MATERIAL and METHODS: Three dimensional (3D) digital subtraction angiography (DSA) studies from 180 patients with ruptured sidewall (SW) and sidewall with branching vessel (SWB) aneurysms, and 70 patients with ruptured endwall (EW) aneurysms were retrospectively analyzed, excluding anterior communicating artery aneurysms. In SW and SWB cases, relationships between maximum aneurysm depth and various geometric features, including neck diameter, parent vessel (PV) curvature angle, and diameter difference between proximal and distal PV segments, were explored. In EW cases, the neck diameter, branching angle, and discrepancy between daughter vessel diameters were measured and compared with aneurysm depth.

RESULTS: A narrow PV curvature angle significantly correlated with greater maximum aneurysm depth in SW aneurysms (p-value=0.019). PV stenosis distal to SW aneurysms was significantly associated with greater aneurysm depth at the time of rupture (p-value<0.001). A wider branching angle was associated with smaller aneurysm depth at the time of rupture in EW aneurysms having daughter vessels narrower in caliber than their PV (p-value=0.02). A positive significant correlation was recorded between aneurysm depth and neck width in both EW and SW aneurysm types (p-value<0.001).

CONCLUSION: Geometric factors such as PV curvature angle, neck width, and PV distal narrowing could affect the risk of growth and rupture of SW and SWB aneurysms. A wider branching angle could be considered in the early rupture of EW aneurysms. Neck width could be significantly related to the growth and rupture of both SW and EW intracranial aneurysms. Keywords : Aneurysm rupture, Flow dynamics, Parent vessel curvature angle, Branching angle, Neck