Sphenoid 1... The sphenoid sinus is the most posterior sinus. An infected sphenoid sinus can cause posterior headaches. The drainage from the sphenoid is almost directly down the throat. Patients often complain of chronic cough and posterior headaches if the sphenoid is involved. The pituitary gland rests on the top of the sphenoid sinus. 1999 Peter Casano, M.D.