On Tuesday morning, baby3 will have an operation: once it’s concluded, if everything goes well (and we’ve no reason to think it won’t) he’ll be able to run at 70mph, and jump 10ft in the air from a standing position.
Well, no he won’t. That’s not the operation at all. But in the same way, the aim is to enhance what he has, to take it beyond what he was born with. The operation is a cochlear implant: a tiny processor is bedded in the skull, and filaments inserted into the cochlea (the inner ear, which connects to the auditory nerve). It’s almost keyhole surgery; the intention is that the scar will only be an inch or two long, behind the ear, almost invisible. And when that’s healed, an external processor – sort of like a hearing aid, except it generates a digital output – will attach magnetically to the processor under the skin, and stimulate his nerve directly.
It’s not been an easy decision. What are the risks? Some think there’s an increased risk of meningitis (but a BMJ paper retrospectively looking at the incidence of meningitis among implantees didn’t find any significant different compared to the population). There is a risk that the surgeon will hit the facial nerve and damage it; that would be bad, possibly the worst “expected” thing that could happen in the operation. Then there are all the imponderables about operations – although he has had general anaesthetic before, to have grommets inserted earlier this year.
How did we get here? First we discovered he’s profoundly deaf. Equally, he’s vivacious, clever, delightful. He’s building up a vocabulary of sign language with increasing speed; soon, I suspect, he’ll start stringing words together. So why subject him to an operation at the tender age of 14 months? There’s nothing medically wrong with him.
A skin incision is made behind the ear. A special instrument is placed on the patients face to monitor the facial nerve.
Incision? Ow, that’s big. Careful with that scalpel, Eugene.
Because he lives in a world where everyone runs at 70mph and jumps 10ft in the air. Plus, our limitations are in effect holding him back: we’re not nearly good enough at sign language (we can probably manage about 50 or 60 words, of which he understands probably 30 or 40), and don’t use it consistently enough, to satisfy his sponge-like desire for more words, more language, more comprehension, more understanding of the world. He picks up words almost as quickly as he sees them now: you sign ‘dolphin’ (curved hand going over waves), and he echoes it straight back. Who knows how quickly he might pick up spoken language if we can only connect him with it?
The mastoid bone (bone behind the ear) is then removed with a high speed surgical drill. An area of bone above the ear is also removed in order to make room for the internal receiver magnet and processing unit.
I’ve heard the sound of a drill meeting live bone. I couldn’t be in the room.
Conventional hearing aids just don’t do the job; they have to be cranked up so high, and the moulds so often don’t quite fit well enough, or there’s a bit of wax reflecting the sound out, that you get whistling feedback (aka howlround) which means that’s all he’ll hear in that ear. The combination of our inability to sign well and the comparative ineffectiveness of his hearing aids says to us that a cochlear implant is the best way forward. Plus, at this age, the brain is adaptive enough to work out what it’s hearing actually is. Children have had implants at 3, 4, 5, 6 and done well.
An area called the facial recess is then uncovered to reveal the round window. A microscopic drill is then used to open this window and enter the cochlea. If substantial infection is found in the middle ear, the procedure may have to be abandoned.
He hasn’t had a cold recently, has he?
The leadup to the meeting where we were offered the implant for him took ages: months of evaluations every few weeks, or meetings at home, in addition to all the meetings we already have with his Teacher for the Deaf (who is fantastic; shout out for Stephanie Gillingham of Essex Support Services, since she doesn’t get much Googlelurv) and the weekly or fortnightly trips to the hospital for more moulds.
In accessing the round window, the electrode must be channeled between the facial nerve and the chorda tympani (which determines taste). Clipping either of these nerves can lead to loss of facial control on that side, or of taste in the front part of the tongue on that side.
They have monitors for the facial nerve. No such for the chorda.
