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Cholesterol cyst and cholesterol granuloma of the petrous bone

Developmental cholesterol cysts of the petrous bone most commonly occur at the petrous apex and have been well described (Graham et ai, 1985; Sataloff et ai, 1988; King et at., 1989). These are rarely associated with chronic suppurative otitis media. Cholesterol granulomata are also a well described distinct entity most commonly remaining confined to the middle ear and mastoid system and being associated with previous infection or surgery. Two unusual cases demonstrating cysts in unexpected locations are described. One is of a progressively enlarging developmental cyst of the petrous bone lying in a retro-labryinthine position. The other is of an extensive cholesterol granuloma which was associated with an aural polyp and middle ear infection, but was shown to have large destructive cystic components extending into the jugular foramen and infratemporal fossa. In both cases the use of MRI for assessment and diagnosis and of CT scanning to delineate both the lesion and temporal bone anatomy in planning surgery was invaluable.