Splitting and penetration of the optic nerve by an aneurysm arising from the anterior wall of internal carotid artery: case report

Aneurysms arising from the anterior wall of the internal carotid artery (IC A) are uncommon. There have not been any reports demonstrating the anatomic al relation of such aneurysms to the optic nerve. An aneurysm arising from the anterior wall of the ICA splitting and penetrating the optic nerve is r eported. A 73 year old woman presented with severe headache due to subarach noid haemorrhage. She had never experienced a visual disturbance. At surger y, the aneurysm was shown to arise from the anterior wall of the left inter nal carotid artery and to split and penetrate the left optic nerve. The ane urysm was not related to arterial bifurcation of any branches and was safel y neck clipped. Given the evidence of a split and penetration of the optic nerve, the pathogenesis of such an aneurysm may be due to the persistence o f an embryonic vessel.