They called us to a meeting (a few weeks after they’d had their own internal meeting to decide) to tell you whether it’s yea or nay for the implant. Except that while we were waiting, one of the nurses gave us a letter, which she explained was for our doctor, so that baby3 could get a pneumococcal meningitis vaccination pronto. Since we knew that that vaccination is indicated if you’re going to have a cochlear implant, it rather took the surprise away when we went to see the specialist. But that’s OK. Sometimes, you don’t want the surprise. “We think he’ll fly,” the surgeon, Patrick Axon, said. Perhaps not meaning it literally.
The electrode is then introduced through the facial recess into the round window and into the cochlea. The surgeon uses both visual and tactile information to ensure that the electrode is in proper position and that a full insertion of all electrodes has been achieved. The round window and facial recess is then packed with a small plug of muscle to insure that the electrode array stays in place.
You just hope they don’t get what the surgeons call a “gusher”, where the cochlea is filled with fluid at pressure.
Then a few days later there was another meeting – choosing which make of device to implant (Med-El, Advanced Bionics, or Cochlear). This is really difficult. We wanted (1) minimum amount of drilling into the skull required to seat the internal bit (2) most appropriate external system for a toddler (eg, separated into batteries and processor, so they’re not bearing the whole weight on their ear (3) best results from comparative studies (4) best useful number of “channels” (the more channels, the more frequencies and phase changes an implant can provide to the auditory nerve).
In the end I picked the Advanced Bionics model. It’s light on the bone. They’re developing “virtual channels”, which can be implemented by the external processor – so an upgrade could mean better hearing. They can generate a “map” of how his nerve responds to sounds in the operating theatre, so they’ll already have a rough idea of how the processor should be programmed.
What amazed me most in the whole thing is the method by which they determine what the “loudest” output level should be. You’ll remember that the ear has three parts – outer (the bit you see, up to the eardrum), middle, and inner (with the cochlea). The middle ear has three tiny bones – the hammer, anvil and stirrup (stapes) which transmit the sound from the eardrum to the cochlea. The stapes is the last of the trio. But when a sound gets too loud, it triggers a reflex from the auditory nerve to the spinal nerve that controls the stapes, and effectively freezes it. So you can’t hear a sound that’s so loud it’s damaging. What’s fascinating is that the auditory nerve is the 8th spinal nerve; the stapedial nerve is the 7th. So the reflex works up the spine. What happened in evolution to make that happen? What’s more, why should the stapedial reflex work in people who are deaf? Yet it does.
At this point the skin incision is temporarily and partially closed. this allows the surgical and electrophysiological team to test the prosthesis. In the unlikely event that a problem with the electrode placement or a defect in the prosthesis exists the difficulty may be quickly and easily remedied.
So they figure out the ceiling for sound, and they can get an idea of the floor for stimulating the nerve. They can work out the map pretty quickly. That’s the job of the “medical physicist”. Though the people at the centre also said to us that Mr Axon is “quick”. They kept using this word, “quick”, like it would reassure us. “Actually,” I said after a while, “the word we were hoping to hear was ‘accurate’.” He has a very good reputation, though, and he’s done plenty of implants.
The internal receiver is then secured in place to the bone of the skull with sutures and the skin incision is permanently closed. A sterile dressing is placed on the incision and the patient is awakened.
What’s really hard about this is what I said at the beginning. It’s not medically necessary; not now. But we have to make the judgement that it’s going to be necessary for him to leap tall buildings and catch trains that have left the station already. Because the language train rushes along, and waits for nobody. You’re on it or you’re not.
We’ll have to wait six weeks or so before the surgery is expected to have healed enough for the implant to be “switched on”. And then begins the long, slow process of seeing how well he adapts to having it.
And the other thing? He’s still going to be deaf. Take off his processor and he’ll not be able to hear a thing – in the bath, the swimming pool, anywhere with loads of static (such as a soft play centre), in bed. We’re a bag of nerves, stressed, trying to keep calm for the other two kids, trying to get everything organised. And the uncertainty goes forward. Hell.
(To see the procedure with gruesome pics, see http://www.capitaloto.com/surgical.htm. Warning: contains pictures of surgery. Yup, warned you.)