Tympanic membrane retraction adherent to other structures within the middle ear. Some retractions continue to progress and grow more deeply into the ear. This can result in erosion of bone. As the middle ear is only a narrow space, the eardrum only has to retract a short distance before it touches boney structures within the middle ear such as the ossicles. It may become adherent to these bones and in some cases, this contact leads to erosion of the bone. As well as ossicular erosion, the bone of the ear canal (e.g. the scutum) and even bone over the cochlea (the promontory) can
Tympanic part of the temporal bone squama and mastoid part, and forms the anterior boundary of the tympanomastoid fissure. Its upper border fuses laterally with the back of the postglenoid process, while medially it bounds the petrotympanic fissure. The medial part of the lower border is thin and sharp; its lateral part splits to enclose the root of the styloid process, and is therefore named the "vaginal process". The central portion of the tympanic part is thin, as it gives rise to the bony inner two-thirds of the ear canal, and in 5 - 20% of skulls the lower surface is perforated by a hole, the