Donor Nerve Selection in Facial Reanimation Surgery

Donor Nerve Selection in FacialReanimation SurgeryMichael Klebuc, M.D.1 and Saleh M. Shenaq, M.D.1

ABSTRACT

The motor components of local cranial nerves provide a series of options for thesurgical rehabilitation of the paralyzed face. Nerve donor sites vary with respect to theirmotor power, functional deficit, and synergy with facial expression. A thorough under-standing of each donor nerve’s strengths and weaknesses facilitates the selection process.Technical modifications to reduce donor site morbidity and the emerging role of themasseter nerve are examined.

KEYWORDS: Facial nerve paralysis, trigeminal motor nerve, cross-face nerve graft,

hypoglossal nerve transfer, facial reanimation

Local cranial nerves in the patient with facialparalysis represent a source of motor axons that can beredirected for facial reanimation. Each nerve donor sitepossesses a series of advantages and disadvantages man-dating careful planning and selection. Considerationshould be given to the functional defect produced bysectioning the donor nerve and the degree of motorpower (muscle excursion) that can be anticipated. Thepotential for motor reeducation or true mimetic func-tion, incidence of mass motion, recovery time, technicaldifficulty, and need for nerve grafting require appraisal.The disease state and the prospect for development ofadditional cranial nerve deficits (i.e., neurofibromatosistype II) should also be considered. The presence ofcoexistent cranial nerve lesions also influences donornerve selection. The cumulative effect of the functionallosses must be carefully analyzed to prevent debilitatingproblems. A clear example is the frequent developmentof profound swallowing dysfunction when hypoglossal-to-facial nerve transfers are utilized in patients withtenth-nerve deficits.

Cranial nerve motor branches are sacrificed torehabilitate the paralyzed face in three principal fashions:

1. Adjacent cranial nerve transfers to VII2. Cross-face nerve grafts with VII to contralateral VII

or a free muscle flap3. Adjacent cranial nerve to power a free muscle flap

Adjacent cranial nerve transfers can provide aneffective strategy for reanimating the paralyzed face.These techniques are characteristically employed whena proximal facial nerve segment is unavailable to beutilized in the reconstruction. In addition, requirementsinclude the presence of distal facial nerve branches andmimetic musculature that have not been damaged bytrauma or irreversible degeneration.

Nerve transfer techniques are often selected as themethod of choice for facial nerve reconstruction follow-ing ablative tumor surgery or trauma involving the brainstem and skull base. If the distal nerve segments andfacial muscles have been resected or traumatized ordeveloped irreversible atrophy, the nerve can be utilizedto power a free muscle flap.

Traditional donor nerves for transfer to cranialnerve (CN) VII include the hypoglossal nerve (CN XII),facial nerve (CN VII) with cross-face graft, and spinal

Facial Paralysis; Editor in Chief, Saleh M. Shenaq, M.D.; Guest Editor, Susan E. Mackinnon, M.D. Seminars in Plastic Surgery, Volume 18,Number 1, 2004. Address for correspondence and reprint requests: Michael Klebuc, M.D., Division of Plastic Surgery, Baylor College of Medicine,6560 Fannin, #800, Houston, TX 77030. 1Division of Plastic Surgery, Baylor College of Medicine, Houston. TX. Copyright 2004 byThieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001 USA. Tel: +1(212) 584-4662. 1535-2188,p;2004,18,01,053,060,ftx,en;sps00109x.

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accessory nerve (CN XI). Selected branches of thehypoglossal nerve can be utilized (descendens hypo-glossi) or a jump graft technique after sectioning ap-proximately one third of the nerve. Less frequentlyutilized transfers include the spinal accessory (XI) andphrenic nerves. In our practice, the motor branch to themasseter muscle (CN V) is emerging as the cranial nervetransfer of choice.

Selecting a cranial nerve for transfer requirescareful consideration regarding a series of variables:

Functional deficit produced by sacrificing the donornerve (i.e., speech, swallowing)

Need for interposition nerve grafts (i.e., sural/greaterauricular nerve)

Synergism between the donor nerve and facial nerve andits influence on motor reeducation

Nerve topography (diameter, axon count, fiber type) andthe donor nerve’s ability to provide adequate powerwithout inducing mass movement

Further analysis of specific motor nerve donorsites and the rationale for selection are provided in thefollowing sections.

