Reparative granuloma related to perilymphatic fistula.

Reparative granuloma is defined as an 'exaggeration of the normal reparative process' (Schuknecht) after stapes surgery, often resulting in a destruction of the labyrinth. It is ascribed to a foreign body reaction, yet there are insufficient histological data to prove this and although rare, the problem is still with us. We encountered two patients in whom the history contains elements evoking a perilymphatic fistula. Cerebrospinal fluid causes irritation of the middle ear mucosa. This is demonstrated in an exemplary way in case of a spontaneously developed cerebrospinal fluid leak from a defect in the tegmen tympani. The leak itself may be very small, but is almost always surrounded by a large mass of granulation tissue. Since the chemical composition of perilymph and cerebrospinal fluid is known to be identical, a persistent perilymphatic leak might likewise be responsible for the formation of a granuloma in the middle ear, eventually invading and destroying the labyrinth. Laboratory experiments to investigate this hypothesis are recommended.