Two Ears are Better than One

Bilateral Cochlear Implantation

Bilateral implantation is cochlear implantation in both ears. Hearing with two ears, also called binaural hearing, has distinct advantages such as improved speech understanding in noise, better speech recognition and sound localization1. In general, it can be said that “stereo” hearing (with two ears) is less strenuous than “mono” hearing (with one ear). MED‑EL pioneered bilateral cochlear implantation in 1996 and has since accumulated leading experience in this field.

Bilateral Implants in Children
Implanted children are a unique group. Unlike adults who may have had hearing and then lost it, children usually learn to listen using only the sound from the cochlear implant. It is common knowledge that it is more difficult to learn certain things later in life – such as learning second languages – and it has long been understood that there is a “critical window” of time early in a child’s life when he or she has the best chance of making use of sound for the development of language. For example, studies have illustrated that children who received their bilateral implants prior to age 3½ were able to make the most of the brain’s ability to learn.2,3,4

In a retrospective study using a parent questionnaire5, hearing quality in children was found to be significantly better following bilateral implantation. Bilaterally implanted children respond much faster in group situations; they react more quickly and appropriately in everyday situations and acquire language spontaneously. Additionally, auditory effort is reduced and, according to parents, the children are less tired after school or kindergarten. Parents of bilaterally implanted children often report clear benefits in speech understanding and an increase in their child’s self-confidence.

Bilateral Implants in Adults
The distinct advantages of bilateral implantation have also been well documented in adults. Several studies have reported restored ability to localize sounds6,7,8,9 and that adult bilateral users have demonstrated all of the binaural effects that normal individuals enjoy.10,11,12,13 Furthermore, the age of implantation in adults appears to have no bearing on the performance of the cochlear implant14 meaning that older adults can also obtain the same benefits as younger implanted adults.

Surgery
Most surgeons agree that implanting a second device is really no different than implanting the first. Candidacy requirements are the same, surgical risks should not vary, and potential benefits/limitations of one implant apply equally to two implants. However, your implant team may have varying recommendations or opinions regarding the timing of surgery. Bilateral implants can be placed either simultaneously or sequentially depending on your decision and consultation with your surgeon.

If you are considering bilateral implantation for yourself or your child, we recommend that you talk to your implant center and implant team. They will be able to help you establish appropriate expectations based on your unique history and any experience you've already had with one cochlear implant. It is also very helpful to talk with other bilateral implant users, therefore we have created a website that allows you to connect, share experiences and chat live with other MED‑EL bilateral recipients. Connect now at www.hearpeers.com

The MED‑EL Advantage
A variety of technical features make MED‑EL cochlear implant systems especially well suited for bilateral implantation. In particular, the combination of Fine Structure Processing and specially designed flexible electrodes that allow deep insertion into the cochlea provides users with a maximum amount of acoustic information. Fine Structure Processing refers to the amount of information that the implant can deliver to the ear, and how detailed that information is.

Research has shown that the fine structure of a sound is the main carrier of timing information facilitating localization of sound sources in space. Fine Structure Processing more closely represents the function of the normal cochlea and has been found to be beneficial in speech understanding15. Another innovative feature is the ability to use one FineTuner remote control unit for both implants, making it user-friendly for people of all ages. Finally, listening accessories allow bilateral implant users to access stereo sound when listening to other devices, like an MP3 player.
  1. Laske R.D., et al., 2009. Subjective and Objective results after bilateral cochlear implantation in adults. Otol Neurotol. Vol. 30. pp.313-318
  2. Sharma, A., Dorman, M. F., Kral, A. (2005). The influence of a sensitivity period on central auditory development in children with unilateral and bilateral cochlear implants. Hearing Research, 203, 134-143.
  3. Sharma, A., Gilley, P., Martin, K., Roland, P., Bauer, P., Dorman, M. (2007). Simultaneous versus sequential bilateral implantation in young children: Effects on central auditory system development and plasticity. Audiological Medicine, 5(4), 218-223.
  4. Sharma, A., and Dorman, M. (2006). Central Auditory Development in Children with Cochlear Implants: Clinical Implications. Advances in Otorhinolaryngology. Vol 64. Basel: Karger pp 66-88.
  5. Winkler F et al., The Wurzburg questionnaire for assessing the quality of hearing in CI children (WH-CIK ). J Laryngorhinootologie. 2002 Mar:81(3):211-216.
  6. Nopp, P., Schleich, P., D’Haese, P. (2004). Sound localisation in bilateral users of MED-EL COMBI 40/40+cochlear implants. Ear and Hearing, 25, 205-214.
  7. Schoen, F., Mueller, J., Helms, J., Nopp, P. (2005). Sound localisation and sensitivity to inter-aural cues in bilateral users of the MED-EL COMBI 40/40+ cochlear implant system. Otology and Neurotology, 26, 429-437.
  8. Senn, P., Kompis, M., Vischer, M., Häusler, R. (2005). Minimum audible angle, just noticeable interaural differences and speech intelligibility with bilateral cochlear implants using clinical speech processors. Audiology and Neurotology,10, 342-352.
  9. Grantham, D., Ashmead, D., Ricketts, T., Labadie, R., Haynes, D. (2007). Horizontal-plane localisation of noise and speech signals by postlingually deafened adults fitted with bilateral cochlear implants. Ear and Hearing, 28(4),524-41.
  10. Müller, J., Schön, F., Helms, J. (2002). Speech understanding in quiet and noise in bilateral users of the MED-EL COMBI 40/40+ cochlear implant system. Ear and Hearing, 23, 198 206.
  11. Schön, F., Müller, J., Helms, J. (2002). Speech reception thresholds obtained in a symmetrical four loudspeaker arrangement from bilateral users of MED-EL cochlear implants. Otology and Neurotology, 23, 710-714.
  12. Schleich, P., Nopp, P., D’Haese, P. (2004). Head shadow, squelch and summation effects in bilateral users of the MED-EL COMBI 40/40+ cochlear implant. Ear and Hearing, 25, 197-204.
  13. Litovsky, R., Parkinson, A., Arcaroli, J,. Sammeth C. (2006). Simultaneous bilateral cochlear implantation in adults: a multicentre clinical study. Ear and Hearing, 27(6), 714-31.
  14. Noble W., et al., 2009. Younger- and Older-Age Adults with Unilateral and Bilateral Cochlear Implants: Speech and Spatial Hearing Self-Ratings and Performance. Otology & Neurotology. pp.1-9 
  15. Harnisch et al. Performance of long-time Tempo+ users is improved after switching over to the OPUS2 speech processor. Presented at the 9th European Symposium on Paediatric Cochlear Implantation, Warsaw, 2009

* FSP is not indicated for use by pre-lingual children in the US.

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