Morphometry of Cerebral Arterial Bifurcations Harbouring Aneurysms: A Case-Control Study On 253 Patients
Abstract Background Conclusions from studies evaluating vessel dimensions and their deviations from the values resulting from the principle of minimum work (PMW) on the formation of intracranial aneurysms (IAs) are still inconclusive. The aim of our study was the morphometric analysis of cerebral arterial bifurcations harbouring aneurysms. Methods The study comprised 147 patients with basilar artery (BA) and middle cerebral artery (MCA) aneurysms, and 106 patients constituting the control group. The following morphometric parameters were evaluated: the radii of vessels forming the bifurcation, the junction exponent, the values of the bifurcation angles (Φ1 and Φ2 angles between the parent vessel trunk axis and the larger or smaller branches, respectively; α angle, total bifurcation angle) and the difference between the predicted optimal and observed branch angles. Results The analysed parameters for internal carotid artery (ICA) bifurcations were not significantly different among the groups. MCA and BA bifurcation angles and the radii of the parent MCA and BA vessels with aneurysms were significantly higher compared to the control group. The differences between the predicted optimal and observed branch angles were significantly higher for BA and MCA bifurcations with aneurysms compared to the control group. The mean junction exponent for bifurcations in the circle of Willis (i.e., ICA and BA bifurcations, respectively) and MCA bifurcations with aneurysms was significantly lower than the theoretical optimum and not significantly different among the groups. In a multilevel multivariate logistic regression analysis, the branch angles and the radius from the parent vessel were significant independent predictors of the presence of IAs. The ROC analysis indicated that the α angle was the best performer in discriminating between aneurysmal and non-aneurysmal bifurcations. Conclusions The dimensions of the arteries forming the circle of Willis do not follow the PMW. The deviation from optimum bifurcation geometry for bifurcations beyond the circle of Willis (particularly a wider radius of the parent artery and a wider total bifurcation angle) may lead to the formation of IAs. Further studies are warranted to investigate the significance of vessel dimensions and the bifurcation angle on the magnitude of the shear stress in the walls of arterial bifurcations.