Bifurcation Location Is Significantly Associated with Rupture of Small Intracranial Aneurysms (<5 mm)

Evaluation of PHASES Score for Predicting Rupture of Intracranial Aneurysms: Significance of Aneurysm Size

BACKGROUND

Recent data have identified that certain risk factors for rupture differ between small and larger intracranial aneurysms (IAs). Such differing risk factors make up 5 out of the 6 predictor variables used in the PHASES score, which raises the question on whether IA size has a significant effect on the score's performance.

METHODS

Patients who were diagnosed with an IA incidentally or due to a subarachnoid hemorrhage between 2015 and 2023 were selected for potential inclusion. The median IA size of the cohort was chosen as the cutoff point to categorize small and large (6 mm). The PHASES score was calculated for all patients, and a receiver operating characteristic curve analysis was performed to evaluate the classification accuracy of PHASES in predicting rupture for small and large IAs.

RESULTS

A total of 677 IAs were included. Among the IAs, 400 (58.9%) presented as UIAs and 279 (41.0%) as subarachnoid hemorrhage. The average PHASES score was 2.9 and 6.5 for small (n = 322) and large (n = 355) IAs, respectively. The PHASES score performed significantly lower for predicting rupture in smaller IAs (area under the curve: 0.634) compared with the larger (area under the curve: 0.741) (P = 0.00083).

CONCLUSIONS

PHASES was shown to underperform on small IAs. The decision to treat small unruptured IAs remains highly controversial, and the development of a new score to estimate the annual rupture rate while accounting for IA morphology is of great need. Our findings can help encourage future researchers to develop such a score.

Differences and Correlations of Morphological and Hemodynamic Parameters between Anterior Circulation Bifurcation and Side-wall Aneurysms

OBJECTIVE

The objective of this research was to explore the difference and correlation of the morphological and hemodynamic features between sidewall and bifurcation aneurysms in anterior circulation arteries, utilizing computational fluid dynamics as a tool for analysis.

METHODS

In line with the designated inclusion criteria, this study covered 160 aneurysms identified in 131 patients who received treatment at Union Hospital of Tongji Medical College, Huazhong University of Science and Technology, China, from January 2021 to September 2022. Utilizing follow-up digital subtraction angiography (DSA) data, these cases were classified into two distinct groups: the sidewall aneurysm group and the bifurcation aneurysm group. Morphological and hemodynamic parameters in the immediate preoperative period were meticulously calculated and examined in both groups using a three-dimensional DSA reconstruction model.

RESULTS

No significant differences were found in the morphological or hemodynamic parameters of bifurcation aneurysms at varied locations within the anterior circulation. However, pronounced differences were identified between sidewall and bifurcation aneurysms in terms of morphological parameters such as the diameter of the parent vessel (Dvessel), inflow angle (θF), and size ratio (SR), as well as the hemodynamic parameter of inflow concentration index (ICI) (P<0.001). Notably, only the SR exhibited a significant correlation with multiple hemodynamic parameters (P<0.001), while the ICI was closely related to several morphological parameters (R>0.5, P<0.001).

CONCLUSIONS

The significant differences in certain morphological and hemodynamic parameters between sidewall and bifurcation aneurysms emphasize the importance to contemplate variances in threshold values for these parameters when evaluating the risk of rupture in anterior circulation aneurysms. Whether it is a bifurcation or sidewall aneurysm, these disparities should be considered. The morphological parameter SR has the potential to be a valuable clinical tool for promptly distinguishing the distinct rupture risks associated with sidewall and bifurcation aneurysms.

Predictors for Rupture of Small (<7mm) Intracranial Aneurysms: A Systematic Review and Meta-Analysis

INTRODUCTION

Identifying predictors for rupture of small intracranial aneurysms (sIAs) have become a growing topic in the literature given the relative paucity of data on their natural history. The authors performed a meta-analysis to identify reliable predictors.

METHODS

PubMed, Scopus, and Web of Science were used to systematically extract references which involved at least 10 IAs <7mm which including a control group experiencing no rupture. All potential predictors reported in the literature were evaluated in the meta-analysis.

RESULTS

Fifteen studies yielding 4,739 sIAs were included in the meta-analysis. Four studies were prospective and 11 were retrospective. Univariate analysis identified 7 predictors which contradicted or are absent in the current scoring systems, while allowing to perform subgroup analysis for further reliability: patient age (MD -1.97, 95%CI -3.47-0.48; P = 0.01), the size ratio (MD 0.40, 95%CI 0.26-0.53; P < 0.00001), the aspect ratio (MD 0.16, 95%CI 0.11-0.22; P < 0.00001), bifurcation point (OR 3.76, 95%CI 2.41-5.85; P < 0.00001), irregularity (OR 2.95, 95%CI 1.91-4.55; P < 0.00001), the pressure loss coefficient (MD -0.32, 95%CI -0.52-0.11; P = 0.002), wall sheer stress (Pa) (MD -0.16, 95%CI -0.28-0.03; P = 0.01). All morphology related predictors listed above have been confirmed as independent predictors via multivariable analysis among the individual studies.

