Just occasionally paediatric audiologists, particularly those who work in cochlear implant programmes, will meet a child who has been born without cochlea or auditory nerves, or other abnormality of the inner ear that makes a hearing aid or cochlear implant useless. This diagnosis has just been given to the parents of a 4 month old boy and other parents in the same situation have shared their experiences on the NDCS Parent Place forum. This must be devastating for parents who have held out hope for a technological miracle that will help their little one access hearing and speech. Some parents have been researching the option of an auditory brainstem implant (ABI).
An ABI works in a similar way to a cochlear implant and in fact the external parts look just like a cochlear implant. But instead of electrodes inserted into the cochlea, the electrodes stimulate the auditory brainstem directly, bypassing the ear and auditory nerve. This makes the procedure more invasive than that for a cochlear implant.
ABI’s are used most often for adults who have suffered trauma to their hearing nerve which means that it is no longer useful and Manchester Cochlear Implant Programme have implanted more than 50 adolescents and adults in this group. Trauma usually occurs during surgery to remove a tumour from the hearing nerve. Once the hearing nerve has been damaged in this way the person would not benefit from hearing aids or a cochlear implant because the sounds could not transfer from the ear to the brain along the nerve. ABI has only been used for adults who have previously had hearing and use speech to communicate. Where a cochlear implant stimulates different points corresponding to different frequencies along the cochlea, the brainstem does not have this separation of frequencies so the ABI cannot separately stimulate different groups of nerves corresponding to distinct frequency ranges. The ABI therefore provides a sensation of hearing that can help aid lip-reading and provide other clues used in spoken communication (for example rhythm and speed of speech) but these adults are unable to use the ABI alone to hear speech without the additional help of lip-reading etc.
Although ABI’s have been available in the UK for the last decade only a handful of children have had the procedure here. The outcomes for children are more variable than for children who use a cochlear implant – they may only offer access to louder and environmental sounds although some are accessing speech. Like cochlear implants the emerging evidence is that the earlier implantation takes place, the better the outcomes for the child. ABI’s have been used in cases when there is no cochlea (and therefore nothing to implant with a cochlear implant), when the cochlea has suffered extensive damage (such as following meningitis) and an electrode can’t be inserted into the cochlea, and when there is no auditory nerve.
It is understandable that most hearing parents opt for cochlear implants for their deaf child – opening up options for their child to develop spoken language as well as BSL and potentially other languages too. For parents of children in the ABI candidature group it appears that most have instead been opting to concentrate on developing British Sign Language as their child’s first language without technological intervention but there is increasing interest in the option of an ABI.
Further information on auditory brainstem implants including further reading links and research go to the NDCS webpage.
Update 4th July 2012
Hope for Hearing is a trust that was set up to raise funds for 22 month old Evie’s ABI which was implanted in Italy in June 2012. You can read more about her story and her family’s experiences of the assessment and surgery etc.
amazing amelia is now 3 years old and had her ABI at 2 years 8 months. Read her blog and watch videos of her progress.
Update 30th July 2012
The Fight for Finn is a trust that was set up to raise funds for 18 month old Finn’s ABI which was implanted in Italy in July 2012. You can read more about his story and his family’s experiences of the assessment and surgery etc.
