How a Cochlear Implant Works
I’ve had several people ask me in the past few weeks if my hearing has improved. I felt it best to write a post describing how hearing aids and cochlear implants work.
There are many different types of hearing loss. Probably one of the more common kinds is the type I have: sensorineural. Basically, this means I have a bone conduction AND a auditory nerve hearing loss. You can have just a conductive loss or a mixed hearing loss, but for the sake of how it all relates to me, I’m just going to stick with sensorineural hearing losses. To get to the root of the issue with sensorineural losses, the cochlea does not work as it should
The cochlea is the seashell/spiral shaped part of the ear to the far right in this picture. It is where the organ of hearing lies. In a nutshell, the interior of the cochlea is lined with hair cells and it is filled with fluid. When sound vibrations enter the ear, the ear drum moves and causes the tiny bones attached to it to move. When these bones move, they cause the fluid in the cochlea to move. The movement of the fluid in the cochlea then causes the hair cells to move. When the hair cells move, they send a signal to the auditory nerve, which in turn sends signals to the brain and the brain interprets what these signals mean to it. As you can see, there are many steps in which the sound can be disrupted and not reach the auditory nerve. I’m not going to get into all of that, just remember that this is a very simplified explanation of how a working ear functions! 🙂 For me, it is most likely that many of my hair cells in the cochlea are damaged. When the hair cells are damaged, there is no sound signal sent to the brain.
Hearing aids are completely external and ultimately are one piece. They amplify everything. Loud sounds can become too loud VERY quickly. Digital hearing aids can do amazing things that the old analog aids could not, but they still amplify. If you wear hearing aids and are in a room where there is a person talking to you and background noise, an air conditioner, for example, it can be quite difficult for you to understand or even hear the person talking over the air conditioner. This is because, much as the audiologist may try to adjust the programming on the digital hearing aids, the air conditioner is still going to be amplified. There gets to be a point where hearing aids just can’t help any more. They are only so strong and can only do so much.
A cochlear implant is two parts, in internal device, the actual implant, and the external device, the processor. They do not just make every sound louder. Instead, the long, thin electrode of the implant (as shown in the picture above) is surgically implanted and inserted into the cochlea. The larger, rectangular part is place on the head, usually above the ear or just behind it and has a small magnet in it. This internal device in the picture above is all one piece and is all surgically implanted at the same time. After the recovery period, the implant is turned on and the external device is received.
I’ll post a better picture when I get my processor tomorrow, but for now, this will have to do. 🙂 The external processor has a piece that goes over the ear, much like a hearing aid, and has a “wire” that has a round magnetic piece at the end. When this external part is place over the area where the internal device, also containing a magnet, the device is then fully connected and begins to send sound signals. You MUST have this external processor to be able to hear. Without it, there is no hearing. There is no way to send a signal to the brain that there is sound. When the magnets are, in a sense, connected, then a signal is sent through the 2 devices. This signal is an electrical signal that bypasses the hair cells and is sent directly to the auditory nerve and then to the brain to be interpreted
I’m going to stop here and leave it at that. Feel free to ask questions! I will post much more later as I learn more and experience what the beginning sounds are like with my implant. They are not likely to be the same as with my hearing aid in the beginning and I will have to learn how to interpret them and give my brain time to adjust and learn. There are still many misconceptions about cochlear implants that I (hopefully) will dispel as time goes on. I’m sure this all seems so cut and dry, but it’s really the basics to hearing and hearing aids and implants and needs to be known before you can really start to understand the rest!