The Role of Hearing Preservation on Electrical Thresholds and Speech Performances in Cochlear Implantation

OBJECTIVE: The purpose of this study was to verify if the preservation of residual hearing after cochlear implantation in classic adult cochlear implant candidates implanted with a perimodiolar electrode correlates with the electric thresholds and with speech perception measures. STUDY DESIGN: Retrospective study. SETTING: Cochlear Implant Center at a tertiary referral University Hospital. PATIENTS: Forty-one patients with cochlear implant were involved in our study. They were subdivided into 2 groups according to the average preoperative hearing loss at the frequencies of 125 and 250 Hz (low-frequency pure tone average [LFPTA]). Group A included 21 patients with a mean LFPTA of 90 dB HL or lower; group B included 20 patients with a mean LFPTA of greater than 90 dB HL. They underwent 12 months' follow-up after cochlear implantation, including standard audiologic investigation, speech discrimination tests, and electrical measurements. RESULTS: No significant differences were found in speech perception tests among groups. In group A, hearing was preserved in 8 (group A1) and was lost in 13 patients (group A2); the postoperative LFPTA was significantly better (p < 0.0001) in A1. Group A1 patients present significantly higher C values (p < 0.0001) than the other 2 groups, and the dynamic range was therefore significantly wider (p < 0.001). CONCLUSION: Preservation of residual hearing should be attempted in all cases. In fact, although effects on the speech perception are not evident with the standard evaluation, larger electrical dynamic range can be achieved and may represent a sign of cochlear "well-being," potentially allowing a more complex electric stimulation of the nerve.