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': 'Post head injury, the patient had conductive deafness and on examination, tympanic membrane was normal and mobile. Likely diagnosis is - \nSelect and explain. \nA. Distortion of ossicular chain, B. Haemotympanum, C. EAC sclerosis, D. Otosclerosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In post head injury, the conductive deanfess may occur due to:\n\nFracture temporal bone (more commonly longitudinal) extending to external canal: tympanic membrane is frequently torn and inner ear is spared.\nBlood or CSF in external and middle ear.\nDamage to ossicle (most frequent being incudo-stapedial joint) resulting in more severe and permanent conductive deafness.\nAseptic necrosis of long process of incus can lead to late conductive deafness.\n\nIn the Question it is given:\nTympanic membrane is normal and mobile: In hemotympanum - tympanic membrane will appear red/blue (due to presence of blood pigments) so it is ruled out.\nOtosclerosis and EAC sclerosis do not occur in case of head injury and hence they are ruled out.\nALSO KNOW\nCauses of SNHL in case of head injury:\n\nLabyrinthine concussion\nVestibular damage.', 'role': 'assistant'}]