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The nerve to the mylohyoid as a donor for facial nerve reanimation procedures: a cadaveric feasibility study.
by Tubbs RS, Loukas M, Shoja MM, Acakpo-Satchivi L, Wellons JC, Blount JP, Oakes WJJournal of neurosurgery.
Article Abstract:
OBJECT: Facial nerve injury with resultant facial muscle paralysis is disfiguring and disabling. Reanimation of the facial nerve has been performed using different regional nerves. The nerve to the mylohyoid has not been previously explored as a donor nerve for facial nerve reanimation procedures. METHODS: Five fresh adult human cadavers (10 sides) were dissected to identify an additional nerve donor candidate for facial nerve neurotization. Using a curvilinear cervicofacial skin incision, the nerve to the mylohyoid and facial nerve were identified. The nerve to the mylohyoid was transected at its point of entrance into the anterior belly of the digastric muscle. Measurements were made of the length and diameter of the nerve to the mylohyoid, and this nerve was repositioned superiorly to the various temporofacial and cervicofacial parts of the extracranial branches of the facial nerve. All specimens had a nerve to the mylohyoid. The mean length of this nerve available inferior to the mandible was 5.5 cm and the mean diameter was 1 mm. In all specimens, the nerve to the mylohyoid reached the facial nerve stem and the temporofacial and cervicofacial trunks without tension. No gross evidence of injury to surrounding neurovascular structures was identified. CONCLUSIONS: To the authors' knowledge, the use of the nerve to the mylohyoid for facial nerve reanimation has not been explored previously. Based on the results of this cadaveric study, the use of the nerve to the mylohyoid may be considered for facial nerve reanimation procedures.
The nerve to the mylohyoid as a donor for facial nerve reanimation procedures: a cadaveric feasibility study.
By: Anonymous - Wed 4/25/2007 PMCommon alternatives when the proximal stump of the facial nerve is not available include the hypoglossal nerve, cervical plexus, and branch to the masseter(trigeminal nerve).
Why would one preferably opt for the mylogyoid branch? The authors discuss that the masseteric branch or hypoglossal nerve are not optimal donors because they may cause unwanted facial movements during chewing or speaking. It is uncertain if similar co-contractions after mylohyoid nerve transfer will also occur, speciifcally when the jaw is depressed. They also discuss that with hypoglossal and masseteric transfers the jaw either needs to clenched (masseter) or tongue pressed to the side of the mouth (hypoglossal) to initiate a smile. This often true, however, are these initiation movements worse then potentially having to depress the jaw to smile, which may look more awkward? Finally, the mylohyoid branch was quoted to have about 2000 myelinated axons, while the facial has about 7000. Is this enough? Probably considering it is a "pure" motor nerve, however, properly coapting this much smaller nerve to the parent facial may be difficult. The mylohyoid branch may be more appropriate for selective reinnervation of facial nerve divisions.