Morphological parameters associated with ruptured posterior communicating aneurysms

A Systematic Review and Meta-Analysis of 3-Dimensional Morphometric Parameters for Cerebral Aneurysms

BACKGROUND

Imaging modalities with increased spatial resolution have allowed for more precise quantification of cerebral aneurysm shape in 3-dimensional (3D) space. We conducted a systematic review and meta-analysis to assess the correlation of individual 3D morphometric measures with cerebral aneurysm rupture status.

METHODS

Two independent reviewers performed a PRISMA (preferred reporting items of systematic reviews and meta-analysis)-guided literature search to identify articles reporting the association between 3D morphometric measures of intracranial aneurysms and rupture status.

RESULTS

A total of 15,122 articles were identified. After screening, 39 studies were included. We identified 17 3D morphometric measures, with 11 eligible for the meta-analysis. The meta-analysis showed a significant association with rupture status for the following measures: nonsphericity index (standardized mean difference [SMD], 0.66; 95% confidence interval [CI], 0.53-0.79; P < 0.0001; I2 = 55.2%), undulation index (SMD, 0.55; 95% CI, 0.26-0.85; P = 0.0017; I2 = 68.1%), ellipticity index (SMD, 0.53; 95% CI, 0.29-0.77; P = 0.0005; I2 = 70.8%), volume (SMD, 0.18; 95% CI, 0.02-0.35; P = 0.0320; I2 = 82.3%), volume/ostium ratio (SMD, 0.43; 95% CI, 0.16-0.71; P = 0.0075; I2 = 90.4%), elongation (SMD, -0.94; 95% CI, -1.12 to -0.76; P = 0.0005; I2 = 0%), flatness (SMD, -0.87; 95% CI, -1.04 to -0.71; P = 0.0005; I2 = 0%), and sphericity (SMD, -0.62; 95% CI, -1.06 to -0.17; P = 0.0215; I2 = 67.9%). A significant risk of publication bias was estimated for the ellipticity index (P = 0.0360) and volume (P = 0.0030).

CONCLUSIONS

Based on the results of a meta-analysis containing 39 studies, the nonsphericity index, undulation index, elongation, flatness, and sphericity demonstrated the most consistent correlation with rupture status.

Basilar tip morphology: impact on mechanical thrombectomy for acute distal basilar artery occlusion

BACKGROUND

The morphology of the basilar artery tip (BAT) varies between patients. The morphologic anatomy of the BAT could affect the efficacy of mechanical thrombectomy (MT).

METHODS

108 patients with acute distal basilar artery occlusion (dBAO) who underwent MT from January 2013 to December 2021 were retrospectively analyzed. These patients were divided into two groups based on their BAT morphology: those with symmetrical cranial or caudal fusion of the BAT (symmetric group) and those with asymmetrical fusion of the BAT (asymmetric group). Morphological variables and angiographic and clinical outcomes were compared between the two groups.

RESULTS

Of the 108 enrolled patients, 42 were in the asymmetric group. Compared with the symmetric group, the asymmetric group had significantly larger BAT diameter (mean 3.5±1.0 mm vs 4.3±1.1 mm, P=0.001) and basilar artery tip/trunk ratio (1.2±0.2 vs 1.7±0.2, P<0.001). The asymmetric group showed a significantly lower rate of complete reperfusion (71.2% vs 40.5%, P=0.002) and first pass effect (FPE) (51.5% vs 21.4%, P=0.002) than the symmetric group. The BAT asymmetry was an independent predictor of failed FPE (OR 0.299, 95% CI 0.098 to 0.918, P=0.035) and failed complete reperfusion (OR 0.275, 95% CI 0.087 to 0.873, P=0.029).

CONCLUSIONS

The efficacy of MT for dBAO differs according to the anatomic morphology of the BAT. The asymmetric BAT was frequently encountered in dBAO patients and was independently associated with a reduced likelihood of complete reperfusion and FPE.

