Cochlear Implants

So what exactly is a cochlear implant?

In short (or as we described it to Alice’s big brother Joseph) it’s a machine that is in your head that will make you hear.  Does that really explain it? – no.  To understand what a CI is requires a bit of understanding about how the ear works.  So (and please note, as the non-scientist in the household, I am writing this bit) here goes.

Normal Hearing

Your ear is divided into three parts:

Outer Ear –  the outside bits up to your ear drum. Its role is essentially capturing sound and making the ear drum vibrate (1)

Middle Ear – ear drum to inner ear. This is the bit that contains the three tiny bones that continue to transmit the sound into your head.  It is the motion of these bones that causes the fluid in the inner ear to move (2)

Inner Ear– this contains the snail shaped cochlea (3) containing the organ of Corti (this contains the all important hair cells) (4).  The fluid in the inner ear causes the hair cells to start waving (in synchrony hence dys-synchrony in Alice’s case) and these waves convert into electrical pulses.

These electrical pulses are then sent up the auditory nerve (5) to the brain for translation into sound

Are you all with me ?

Ok – a picture to help.

howearnormworks

This is all great, but when you are hearing impaired you essentially have a problem somewhere along this path.  Depending on where the problem is and the underlying cause (and extent) will all ultimately drive the appropriate choice of treatment.

So back to the original point.  What is a Cochlear Implant.  We often used the term bionic ear, not only does it sound more exciting, but for most people how haven’t sat through endless lessons in ear biology, its easier to comprehend.

Cochlear Implant

So the bionic ear – Hearing is the only sense that can currently be replaced (to an extent) with technology and we take comfort that there is something we can do.

The CI essentially replaces 1,2,3 and 4 and stimulates the nerve directly.  Probably easier to see this with another picture….

ear_coch

So the wonky bits in Alice are by-passed.

The CI comprises 5 bits; an internal electrode and receiver and then externally a transmitter, a microphone and a speech processor.

Internally –  the electrode sits within the cochlea is actually 22 electrodes (recent articles suggest that this could increase to 50 in the next 5- 10 years).   This is pushed (carefully) into the cochlea during surgery.  This is attached to the receiver which is implanted just below the skin above the ear.

electrode

This is the array itself

Externally – a microphone (obviously to pick up sound) and the speech processor to convert that sound into digital form.   The two parts are essentially joined by a magnet in the receiver and transmitter across the skin.  Easy?

ci

CI devices are currently made by 4 companies: Med-el (Austrian), Cochlear (Australian), Advanced Bionics (American) and Neurelec (French).  The first 3 are approved in the UK, but St. George’s only really work with Cochlear, so no real choice there.  As Alice is small, we’ll start with the processor not behind her ear but “baby worn” so either under her clothes or pinned to a t-shirt.  You can spot a CI wearer though by the Star Trek style wire and circle on their head.

That’s the basics of what it is – but we think it is also important to understand what it means for Alice and us. We’ve not really taken our first steps (having only recently touched a CI for the first time recently) so then next bit will be updated as we get there.

UK Assessment Process

Alice’s condition has meant that some of the assessment has not necessarily happened in the right order.  But essentially assessment covers 3 main areas.  What is Alice’s physical situation, what is the hearing loss and what is her current development.  Or in other words:

  • General health check– covering deaf complications – deafness can coincide with other complications, so is there anything else that the surgeons need to be aware of (eye-sight check, kidney ultrasound, heart ECG).  She has also had MR and CT scans of her ears.  These look at the soft tissue and the cochlear and ear bones in some detail, largely to see if there is anything unusual (for example a true neuropathy) and also from a surgical perspective if there are any restrictions (such as a malformed cochlea).
  • Hearing assessment– how bad is her loss and is one ear better than the other (achieved by a whole load of extra audiology).  This becomes particularly relevant if unilateral or sequential implants are being considered.
  • Development – predominately provided by assessments by the CI Teacher of  the Deaf and the CI Speech and Language Therapist.  These are focused on measurable developmental milestones, partly to draw a line in the sand as to where we are currently, but also to have measures of improvement post implant.  Our frustrations often came out in these sessions as yet another hour was spent watching Alice bath the doll, or feed it imaginary food.  The reality is that these measure her internal language, her grasp of concepts and other deaf child monitoring protocols …

Implantation

What we are really talking about here is surgery.  Alice will have her ears done separately (our choice and a very hard one).  In the UK, NICE  has decreed that all severely and profoundly deaf children should be offered bilateral simultaneous implants, which is fantastic news.  Currently there are very few centres in the UK that offer CI and St Georges is a relatively new programme.

