Trigeminal Sensory Supply Is Essential for Motor Recovery after Facial Nerve Injury |
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Authors: | Svenja Rink-Notzon Jannika Reuscher Klaus Nohroudi Marilena Manthou Tessa Gordon Doychin N. Angelov |
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Affiliation: | 1.Department of Prosthetic Dentistry, School of Dental and Oral Medicine, University of Cologne, 50931 Cologne, Germany;2.Anatomical Institute II, University of Cologne, 50931 Cologne, Germany;3.Anatomical Institute I, University of Cologne, 50931 Cologne, Germany;4.Department of Histology and Embryology, Aristotle University Thessaloniki, GR-541 24 Thessaloniki, Greece;5.Department of Surgery, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada |
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Abstract: | Recovery of mimic function after facial nerve transection is poor. The successful regrowth of regenerating motor nerve fibers to reinnervate their targets is compromised by (i) poor axonal navigation and excessive collateral branching, (ii) abnormal exchange of nerve impulses between adjacent regrowing axons, namely axonal crosstalk, and (iii) insufficient synaptic input to the axotomized facial motoneurons. As a result, axotomized motoneurons become hyperexcitable but unable to discharge. We review our findings, which have addressed the poor return of mimic function after facial nerve injuries, by testing the hypothesized detrimental component, and we propose that intensifying the trigeminal sensory input to axotomized and electrophysiologically silent facial motoneurons improves the specificity of the reinnervation of appropriate targets. We compared behavioral, functional, and morphological parameters after single reconstructive surgery of the facial nerve (or its buccal branch) with those obtained after identical facial nerve surgery, but combined with direct or indirect stimulation of the ipsilateral infraorbital nerve. We found that both methods of trigeminal sensory stimulation, i.e., stimulation of the vibrissal hairs and manual stimulation of the whisker pad, were beneficial for the outcome through improvement of the quality of target reinnervation and recovery of vibrissal motor performance. |
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Keywords: | rat facial nerve motoneuron axotomy trigeminal nerve stimulation vibrissal whisking motion analysis recovery of function morphological correlation |
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