Impact of Morphological Factors on the Future Growth of Unruptured Posterior Communicating Artery Aneurysms

BACKGROUND

No previous study has established the factors associated with intracranial aneurysm growth using imaging data obtained before the appearance of morphological changes. Therefore, we investigated the factors related to future aneurysm growth in posterior communicating artery (Pcom) aneurysms.

METHODS

Using a longitudinal database of intracranial aneurysm cases, we reviewed the findings for consecutive patients with unruptured Pcom aneurysms admitted to our institute from 2012 to 2021. Magnetic resonance images obtained over time were used to evaluate aneurysm growth. Aneurysms showing growth over time (group G) and unchanged aneurysms (group U) were compared in terms of background data and morphological factors.

RESULTS

93 Pcom aneurysms (group G: 25 aneurysms, 25%; group U: 68 aneurysms, 75%) were eligible for the present study. Six aneurysm rupture events occurred in group G (24%). Among morphological factors, Pcom diameter (1.2 ± 0.3 mm vs. 0.8 ± 0.7 mm, P < 0.01), bleb formation (group G: 39% vs. group U: 10%; odds ratio, 5.6; P = 0.01), and the lateral projection of the dome (group G: 52% vs. group U: 13%; odds ratio, 3.2; P = 0.023) were significantly different between the 2 groups. The sensitivity and specificity of a cutoff Pcom diameter of 0.73 mm for predicting enlargement were 96% and 53%, respectively.

CONCLUSIONS

Pcom diameter, bleb formation, and lateral dome projection were associated with growth of Pcom aneurysms. Aneurysms with these risk factors require careful follow-up imaging, which may facilitate early detection of aneurysm growth and prevention of rupture through therapeutic interventions.

Radiologic assessment of rupture risk in small (<5 mm) posterior communicating artery aneurysms

Although previous studies have investigated the predictors of posterior communicating artery (PCoA) aneurysm rupture with clinical and radiologic parameters, the accessibility of "small PCoA aneurysms (<5 mm)" has rarely been reported. Here, we designed a study to identify the factors which are thought to be risky and prone to rupture in small PCoA aneurysms (<5 mm).A total of 114 patients diagnosed with PCoA aneurysm under 5 mm in size on digital subtraction angiography were retrospectively enrolled and divided into ruptured (n = 51) and unruptured (n = 63) groups. Clinical variables were reviewed, and 10 radiologic parameters were obtained, including maximum diameter, height, width, neck width, aspect ratio, dome-to-neck ratio, bleb formation, size ratio, presence of fetal-type PCoA, and inflow angle. Statistical analyses were conducted to compare the groups (ruptured vs unruptured) and identify the risk factors for rupture.High rupture rate of small PCoA aneurysm is noted (51/114, 44.7%). In the comparison analysis, parameters of size ratio (P = .045), aspect ratio (P = .001), and bleb formation (P = .015) were significantly different between the 2 groups. In the regression model, the aspect ratio (P = .045) and bleb formation (P = .004) were significantly associated with the rupture of aneurysm.In respect of small (<5 mm) PCoA aneurysms of our cohort, morphologic parameters of "bleb formation" and "a high aspect ratio" are present more often in ruptured aneurysms as compared to unruptured aneurysms.

Morphological variables associated with ruptured basilar tip aneurysms

Morphological factors of intracranial aneurysms and the surrounding vasculature could affect aneurysm rupture risk in a location specific manner. Our goal was to identify image-based morphological parameters that correlated with ruptured basilar tip aneurysms. Three-dimensional morphological parameters obtained from CT-angiography (CTA) or digital subtraction angiography (DSA) from 200 patients with basilar tip aneurysms diagnosed at the Brigham and Women's Hospital and Massachusetts General Hospital between 1990 and 2016 were evaluated. We examined aneurysm wall irregularity, the presence of daughter domes, hypoplastic, aplastic or fetal PCoAs, vertebral dominance, maximum height, perpendicular height, width, neck diameter, aspect and size ratio, height/width ratio, and diameters and angles of surrounding parent and daughter vessels. Univariable and multivariable statistical analyses were performed to determine statistical significance. In multivariable analysis, presence of a daughter dome, aspect ratio, and larger flow angle were significantly associated with rupture status. We also introduced two new variables, diameter size ratio and parent-daughter angle ratio, which were both significantly inversely associated with ruptured basilar tip aneurysms. Notably, multivariable analyses also showed that larger diameter size ratio was associated with higher Hunt-Hess score while smaller flow angle was associated with higher Fisher grade. These easily measurable parameters, including a new parameter that is unlikely to be affected by the formation of the aneurysm, could aid in screening strategies in high-risk patients with basilar tip aneurysms. One should note, however, that the changes in parameters related to aneurysm morphology may be secondary to aneurysm rupture rather than causal.

