A quite rare condition: absence of sphenoidal sinuses.

The absence of sphenoidal sinuses (SS) in an adult is an extremely rare condition. We investigated in agenesis of the sphenoid, maxillary, ethmoid, and frontal sinuses in 20 male adult cadavers. In a 50-year-old man, bilateral absence of the SS was observed. On the macroscopic examination, opening of the SS was not found on the lateral wall of the nasal cavity. There were multiple small mucosal grooves between the sphenoidal rostrum and the superior nasal turbinates. The bulging of the sphenoidal rostrum at the choanal level was flat. The body of the sphenoid bone was normal and consisted of a symmetrical bony structure with a total lack of pneumatization. Other paranasal sinuses agenesis was not observed. Surgeons should also consider the possibility of sphenoidal agenesis before transsphenoidal hypophysectomy. As a supplement to the traditional classification, agenesis of the SS can be described as the fourth type of pneumatization.