Variable long-term outcomes from cochlear implantation in children with hypoplastic auditory nerves

Abstract

This paper describes the outcomes in six children with hypoplastic cochlear nerves, demonstrated on magnetic resonance imaging who were selected for implantation because they had clear responses to sound, with hearing aids. In four of the six children the internal auditory canals were abnormally narrow; however in the remaining two the internal auditory canals were of normal width. After activation of their devices, all six children had auditory thresholds within the normal range for implanted congenitally deaf children. However the progress of all these children after 2 to 6 years of implant use turned out to be disappointing. Five of the children developed only the ability to detect the presence of sound, and were unable to discriminate accurately between speech sounds. They remain at Category of Auditory Performance (CAP) level 2: sign is their primary mode of communication. All five children also remain at Speech Intelligibility Rating (SIR) level 2, with unintelligible connected speech. The sixth child was able to develop some understanding of common phrases through listening alone, however he remains at CAP level 4 and his SIR level also remains at 2. The benefit of cochlear implantation in this group of children is likely to be considerably restricted. In specific cases it may be appropriate to offer a cochlear implant to a child with hypoplastic auditory nerves but careful counselling of the family about likely outcomes is essential.