Geometric Analysis of Factors Impacting Formation of Cavernous Internal Carotid Artery Aneurysms

Introduction: Unlike bifurcation aneurysms, the cavernous internal carotid artery (cav-ICA) develops side wall aneurysms. We performed geometric analysis from a group of patients with cav-ICA aneurysms and compared it to a control group. We hypothesize that stress concentration at vulnerable points along the cav-ICA contributes to aneurysm formation.

Methods: We retrospectively analyzed 3D rotational angiograms from 28 patients, including 6 with cavernous ICA aneurysms. The DICOM images were segmented in Materialise Mimics, and 3D vascular and skull models were created for analysis. Stress concentration factors including diameter, curvature, geometric or material discontinuity were assessed along the cav-ICA path. Independent t-tests were used to evaluate mean differences between groups.

Results: Cav-ICA diameter was slightly smaller in the aneurysm group (4.64 ± 0.75 mm vs. 4.93 ± 0.59 mm), and the genu diameter was larger in the aneurysm group (5.36 ± 2.0 mm vs. 4.63 ± 0.68 mm); however, neither difference was statistically significant (p > 0.05). Curvatures of the cavernous ICA (0.24 ± 0.35 mm^-1 vs. 0.11 ± 0.07 mm^-1) and genu of the ICA (0.30 ± 0.04 mm^-1 vs. 0.33 ± .11 mm^-1) showed no significant differences between groups (p > 0.05). The aneurysm group showed composite material discontinuity at the point of aneurysm formation.

Conclusion : No statistically significant differences were found in ICA geometry between patients with and without aneurysms. However, the transition from the part of cav-ICA surrounded with bone to the part without bone corresponds to the point of aneurysm formation. This represents material discontinuity, which is an established stress factor. This study introduces a novel use of 3D analysis for exploring aneurysm formation. Future research with a larger sample size and hemodynamic assessments may help clarify the role of ICA geometry in aneurysm pathogenesis.