Optic nerve injury following sinus surgery (FESS) is due to removal of which ethmoidal cells?
**Core Concept**
The optic nerve is at risk during functional endoscopic sinus surgery (FESS) due to its close proximity to the ethmoidal air cells, particularly the lamina papyracea and the optic nerve canal. The lamina papyracea is a thin bony plate that separates the ethmoidal air cells from the orbit, and its removal can compromise the integrity of the orbital floor and put the optic nerve at risk.
**Why the Correct Answer is Right**
The ethmoidal cells that are most likely to be involved in optic nerve injury during FESS are the **anterior ethmoidal cells**. These cells are located in the anterior part of the ethmoidal labyrinth and are in close proximity to the lamina papyracea. The anterior ethmoidal cells are also the most commonly involved in orbital complications, including optic nerve injury, during FESS. The anterior ethmoidal cells are drained by the anterior ethmoidal branch of the nasolacrimal duct, which is a key anatomical landmark for identifying the location of the optic nerve during surgery.
**Why Each Wrong Option is Incorrect**
* **Option B:** The posterior ethmoidal cells are located in the posterior part of the ethmoidal labyrinth and are less likely to be involved in optic nerve injury during FESS.
* **Option C:** The maxillary sinus ostium is not directly related to the optic nerve injury during FESS.
* **Option D:** The sphenoid sinus is located posterior to the ethmoidal air cells and is not directly related to the optic nerve injury during FESS.
**Clinical Pearl / High-Yield Fact**
When performing FESS, it is essential to identify the anterior ethmoidal cells and the lamina papyracea to avoid compromising the integrity of the orbital floor and putting the optic nerve at risk.
**Correct Answer: A. Anterior ethmoidal cells**