Air enters the middle ear via the eustachian tube which opens into the naspharynx (deep portion of the nasal chamber). Recurrent middle ear infections may be due to poor function of the eustachian tube. Although most middle ear infections resolve, some recur or persist. Those chronic infections may lead to damage of the tympanic membrane (ear drum) that can result in a perforation or, in some cases to recurrent infections of the mastoid, or even cholesteatoma. Cholesteatoma is an epithelial cyst (made from the tissue and cells that make skin). Technically, it is not a tumor, but it grows independently. Cholesteatomas grow slowly, yet are able to erode and destroy bone in their path. Most commonly bone destruction is manifest as erosion of the ossicles (the vibrating bones of hearing), but cholesteatoma can erode into the inner ear, leading to nerve deafness and vertigo, or can erode into the intracranial cavity leading to infection around or inside the brain. Cholesteatoma can erode the bone surrounding and protecting the facial nerve, and can lead to facial weakness, or in severe cases paralysis.

Cholesteatoma is treated by microsurgery. Several different types and degrees of tymanomastoidectomy surgery exist for cholesteatoma. The appropriate surgery is selected on the basis of the size and location of the cholesteatoma. Reconstruction of damaged ossicles is also possible, but may require additional surgery depending on the findings at the initial surgery. Cholesteatoma surgery can be lengthy, since it requires meticulous microdissection, but success rates for control of cholesteatoma are high and risks of surgery are low.