Unruptured Paraclinoid Carotid Aneurysms Occur More Frequently in Younger Ages

PURPOSE: We investigated the age distribution of cerebral saccular aneurysms in various locations to clarify the differences by location and discuss the mechanism of formation. MATERIALS AND METHODS: We retrospectively assessed clinical material obtained from 1,252 unruptured aneurysms treated with endovascular embolization between 2004 and 2019. Age, sex, laterality, and size were investigated by the location of aneurysms, classified as cavernous internal carotid artery (ICA), paraclinoid ICA, supraclinoid ICA, anterior communicating artery, anterior cerebral artery, middle cerebral artery, basilar artery complex, and posterior inferior cerebellar artery. Paraclinoid aneurysms were subclassified into 3 patterns according to their projecting direction: S-type, with superior protrusion; M-type, with medial protrusion; and P-type, with posteroinferior protrusion. RESULTS: There was no significant difference by location for sex, laterality, and size. The mean age of patients with paraclinoid aneurysms (56.5 years old) was significantly lower than that of other aneurysm patients (64.3 years old). Notably, 40% of the patients with M-type aneurysms were <50 years old. This percentage was significantly higher than that of aneurysms at other locations (P<0.05). CONCLUSION: We found a young female predominance for patients with paraclinoid carotid aneurysms. This study may suggest that congenital factors contribute to paraclinoid aneurysm formation as well acquired factors, such as hemodynamic stress, atherosclerotic wall damage, and local inflammation.