The Journal of Neuroscience, December 15, 1999, 19(24):11007-11016
Factors Contributing to Preferential Motor Reinnervation in the
Primate Peripheral Nervous System
Roger D.
Madison1, 2, 3,
Simon J.
Archibald1,
Robert
Lacin1, and
Chris
Krarup4
1 Division of Neurosurgery and 2 Department
of Neurobiology, Duke University Medical Center, and
3 Research Service of the Veterans Affairs Medical Center,
Durham, North Carolina 27710, and 4 Department of Clinical
Neurophysiology, University Hospital, Copenhagen, Denmark
Functional recovery after nerve lesions in the peripheral nervous
system requires the accurate regeneration of axons to their original
target end organs. This paper examines axonal regeneration of the
primate median nerve lesioned at the wrist over nerve gap distances of
up to 50 mm. Nerve gaps were bridged by either a sural nerve graft or a
biodegradable collagen nerve guide tube, and recovery was followed for
up to 1100 d. Nondestructive physiological methods were used to
serially examine the number of regenerated motor units, and binomial
statistics were used to compare the observed number of regenerated
motor units with that expected if axonal regeneration of motor neurons
were random. We found up to twice the number of motor units expected by
random regeneration in direct suture and sural cable graft groups but
not in nerve guide repairs of 20 or 50 mm. In all repaired nerves,
aberrant motor axon collaterals were detected in digital sensory nerve territory. The results support the contention that the aberrant fibers
represent collaterals of an
-motor axon, which also innervates muscle. Although the aberrant motor axon collaterals remained in
digital sensory nerve territory for long periods, they remained relatively immature compared with their sibling collateral projecting to muscle, or sensory axons within the digital nerve. The number of
such aberrant motor axon collaterals decreased over time in some repair
groups, suggesting a selective pruning of the inappropriate collateral
under certain conditions.
Key words:
preferential motor reinnervation; regeneration accuracy; nonhuman primate; median nerve; PNS; nerve regeneration
Copyright © 1999 Society for Neuroscience 0270-6474/99/192411007-10$05.00/0