Geometry of the internal carotid artery and recurrent patterns in location, orientation, and rupture status of lateral aneurysms: an image-based computational study

BACKGROUND: Intracranial aneurysm development and rupture may be associated to the morphology of the parent vessel. OBJECTIVE: To quantitatively characterize the geometry of the internal carotid artery (ICA) in relation to the location and orientation of lateral aneurysms and to identify recurrent patterns associated with their rupture status. METHODS: The geometry of 54 ICAs hosting lateral aneurysms was analyzed by means of computational geometry techniques. The ICA was split into individual bends, and the bend hosting the aneurysm was described in terms of curvature, torsion, length, and radius. Aneurysm position and orientation with respect to the parent vessel and specifically the hosting bend were characterized, as well as angles between the portions of the parent artery immediately upstream of and downstream from the aneurysm and the aneurysm ostium. Differences in geometric parameters with respect to rupture status and their performance as classifiers were evaluated. RESULTS: ICA bends hosting ruptured aneurysms were shorter with a smaller radius, lower maximum curvature, and lower proximal torsion compared with those hosting unruptured lesions. Ruptured aneurysms occurred in more distal portions of the ICA, along the outer wall of the vessel, and closer to the curvature peak within the hosting bend than unruptured ones. The proximal portions of ICAs hosting ruptured aneurysms approached the ostium region at a smaller angle. CONCLUSION: Geometric factors relative to the ICA were associated with the distribution of aneurysms and their rupture status. The present work has potential implications in the quest for hemodynamic factors contributing to the development, progression, and rupture of intracranial aneurysms.