Hypoglossal Facial Anastomosis

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Chapter 62 Hypoglossal Facial Anastomosis

Eric P. Wilkinson, William M. Luxford

image Videos corresponding to this chapter are available online at www.expertconsult.com.

Facial nerve paralysis is a debilitating problem cosmetically and functionally. During the course of otologic and neurotologic surgery, sacrifice of the facial nerve is sometimes necessary, and may occur inadvertently, despite meticulous surgical technique. In these cases, one must be prepared to rehabilitate and restore function as much as possible. Direct repair of the injured nerve is currently the best option available to re-establish facial function. If a direct approximation of the nerve ends is impossible, a graft connecting the two ends is the next best choice.

There are situations in which neither of these options is feasible. Perhaps the most common of these involves the extirpation of cerebellopontine angle tumors, in which the facial nerve is severed at the brainstem, and there is no proximal stump present for connection of a graft. There are also cases in which a very attenuated but intact nerve regains no function. In these situations, an alternative to direct repair and nerve grafting is required.

Ideally, facial nerve restoration procedures should provide normal facial tone and symmetry, strong volitional and emotional facial movement, protection of the eye, facilitation of mastication, avoidance of dyskinesias, and no additional motor deficits. Even immediate direct anastomosis cannot fulfill these criteria, however. Several methods to restore some facial function have been developed that require neither direct repair nor grafting. These include cross-facial nerve grafting; nerve/muscle pedicle grafts; and nerve substitutions, such as phrenic, accessory, hypoglossal, and ansa cervicalis.

Connection of a graft with the normal facial nerve followed by redirection of some of these fibers to the paralyzed side is termed cross-facial grafting. This method can provide some symmetry of movement, while avoiding other motor deficits. This procedure partially compromises the normal nerve, however, and provides a scant supply of neural elements to the recipient muscles, leading to inconsistent results.1,2 As a consequence, this procedure has not met with widespread acceptance.3,4 Combinations of cross-facial grafting and traditional nerve substitutions may also be employed.5–8

Nerve/muscle pedicle grafts such as temporalis muscle transfer have been used with some success, but have also yielded inconsistent results.9 Because the results of nerve/muscle pedicle grafts and cross-facial grafts have been disappointing, modifications of these procedures have been developed that use combination cross-facial grafting and microvascular free muscle flaps for facial reanimation.9,10 More recently, a modification of the traditional temporalis transfer has been used that incorporates the temporalis tendon alone instead of a portion of the muscle.11

Nerve substitution procedures provide a large supply of axons to the recipient muscles, and are generally technically facile. The results are consistent and predictable. The major disadvantages include the lack of emotional facial function and the donor nerve deficit. Because of the close relationship of tongue movement to facial movement, the hypoglossal/facial (CN XII/VII) anastomosis has proved to be a useful procedure in cases of facial paralysis in which a direct repair or graft is impossible. This procedure produces varying degrees of tongue dysfunction, based on the amount of hypoglossal nerve donated for transposition to the facial nerve. Newer techniques have been designed with the goal of preserving tongue function. This chapter focuses on the hypoglossal/facial anastomosis.

PATIENT SELECTION

Patients with facial paralysis must receive a detailed evaluation to determine the etiology of the paralysis. In some cases, the cause is obvious, as in resection of the nerve in the course of removal of a neoplasm. The evaluation of facial palsy of unknown cause is beyond the scope of this chapter. Careful evaluation should precede any reanimation procedure, however, to avoid missing treatable disease, and to avoid destruction of a nerve that has potential for return of function.

In cases of known facial nerve discontinuity in which direct repair or grafting is impossible, the CN XII/VII anastomosis should be performed as soon as reasonably possible. Muscle atrophy and degeneration proceed rapidly after denervation.12 Early repair provides axonal growth to the muscles and limits the amount of muscle degeneration.

The severed nerve also begins to experience fibrosis.13,14 In early anastomoses, new axons fill the nerve sheath before fibrosis and potentially allow a greater supply of axons to the muscles. Although earlier anastomosis gives a better functional result, the CN XII/VII anastomosis is also effective after a prolonged denervation and should be considered up to 2.5 years after injury.4,15 Return of function can occur 4.5 years after injury.16

In other patients in whom the continuity of the nerve is in question, including patients who sustain trauma, have idiopathic palsy, and have nerves damaged in surgery, it is prudent to wait at least 1 year to ensure that no return of function occurs. Electrophysiologic testing is helpful in determining the innervation and viability of facial muscles. A positive response to electroneuronography or evoked electromyography indicates that at least some motor end plates are functional. These patients should be given the longest possible time to show improvement in function. Some of these patients have so few remaining neural elements, however, that they never regain any useful function. In this situation, a CN XII/VII graft helps provide a sufficient amount of neuronal input to the muscles.

