The ethmoidal sinuses are paranasal sinuses that occur as a paired structure and are also referred to as ethmoidal cells or cellulae ethmoidales.
Anatomy
The ethmoidal sinuses contain numerous thin-walled chambers in the ethmoid bone that are incompletely separated from one another. On each side, an anterior, middle, and posterior group are distinguished. The largest ethmoidal cell is called the bulla ethmoidalis and is located lateral to the nasal wall, above the hiatus semilunaris. Medially, the ethmoidal 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 cells is the anterior cranial fossa, and caudal to them is the maxillary sinus. Depending on their location, the ethmoidal cell groups drain into the middle or superior nasal meatus[^1].