Giant aneurysms of the carotid system presenting as visual field defect.

Visual field loss was the presenting symptom in 19 patients with large intracranial aneurysms of the carotid system. Location of the aneurysm was cavernous, carotid-ophthalmic (two), supraclinoid (nine), anterior communicating (six). Other features were pain and a long history of fluctuating visual loss. Cavernous or carotid-ophthalmic aneurysms mostly caused purely uniocular field loss consistent with optic nerve compression. Supraclinoid aneurysms most often caused a lateral chiasmal syndrome. Anterior communicating aneurysms caused asymmetric compression of one or both optic nerves, the eye contralateral to the feeding artery being more often affected. Carotid ligation appeared to arrest visual deterioration in some patients in the supraclinoid group.