Purpose:
Intracranial aneurysms display diverse morphologies influenced by parent vessel geometry. The role of 3D vessel tortuosity in differentiating small versus large aneurysms remains underexplored. To comprehensively analyze morphometric and tortuosity parameters of internal carotid arteries (ICA) harboring small (<5mm) versus large (≥5mm) aneurysms using advanced 3D imaging.

Material and methods:
This retrospective study included 48 patients with unruptured unilateral ICA aneurysms (21 small, 27 large) without previous interventions. 3D DSA imaging was used to reconstruct arterial models. We extracted morphometric parameters (radius, length) and tortuosity metrics including relative length (RL), sum-of-angle metric (SOAM), inflection count metric (ICM), and normalized curvature/torsion using validated algorithms.

Results:
ICA radius was significantly smaller in small aneurysm group (2.08±0.27mm vs 2.22±0.17mm; p=0.039). Vessels with small aneurysms demonstrated higher tortuosity: normalized torsion (3.89±6.96 vs -3.43±9.96; p=0.005), normalized curvature (8.91±4.14 vs 5.56±5.75; p=0.025), lower RL (0.56±0.08 vs 0.63±0.05; p=0.002), higher SOAM (2.48±0.56 vs 2.14±0.51; p=0.034), and elevated ICM (8.54±3.07 vs 5.95±2.60; p=0.004).

Conclusions:
Small ICA aneurysms occur preferentially on more tortuous vessels with smaller parent-artery radius. These findings support integrating 3D vessel geometry metrics into research of aneurysm risk stratification and treatment planning algorithms.