Multichannel cochlear implant and electrically evoked auditory brainstem responses in a child with labyrinthitis ossificans.

Ossification of the cochlea following meningitis presents a surgical challenge. Electrode mapping, especially in the young child, is difficult given the uncertainty of electrode contact with viable neural elements. This paper reviews surgical technique and the use of auditory brainstem responses to map the electrodes. A 4-year-old child deafened by meningitis at age 20 months had bilateral cochlear ossification by computed tomography. At surgery, a canal wall-down mastoidectomy and closure of the ear canal were performed. A trough around the modiolus was drilled, and the electrode array was placed in it. Post-operatively, the patient gave aversive or no responses to electrode stimulation. To assess electrode function, auditory brainstem responses to individual electrode activation were obtained under general anesthesia. Functioning electrodes could thus be selected for mapping. The patient now responds well to sound.