Rerouting Working Nerves To Restore Hand Function

May 18, 2012
Originally published on May 18, 2012 12:54 pm
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It's interesting that while the robotic arm picked up most of the attention this week, doctors at Washington University School of Medicine in St. Louis have come up with another unique way to restore mobility in paralysis patients. The research involves a 71-year-old man who suffered a spinal cord injury. So he lost complete control over his hands.

Doctors sought a way to restore the broken nerve connection and give the man back the use of his hand, and this time instead of operating on the spine itself, trying to hook the nerves back together, surgeons rewired the severed nerves in his hand to functional nerves in the patient's upper arm, creating a fresh, new connection between his brain and hand.

And after intensive physical therapy, the man is now able to feed himself and even write with some assistance. Dr. Ida Fox is assistant professor of plastic and reconstructive surgery at Washington University School of Medicine. She joins us from St. Louis. And the procedure was describe in the Journal of Neurosurgery. Welcome to SCIENCE FRIDAY.

IDA FOX: Thank you.

FLATOW: So your approach, or the approach - you didn't do this one yourself, but the approach of the surgeons was not to operate on the spinal cord and the severed cord but to take the nerves in the muscles that still function in the upper part of the arm and connect the nerves from the hand to those healthy, functioning nerves.

FOX: Correct.

FLATOW: That's correct?

FOX: That is correct.

FLATOW: So bypassing the whole need to go through the spinal cord.

FOX: That's right.

FLATOW: Wow, is this a hard approach?

FOX: So the surgery is a nerve transfer surgery, and we use it a lot for injuries in the arm, and it's really just applying it to this different patient population. So the surgery is not terribly difficult for somebody who does hand surgery every day. It is microsurgery, it does require the use of special instruments, and the nerves themselves are about the size of a piece of angel hair pasta. So it does take some precision.

But it is not attempting to restore function to the spinal cord or central nervous system, which we really haven't figured out how to fix or make heal itself.

FLATOW: So these nerves in the upper arm that are still functioning, they control muscles in the upper arm.

FOX: Correct.

FLATOW: There are a lot of different nerves up there.

FOX: Yes.

FLATOW: And so you - is it a question of picking out which nerves you want to attach to the hand to get to make it function again?

FOX: Well, in these particular patients, they only have some nerves that are working that their brain can still control, and those are the nerves that come off the spinal cord at a level above the injury. And the one in particular that we stole from was the brachialis muscle's nerve, and that's a muscle that you don't hear about much, but it works just like the biceps muscle to bend the elbow.

And we stole that extra elbow-bender and swapper it over to give function back to the thumb and index finger, and that's what we're planning on doing in these patients who have C-6 and C-7 spinal cord injuries. So that's on a level in the cervical cord. They still have the ability to bend the elbow, but now to use their finger independently.

FLATOW: So will you be able to give them that ability to use their fingers?

FOX: Yes.

FLATOW: And do they get sensation in them also?

FOX: Most patients have some sensation because of their level of injury. They have some preserved sensation usually at the thumb and index finger. So that's not as much of an issue, although certainly nerve transfers could also be used to restore sensation in some cases.

FLATOW: You know, the obvious question is, if you can do this in the arm and the hands, why not in other parts of the body?

FOX: So that is the critical difference between a peripheral nerve injury and a spinal cord injury. So in the spinal cord injury, the nerves below the level of injury are still connected to the muscles and keep the muscles alive. In a peripheral nerve injury which occurs as soon as we cut that nerve to swap it over, we have to necessarily create that injury of a nerve in the periphery. And then the clock starts ticking. And if you don't get the nerve to sprout back to the muscle within a year after the time you cut it, then that muscle will become unresponsive. So as much as we would like to transfer a nerve down to the legs, the distance is too great, and that nerve fiber won't get there in time for the muscle to respond.

FLATOW: So you say that the nerve does regenerate itself?

FOX: Peripheral nerves do regenerate, and that's what makes us so novel, is we're really harnessing the unique attributes of both types of injuries to make some success and to restore function to these patients.

FLATOW: So while you've grafted the nerves, the nerve is regenerating itself also?

FOX: Yes. So we actually cut the nerve, so...

FLATOW: Right.

FOX: ...we have one sprout that the brain still controls. We cut that piece of spaghetti and rewire it into another nerve that's going to a muscle that the brain no longer could control after the injury. It grows from the point at which we cut it, grows back down that tube of nerve, gets down to the muscle, and that growth occurs at about an inch a day, which is why it takes some time. You don't see it immediately. The patients have to have that nerve growth, and then they have to retrain to make their brain relearn what used to bend their elbow is now telling the muscles that bend the thumb and index finger to function.

