Effects of loss of residual hearing on speech performance with the CI422 and the Hybrid-L electrode.

Objective: Preservation of residual low-frequency hearing has become a priority in cochlear implantation. The purpose of this study was to compare rates of hearing preservation and effects on performance of loss of low-frequency acoustic hearing with two different length electrodes.

Study Design: Retrospective chart review.

Setting: Tertiary Care Hospital.

Patients: Twelve patients were implanted with the CI422 a slim-straight electrode; the second group consisted of 10 patients implanted with the Hybrid-L, a shorter hearing preservation electrode.

Main Outcome Measure: Audiometric thresholds and speech perception measures.

Results: At 1 year, 3/10 (30%) patients with the Hybrid-L and 7/12 (58%) patients with the CI422 lost residual acoustic hearing resulting in a profound hearing loss in the implanted ear. In comparing these patients in particular, mean CNC words in the implanted ear were 72% in the CI422 electrode group and 15% in the Hybrid-L electrode group at 1 year (P = 0.03). While hearing preservation rates with the Hybrid-L tended to be better, among recipients who lost residual hearing, speech perception was better in those with the longer CI422 electrode.

Conclusions: With emphasis on preservation of residual hearing, patients need to be counseled regarding possible outcomes and options should loss of residual hearing occur following implantation. While shorter electrodes may have better rates of hearing preservation, the patients with the longer straight electrode in our study had significantly better speech understanding following the loss of residual hearing.