This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
The commonest site of otosclerosis is - 
Select and explain. 
A. Round window, B. Utricle, C. Ossicles, D. Oval window
D: Oval window
Answer: D: Oval window 
Explanation: Ans. is 'd' i.e., Oval window o The most common site of disease is promontory in the region of the anterior margin of oval window, and inadvanced cases the stapes become ankylosed in position by a mass of new spongy bone.Why is it so# This area is involved most commonly because in this area is located the fissula ante fenestram, a vestigial structure which frequently contains cartilaginous remnants and which is particularly prone to otosclerotic changes.o Most common type of otosclerosis - Stapedial otosclerosiso Most common site of otosclerosis - Fissula ante fenestram (i.e, just in front of oval window)o Most common site for stapedial otosclerosis - Fissula ante fenestram (i.e, just in front of oval window)o Most common site for cochlear otosclerosis - Round window