Bilateral sequential cochlear implantation in the congenitally deaf child: Evidence to support the concept of a ‘Critical Age’ after which the second ear is less likely to provide an adequate level of speech perception on its own

Abstract

This study attempts to answer the question of whether there is a 'critical age' after which a second contralateral cochlear implant is less likely to provide enough speech perception to be of practical use. The study was not designed to predict factors that determine successful binaural implant use, but to see if there was evidence to help determine the latest age at which the second ear can usefully be implanted, should the first side fail and become unusable.Outcome data, in the form of speech perception test results, were collected from 11 cochlear implant programmes in the UK and one centre in Australia. Forty-seven congenitally bilaterally deaf subjects who received bilateral sequential implants were recruited to the study. The study also included four subjects with congenital unilateral profound deafness who had lost all hearing in their only hearing ear and received a cochlear implant in their unilaterally congenitally deaf ear. Of those 34 subjects for whom complete sets of data were available, the majority (72%) of those receiving their second (or unilateral) implant up to the age of 13 years scored 60 per cent or above in the Bamford Kowal Bench (BKB) sentence test, or equivalent. In contrast, of those nine receiving their second or unilateral implant at the age of 15 or above, none achieved adequate levels of speech perception on formal testing: two scored 29 per cent and 30 per cent, respectively, and the rest seven per cent or less.A discriminant function analysis performed on the data suggests that it is unlikely that a second contralateral implant received after the age of 16 to 18 years will, on its own, provide adequate levels of speech perception. As more children receive sequential bilateral cochlear implants and the pool of data enlarges the situation is likely to become clearer.The results provide support for the concept of a 'critical age' for implanting the second ear in successful congenitally deaf unilateral cochlear implant users. This would argue against 'preserving' the second ear beyond a certain age, in order to use newer models of cochlear implant or for the purpose of hair cell regeneration and similar procedures in the future. The results suggest a new and more absolute reason for bilateral implantation of congenitally deaf children at an early age.

Bilateral cochlear implants in children: Effects of auditory experience and deprivation on auditory perception

“…It may seem reasonable to define an age at which bilateral implantation should not proceed. However, while benefits from bilateral implantation in children can decline with age [13, 59, 71–77], there are many associated time-based issues to address. Consider for example, the suggestion by Graham and colleagues that adolescents should not be provided with a second cochlear implant [77].…”

“…However, while benefits from bilateral implantation in children can decline with age [13, 59, 71–77], there are many associated time-based issues to address. Consider for example, the suggestion by Graham and colleagues that adolescents should not be provided with a second cochlear implant [77]. The adolescent group may be amongst the poorest candidates based on abnormal cortical maturation, poor speech perception in the newly implanted ear compared to the first, inconsistent use of the second device, and inability to hear binaural timing cues [34, 77, 78].…”

Strengthening of Hearing Ear Representation Reduces Binaural Sensitivity in Early Single-Sided Deafness

“…Here, the outcome in speech performance for the second-implanted ear in sequential implantation is significantly dependent on interimplant delay [Zeitler et al, 2008;Graham et al, 2009;Illg et al, 2013]. Waiting for more than 3-5 years with the second cochlear implantation does significantly decrease the benefit of the therapy on the second ear [Zeitler et al, 2008;Graham et al, 2009;Gordon et al, 2013;Illg et al, 2013].…”

Integrative Neuronal Functions in Deafness

“…Finally, reorganization of aural preference (dominance) in consequence to unilateral hearing experience via a cochlear implant, measured with onset latencies and peak amplitudes of local field potentials, showed a sensitive period of 3 months , demonstrating that different functions and structures show different sensitive periods. This seems to be the neuronal mechanism of the observation that in subjects implanted binaurally, delaying the second implantation decreases performance on the second-implanted ear (Graham et al, 2009).…”