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Auditory brainstem implant
The hearing implant centre at St Thomas' Hospital, in association with Kings College Hospital, offers auditory brainstem implants to children for whom cochlear implantation is not an option. There are only two specialist centres in the UK that have been commissioned by NHS England to offer this treatment to children under the age of 5.
The paediatric auditory brainstem implant team is a specialist multidisciplinary team providing highly skilled care throughout your child’s assessment, inpatient stay and follow up after surgery.
The outpatient appointments both before and after surgery are carried out at the hearing implant centre at St Thomas’ Hospital while the inpatient stay and operation is carried out at Kings College Hospital. The team work across both sites, so it is the same team supporting you and your child throughout their journey.
How does the ear work?
The ear is made up of three parts, the outer (external) ear, the middle ear and the inner ear.
Diagram showing how the ear works
Image © Scott Maskell
- The part we can see is the outer ear, which also includes the ear canal. It functions to capture sound energy and funnel it to the ear drum. When the sound energy reaches the ear drum it causes the ear drum to move and vibrate.
- There are three tiny middle ear bones connected to the ear drum. When the ear drum vibrates, it causes the three bones to vibrate as well.
- As these bones vibrate, they push against the inner ear (cochlea). The cochlea is a fluid filled organ which contains many sensory cells called hair cells. As the three bones push against the cochlea the fluid inside the cochlea begins to move, which causes the hair cells to move and bend. The hair cells contact the hearing nerve (auditory nerve) and as they move and bend they stimulate the nerve. The nerve then sends the message to the brain for processing.
In the case of severe to profound deafness, the hair cells and part of the hearing nerve are affected. This is called sensorineural hearing loss. This damage prevents the sound signals from being transmitted to the brain.
Watch a video explanation of how the ear works.
See more useful information about hearing implants.
What is an auditory brainstem implant (ABI)?
The auditory brainstem implant (ABI) is an electronic device that is intended to restore a degree of hearing sensation for individuals with missing or damaged cochlea and/or cochlear nerves. Historically ABI’s have been used for adults who have lost their hearing following the removal of acoustic tumours, however in recent years ABI’s have been offered to children when a cochlear implant is not an option.
How does the ABI work?
The ABI consists of two parts.
- One part is surgically implanted under the skin on the cochlear nucleus in the brainstem. This consists of an electrode array (placed on the cochlear nucleus) and a receiver stimulator (behind the ear under the skin).
- The other part is worn externally behind the ear or as a body worn configuration and is referred to as a speech processor. It is worn with a headpiece which is held in place on the head by a magnet.
The external parts of the implant can be removed at any time, for example when sleeping or swimming and bathing.
The internal device electrically stimulating the cochlear nucleus in the brainstem to produce a sensation of sound, it is powered by the external speech processor.
- Sound is picked up by microphones in the external speech processor
- The speech processor filters and analyses the sounds and codes it into digital signals
- The coded signals are sent along the cable to the transmitting coil
- The transmitting coil sends the coded signals to the implant underneath the skin
- The implant delivers the signals to the electrodes on the cochlear nucleus
- The electrodes stimulate the cochlear nucleus, producing stimulation that may be interpreted as sound in the auditory cortex of the brain
Placement of the ABI
Placement of the ABI
Image courtesy of Med EL
Who might be suitable for an ABI?
Individuals will be assessed by a specialist multidisciplinary team who will consider options available to support hearing. If Cochlear Implants are not an option then an Auditory Brainstem Implant may be considered.
Where can my child be assessed for an ABI?
In the UK there are two hearing implant centres that are commissioned to provide paediatric ABI’s for children under the age of 5 years old: St Thomas’ hearing implant centre (London ABI programme) and the Richard Ramsden centre for hearing implants (Manchester).
What is involved in the surgery for ABI?
The surgery consists of placing of the electrode array onto the cochlear nucleus in the brainstem, and placement of the receiver stimulator over the skull bone behind the ear. The optimal placement of the electrode array is guided by activating electrodes during the placement and record the brain’s response. The operation lasts several hours.
What are the risks of having ABI surgery?
You will meet with the surgeons who will discuss these with you.
What are the outcomes of ABI’s
The degree of benefit cannot be guaranteed and varies from child to child. Published research studies relate to very small numbers of patients. Outcomes relate to a range of factors including: surgical outcome (placement of electrodes), number of electrodes active and additional needs (cognitive ability) of the child. In cochlear implantation there is strong evidence of age of implantation impacting on outcomes. Theoretically age is likely to be another factor that contributes to outcomes post ABI.
Your child’s progress with the ABI may be very slow and it may take months and years before we can see how much help the ABI can give and if this translates into any functional use of hearing. It is essential that a sign based communication system is developed and used consistently within the family to support communication between parents and child. It is likely that signing will remain the dominant part of the child and families communication system in the longer term even with an ABI in use.
What is the longer term care for my child following Auditory Brainstem Implantation?
Once your child has an ABI they will be required to have regular monitoring at the Hearing Implant Centre for life.
What can I do to maximize my childs progress with their ABI?
It is vital that you establish consistent use of the speech processor as soon as possible. The speech processors should be worn by the child all waking hours.
Where does surgery take place ?
Your child will be admitted to Lion Ward at King's College Hospital.