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
A 30-year old male is having Attic cholesteatoma of left ear with lateral sinus thrombophlebitis. Which of the following will be the operation of choice 
Select and explain. 
A. Intact canal will be the operation of choice, B. Simple mastoidectomy with tympanoplasty, C. Canal wall down mastoidectomy, D. Mastoidectomy with cavity obliteration
C: Canal wall down mastoidectomy
Answer: C: Canal wall down mastoidectomy 
Explanation: Canal wall down procedures: They leave the mastoid cavity open into modified the external auditory canal so that the disease area is fully exteriorised. The commonly performed operations for the atticoantral disease are atticotomy, radical mastoidectomy and rarely, the radical mastoidectomy. ( Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 80)