This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CT SCAN, Subject name: Radiology
Which Ethmoidal Air cells are related to optic nerve? 
Select and explain. 
A. Onodi cells, B. Haller cells, C. Agger nasi cells, D. Mastoid air cells
A: Onodi cells
Answer: A: Onodi cells 
Explanation: Onodi Air Cells: Bilateral aerated cavities lateral to the optic canal, extending into the anterior Glenoid processes. These are variants of the utmost posterior ethmoid cells, Onodi air cells or are otherwise known as Sphenoethmoidal air cells. Their impoance is the close relation to the optic nerve and internal carotid aery and these can be potentially damaged during endoscopic sinus surgery if this variant is not recognised pre-operatively. On the left a smaller Onodi cell is noted, but aeration of the left anterior clinioid process is due to a recess of the sphenoid sinus.