Clinical Analysis Of Increased Carotid Siphon Tortuosity Is Associated With The Presence Of Paraclinoid Aneurysms

Objective The mechanism of intracranial aneurysms formation is still unclear,and may be the result of congenital defect of the arterial wall and a variety of acquired factors.Compelling evidence has shown the association of modifiable（smoking,hypertension,alcohol,atherosclerosis）and non-modifiable（age,gender,heredity）risk factors with the development of intracranial aneurysms.The morphological factors of peripheral blood vessels may play a key role in the formation of intracranial aneurysms,especially the bifurcation and bending sites of arteries are considered to be prone to aneurysm formation.The carotid siphon angle is the cranial curvature of the carotid artery and is one of the highly susceptible sites for vascular disease.These forms of the siphon are not static,but gradually change with the processes of aging,development,and degeneration,especially affected by diseases such as atherosclerosis and hypertension.Paraclinoid aneurysm was defined as an aneurysm arising from the internal carotid artery segment between the top of the cavernous sinus and the beginning of the posterior communicating artery.To explore the association between carotid siphon curvature and the presence of paraclinoid aneurysms of the internal carotid artery,aimed at determining the risk factors of aneurysm formation.Methods The imaging data and clinical records of 42 patients with paraclinoid aneurysms（31 with non-aneurysmal contralateral side）and 42 age-and gender-matched healthy control subjects admitted to the First Affiliated Hospital of Anhui Medical University and Bozhou People’s Hospital from September 2018 to June 2021 were retrospectively analyzed.Morphological characteristics of the carotid siphon（the posterior angle [α],anterior angle [β],and Clinoid@Ophthalmic angle [γ]）were explored via three-dimensional rotational angiography（3DRA）multiplanar reconstruction.The association of carotid siphon morphological characteristics with the formation of paraclinoid aneurysms was assessed through univariate analysis.Subsequently,logistic regression analysis was performed to identify independent risk factors for aneurysms.Lastly,matched pair analysis and subgroup analysis allowed for evaluation of the morphology of carotid siphon in case group.Results Significantly smaller angles α,β,and γ were reported in aneurysmal carotid siphon compared to non-aneurysmal contralateral and healthy controls.Matched pair analysis and subgroup analysis repeated on the carotid siphon angle showed that the differences between the groups were more significant.Bilateral DSA images were obtained in 31 patients with unilateral paraclinoid aneurysms.Compared with the non-aneurysmal contralateral,the carotid siphon（the posterior angle,anterior angle,and Clinoid@Ophthalmic angle）of the carotid artery in the aneurysm group was significantly more narrow and tortuous.Angle β was the best performer in discriminating between aneurysmal and nonaneurysmal the carotid siphon,with an optimal β threshold of 18.25°（AUC 0.861,specificity 83.3%,sensitivity 78.6%）.By adjusting for hypertension,smoking,hyperlipidaemia,and diabetes mellitus,logistic regression analysis demonstrated an independent association of carotid siphons angles α（odds ratio [OR] 0.953;p < 0.05）,β（OR 0.690;p < 0.001）and γ（OR 0.958;p < 0.01）with the risk of paraclinoid aneurysms.Conclusions The mechanism of intracranial aneurysms formation may be the result of congenital defect of the arterial wall and a variety of acquired factors.Evidence on the association of carotid siphon with endothelial dysfunction on the ICA suggests that individuals with greater carotid siphon tortuosity may be at an increased risk of aneurysms.Additionally,the posterior angle,anterior angle,and Clinoid@Ophthalmic angle of carotid siphons were revealed to be independent risk factors for paraclinoid aneurysms.An optimal anterior angle threshold of 18.25（78.6% specificity,83.3%sensitivity）was established for discriminating patients with aneurysms from healthy controls.Overall,the morphological characteristics of carotid siphon hold great promise as a novel imaging biomarker that can guide clinicians in the risk assessment and prognostication of individual patients.