.035-11.938) for every doubling of SR value. The AUC value of SR (0.688) was higher than that of AR (0.642) and size (0.585).

CONCLUSIONS

SR had the strongest correlation with IA rupture and was demonstrated to be a valuable parameter in 2D, where it can be easily obtained from angiographic images. When eventually evaluated in a prospective data set, SR may prove to be an important tool for aneurysm rupture-risk assessment.

Influence of intracranial aneurysm-to-parent vessel size ratio on hemodynamics and implication for rupture: results from a virtual experimental study

OBJECTIVE

The effectiveness of intracranial aneurysm (IA) size as a predictor for rupture has been debated. We recently performed a retrospective analysis of IA morphology and found that a new index, namely, aneurysm-to-parent vessel size ratio (SR), was strongly correlated with IA rupture, with 77% of ruptured IAs showing an SR of more than 2, and 83% of unruptured IAs showing an SR of 2 or less. As hemodynamics have been implicated in both IA development and rupture, we examine how varying SR influences intra-aneurysmal hemodynamics.

METHODS

One sidewall and 1 terminal IA were virtually reconstructed from patient 3-dimensional angiographic images. In 2 independent in silico experiments, the SR was varied from 1.0 to 3.5 by virtually changing either aneurysm size or vessel diameter while keeping the other parameter constant. Pulsatile computational fluid dynamics simulations were performed on each model for hemodynamics analysis.

RESULTS

Low SR (</=2) aneurysm morphology consistently demonstrated simple flow patterns with a single intra-aneurysmal vortex, whereas higher SR (>2) aneurysm morphology presented multiple vortices and complex flow patterns. The aneurysm luminal area that was exposed to low wall shear stress increased with increasing SR. Complex flow, multiple vortices, and low aneurysmal wall shear stress have been associated with ruptured IAs in previous studies.

CONCLUSION

Higher SR, irrespective of aneurysm type and absolute aneurysm or vessel size, gives rise to flow patterns typically observed in ruptured IAs. These results provide hemodynamic support for the existing correlation of SR with rupture risk.

Morphology parameters for intracranial aneurysm rupture risk assessment

OBJECTIVE

The aim of this study is to identify image-based morphological parameters that correlate with human intracranial aneurysm (IA) rupture.

METHODS

For 45 patients with terminal or sidewall saccular IAs (25 unruptured, 20 ruptured), three-dimensional geometries were evaluated for a range of morphological parameters. In addition to five previously studied parameters (aspect ratio, aneurysm size, ellipticity index, nonsphericity index, and undulation index), we defined three novel parameters incorporating the parent vessel geometry (vessel angle, aneurysm [inclination] angle, and [aneurysm-to-vessel] size ratio) and explored their correlation with aneurysm rupture. Parameters were analyzed with a two-tailed independent Student's t test for significance; significant parameters (P < 0.05) were further examined by multivariate logistic regression analysis. Additionally, receiver operating characteristic analyses were performed on each parameter.

RESULTS

Statistically significant differences were found between mean values in ruptured and unruptured groups for size ratio, undulation index, nonsphericity index, ellipticity index, aneurysm angle, and aspect ratio. Logistic regression analysis further revealed that size ratio (odds ratio, 1.41; 95% confidence interval, 1.03-1.92) and undulation index (odds ratio, 1.51; 95% confidence interval, 1.08-2.11) had the strongest independent correlation with ruptured IA. From the receiver operating characteristic analysis, size ratio and aneurysm angle had the highest area under the curve values of 0.83 and 0.85, respectively.

CONCLUSION

Size ratio and aneurysm angle are promising new morphological metrics for IA rupture risk assessment. Because these parameters account for vessel geometry, they may bridge the gap between morphological studies and more qualitative location-based studies.

What Is the Significance of a Large Number of Ruptured Aneurysms Smaller than 7 mm in Diameter?