Age and morphology of posterior communicating artery aneurysms

Risk of intracranial aneurysm rupture could be affected by geometric features of intracranial aneurysms and the surrounding vasculature in a location specific manner. Our goal is to investigate the morphological characteristics associated with ruptured posterior communicating artery (PCoA) aneurysms, as well as patient factors associated with the morphological parameters. Three-dimensional morphological parameters in 409 patients with 432 PCoA aneurysms diagnosed at the Brigham and Women’s Hospital and Massachusetts General Hospital between 1990 and 2016 who had available CT angiography (CTA) or digital subtraction angiography (DSA) were evaluated. Morphological parameters examined included aneurysm wall irregularity, presence of a daughter dome, presence of hypoplastic or aplastic A1 arteries and hypoplastic or fetal PCoA, perpendicular height, width, neck diameter, aspect and size ratio, height/width ratio, and diameters and angles of surrounding parent and daughter vessels. Univariable and multivariable statistical analyses were performed to determine the association of morphological parameters with rupture of PCoA aneurysms. Additional analyses were performed to determine the association of patient factors with the morphological parameters. Irregular, multilobed PCoA aneurysms with larger height/width ratios and larger flow angles were associated with ruptured PCoA aneurysms, whereas perpendicular height was inversely associated with rupture in a multivariable model. Older age was associated with lower aspect ratio, with a trend towards lower height/width ratio and smaller flow angle, features that are associated with a lower rupture risk. Morphological parameters are easy to assess and could help in risk stratification in patients with unruptured PCoA aneurysms. PCoA aneurysms diagnosed at older age have morphological features associated with lower risk.

Are Fetal-Type Posterior Cerebral Arteries Associated With an Increased Risk of Posterior Communicating Artery Aneurysms?

BACKGROUND

Fetal-type posterior cerebral arteries (F-PCAs) might result in alterations in hemodynamic flow patterns and may predispose an individual to an increased risk of posterior communicating artery aneurysms (PCoAAs).

OBJECTIVE

To determine the association between PCoAAs and the presence of ipsilateral F-PCAs.

METHODS

We retrospectively reviewed the radiographic findings from 185 patients harboring 199 PCoAAs that were treated at our institution between 2005 and 2015. Our study population consisted of 4 cohorts: (A) patients with 171 internal carotid arteries (ICAs) harboring unilateral PCoAAs; (B) 171 unaffected ICAs in the same patients from the first group; (C) 28 ICAs of 14 patients with bilateral PCoAAs; and (D) 180 ICAs of 90 patients with aneurysms in other locations. We then determined the presence of ipsilateral F-PCAs and recorded all aneurysm characteristics.

RESULTS

Group A had the highest prevalence of F-PCAs (42%) compared to 19% in group B, 3% in group C, and 14% in group D (odds ratio A : B = 3.041; A : C = 19.626; and A : D = 4.308; P < .001). PCoAAs were associated with larger diameters of the posterior communicating arteries (median value 1.05 vs 0.86 mm; P = .001). The presence of F-PCAs was associated with larger sizes of the aneurysm necks (median value 3.3 vs 3.0 mm; P = .02).