Trigeminal Motor Nerve (Masseteric Nerve)

In our Restoration Center the motor branch of thetrigeminal nerve to the masseter muscle has graduallyevolved into the nerve of choice for reinnervating paral-yzed mimetic muscles in the midface and powering freemuscle flaps. The motor nerve branch to the masseterhas a series of advantages compared with more tradi-tional options such as the hypoglossal nerve.

The masseter and temporalis muscles work inconcert during mastication. The donor deficit producedby harvesting the motor nerve branch of the massetermuscle is therefore significantly lessened by this duplica-tion of function. This stands in direct contrast to theclassical complete XII–VII nerve transfer, with whichsignificant postoperative difficulties with eating andimpaired speech can develop in 21 to 45% of patients.1,2

In addition, utilization of the motor branch of thetrigeminal nerve has not resulted in complete paralysis ofthe masseter muscle or atrophy producing a visiblecosmetic deformity. Temporal mandibular joint dys-function has also not been identified on long-termfollow-up. The limited donor site morbidity probablyresults from the nerve’s branching pattern. The nervearises beneath to the zygomatic arch and charts anoblique course along the deep surface of the musclerunning from the posterior superior to anterior inferiorborder (Fig. 1). Operative exploration of the nerve hasidentified a series of smaller proximal branches asso-ciated with a more dominant descending branch. Divid-ing the descending branch distally and transposing the

nerve into a more superficial location facilitate micro-surgical anastomosis while preserving proximal in-nervation. Adequate length to permit a tension-freemicrosurgical nerve coaptation without utilizing a nervegraft has been universal in our experience.

Our preliminary experience with this techniqueencompasses 10 nerves in eight patients. The motorbranch of the trigeminal nerve was utilized to reinnervatemimetic musculature in four individuals and power freegracilis muscle flaps in an additional four patients(Fig. 2).3

Several interesting findings have surfaced fromthis initial experience. All patients developed strongcontraction of the selected muscles of facial expressionand free muscle flaps. This clinical finding has also beenduplicated in an animal model. Frydman et al havecompared standard XII–VII to V–VII transfers in rab-bits.4 Histologic and electromyographic evaluation de-monstrated similar mean muscle fiber diameters andatrophy scores, suggesting that both techniques canprovide adequate axonal input for facial reanimation.

In the principal author’s experience, the motorbranch to the masseter was initially utilized to innervatefree muscle flaps in patients with Mobius syndrome.This has resulted in significantly better muscle excursionthan that in our non-Mobius patients in whom cross-face grafts have been employed. These findings have alsobeen observed by Bae et al.5 They compared the extent oforal commissure movement in 120 children who under-went free gracilis muscle flaps for facial reanimationpowered by either a cross-face nerve graft or the masseternerve. Muscle excursion in the cross-face nerve graftgroup was significantly less than that in both the pa-tient’s contralateral (normal) side and that achieved withthe masseter nerve transfers (Fig. 3).

A significant shortcoming of nerve transfers hasbeen the development of unwanted mass facial motion.

Figure 1 Trigeminal motor nerve on deep surface of masseter.Proximal branches and single descending branch.

54 SEMINARS IN PLASTIC SURGERY/VOLUME 18, NUMBER 1 2004

Facial spasm is frequently produced by mastication (XII–VII transfers), shoulder movement (XI–VII transfers),and inspiration with phrenic nerve transfers. In addition,an extensive period of motor reeducation is often neededto achieve a proficient smile and there is question aboutwhether this can ever be truly spontaneous in nature.Several large trials reported good to excellent results in22 to 65% of patients with XII–VII transfers; however,Baker cautioned that a behavioral response closely simu-lating normal smiling develops in only 10% of highlymotivated patients.6,7

In our early experience with the fifth cranial nerve,active motion of the facial musculature or free flap hasdeveloped an average of 6 months after surgery.

Rapid motor reeducation has also been appre-ciated. Patients have quickly learned to smile withoutteeth clenching, despite a lack of formal physical therapy,especially in the pediatric age group. Efficient cerebraladaptation with fifth-nerve transfers has also been de-scribed by Manktelow et al.8 They reviewed their ex-

perience with 41 functional-free-muscle flaps innervatedby the masseter nerve. In this series, 82% of patientsdeveloped the ability to smile without biting and 53%could produce a smile without conscious effort.

