Nerves Controlling Muscles Are Best Repaired With Similar Nerves

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Nerves Controlling Muscles Are Best Repaired With Similar Nerves

http://www.sciencedaily.com/releases/2007/05/070511203204.htm

When repairing severed or damaged motor nerves with a donor nerve

graft, surgeons have traditionally used a sensory nerve from another

area of the patient's body. However, these patients often do not

fully regain function in the injured area.

Surgeon Borschel has found that larger nerve fibers of motor

nerves are better for regeneration than smaller sensory nerve

fibers.

But now a team of surgeons at Washington University School of

Medicine in St. Louis and -Jewish Hospital has found that

repairing a motor nerve in rats with an intact motor nerve yields

better results than using a sensory nerve. The research appeared in

the March issue of the journal Microsurgery.

Motor nerves control movement in the muscles, while sensory nerves

receive sensory stimuli, such as pain. A significant difference

between the two types of nerves is that motor nerves have much

larger axons, the thread-like extensions of the nerve cell that

carry nerve impulses throughout the body.

The researchers, led by H. Borschel, M.D., a plastic and

reconstructive surgeon at the School of Medicine and senior author

of the paper, defines the question of this work as seeking to

determine why motor nerves were regenerating more successfully than

sensory nerves. Was it because of the nerve's own structure, or

architecture, or because supporting cells such as Schwann cells were

boosting the regeneration "

To find an answer, the researchers broke down the nerve architecture

by chopping up motor, sensory and mixed nerves. They divided the

minced nerves into groups by type, inserted the mush into tiny

silicone tubes and encouraged severed motor nerves to regenerate

through the mixtures in the tubes.

The researchers found that disrupting the nerve's architecture by

mincing it abolished the benefit of repairing a motor nerve with an

intact motor nerve. " It turned out there was no difference in

regeneration using motor versus sensory nerves through the chopped-

nerve tissue, " Borschel said.

Several factors contributed to the results, he said. " We know that

the axons, or nerve fibers, in the motor nerves are bigger, while

the sensory nerve fibers are smaller, " he said. " When the nerves are

trying to regenerate using a motor nerve as a graft, it's easier for

them to use the larger axons of another motor nerve, although the

reason why is not clear. "

The results could eventually translate into improved treatment for

humans who have nerve damage from industrial, recreational or auto

accidents.

" The research data is very compelling, " Borschel said. " The evidence

presented through this study could represent a paradigm shift from

what we currently do in the operating room. The current standard of

treatment for fixing a gap in a motor nerve is to use a sensory

nerve, but we believe that if you use a motor nerve instead of a

sensory nerve, then the outcome would be better. "

The surgeons in the Division of Plastic and Reconstructive Surgery

have begun using motor nerves grafts in limited patient cases with

good results, Borschel said, but to clearly demonstrate the

difference between motor nerve grafting and sensory nerve grafting

in humans, much more study is needed.

One obstacle to the use of more motor nerve grafts is that the human

body has a limited number of expendable motor nerves. Currently,

surgeons are able to use the nerve from the gracilis muscle along

the inner thigh or the latissimus dorsi along the side of the torso.

" This study, in conjunction with other related work from our

laboratory, will likely result in a shift away from the use of

traditional sensory nerve grafts to the much more permissive motor

nerve grafts for reconstruction of injury, " said E. Mackinnon,

M.D., the Sydney M., Jr. and H. Shoenberg Professor and Head

of the Division of Plastic and Reconstructive Surgery at the School

of Medicine.

Lloyd BM, Luginbuhl RD, Brenner MJ, Rocque BG, Tung TH, Myckatyn TM,

Hunter DA, Mackinnon SE, Borschel GH. Use of motor nerve material in

peripheral nerve repair with conduits. Microsurgery, Volume 27,

Issue 2.

Funding from the National Institutes of Health supported this

research.