Elsevier

World Neurosurgery

Volume 107, November 2017, Pages 255-262
World Neurosurgery

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

https://doi.org/10.1016/j.wneu.2017.07.063Get rights and content

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.

Introduction

Intracranial aneurysm (IA) is a common cerebrovascular disease with a prevalence of approximately 5%,1 is the most common cause of subarachnoid hemorrhage (SAH),2 and is associated with high mortality and morbidity rates.3 Recent studies have indicated that 17%–76% of IAs are irregularly shaped aneurysms.4, 5

Furthermore, an irregular aneurysmal shape was associated strongly with IA rupture in large observational series and also was an independent predictor of rupture risk in a Japanese natural history study.6 Abboud et al.5 reported that the rate of aneurysm rupture is increased for irregular aneurysms and an irregular shape accounts for 76%in all IAs.

Many reports have hypothesized that an irregular aneurysmal shape may be related to degeneration and weakness of the lesion wall.7 Moreover, Cebral et al.8 have reported that irregular aneurysms with blebs form at or adjacent to regions with high wall shear stress (WSS) and are aligned to major intra-aneurysmal flow structures. However, few studies have investigated the factors related to irregular shape in IAs. Here, we performed a retrospective review of patients with IAs to identify the factors related to irregular shape in IAs.

Section snippets

Patient Population and Exclusion Criteria

Our study was approved by the review committee of Beijing Tiantan Hospital and conformed to the tenets of the Declaration of Helsinki, and informed consent was obtained from all participants when they were enrolled. We performed a single-center study of patients evaluated or treated for IAs at our institution, from June 2015 to July 2016. All patients received conventional digital subtraction angiography of the internal and external carotid artery and vertebral artery. Thereafter, 3-dimensional

Patient Characteristics

A total of 429 aneurysms (180 irregular and 249 regular aneurysms) were enrolled, 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%).

One hundred twenty-eight patients were excluded for the following reasons: (1) multiple IAs were

Discussion

This study showed that location at a bifurcation, an increased aneurysm size and greater AR are significant independent factors associated with an irregular shape in unruptured IA but not smoking status, hypertension, hyperlipidemia, or DM. Many reports have suggested that hemodynamic factors and pathologic mechanisms in the IA wall are factors significantly associated with formation of IAs with an irregular shape.24 Some research has shown that bleb in IA is at or adjacent to areas of high

Conclusions

This study showed that location at an arterial bifurcation is a significant independent factor for the formation of aneurysms with an irregular shape and that growth in the aneurysm size also may be related to irregularly shaped aneurysms. Further studies of hemodynamic and pathologic mechanisms related to a bifurcation location, aneurysmal growth, and irregular shape of IAs should be performed.

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    Conflict of interest statement: This work was supported by the Natural Science Foundation of Beijing, China (No.7142032), and Specific Research Projects for Capital Health Development (2014–3-2044).

    Xin Feng and Baorui Zhang contributed equally and are co–first authors.

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