Special Names of the Ethmoid Air Cells

Agger nasi cells are the most anterior ethmoid air cells and are located within the lacrimal bone. They are located anterior, lateral, and inferior to the frontoethmoidal recess and anterior and above the attachement of the middle turbinate.

Haller cells refer to ethmoid air cells that are located along the inferolateral margin of the orbit and protrude into the maxillary sinus. If they get too big, they can block the drainage pathway of the maxillary sinus.

Ethmoidal bulla refers to the largest ethmoid air cell, located above and behind the infundibulum and hiatus semilunaris. If it gets too big, it can block the drainage pathway of the maxillary sinus and result in the infundibular pattern of sinus disease.

Onodi (sphenoethmoid) cells are the posteriormost ethmoidal air cells that pneumatize into the sphenoid bone superior to the sphenoid sinus. The image shows a left Onodi cell (white arrows) above the left spenoid sinus (pink arrow). The right sphenoid sinus is indicated by the blue arrow. They can be intimately associated with the optic nerve (most common, green arrow) and internal carotid artery (less common). The anterior clinoid process may be pneumatized via Onodi cells (not so in this case). Onodi cells are important in sinus surgery. In a transsphenoidal approach, an Onodi cell can be entered under, resulting in damage the optic nerve or internal carotid artery.

References

Kantarci M, Karasen RM, Alper F, Onbas O, Okur A, Karaman A. Remarkable anatomic variations in paranasal sinus region and their clinical importance. Eur J Radiol. 2004 Jun;50(3):296-302.