You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is The segment of facial nerve most commonly involved in CSOM/ cholesteatoma? and explain in detail?
Ans. a (Tympanic part). (Ref. Radiology of ent by Valvassori 1st ed., 70)Cholesteatomas may erode the facial nerve canal and expose the nerve rarely. The most common site of facial nerve canal erosion is area extending from oval window to the pyramidal eminence and the proximal portion of the vertical segment. Erosion of the anterior part of tympanic segment and geniculate ganglion may occur in large anterior epitympanic lesions. Erosion of mastoid segment occurs in lesions which involve the entire mastoid.