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
What is the COMMONEST complication of CSOM? 
Select and explain. 
A. Subperiosteal abscess, B. Mastoiditis, C. Brain abscess, D. Meningitis
B: Mastoiditis
Answer: B: Mastoiditis 
Explanation: Mastoiditis is the most common complication of CSOM. Acute mastoiditis usually accompanies or follows acute suppurative otitis media. Complications of otitis media are classified into two main groups: A.Intratemporal: Mastoiditis Petrositis Facial paralysis Labyrinthitis B.Intracranial: Extradural abscess Subdural abscess Meningitis Brain abscess Lateral sinus thrombophlebitis