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Inhibition of motor nerve regeneration in a rabbit facial nerve model
C H Yian1, R C Paniello, J Gershon Spector
1Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, St. Louis, MO 63110, U.S.A.
Objectives/Hypothesis:
We hypothesized that intramuscular injection of vincristine into the upper lip selectively prevents reinnervation of the target muscle (quadratus labii superioris) after facial nerve transection.
Study Design:
Prospective controlled experiment.
Methods:
Transection injuries with primary neurorrhaphy were performed just proximal to the buccal and zygomatic branches of both facial nerves in 20 rabbits. The left (experimental) quadratus labii superioris muscle was injected with 200 microg vincristine 72 hours after injury; the right (control) side was injected with saline. Functional, electrophysiological and histological studies were performed 6 weeks after surgery.
Results:
After 6 weeks, the control side had a mean axon count (distal buccal branch) of 1160, conduction velocity of 50.4 m/s, reduction of compound action potential amplitude of 44%, and functional index of 1.67 units. The experimental side had a mean axon count of 265, conduction velocity of 16.5 m/s, reduction of compound action potential amplitude of 88%, and a functional index of 0.176 units. All parameters were significantly reduced by vincristine blockade (P <.05). The zygomatic division (not exposed to vincristine) displayed a trend toward increased axon counts, but this was not statistically significant (P =.131).
Conclusions:
These results demonstrate that reinnervation of a selected muscle can be prevented by injection of vincristine. Enhanced reinnervation of adjacent muscle groups may also occur. Thus, nerve blockade by vincristine may be useful for the prevention of synkinesis.
Insights
Vincristine injection into the quadratus labii superioris muscle selectively blocked reinnervation after facial nerve injury in rabbits. This nerve blockade may prevent synkinesis by targeting specific muscle reinnervation.
Area of Science:
- Neuroscience
- Regenerative Medicine
- Surgical Innovation
Background:
- Facial nerve injuries can lead to synkinesis, an abnormal muscle coordination.
- Targeted prevention of reinnervation is crucial for managing post-injury facial dysfunction.
Purpose of the Study:
- To investigate if intramuscular vincristine injection can selectively prevent reinnervation of the quadratus labii superioris muscle after facial nerve transection.
- To assess the efficacy of vincristine as a nerve blockade agent for preventing synkinesis.
Main Methods:
- A prospective controlled experiment was conducted on 20 rabbits with facial nerve transection and primary neurorrhaphy.
- The experimental side received vincristine injection into the quadratus labii superioris, while the control side received saline.
- Functional, electrophysiological, and histological assessments were performed six weeks post-surgery.
Main Results:
- Vincristine significantly reduced axon count, conduction velocity, and compound action potential amplitude in the target muscle.
- The experimental side showed a marked decrease in functional index compared to the control side.
- A trend towards increased reinnervation in adjacent, non-injected muscle groups was observed.
Conclusions:
- Intramuscular vincristine injection effectively prevents reinnervation of targeted muscles following facial nerve injury.
- Vincristine nerve blockade shows potential for preventing synkinesis by selectively inhibiting nerve regeneration.
- This approach may offer a novel strategy for improving outcomes after facial nerve repair.