How is direct (primary) facial nerve repair performed?

Updated: Nov 28, 2018
  • Author: Tang Ho, MD, MSc; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

The facial nerve is exposed to a length sufficient to permit the exposure and mobility required for performance of the grafting procedure. A parotidectomy incision is made, and the facial nerve is identified as it exits the stylomastoid foramen by using the traditional landmarks (ie, the tragal pointer, the sternocleidomastoid, the posterior belly of the digastric, and the stylomastoid suture).

Once the nerve is identified, it is followed distally as necessary. Meticulous, gentle technique is employed, as in a parotidectomy. If the intratemporal portion of the nerve is involved or requires exposure, it is exposed via a mastoidectomy.

The key to successful nerve grafting is careful coaptation of the nerve ends without tension. Several principles apply, regardless of which specific type of procedure is chosen. The nerve tissue must be handled atraumatically with microinstruments. Magnification with an operating microscope is essential to allow meticulously precise alignment of the nerve ends. A colored background is helpful for facilitating clear visualization of the anatomy.

Typically, 2-3 sutures are carefully placed through the epineurium. Fine (8-0 to 10-0) monofilament permanent suture material is used; this minimizes tissue reactivity. Although epineurial suturing is generally considered the standard, there is some controversy on this point. Perineural and endoneurial or intrafascicular repairs have been advocated, but the data are unclear as to whether these techniques actually offer significant advantages.

The important relation to keep in mind is the size match between the endoneurial surfaces. This must be inspected with magnification; if a mismatch is evident, then one end may be trimmed in a beveled fashion to yield a better match between the surface areas of the ends to be approximated.

In some cases, a nerve segment may be unavailable for reapproximation, either because of resection of a malignancy or because of destruction by trauma. This prevents primary grafting without tension. The problem may be addressed in a number of ways. For example, if the injury site is intracranial or intratemporal, the facial nerve must be rerouted, repaired with a cable graft, or both. In this instance, one may mobilize the facial nerve from the fallopian canal by decorticating it via a transmastoid approach.

If hearing preservation is not a concern, a translabyrinthine approach allows exposure of the entire length of the nerve up to the internal auditory canal. The mastoid tip may be removed to afford the nerve greater mobility. Furthermore, the entire nerve can be rerouted by combining the mastoidectomy with a middle fossa approach, which allows grafting of the proximal portion of the nerve.

Peripheral injuries likewise may necessitate mobilization of the nerve through one of the abovementioned techniques in order to allow primary repair. Repairing the nerve with primary grafting is always preferable when feasible. If it is not feasible, then a cable graft may be used.


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