Endoscopic View Through the Anterior Nasal Aperture. G, Anterior endoscopic view of reconstructed sphenoid, ethmoid, and both palatine bones. Only the lower medial part of the anterior wall of the sphenoid sinus, which corresponds to the sphenoid conchae, is seen through the nasal cavity. The remainder of the anterior wall of the sphenoid sinus is hidden behind the ethmoid bone, which shares its posterior wall with the anterior wall of the sphenoid sinus. The sphenoid ostium is exposed near the superior angle of the sphenoid concha. The posterior ethmoid air cells share a common wall with the upper lateral part of the anterior wall of the sphenoid sinus. H, The ethmoid bone has been removed. The right half of the anterior wall of the sphenoid sinus has been opened. The sphenopalatine foramen is located just above the ethmoid crest in the lateral wall of the nasal cavity between the sphenoid and orbital processes of the palatine bone. I, Posterior wall of the sphenoid sinus. There is a spontaneous dehiscence of bone over the left carotid artery. The posterior sinus wall is limited superiorly by the sellae and laterally by the prominences overlying the cavernous carotid. The posterior sinus wall corresponds to the part of the clivus formed by the sphenoid bone. The sinus wall often extends posteriorly beyond the vertical coronal plane of posterior wall of pituitary fossa to form a clival recess. The vidian canal is located at the lower lateral corner of the sphenoid sinus. J, View extending to the clivus, foramen magnum, and C1. In this specimen, the opticocarotid recesses, the recess located between the optic canal and the carotid prominence that extends into the optic strut, is shallow. K, Left lateral wall of the sphenoid sinus viewed with a 45-degree endoscope. In this specimen, the pneumatization extends laterally beyond the vidian canal into the greater wing to form a lateral recess. The left vidian canal underlies a bony ridge in the lateral part of the floor of the sphenoid sinus. L, Posterior wall of the sphenoid sinus in another specimen. The vertical paraclival segment of the carotid artery ascends along the lateral limit of the posterior wall of the sphenoid sinus. (Images courtesy of AL Rhoton, Jr.)