Friday, July 02, 2004

The Truth About Cochlear Implants, or What I Learned on my Summer UnVacation

I admitted in a post a while back that I had always found cochlear implants (CIs) 'creepy', although I've never had much of a 'thing' with any other physical oddity. (A result no doubt of my many months in hospital, as well as a general occupational and personal attitude of appreciation of diversity.) Well, the good people at my office have given me this week off to try to sort out as much of my personal mess as possible, and part of that has involved taking the time to research the CI in a lot of detail.

Boy, was I stupid.

Most of my inability to accept CIs, I realize, come from the fact that I had the boneheaded (pardon the pun) impression that the external unit sort of 'plugged in' to some kind of socket in the scalp. In fact, the internal unit which is implanted during the surgery is entirely under the skin; the external unit attaches to it with - a magnet!

Well, duh.

In terms of keeping the area clean, safe and healthy, this changed my view of the CI enormously, to say the least.

The device is hugely ingenious and the process, from sound to hearing, works like this:

* a sound is picked up by a microphone that is worn behind the ear (think of an external hearing aid);

* the microphone shoots it via a wire to a little computer which is worn on your belt;

* the computer turns the sound into something your implant can tell your brain to understand, let's now call it an 'impulse';

* the impulse is now shot back up the wire to a transmitter which is attached to your head - and attached, on the other side of your skin, to the implant - with a magnet;

* the transmitter beams the impulse across the skin to the internal implant, which feeds the impulse along a wire curled through the cochlea.

That impulse causes the stimulation of the correct combination of electrodes spaced along the wire - 22 or 24 now, as opposed to one or two in early models - to send your brain the illusion of a reproduction of the sound.

Brilliant, no?

There are lots and lots of good diagrams and descriptions on the web; here are some of the best I've found:

Frontal cross-sectional diagram of an implant

A photo of what the device looks like when being worn

There are also, for the not-faint-of-heart, photos of the actual surgery online. This set is of the surgery being performed on an infant and was pretty alarming when I first saw it. However, I then thought about the relative size of an infant and adult head (interestingly, the cochlea itself doesn't grow much; but obviously the skull and ears do, significantly) and figure that adult surgery wouldn't be, relatively speaking, nearly as invasive.

So, like most prejudices, mine against CIs turns out to be based on misinformation and ignorance. And smartening up about it has opened me to a possibility.

Man, if I learn any more life lessons out of this, I'll be too smart to live with.



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