Morphological Characteristics of the Sphenoid Sinus and Endoscopic Localization of the Cavernous Sinus

The aim of this study was to investigate the relationship between the morphological characteristics of the sphenoid sinus and endoscopic localization of the cavernous sinus (CS) using an extended endoscopic endonasal transsphenoidal approach. Thirty sides of CS in 15 adult cadaver heads were dissected to simulate the extended endoscopic endonasal transsphenoidal approach, and the morphology of the sphenoid sinus and anatomic structures of CS were observed. The opticocarotid recess (OCR), ophthalmomaxillary recess (V1V2R), and maxillomandibular recess (V2V3R) in the lateral wall of the sphenoid sinus were presented in 16 sides (53.3%), 6 sides (20%), and 4 sides (13.3%) of the 30 sides, respectively. OCR is a constant anatomic landmark in endoscopy and coincides with the anterior portion of the clinoidal triangle. The C-shaped internal carotid artery (ICA) in the lateral wall of the sphenoid sinus was presented in 11 sides (36.7%), the upper one-third of which corresponds to the middle portion of the clinoidal triangle, and the lower two-thirds of which correlates to the supratrochlear triangle, infratrochlear triangle, and ophthalmic nerve in CS, around which the medial, lateral, and anteroinferior interspaces are distributed. From a front-to-behind perspective, the C-shaped ICA consists of inferior horizontal segment, anterior vertical segment, clinoidal segment as well as partial subarachnoid segment of the ICA. OCR and C-shaped ICA in the lateral wall of the sphenoid sinus are the 2 reliable anatomic landmarks in the intraoperative location of the parasellar region of CS.