The Basics
So, how does it work?
Concerns for children with hydrocephalus and cochlear implants
Will a cochlear implant restore my child's hearing?
What is the process for getting a cochlear implant?
While this website might be dedicated to congenital hydrocephalus, I feel that it is appropriate to add a page for cochlear implants. The cochlea and other structures in the middle and inner ear are very delicate and do not always do well under the pressure that is placed on the head and skull before a child can be shunted. As a result many children with hydrocephalus are born deaf or with significant hearing problems. Therefore many parents of children with congenital hydrocephalus will have to face the decision of whether or not to pursue a cochlear implant for their child.
The Basics
As always, it's best to start with a picture and to begin with the basics. First, you need to understand how the ear works.

In a normal ear, sound is collected by the pinna (the outer part that you see and stick earings in) and is directed down the ear canal. The sound hits the ear drum causing it to vibrate, which in turn causes the small bones of the middle ear - the hammer, anvil and stirrup - to vibrate. The middle and inner ear are filled with fluid which allows the vibrations from the small bones to travel down into the snail shaped cochlea. The walls of the cochlea are covered with small hair cells that translate the vibrations into electrical signals which are picked up by the auditory nerve and then interpreted by the brain.

Next we move onto what happens when things are not normal. One of the most common forms of hearing loss is called sensorineural hearing loss and it is generally caused by a failure of the hair cells in the cochlea to transmit their electrical signals to the auditory nerve. This is the type of hearing loss that a cochlear implant can help with.
So, how does it work?
A cochlear implant works by bypassing the outer and middle ear altogether and sends signals directly to the auditory nerve. The diagram below is from the National Institutes of Health. In this diagram you can see that the cochlear implant has electrodes which are coiled up down in the snail shaped cochlea.

A cochlear implant has two parts - an external part with a speech processor and battery pack that is responsible for receiving sound and an internal part which is responsible for transmitting those sounds to the auditory nerve. The two parts communicate with each other through magnets which pass the messages through the skin via magnetic induction. There is no physical connection between the internal and external pieces, the skin is completely sealed.

Below is a picture of the external hardware. The piece sticking to the side of the person's head is called the coil. It is being held in place by a magnet which sticks to a magnet in the internal piece which is just below it under the skin. In younger children whose ears are too small to support the fully "behind the ear" speech processor, a "Babyworn" configuration is used where there is a small piece over the ear to place a microphone in the correct position for natural hearing, but the speech processor and battery are in another piece which can be clipped to their clothing. Below is little Mariah (thanks to her Mom for letting us use these pictures, you can read Mariah's story here) with the Babyworn setup. Mariah has bilateral implants, meaning that she has implants in both ears, so you can see two processors clipped to her shirt. From the front it is much harder to see the whole rig. Mariah is wearing the Nucleus Freedom cochlear implant system from Cochlear Corporation.


The internal piece is surgically implanted behind the ear. If you are not squeemish you can actually see a video here of the surgery done by Dr. Buchman at UNC-Chapel Hill, who did our son's surgery. Below are the internal pieces of the cochlear implants by the three major manufacturers:

Cochlear Corporation
Nucleus Freedom
  Advanced Bionics

The internal pieces are very similar between the manufacturers. There is a metal portion at the top which contains the magnet and the electronics that translate the signals from the external piece into electrical signals that travel down into the long probe that comes out from the bottom. The probe is inserted down into the cochlea and it has electrodes on it that send electrical signals to the auditory nerve. Each manufacturer has a different number of electrodes and different shape for the probe, with each one claiming that their setup is better than the others. In reality they all seem to work well, and often the choice of which manufacturer to use depends on the anatomy of the child and the shape of the manufacturer's probes to match that anatomy.
Concerns for children with hydrocephalus and cochlear implants
Before a child is implanted they go through a fairly long process to determine if they are a good candidate. One problem that may be encountered is a misshapen cochlea or a damaged or missing auditory nerve. If your child's hydrocephalus is one of the types that forms very early in the pregnancy, then it may be that the cochlea and nerve will have to form under pressure. In order for a cochlear implant to work you need to have an intact auditory nerve and a cochlea that is at least intact enough to lay the electrodes in. In our son's case he has no auditory nerve and the cochlea barely got started forming on his left side. As such he cannot have an implant on that side. On the other side the cochlea did not fully form, but there was enough to get 20 out of the 22 electrodes of a Cochlear Nucleus Freedom in and his auditory nerve was fine. An MRI taken at the beginning of the process will show if the cochlea and auditory nerve are intact. !!!Remember, if your child has a programmable shunt, it will need to be reprogrammed immediately after the MRI!!!