CONCLUSIONS

Morphology related predictors are superior to the classic patient demographic predictors present in most scoring systems. Given that morphology predictors take time to measure, our findings may be of great interest to developers seeking to incorporate artificial intelligence into the treatment decision-making process.

Pediatric brain aneurysms: a review of 1458 brain MR angiograms

PURPOSE

To evaluate clinical and imaging characteristics of pediatric brain aneurysms.

MATERIALS AND METHODS

A retrospective review of 1458 MR angiograms of pediatric patients (≤18 years old) obtained between 2006 and 2021 was performed. A non-infundibular arterial luminal outpouching larger than 1mm in size was identified as an "Intracranial aneurysm." Patient demographics, clinical presentations, and predisposing risk factors, including family history and underlying medical conditions, were reviewed. MRA images were analyzed for aneurysm location, number, maximum diameter, and interval changes on follow-up.

RESULTS

Forty-nine (3.3%) patients (30 females, 19 males) with 64 intracranial aneurysms were identified with an average age of 13.71 ± 3.67 years. Eleven (22.4%) patients had multiple aneurysms. An underlying systemic illness was observed in 81.6% (40/49) cases, with sickle cell disease as the most frequent (25/49, 51%) diagnosis. A first-degree family history of intracranial aneurysms was recognized in 36/1458 (2.5%) patients. However, no intracranial aneurysm was found in this group. While 02/49 (4%) patients presented with acute SAH, headache was the most common (16/49, 32.7%) symptom at presentation in unruptured cases. The majority (47/64, 73.4%) of the aneurysms were located in the anterior circulation, with the ICA ophthalmic segment being most frequently (24/47, 51%) involved. Most (54/64, 84.4%) aneurysms were smaller than 4mm in size at the time of diagnosis. At least one follow-up MRA was obtained in 72.3% (34/47) of the unruptured aneurysms cohort. There was no change in the aneurysm size and morphology in 31/34 (91.2 %) patients over an average imaging follow-up of 39.6 months. Three (6%) patients demonstrated an interval increase in the aneurysm size. SAH patients (n=2) and two unruptured aneurysm patients with an interval increase in size were successfully treated with endovascular techniques.

CONCLUSION

Female predominance with a higher frequency of small and unruptured intracranial aneurysms was recognized in our cohort. A higher incidence of an underlying systemic illness, especially sickle cell disease, was also noted. Most intracranial aneurysms in children appear to remain stable. However, there seems to be the risk of an aneurysm size increase which warrants regular clinical and imaging follow-up.

Rupture discrimination of multiple small (< 7 mm) intracranial aneurysms based on machine learning-based cluster analysis

BACKGROUND

Small multiple intracranial aneurysms (SMIAs) are known to be more prone to rupture than are single aneurysms. However, specific recommendations for patients with small MIAs are not included in the guidelines of the American Heart Association and American Stroke Association. In this study, we aimed to evaluate the feasibility of machine learning-based cluster analysis for discriminating the risk of rupture of SMIAs.

METHODS

This multi-institutional cross-sectional study included 1,427 SMIAs from 660 patients. Hierarchical cluster analysis guided patient classification based on patient-level characteristics. Based on the clusters and morphological features, machine learning models were constructed and compared to screen the optimal model for discriminating aneurysm rupture.

RESULTS

Three clusters with markedly different features were identified. Cluster 1 (n = 45) had the highest risk of subarachnoid hemorrhage (SAH) (75.6%) and was characterized by a higher prevalence of familiar IAs. Cluster 2 (n = 110) had a moderate risk of SAH (38.2%) and was characterized by the highest rate of SAH history and highest number of vascular risk factors. Cluster 3 (n = 505) had a relatively mild risk of SAH (17.6%) and was characterized by a lower prevalence of SAH history and lower number of vascular risk factors. Lasso regression analysis showed that compared with cluster 3, clusters 1 (odds ratio [OR], 7.391; 95% confidence interval [CI], 4.074-13.150) and 2 (OR, 3.014; 95% CI, 1.827-4.970) were at a higher risk of aneurysm rupture. In terms of performance, the area under the curve of the model was 0.828 (95% CI, 0.770-0.833).

CONCLUSIONS

An unsupervised machine learning-based algorithm successfully identified three distinct clusters with different SAH risk in patients with SMIAs. Based on the morphological factors and identified clusters, our proposed model has good discrimination ability for SMIA ruptures.

