The ethmoid bulla, also known as bulla ethmoidalis, is the largest and most consistent air cell of the anterior ethmoid sinuses.
It can be classified into three subtypes 1:
- simple bulla (50%): a single cavity that usually communicates in the hiatus semilunaris
- compound bulla (25%): 2-3 separate compartments that communicate with the hiatus semilunaris
- complex bulla (25%): 2-3 separate compartments that communicate with the hiatus, ethmoid infundibulum and