Hey presto! The Deaf can hear...

Having a deaf child, we have had to learn a lot, and fast! With an appointment at the Cochlear Implant Clinic coming up next week I felt it timely to share what we have learnt about the Cochlear Implant and why we are choosing to have Jaime implanted (if she is eligible).

Firstly I will explain a little about Jaime's deafness:

Jaime suffers sensorineural hearing loss, this can also be referred to as nerve deafness.
Although the problem stems from the inner ear (cochlea) rather than the nerve itself, without use the nerve can deteriorate (use it or lose it) hence the sooner deafness is treated the better the outcome (not to mention the learning capacity of young children and babies).
In most cases of sensorineural hearing loss the small hair cells within the cochlea are malformed/absent (in the case of congenital hearing loss) or damaged (in the case of acquired hearing loss). In other rare cases the cochlea or hearing nerve itself may be absent or malformed hence Jaime will require both an MRI and CT scan to ensure the inner structures of her ear are able to accept an implant, and to also ensure her hearing nerve is intact.

Jaime's hearing loss is congenital, meaning that it was either caused by abnormal development (a glitch in the making of her inner ear) or inherited.
We still don't know the exact cause of Jaime's hearing loss and are awaiting genetic testing to determine if she inherited her deafness (despite my husband and I having normal hearing).

*Before the development of a vaccine, maternal rubella or German Measles was also a common cause of congenital hearing loss.


The treatments for sensorineural deafness vary depending on the level of hearing loss and whether the loss is in one ear or both ears.
Jaime suffers a loss in both ears but to a differing degree- her left is a profound loss (>90db) and her right is a moderate-to-severe loss (>70-80bd)
When hearing loss is mild to moderate hearing aids can often help by amplifying sound. For more severe levels of loss, sometimes hearing aids are just not enough. This is because although amplifying sounds makes them louder, it does not necessarily make them clearer. If sounds are becoming distorted by the inner ear, even the best quality hearing aids may not be enough to establish "normal" hearing.

This is where the cochlear implant steps in...

The Cochlear Implant or 'bionic ear' is a marvel of medical science... hey presto... the deaf can hear!

But how?

Within the inner ear is the Cochlea, a small shell shaped canal, within this canal sit thousands of tiny hair cells. When sound waves enter the ear they stimulate the hairs which convert these physical movements and vibrations into nervous impulses that are sent to the brain and interpreted as sound.

A cochlear implant is an electronic device that is surgically implanted - so it bypasses the damaged inner part of the ear. Unlike hearing aids which simply amplify sound at the outer ear, a cochlear implant converts sound waves to electrical impulses that directly stimulate the cells within the cochlea in a way that mimics your natural hearing.


Below is a diagram of a cochlear implant and its components

How it delivers sound...

The speech processor worn behind the ear (BTE) captures sound waves and converts them into digital code.
The digitally coded sound is transferred from the speech processor to the implant by the coil which sits over the implant (held in place by a magnet within the implant).
The implant converts the digitally coded sound to electrical signals and sends them along the electrode array, positioned in the cochlea (inner ear).
The implant's electrodes stimulate the cochlea’s natural hearing nerve fibres, which sends signals to the brain that are interpreted as sound.

...hey presto! The deaf can hear!


Jaime is currently a likely candidate for one cochlear implant to replace her hearing on her profoundly deaf side, we are awaiting further testing to determine if she will require two implants to get the most out of her hearing.


(I will speak further about the selection process for cochlear implant recipients and the advantages of bilateral hearing later)


Information regarding sensorineural hearing loss and Cochlear implants curtesy of
http://www.cochlear.com/au