A cochlear implant is a device used to provide the sensation of sound to the pro foundly deaf. It includes an implantable receiverIstimulator module with an electrode array (placed either inside or outside the cochlea), a microphone and a speech processor.
The Nucleus 22 channel cochlear implant is the current market leader. Development of the technology continues to be rapid.
Profound deafness affects approximately 10,000 to 12,000 adults and 1,400 children in Australia. From this population there is a pool of approximately 2,000 adults and 570 children who are candidates for implantation.
Over 300 implantation procedures have been conducted in Australia and between 5,000 and 6,000 worldwide.
The selection criteria to assess the suitability of profoundly deaf adults wishing to receive a cochlear implant are settled, with the possible exception of the criterion for the threshold hearing level applied to severely deafened adults.
Radiological examination excludes about 30 per cent of potential candidates for implantation. Further refinement of radiology techniques and further under standing of the disease process of both bacterial and viral meningitis would aid implantation teams in deciding when and if the surgery should be performed.
Nearly all recipients of cochlear implants derive benefit through improved speech perception and by being able to hear environmental sounds. However, individuals derive varying degrees of benefit. Some recipients achieve open speech recognition on sound-only inputs, while others use the device as supple mentation to lip-reading. Candidates must be extensively counselled as to the likely outcome of their surgery and rehabilitation.
Benefits of the technology for pre-lingually deafened children are now emerging, with some achieving open-set speech perception.
The use of cochlear implants in children continues to be controversial, with the Australian Association for the Deaf opposing both the implantation of pre- and post-lingually deafened children.
The rehabilitation associated with the program makes a major contribution to the overall cost. However, offsetting savings are derived through the mainstreaming of children within the education system.
Estimates of the cost of this tre tment are approximately $35,000 and $25,915 for the first year for four-year-old children and adults respectively.
Preliminary consideration of cost utility of the technology suggests that it is reasonable value for money.
In Australia an overall complication rate following surgery of approximately five per cent has been observed. The most common surgical complication is infection/necrosis of the skin flap covering the receiverIstimulator module.
While some trauma occurs on insertion of the electrode array, continued electrical stimulation does not deplete the numbers of ganglion cells.
Hearing-impaired people also derive benefit from the use of tactile aids as supplementation to lip-reading and hearing aid inputs. However, the place of tactile devices may be limited by the competition from use of cochlear implants and the amount of rehabilitation required.
As the numbers of cochlear implant recipients increase, further demands for au diology and other support services may need to be met. Attention may need to be given to the geographical distribution of these services.
Further research is required in a number of areas, including the disease processes that cause deafness, assessment of the level of benefit from cochlear implants and the costs incurred by society resulting from profound deafness.
Selection of candidates for cochlear implants
Rehabilitation following surgery
Measurement of outcome
Adverse effects associated with cochlear implants
Attitudes to cochlear implants by the Deaf Community and educators
Utilisation and cost of cochlear implants
Preliminary economic assessment
Tactile devices and cochlear implants
Current status and future research needs
Appendix 1: Australian Association of the Deaf Policy on the cochlear implant
Appendix 2: Auslan, Signed English and the education system
End matter: References; Acknowledgements