Electromyography helps detect polyphasic action potentials indicative of reinnervation, and fibrillation potentials indicative of denervation. In cases of long-standing paralysis (>2.5 years), a muscle biopsy in addition to electromyography may be useful to determine viability, atrophy, and fibrosis. In cases of severe muscle atrophy and neural fibrosis, the results of any reinnervation procedure would be poor, and muscle transfers and other augmenting procedures should be considered.

The clinician should also consider the status of the contralateral twelfth cranial nerve when deciding on the CN XII/VII transposition. Contralateral hypoglossal paralysis is a contraindication to the standard CN XII/VII transposition, as are multiple lower cranial nerve deficits that already compromise swallowing and speech.

SURGICAL TECHNIQUE

In addition to standard head and neck surgical instrumentation, hypoglossal facial anastomosis requires jeweler’s forceps to handle the nerve ends, a Castroviejo needle holder, and microforceps for knot tying. A sterile tongue blade is useful to improve visibility when the ends of the nerves are anastomosed under microscopic vision.

After satisfactory general endotracheal anesthesia has been obtained with the patient in the supine position, the neck is extended, and the face is turned toward the side opposite the paralysis. The ear, face, and neck are prepared and draped using sterile technique. A standard lazy S parotidectomy incision is made in the preauricular crease and extended behind the lobule and then anteriorly about 2 cm below the angle of the mandible (Fig. 62-1). In cases where the patient has had a prior postauricular incision for craniotomy, the postauricular incision may also be used for the superior aspect of the incision. This is particularly true if a mobilization of the facial nerve out of the fallopian canal is planned.

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FIGURE 62-1 Lazy S standard parotidectomy incision is used in this procedure. Scar is well hidden in preauricular crease and in natural skin crease in submandibular area.

Skin flaps are raised anteriorly and posteriorly. The parotid is mobilized from the anterior border of the sternocleidomastoid muscle and from the external auditory canal. The angle formed by the cartilage of the anterior external canal, known as the tragal pointer, is followed medially to the stylomastoid foramen, where the facial nerve exits the temporal bone. The nerve is dissected from the parotid gland to expose the pes anserinus and free the main trunk from the gland. The nerve is transected at the stylomastoid foramen.

The hypoglossal nerve is identified by retracting the sternocleidomastoid muscle posteriorly and exposing the great vessels of the neck. The posterior belly of the digastric muscle is retracted superiorly, and the hypoglossal nerve is found coursing inferiorly with the great vessels and then turning anteriorly as it supplies the ansa cervicalis, which descends in the carotid sheath (Fig. 62-2). The hypoglossal nerve is followed anteriorly and medially as it enters the tongue muscle. The nerve is freed from its fascial attachments in the neck. The network of veins and arteries entering the internal jugular vein and external carotid artery should be controlled during this maneuver. After the nerve is freed from its attachments, it is divided as far anteriorly as is possible to gain sufficient length. The free hypoglossal nerve is rotated superiorly. Directing the nerve medial to the digastric muscle in this rotation gives the most length, but is unnecessary for a satisfactory anastomosis.

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FIGURE 62-2 Parotid gland is mobilized anteriorly and superiorly as sternocleidomastoid muscle is retracted posteriorly, exposing facial and hypoglossal nerves.

FIGURE 62-3. Proximal end of hypoglossal nerve is anastomosed to distal end of facial nerve. Care is taken to use maximal length of each nerve to achieve tension-free anastomosis.

There are many ways to anastomose the ends of the nerves, including collagen trays and fibrin glue, vein sheaths, laser welding, and various suture techniques. It is beyond the scope of this chapter to describe the various methods; however, several principles are almost universally agreed on. The two ends of the nerves should be free of all tension. This requirement is usually not a problem if the technique described earlier is followed. The ends should be cut sharply to provide a flush connection. The anastomosis should be as atraumatic as possible, yet provide strength to prevent disruption. It is also important to ensure, using frozen section histologic evaluation, that the distal facial nerve has not totally fibrosed in cases of long-standing paralysis. A conventional suture technique that yields reliable results is as follows:

1. By use of the operating microscope, the distal end of the facial nerve and proximal end of the hypoglossal nerves are stripped of the epineurium 2 to 3 mm from the cut ends.
2. The ends are freshened with a sharp, clean, perpendicular cut to provide a good flush connection.
3. The perineurium is approximated with two or three 9-0 nylon sutures (Fig. 62-3).
4. The wound is closed in layers over a Penrose drain.
5. A fluffed, snug parotidectomy dressing is applied, and the drain is removed the next day. Perioperative antibiotics are unnecessary.