Another possible complication for kids with hydrocephalus is if they have a programmable shunt. Both the internal and external components of a cochlear implant use magnets to stick the coil to the head and to communicate. Programmable shunts are reprogrammed using magnets. If the cochlear implant and the programmable shunt are on oppoite sides of the head, then the internal pieces will not interfere with each other. The external pieces have to be thought about in greater detail as they can be moved around and the child could accidentally put it right over the shunt even if the cochlear implant isn't on the same side. MED-EL makes a magnet for the external piece that is strong enough to reprogram a programmable shunt and that magnet should not be used - but all of the models come with choices in strength for the magnet so it should be possible to avoid the strongest one. The weaker ones do not seem to be able to reprogram the shunt, or if they do it can only make small changes. Also, the design of the Codman Hakim programmable shunt makes it considerably more difficult to reprogram than the Medtronics programmable shunt. If you have a Medtronics programmable shunt it may not be possible to use it with a cochlear implant, but I don't have definitive data on this. A study on programmable shunts and cochlear implants was recently done at UNC-Chapel Hill. If you need information on this please contact Dr. Craig Buchman's team in the ENT Department at (919) 966-6484.

Will a cochlear implant restore my child's hearing?
Well, yes and no. Firstly, there is no guarantee that the electrodes will be able to deliver a good enough signal to the auditory nerve, especially when you are dealing with a damaged or misshapen cochlea. There is no way to know for sure until you turn it on, although the surgeon can generally tell you if there is at least a decent enough chance to warrant the attempt from the MRI.

So lets say you turn it on and walla, the child reacts to the sound. The next thing to remember is that the normal cochlea has about 16,000 hair cells in that send signals to the auditory nerve. The implant with the largest number of electrodes is the Nucleus Freedom by Cochlear and it has 22. That's less than one percent of the number that a natural cochlea has, so it is not the same quality of hearing. However new software has done some amazing things with those 22 (or even the 12 from MED-EL) electrodes and many people are able to understand speech and even enjoy music. I think of it as watching a streaming video on UTube. It's not nearly the same quality as on my HD television set, but I can usually figure out what's going on and get the point that the video is trying to get across.

So after you turn it on it is going to take some fairly intensive speech therapy to actually achieve the ability to speak and understand what is being said by others. The most common method of speech therapy for people with cochlear implants is called AVT, or audio verbal therapy. It emphasizes learning individual sounds first and then teaches them how to pick out those sounds from words and then how to pick those words out of sentences. The term "learning to listen" is used quite often in AVT and it sums up the methodology quite nicely. Whereas hearing people learn to listen naturally, a cochlear implant recipient has to work much harder at it, mostly because of the limitations of the implant and also due to the fact that the child is already delayed when they start because they may not have been hearing properly since birth.

