Retraction pocket cholesteatoma with mouth at pars flaccida

Acquired cholesteatomas usually arise from focal retractions of the TM. Retraction pockets are invaginations of the TM that form in patients with chronic Eustachian tube dysfunction, negative middle ear pressure, and focal collapse of the TM. Areas of predilection for retraction pockets include old tympanostomy tube sites, the posterosuperior portion of the TM overlying the entrance to the mastoid, and the pars flaccida at the top of the TM (arrows). These can become infected following water exposure or a middle ear infection, resulting in chronic purulent drainage.