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Modelling the effect of round window stiffness on residual hearing after cochlear implantation

Modelling the effect of round window stiffness on residual hearing after cochlear implantation
Modelling the effect of round window stiffness on residual hearing after cochlear implantation
Preservation of residual hearing after cochlear implantation is now considered an important goal of surgery. However, studies indicate an average post-operative hearing loss of around 20 dB at low frequencies. One factor which may contribute to post-operative hearing loss, but which has received little attention in the literature to date, is the increased stiffness of the round window, due to the physical presence of the cochlear implant, and to its subsequent thickening or to bone growth around it. A finite element model was used to estimate that there is approximately a 100-fold increase in the round window stiffness due to a cochlear implant passing through it. A lumped element model was then developed to study the effects of this change in stiffness on the acoustic response of the cochlea. As the round window stiffness increases, the effects of the cochlear and vestibular aqueducts become more important. An increase of round window stiffness by a factor of 10 is predicted to have little effect on residual hearing, but increasing this stiffness by a factor of 100 reduces the acoustic sensitivity of the cochlea by about 20 dB, below 1 kHz, in reasonable agreement with the observed loss in residual hearing after implantation. It is also shown that the effect of this stiffening could be reduced by incorporating a small gas bubble within the cochlear implant.
0378-5955
155-167
Elliott, Stephen
721dc55c-8c3e-4895-b9c4-82f62abd3567
Ni, Guangjian
f6ddc112-7d81-403a-b97a-7ecbc8fd4e59
Verschuur, Carl
5e15ee1c-3a44-4dbe-ad43-ec3b50111e41
Elliott, Stephen
721dc55c-8c3e-4895-b9c4-82f62abd3567
Ni, Guangjian
f6ddc112-7d81-403a-b97a-7ecbc8fd4e59
Verschuur, Carl
5e15ee1c-3a44-4dbe-ad43-ec3b50111e41

Elliott, Stephen, Ni, Guangjian and Verschuur, Carl (2016) Modelling the effect of round window stiffness on residual hearing after cochlear implantation. Hearing Research, 341, 155-167. (doi:10.1016/j.heares.2016.08.006).

Record type: Article

Abstract

Preservation of residual hearing after cochlear implantation is now considered an important goal of surgery. However, studies indicate an average post-operative hearing loss of around 20 dB at low frequencies. One factor which may contribute to post-operative hearing loss, but which has received little attention in the literature to date, is the increased stiffness of the round window, due to the physical presence of the cochlear implant, and to its subsequent thickening or to bone growth around it. A finite element model was used to estimate that there is approximately a 100-fold increase in the round window stiffness due to a cochlear implant passing through it. A lumped element model was then developed to study the effects of this change in stiffness on the acoustic response of the cochlea. As the round window stiffness increases, the effects of the cochlear and vestibular aqueducts become more important. An increase of round window stiffness by a factor of 10 is predicted to have little effect on residual hearing, but increasing this stiffness by a factor of 100 reduces the acoustic sensitivity of the cochlea by about 20 dB, below 1 kHz, in reasonable agreement with the observed loss in residual hearing after implantation. It is also shown that the effect of this stiffening could be reduced by incorporating a small gas bubble within the cochlear implant.

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Accepted/In Press date: 16 August 2016
e-pub ahead of print date: 30 August 2016
Published date: November 2016
Additional Information: Cochlear implant (CI) recipients typically lose about 20 dB residual hearing immediately after implantation. Our study predicts that the main source of short-term post-operative hearing loss is due to mechanical changes in the cochlea due simply to the presence of the electrode array. Our model paves the way for new methods to reduce these mechanical changes and thus preserve hearing better, with implications for widened CI candidacy and increased clinical benefit. Since publication, we have obtained preliminary agreement from one of the CI companies for possible development of an electrode array, proposed in our paper, that would solve this problem.
Organisations: Inst. Sound & Vibration Research

Identifiers

Local EPrints ID: 400523
URI: http://eprints.soton.ac.uk/id/eprint/400523
ISSN: 0378-5955
PURE UUID: 752e0551-fdb7-4c76-a7dc-c299931d7b25
ORCID for Guangjian Ni: ORCID iD orcid.org/0000-0002-9240-3020

Catalogue record

Date deposited: 16 Sep 2016 07:32
Last modified: 07 Oct 2020 02:02

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