The other thing to keep in mind is that hydrocephalus often brings other learning delays with it in addition to the ones already caused in the speech area by deafness. This can have a greater impact on the final ability to acquire speech than the hardware of the implant itself. In our case we decided that even if our son is not able to speak in the end, it is still worth it to have him be able to hear us and know that we are there even when he can't see us. When he is sitting by himself and we are not in the room we cannot even call out to him and reassure him without actually going out and standing next to him. During the long car rides to doctor's appointments in North Carolina (we live in Virginia) he is by himself in the back seat in a rear facing car seat and he can't see me except a bit in the mirror. I would like for him to be able to hear me singing to him and talking to him, even if he can't talk back.
What is the process for getting a cochlear implant?
The process starts at birth with the newborn hearing screening. This was not done for our son because of all of the other issues we had with prematurity and hydrocephalus. Please make sure that they take the few minutes and do it before your child leaves the hospital. It is required by law in most states and the sooner you know, the sooner you can get treatment. Even if they pass the newborn hearing screening you should probably get a screening done again at six months and one year just to be sure that there is not a partial hearing loss. Those first months and up to the age of 3 (some say 5) are really critical to language acquisition and there is such an increased risk of hearing loss with hydrocephalus that it is something you should pay extra attention to.

If your child fails the newborn screening or a later screening, the next test that will be done is an otoacoustic emissions test or OAE. An OAE is done while the child is awake but calm. Ear plugs that are connected to cables are placed in the child's ears. A computer or small hand held device plays a tone into the ears and "listens" for an echo that most normal ears produce. This test is very quick and painless and you should get the result immediately.

If the child fails to produce a response on an OAE then they will be asked to do an Auditory Brainstem Response or ABR test. It is possible to fail an OAE and still have hearing, though it is extremely rare. The ABR test is usually done in a hospital setting because the child must be sedated. Electrodes are placed on the child's head while sounds are played. If the auditory nerve is receiving sounds it will produce an electrical impulse which is read by the electrodes. Tones are played at different volumes and frequencies to test if there is a full or partial hearing loss. An ABR result is usually considered definitive. It is possible for the re-routing that occurs in the hydrocephalic brain to produce an unusual response, but most technicians know that and will try more than one site for the electrodes, though it is something you might want to mention at the time of the test. Even so, an ABR is generally considered definitive. If they are hearing anything, it should produce some kind of response, even if it is an unclean signal because of re-routing.

It is important to note that there are two different ABR tests, a "click" ABR and a full tonal ABR. The click ABR just plays single clicks to test for responses and therefore tests a very small frequency range. The full tonal ABR tests a much wider range of sounds and will be much more useful. In fact if they fail the click ABR most cochlear implant centers will require that they go through a full tonal ABR first thing. As such, I would recommend that you make certain that the first test is a full tonal one so that you don't have to go through it all over again later.

One other type of testing that might be done for older child is behavioral testing. In this type of test the child is put in a sound booth and they are watched for responses while sounds are played. If they are old enough or capable, they will be trained to turn their head toward a video screen or a toy that lights up every time they hear a sound. The training is done with a vibration that comes with each sound at first, and then when they reliably turn their head the vibration is removed.

You can read more about the testing that is done here. The tests that are done will produce something called an "audiogram". This is a graph that shows any response at any frequency or decibal (volume) level. If the child does show some response to sound but not normal hearing, then the audiogram will be used to set up their hearing aids. If there are no responses the then audiogram will just be a flat line. Below is a picture of an audiogram:

Even if the child produces no responses on any of the above tests, it is likely that they will be given a set of hearing aids anyway to use for a trial period during which they will be tested several times while wearing them. This may seem frivolous, but it isn't. The placement of a cochlear implant generally destroys any natural hearing that a person might have. They have to be absolutely certain that there is not enough residual hearing to be useful. It is also important to note that even if a child does produce a response on these tests, they may still be a candidate for a cochlear implant. It is possible to have some hearing, but have it not be enough to be able to acquire speech. Think of how you hear sounds while swimming underwater. Your friend can be shouting at the top of their lungs on the pool deck, but all that you can hear is that they are shouting. You can't make out the words that they are saying. Or think of hearing someone that is speaking quietly at the other end of the room. You know that they are saying something, but again you can't understand the words. For children whose hearing exists but is not enough for them to understand speech, it may be beneficial for them to receive a cochlear implant.

