26 September 2017
For most children that are supported by the Cora Barclay Centre their hearing loss is sensorineural; meaning their loss is due to problems with the inner ear or auditory nerve. However, for some children the inner ear and auditory nerve are completely fine and the problem comes from an inability for sound to reach the inner ear or auditory nerve. This type of loss is known as a conductive loss.
Of the 275 children currently enrolled with the Cora Barclay Centre we have 38 children with a conductive loss. By far the most common conditions that creates a conductive hearing loss amongst our students are microtia and atresia, and we currently have 15 students with these conditions.
What is microtia?
The literal translation of the Latin word microtia is little ear. Microtia occurs during the first trimester of pregnancy when the outer ear doesn’t develop properly. There is no definite type of development of a microtia ear. Some ears may be completely absent, others are peanut shaped, and some may look like a fully developed ear, just smaller. Microtia is very often accompanies by atresia.
What is atresia?
People with atresia have a closed, or completely missing external auditory ear canal. It can also create a malformation of the middle ear bones.
How do people with microtia / atresia hear?
Obviously if the outer ear and ear canal are missing or blocked there is no way for sound to enter the ear canal and reach the inner ear. This is the reason that people with microtia and atresia are unable to hear. For many the inner ear remains in perfect working order, the sound just can’t get to it!
This means that regular hearing aids and cochlear implants do not work or would not be appropriate. A regular hearing aid amplifies sound, but the sound is delivered through the ear to the inner ear, and a cochlear implant is designed to replace the damaged hair cells in the cochlea, something which works fine for those with microtia and atresia. Luckily there is another option, and that’s bone conduction.
What is bone conduction?
Every one of us, whether we have hearing loss or not, use a combination of bone conduction and air conduction to hear.
If you have full hearing you will mainly rely on air conduction to hear; sound passes into the ear canal to the ear drum, which then converts the sound waves to vibrations and sends them to the cochlea then up to the auditory nerve and into the brain.
With bone conduction the sound by passes the ear drum. The vibrations go straight to the cochlea and are then passed to the brain. This is actually how you hear your own voice, even with full hearing.
What technology can help those with microtia / atresia?
A different type of hearing device known as a bone anchored hearing aid (BAHA) utilises bone conduction to allow people with microtia / atresia to hear.
A bone anchored hearing aid sits on the outside of the head, near the ear. The microphone takes in the sounds and converts them to vibrations, which are then felt through the skull by the cochlea. This is a great video by
Cochlear which shows how a BAHA works (there are many other brands of BAHA available).
This video shows the BAHA anchored to the skull, however, this surgery is not available until at least the age of 5. Until that point children wear their processor on a soft head band and the vibrations pass through the skin.
What does a BAHA sound like?
As you can imagine the sound heard through a BAHA isn’t akin to that of normal full hearing. It can sound a little tinny, or like an AM radio station. However, the technology has advanced considerably over the last few years and learning to listen and speak using a BAHA is completely possible.
Can microtia or atresia be fixed?
The very short answer is yes, but the reality is much more complicated. Families can consider several options.
No surgical intervention
Obviously, the first option is leave the ears as they are. With the addition of a BAHA children can learn to listen and speak and can achieve their goals, just as well as any other child.
There are two ways that an ear can be reconstructed surgically; the first option is using the child’s own rib cartilage and body tissue and the second is using the child’s own skin around a man-made framework.
The final option is to have a prosthetic ear created and attached. Prostheses technology continues to advance, with Queensland University of Technology even developing a 3D printed ear.
Obviously, every family needs to consider which options are right for them, but the great part is that there are options.
Where can I get more information?
We have tried to give a brief overview of microtia and atresia here to help increase awareness and understanding, but if you have a child, or family member with either condition and would like more information you can use the links below:
Also, our sister centre, Hear and Say, run the Australian Microtia and Atresia Conference each year which provides up to date information on current treatments and management options.
If your child has microtia or atresia and you would like more information on their options for hearing, please get in touch.