CONCLUSION

PCoAAs were associated with a higher prevalence of ipsilateral F-PCAs. This variant was associated with larger sizes of the aneurysm necks but was not associated with the sizes of the aneurysm domes or with their rupture statuses.

Size of ruptured intracranial aneurysms: a systematic review and meta-analysis

BACKGROUND

There is wide variation in the reported size of ruptured intracranial aneurysms and methods of size estimation. There is widespread belief that small aneurysms < 7 mm do not rupture. Therefore, we performed a systematic review and meta-analysis of the literature to determine the size of ruptured aneurysms according to aneurysm locations and methods of size estimation.

METHODS

We searched PubMed, Cochrane, CINAHL, and EMBASE databases using a combination of Medical Subject Headings (MeSH) terms. We included articles that reported mean aneurysm size in consecutive series of ruptured intracranial. We excluded studies limited to a specific aneurysm location or type. The random-effects model was used to calculate overall mean size and location-specific mean size. We performed meta-regression to explain observed heterogeneity and variation in reported size.

RESULTS

The systematic review included 36 studies and 12,609 ruptured intracranial aneurysms. Overall mean aneurysm size was 7.0 mm (95% confidence interval [CI 6.2-7.4]). Pooled mean size varied with location. Overall mean size of 2145 ruptured anterior circulation aneurysms was 6.0 mm (95% CI 5.6-6.4, residual I² = 86%). Overall mean size of 743 ruptured posterior circulation aneurysms was 6.2 mm (95% CI 5.3-7.0, residual I² = 93%). Meta-regression identified aneurysm location and definition of size (i.e., maximum dimension vs. aneurysm height) as significant determinants of aneurysm size reported in the studies.

CONCLUSIONS

The mean size of ruptured aneurysms in most studies was approximately 7 mm. The general wisdom that aneurysms of this size do not rupture is incorrect. Location and size definition were significant determinants of aneurysm size.

Morphological Variables Associated With Ruptured Middle Cerebral Artery Aneurysms

BACKGROUND

Geometric factors of intracranial aneurysms and surrounding vasculature could affect the risk of aneurysm rupture. However, large-scale assessments of morphological parameters correlated with intracranial aneurysm rupture in a location-specific manner are scarce.

OBJECTIVE

To investigate the morphological characteristics associated with ruptured middle cerebral artery (MCA) aneurysms.

METHODS

Five hundred sixty-one patients with 638 MCA aneurysms diagnosed between 1990 and 2016 who had available computed tomography angiography (CTA) were included in this study. CTAs were evaluated using the Vitrea Advanced Visualization software for 3-dimensional (3D) reconstruction. Morphological parameters examined in each model included aneurysm projection, wall irregularity, presence of a daughter dome, presence of hypoplastic or aplastic A1 arteries and hypoplastic or fetal posterior communicating arteries (PCoA), aneurysm height and width, neck diameter, bottleneck factor, aspect and size ratio, height/width ratio, and diameters and angles of surrounding parent and daughter vessels. Univariable and multivariable statistical analyses were performed to determine the association of morphological characteristics with rupture of MCA aneurysms. Logistic regression was used to build a predictive MCA score.

RESULTS

Greater bottleneck and size ratio, and irregular, multilobed, temporally projecting MCA aneurysms are associated with higher rupture risk, whereas higher M1/M2 ratio, larger width, and the presence of an ipsilateral or bilateral hypoplastic PCoA were inversely associated with rupture. The MCA score had good predictive capacity with area under the receiver operating curve = 0.88.

CONCLUSION

These practical morphological parameters specific to MCA aneurysms are easy to assess when examining 3D reconstructions of unruptured aneurysms and could aid in risk evaluation in these patients.

Risk factor analysis of recanalization and retreatment for patients with endovascular treatment of internal carotid artery bifurcation aneurysms

PURPOSE

Only a few reports of internal carotid artery (ICA) bifurcation aneurysms using the endovascular technique have been published in the current literature. The purpose of this study was to assess how multiple risk factors including angioarchitectural features of ICA bifurcation characteristics may have influenced aneurysmal rupture, recanalization, and retreatment.

