CONSULTATIONS

MANAGEMENT OF FAILED NERVE GRAFT FOLLOWING FACIAL NERVE RESECTION FOR FACIAL NERVE NEUROFIBROMA

MARK MAY, MD, BRUCE GANR, MD, and GORDON HUGHES, MD

This issue’s Consultations involves a difficult fa- cial nerve problem, that of a facial nerve graft with no evidence of reinnervation 1 year later. Almost all facial nerve grafts achieve some degree of nerve reinnervation, depending on length of the graft, radiotherapy, age of the patient, and other considerations. When there is no reinnervation whatsoever, rather difficult diagnostic and ther- apeutic options must be considered, as with this case.

CLINICAL HISTORY

A 27-year-old, healthy, white man had a radical parotidectomy with facial nerve resection for a facial nerve neurofibroma. The tumor had en- larged the fallopian canal and extended proxi- mally from the pes anserinus to the proximal por- tion of the tympanic segment of the facial nerve. The tumor resection, performed 1 year previously,

Readers are invited to submit pafticu/ar/y difficult cases for consideraation to Roger L. Crumley, MD, Editor, Consultations, 350 Parnassus #501, San Francisco, CA 941 17.

From the Department of Otalaryngology. University of Pittsburgh School of Medicine, Pittsburgh, PA (Dr. May); the Department of Otolaryngol- ogy-Head and Neck Surgery, University of Iowa. Iowa City, IA (Dr. Gantz); and the Department of Otolaryngology and Communicative Disorders. Cleveland Clinic Foundation, Cleveland, OH (Dr. Hughes). Accepted for publication September 30, 1986.

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184 Failed Nerve Graft Following Facial Nerve Section

was accomplished via modified radical mastoidec- tomy. Gross tumor involvement of the nerve ap- peared to stop distal to the cochleariform process and a tiny frozen section of the proximal end of the resected nerve was negative for tumor. Per- manent biopsy sections showed neurofibroma to be within 1.5 high-power fields of the proximal transection site.

A sural nerve graft was laid in the fallopian canal from the geniculate ganglion (without su- ture), and Gelfoam was used to cover and secure the proximal portions of the nerve graft. Three 10-0 monofilament sutures were used to approx- imate the distal end of the graft to the pes an- serinus.

Postoperatively, the patient developed a sup- purative infection in the lower portion of the postauricular incision. A small abscess cavity was noted 7 days postoperatively immediately below the mastoid tip. The nerve graft could be seen through the dehiscent wound. The infection re- sponded to intravenous antibiotics and gentle packing. The defect gradually granulated and closed by secondary intention.

Twelve months later, the patient returned, complaining of lack of facial movement. One month prior to the visit (11 months after nerve graft), an electromyogram (EMG) demonstrated only fibril- lation potentials. The patient’s eye was well lu- bricated and demonstrated a satisfactory Bell’s phenomenon. A computed tomographic (CT) scan

HEAD & NECK SURGERY Jan/Feb 1987

did not reveal any bony enlargement near the ge- niculate ganglion (no gross recurrence of tumor).

1. Because it has been 12 months since the procedure was performed, do you believe there is reason to wait longer before further diag- nostic tests or surgical exploration are per- formed?

Dr. Hughes: No. Sufficient time has elapsed for axon regrowth from the cochleariform process to the facial muscle. EMG evidence should be dem- onstrated by this time.

Dr. May: Because there has been no recovery in a year, it would be appropriate to assume there is need for revision.

Dr. Gantz: No. One year has elapsed, which is sufficient time for EMG to demonstrate reinner- vation.

2. What further diagnostic tests would you order at this time?

Dr. Hughes: I believe the proximal nerve anas- tomosis was disrupted by the infection, with wound contraction in the soft tissues at the mastoid tip, or direct inflammation with separation of the nerve at the geniculate ganglion. I am less inclined to believe that the distal anastomosis failed or that the infection rendered the nerve graft incapable of propagating axon growth. It is also possible that tumor is present at the proximal site (neurofi- broma was within 1.5 high-power fields on patho- logic study).

Dr. May: The infection was probably the cause of the nerve graft failure. Tumor appears to have been excised or, in any case, does not show up on CT scans. I would suspect that infection produced scarring of the nerve graft in the immediate ex- tracranial segment.

Dr. Gantz: Three possibilities exist: (1) The most probable explanation is nonvascularization of the nerve graft secondary to the abscess. Al- though the facial nerve is often relatively resis- tant to infection, a free nonvascularized nerve graft would not be expected to fare well in an abscess cavity, as described in this case. (2) The second possibility is dehiscence of the proximal anasto- mosis. It is frequently not possible, as in this case, to place a neurorrhaphy suture near the genicu- late ganglion, leaving the anastomosis susceptible to disruption. (3) The third possibility is recurrent tumor at either end of the nerve graft. It is con- ceivable that a small regrowth of tumor at the proximal anastomosis could prevent nerve regen- eration and healing, without being visible on CT scan.

Dr. Hughes: No further preoperative diagnos- tic tests are required. Surgery is indicated to en- sure that the proximal nerve segment is tumor- free and to rehabilitate the facial paralysis. I would prepare the patient for postauricular exploration to the geniculate ganglion and for possible hy- poglossal-facial anastomosis if necessary. I would avoid middle fossa exploration to minimize poten- tial infection from the mastoid cavity unless tu- mor resection was required proximal to the ge- niculate ganglion.

