What is the hypoglossal-facial anastomosis approach to facial nerve repair?

Updated: Nov 28, 2018
  • Author: Tang Ho, MD, MSc; Chief Editor: Arlen D Meyers, MD, MBA  more...
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The hypoglossal-facial (XII-VII) anastomosis is the preferred approach to reanimating the face when the proximal end of the facial nerve is not available and the peripheral system is still viable. This situation may arise after surgery of the skull base, as in resection of an acoustic neuroma.

If sacrifice of the facial nerve is known at the time of tumor removal, hypoglossal-facial anastomosis is best performed at that time. In cases in which paralysis becomes evident postoperatively, the same principles of timing apply. If no return of function becomes apparent, performing the cranial nerve substitution procedure is appropriate. A successful result is possible many months later, but after 12-18 months, the likelihood of such an outcome is small.

Essentially, 2 options exist for this procedure. Either the hypoglossal nerve is completely transected and connected to the facial nerve, or a partial transection of the hypoglossal nerve is attached to the facial nerve. The latter may be accomplished by means of an interposition cable graft. An alternative is to mobilize the facial nerve via a mastoidectomy and nerve dissection, allowing the facial nerve to be transected more proximally. The facial nerve can then be brought to the partially transected hypoglossal nerve for repair.

The first option, a classic end-to-end anastomosis, involves sectioning the hypoglossal nerve distal to the takeoff of the descendens hypoglossi. This produces reliably improved facial tone and symmetry in more than 90% of patients. The improvement occurs over a period of 4-6 months; it is largely observed in the midface, is less noticeable in the lower face, and is even less significant in the upper face.

On the other hand, hemitongue mobility is impaired. This loss of function must be weighed against the expected gain in facial tone, symmetry, and movement. Spontaneous mimetic function is not expected to return, and some training is necessary to teach the patient to smile by stimulating the hypoglossal nerve. Nevertheless, this procedure is generally well tolerated and fairly successful.

The second option involves the use of jump grafts, in which the hypoglossal nerve is only partially transected and a graft (eg, the great auricular nerve) is used to connect the transected portion of the hypoglossal nerve to the end of the facial nerve. The advantages of this technique include minimization of tongue weakness and a purported decrease in synkinesis. The disadvantages include the need for 2 anastomoses and the availability of fewer nerve cells to “drive” the face. [7]

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