OBJECTIVE

The International Study of Unruptured Intracranial Aneurysms (ISUIA) reported that the 5-year cumulative rupture rate of small unruptured aneurysms less than 7 mm in diameter is very low depending on the aneurysm's location. However, we have seen a large number of ruptured aneurysms less than 7 mm in clinical practice. The purpose of this study was to review our experience and to measure the size and location at which aneurysms ruptured in our patient population.

METHODS

We reviewed the characteristics of aneurysms, such as size and location, from the original angiograms of patients who were admitted to our hospital between January 2004 and December 2007. All aneurysms were treated surgically or through endovascular procedures.

RESULTS

Interventional or surgical treatment was given to a total of 889 patients, including 568 females and 321 males. At the time of our study, 627 cases were ruptured aneurysms and 262 cases were unruptured aneurysms. Of the ruptured cases, the mean diameter of the aneurysm was 6.28 mm. We found that 71.8% of ruptured aneurysms were smaller than 7 mm in diameter, and 87.9%, were smaller than 10 mm. Based on location, the data show that anterior communicating artery aneurysms most often presented with rupture sizes less than 7 mm (76.8%) and 10 mm (92.1%) in diameter. Most ruptured aneurysms were less than 7 mm in size, although recent studies have noted that small aneurysms are less likely to rupture.

CONCLUSION

Although the natural history of unruptured intracranial aneurysms remains controversial, the aneurysm size and location play a signigicant role in determining the risk of rupture. Larger sample sizes and a long term study are needed to reveal the natural history and the rupture risk of unruptured intracranial aneurysms because the size of most ruptured aneurysms was less than 7 mm in diameter in our series.

Size and location of ruptured intracranial aneurysms

OBJECTIVE

The aim of study was to review our patient population to determine whether there is a critical aneurysm size at which the incidence of rupture increases and whether there is a correlation between aneurysm size and location.

METHODS

We reviewed charts and radiological findings (computed tomography (CT) scans, angiograms, CT angiography, magnetic resonance angiography) for all patients operated on for intracranial aneurysms in our hospital between September 2002 and May 2004. Of the 336 aneurysms that were reviewed, measurements were obtained from angiograms for 239 ruptured aneurysms by a neuroradiologist at the time of diagnosis in our hospital.

RESULTS

There were 115 male and 221 female patients assessed in this study. The locations of aneurysms were the middle cerebral artery (MCA, 61), anterior communicating artery (ACoA, 66), posterior communicating artery (PCoA, 52), the top of the basilar artery (15), internal carotid artery (ICA) including the cavernous portion (13), anterior choroidal artery (AChA, 7), A1 segment of the anterior cerebral artery (3), A2 segment of the anterior cerebral artery (11), posterior inferior cerebellar artery (PICA, 8), superior cerebellar artery (SCA, 2), P2 segment of the posterior cerebral artery (1), and the vertebral artery (2). The mean diameter of aneurysms was 5.47+/-2.536 mm in anterior cerebral artery (ACA), 6.84+/-3.941 mm in ICA, 7.09+/-3.652 mm in MCA and 6.21+/-3.697 mm in vertebrobasilar artery. The ACA aneurysms were smaller than the MCA aneurysms. Aneurysms less than 6 mm in diameter included 37 (60.65%) in patients with aneurysms in the MCA, 43 (65.15%) in patients with aneurysms in the ACoA and 29 (55.76%) in patients with aneurysms in the PCoA.

CONCLUSION

Ruptured aneurysms in the ACA were smaller than those in the MCA. The most prevalent aneurysm size was 3-6 mm in the MCA (55.73%), 3-6 mm in the ACoA (57.57%) and 4-6 mm in the PCoA (42.30%). The more prevalent size of the aneurysm to treat may differ in accordance with the location of the aneurysm.

[Intracranial aneurysm, arteriovenous malformation, and carotid artery stenosis : endovascular prophylactic therapy]

The treatment of acute cerebrovascular disease plays a prominent role in clinical routine. However, prophylactic therapy of cerebrovascular disease including endovascular options is becoming more and more important. With particular regard to endovascular therapies, this summary deals with the natural course of cerebrovascular diseases and different treatment strategies for asymptomatic intracranial aneurysms, cerebral arteriovenous malformations, and extracranial carotid artery stenoses.

