Split optic nerve penetrated by a carotid-ophthalmic aneurysm another instance of a rare presentation: Case report

Abstract

Penetration of the optic nerve by aneurysms of the paraclinoid carotid artery is rare. We present the seventh aneurysm-related split optic nerve case reported in the literature, review the pathophysiologic mechanisms and discuss the technical aspects for successful clip ligation and complication avoidance. A 64-year-old male with history of hypertension, chronic obstructive pulmonary disease and polycystic kidneys presented with headache and dizziness. Magnetic resonance imaging and angiographic work-up confirmed the presence of a right-sided partially thrombosed carotid-ophthalmic aneurysm. There was no evidence of significant visual dysfunction. A right pterional craniotomy with frontal extension was performed. The aneurysm dome was noted to extend subfrontally after passing through a split optic nerve. Aneurysm neck was clipped using a combination of standard ophthalmic and fenestrated clips. During immediate post-operative period the patient had worsening of visual acuity, yet showed progressive visual improvement on clinical follow-up. The pathophysiologic mechanisms for aneurysm development range from congenital to mechanical/hemodynamic. Our patients clinical presentation suggests a slowly growing lesion that may have penetrated through a weak spot in the overlying optic nerve. This may have been caused by either congenital fenestration of the optic nerve, persistent vestigial artery or an old unrecognized hemorrhage. Optic nerve penetration by carotid-ophthalmic aneurysms occurs rarely, yet is being increasingly reported and recognized. Knowledge of this potential configuration can help avoid inadvertent damage and improve results by novel application of fenestrated and standard clips.