More Than Meets the Ear: Incidental Cerebrospinal Fluid Leak During Myringotomy in a Child With Common Cavity Deformity.

Cerebrospinal fluid (CSF) otorrhea represents a breach of the temporal bone separating the subarachnoid space from the middle ear and carries a significant risk of meningitis. While most cases are associated with trauma or prior skull base surgery, congenital fistulas may remain occult until unmasked by otologic procedures.  We report the case of a five-year-old male with bilateral profound sensorineural hearing loss and previously unknown labyrinthine anomalies who developed high-flow, pulsatile clear otorrhea during routine left ear myringotomy for recurrent otitis media. Immediate concern for CSF leak prompted fluid collection for beta-2 transferrin analysis and urgent surgical management. Subsequent exploration via lateral temporal bone resection revealed a congenital inner ear fistula with active CSF egress from the vestibule through the oval window. The leak was successfully managed using a multilayer closure technique including vestibular packing with temporalis fascia, cartilage reinforcement, Eustachian tube obliteration, pedicled temporalis muscle flap coverage, and blind sac external auditory canal closure. This case illustrates the recognition and acute intraoperative management of an unanticipated high-flow CSF leak during a routine pediatric otologic procedure, and supports preoperative temporal bone imaging in children with profound sensorineural hearing loss before middle-ear instrumentation. Untreated, such leaks carry a significant risk of life-threatening meningitis.