Horizontal sound localization in children with bilateral cochlear implants: effects of auditory experience and age at implantation

Abstract

Objective: To study sound localization performance in relation to auditory experience and age at implantation in children with bilateral cochlear implants.

Study design: Clinical study.

Setting: University hospital.

Patients: Sixty-two sequentially and 4 simultaneously bilaterally implanted children participated in this clinical sound localization study, at a median age of 5.6 years. They underwent sequential implantations at median ages of 1.9 and 4.2 years, respectively. Simultaneous implantations were performed at a median age of 2.0 years.

Methods: Localization performance was measured with pink noise presented in random order from 5 loudspeakers in the frontal horizontal plane. Twenty-one subjects participated in repeated testing.

Main outcome measure: Sound localization performance as quantified with an Error Index.

Results: On group level, bilaterally implanted children pinpointed the sounding loudspeaker in the frontal horizontal plane. Sound localization performance improved significantly with increasing bilateral cochlear implant experience, as observed in the entire study group and intraindividually, albeit large interindividual variability existed. Regression analyses in the entire study group and in the sequentially implanted children did not reveal any relationship between sound localization performance and ages at first and second implantation, interimplant interval, or age. However, second implantation before 4 years of age contributed to faster sound localization improvement with increasing bilateral cochlear implant experience.

Conclusion: Median perceived azimuths coincided with presented azimuths. We suggest that listening experience after bilateral cochlear implantation affects sound localization performance, possibly owing to the ongoing stimulus-driven maturation of the central auditory system. The amount of time listening with bilateral implants has methodologic implications on sound localization assessment in bilaterally implanted children.