Sudden unilateral blindness after intracranial aneurysm surgery

The incidence of unilateral blindness and ophthalmoplegia after aneurysm surgery is very rare, but if it occurs, it is mainly caused by intra-operative nerve injury. We experienced 6 cases of unilateral blindness immediately after surgery for 3 recent years. These patients were classified into Hunt-Hess grade I to II except for one patient with III. All patients complained of visual loss with varying degree of lid oedema and ophthalmoplegia ipsilateral to the site of surgery. Angiographic examination of these patients revealed that the aneurysm was located at the internal carotid artery bifurcation in one case and the middle cerebral artery bifurcation in five cases. All of them were relatively far from the optic nerve. The aneurysm was clipped easily with minimal brain retraction via standard pterional craniotomy since the brain was slack in all cases. In all cases, injuring the optic nerve during surgery was remote. All patients showed evidence of retinal ischaemia on fundoscopy with or without fluorescein angiography. The pathophysiology of this ischaemic event is unknown. In our patients, we could exclude possible aetiological factors such as abnormal systemic and ocular conditions, causing ischaemia in intra-orbital structures, increased intracranial pressure, intra-operative hypotension, carotid atherosclerosis, and ocular vasospasm etc. Accordingly we speculate that the complications seen in our cases were most likely related to intra-orbital ischaemia initiated by a collapse of the arterial and venous channels in the orbit and/or to direct or indirect contusion on the intra-orbital structures. These situations could be produced by inadvertent pressure placed on the eyeball with a bulky retracted frontal skin flap. Visual acuity in these patients ranged from no light perception to the ability to see objects and detect colour. Their conditions were irreversible. The degree of visual recovery seems to be dependent on the duration and severity of retinal ischaemia by orbital compression. Unfortunately there is no satisfactory treatment. We recommend the use of an eye shield to protect ipsilateral eyeball just before aneurysm surgery.