Predicting aneurysm rupture probabilities through the application of a computed tomography angiography–derived binary logistic regression model

Object

The goal of this study was to establish a biomathematical model to accurately predict the probability of aneurysm rupture. Biomathematical models incorporate various physical and dynamic phenomena that provide insight into why certain aneurysms grow or rupture. Prior studies have demonstrated that regression models may determine which parameters of an aneurysm contribute to rupture. In this study, the authors derived a modified binary logistic regression model and then validated it in a distinct cohort of patients to assess the model's stability.

Methods

Patients were examined with CT angiography. Three-dimensional reconstructions were generated and aneurysm height, width, and neck size were obtained in 2 orthogonal planes. Forward stepwise binary logistic regression was performed and then applied to a prospective cohort of 49 aneurysms in 37 patients (not included in the original derivation of the equation) to determine the log-odds of rupture for this aneurysm.

Results

A total of 279 aneurysms (156 ruptured and 123 unruptured) were observed in 217 patients. Four of 6 linear dimensions and the aspect ratio were significantly larger (each with p < 0.01) in ruptured aneurysms than unruptured aneurysms. Calculated volume and aneurysm location were correlated with rupture risk. Binary logistic regression applied to an independent prospective cohort demonstrated the model's stability, showing 83% sensitivity and 80% accuracy.

Conclusions

This binary logistic regression model of aneurysm rupture identified the status of an aneurysm with good accuracy. The use of this technique and its validation suggests that biomorphometric data and their relationships may be valuable in determining the status of an aneurysm.

Endovascular coil embolization of 435 small asymptomatic unruptured intracranial aneurysms: procedural morbidity and patient outcome

BACKGROUND AND PURPOSE

Whether treatment of small asymptomatic aneurysms is appropriate or not remains controversial. We performed a retrospective study on the procedural morbidity and mortality of coil embolization of small asymptomatic unruptured intracranial aneurysms (UIAs) to obtain a more generalized estimate of procedural risk.

MATERIALS AND METHODS

A total of 435 small (maximum diameter < or = 7 mm) asymptomatic UIAs in 370 patients were treated by coil embolization. Aneurysm sizes were determined by using 3D angiograms. We assessed procedure-related morbidity and mortality, immediate postprocedural angiographic results, short-term imaging follow-up results, and clinical outcomes.

RESULTS

Initial aneurysm occlusion was complete in 334 aneurysms, near complete in 78, and incomplete in 22. One internal carotid artery (ICA) aneurysm that ruptured during the procedure was treated with parent artery occlusion. Two hundred wide-neck aneurysms were coiled with the aid of various neck-remodeling techniques. The 44 procedure-related complications were the following: 24 thromboembolisms, 11 coil protrusions or prolapses into the parent vessel, 4 intraprocedural ruptures, 3 device-related complications, and 2 femoral-access complications. We had a total of 44 (10.1%) procedure-related complications with only 1 leading to persistent neurologic deficit. Procedure-related permanent morbidity and mortality were 0.27% (1/370) and 0%, respectively.

CONCLUSIONS

In this series of small unruptured asymptomatic aneurysms, endovascular treatment was achieved with good short-term angiographic outcome and low permanent neurologic impairment. The goal of this study was not to provide a conclusion about treatment guidelines for small UIA but rather to help guide future recommendations by presenting a more generalized estimate of endovascular treatment risk than is currently available.

Morbidity and mortality from surgical treatment of unruptured cerebral aneurysms at Research Institute for Brain and Blood Vessels-Akita

OBJECTIVE

Although the necessity of craniotomy for an unruptured cerebral aneurysm (UCA) is controversial, surgery is warranted if surgical risks are less than the risks of natural history. In this study, we investigated the need for craniotomy for UCAs on the basis of surgical risk.

