An anatomic and CT scan study of the lateral wall of the sphenoid sinus as related to the transnasal transethmoid endoscopic approach.

Interest in endoscopic sinus surgery has expanded to include the sphenoid sinus. While the transnasal transethmoid approach is an established route to the sphenoid sinus, instrumentation is brought close to the lateral wall. This study organizes the lateral wall of the sphenoid sinus into three distinct areas. Fifteen fixed cadaver specimens, 15 fresh specimens and 25 axial as well as coronal CT scans are used to examine each area of the lateral wall. The orbital apex, spongy vascular tissue of the cavernous sinus and the internal carotid artery are found in tandem sequence adjacent to the lateral wall of the sphenoid sinus. A highly pneumatized sphenoid sinus may attenuate the bone over the lateral wall placing the optic nerve and carotid artery at greater risk. Anatomic variations, as examined in this study, and limitations imposed by endoscopic vision via the transnasal transethmoid approach dictates a need to understand the anatomy as well as familiarity with endoscopic surgery. Axial CT scans of the sphenoid sinus can image anatomic variations which may compromise safety of the lateral sphenoid sinus wall.