London Cochlear Implant Clinic

 

Who Can Benefit from Cochlear Implantation?

Traditionally there are two groups of patients who have been found to benefit from a CI. 

  1. Children born with a profound hearing loss
  2. Adults who have had hearing and have lost it.

There is now a third group, the so-called non-traditionals, adults and older children born with severe to profound hearing loss who have had some benefit from conventional hearing aids.

The benefit derived from a CI is to a large extent dependent on the brain and in particular the hearing part of the brain – the auditory cortex.  In a new born baby the brain is like a sponge that soaks up information.  How the brain develops depends on what stimulation it receives.  How the auditory cortex grows and develops therefore depends on how much information comes along the hearing (auditory) nerve in the first few years of life.  In a normal child with normally functioning ears the sounds and voices all around the child will be picked up by the ears and result in a lot of stimulation along the auditory nerves.  This stimulation causes large parts of the brain to be “opened up” for hearing.  In a child with a hearing loss there will be reduced stimulation along the auditory pathway and therefore less of the brain will be “opened up” for hearing.  This can be overcome in cases of lesser hearing loss by the early fitting of hearing aids which will boost the stimulation of the hearing pathways.  After the age of about 4 years these pathways are fixed and no amount of stimulation after this will enable them to “open up”.  In normal circumstances the speech and language parts of the brain develop as a result of development of the auditory cortex ie children go from hearing words to trying to copy them.  If they are unable to hear the words they can not copy them and therefore speech development is affected.

Therefore it is essential that all children have their hearing checked at birth (as happens in the UK with the National Neonatal Hearing Screening).  Any that have a degree of hearing loss can then be fitted with aids at the earliest opportunity to enable central auditory development.  In those children that have a severe to profound loss hearing aids may not be able to provide sufficient stimulation and therefore cochlear implantation should be considered at the earliest opportunity.  In practice this usually occurs around the age of 1 year.

In adults who have had normal hearing for the first four years of life the central auditory pathways and speech and language areas will have developed normally therefore losing their hearing at a later date is less of a problem since the hearing part of the brain is fully formed and does not (to a large extent) deteriorate over time.

For the non-traditionals it all depends on how much stimulation their developing brain had in the first four years of life.  As a basic rule of thumb, if they have developed easily understandable speech it is likely that they could derive benefit from a CI.