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
[{'content': 'Most common site of perilymph fistula ? \nSelect and explain. \nA. Round window, B. Oval window, C. Otic capsule, D. Attic', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Oval window Perilymph fistula In this condition, perilymph leaks into the middle ear through the oval or round window. Perilymphatic fistula (so positive fistula test) may occur due to a defect in one of three locations : 1. Oval - window (most common site) Stapedectomy surgery (for otosclerosis) Head trauma or Barotrauma (Pressure injury) Acoustic trauma 2. Round window (rupture of round window membrane) Barotrauma :- SCUBA diving, airplane pressurization Congenital malformations (mondini dysplasia) 3. Otic capsule Another possible location for a fistula is in the bone of the ear (the otic capsule). This is a rare condition where the bone between the ear and brain area is missing or thin, causing symptoms very similar to that of round or oval window fistula. Causes are :- Superior canal dehiscence syndrome Cholesteotoma Fenestration surgery (surgically created window in horizontal SCC) Erosion of Horizontal (lateral) SCC due to any cause Temporal bone fracture Micro fissure", 'role': 'assistant'}]