NERVE GROWTH FACTORS AND CONDUITS

Nerve grafts are the traditional technique to bridge the gap between two ends of nerve to be anastomosed. Because nerve repairs need to be tension-free, grafts are required if the ends of the nerve cannot be freely coapted. If a way could be developed to bridge this gap without using a nerve graft, that would be a potential improvement. Artificial conduits are one potential replacement for nerve grafts.17,18 Collagen tubules have been used to provide a pathway for axonal growth to occur. Other substances that have been used to create conduits include hydrogels19 and collagen-filled vein grafts.20

Nerve ends to be repaired are placed inside these conduits and either directly coapted in the conduit or placed at some distance from one another. One manufacturer (Integra, Plainsboro, NJ) recommends that if the nerve ends are not directly in contact, saline should be instilled to fill the tubule. The nerve ends may be attached to the tubule by one epineurial suture.

Several different nerve growth factors have been used to augment nerve graft repair and in collagen tubules. Brain-derived neurotrophic factor is an agent that has shown promise when used in collagen tubules or when applied directly to nerve repairs.21,22 Other agents that have been employed include neurotrophin-3 and fibroblast growth factor 1.23 Ciliary neurotrophic factor, a neurocytokine, has also been used in nerve repairs and may increase the rate of recovery over brain-derived neurotrophic factor alone.24

NEWER MODIFICATIONS OF HYPOGLOSSAL-FACIAL ANASTOMOSIS

One modification of the standard CN XII/VII crossover graft uses a jump graft between the CN XII and VII. This procedure, as described by May and others,25,26 succeeds in preserving tongue function and reinnervating the facial muscles. The exposure of CN XII and VII is identical to that described earlier (see Fig. 62-2). A 5 cm length of great auricular nerve is harvested. CN XII is cut through on half of its diameter in a beveled manner. The incision should be made in a portion of the nerve distal to the divergence of the ansa cervicalis to avoid tapping the fibers that constitute this nerve (Fig. 62-4, inset). Stimulation of CN XII with a nerve stimulator proximal to the partial transection should confirm preservation of tongue function.

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FIGURE 62-4 In CN XII/VII jump graft, greater auricular or sural nerve graft is harvested. Facial nerve is cut at stylomastoid foramen. Hypoglossal nerve is cut across half its diameter using Keith needle and scalpel blade (see inset). Tension-free anastomoses are created between jump graft, facial nerve, and hypoglossal nerve.

The great auricular graft and the distal segment of the facial nerve are prepared for anastomosis in the manner described for the standard CN XII/VII crossover. The graft is sutured to the proximal segment of the partially severed CN XII. The other end of the graft is sutured to the prepared distal end of the facial nerve (see Fig. 62-4). Two or three sutures are used for this connection. Enough length of graft must be used to avoid tension at the sites of anastomosis. The wound is closed as in the standard procedure. The patient is usually kept in the hospital overnight and discharged the following morning after removal of the drain. Although the patient may have some trouble with pooling of food in the ipsilateral oral vestibule, no special diet is necessary.

Pitfalls to avoid in this surgery include use of the ansa cervicalis branch of CN XII instead of CN XII itself. This particular method leads to a much weaker result. The surgeon should also ensure that the distal facial nerve is not fibrosed, and that the facial muscles are still viable.

In another variation of the jump graft hypoglossal/facial anastomosis, a collagen tubule may be used as an adjunct to the anastomosis between the facial nerve and the jump graft (Fig. 62-5). Collagen tubules, described previously, may be used to facilitate direct coaptation of the nerve ends, or saline may be placed in the tubule between the nerve ends. A single epineurial suture is used to connect the nerve graft to the collagen tubule (see Fig. 62-5, inset).

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FIGURE 62-5 Collagen tubules may be used as adjunct to coaptation of jump graft and facial nerve or hypoglossal nerve. With collagen tubules, one simple epineurial suture is used between nerve and tubule. Tubule may be filled with saline, or ends of nerve may be directly coapted inside tubule.