FLATOW: Well, you may not think that's fast, an inch a day...


FLATOW: ...when I certainly think that's pretty fast.



FOX: It's better than nothing.

FLATOW: It's...

FOX: It is six to 12 months before they really get meaningful function.

FLATOW: And how much function can they expect?

FOX: It will vary on the patient, so we have done another one of these transfers, but it's too early to see the results. And that one I did, and we actually transferred to both the thumb and index finger, as well as some other muscles that go to the fingers and muscle that goes to bend the wrist. So I will be able to tell you that in about six to 12 months.

FLATOW: Interesting. You know, you say this is a common type of operation. Why hasn't someone thought of this before?

FOX: Well, it's a lot of lucky chance, so my colleague, Susan MacKinnon, who did the first one of these surgeries, I don't think the patient would mind us telling, but that patient was actually a surgeon. He's consented to have his name publicized, and he was a surgeon who is friends with the plastic surgeon that she knows, and that plastic surgeon brought his friend who was a new quadriplegic to Dr. MacKinnon's office and said this is my friend from my, I think, internship year.

He's now a quadriplegic. And, Susan, you have to do something to fix him. That's the story she told me. And she looked at him and said I don't treat spinal cord injury patients. I don't, certainly, treat quadriplegics. But for whatever reason, at that moment, with that particular patient, the idea came into her mind to use the technology that we all know well as plastic surgeons and hand surgeons, which is to harness the use of nerve transfers in this particular patient population.

FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR...

FOX: Thank you.

FLATOW: ...talking with Dr. Ida Fox about some fascinating surgery. Now, I said other parts of the body, could you not do this for people who have lost movement in their legs, find a spot where, you know, the - you might be able to transfer some of that leg movement into nerves that are still around? And is that still your response that the nerves are not going to grow fast enough to do that?

FOX: If they have a partial injury, low down and they're missing a specific function, I suppose there's the possibility of making their function slightly better. But in somebody who's a paraplegic from the waist or below, you would have to steal something from the arm and get it to grow down to the leg, and that distance in the torso in adults is too far.

FLATOW: Unless you could find something that makes the nerve grow faster.

FOX: Correct. And that's the next frontier.

FLATOW: Tell us about that.

FOX: So peripheral nerve regeneration is frustrating because it does take time and because we can't keep the muscle alive to accept that regenerating sprout. And there has been a lot of work to figure out ways to not only make nerves regenerate faster but to also preserve the muscle so it will respond once the nerve gets there, even if it is more than that magic of 12 to perhaps 18 months.

FLATOW: 1-800-989-8255. Let's get a phone call or two in. Caroline from Anchorage. Hi, Caroline.

CAROLINE: Yes, hi. This is Caroline. Thank you so much for this program. You've pretty much answered the question while I was holding, but the idea of nerves growing, finding other paths, if that's the way it's done, is that not similar to what happens with capillaries? And also, would the connection with the mind be able to stimulate the growth? I know that may seem farfetched, but this whole thing is science fiction. So that's basically it.


CAROLINE: Can people be in - can the paraplegic or the person that you're operating on, can they be able to stimulate their own growth by just thinking about it or working on it?

FOX: So one thing that the therapist tells patients is strengthen the donor. So in this case, we're taking a muscle which bends the elbow, so even before that nerve gets back down to the muscle we transferred it to, we will ask him to work on strengthening his biceps or working on bending at the elbow because that will sort of re-establish that connection, make that muscle strong, theoretically, in their mind, so that they can then relearn the new tasks. So asking about the brain and its role is not at all an unrelated question. And that part is really important because that's sort of the part we don't know is how long it takes for people...

FLATOW: Right.

FOX: relearn to make one nerve do a function of a different nerve. So that's very important.

FLATOW: Just before we go, we have about a few seconds left. I have to make sure you - did you mean to say an inch a month instead of an inch a day?

FOX: Yes. I meant to say an inch a month, a millimeter a day.


FOX: Thank you for clarifying.

FLATOW: Well, we got a - Christopher Hinkle(ph) tweeted us and let us know that was something we should be clarifying with you. Thank you very much. It's fascinating work. Thank you. We'll keep in touch, OK?

FOX: Thank you.

FLATOW: Dr. Ida Fox, assistant professor of plastic and reconstructive surgery at Washington University School of Medicine in Saint Louis. We're going to take a break and talk with Elon Musk about some fascinating space travel coming up tomorrow. Stay with us. We'll be right back. Transcript provided by NPR, Copyright NPR.