April 2020 HSC Section 4 - Plastic and Reconstructive Problems

Management of Flaccid Facial Paralysis

include the ability to restore resting facial tone, the capacity to produce robust dy- namic motion (ie, donor nerve axonal count), the ability to achieve consistent results, ease of use, and the degree of donor site morbidity. The aim of dual innervation tech- niques is to use multiple donor cranial nerves with the intention of allowing the individ- ual properties of each donor nerve to complement each other and avoid drawbacks inherent to any individual donor nerve when used on its own. Yamamoto and colleagues 27 first reported this approach for rehabilitation of facial paralysis subject. They described the use of the hypoglossal nerve to supple- ment proximal facial nerve for donor nerve sources in 8 subjects with both com- plete and incomplete facial paralysis and salvageable facial musculature. 27 The investigators termed this approach supercharging because the donor hypoglossal nerve augmented the attenuated neural input from the damaged facial nerve. Yamamoto and colleagues 27 reported improvement from House-Brackmann grade IV–VI to grade II–III in their small case series of this technique, and did not observe any mass synkinesis associated with use of the hypoglossal donor nerve. Use of the motor branch to the masseter muscle has gained popularity for use in facial reanimation procedures due to its ability to provide expedient regrowth of donor nerve axons and consistent dynamic motor outcomes ( Fig. 2 ). However, evidence sug- gests that the motor nerve to masseter has limited ability to restore baseline resting tone, especially in patients with severe flaccid facial paralysis. 28 A recent report by Owusu and colleagues 29 described a series of 9 subjects who underwent immediate facial nerve repair following radical parotidectomy with concurrent cable grafting and masseteric to facial transposition. In their series, the motor branch to the masseteric nerve was coapted to a midfacial branch of the facial nerve controlling smile, whereas the cable graft was used to repair the remaining branches ( Fig. 3 A). This method of dual innervation combined the advantages of being able to restore tone to the periocular area and upper facial with the cable graft, whereas the masseteric nerve was used for restoration of dynamic motion to the oral commissure (ie, reanimate smile). All sub- jects were found to have return of oral commissure motion within 7 months after

Fig. 2. Transposition of masseteric nerve to facial nerve trunk. Selective cervical branch neu- rectomy may be performed simultaneously to reduce synkinesis involving the platysma.

163