To evaluate the feasibility of neurotisation of facial nerve branches with ipsilateral masseteric nerve: an anatomic study

Abstract

Context: Facial palsy is a common problem encountered in clinical practice. These patients suffer serious functional, cosmetic & psychological problems with impaired ability to communicate. Functional problems around the eye are usually a first priority for the patient with facial palsy.The nerve to masseter as a direct nerve transfer to the zygomatic branch of facial nerve to reinnervate viable facial muscles within a year after the onset of paralysis has been scarcely reported. This study was contemplated to evaluate the feasibility of neurotisation of zygomatic branch of facial nerve with masseteric nerve branch of the trigeminal nerve Objectives: Establishing the anatomic relationship of masseteric nerve to masseteric muscle, determining feasibility of neurotisation of zygomatic branch of facial nerve using the nerve to the masseter and establishing fascicular correlation of the donor and the recipient nerves.

Materials and methods: Ninteen hemi-faces in ten fresh cadavers (6 Male and 4 Female)were dissected in a forensic morgue and access was by a standard preauricular incision and anterior skin flap is elevated in a subcutaneous plane. Facial nerve and its two main divisions are dissected in its full A*/extratemporal course. Zygomatic branch dissected upto zygomatic arch and the nerve to the masseter is identified within the masseter muscle, dissected proximodistally to isolate it. Feasibility of transfer of this masseteric nerve to the zygomatic branch without using nerve graft is determined. At the completion of dissection, the ends of both nerves are sent for HPE analysis to determine fascicular anatomy and count.

Results: The dissection of massteric nerve was done taking into consideration of 3 axes, that is anteroposterior (x), vertical (y) axes and mediolateral(z) for locating the nerve and for standardization of the dissection. The nerve was cut and stored in glutaraldehyde solution and subjected to histopathologic examination after fixing and staining with Haematoxilin-eosin stain. Donor masseter neve has 7-10 fascicles. Recipient zygomatic branch has 2-3 fascicles. And the buccal branch has 5-6 fascicles.

Conclusion: The use of the nerve to masseter offers a simpler ipsilateral alternative for neurotisation of the facial nerve branches in patients who have an early facial nerve paralysis.

Keywords: Facial palsy; Masseter nerve; Nerve grafting; Orbicularis oculi.

[Table/Fig-1]:

Axis

[Table/Fig-2]:

Anteroposterior plane

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Vertical dimensions

[Table/Fig-5,6]:

Medio lateral plane and Length of masseteric nerve

[Table/Fig-7]:

Masseteric nerve complete dissection

[Table/Fig-8]:

Direct coaptation

[Table/Fig-9]:

Direct coaptation

[Table/Fig-10]:

Histopathological examination of Masseteric nerve

[Table/Fig-11]:

Histopathological examination of Buccal nerve

[Table/Fig-12]:

Histopathological examination of Zygomatic branch of Facial nerve