End-to-Side Anastomosis via Translocation of Facial Nerve from the Fallopian Canal

A more recent technique consists of rerouting the facial nerve from the fallopian canal and connecting it directly to the hypoglossal nerve through an end-to-side anastomosis.27 In this technique, the facial nerve is decompressed from the stylomastoid foramen inferiorly to the geniculate ganglion superiorly. The greater superficial petrosal nerve is transected at the geniculate ganglion, and the facial nerve is mobilized inferiorly. The nerve itself is traced through the periosteum of the stylomastoid foramen until the pes anserinus is reached (Fig. 62-6). When the pes is reached, the nerve is of sufficient length for the proximal end of the nerve to be anastomosed to a partial (“end-to-side”) transection of the hypoglossal nerve, either through a direct anastomosis or with a collagen tubule (see Fig. 62-6).

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FIGURE 62-6 Translocation of intratemporal facial nerve with direct anastomosis between facial nerve and split end of hypoglossal nerve (end-to-side anastomosis). Collagen tubules (not shown) may also be used to facilitate anastomosis.

This technique usually provides enough length to avoid the use of a jump graft. The primary advantage of this technique is a single facial/hypoglossal anastomosis with the ability to use a partial hypoglossal donor nerve. In this manner, an efficient anastomosis may be achieved with minimal tongue weakness.

RESULTS

A patient with facial paralysis who is considered a candidate for CN XII/VII crossover should be counseled about the expected results from this procedure. The patient cannot expect normal facial function for several reasons.3,4,28–32 As in a direct nerve repair, the axons directed to specific muscles find a random path. The muscles of the face include agonists and antagonists for various expressions and movements. When agonist and antagonist muscles are simultaneously stimulated, the result is a canceling effect. This effect is similar to that occurring during stimulation of a flexor and extensor muscle at the same time. The hypoglossal nerve controls different muscle groups, allowing training of facial movement as the patient attempts various tongue motions. The training is successful, but is not helpful in emotional facial response. This procedure does not reproduce the blink reflex, even though some investigators have shown a trigeminal-hypoglossal reflex.28 Problems with xerophthalmia and exposure keratitis may require adjunctive lid procedures, such as a palpebral spring or gold weight lid implant.

Within 4 to 6 months, the patient begins to see tone in the muscles and a resting symmetry.3,4,13,32 With a rehabilitation program, volitional movement is possible, allowing the patient to smile with tongue movement. Electromyographic feedback–enhanced rehabilitation has shown some additional benefits.1,13,33 Because many facial movements are also coordinated with oral function, the CN XII/VII anastomosis improves the patient’s ability to eat by providing tension to the buccal area and keeping the bolus in the oral vestibule. The natural interaction between the facial and hypoglossal nerves in eating, swallowing, and speaking facilitates the rehabilitation seen with this crossover graft as opposed to the accessory or phrenic nerve.

Because of the nonselective nature of reinnervation, movement of the face results in synkinesis and mass movement that varies from patient to patient. Synkinesis can be reduced by exercise and biofeedback early in recovery.33 Selective section of branches of the facial nerve is also useful in severe cases, as is the use of selective botulinum toxin injections.34

Because the function gained by reinnervation procedures cannot compare with normal facial function, a different method of grading facial function is used in evaluation of the results of the CN XII/VII crossover. A grading system used in a prior analysis of CN XII/VII crossover patients in our facility is presented in Table 62-1. Although the methods used to evaluate results vary from study to study, we have extrapolated the grading system in Table 62-1 to provide the results from several sizable studies (Table 62-2). This analysis should give the reader a good idea of reasonable expectations from this procedure.

TABLE 62-1 Facial Nerve Function after Cranial Nerve XII-VII Anastomosis: Quality of Return Criteria before House-Brackmann Grading Scale

Poor Tone without symmetry or movement
Fair Tone, symmetry, limited movement
Good Tone, symmetry, fair movement, moderate synkinesis
Excellent Tone, symmetry, good movement, mild synkinesis

From Luxford WM, Brackmann DE: Facial nerve substitution: A review of sixty-six cases. Am J Otol Suppl 55-57, 1985.

TABLE 62-2 Results of Cranial Nerve XII-VII Anastomosis from Selected Studies

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More recent studies, particularly studies reporting on results for jump interposition grafts or translocation of the facial nerve with end-to-side anastomosis, use the House-Brackmann grading scale for result reporting.35 Table 62-3 shows results from more recent studies using either jump grafting or end-to-side anastomosis. The patients in these studies were divided between early intervention (<12 months) and late intervention (>12 months, but generally <24 months), and had similar outcomes. Generally, the best result to be expected on the House-Brackmann grading scale with any nerve grafting procedure is a grade III result. This result requires movement of the forehead. Almost all patients have significant synkinesis after hypoglossal/facial anastomosis, rendering grade III the best result to be expected.

