The ethmoid sinuses are paranasal sinuses that occur as a pair and are also referred to as ethmoidal air cells or cellulae ethmoidales.
Anatomy
The sinus ethmoidales contains numerous thin-walled chambers within the os ethmoidale that are incompletely separated. On both sides, an anterior, middle, and posterior group are distinguished. The largest ethmoidal air cell is called the bulla ethmoidalis and is located lateral to the nasal wall, above the hiatus semilunaris. Medially, the ethmoidal air cells border the superior part of the nasal cavity; laterally, they border the orbit, from which they are separated only by a paper-thin bony lamella. Cranial to the ethmoidal air cells is the anterior cranial fossa, and caudal to them is the maxillary sinus. Depending on their location, the ethmoidal air cell groups drain into the middle or superior nasal meatus[^1].