Preservation of hearing after removal of the membranous canal with a cholesteatoma.

Normal cochlear function was preserved in a patient after excision of the membranous canal from a huge fistula at revision surgery eight years after the primary procedure. A recurrent cholesteatoma had eroded the entire prominence of the horizontal canal and surrounded its membranous portion. The cholesteatoma, including the membranous canal, was removed in a one-stage procedure. The open ends of the bony canal were sealed with a fascia soaked in fibrin glue. After initial dizziness and severely reduced hearing, the patient quickly recovered, with normal bone conduction and a stable 30-dB hearing level by air conduction. The lumen of the membranous canal was patent, and only the ampullar end was atretic. Presumably, the fistula became separated from fluid spaces by formation of perilymphatic partitions and by collapse of the membranous labyrinth adjacent to the fistula.