A cholesteatoma is an abnormal skin growth in the middle ear behind the eardrum, usually in the form of cysts or pouches that shed layers of old skin. Although they may be congenital, most commonly they occur following successive or chronic ear infections. The functioning of the Eustachian tube compensates the pressure in the middle ear but may not work well when negative pressure builds up, pushing part of the tympanic membrane into the middle ear. This creates a sac or cyst of old skin and other waste materials i.e. the cholesteatoma. Over time, the cholesteatoma can grow and destroy the middle ear bones or other structures of the ear. Some symptoms that may result from such growth include: hearing loss, loss of balance, dizziness and even paralysis or dysfunction of the facial muscles.