Residual hearing preservation after pediatric cochlear implantation

Abstract

Objective: This study is designed to test the hypothesis that preservation of residual hearing in a pediatric population is possible using standard electrode arrays with full-length insertions. Surgical technique during implantation also is described.

Study design: Retrospective review of patient medical records.

Setting: Academic tertiary care center.

Patients: Thirty-one severely to profoundly hearing impaired pediatric patients with some residual hearing precochlear implantation.

Intervention: Cochlear implantation using a modified "soft surgery" protocol.

Main outcome measures: Preimplant and postimplant pure tone thresholds and pure-tone average were calculated from unaided preoperative and postoperative audiograms from 250, 500, and 1,000 Hz. Hearing preservation rates were determined to be complete (loss of ≤10 dB), moderate (loss of 11-20 dB), marginal (loss of 21-40 dB), or none (loss of >40 dB or no response at the limits of the audiometer). Functional residual hearing rates (defined in this study as at least 1 threshold better than or equal to 75 dB HL for 250, 500, or 1,000 Hz were calculated.

Results: Complete hearing preservation was achieved in 14 (45.2%) of 31 patients, whereas 28 (90.3%) of 31 had at least partial hearing preservation (loss of ≤40 dB). The preoperative to postoperative low-frequency pure-tone average had a mean change of 18.5 dB and median change of 20 dB. Of the patients who had preoperative functional hearing, 9 (50.0%) of 18 maintained functional residual hearing postoperatively for at least 1 pitch.

Conclusion: Preservation of residual hearing is feasible in pediatric cochlear implant patients using standard-length electrode arrays with full insertions. These data have implications for cochlear implantation in pediatric patients who are at higher risk of progressive hearing loss than adults.

Figure 1

Technique of cochleostomy.

1. A wide facial recess approach (right ear). The Fallopian canal is skeletonized and the bone medial to (underneath) the canal is removed to expose the tectulum (bony overhang) of the round window niche. (arrowhead: stapes)

2. The tectulum is completely removed (arrow) exposing the entire round window.

3. The bone inferior to the round window is thinned to expose the “endosteum” of the scala tympani (arrowhead). The bone removal is just inferior to the annulus (arrow) of the round window membrane.

4. The thinned bone of the scala tympani is removed with rasps (arrowhead). Note that the cochleostomy is immediately adjacent to the inferior part of the round window (arrow).

5. The completed cochleostomy. The size of the opening into the inferior most part of the scala tympani may vary depending on the size of the electrode array.