The motor division of the trigeminal nerve ap-pears to hold some advantage over other nerve donorsites with respect to reeducation and production of aneffortless smile. Rubin et al, when reviewing a 30-yearexperience utilizing partial transfers of the temporalisand masseter muscles for facial reanimation, noted that66% of patients could smile without clenching theirteeth and an additional 30% required only minimalvolitional input.9 In consultation with several preemi-nent neurophysiologists, they postulated that following afacial nerve injury the neuroplastic potential of the brainfacilitates development of new neurocranial pathwaysbetween the fifth and seventh nerves. This theory isfurther supported by the close proximity of the facial andtrigeminal nuclei within the pons. Scattered reports alsoexist describing spontaneous redevelopment of facial

Figure 2 (A) Left facial nerve paralysis 8 months after skull base fracture. (B) Preoperative markings for masseter nerve transfer andcross-face graft. (C) Masseter-buccal branch anastomosis and cross-face graft to zygomatic branch. (D) Facial motion, fifth post-operative month.

DONOR NERVE SELECTION/KLEBUC, SHENAQ 55

motion after surgical sacrifice of the facial nerve duringtotal parotidectomy.10 Electroneurographic evidencesuggests that the damaged facial nerve undergoes ipsi-lateral neurotization via the trigeminal nerve. This con-cept is the basis of the Lexer-Rosenthal procedure, inwhich the raw surface of the masseter muscle is broughtinto contact with facial musculature to facilitate in-growth from the terminal branches of the trigeminalnerve.11 Alternative explanations for spontaneous recov-ery include the presence of aberrant pathways betweenthe fifth and seventh nerves. Embryologic evidence isavailable demonstrating the presence of trigeminal nervefibers within facial nerve branches.12,13 Developmentalmodels have also identified facial nerve fibers coursingwithin the motor pathway of the trigeminal nerve thateventually rejoin branches of the facial nerve via V–VIIcommunicating rami.14

The specifics of the anatomic relationship be-tween the fifth and seventh cranial nerves require furtherclarification. However, it is highly probable that the‘‘connectedness’’ of these structures in conjunction withcentral neuroplasticity contributes to the rapid, uncom-plicated adaptation present clinically when the masseternerve is utilized for facial reanimation.

Hypoglossal Nerve

The complete XII–VII crossover represented the ‘‘goldstandard’’ nerve transfer for many years but is associatedwith significant donor site morbidity. Complicationswith tongue atrophy (27%), difficulty eating (45%), andimpaired speech (27%) are frequent.2 Synkinesis is pre-valent, and up to 80% of patients develop problems withmass motion.15 Despite excessive motion in the midface,the transfer often provides inadequate protection of theeye. In addition, the complete XII–VII transfer is con-traindicated in individuals with neurofibromatosis (typeII) and adenoid cystic carcinoma who are susceptible tothe development of multiple cranial nerve deficits.Hypoglossal nerve transfers combined with a tenthcranial nerve deficit can result in profound swallowingdysfunction.

The functional deficit produced by complete XII–VII transfer can be significantly reduced by utilizing ajump graft technique. A neurotomy is created dividing25 to 30% of the hypoglossal nerve’s diameter (Fig. 4).16

An interposition graft is then sutured in an end-to-sidefashion to nerve XII, followed by an end-to-end repair tonerve VII. On average, a 5-cm length of graft is requiredand can be obtained from the great auricular, medial

Figure 3 (A) Mobius syndrome patient. Free gracilis muscle flapwith obturator-to-masseter nerve anastomosis. (B) Face at restafter free gracilis muscle flap to left side (sixth postoperativemonth). (C) Facial motion after free gracilis muscle flap to leftside (sixth postoperative month).


antebrachial cutaneous, and sural nerves. Utilizing a‘‘partial’’ hypoglossal-to-facial nerve transfer, a signifi-cant reduction in donor site morbidity has been realized.May and associates reported their experience with 69hypoglossal jump grafts performed on 66 patients.2 Theoutcomes were compared with those of their patientswho had previously received complete XII transfers. Apermanent tongue deficit developed in 8% of the jumpgraft group and in 100% of patients who had received acomplete transfer. Difficulty swallowing was associatedwith 3% of the jump grafts and 45% of the traditionaltransfers. Impaired speech developed in 1% and 27% ofthe jump graft and complete transfer patients, respec-tively. Recovery was slower and the degree of musclecontraction was less in the jump graft group. The pa-tients who received partial hypoglossal transfers seldomdeveloped the mass motion and synkinesis that fre-quently complicated the complete XII transfers. Thebest results with this technique were obtained when thesurgery was performed within the first 3 months of facialnerve injury.2

