Cholesteatomas are benign tumors in cases where a perforation of the eardrum (tympanic membrane) does not heal without surgery, but instead grows through the hole into the middle ear and, if infection develops, results in a cyst-like tumor.

A cholesteatoma cyst consists of desquamating (peeling) layers of scaly or keratinised (horny) layers of epithelium, which may also contain cholesterol crystals.

If untreated, a cholesteatoma can eat into the three small bones located in the middle ear (the malleus, incus and stapes, collectively called ossicles), which can result in nerve deterioration, deafness, imbalance and vertigo. It can also affect and erode, through the enzymes it produces, the thin bone structure that isolates the top of the ear from the brain, as well as lay the covering of the brain open to infection with serious complications.

A history of ear infection or flooding of the ear during swimming should be taken seriously and investigated and cholesteatoma should be considered a possible outcome.

Even after careful microscopic surgical removal, however, 10% to 20% of cholesteatomas may recur, which then require follow-up checks and/or treatment.

Usually cholesteatomas in adults are acquired through the above reasons. Less commonly the disease may be congenital, when it grows from birth behind the eardrum.

Both the acquired as well as the congenital types of the disease can affect the facial nerve that reaches from the brain to the face and leads through the inner and middle ear and leaves at the forward tip of the mastoid bone , and then rises to the front of the ear and extends into the upper and lower face.