Cholesterol Granuloma
A cystic lesion of the temporal bone thought to be related to breakdown of hemoglobin in patients with chronic otitis media. These lesions can arise spontaneously, in any air -cell tract of the temporal bone, or result from surgery, when natural outflow of ear secretions or hemorrhage is obstructed. These slow growing cystic masses can expand and erode the surrounding bone. When they occur at the petrous apex, pressure can occur on the nerves that move the eyes (most commonly 6th cranial nerve), or the nerve that supplies the sensation of the face.
The diagnosis can be made from its characteristic radiologic appearance on CT or MRI imaging.
The treatment of a petrous apex cholesterol granuloma is drainage, connecting the “trapped cells” with the normal outflow pathways. This can be performed via one of several routes. Drainage via the infracochlear (below the hearing part of the inner ear) approach; infralabyrinthine (below the balance part of the inner ear); zygomatic root (through the front and above the ear), transsphenoid (through the sinuses), or middle cranial fossa approaches have been described.
The most common approach is an infracochlear or peritubal approach which drains the cystic fluid into the middle ear and from there to the eustachian tube.