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Facial Nerve Regeneration Through Cross-Face Nerve Grafts Is Improved by End-to-Side Coaptation of Sensory Nerves to the Graft
Eva Placheta; Christine Weber; Matthew D. Wood; Tessa Gordon; Manfred Frey; Gregory H. Borschel
Division of Plastic Surgery, The Hospital for Sick Children, Toronto, ON, Canada
Introduction: In unilateral facial palsy, cross-face nerve grafts are used for emotional facial reanimation. Facial nerve regeneration through cross-face nerve grafts takes several months and the functional results are sometimes inadequate. We hypothesize that the loss of the pro-regenerative state of the Schwann cells of long nerve grafts, such as cross-face nerve grafts, results in incomplete nerve regeneration. We propose that donor axons from adjacent sensory nerves can keep Schwann cells of cross-face nerve grafts in a growth-permissive state and increase axon regeneration.
Materials and Methods: The common peroneal (fibular) nerve was used as the cross-face nerve graft in the rat model. The 30mm-long nerve graft was coapted end-to-end to the right buccal branch of the facial nerve (donor nerve branch) and the buccal and marginal mandibular branch of the left facial nerve (recipient nerve branches). In the other experimental group, end-to-side neurorrhaphies of both sensory occipital nerves to the cross-face nerve graft (through an epineural window) were performed. The facial nerve regeneration was imaged in-vivo every 4 weeks postoperatively in transgenic Thy1-GFP rats, which express GFP in their neural structures, using a GFP-MDS-96/BN excitation stand (BLS Ltd). After 16 weeks, the regenerating axons were retrogradely labeled distal to the cross-face nerve graft. Both experimental groups were compared for statistical significance using t-tests of independent samples (p<0.05).
Results: Facial nerve regeneration through cross-face nerve grafts was successfully macroscopically imaged in-vivo. After 8 weeks of regeneration, the axons in the experimental group with end-to-side coaptations of the occipital nerves reached the recipient facial nerve branches, whereas they did not cross the distal suture site of the nerve graft in the group without end-to-side coaptation of the sensory nerves. Retrograde labeling revealed that the regeneration of facial nerve axons was increased in the experimental group with end-to-side neurorrhaphy of the occipital nerves to the cross-face nerve graft.
Conclusion: Axon regeneration through the cross-face nerve grafts was macroscopically imaged in-vivo in transgenic Thy-1 GFP rats. Motor axon regeneration through cross-face nerve grafts was improved by end-to-side coaptation of the sensory occipital nerves to the nerve graft.
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