Transsphenoidal optic nerve decompression: an endoscopic anatomic study.

The objective was to study the relationships among the optic nerve, posterior paranasal sinuses, and ophthalmic artery. The identification of reliable anatomic landmarks would provide an endoscopic anatomic basis for optic nerve localization and effective prevention of ophthalmic artery injury during transsphenoidal optic nerve decompression surgery. The Messerklinger technique was performed to open the posterior ethmoid sinus and sphenoid sinus in 8 adult-head specimens. The opticocarotid recess and optic canal were identified under endoscopy, and the relationships between the optic nerve and posterior paranasal sinuses were observed. The relationship between the optic nerve and ophthalmic artery was examined. In all specimens, the opticocarotid recess could be identified; however, the optic nerve protuberance was present in only 10 sides (62%). Three types of relationships were found to exist among the optic nerve, sphenoid sinus, and posterior ethmoid sinus. The posterior ethmoid sinus was anterior and the sphenoid sinus was posterior in 8 sides (50%), the sphenoid sinus was both anterior and posterior in 5 sides (31%), and the ethmoid sinus was both anterior and posterior in 3 sides (19%). At the intracranial opening of the optic canal, the ophthalmic artery was inferomedial to the optic nerve in 9 sides (56%), inferior to the optic nerve in 4 sides (25%), and inferolateral to the optic nerve in 3 sides (19%). The ophthalmic artery coursed laterally from inferior to the optic nerve, and at the intraorbital opening of the optic canal, the ophthalmic artery was inferolateral to the optic nerve in 13 sides (81%) and inferior to the optic nerve in 3 sides (19%). The opticocarotid recess is always present; the imaging characteristics of endoscopy allow this recess to be more reliably identified than the optic nerve protuberance. It can be used as the anatomic landmark of choice in endoscopic optic nerve decompression. The origin of the ophthalmic artery is inferomedial to the optic nerve, and thereafter, it courses inferolaterally. An intersecting relationship exists along its course, a factor that must be taken into account during surgery to avoid injuring the ophthalmic artery.