Sphenoid sinus: an anatomic and endoscopic study in Asian cadavers.

An anatomic and endoscopic study of 48 cadaveric heads (96 sphenoid sinuses) was undertaken to describe the anatomy of the sphenoid sinus in Asians. Sellar type of sphenoid sinus is the most common, present in 53 out of 96 sides (55%). Forty-five of the 48 heads had a dominant sphenoid cavity, of which 11 contained vital structures from both sides of the sphenoid sinus. The incidence of accessory septae, carotid artery, optic nerve, maxillary nerve, and vidian nerve bulges were 70.8%, 67.7%, 69.8%, 61.5%, and 64.6%, respectively. There is a significantly higher number of overriding ethmoid sinuses in Asian cadavers (46/96 sides) compared to western studies (P < 0.0005). Seven (15%) of these 46 sides were also Onodi positive. The rest of the overriding ethmoid cells were Onodi negative. Surgeons should be aware of the significantly higher number of overriding posterior ethmoid cells in Asian populations during functional endoscopic sinus surgery (FESS). The optic nerve is at risk during FESS surgery if the sphenoid sinus is sought behind the deepest point of these posterior ethmoid cells. These overriding posterior ethmoid cells may also confuse the unwary surgeon that he has entered the sphenoid sinus where in fact he is still operating in the posterior ethmoid cells.