METHODS

Fifty-one patients with 52 ICA bifurcation aneurysms treated with endovascular coiling between July 2003 and July 2015 were retrospectively analyzed. The patients' clinical records, endovascular reports, and clinical and angiographic outcomes were reviewed. We also evaluated risk factors for recanalization and retreatment, including the angioarchitectural anatomy.

RESULTS

The clinical outcomes were observed to be satisfactory in 49 patients (96.0%) and unfavorable in 2 patients (4.0%). The risk factor for aneurysmal rupture was young age (P = 0.024). Symptomatic complications due to thromboembolism occurred in 1.9% of cases; no patients suffered a fatal complication. Eleven of 52 ICA bifurcation aneurysms (21.2%) were recanalized within an average of 54.3 ± 33.5 months of follow-up. Among the aneurysms, 4 (7.7%) underwent recoiling. Multivariate analysis showed that ruptured aneurysms (P = 0.006) and a lower packing density (P = 0.048) were risk factors for recanalization. A lower packing density was the only risk factor for retreatment (P = 0.019).

CONCLUSION

Endovascular treatment of ICA bifurcation aneurysms is considered safe and acceptable. This study showed that the ICA bifurcation aneurysms ruptured more frequently at a younger age. A higher packing density has been shown to reduce major recanalization and retreatment.

CTA analysis and assessment of morphological factors related to rupture in 413 posterior communicating artery aneurysms

Posterior communicating artery (PcomA) aneurysms are frequently encountered, but there are few publications on their morphology. A growing number of aneurysms are incidental findings, which makes evaluation of rupture risk important. Our goal was to identify morphological features and anatomical variants associated with PComA aneurysms and to assess parameters related to rupture. We studied CT angiographies of 391 consecutive patients treated between 2000 and 2014 at a single institution. We determined clinically important morphological parameters and performed univariate and multivariate analysis. There were a total of 413 PComA aneurysms: 258 (62%) were ruptured and 155 (38%) unruptured. Ruptured PComA aneurysms had the potential to cause severe bleeding with IVH and/or temporal ICH (n = 170, 66% of ruptured). The main types of PComA origin were classified as follows: (1) separate (32%), (2) side by side (21%) and (3) a joint neck with the aneurysm (6%). After the multivariate logistic regression, the morphological parameters related to PComA aneurysm rupture were an irregular aneurysm dome, neck diameter, and aspect ratio >1.5. The most marked morphological features of the PComA aneurysms were: saccular nature (99%), infero-posterior dome orientation (42%), infrequency of large or giant aneurysms (4%), narrow neck compared to the aneurysm size, PComA originating directly from the aneurysm neck or the dome (28%), and fetal or dominant PComA on the side of the aneurysm (35%). There were location-related parameters that were more strongly associated with PComA aneurysm rupture than aneurysm size: an irregular aneurysm dome, larger diameter of the aneurysm neck and aspect ratio >1.5.

Reproducibility of image-based computational models of intracranial aneurysm: a comparison between 3D rotational angiography, CT angiography and MR angiography

BACKGROUND

Reconstruction of patient-specific biomechanical model of intracranial aneurysm has been based on different imaging modalities. However, different imaging techniques may influence the model geometry and the computational fluid dynamics (CFD) simulation. The aim of this study is to evaluate the differences of the morphological and hemodynamic parameters in the computational models reconstructed from computed tomography angiography (CTA), magnetic resonance angiography (MRA) and 3D rotational angiography (3DRA).

METHODS

Ten patients with cerebral aneurysms were enrolled in the study. MRA, CTA and 3DRA were performed on all patients. For each patient, three patient-specific models were reconstructed respectively based on the three sets of imaging data of the patient. CFD simulations were performed on each model. Model geometry and hemodynamic parameters were compared between the three models.