In addition, Atlas and Lowinger have reportedperforming a direct end-to-side repair of extensivelymobilized facial nerves to the partially incised hypoglos-sal nerve.17

Contralateral Facial Nerve with

Cross-Face Graft

The principal benefit of utilizing the contralateral facialnerve for reanimation is its ability to provide a sponta-neous smile. Although true mimetic function can beachieved, the muscular contraction produced is often

significantly weaker than that on the normal side. This isnot unexpected as a limited number of functioning facialnerve branches are sacrificed for the transfer. The re-generating axons must cross two suture lines and traversea sural nerve graft up to 24 cm in length. A significantsize mismatch between the facial nerve branches andnerve graft also exists. A period of 9 to 12 months isrequired for the axons to migrate through the graft. Thistime lag subjects the paralyzed facial muscles to furtheratrophy and fibrosis. Clearly, time is not on one’s sidewhen utilizing this technique, and it is best suited forcases of facial paralysis less than 6 months in duration orto motor free muscle flaps (Fig. 5). Our best results havebeen achieved when immediate cross-face nerve graftswere placed at the time of tumor excision, when theproximal segment of the facial nerve was resected.

The final result can be maximized by utilizingmeticulous microsurgical technique and a single-stageapproach. Myelin thickness, fiber diameter and neuraltissue density are all enhanced by immediately perform-ing the distal neurorrhaphy.18 Partial hypoglossal trans-fers to selected buccal and zygomatic branches can beutilized as a ‘‘baby-sitting’’ procedure to maintainthe neuromuscular junctions of the denervated musclewhile axonal regeneration proceeds in the cross-facegraft.19 The baby-sitter procedure is performed in con-junction with the cross-face graft and is usually left intactto augment the final function.

The use of cross-face grafts in our practice hasslowly changed from an exclusive freestanding techniqueto a more adjunctive role. Cross-face grafts have proveduseful in augmenting specific facial nerve branches inindividuals with incomplete paralysis. In these cases,

Figure 4 Partial XII–VII transfer with jump graft technique.

Figure 5 Cross-face nerve graft to power free gracilis muscleflap.


symmetry is enhanced by both strengthening the pareticside and weakening the overactive normal side. May andcolleagues also reported a positive experience utilizingcross-face nerve grafts for treating incomplete facialparalysis. The majority of good results with cross-facenerve grafts in their series were obtained when thetechnique was employed for augmentation.2

A combined approach is often utilized for indivi-duals with complete hemifacial paralysis of less than1 year duration. The cross-face graft is utilized toreinnervate the orbicularis oculi, and the eye is protectedby a gold eyelid weight during the period of regenera-tion. The masseter nerve is transferred to selected buccalbranches to reanimate the corner of the mouth, and themarginal mandibular branch is reconstructed with trans-fer of the descendens hypoglossi or selective myectomy ata later time. The brow is usually addressed with standardaesthetic surgery techniques.

The contralateral facial nerve via a cross-face grafthas traditionally been utilized to power free muscle flapsfor reanimating the corner of the mouth. This is usuallyperformed as a two-stage procedure and often results inmuscle flap contraction that is spontaneous but weakerthan that on the normal side.5

The motor branch to the masseter muscle, aspreviously mentioned, is emerging as a significant alter-native to cross-face grafts for innervating free muscleflaps. The masseter nerve produces stronger muscle con-traction while allowing the reconstruction to be per-formed in a single stage. The smile may not be trulyspontaneous, but the muscle is activated without bitingin more than 80% of patients. More than 50% ofindividuals require no conscious effort to produce arecognizable smile.8

Spinal Accessory Nerve (Cranial Nerve XI)

The spinal accessory nerve is not considered a first-linedonor site for facial reanimation. Complete sectioning ofthe nerve can produce significant shoulder weakness andthe transfer lacks the ‘‘physiologic dynamism’’ providedby other cranial nerves (i.e., XII, V).20 Shoulder move-ment generated by normal activities can induce trouble-some mass contraction of the facial musculature. Someindividuals develop the ability to dissociate faceand shoulder motion, but a voluntary effort is usuallyrequired.

The spinal accessory transfer appears best suitedfor situations in which the motor branch to masseterand hypoglossal nerves are absent or preexisting speechand swallowing problems are present.

The donor site morbidity can be reduced byselective utilization of the branch to the sternocleido-mastoid (SCM) muscle.21 Thulin reported his experi-ence with SCM branch transfers in 15 patients.22 Goodmotion developed in more than half of the subjects

and no patient experienced debilitating atrophy of thetrapezius muscle.

