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: ENT
Schwartz operation is done in - 
Select and explain. 
A. CSOM, B. Serous otitis media, C. Otosclerosis, D. Acute mastoiditis
D: Acute mastoiditis
Answer: D: Acute mastoiditis 
Explanation: Indications of simple / cortical mastoidectomy (Schwartz operation)

Acute coalescent mastoiditis.
Incompletely resolved acute otitis media with reservoir sign.
Masked mastoiditis.
As a initial step to perform:


Endolymphatic sac surgery
Decompression of facial nerve
Translabyrinthine or retrolabyrinthine procedures for acoustic neuroma.