**2.6 Sphenoid sinus**

The sphenoid sinus is well known as a part of para-sinus which is close to the skull base. It can be used for the transnasal, transsphenoidal approach. However, it can be accessed from the transcranial approach. The posterior part of the SphS can be opened above and below the VN. After exposing and opening the vidian canal, the VN can be followed to the PPG anteriorly. The sphenopalatine artery supplies the SphS mucosa, except for the area of the planum sphenoidal, which is supplied by the posterior ethmoidal artery.