METHODS

History of cerebrovascular disorders, aneurysm site and size, surgical complications, and clinical outcome were investigated in 368 patients (134 men, 234 women; ages 31-79 yr) who underwent craniotomy for treatment of UCA at our institute between 1993 and 2000.

RESULTS

We investigated 549 aneurysms. The mean size was 6.0 mm. Sites affected were the anterior cerebral artery (101 aneurysms), internal carotid artery (224 aneurysms), middle cerebral artery (201 aneurysms), and vertebrobasilar artery (23 aneurysms). The most common previous cerebrovascular disorders were subarachnoid hemorrhage (58 patients, 15.8%) and cerebral infarction (41 patients, 11.1%). Eight patients experienced permanent neurological deficits, for a total morbidity of 2.2%. One patient died, for a total mortality of 0.3%. For UCAs less than 10 mm in size, the morbidity was 0.6% and the mortality was 0%. For UCAs greater than 10 mm in size, the morbidity was 6.1% and the mortality was 1.2%. For UCAs in the anterior cerebral artery or middle cerebral artery, the morbidity was 0.3%. Temporary deficits were more frequently observed in patients older than 70 years of age than in patients 70 years of age or less.

CONCLUSION

Surgical treatment is a viable alternative for patients 70 years of age or less with UCAs less than 10 mm in size or UCAs located in the anterior cerebral artery or middle cerebral artery, because the surgical risk of treating such UCAs is sufficiently lower than the annual rupture rate of UCAs (2.3%) and the mental stress suffered by patients with untreated UCAs.

Outcome of Surgical Clipping of Unruptured Aneurysms as it Compares with a 10-Year Nonclipping Survival Period

OBJECTIVE

Recent studies on the natural history of unruptured intracranial aneurysms dictate that we reevaluate the risks and benefits of surgical intervention as it compares with the natural course. We analyzed the outcome of surgical clipping of a patient cohort with unruptured aneurysms as it compares with a 10 year nonclipping survival period on the basis of two previously published studies (International Study on Unruptured Intracranial Aneurysms and a study by Juvela et al. [36] from Helsinki).

METHODS

Data on 148 unruptured aneurysms in 116 consecutive surgically treated patients were prospectively recorded and retrospectively analyzed. The overall majority were diagnosed with cerebral angiography. Data analyzed included aneurysmal properties and clinical outcomes including surgical related mortalities and morbidities. The observed outcomes were compared with the expected outcome of a 10 year nonclipping survival period if the patient cohort was included in recently reported studies on unruptured aneurysms. More than 1 year follow-up was available in 93.1% (108) of patients and follow-up cerebral angiography was performed in 80% (93) of patients.

RESULTS

Mean age was 53.57 years. There were 25 (16.8%) small aneurysms (less than 7 mm), 70 (47.2%) aneurysms 7 to 12 mm in size, 41 (27.70%) large (13-24 mm), and 12 (8.10%) giant (>25 mm) aneurysms. Posterior circulation aneurysm comprised 13.51%. One hundred forty-three (96.62%) aneurysms were successfully clipped, and 3.37% were either wrapped or later coiled. Surgical-related mortality was 0.82% (1 patient because of air embolism). Surgical related permanent morbidity was 3.44% (4 patients) and transient surgical-related mild morbidities was 7.7% (9 patients). Immediate postsurgical good outcome (Glasgow Outcome Score = 4-5) was 87.93% (102 patients) and 95.68% in 3 months (111 patients). At 1 year, the modified Rankin scale scores were 0 to I = 102, II = 3, III = 2, IV = 1, and V = 0. Residual aneurysms were seen in none of the postoperative angiograms (93 patients). Using the chi method, the comparison of the expected to the observed mortality and morbidity revealed a statistically significant difference in the mortality in favor of surgical clipping (P = 0.034 when compared with the International Study on Unruptured Intracranial Aneurysms and P = 0.05 when compared with the Juvela et al. [36] study). There was no statistically significant difference in the permanent morbidity.

