Labyrinthine Cyst Arising in a Longstanding Cavity After a Canal Wall Down Mastoidectomy

Objective: Describe the clinical course and management of a labyrinthine cyst associated with a labyrinthine fistula arising in a longstanding cavity after a canal wall down mastoidectomy. Study Design: Case report. Setting: University Hospital, tertiary referral center. Patients, Intervention, and Results: A 71-year-old woman who underwent left radical mastoidectomy at age 7 was referred to our clinic complaining of left ear fullness. She experienced severe vertigo for several years postoperatively, but did not complain of vertigo at her initial visit. A pale cystic mass was seen in the external auditory canal. She was completely deaf in her left ear and showed no signs of a fistula. Computed tomography and magnetic resonance imaging revealed a 12-mm mass in the superior semicircular canal and the vestibule. Removal of the cyst led to perilymph leakage through a large labyrinthine fistula, which was sealed by cortical bone chips, bone dust, and temporal fascia with fibrin glue. Histological examination revealed that the cyst wall was composed of fibrous connective tissue, contained scattered calcium deposits, and lacked an inner epithelial lining. The postoperative course was uneventful, and there has been no recurrence for 45 months. Conclusion: To our knowledge, this is the first reported case of a labyrinthine cyst associated with a labyrinthine fistula. This delayed labyrinthine fistula is a unique complication in a longstanding cavity after a canal wall down mastoidectomy.