Analysis of sphenoid sinus in the operative plane of endoscopic transsphenoidal surgery using computed tomography

Recently, the endoscopic transsphenoidal approach for sphenoid sinus or intracranial lesion has gained more popularity and the study of the surgical anatomy and relationships of the sphenoid sinus has gained increased significance. The aim of this study was to clarify the anatomical features of the sphenoid sinus including surrounding structures as seen in the operative view of endoscopic transsphenoidal surgery. The various distances in the sphenoid sinus as well as the relationships between the sphenoid sinus ostium (SO) and important structures such as the optic canal (OC) and carotid artery (CA) according to the presence of Onodi cell (sphenoethmoidal cell; Onodi group vs. non-Onodi group) were assessed using multiplanar and three-dimensional model of CT scans in 100 patients. The SO was more inferior in Onodi group and located superior to the lowest point of the sella. The horizontal distance from the SO to sella was approximately 13 or 14 mm depending on the existence of Onodi cells. Regardless of Onodi cell, the whole course of the OC in the sinus ran superolaterally to inferomedially in the endoscopic view. However, Onodi cell made the angles from the SO to OC larger. In Onodi group, the CA was located from the SO in a superolateral direction, but in non-Onodi group, the CA was located from the SO in the inferolateral direction. This study provides anatomical information about the sphenoid sinus, with important surgical distances between the SO and surrounding structures measured, which is essential to avoid complications during transsphenoidal surgery.