This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
Operation of choice for coalescent mastoiditis is: 
Select and explain. 
A. Cortical mastoidectomy, B. Modified radical mastoidectomy, C. Radical mastoidectomy, D. Fenestration operation
A: Cortical mastoidectomy
Answer: A: Cortical mastoidectomy 
Explanation: Coalescent mastoiditis is treated by cortical mastoidectomy, also known as Schwartz operation. In this operation all mastoid air cells are exenterated leaving posterior canal wall intact.