Phrenic Nerve

The phenic nerve is largely mentioned for completenessbut has been utilized in rare situations when more ac-ceptable donor nerves were unavailable. Perret describedhis experience with 23 cases.23 Good resting facial tonewas achieved, but asymmetry and marked contractiondeveloped with coughing, laughing, and deep inspira-tion. The transfer produces hemidiaphragmatic paraly-sis; however, chest radiographs and pulmonary functiontests tend to improve with time.24 This transfer is clearlycontraindicated in individuals with pulmonary disease orchest wall abnormalities.

In conclusion, it can be said that local cranialnerves provide a series of reconstructive options forreanimating the paralyzed face. Understanding thestrengths and weaknesses of each donor nerve and theirvariability with respect to motor power, functional loss,and ability to produce a natural smile is an essential partof the selection process.

ACKNOWLEDGMENT

I would like to recognize Dr. Melvin Spira’s pioneeringwork in the early 1970s with masseter nerve transfers andthank him for his kindness, support, and infectiousenthusiasm.

REFERENCES

1. Pensak ML, Jackson GG, Glasscock ME, et al. Facialreanimation with the XII–VII anastomosis: analysis of thefunction and psychological results. Otolaryngol Head NeckSurg 1986;94:305–310

2. May M. Nerve substitution techniques: XII–VII hook-up,XII–VII jump graft and cross-face graft. In: May M, ed. TheFacial Nerve. May’s 2nd ed. New York: Thieme MedicalPublishers; 2000:611–633

3. Spira M. Anastomosis of masseteric nerve to lower division offacial nerve for correction of lower facial paralysis. PlastReconstr Surg 1978;61:330–334

4. Frydman W, Heffez L, Jordan S, et al. Facial muscle re-animation using the trigeminal motor nerve: an experimentalstudy in the rabbit. J Oral Maxillofac Surg 1990;48:1294–1304

5. Bae YC, Zuker R, Manktelow R, et al. Comparative study ofresults after gracilis muscle transplant for facial animation inchildren according to innervated motor nerve: cross-facialnerve graft vs. the masseteric nerve. Paper presented at theAnnual Meeting of the American Society for ReconstructiveMicrosurgery; January 11, 2003; Kauai, Hawaii

6. Luxford W, Brackmann DE. Facial nerve substitution: areview of sixty-six cases. Am J Otolaryngol 1985;Suppl:55–57

7. Baker D. Hypoglossal facial nerve anastomosis indicationsand limitations. In: Portmann MD, ed. Proceedings of the


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8. Manktelow R, Tomat L, Chang M, et al. Does cerebraladaptation occur when the Vth nerve is used for facialparalysis reconstruction in adults? Paper presented at theAmerican Association of Plastic Surgeons 81st AnnualMeeting; April 29, 2002; Seattle, Washington

9. Rubin L, Rubin P, Simpson R, et al. The search for theneurocranial pathways to the fifth nerve nucleus in the re-animation of the paralyzed face. Plast Reconstr Surg 1999;103:1725–1728

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11. Adour K, Klein J, Bell D. Trigeminal neurotization ofparalyzed facial musculature. Arch Otolaryngol 1979;105:13–16

12. Bowden R, Mahram Z. Experimental and histological studiesof the extra petrous portion of the facial nerve and its com-munications with the trigeminal nerve in the rabbit. J Anat1960;94:375–386

13. Gasser RF. The development of the facial nerve in man. AnnOtol Rhinol Laryngol 1967;76:37–56

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18. Mackinnon SE, Dellon AL, Hunter DA. Histologicalassessment of the effects of the distal nerve in determiningregeneration across a nerve graft. Microsurgery 1988;9:46–51

19. Endo T, Hata J, Nakayama Y. Variations on the ‘‘baby-sitter’’procedure for reconstruction of facial paralysis. J ReconstrMicrosurg 2000;16:37–43

20. Baker DC. Facial paralysis. In: McCarthy J, ed. Plastic Sur-gery. Vol 3: The Face Philadelphia: WB Saunders; 1990:2277–2284

21. Griebie MS, Huff JS. Selective role of partial XI-VIIanastomosis in facial reanimation. Laryngoscope 1998;108:1664–1668

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24. Fackler CD, Perret GE, Bedell GN. Effect of unilateralphrenic nerve section on lung function. J Appl Physiol 1967;23:923–926


Donor Nerve Selection in Facial Reanimation Surgery

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