Cholesteatoma can be a congenital defect, but it more commonly occurs as a complication of chronic ear infection. Long-term 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 and other debris. The cyst becomes chronically infected. The cyst typically continues to fill with debris over time and may erode the mastoid bone and the bones of the middle ear.
The only known treatment is surgical removal of the cholesteatoma. Surgery may involve the creation of a common area in the middle ear and mastoid bone that may need to be periodically cleaned by the surgeon.