Role of electrically evoked auditory brainstem response in cochlear implantation of children with inner ear malformations.

Objective: To evaluate the usefulness of promontory electric auditory brainstem response (EABR) testing in children with inner ear malformations before cochlear implantation indicated by postoperative speech performance.

Study Design: Retrospective analysis.

Setting: Tertiary academic cochlear implant center.

Patients: Forty-three children with congenital inner ear malformations, of which 39 received a cochlear implant. Age at implant ranged from 12 months to 13 years. Patients were categorized into 3 groups based on the type of malformations. Groups 1 and 2 involved malformations of the cochlea and/or vestibular organ. Group 3 consisted of children with narrow internal auditory canal.

Interventions: Preoperative EABR testing with threshold, Wave V amplitude, and latency determination.

Main Outcome Measures: Postoperative speech perception performance was measured using Glendonald Auditory Speech Perception Tests for words and sentences, Northwestern University-Children's Perception of Speech test, and minimal pairs test. Patients were further categorized into a speech perception category based on these test results.

Results: Mean values for EABR threshold, Wave V amplitude, and latency for Group 1 (11 patients) were 485 microA, 0.21 microV, and 4.51 milliseconds, respectively. Mean values for Group 2 (20 patients) were 556 microA, 0.26 microV, and 4.45 milliseconds, respectively. Mean values for Group 3 (8 patients) were 500 microA, 0.11 microV, and 4.65 milliseconds, respectively. Open-set sentence recognition was possible in 73% in Group 1, 30% in Group 2, and 38% in Group 3 by 36 months after implant activation. Patients with lower preoperative EABR threshold (<600 microA) had better postoperative speech performance (p < 0.05). Larger Wave V amplitude and shorter latency were associated with better speech performance.

Conclusion: Preoperative EABR is useful in determining cochlear implant candidacy in children with inner ear malformations. Results of this study indicate that the EABR accurately predicts outcome when cochlear implant efficacy is uncertain.