Commonest complication of CSOM is
50% of brain abscesses in adults and 25% in children are otogenic in origin. In adults, an abscess usually follows CSOM with cholesteatoma. (Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 90)
Subperiosteal abscess
Mastoiditis
Brain abscess
Meningitis
Ear