During posterior ethmoidectomy, the surgeon notes a posterior ethmoid air cell that has pneumatized superolateral to the sphenoid sinus, lying immediately adjacent to the optic nerve. This anatomical variant, which places the optic nerve at risk, is called:
- A Haller cell
- B Agger nasi cell
- C Onodi cell ✓
- D Concha bullosa
Correct answer: C. Onodi cell
Explanation
An Onodi cell, or sphenoethmoidal cell, is a posterior ethmoid cell that extends superolateral to the sphenoid sinus and intimately relates to the optic nerve canal and sometimes the internal carotid artery. Dissecting it while believing one is entering the sphenoid can cause blindness. A Haller cell is an infraorbital ethmoid cell along the maxillary roof, an agger nasi cell is anterior near the frontal recess, and concha bullosa is a pneumatized middle turbinate.
Reference: Scott-Brown's Otorhinolaryngology and Head and Neck Surgery, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.