Surgical endoscopic anatomy of the sphenoid sinus. Structural foundation: tactical and technical.

The object of this presentation is to describe the endoscopic anatomy of the sphenoid sinus and its approaches, providing the surgeon with a step to step guide for dissection of then region in lab or everyday surgical practice.The following study was done on cadaveric material and bones with rigid 4mm rigid endoscopes and 0, 30 and 90 grades optics. The chosen approaches were the direct endonasal and transnasal transeptal approach. The sphenoid sinus is the most posterior of all paranasal sinuses. It is located in the middle and inferoposterior part of the sphenoid bone. It shows a variable size and it is surrounded by anatomic structures such as the carotid artery and the optic nerves, which can be damaged during surgical approach. The optic nerves can protrude inside the sphenoid sinus. In some cases, the horizontal portion of the intracavernous carotid artery protrudes inside of it too. Other anatomic structures are related to the sinus: meninges, the pituitary gland, the optic chiasm and the cavernous sinuses. The floor of the cavernous sinus may show the prominence of the maxillary nerve.Endoscopic anatomy of the sphenoid sinus has its own characteristics whic differ from macroscopic ones. In using an endoscope, interpreting and knowing exactly the anatomic relations in three dimensions, is mandatory for a successful approach to the sphenoid sinus. The sphenoid sinus congregates the interest of multiple specialties, for being a point in common to many approaches of paranasal sinuses, decompressive surgeries of optic nerve, of medial wall of cavernous sinus and sellar region. Endoscopic approach to sphenoid sinus allows the use of a natural orifice and highly respects anatomic structures.