Multiple intracranial aneurysms: a direct hemodynamic comparison between ruptured and unruptured vessel malformations

Despite numerous studies addressing the rupture risk of intracranial aneurysms that have been published, the assessment thereof still remains challenging. Image-based simulations enable a precise prediction of patient-specific blood flow information. However, those approaches normally consider only small segments of the complete cerebral vasculature.

To test the validity of the consideration of single aneurysms in one computational setup, domains of the complete anterior and posterior circulations with multiple intracranial aneurysms (MIA) were simulated. Six patients with MIA were investigated, while 3D surfaces of eleven unruptured and six ruptured aneurysms were segmented. The segmentations were used for the determination of morphological parameters and also for image-based blood flow simulations used to characterize the hemodynamic properties of each aneurysm.

In the geometric comparison, neck aspect ratios of unruptured and ruptured aneurysms did not differ significantly. In contrast, size ratios, aspect ratios, surface areas, volumes, and non-sphericity indices were significantly higher in the ruptured cases. The analysis of hemodynamic parameters demonstrated that in each patient, the ruptured aneurysm exhibited the lowest averaged wall shear stresses and highest oscillatory shears. Unstable flow was also detected in ruptured aneurysms based on increased oscillatory velocity.

In this small study involving patients with MIA, different morphologies and flow patterns were observed between ruptured and unruptured aneurysms. The analysis of the hemodynamics in such patients revealed a good agreement with studies that only considered single malformations. Additionally, complex flow patterns are detected in ruptured cases, which require deeper investigation.