Endoscopic View of the Infraoptic Recess

The sphenoid sinus is extremely variable in its shape and size. This variability is determined by the extent of pneumatization of the sphenoid bone. ^{1 –3} Pneumatization of the sphenoid bone can extend to the lesser wing of the sphenoid in a superolateral direction to the greater wing of the sphenoid laterally or into the pterygoid process inferolaterally. ⁴

The lateral wall relationships of the sphenoid sinus are of particular importance to the endoscopic sinus surgeon. The internal carotid artery has been found to indent or project into the lateral sinus wall in at least 65% of patients ³ (Figure 1A-C) and has been found to be partially exposed by lateral wall bony dehiscence not infrequently (Figure 1D). ² The prominent medial projection of the optic nerve and canal has been found in up to 40% of cases in a large study by Van Alyea ³ and is frequently seen in the dissection laboratory (Figure 1A) or at the time of sphenoid sinus surgery (Figure 1B-D).

Figure 1.

A, A cadaver dissection of the sphenoid sinus shows the infraoptic recess (arrow). B and C, A surgical dissection shows the optic nerve (ON), the internal carotid artery (ICA), and the infraoptic recess (arrow). D, This surgical dissection shows a prominent dehiscent internal carotid artery (black arrow) and the infraoptic recess (yellow arrow).

A less frequently described anatomic formation seen in the lateral sphenoid wall is the infraoptic recess. In the superolateral wall of the sphenoid sinus between the optic nerve superiorly and the internal carotid artery below can be seen a deep recess, the infraoptic recess (Figure A-D). This deep recess is formed by pneumatization of the anterior clinoid process of the sphenoid bone. ^4,5

Indications for surgical approach of the sphenoid sinus are numerous. These include, but are not limited to, acute and chronic sinusitis, biopsy, and management of benign and malignant tumors, repair of cerebrospinal fluid leaks, and for access to the skull base. The anatomical relationship of the carotid artery and optic nerve is of vital importance in the consideration of the understanding of disease process as well as avoidance of complications in surgical procedures involving the sphenoid sinus. It is vital to have a good understanding of the lateral wall anatomy.