CONCLUSION

Studies on natural history of unruptured intracranial aneurysms suggest 10 year cumulative bleeding-related mortality and severe morbidity of no less than 7.5%. In our study, surgical clipping resulted in an 0.8% rate of mortality and 3.4% permanent morbidity. This suggests that surgical clipping has the potential of a superior outcome to the natural history of patients who have an estimated life expectancy of no less than 10 years.

Size and location of ruptured and unruptured intracranial aneurysms measured by 3-dimensional rotational angiography

OBJECTIVE

The aim of the study was to report about accurate size and location of a consecutive series of ruptured and unruptured aneurysms taking the complex 3-dimensional (3D) anatomy and parent vessel morphology into consideration by using the newly developed 3D rotational angiography (3D-RA).

METHODS

One hundred eighteen consecutive patients with 155 saccular intracranial aneurysms were included in the study and received 3D-RA reconstructions for measurement of maximal height and width of the aneurysmal sac. Statistical evaluation compared values for ruptured (n = 83) and unruptured (n = 72) aneurysms.

RESULTS

Mean height and width of unruptured aneurysms were 5.7 and 5.7 mm; of ruptured aneurysms, 6.7 and 6.1 mm (not significant, P = .7 for height and P = .9 for width). The majority of ruptured aneurysms, 81.9% and 59%, were smaller than 10 and 7 mm; likewise, 81.9% and 68.1% of unruptured aneurysms were smaller than 10 and 7 mm. The difference in frequency of small (<10/<7 mm) aneurysms between unruptured and ruptured aneurysms was not significant (P = 1.0 and .32, respectively). The majority (69.4%) of small ruptured aneurysms (<7 mm) were located in the anterior circulation. Most ruptured aneurysms were in the size group 4 to 6 mm in height and 2 to 4 mm in width, and a critical threshold size for aneurysm rupture could not be identified.

CONCLUSIONS

An automated calibration procedure applied to all images and excellent visualization of aneurysm and parent vessel morphology using 3D-RA allow accurate size measurement of intracranial aneurysms which may be smaller than previously thought. Small aneurysm (<7 mm), also in the anterior circulation, should be carefully evaluated for treatment.

ELANA: Excimer Laser-Assisted Nonocclusive Anastomosis for extracranial-to-intracranial and intracranial-to-intracranial bypass: a review

ELANA, excimer laser-assisted nonocclusive anastomosis, is a technique using an excimer laser/catheter system for intracranial bypass surgery of the brain. The technique has been developed over the past 12 years by Tulleken and colleagues at UMC Utrecht in The Netherlands for treatment of primarily untreatable giant aneurysms. We review here the emergence of transplanted conduit bypass as a valuable technique for managing these lesions and the subsequent development of ELANA bypass. The ELANA technique allows the operating surgeon to perform an extracranial-to-intracranial or intracranial-to-intracranial bypass using a transplanted large caliber conduit without occlusion of the recipient artery, thus eliminating intraoperative ischemic insult related to temporary occlusion time. We describe the ELANA technique, illustrate it with intraoperative photos, and review the relevant literature. ELANA is shown to be safe; we discuss its advantages over conventional techniques.

Parameterization of the shape of intracranial saccular aneurysms using Legendre polynomials

Our recent studies of the nonlinear mechanics of saccular aneurysms suggest that it is unlikely that these lesions enlarge or rupture via material (limit point) or dynamic (resonance) instabilities. Rather, there is a growing body of evidence from both vascular biology and biomechanical analyses that implicate mechanosensitive growth and remodeling processes. There is, therefore, a pressing need to quantify regional multiaxial wall stresses which, because of the membrane-like behavior of many aneurysms, necessitates better information on the applied loads and regional surface curvatures. Herein, we present and illustrate a method whereby regional curvatures can be estimated easily for sub-classes of human aneurysms based on clinically available data from magnetic resonance angiography (MRA). Whereas Legendre polynomials are used to illustrate this approach, different functions may prove useful for different sub-classes of lesions.