Impact of different types of facial nerve reconstruction on the recovery of motor function: an experimental study in adult rats.
OBJECTIVE
Poor functional recovery after facial nerve reconstruction is characterized by mass movements and synkinesis. Major reasons are axonal sprouting from the regenerating axons leading to misdirected reinnervation and hyperinnervation as well as polyinnervation of the mimic muscle end plates. We analyzed whether or not the type of nerve reconstruction influenced these pathological phenomena.


METHODS
The experiments were performed on 48 adult rats divided into four groups. One group served as an intact control and the experimental groups were subjected to facial-facial nerve repair (FFN), facial nerve interpositional grafting, and hypoglossal-facial nerve repair (HFN), with 12 subjects in each group. Two months later, functional recovery was measured by biometrical motion analysis of whisking. Retrograde fluorescence labeling of the brainstem motoneurons was used to quantify the degree of collateral axonal branching at the lesion site. Fluorescence histochemistry of sections through the levator labii superioris muscle was performed to quantify the degree of polyinnervation after surgery.


RESULTS
The type of nerve reconstruction significantly influenced the regeneration. The whisking amplitude did not recover completely regardless of the type of reconstruction. The angular velocity and angular acceleration of the vibrissal hairs showed a full recovery after facial nerve interpositional grafting and HFN, whereas these parameters remained decreased after FFN. Significantly less collateral branching and polyinnervation of the end plates were determined after grafting and HFN than after FFN.


CONCLUSIONS
No type of immediate facial nerve reconstruction results in a full recovery in the rat. However, the morphological and functional recovery was significantly better after grafting and HFN than after FFN.
Guntinas-Lichius
Orlando
O
Department of Otorhinolaryngology, Friedrich-Schiller-University Jena, Jena, Germany. orlando.guntinas@med.uni-jena.de
Hundeshagen
Gregor
G
Paling
Thomas
T
Angelov
Doychin N
DN
D000578:Amidines; D000596:Amino Acids / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D005155:Facial Nerve Diseases / Q000601:surgery*; D009046:Motor Neurons / Q000502:physiology*; D009121:Muscle Denervation / Q000379:methods; D009416:Nerve Regeneration / Q000502:physiology*; D051381:Rats; D019651:Plastic Surgery Procedures / Q000379:methods*; D020127:Recovery of Function / Q000502:physiology*; D015050:Zygoma / Q000378:metabolism
D000578:Amidines; D000596:Amino Acids; C031455:diamidino compound 253-50; C098463:dolaisoleucine