How many paranasal sinus groups should be visible on a lateral projection of the sinuses?

How many paranasal sinus groups should be visible on a lateral projection of the sinuses?

• A. Three
• B. Four
• C. Five
• D. Two

Answer: (B)

On a lateral projection of the sinuses, you should be able to visualize all the major paranasal sinus groups: frontal, maxillary, ethmoid, and sphenoid. The side view frames the skull so each of these air-filled spaces can be distinguished in profile: the frontal sinuses sit above the orbits, the maxillary sinuses are large and lie below the orbits, the ethmoid sinuses form a maze of tiny cells between the eyes, and the sphenoid sinuses lie deeper, behind the ethmoid group. When the position and exposure are proper, the outlines of these four cavities appear clearly, letting you assess their patency and any mucosal changes. If one is obscured, it’s usually due to inadequate visualization rather than an inherent absence.

On a lateral projection of the sinuses, you should be able to visualize all the major paranasal sinus groups: frontal, maxillary, ethmoid, and sphenoid. The side view frames the skull so each of these air-filled spaces can be distinguished in profile: the frontal sinuses sit above the orbits, the maxillary sinuses are large and lie below the orbits, the ethmoid sinuses form a maze of tiny cells between the eyes, and the sphenoid sinuses lie deeper, behind the ethmoid group. When the position and exposure are proper, the outlines of these four cavities appear clearly, letting you assess their patency and any mucosal changes. If one is obscured, it’s usually due to inadequate visualization rather than an inherent absence.