By Doug Kaufman, MD Consult, May 17, 2006
ST LOUIS (MD Consult) - Nerve transplant and nerve transfer surgeries are offering new hope for patients who have had extremities paralyzed or severely damaged by accidents.
The surgeries, still relatively new and rare, can replace nerves lost to traumatic injury.
"It''s limb salvage surgery," said Dr Susan Mackinnon, chief of the Division of Plastic and Reconstructive Surgery at Barnes-Jewish Hospital and Washington University School of Medicine, both in St Louis. "So it would take someone from what we call a functional amputation, where the arm is there but it''s dead and lifeless, it just hangs there."
In most cases, the replacement nerves come from cadavers or, occasionally, living donors. Either way, patients must receive immunosuppressant drugs until their nerves regenerate, which can take up to 2 years.
"Right now, because we have to put patients on immunosuppression for a couple of years, and put them at risk with the side effects of the immunosuppression, we only do these nerve transplants in the direst of cases," Dr Mackinnon said. "Or situations where all the nerves are gone and there''s nothing else we can do, no other tricks in our bag."
It''s a question of risk weighed against benefit, she said.
"I won''t put somebody on immunosuppression for 2 years unless it''s necessary to save a limb," Dr Mackinnon said.
Dr Thomas Tung, an assistant professor in the Division of Plastic and Reconstructive Surgery at Barnes-Jewish Hospital and Washington University School of Medicine, recently led a 22-hour, 2-day nerve transplant and muscle transfer surgery on a 21-year-old man who was paralyzed in the mid-upper right arm after a motorcycle accident. The patient lives in North Carolina, but was brought to Barnes-Jewish because the surgery isn''t widely available yet
"Nerve surgery, in itself, is fairly unique," Dr Tung said. "The knowledge and performance of complex reconstruction is still only [done] in a few centers in the country. As far as major, complicated nerve reconstruction, brachial plexus and certainly, nerve transplant, it''s going to be less than a handful. ... Certainly less than 10 centers in the country, probably, are doing that brachial plexus surgery consistently. As far as nerve transplants go, it''s probably less than 5 [centers]."
There is a need for expediency in nerve transplant surgery.
"The sooner you do a transplant, the better," Dr Mackinnon said.
"We only have a certain amount of time to re-energize the muscles, before we can''t recover them anymore," Dr Tung said. "The longer we wait, depending on when they come to see us, 2 to 3 months can make a big difference. We manage a lot of complicated nerve injuries. Even for cases where we don''t use nerve transplant reconstruction, there''s still that time limit. A lot of doctors out there aren''t aware of that."
Many patients still don''t get to specialists like Drs Mackinnon and Tung until "much later than we prefer," Dr Tung said. The whole process, including the initial nerve surgery and the recovery time necessary for the muscles to re-enervate, has to be completed by approximately 1 year after the injury, he added.
"Nerve regeneration is very slow—it''s only about a millimeter a day," Dr Tung said. "Therefore, in most cases, what that usually comes down to is, preferably, we would operate on these patients within 3 to 6 months of their injury. That gives us enough time for regeneration to occur so that it can still reach the muscles by 1 year. But we still get a lot of referrals that are way longer than 6 months—maybe even closer to a year. Which really makes a difference in their outcome."
First-line ER or orthopedic surgeons, working to stabilize the patient, can help nerve transfer specialists by tagging damaged nerves.
"That means suture one end of [the nerve] with a long suture that can be easily found and identified later," Dr Tung said. "... That''s something that many surgeons do for us, but that''s not always the case."
Since most nerves come from cadavers, this can result in extended waiting list delays until a suitable donor is found. The 21-year-old patient, who nearly lost his right arm in the motorcycle accident, underwent a rare living donor nerve transplant, receiving nerves from his mother.
"When he came to us he was in pretty good shape," Dr Tung said. "He was 5 or 6 months after [the accident], so all of his wounds had healed. There were no open areas. The fracture had healed. The blood vessels were reconstructed and had remained open, and he was getting good blood supply to his forearm and hand. ... As far as his nerves go, obviously, he was in bad shape. He was having a lot of pain from the injury, which is common. [Plus], he had some contracture at his shoulder and his elbow and so forth. But a lot of that is very difficult to avoid."
The patient''s chances for recovery can be considered on several levels, Dr Tung said.
"One of them is the muscle recovery we did," he said. "It''s a fairly complicated surgery, and [many] of the muscles that bend the elbow up, like his biceps, were actually injured and removed during his initial [surgery]. So trying to recover that muscle was useless. So ... we tranferred a large muscle from his back, kept its nerve and blood supply intact, so that it still functioned, and just reattached it ... to take the place of his biceps. ... We expect that muscle to work right off the bat and continue working."
The nerve transplants, however, are more unpredictable.
"I think he''s going to get some sensation. That we can predict," Dr Tung said. "It''s not going to be normal sensation, and it never is. But some sensation—when you have nothing, a little is a lot."
Dr Tung does expect the patient to have protective sensation, so he will be able to sense things like heat that could otherwise cause injury.
"At least if we get them protective sensation, although far from normal, they can sense when something is damaging their tissue," he said.
A live donor nerve transfer has a couple of significant advantages over using nerves from a cadaver. It''s usually from someone in the patient''s family, so there isn''t a long wait. In addition, Dr Tung said, the chance of a match is much better. Still, surgeons are limited in what nerves they can take.
"These are expendable nerves that really just provide sensation," he said. "The first choices are usually the sural nerves. These are nerves in the lower leg that provide some sensation to the side of the foot. Those are often our first choice because those are expendable. That area of numbness that results from taking these nerves usually diminishes with time. And there''s no functional impairment."
Tissue and organ transplants—involving permanent transplant of something foreign into the patient''s body—require permanent immunosuppressants, which come with risky side effects, Dr Tung said.
"The nerve transplants are being used to bridge a gap in the injured nerve," he said. "The patient''s own nerves will eventually regenerate through the nerve transplant to reach their own muscles. Once it''s regenerated through the transplanted nerves, ... their need for immunosuppression is only temporary."
Dr Tung expects nerve transfers and transplants to become more commonly available.
"Much of this is the direction of the future in plastic surgery," he said.