TABLE 62-3 Results of More Recent Studies on Variations of Hypoglossal-Facial Anastomosis

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The deficit incurred in the sacrifice of one hypoglossal nerve is easily overcome by most patients.4,13,32 Initially, some pooling of food in the lingual sulcus is problematic. As the buccal musculature regains tone, and as the ipsilateral tongue atrophies, this problem lessens. In Conley and Baker’s large series,4 about one fourth of the patients experienced severe or minimal atrophy, and the remaining half experienced moderate atrophy. Very few patients had trouble with speech. The best results in regaining facial function and overcoming the CN XII deficit were seen with early anastomosis compared with procedures performed on patients with long-standing paralysis.4

More recent reports indicate that the choice of technique does not cause a difference in facial functional outcomes.36 Methods that preserve tongue function may become preferable to the standard hypoglossal/facial anastomosis.

SUMMARY

The CN XII/VII crossover graft is a easy, reliable procedure in the rehabilitation of facial paralysis. A thorough preoperative evaluation is required, as is proper timing. The patient can expect return of tone and symmetry and synkinesis and mass movement. The donor deficit is not significant when measured against the benefits gained from the procedure, particularly when partial hypoglossal nerve transection and jump graft or end-to-side anastomosis is performed. Patients who are given realistic expectations are pleased with the improvement seen from this procedure.

REFERENCES

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3. Chuang D.C., Wei F.C., Noordhoff M.S. “Smile” reconstruction in facial paralysis. Ann Plast Surg. 1989;23:56-65.

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5. Yamamoto Y., Sasaki S., Sekido M., et al. Alternative approach using the combined technique of nerve crossover and cross-nerve grafting for reanimation of facial palsy. Microsurgery. 2003;23:251-256.

6. Ueda K., Akiyoshi K., Suzuki Y., et al. Combination of hypoglossal-facial nerve jump graft by end-to-side neurorrhaphy and cross-face nerve graft for the treatment of facial paralysis. J Reconstr Microsurg. 2007;23:181-187.

7. Hadlock T., Sheahan T., Heaton J., et al. Baiting the cross-face nerve graft with temporary hypoglossal hookup. Arch Facial Plast Surg. 2004;6:228-233.

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9. Tucker H.M. Restoration of selective facial nerve function by the nerve-muscle pedicle technique. Clin Plast Surg. 1979;6:293-300.

10. Harrison D.H. The treatment of unilateral and bilateral facial palsy using free muscle transfers. Clin Plast Surg. 2002;29:539-549.

11. Byrne P.J., Kim M., Boahene K., et al. Temporalis tendon transfer as part of a comprehensive approach to facial reanimation. Arch Facial Plast Surg. 2007;9:234-241.

12. Belal A. Structure of human muscle in facial paralysis: Role of muscle biopsy. In: May M., editor. The Facial Nerve. New York: Thieme; 1986:99-106.

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14. Ylikoski J., Hitselberger W.E., House W.F., et al. Degenerative changes in the distal stump of the severed human facial nerve. Acta Otolaryngol. 1981;92(3-4):239-248.

15. Kunihiro T., Kanzaki J., Yoshihara S., et al. Hypoglossal-facial nerve anastomosis after acoustic neuroma resection: Influence of the time anastomosis on recovery of facial movement. ORL J Otorhinolaryngol Relat Spec. 1996;58:32-35.

16. Hitselberger W.E.. Hypoglossal-facial anastomosis. House W.F., Luetje C.M., editors. Acoustic Tumors. vol 2, 1979. University Park Press, Baltimore, 97-103. Management

17. Archibald S.J., Shefner J., Krarup C., et al. Monkey median nerve repaired by nerve graft or collagen nerve guide tube. J Neurosci. 1995;15(5 Pt 2):4109-4123.

18. Archibald S.J., Krarup C., Shefner J., et al. A collagen-based nerve guide conduit for peripheral nerve repair: An electrophysiological study of nerve regeneration in rodents and nonhuman primates. J Comp Neurol. 1991;306:685-696.

19. Belkas J.S., Munro C.A., Shoichet M.S., et al. Peripheral nerve regeneration through a synthetic hydrogel nerve tube. Restor Neurol Neurosci. 2005;23:19-29.

