During FESS for chronic ethmoid sinusitis, a surgeon encounters a posterior ethmoid air cell that has pneumatized superolaterally above and lateral to the sphenoid sinus, bringing the optic nerve into close proximity with its roof. This anatomical variant, which carries a serious risk of optic nerve injury, is called:

• A Haller cell
• B Agger nasi cell
• C Onodi cell ✓
• D Concha bullosa

Explanation

An Onodi cell, or sphenoethmoidal cell, is a posterior ethmoid cell that pneumatizes superiorly and laterally over the sphenoid sinus, so that the optic nerve canal or carotid canal may lie in its wall or project into it. Dissecting posteriorly assuming one is entering the sphenoid can therefore injure the optic nerve or internal carotid artery. A Haller cell is an infraorbital ethmoid cell along the maxillary sinus roof, an agger nasi cell is the anterior-most ethmoid cell near the frontal recess, and concha bullosa is pneumatisation of a turbinate.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.