The Association of Morphological Differences of Middle Cerebral Artery Bifurcation and Aneurysm Formation: A Systematic Review and Meta-Analysis

OBJECTIVE

We explored the relationships between morphological parameters of middle cerebral artery (MCA) bifurcations based on imaging and the development of middle cerebral aneurysms. Artery bifurcations can form disordered hemodynamics which can promote the development of aneurysms, whereas the hemodynamic environment at the bifurcation tip is highly reliant on the bifurcation's geometry.

METHODS

We searched 3 electronic databases for all relevant, publicly available publications as of March 18, 2022. Through the screening of abstracts and full texts, a meta-analysis was performed to compare the daughter-to-daughter angle, the inclination angle (γ), and the parent vessel diameter of MCA bifurcations between patients in MCA aneurysm and non-aneurysm controls.

RESULTS

Ten articles describing 1012 patients with MCA aneurysms and 1106 control individuals without aneurysms were included in the analysis. The aneurysm group showed a larger daughter-to-daughter branch angle at MCA bifurcations than the non-aneurysm group (weighted mean difference [WMD] = 42.00; 95% confidence interval [CI], 33.77 to 50.23; P < 0.00001). The daughter-to-daughter angle was also larger in the MCA aneurysm group with than without an aneurysm side branch (WMD = 37.03; 95% CI, 26.57 to 47.50; P < 0.00001), and in the MCA aneurysm group than in the non-aneurysm control group (WMD = 41.87; 95% CI, 29.19 to 54.54; P < 0.00001). The aneurysm group had a larger inclination angle than the control group (WMD = 28.73; 95% CI, 18.78 to 38.69; P < 0.00001). In patients with a MCA aneurysm, the parent vessel of the branch with the MCA aneurysm tended to be smaller in diameter than the contralateral branch without the aneurysm (WMD = -0.12; 95% CI, -0.24 to 0.00; P = 0.05).

CONCLUSIONS

A larger daughter-to-daughter angle and larger inclination angle at MCA bifurcations are closely related to MCA bifurcation aneurysms. The parent vessel diameter is negatively related to MCA bifurcation aneurysms.

Novel Models for Identification of the Ruptured Aneurysm in Patients with Subarachnoid Hemorrhage with Multiple Aneurysms

BACKGROUND AND PURPOSE

In patients with SAH with multiple intracranial aneurysms, often the hemorrhage pattern does not indicate the rupture source. Angiographic findings (intracranial aneurysm size and shape) could help but may not be reliable. Our purpose was to test whether existing parameters could identify the ruptured intracranial aneurysm in patients with multiple intracranial aneurysms and whether composite predictive models could improve the identification.

MATERIALS AND METHODS

We retrospectively collected angiographic and medical records of 93 patients with SAH with at least 2 intracranial aneurysms (total of 206 saccular intracranial aneurysms, 93 ruptured), in which the ruptured intracranial aneurysm was confirmed through surgery or definitive hemorrhage patterns. We calculated 13 morphologic and 10 hemodynamic parameters along with location and type (sidewall/bifurcation) and tested their ability to identify rupture in the 93 patients. To build predictive models, we randomly assigned 70 patients to training and 23 to holdout testing cohorts. Using a linear regression model with a customized cost function and 10-fold cross-validation, we trained 2 rupture identification models: RIM_C using all parameters and RIM_M excluding hemodynamics.

RESULTS

The 25 study parameters had vastly different positive predictive values (31%-87%) for identifying rupture, the highest being size ratio at 87%. RIM_C incorporated size ratio, undulation index, relative residence time, and type; RIM_M had only size ratio, undulation index, and type. During cross-validation, positive predictive values for size ratio, RIM_M, and RIM_C were 86% ± 4%, 90% ± 4%, and 93% ± 4%, respectively. In testing, size ratio and RIM_M had positive predictive values of 85%, while RIM_C had 92%.

CONCLUSIONS

Size ratio was the best individual factor for identifying the ruptured aneurysm; however, RIM_C, followed by RIM_M, outperformed existing parameters.

Safety and efficacy of treatment of very small intracranial aneurysms

Purpose

Very small intracranial aneurysms (VSIAs) may cause many neurological complications and even death. Thanks to technological progress and higher quality of non-invasive neuroimaging methods, these pathologies can be investigated sooner and treated earlier. Due to the controversy surrounding invasive treatment of these pathologies, the aim of the study was to analyse methods of treatment, their outcome, and complications in a group of patients with VSIAs.

Material and methods

Out of 444 cases of intracranial aneurysms treated in our centre, 65 aneurysms met the radiological criteria of VSIAs. The parameters – width and length of the aneurysm’s neck and width, length, and height of the aneurysm’s dome – were measured. The analysed parameters were as follows: symptoms upon admission and after treatment, days in hospital, and intraoperative complications. Clinical and radiological intensity of subarachnoid haemorrhage (SAH) was evaluated by using the Hunt-Hess and Fisher scales. The degree of embolisation of the aneurysm after the procedure was assessed using the Montreal Scale. Clinical outcome was assessed by Glasgow Outcome Scale.

