What is a Bone Anchored Hearing Aid ("BAHA")
This is a special type of hearing aid recommended when the use of standard hearing aids (which fit into the ear canal) is not possible or difficult.The BAHA is extremely comfortable to use (in most cases the wearer is unaware of its presence) and is cosmetically good.
I typically recommend this type of implant and hearing aid for teenagers and adults. I have used the BAHA for younger children too, and while the hearing is excellent with this,we have found that younger children are prone to infections in the skin around the implant.
It has several components. An internal component is fitted underneath the skin behind the ear. This called the 'flange fixture'.This is made of 100% pure titanium, which integrates into the bone under the skin behind the ear. Human bone cells do not recognise the titanium as a foreign substance, which therefore actually grow firmly onto the titanium surface of the flange fixture. This is what makes the transfer of sound vibrations possible. The second component is called an 'abutment' which appears to sit mainly on the outside of the skin behind the ear but passes through a small hole in the skin into the flange fixture. This is what the hearing aid attaches to.
Younger children (if suitable) have both parts of the implant inserted seperately, 3 months apart, but adults and children 4 years and over may have both parts inserted simultaneously.
The actual hearing aid clips on and off the abutment- and does not rest on the ear.
BAHA implant behind the ear
BAHA hearing aid behind the ear
(attached to the implant)
Implant behind the ear, 12 days post op (courtesy of Cochlear Ltd)
Images of BAHA hearing aids. For children, they can also be customised and decorated.
Who is Suitable for a Bone Anchored Hearing Aid?
This is suitable for adults and children. Those who may benefit include:
- > Those who have "middle ear" hearing loss because of absence of the ear canals or because of birth malformations of the middle ear.
- > Those with persisting ear discharge or weeping from the ears secondary to long term ear infection which may prevent them from using a standard hearing aid. This may include people who have had "mastoid surgery" in the past.
- > Adults and children who are deaf in one ear (single sided hearing loss). The "BAHA" transfers the sound from the affected side into the normal hearing ear and is superior to other types of aiding systems for single sided hearing loss. This may apply to those who have had a progressive loss of hearing in one ear, a sudden hearing loss, a traumatic injury to the ear, or following acoustic neuroma surgery.
Usually, for those with hearing loss in only one ear, I recommend trialling a BAHA aid attached to an elastic headband for a period of a few days or a week, and in addition a hearing test with the aid both on and off. This often will show a significant difference, pleasingly suprising to the wearer.
Sometimes we recommend a period of time of classroom observation both with and without the BAHA aid, which is evaluated by the classroom teacher, or an advisor on Deaf and Hearing Impaired Children (from the Ministry of Education)
What is the Procedure Used to Insert a Bone Anchored Hearing Aid?
This is a simple and brief procedure performed under a general anaesthetic in children, but usually only local anasthetic is needed for adults. Two stages under general anaesthetic (spaced 3 months apart) are required in children aged under 4-5 years.
The small implant is inserted through the skin into the bony area behind the ear. This takes only 30 minutes or so to do and discomfort afterwards is minimal. A small amount of hair needs to be shaved and a 2 cm incision is made to enable the implant to be inserted. (In the past, a skin graft or skin thinning was required, but this is no longer necessary.) in young children, I sometimes insert a spare implant which remains buried under the skin, but which may be easily used in the future if ever needed. A white "healing cap" is attached to the implant abutment, and holds an antibiotic coated ribbon gauze dressing underneath it for 7 days. After that, the healing cap and dressing are removed. and the wound underneath will be healed.
The hearing aid is able to be used 6 weeks post op, in adults and a week after the second stage in children.
This small white "cap" is applied to the implant abutment for a week after surgery. It holds a dressing underneath it.
Another view of how the implant abutment looks within the hair, post operatively.
What is the Post Operative Care Required?
The abutment needs to be cleaned on a twice weekly basis with a small very soft "toothbrush" (supplied by your audiologist). In addition, the implant is best cleaned with a baby wipe or alcohol wipe each day. The hearing aid must be removed for showering and swimming. A small cover is available for the abutment, if desired, when the hearing aid is not being worn.
Are there Complications of a Bone Anchored Hearing Aid?
In adults, the implants seem to last well indefinately, but there is a small risk of the implant not healing well or later becoming loose. Particularly in children, the implant site may become infected periodically. This is usually treatable with antibiotic creams and occasionally oral antibiotics. 20% of children in my clinic will eventually lose their original implant through infection or trauma (such as being hit by balls)