RESULTS

In terms of morphological parameters, by comparing CTA based models (CM) and 3DRA based models (DM) which were treated as the "standard models", the aspect ratio had the minimum difference (Δ = 8.3 ± 1.72 %, P = 0.953) and the surface distance was 0.25 ± 0.07 mm. Meanwhile, by comparing MRA based models (MM) and DM, the size had the minimum difference (Δ = 6.6 ± 1.85 %, P = 0.683) and the surface distance was 0.36 ± 0.1 mm. In respect of hemodynamic parameters, all three models showed a similar distribution: low average WSS at the sack, high OSI at the body and high average WSSG at the neck. However, there was a large variation in the average WSS (Δ = 34 ± 5.13 % for CM, Δ = 40.6 ± 9.21 % for MM).

CONCLUSION

CTA and MRA have no significant differences in reproducing intracranial aneurysm geometry. The CFD results suggests there might be some significant differences in hemodynamic parameters between the three imaging-based models and this needs to be considered when interpreting the CFD results of different imaging-based models. If we only need to study the main flow patterns, three types of image-based model might be all suitable for patient-specific computational modeling studies.

Carotid siphon morphology: Is it associated with posterior communicating aneurysms?

BACKGROUND AND PURPOSE

Posterior communicating artery (PComA) aneurysm seems to behave uniquely compared with other intracranial aneurysms at different locations. The association between the morphology of the carotid siphon and PComA aneurysms is not well known. This study aimed to investigate whether the anatomical characteristics of the carotid siphon are associated with the formation and rupture of PComA aneurysms.

METHODS

One hundred and thirty-two patients were retrospectively reviewed in a monocentric case-control study. Sixty-seven consecutive patients with PComA aneurysms were included in the case group, and 65 patients with anterior circulation aneurysm situated in other intracranial locations were included in the control group, matched by age and sex. Morphological characteristics of the carotid siphon were analyzed using angiography images. A univariate analysis was used to investigate the association between the morphological characteristics and the formation of PComA aneurysms. Furthermore, a subgroup analysis within the case group compared ruptured and non-ruptured PComA aneurysms.

RESULTS

Patients with PComA aneurysm had a significantly (1.31 ± 0.70 vs. 0.82 ± 0.46; P < 0.001) larger PComA. No association was observed between the morphological characteristics of the carotid siphon and the presence of a PComA aneurysm. Likewise, subgroup analysis showed no significant association between morphological characteristics of the carotid siphon and aneurysm rupture.

CONCLUSIONS

This case-control study shows that the carotid siphon morphology seems not to be related to PComA aneurysm formation or rupture.

Morphological and Hemodynamic Discriminators for Rupture Status in Posterior Communicating Artery Aneurysms

Background and Purpose

The conflicting findings of previous morphological and hemodynamic studies on intracranial aneurysm rupture may be caused by the relatively small sample sizes and the variation in location of the patient-specific aneurysm models. We aimed to determine the discriminators for aneurysm rupture status by focusing on only posterior communicating artery (PCoA) aneurysms.

Materials and Methods

In 129 PCoA aneurysms (85 ruptured, 44 unruptured), clinical, morphological and hemodynamic characteristics were compared between the ruptured and unruptured cases. Multivariate logistic regression analysis was performed to determine the discriminators for rupture status of PCoA aneurysms.

Results

While univariate analyses showed that the size of aneurysm dome, aspect ratio (AR), size ratio (SR), dome-to-neck ratio (DN), inflow angle (IA), normalized wall shear stress (NWSS) and percentage of low wall shear stress area (LSA) were significantly associated with PCoA aneurysm rupture status. With multivariate analyses, significance was only retained for higher IA (OR = 1.539, p < 0.001) and LSA (OR = 1.393, p = 0.041).

Conclusions

Hemodynamics and morphology were related to rupture status of intracranial aneurysms. Higher IA and LSA were identified as discriminators for rupture status of PCoA aneurysms.

Smoking and Intracranial Aneurysm Morphology

BACKGROUND

Smoking is a well-known independent risk factor for both aneurysm formation and rupture. There is mounting evidence that aneurysm morphology beyond size can have a significant role in aneurysm formation and rupture risk by its effects on aneurysmal hemodynamics.

