A BAHA (Bone Anchored Hearing Aid) is an auditory implant and sound processor for people with hearing loss who don't benefit from normal (air conduction) hearing aids. The commonest reasons for considering BAHA are
chronic ear infection - when wearing normal hearing aids makes the infection worse
single sided deafness due to tumours, surgery or trauma
children born with abnormal ears
A small titanium screw is implanted behind the ear. Sounds are conducted directly through bone to the cochlea, bypassing any problem in the outer or middle ear. You need at least one working cochlea for a BAHA to help you hear. The sound processor is normally hidden in the hair.
Bone Anchored Hearing Aid components diagram courtesy of Cochlear / Entific
BAHA direct bone conduction of sound to cochlea
The BAHA system consists of 3 parts:
The sound processor a detachable electronic hearing aid with a snap-fit coupling to the abutment. The user takes the sound processor on and off as required, for example for hair washing or swimming.
The abutment a socket attached by an internal screw to the fixture. The abutment penetrates the surface of the scalp and is shaped to hold the snap-fit coupling of the sound processor. The abutment can be unscrewed from the fixture for maintenance or replacement by the specialist audiologist.
The fixture (or implant) a small titanium screw, four millimetres long, implanted into the bone behind the ear. The fixture is permanent, it is not adjusted or removed. The metal becomes firmly anchored to living bone by the process of osseo-integration.
The audiologist will do two main hearing tests to help decide if the BAHA will help you.
Pure Tone Audiometry (air conduction and bone conduction) The BAHA works by conducting sound directly to the cochlea by bone conduction. It doesn't matter how much damage has been done to the outer ear, eardrum or ossicles (small bones of the middle ear). The BAHA will still work even if these structures are missing altogether. But you do need at least one working cochlea (inner ear). The hearing ability of the inner ear is measured by the bone conduction thresholds of the pure tone audiogram. The BAHA will still work with some damage to the inner ear. Depending on the results of the bone conduction audiogram, you may be suitable for a head mounted sound processor, or you might need the more powerful body-worn sound processor. If you are very deaf with poor cochlear function in both ears, a BAHA might not help you. You might need another treatment such as a cochlear implant.
A headband test you will have the opportunity to "try out" a BAHA on a headband. The sound quality you will get from the headband is not nearly as good as the real thing, because the sound is muffled by having to pass through the soft tissues of the scalp. If you can hear reasonably well with the headband BAHA, you will hear better with the implant proper.
Mrs Amanda Banham BSc MSHAA is a qualified independent hearing aid audiologist with 17 years experience. She is trained in assessment and fitting of Baha® Divino and Cordelle sound processors. Contact details: Hearing Aid Consultancy Wellington Cottage Main Road Sellindge Ashford Kent TN25 6EQ tel 01303 813531 mobile 07775 952609
Baha® headband
Surgical assessment
BAHA is commonly used to treat conductive hearing loss due to chronic ear infections. It can also be used to treat single sided sensorineural deafness, where one cochlea (inner ear) is no longer working. Before recommending BAHA as a treatment, you will need a specialist assessment to confirm your diagnosis. Microsuction of the ear may be needed. Even if you are suitable for BAHA, there may be reasons why another treatment is better in your case. It is important to know what you hope for and expect from treatment, we can then tell you whether the BAHA is likely to achieve that. Having any form of implant surgery is an important decision with a lifelong commitment. We do not want hasty decisions, you should not feel under any pressure, we prefer you to have the chance to consider things carefully. We provide you copies of the written report on your assessment as a matter of course, and often advise you to think things over at home. On the other hand, we do not expect you to shoulder the burden of treatment choices alone, we are there to help. If the best choice of treatment is clear, we will tell you so. We will do our best to help you understand the pros and cons of all the treatment options. Top of page
The titanium fixture is implanted into the skull behind the ear under local anaesthetic in the operating theatre. Surgery to implant a BAHA fixture is not an ear operation, your ear itself is not operated on. The procedure is similar to dental treatment, and takes less than an hour. Hair is shaved above and behind the ear. After cleaning with antiseptic solution, you will receive several injections to numb the area. You will then hear the sounds of the dermatome raising a skin flap, and the soft tissues of the scalp being removed. The actual drilling of the bone takes less than a minute and is painless. The titanium fixture and abutment are screwed into place, and the skin flap is stitched down. A dressing is positioned over the abutment. It is held in place by the temporary white plastic healing cap, which snap-fits into the abutment. Top of page
Head bandaged following BAHA surgery under local anaesthetic in operating theatre
Dressings
You will be able to take off your head bandage the day after surgery. You should leave the plastic healing cap alone, we will remove that at your first follow-up visit some two weeks following surgery. Top of page
Temporary healing cap used to hold dressing in place after surgery
We normally see you two weeks after surgery to remove the plastic healing cap and dressings. Your next follow up will be around 2 months. You will see the surgeon and, if the condition of the skin graft, abutment and fixture is satisfactory, will be able to proceed to fitting of the sound processor.
St Saviours Hospital Hythe Kent
Fitting of Sound processor
Mrs Banham will show you how to take your sound processor on and off, and how to adjust it. You will also receive written information from Cochlear / Entific, the manufacturers of the BAHA.
You have a lifelong commitment to cleaning and hygiene around the abutment. The BAHA is based on the same titanium technology used for dental implants. If you don't clean your teeth every day, you will develop gum disease. Infection will set in and loosen the tooth and it will fall out. The same will happen with the BAHA unless you look after it. You may need daily cleaning with a baby toothbrush around the abutment, though some patients do not seem to need to clean so often. Top of page
Daily hygiene with toothbrush around baha abutment
It is OK to have an MRI scan with a BAHA. All patients undergoing magnetic resonance scans are asked whether they have any metallic implants. Strong magnetic fields inside the scanner could cause ferrous metal to move, and this could injure the patient. Patients with stainless steel wires, clips and pacemakers cannot safely have an MRI scan. But the BAHA fixture and abutment are made of titanium. Titanium is non-magnetic. It will not be affected by the magnetic field, and there is no problem with having magnetic resonance imaging with your BAHA implant. There are ferro-magnetic parts in the sound processor. You will need to take off the sound processor to go into the scanner.
A BAHA is not a one-off purchase, it is more like buying a car - you know you will have running costs, petrol, servicing, and will eventually need a replacement. With the BAHA you will need to pay for batteries, maintenance and allow for replacement of the sound processor in future years. It is not possible to know how any individual sound processor will behave, but most of our BAHA patients use their hearing aids all day, every day, with usage around 6,000 hours per year. The sound processor does contain moving parts (particularly the transducer which converts the sound signal into vibrations in the metal) and it will eventually wear out. The manufacturers of the sound processor estimate its working life expectancy to be around three to five years, depending on usage. You have two main options to budget for this
Pay as you go - servicing, repairs and replacement as required
Three year maintenance & replacement plan covers all repairs and servicing, with provision of replacement sound processor at 3 years. If your existing processor is still in working order, you can keep it as a spare. Cost £2,500 spread over 3 years, equates to £16 per week or just over £2 per day.
For full details of the maintenance replacement package, see Cochlear Corporation documentation available from Mrs Banham.
http://www.baha-users-support.com founded to support patients attending Mr Fairley's clinic in Kent 1999, now a UK registered Charity providing advice and support to current and potential BAHA users worldwide
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