Choosing a centre is ultimately down to individual choice, but we decided based on a couple of things.

1. Staff – we liked the team at St Georges, David in particular.  They are open, friendly and generally willing to listen to our probably mis-guided thoughts and gently point us in the right direction.  ANSD does not complicate the surgery, but it does have its own “academic considerations”, the team were willing and available to debate these.

2. Quality of “aftercare” what we really mean here is the therapy.  Successful implantation does involve good therapy.  Alice needs to be taught how to use her CI and she needs plenty of support getting the best out of it.  We are new to this, the team isn’t.  St Georges has a small team and prides itself on best in class processes.  They proudly state they know all the children on the programme, one can’t help but wonder if this would be the case on larger programmes.

3. Ease of access, not to be underestimated.  We have been to St Georges, probably 30 times already.  By the time Alice is 3, we will have been another 30.  Of course we would go to the ends of the Earth to give her the best possible care, but it helps that we don’t have to.

So there we are, I’ve avoided it for long enough, but sooner or later, the fact that a nice man has to drill into Alice’s skull can not be avoided for ever.

Surgery

First a small incision is made behind the ear.  Alice’s incision is tiny, less than 3 inches long as is tucked in the crease behind her ear.  Different surgeons will do this more or less invasive.  The surgeon then drills into the mastoid bone and into the inner ear.  This enables the electrode to be feed through into the cochlea itself.  Cochlear claim that their latest device doesn’t damage the hair cells during insertion, protecting the natural hearing (we remain sceptical).  full insertion is achieved where all 22 electrodes are placed within the cochlear.  The receiver is then pushed under the skin into a slight well made in the skull.  Finally post surgery the device is tested whilst the patient is still under anaesthetic.  The area is then bandaged to reduce swelling.  Anti nausea drugs and antibiotics are usually given post surgery to reduce the risks of complications.  Patients can feel dizzy for a while after surgery, Alice was certainly a bit wobbly.

Interesting points to note include the position of the implant.  Poor Mr Selvadurai, he has promised to get his protractor out for number 2, to make sure they line up on her head….

Mapping

A week or so before you first get mapped, the equipment comes home for trial and we get to play with the most amazing piece of medical equipment I have ever seen.

What is mapping ?

Mapping is essentially the programming of the device for an individual.  Essentially the purpose of this is to increase the intensity of stimulation that the patient can bear.

Therapy

Now I need to apologise for ripping this from someone else and I’ve seen the analogy elsewhere talking in terms of pixelation on cameras but it all boils down to the same thing, CI’s are not normal hearing.  They are good / amazing but not the same as hearing as we do… so

” I’ll try to make a visual picture that relates to the way sound is heard by a child with a cochlear implant. Suppose that you have to identify a four-legged animal, and you’ve not seen that animal before but you have to figure out what it is. Maybe you have to draw it. Maybe you have to learn the name for it.

Now that animal is standing in back of a bunch of trees. To see that animal, you have to look through tree trunks that are hiding big parts of that animal. Now, if you were looking through those trees with the equivalent of a hearing aid, you could probably only see the tail end of that animal because you could only hear the low frequencies with that
hearing aid. With a cochlear implant, though, you can see pieces of that animal’s head, pieces of its neck, its legs, its body, pieces of its tail end, but you still are missing pieces in between each of those that you see.
The reason I’m bringing this up for you to think about is because it’s important for us to realize that children who are using cochlear implants still don’t see the whole animal. They see more of a range of that animal but they have to use their brains. They have to use what they already know about the world. They have to use their cognitive abilities to fill in those gaps to be able to put together a picture of that whole animal. That’s the kind of task that a child is facing using a cochlear implant. ”  Dr. Patricia Spencer, Professor, Department of Social Work, Gallaudet University

This explains rather well where the technology has to get to, like improving the camera on your phone, it’s possible it’s just the next round of upgrades.  We often hear of children enjoying music but struggling with complex sounds and harmonies.  Or as someone once said, telling the difference between good and bad on x-factor (if that’s possible for me with relatively good hearing).

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