20. Lee D.Y., Choi B.H., Park J.H., et al. Nerve regeneration with the use of a poly(l-lactide-co-glycolic acid)-coated collagen tube filled with collagen gel. J Craniomaxillofac Surg. 2006;34:50-56.

21. Lewin S.L., Utley D.S., Cheng E.T., et al. Simultaneous treatment with BDNF and CNTF after peripheral nerve transection and repair enhances rate of functional recovery compared with BDNF treatment alone. Laryngoscope. 1997;107:992-999.

22. Barde Y.A., Edgar D., Thoenen H. Purification of a new neurotrophic factor from mammalian brain. EMBO J. 1982;1:549-553.

23. Midha R., Munro C.A., Dalton P.D., et al. Growth factor enhancement of peripheral nerve regeneration through a novel synthetic hydrogel tube. J Neurosurg. 2003;99:555-565.

24. Lewin S.L., Utley D.S., Cheng E.T., et al. Simultaneous treatment with BDNF and CNTF after peripheral nerve transection and repair enhances rate of functional recovery compared with BDNF treatment alone. Laryngoscope. 1997;107:992-999.

25. May M., Sobol S.M., Mester S.J. Hypoglossal-facial nerve interpositional-jump graft for facial reanimation without tongue atrophy. Otolaryngol Head Neck Surg. 1991;104:818-825.

26. Hammerschlag P.E. Facial reanimation with jump interpositional graft hypoglossal facial anastomosis and hypoglossal facial anastomosis: Evolution in management of facial paralysis. Laryngoscope. 1999;109(2 Pt 2 Suppl 90):1-23.

27. Atlas M.D., Lowinger D.S. A new technique for hypoglossal-facial nerve repair. Laryngoscope. 1997;107:984-991.

28. Stennert E. I. Hypoglossal facial anastomosis: Its significance for modern facial surgery. II. Combined approach in extratemporal facial nerve reconstruction. Clin Plast Surg. 1979;6:471-486.

29. Pensak M.L., Jackson C.G., Glasscock M.E.III, et al. Facial reanimation with the VII-XII anastomosis: Analysis of the functional and psychologic results. Otolaryngol Head Neck Surg. 1986;94:305-310.

30. Sabin H.I., Bordi L.T., Symon L., et al. Facio-hypoglossal anastomosis for the treatment of facial palsy after acoustic neuroma resection. Br J Neurosurg. 1990;4:313-317.

31. Chang C.G., Shen A.L. Hypoglossofacial anastomosis for facial palsy after resection of acoustic neuroma. Surg Neurol. 1984;21:282-286.

32. Luxford W.M., Brackmann D.E. Facial nerve substitution: A review of sixty-six cases. Am J Otol Suppl. 1985:55-57.

33. Hammerschlag P.E., Brudny J., Cusumano R., et al. Hypoglossal-facial nerve anastomosis and electromyographic feedback rehabilitation. Laryngoscope. 1987;97:705-709.

34. Dressler D., Schonle P.W. Botulinum toxin to suppress hyperkinesias after hypoglossal-facial nerve anastomosis. Eur Arch Otorhinolaryngol. 1990;247:391-392.

35. House J.W., Brackmann D.E. Facial nerve grading system. Otolaryngol Head Neck Surg. 1985;93:146-147.

36. Guntinas-Lichius O., Streppel M., Stennert E. Postoperative functional evaluation of different reanimation techniques for facial nerve repair. Am J Surg. 2006;191:61-67.

37. Gavron J.P., Clemis J.D. Hypoglossal-facial nerve anastomosis: A review of forty cases caused by facial nerve injuries in the posterior fossa. Laryngoscope. 1984;94(11 Pt 1):1447-1450.

38. Sawamura Y., Abe H. Hypoglossal-facial nerve side-to-end anastomosis for preservation of hypoglossal function: Results of delayed treatment with a new technique. J Neurosurg. 1997;86:203-206.

39. Darrouzet V., Guerin J., Bebear J.P. New technique of side-to-end hypoglossal-facial nerve attachment with translocation of the infratemporal facial nerve. J Neurosurg. 1999;90:27-34.

40. Rebol J., Milojkovic V., Didanovic V. Side-to-end hypoglossal-facial anastomosis via transposition of the intratemporal facial nerve. Acta Neurochir (Wien). 2006;148:653-657.

41. Godefroy W.P., Malessy M.J., Tromp A.A., et al. Intratemporal facial nerve transfer with direct coaptation to the hypoglossal nerve. Otol Neurotol. 2007;28:546-550.

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