Type of sphenoid sinus in adult population is usually:

The types of the sphenoid sinus can be classified in three groups in the adult: I. conchal, II. presellar, and III sellar types, depending on the extent to which the sphenoid bone is pneumatized. In the conchal type, the area below the sella is a solid block of bone without an air cavity. In the presellar type, the sphenoid sinus has moderate air cavity with no sellar indentation. In the sellar type, which is the most common, the corpus of the sphenoid is well pneumatized with full indentation of the sella into the sinus and extends posteriorly until the clivus The conchal type is most common in children and infrequent in the adult (Rhoton).