OBJECTIVE

To study the variation in aneurysm morphology between smokers and nonsmokers and delineate how changes in these factors might affect aneurysm formation and rupture.

METHODS

We generated 3-dimensional models of aneurysms and their surrounding vasculature by analyzing preoperative computed tomography angiograms with Slicer software. We then examined the association between smoking status and intrinsic, transitional, and extrinsic aspects of aneurysm morphology in both univariate and multivariate statistical analyses.

RESULTS

From 2005 to 2013, 199 cerebral aneurysms in never smokers and current smokers were evaluated/treated at a single institution with available computed tomography angiograms (102 in never smokers and 97 in current smokers). Multivariate analysis of current smokers vs never smokers demonstrated that aneurysms in current smokers were significantly associated with multiple aneurysms (odds ratio [OR]: 2.15, P = .03), larger daughter vessel diameters (OR: 3.13, P = .01), larger size ratio (OR: 1.78, P = .01), and location at the basilar apex (OR: 6.26, P = .02).

CONCLUSION

The differences in aneurysm morphology between smoking and nonsmoking patient populations may elucidate the effects of smoking on aneurysm formation and eventual rupture. We identified several aspects of aneurysm morphology significantly associated with smoking status that may provide the morphological basis for how smoking leads to increased aneurysm rupture.

Clinical, morphological, and hemodynamic independent characteristic factors for rupture of posterior communicating artery aneurysms

OBJECTIVE

To identify clinical, morphological, and hemodynamic independent characteristic factors that discriminate posterior communicating artery (PCoA) aneurysm rupture status.

METHODS

173 patients with single PCoA aneurysms (108 ruptured, 65 unruptured) between January 2012 and June 2014 were retrospectively collected. Patient-specific models based on their three-dimensional digital subtraction angiography images were constructed and analyzed by a computational fluid dynamic method. All variables were analyzed by univariate analysis and multivariate logistic regression analysis.

RESULTS

Two clinical factors (younger age and atherosclerosis), three morphological factors (higher aspect ratio, bifurcation type, and irregular shape), and six hemodynamic factors (lower mean and minimum wall shear stress, higher oscillatory shear index, a greater portion of area under low wall shear stress, unstable and complex flow pattern) were significantly associated with PCoA aneurysm rupture. Independent factors characterizing the rupture status were identified as age (OR 0.956, p=0.015), irregular shape (OR 6.709, p<0.001), and minimum wall shear stress (OR 0.001, p=0.038).

CONCLUSIONS

We combined clinical, morphological, and hemodynamic characteristics analysis and found the three strongest independent factors for PCoA aneurysm rupture were younger age, irregular shape, and low minimum wall shear stress. This may be useful for guiding risk assessments and subsequent treatment decisions for PCoA aneurysms.

Intrinsic, Transitional, and Extrinsic Morphological Factors Associated With Rupture of Intracranial Aneurysms

BACKGROUND

As diagnosis and treatment of unruptured intracranial aneurysms continues to increase, management principles remain largely based on size. This is despite mounting evidence that aneurysm location and other morphologic variables could play a role in predicting overall risk of rupture. Morphological parameters can be divided into 3 main groups, those that are intrinsic to the aneurysm, those that are extrinsic to the aneurysm, and those that involve both the aneurysm and surrounding vasculature (transitional).

OBJECTIVE

We present an evaluation of intrinsic, transitional, and extrinsic factors and their association with ruptured aneurysms.

METHODS

Using preoperative computed tomographic angiography, we generated 3-dimensional models of aneurysms and their surrounding vasculature with Slicer software. Using univariate and multivariate analyses, we examined the association of intrinsic, transitional, and extrinsic aspects of aneurysm morphology with rupture.

