The importance of maintaining facial function combined with improved adjuvant therapies has enabled a more conservative approach toward disease intimately involved with the facial nerve. Although surgical injury or resection is becoming less common, intraoperative sacrifice of the facial nerve still may be required in some select cases. In these circumstances, the best course of action is primary coaptation when tension-free anastomosis is possible. Primary anastomosis, rather than interposition nerve graft, limits the number of splice interfaces to one rather than two. Both suture techniques as well as fibrin glue have been described when anastomosing the intratemporal segment of the facial nerve [13–15]. Typically two or three interrupted 8–0 or 9–0 monofilament sutures are placed through the epineurium to provide approximation and alignment of the fascicular units. However, the intratemporal and intracranial segments of the facial nerve do not have an epineurium layer to assist with anastomosis. In these circumstances both suture repair and sutureless anastomosis techniques have been described. When sutures are used, they are placed superficially through the perineurium with attempts to avoid disruption of the fascicular units as much as possible. In areas where bony anatomy can assists with keeping the nerve fascicles of the proximal and distal ends of the nerve in alignment, absorbable materials such as Gelfoam (Pfizer Inc., New York, NY), collagen matrix, and fibrin adhesive have been used to assist with neural coaptation [15, 16].

Intratemporal facial nerve mobilization can provide added length when required. However, the blood supply received from the periostium of the fallopian canal is compromised with rerouting, placing theoretic limits on the length of consequence-free mobilization. Despite this limitation, primary anastomosis is thought to be optimal for resected segments 18 mm or less [15]. When tension-free closure is not possible, other repair techniques must be employed.

Interposition grafting is the next best option to primary repair. Multiple donor nerves have been described with the most common being the great auricular nerve, medial antebrachial cutaneous nerve, and sural nerve. The great auricular nerve has the advantage of anatomic proximity to JPs and is often times within the surgical field. The path of the great auricular nerve is classically described as originating midway along the SCM coursing superiorly along the lateral aspect of the muscle for approximately 6 cm until it branches into anterior and posterior branches [17]. The medial antebrachial cutaneous nerve and sural nerve provide the advantage of length and are able to provide up to 25 cm of nerve for grafting. The harvesting of these latter nerves requires separate surgical sites with additional morbidities; however, using stair-step incisions provide acceptable cosmetic results. When interposition grafts are anticipated, it is important to counsel patients preoperatively on hypesthesia and loss of sensation in sensory distributions of graft options. The periauricular area is likely to be numb as a result of extensive surgery around the auricle, again favoring the greater auricular nerve. Dorsolateral foot and medial/ulnar surface of the forearm, though well tolerated and “worth” the trade-off for a good donor nerve, are an additional morbidity to be evaluated in the context of patient preference.

With primary repair and interposition grafting, initial return of facial function can be seen at 6 months postoperatively with maximal facial function taking as long as 12–18 months [15]. For these reasons, additional facial reanimation procedures are not typically considered until 1 year postoperatively when satisfactory results have not been obtained. A satisfactory and optimal result in the setting of interposition grafting is considered a House-Brackmann score of III or IV. Therefore, adjuvant procedures may be indicated depending on individual patient’s results and personal expectations.

Transposition grafts are an excellent option for facial nerve reinnervation and are often used when a suitable proximal nerve stump is not available, when interposition grafting has failed, or when facial function has not returned in cases where the nerve was not transected. The timing of this technique is an important factor to consider. Although the utility of earlier intervention is under investigation, most clinicians will allow 12–18 months to pass prior to implementing transposition grafting for dynamic facial reanimation. Proponents for earlier repair site the risk of distal motor end plate degeneration as a reason to intervene sooner; however, this must be balanced with the risk of interrupting a regenerating facial nerve. Electromyography (EMG) can be used to help investigate the progress of neural regeneration. EMG begins to demonstrate fibrillation potentials approximately 2–3 weeks after nerve transection, signifying viable but denervated muscle end plates. As neural regenerating is taking place, EMG demonstrates polyphasic action potentials and observation for facial nerve recovery should be considered. For successful reinnervation, a functional motor end plate-muscle unit must be present; therefore, patients are offered transposition grafting when preoperative work-up reveals fibrillation potentials without signs of polyphasic action potentials on EMG. Conversely, if both fibrillation and polyphasic action potentials are absent, there is irreversible fibrosis and facial muscle atrophy resulting in poor candidacy for reinnervation procedures [15, 17].

Several cranial nerves have been evaluated for use in transposition grafting due to the anatomic location and robust amount of myelinated motor axons. Ipsilateral cranial nerves V, IX, XI, and XII have been used in addition to the contralateral cranial nerve VII [17]. A special consideration that must be made with JPs is that ipsilateral lower cranial nerves may not always be suitable given the potential for disease- and treatment-related injury. Furthermore, paresis of the hypoglossal nerve from transposition in a patient that already has a high vagal nerve injury may have devastating consequences to upper aerodigestive function. As with harvesting sensory nerves for interposition grafts, motor deficits with transposition grafting are important to discuss preoperatively with patients and may need to be addressed postoperatively to limit the morbidity associated with resection of these motor nerves.