any structural anomaly of the small, air-filled, mucosa-lined cavity that is located in the petrous portion of the temporal bone and houses the auditory ossicles and intratympanic muscles (tensor tympani and stapedius) as well as the chorda tympani and the tympanic plexus of nerves; it is split into two parts: the tympanic cavity proper (the space directly internal to the tympanic membrane) and the epitympanic recess or attic (the space superior to the tympanic membrane)