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.

Abnormal Cochleovestibular Anatomy and Hearing Outcomes: Pediatric Patients with a Questionable Cochleovestibular Nerve Status May Benefit from Cochlear Implantation and/or Hearing Aids

“…An abnormal CVN has been reported in patients in whom the cochlear aperture size is normal or in patients with normal size IAC, or in patients with no associated cochleovestibular malformation [Glastonbury et al, 2002;Adunka et al, 2006Adunka et al, , 2007Buchman et al, 2006;Bradley et al, 2008;McClay et al, 2008;Carner et al, 2009;Warren et al, 2010;Kutz et al, 2011;Pagarkar et al, 2011;Colletti et al, 2014]. Our data highlight the association of normal cochleae, normal cochlear apertures, and normal caliber IAC with severe CVN abnormalities.…”

“…Recent studies have reported an improvement in auditory skill development and sound awareness in children who had been diagnosed with CVN deficiency and received a CI [Casselman et al, 1997;Ito et al, 1999;Acker et al, 2001;Govaerts et al, 2003;Zanetti et al, 2006;Bradley et al, 2008;Oker et al, 2009;Kang et al, 2010;Warren et al, 2010;Buchman et al, 2011;Kutz et al, 2011;Young et al, 2012]. Clearly, some nerve fibers were available to transmit auditory signals to the brainstem [Casselman et al, 1997;Ozdoğmuş et al, 2004;Warren et al, 2010].…”

“…Some children, thought to have absent CVN, nonetheless seemed to benefit from a CI and/or exhibit measurable unaided hearing thresholds [Casselman et al, 1997;Ito et al, 1999;Acker et al, 2001;Govaerts et al, 2003;Zanetti et al, 2006;Bradley et al, 2008;Kang et al, 2010;Warren et al, 2010;Buchman et al, 2011;Kutz et al, 2011;Pagarkar et al, 2011;Zhang et al, 2012;Vincenti et al, 2014;Wu et al, 2014]. The Birman classifications have the benefit of directly cataloging what is seen on imaging and providing an association with outcome, lending it diagnostic usefulness.…”

Editorial: ‘Auditory neuropathy’ and cochlear implantation — myths and facts

“…In contrast, congenitally deaf children with OHC survival who also had structural abnormalities of the cochlear nerve rarely achieved any open set speech perception using cochlear implants even after two years of training after implant surgery (Bradley et al, 2008).…”

Assessment of cochlear implant candidacy in patients with cochlear nerve deficiency using the P1 CAEP biomarker

“…While cochlear implantation in children has become a fairly routine procedure, there remain cases where implant candidacy decisions are difficult to make using existing evaluation procedures. Among these cases are children with cochlear nerve deficiencies (CND) (Bradley et al, 2008; Buchman et al, 2006; Govaerts et al, 2003; Walton et al, 2008; Zanetti et al, 2006). Auditory nerve abnormalities or hypoplasias may present in several forms.…”