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The first step in preparing for nerve transplantation is
to identify precisely where the nerve damage has occurred.
Doctors do that using a variety of imaging techniques,
clinical exams and other tests, such as electromyography.
Once they know where they need to insert
the transplanted nerve, they first look for a way to harvest
one from the patient. "The sural nerve runs down the
back of the leg, just under the skin--we joke that it is
God's little gift to microsurgery," comments Dr. Elkwood.
"It is a small, straight, long, good-caliber nerve, and
its only function is to give some sensation to the outside
of your ankle. Almost every procedure starts out with the
harvest of the sural nerve."
The transplanted nerve segment is attached
using microsurgery. "All nerve surgery is microsurgery,"
says Dr. Elkwood. "The nerve endings are so small and they
need to be sewn in such a precise way that you have to
have magnification to do it properly. We use a suture that's
finer than a human hair and a glue made from cow's blood
that has the consistency of a fried egg."
Sometimes, however, the sural nerve is not
long enough to provide a bridge between damaged nerve endings
in, say, an arm or leg. "A living donor, such as a relative,
is the next best choice," says Dr. Elkwood. "Cadaver
donors can also work quite well."
"Even if a transplanted nerve is someone
else's, over time the recipient's body will replace the
outer insulation on that nerve with his or her own. The
body makes that graft a part of itself. So, although we
do need to give people immunosuppressive drugs for the
first year or so after a donor transplant, eventually they
can stop taking them. It's pretty neat."
Reproduced with permission from Diabetes
Focus, copyright Medizine Inc. 2006
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