Correlation Between The Locations Of Middle Cerebral Arterial Bifurcation Aneurysm And The Vessel Diameters Of The Two Branches Of The Bifurcation

Purpose: Intracranial aneurysms have emerged as a serious threat to human health,with the highest incidence,rupture rate,and mortality rate.Intracranial aneurysms are not congenital,but are currently thought to result from a combination of congenital genetic defects and multiple acquired external environmental factors.Current studies consider that the presence of age(advanced age),adverse habits(smoking,alcohol consumption),and underlying medical conditions(hypertension,diabetes,etc.)may be associated with the evolution of intracranial aneurysms(onset,progression,and rupture).In addition to this,the characteristics of the vessels surrounding the aneurysm itself,such as the morphological parameters of the surrounding vessels and hemodynamic changes,are also involved in the evolutionary process.The middle cerebral artery(MCA)bifurcation is a relatively easy site for intracranial aneurysm formation,and there is definite evidence that morphological factors(e.g.,M1 and M2 diameters,vessel angle,and curvature of the mother-daughter vessels)of the MCA bifurcation vessels are associated with aneurysm formation.However,in our clinical work,we found that the location of aneurysms in the bifurcation of the middle cerebral artery is variable,with the neck of the aneurysm not exactly in the apical proper center of the bifurcation,which triggered our team’s curiosity about this phenomenon.In previous studies in the literature on the location of intracranial bifurcation aneurysms,differences in the diameter of the vessels branching the bifurcation may cause the creation of terminal internal carotid artery aneurysms and anterior communicating aneurysms.On this basis,we added several relevant morphological parameters to the study.Therefore,the aim of this study was to investigate whether the factors of morphological variables of the bifurcation could influence the location of the aneurysm neck at the bifurcation of the middle cerebral artery.METHODS: We collected CTA data and general clinical data from patients with confirmed aneurysms at the middle cerebral artery bifurcation between July 2018 and June 2022 at the First and Second Affiliated Hospitals of Anhui Medical University,while excluding data with poor reconstruction and three or more branches at the bifurcation.In addition,vascular data at the middle cerebral bifurcation were collected from patients with normal intracranial CTA.After reconstruction by open-source software,the desired morphological parameters were measured.Ninety-eight patients with aneurysms at the MCA bifurcation and 30 patients with normal intracranial CTA were included in this study,including data from 105 aneurysms at the middle cerebral artery bifurcation,data from 49 normal peri-MCA bifurcation vessels on the non-aneurysmal side,and data from55 normal peri-MCA bifurcation vessels reconstructed from the middle cerebral artery bifurcation.All data were divided into an aneurysm group and a control group.The morphological parameters of the vessels at the bifurcation,including vessel diameter(D1,D2),mother-daughter vessel angle(L,S)and vessel tortuosity(TL,TS),were measured separately,and the diameter ratio(DR),area ratio(SR)and angle ratio(LSR)were calculated.A comparative analysis of the aneurysm group and the control group was first performed to find the risk factors associated with aneurysm formation at the bifurcation of the MCA.Then,the MCA bifurcation aneurysms were divided according to the location of the aneurysm neck in the MCA bifurcation,and the morphological parameters between the aneurysms in different locations were analyzed,while logistic regression analysis was later performed to identify the morphological parameters that could predict and distinguish the aneurysms in different locations.RESULTS: The results showed significant differences between MCA bifurcation aneurysms and normal middle cerebral artery(MCA)vessels surrounding the bifurcation in terms of bifurcation vessel angle,angle ratio,and curvature,as well as the patient’s advanced age and hypertension.After univariate and multivariate logistic regression analysis,there were significant differences in diameter ratio(DR)between type A and type C,angle L and S between type B and type C,and angle L and L-side tortuosity between type A and type B.CONCLUSION: Middle cerebral artery(MCA)bifurcation aneurysms are associated with morphological parameters of the bifurcation branch vessels(larger vessel angle,smaller angle ratio,smaller curvature),advanced age,and history of hypertension.Notably,the location of MCA bifurcation aneurysms was associated with differences in branch vessel diameters,that is,the greater the difference in diameter between the two branch vessels,the more aneurysms tended to form in the larger diameter branch vessel.This article is the first vascular morphology study to address the bias associated with the location of aneurysms at the MCA bifurcation,and the final results are consistent with our clinical findings and preliminary assumptions.