A 32-year-old man undergoes preoperative CT evaluation before FESS. Imaging shows a right posterior ethmoid air cell that has pneumatized superolateral to the sphenoid sinus, with the optic nerve running in a dehiscent canal along its lateral wall. Which anatomical variant is described?
- A Agger nasi cell
- B Haller cell
- C Onodi cell ✓
- D Concha bullosa
Correct answer: C. Onodi cell
Explanation
An Onodi cell (sphenoethmoidal cell) is a posterior ethmoid air cell that extends laterally and superiorly over the sphenoid sinus, bringing the optic nerve and sometimes the internal carotid artery into close relation with its walls. It is the variant that places the optic nerve at greatest risk during endoscopic posterior ethmoidectomy. An agger nasi cell is an anterior ethmoid cell anterior to the frontal recess, a concha bullosa is a pneumatized middle turbinate, and a Haller cell sits along the orbital floor.
Reference: Scott-Brown's Otorhinolaryngology Head and Neck Surgery, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.