Results

50.77% of VSIAs were treated with endovascular procedures and 49.23% with neurosurgical clipping. SAH was presented in 38.46% of patients with VSIAs. Intraoperative complications were presented in 16.92% of patients with VSIAs, and the most common complication was ischaemic stroke. Stents were used in 51.52% of VSIAs. In 69.70% of embolisation procedures at VSIAs complete obliteration was achieved. The average result in the Montreal Scale was 1.31 (SD = 0.66).

Conclusion

VSIAs can be treated as effectively and safely as larger aneurysms, by both endovascular and surgical methods.

Bifurcation Configuration Is an Independent Risk Factor for Aneurysm Rupture Irrespective of Location

Background: Bifurcation and sidewall aneurysms have different rupture risks, but whether this difference comes from the location of the aneurysm is not clear. The objective of this study is to illustrate the rationality of ranking bifurcation configuration as an independent risk factor for aneurysm rupture.

Methods: Morphological features of 719 aneurysms (216 ruptured) were automatically extracted from a consecutive cohort of patients via PyRadiomics. Rupture risks and morphological features were compared between bifurcation and sidewall aneurysms, and lasso regression was applied to explore the morphological determinants for rupture in bifurcation and sidewall aneurysms. Rupture risks and morphological features of bifurcation aneurysms in different locations were analyzed. Multivariate regression was performed to explore the risk factors for aneurysm rupture.

Results: Twelve morphological features were automatically extracted from PyRadiomics implemented in Python. The rupture risks were higher in bifurcation aneurysms (P < 0.01), and morphological features Elongation and Flatness were much lower in ruptured bifurcation than sidewall aneurysms (P = 0.036, 0.011, respectively). Elongation and Flatness were the morphological determinants for rupture in bifurcation aneurysms, whereas Elongation and SphericalDisproportion were determinants for sidewall aneurysms. Different rupture risks and morphological features were found between sidewall and bifurcation aneurysms of the same location, and among bifurcation aneurysms of different locations. In multivariate regression, bifurcation configuration was an independent risk factor for aneurysm rupture (OR 3.007, 95% CI 1.752–5.248, P < 0.001).

Conclusions: Sidewall and bifurcation aneurysms and bifurcation aneurysms of different locations have different rupture risks and morphological features. Bifurcation configuration is an independent risk factor for aneurysm rupture irrespective of location.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Bifurcation Location and Growth of Aneurysm Size Are Significantly Associated with an Irregular Shape of Unruptured Intracranial Aneurysms

BACKGROUND AND OBJECTIVE

Previous studies firmly proved that an irregular aneurysmal shape was associated strongly with intracranial aneurysm (IA) rupture, but it is unclear how irregularly shaped IAs form. We aimed to identify the factors related to irregular shape of IAs.

METHODS

We retrospectively analyzed of consecutive patients evaluated or treated for IA at our institution from June 2015 to July 2016. According to the imaging morphology of aneurysm, the enrolled patients were divided into irregular and regular group. Demographic data and imaging data of the 2 groups were compared to identify the factors related to aneurismal irregular shape.

RESULTS

There were 429 aneurysms (180 irregular and 249 regular aneurysms), including 315 unruptured aneurysms and 114 ruptured aneurysms. Most unruptured aneurysms occurred in the internal carotid arteries (53.3%), anterior communicating artery (10.8%), and posterior communicating artery (10.8%), anterior cerebral artery (5.4%), middle cerebral artery (9.8%), and posterior circulation (9.8%). In univariate analysis, for unruptured aneurysm, irregular aneurysmal shape was significantly related to aneurysm size (P = 0.009), aspect ratio (P = 0.003), size ratio (P = 0.002), and location at the bifurcation (P = 0.009) but not with smoking status, hypertension, hyperlipidemia, or diabetes mellitus. In multivariate logistic analysis, irregular aneurysms occurred mainly in unruptured aneurysms with a larger size (diameter ≥5 mm; odds ratio [OR] 2.106; 95% confidence interval [CI] 1.183-3.749; P = 0.011); location at a bifurcation (OR 2.017; 95% CI 1.191-3.413; P = 0.006), and aspect ratio (≥0.8; OR 4.992; 95% CI 1.318-18.915; P = 0.018).

CONCLUSIONS

Location at a bifurcation, an increased aneurysm size, and greater aspect ratio are significant independent factors associated with an irregular shape in unruptured IAs but not with smoking status, hypertension, hyperlipidemia, or diabetes mellitus.