Cholesteatoma

Definition:

A type of cyst located in the middle ear.

Causes, incidence, and risk factors:

Cholesteatoma may be a congenital defect but more commonly occurs as a complication of chronic ear infection. Prolonged inflammation and malfunction of the eustachian tube leads to chronic negative pressure in the middle ear. This pulls a portion of the eardrum (tympanic membrane) inward, creating a sac or cyst that fills with old skin cells. The cyst becomes chronically infected. The cyst typically continues to grow and may erode the mastoid bone and the bones of the middle ear.