During routine FESS for chronic ethmoid sinusitis, the surgeon identifies a posterior ethmoid air cell that has pneumatized superolaterally above and lateral to the sphenoid sinus, lying immediately adjacent to the optic nerve canal. Which anatomical variant is this, and what is its surgical significance?

• A Haller cell, it narrows the maxillary ostium
• B Agger nasi cell, it obstructs the frontal recess
• C Onodi cell, the optic nerve is at risk of injury during dissection ✓
• D Concha bullosa, it compresses the middle meatus

Explanation

An Onodi cell, also called a sphenoethmoid cell, is a posterior ethmoid cell that pneumatizes above and lateral to the sphenoid, bringing the optic nerve and sometimes the internal carotid artery into the dissection field. Preoperative CT review for this variant is mandatory before posterior ethmoidectomy. Haller cells lie along the orbital floor and narrow the maxillary ostium, while agger nasi cells sit in the frontal recess, which distinguishes the other options.

Reference: Cummings Otolaryngology Head and Neck Surgery, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.