RESULTS

Between 2005 and 2013, 227 cerebral aneurysms in 4 locations were evaluated/treated at a single institution, and computed tomographic angiographies of 218 patients (97 unruptured and 130 ruptured) were analyzed. Ruptured aneurysms analyzed were associated with clinical factors of absence of multiple aneurysms and history of no prior rupture, and morphologic factors of greater aspect ratio. On multivariate analysis, aneurysm rupture remained associated with history of no prior rupture, greater flow angle, greater daughter-daughter vessel angle, and smaller parent-daughter vessel angle.

CONCLUSION

By studying the morphology of aneurysms and their surrounding vasculature, we identified several parameters associated with ruptured aneurysms that include intrinsic, transitional, and extrinsic factors of cerebral aneurysms and their surrounding vasculature.

Morphological Parameters Associated With Middle Cerebral Artery Aneurysms

BACKGROUND:

Morphological factors contribute to the hemodynamics of the middle cerebral artery (MCA).

OBJECTIVE:

To identify image-based morphological parameters that correlated with the presence of MCA aneurysms.

METHODS:

Image-based anatomic parameters obtained from 110 patients with and without MCA bifurcation aneurysms were evaluated with Slicer, an open-source image analysis software, to generate 3-dimensional models of the aneurysms and surrounding vascular architecture. We examined segment lengths, diameters, and vessel-to-vessel angles of the parent and daughter vessels at the MCA bifurcation. In order to reduce confounding by genetic and clinical risk factors, 2 control groups were selected: group A (the unaffected contralateral side of patients with unilateral MCA bifurcation aneurysms) and group B (patients without intracranial aneurysms or other vascular malformations). Univariate and multivariate analyses were performed to determine statistical significance.

RESULTS:

One hundred ten patients who were evaluated from 2007 to 2014 were analyzed (73 patients with MCA aneurysms and 37 control patients). Multivariate analysis revealed that a smaller parent artery diameter (group A: odds ratio [OR] 0.20, P &lt; .01, group B: OR 0.23, P &lt; .01) and a larger daughter-to-daughter branch angle (group A: OR 1.01, P = .04, group B: OR 1.02, P = .04) were most strongly associated with MCA aneurysm presence after adjusting for other morphological factors.

CONCLUSION:

Smaller parent artery diameter and larger daughter-to-daughter branch angles are associated with the presence of MCA bifurcation aneurysms. These easily measurable parameters may provide objective metrics to assess aneurysm formation and growth risk stratification in high-risk patients.

Posterior cerebral artery angle and the rupture of basilar tip aneurysms

Since the initial publication of the International Study of Unruptured Intracranial Aneurysms (ISUIA), management of unruptured intracranial aneurysms has been mainly based on the size of the aneurysm. The contribution of morphological characteristics to treatment decisions of unruptured aneurysms has not been well studied in a systematic and location specific manner. We present a large sample of basilar artery tip aneurysms (BTA) that were assessed using a diverse array of morphological variables to determine the parameters associated with ruptured aneurysms. Demographic and clinical risk factors of aneurysm rupture were obtained from chart review. CT angiograms (CTA) were evaluated with Slicer, an open source visualization and image analysis software, to generate 3-D models of the aneurysms and surrounding vascular architecture. Morphological parameters examined in each model included aneurysm volume, aspect ratio, size ratio, aneurysm angle, basilar vessel angle, basilar flow angle, and vessel to vessel angles. Univariate and multivariate analyses were performed to determine statistical significance. From 2008–2013, 54 patients with BTA aneurysms were evaluated in a single institution, and CTAs from 33 patients (15 ruptured, 18 unruptured) were available and analyzed. Aneurysms that underwent reoperation, that were associated with arteriovenous malformations, or that lacked preoperative CTA were excluded. Multivariate logistic regression revealed that a larger angle between the posterior cerebral arteries (P1-P1 angle, p = 0.037) was most strongly associated with aneurysm rupture after adjusting for other morphological variables. In this location specific study of BTA aneurysms, the larger the angle formed between posterior cerebral arteries was found to be a new morphological parameter significantly associated with ruptured BTA aneurysms. This is a physically intuitive parameter that can be measured easily and readily applied in the clinical setting.