Carotid-ophthalmic aneurysms – protective features making them a rare cause of subarachnoid hemorrhage

Abstract

Objective: To review the rate of carotid-ophthalmic aneurysm (COA) rupture and to identify protective features that may contribute to their low rupture rate.
Methods: We reviewed the records of 790 patients with 773 aneurysms greater than 2 mm treated by endovascular routes between 2002 and 2012 at our institution. Seventy five carotid-ophthalmic aneurysms were identified in 72 patients. Three injected human cadaver heads were studied to evaluate the perianeurysmal environment of the carotid-ophthalmic region.
Results: Only 2 (2.8%) of these 72 patients presented with acute SAH due to a ruptured carotid-ophthalmic aneurysm. The average size of ruptured COA was 11.3 mm versus 7 mm for unruptured aneurysms. Most of the aneurysms were discovered in patients who were asymptomatic. The most common presenting symptom was headache. In this study, we also provide cadaveric anatomic illustrations of the perianeurysmal environment in order to investigate the low rate of COA rupture. Additionally, we highlight the existence of a double arachnoid layer consisting of the arachnoid on the inferior aspect of the optic nerve and surrounding the internal carotid artery (ICA), which could further contribute to the low rupture rate of these aneurysms.
Conclusions: Carotid-ophthalmic aneurysms are uncommon sources of subarachnoid hemorrhage. The perianeurysmal environment surrounding these aneurysms may provide protection, lending these aneurysms to a relatively benign natural history.