Abstract
BACKGROUND: In this study, we aimed to comparatively evaluate the morphology of internal carotid artery (ICA) bifurcations with and without aneurysms and identify risk factors for aneurysm development that are associated with the bifurcation geometry. METHOD: In this two-center study, the computerized tomography angiography data of 1512 patients were evaluated. The study included 64 (4.2%) patients with ICA bifurcation aneurysms (ICAbifAn) and patients with anterior circulation aneurysms (non-ICAbifAn). ICA (P1) was defined as the parent artery, and the middle (M1) and anterior (A1) cerebral artery segments were defined as daughter arteries. We measured the diameters of the P1, M1, and A1 and their ratios (BifSR) to identify the risk factors. In addition, we calculated the bifurcation angle in two ways by measuring all angles between the P1 and daughter arteries and compared these two methods. The first method was the angle between the M1 and A1 (α), and the second was the sum of the angles between the P1 and daughter arteries (BifA). RESULT: A total of 163 patients who met the inclusion criteria were included in this study: 58 patients in the ICAbifAn group and 105 patients in the non-ICAbifAn group. A univariate logistic regression analysis revealed that the P1, BifSR, α, and BifA measurements were significant predictors of aneurysm formation. However, after a multivariate analysis, only the BifA angle retained its significance (OR, 0.911 (0.877-0.946), p < 0.001). In the ROC curve, the optimal BifA threshold for accurately differentiating between an ICAbifAn and non-aneurysmal bifurcation was 210° (area under the curve (AUC), 0.81; sensitivity, 69%; and specificity, 87%). The α angle had an AUC of 0.68. CONCLUSIONS: These results suggest that bifurcation geometry plays a significant role in the likelihood of aneurysm formation. We also showed that the BifA was more predictive of aneurysm formation than the α angle.