This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Otosclerosis, Subject name: ENT
Most common site for the initiation of otosclerosis: 
Select and explain. 
A. Footplate of stapes, B. Margins of stapes, C. Fissula ante-fenestrum, D. Fissula post-fenestrum
C: Fissula ante-fenestrum
Answer: C: Fissula ante-fenestrum 
Explanation: (c) Fissula ante-fenestrum(Ref. Cummings, 6th ed., 2212)Though otosclerosis ultimately results in the fixation of the footplate and margins of stapes which is lying over the oval window, it actually gets initiated most commonly in the immature cartilaginous area of the bony labyrinth which lies anterior to the fenestra of oval window and hence called fissula ante fenestrum.Fissula post-fenestrum area of the bony labyrinth is also cartilaginous but otosclerosis is uncommon here.