The influence of residual high-frequency hearing on the outcome in congenitally deaf cochlear implant recipients.

Abstract

Objective: To show that congenitally deaf children who receive a cochlear implant between 10 and 15 years of age find it significantly more difficult to learn the new signal, and that a history of sound detection at high frequencies with hearing aids is predictive of better outcomes in these children.

Study design: A retrospective study using a within-subjects design.

Setting: Children's Cochlear Implant Centre, Sydney (CCIC), Royal Prince Alfred Hospital, and the New Children's Hospital in Westmead are tertiary referral centers.

Patients: Forty-five congenitally deaf patients were grouped according to their age (in years) at implantation into group 1 (aged 10-15), group 2 (aged <10), group 2a (aged 6-9), and group 2b (aged 3-5). Within each group, individuals with previous hearing between 2 and 4 kHz before receiving a cochlear implant were identified, and their mean results were compared with those in their respective age-matched groups.

Interventions: Surgical implantation, intensive weekly habilitation at the CCIC.

Main outcome measures: Speech perception, speech production, and language measures were compared. Questionnaires and telephone interviews were conducted.

Results: Group 2 (age <10 years) consistently outperformed group 1 (10-15 years) on all outcome measures, and most of them learned to converse without lipreading. In group 1, children with previous aided hearing at high frequencies displayed exceptional gains in speech perception and speech production, with reduced dependence on lipreading. Previous high-frequency hearing does not benefit group 2.

Conclusions: Implant recipients aged 10 to 15 years experience more difficulty than younger children during the initial periods of device use. A history of high-frequency hearing before implantation in these individuals correlates with more rapid improvement.