Occult cholesteatoma of the middle ear.

A clinico-pathological study of 10 cases (including histopathology) indicates that occult cholesteatoma is neither a congenital cholesteatoma nor an epidermoid cyst, originating in the attic through a melaplastic process of middle ear mucosa behind an intact tympanic membrane. Occult cholesteatoma is due to retraction and active immigration of the epidermal layer of the tympanic membrane into the narrow compartments of the epitympanic area and its causative factor is a chronic inflammatory stimulus. Symptomatology is insiduous because extension of destruction depends entirely on the direction of its growth which for its part is guided by the mucosal folds of the epitympanic space.