There are great structural variations of the paranasal sinuses. The detailed structure of the paranasal sinuses can be seen using CT scan. They can reveal various aeration differences ranging from normal formation to total aplasia. 

Sphenoidal sinus aplasia is extremely rare. Unilateral frontal sinus aplasia is present in 15% and bilateral is seen in 5%. Maxillary sinus hypoplasia is well known but its aplasia is extremely rare. 1.7 to 10.4% of patients with sinonasal symptoms are reported to have maxillary sinus hypoplasia.