At some point in this process if it seems likely that a cochlear implant will be needed then an MRI will be done. The MRI shows the cochlea and the auditory nerve and will be looked at by a surgeon that can use it to determine if they are in good enough shape to receive a cochlear implant. REMEMBER! If you have a programmable shunt it will need to be reprogrammed immediately after the MRI! A CT scan is not detailed enough to show the tiny little cochlea and auditory nerve, so it has to be an MRI.

Once they have gone through all of the testing and it has been determined that they are a good candidate, then the surgery will be scheduled. As I mentioned above, if you aren't squeemish you can view a video of the surgery here: here. The surgery takes 90 minutes to 4 hours, depending on the anatomy that has to be worked around. After the surgery huge bandages will be placed on the child's head. Below is another picture of little Mariah with her bandages. She had both ears done at the same time, so she has bandages on both ears.

I would have used a picture of my own son, but he managed to get the whole rig off before I could even get a picture. We had to resort to Mommy running to JoAnn's fabric and getting some sundress material to stretch over the bandage. And sundress material doesn't come in boy colors so yes, it's a pink hat that you can just see the white bandage sticking out from on his right side.

The bandage stays on for 5 to 7 days, or at least you try to keep it on that long. The hardest part of the whole process starts now, they can't just turn on the device. Typically you have to wait 4 weeks before turning it on, which is called "hook up". After the surgery everything needs to heal completely before they start putting an electrical current through the tissues. Some centers do three weeks and some go as far as two months, but four weeks seems to be the average. It's very hard to have the device in, with all the hopes that it brings, and not be able to even test it out to see if it's going to work.

As of this writing, this is as far as we have gotten in the process. The implant was put in 4 days ago, but we have not made it to hook up yet. But we have a fairly good sense of what the process will be from here on out. We have been warned that the hook up which we are so excited about may not be what we expect. Some children turn their head when they hear the sound, some cry, some just stop what they are doing and stare and some may not react at all. They do not start out with the implant at full volume, they start out with a conservative setting and it is possible that they might not hear anything at all on the first mapping. It is also possible that it won't work and that his anatomy won't allow it to produce sound for him.

At fairly frequent intervals for the first few months you will return for new mappings. Mappings are programs that are loaded into the speech processor to optimize the output for your specific child. If the child is old enough or capable the first mapping will be created with their help as they tell you what they can hear. If they are too young or not capable of communicating what they are experiencing most of the implants have the ability for a computer to measure the response without the child's input and that will be used to determine that first mapping. It may take several mappings to get the settings right for the child to be able to show reliable responses to sound. The audiograms that were mentioned above will become very important in determining the changes needed in the mappings.

The final step is lots and lots of speech therapy and lots and lots of work at home. The speech therapist can teach a parent how to help the child at home. Speech must be emphasized all day every day in every possible way to maximize the child's exposure and to help them progress. AVT therapy includes many songs and toys and actions that are used to teach sounds and the parents can use these at home as well. A great deal of the outcome is based not so much on the implant itself, but on how much work is done after the implant is working.

There is a tremendous amount of information out there about cochlear implants and there are no shortage of web pages covering this subject so I won't bother to put a list of links here. However I can recommend a video that we bought that was particularly useful. It's only available on VHS, but it's worth it to dust off the VCR. It follows two sets of twins, with one born hearing and one born deaf in each pair, one set are both girls and in the other set both are boys. In each set, the deaf child is implanted at one year old and they follow their progress until they are four years old. It is great to see their progress, and it gives you a true idea of what is involved in acquiring speech with a cochlear implant. The movie is called Twins and you can purchase it here.

Legal Disclaimer: While every effort has been made to make certain that the information contained in this website is accurate, it must be remembered that the content is managed by a parent, not by a doctor. Information contained here is for general support purposes only and is no substitute for the care of a physician.