Geometrical and Hemodynamic Characteristic Changes of Small Anterior Communicating Artery Aneurysms during Follow-ups in a Retrospective Analysis

Abstract

Background: Small intracranial aneurysms have a low risk of rupture. However, ruptured anterior communicating artery (ACoA) aneurysms are usually smaller in clinical practice. The retrospective study aimed to investigate the geometrical and hemodynamic changes of small unruptured ACoA aneurysms during serial follow-ups. Materials and Methods: We retrospectively collected patients with small unruptured ACoA aneurysms that were not repaired, who had serial follow-ups from the Electronic Medical Record System in four tertiary hospitals. The geometrical parameters of ACoA aneurysms were measured using a three-dimensional reconstructed model. Intra-aneurysmal hemodynamic parameters were computed using a high-resolution computational fluid dynamics model. Geometrical and hemodynamic changes of the aneurysms were evaluated at each follow-up. Results: Five patients with small unruptured ACoA aneurysms that were not repaired were identified and included in this analysis. Aneurysms rupture occurred in two patients with aneurysm growth. The formation and enlargement of an irregular bleb at the aneurysm neck or dome were observed before the rupture. Ruptured aneurysms showed high wall shear stress (WSS) in the high inflow zone of aneurysm neck while low WSS and high oscillatory shear index (OSI) in the flow-recirculating region of aneurysm dome. Three unruptured aneurysms maintained a stable morphology and a physiological level of WSS. Conclusions: Aneurysm growth, low WSS, and high OSI at the dome and/or high WSS at the neck potentially contribute to the rupture of small ACoA aneurysms. These aneurysms should be considered for the treatment regardless of the small size.