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.