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Cochlear implants - the future
Future developments
Neural response telemetry (NRT)

Cochlear - MAIN

Future developments
Cochlear Ltd will be focussing on:

  • lower power consumption
  • biocompatability
  • miniaturisation
  • manufacturing automation.

A new development of the Nucleus® 24 implant system is the neural response telemetry tool.

Neural response telemetry (NRT)
The NRT tool provides a simple way to directly record neural responses. Information from Nucleus NRT gives the audiologist or surgeon confirmation that the cochlear implant is effectively stimulating the hearing nerve fibres in the inner ear and all conveniently measured within minutes. This non-invasive, objective test is quicker and easier than other standard methods and does not require sedation or the use of external recording electrodes.

NRT measurements assist clinicians in selecting and optimising initial programming parameters — speeding and simplifying the programming of young children. NRT is unique to the Nucleus® 24 implant system and provides an objective measure of auditory nerve function.

During NRT testing, an electrical signal is sent to the implant electrode and the activity of the hearing nerve fibres is recorded. All of the 22 electrodes of the Nucleus cochlear implant can be measured if required. NRT can be performed during the cochlear implant surgery and at the follow-up appointments any time after surgery.

NRT testing
NRT testing (Cochlear Pty Ltd)

1. The test can be performed at any time by connecting a speech processor to a programming system running the Nucleus NRT software on a computer
2. A pulse is delivered from one electrode to the hearing nerve fibres in the inner ear.
3. The hearing nerve fibres respond to the pulse.
4. The implant system sends the response back to the computer which collects the information.

The steps are repeated to build a profile of the responsiveness of the hearing nerve fibres at different sites on the electrode array.


Improving the implant
Australian researchers are continually looking to improve the Cochlear implant. The pre-curved electrode has demonstrated better sound discrimination when tested against previous implants. Another area they will be focussing on is the possibility of making the whole device invisible. To do this the speech processor and microphone could also be implanted inside the body. Sound vibrations in the skin could be detected using a piezo-electric microphone, or the vibrations of the middle ear ossicles could be sensed and transmitted to the brain.

Another important area for research is the use of nerve growth factors to protect the hearing nerve from dieback and also regenerate the nerve. This could be used in combination with the Cochlear implant to improve effectiveness or could provide a complete pharmacological cure for sensori-neural hearing loss.

Growth of the cochlear implant industry is backed by research and development conducted in Australia and overseas. In Australia, the Cooperative Research Centre for Cochlear Implant, Speech and Hearing Research, the Bionic Ear Institute, the University of Melbourne Department of Otolaryngology and the Human Communication Research Centre are all involved in cochlear implant research. Ongoing research aims to:

  • improve the cochlear implant by increasing understanding of how electrical stimulation by the cochlear implant is perceived by the users, and how best to present speech information to them
  • minimise the impact of noise on the clarity of the speech signal provided by the cochlear implant
  • maximise the benefit that young children gain from the cochlear implant
  • improve the understanding of how the auditory nerve fibres and brain respond to the electrical stimulation of the cochlear implant, including the testing of newer modes of electrical stimulation
  • develop new speech processing strategies through computer simulations of the response of the auditory system to acoustic and electrical stimulation
  • improve the design of the cochlear implant electrodes
  • improve pre- and post-operative clinical management
  • improve surgical procedures
  • develop a technique for direct electrical stimulation of the brainstem for deaf people who are unable to use the cochlear implant - particularly those with few residual auditory nerve fibres
  • make the cochlear implant suitable for people who still have some hearing
  • combine cochlear implant and hearing aid strategies, so that people — particularly those with some hearing — can continue to benefit from a hearing-aid once they have a cochlear implant
  • investigate the use of two microphones — one behind each ear — to improve the perception of speech in noisy environments
  • develop a cochlear implant or hearing aid that resides entirely under the skin. The first stage of this research is the development of a microphone system that can be completely implanted
  • and develop ways of initiating auditory nerve regeneration to enhance the effectiveness of existing cochlear implant systems. http://www.science.org.au/nova/029/029box03.htm
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