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': 'True about BAHA \nSelect and explain. \nA. Useful in canal atresia and microtia, B. Useful in bilateral severe SNHL, C. Useful after surgery in neurofibromatosis 2 for acoustic neuroma, D. It can bypass cochlea', 'role': 'user'}, {'content': 'Answer: A \nExplanation: BAHA: Bone anchored hearing aid is a type of hearing aid which is based on the principle of bone conduction. BAHA uses a surgically implanted abutment to transmit sound by direct conduction through bone to cochlea, bypassing the external auditory canal and middle ear. When air-conduction (AC) hearing aid cannot be used: - Canal atresia, congenital or acquired, not amenable to treatment. - Chronic ear discharge, not amenable to treatment. - Excessive feedback and discomfo from air-conduction hearing aid. Conductive or mixed hearing loss, e.g. otosclerosis and tympanosclerosis where surgery is contraindicated. Single-sided hearing loss. For severe bilateral SNHL--Cochlear implant is used. For bilateral acoustic neuromas in Neurofibromatosis - auditory brainstem implant is used.', 'role': 'assistant'}]