Dr. Gantz: I would obtain a magnetic reso- nance scan, which might reveal recurrent tumor near the geniculate ganglion more definitively than would CT scan. I would also repeat a high-reso- lution CT scan because tumor recurrence in the proximal portion of the tympanic segment would be critical. Electroneuronography would be of no benefit due to the chronicity of the paralysis, as it is useful only within the first 3 months after the procedure.

Dr. May: I do not believe any further scans or electrical tests would be beneficial at this time.

3. What would you assume to be the most probable cause of nerve graft failure in this case?

4. Briefly outline your treatment plan for this patient, including: (1) Is it necessary to expose the middle cranial fossa to explore the proximal anastomosis? (2) If no tumor recur- rence is found, would you attempt to replace the nerve graft? (3) What has been your ex- perience and what is your current thinking on the routing of a nerve graft through a mas- toidectomy cavity; alternate routes? (4) Does muscle transfer have a role, given the muscles continue to generate fibrillation potentials?

Dr. Hughes: If a proximal anastomosis prob- lem exists, the key question is whether you can correct it comfortably through a postauricular ap- proach. If so, a second nerve graft can be inter-

Failed Nerve Graft Following Facial Nerve Section HEAD & NECK SURGERY Jan/Feb 1987 185

posed, or perhaps the ends can be mobilized and reapproximated, which has obvious advantages over hypoglossal-facial anastomosis. On the other hand, another year would be required before any significant function returned. At the time of prox- imal nerve examination, if the proximal anasto- mosis was intact, and if the nerve was grossly normal in appearance and probably free of tumor, I would leave it alone. I would also explore the distal anastomosis to ensure it was intact. If both proximal and distal sites appeared intact, no ex- planation for the failed result is obvious. I would assume that a second grafting attempt would again fail and that a nerve-substitution procedure such as the hypoglossal-facial anastomosis would be appropriate. However, before performing this sur- gery, and despite the normal appearance of the proximal nerve site, I would nonetheless obtain frozen and permanent nerve sections for pathol- ogy. If tumor was histologically present, further local resection and nerve grafting would be ap- propriate. If no tumor was found, the hypoglossal- facial crossover could proceed.

The only remaining concern is that histologic tumor proximal to the geniculate ganglion area might require middle fossa surgery for resection, for which the patient has not been prepared. Some patients may prefer to have a half-head shave and possible middle fossa surgery at the same stage and others may prefer to have formal tumor re- section via the middle fossa at a second stage when the situation is more clearly understood. In either case, the potential benefits of tumor resection through the middle fossa (if required) would out- weigh the potential risks of mastoid cav- ity-middle fossa infection, and I would advise middle fossa surgery in that less-likely circum- stance.

Dr. May: An infection following a nerve graft is a common cause of failure. In such a situation, a procedure that bypasses the area of infection certainly would be appropriate. I would begin by exploring the distal anastomosis in the parotid gland, then proximally into the mastoid, and all the way to the geniculate area. As I explored, I would biopsy the nerve and obtain frozen-section examinations in an attempt to ascertain which portion of the nerve might contain recurrent tu- mor and which portion might have been pene- trated with axons.

It would be important to inspect the proximal anastomotic site carefully for dehiscence and/or tumor recurrence. If no tumor is present and the

biopsies show some axons (even in scar tissue), it may be possible that some recovery will still take place, despite the passage of 1 year. One cannot generally expect good results from a second nerve graft following a failure but I see no alternative in this case.

One type of nerve graft that might be appro- priate would be from the stump of the facial nerve in the cerebellopontine angle through a posterior cranial fossa approach bypassing the temporal bone with a sural graft to the extracranial segment. Special consideration would be directed toward separately reanimating the eye region with a br6w lift, and, if necessary, a gold weight or a spring implant, and perhaps tightening the lower lid. If the bypass graft were successful, rehabilitation of the mid and lower portions of the face could be considered in 1-14 years.

We have been combining nerve grafts in many cases such as this with a temporalis muscle trans- position by placing the temporalis muscle lateral to the superficial musculo-aponeurotic system, where peripheral branches of the facial nerve could be spared and would in no way interfere with spontaneous regeneration through the appropri- ate nerve graft from the brainstem to the extra- cranial portion. This would provide immediate reanimation and would augment any recovery achieved with a nerve graft. However, the tem- poralis transfer is frequently performed at a later stage, when the patient requests enhancement of the smile.

If after 14 years, the nerve graft had not re- covered, I would consider a jump graft using the sural nerve and placing it from the XIIth nerve to the lower mid-division of the facial nerve. A hypoglossal-facial anastomosis must be carefully considered and the patient must be apprised of the effects of hypoglossal denervation. If success- ful, it would provide tone, but only voluntary, not involuntary, motion. I find that 10% of patients undergoing this procedure get too much motion, and 10% get poor results without enough motion, thus, the procedure is only 80% effective. All op- tions, with the anticipated results, should be shared with the patient as part of the decision-making process.

Dr. Gantz: If both CT and magnetic resonance scans are negative and there are no further rea- sons to suspect tumor recurrence, the most ex- peditious course would be to explore the modified radical mastoidectomy cavity for the purpose of biopsy of the nerve.

186 Failed Nerve Graft Following Facial Nerve Section HEAD & NECK SURGERY Jan/Feb 1987

In exploring the nerve proximal and distal to the abscess site, I would obtain frozen-section ex- aminations, as vascularization and, to a certain extent, innervation of nerve graft can be deter- mined on hematoxylin-eosin stains. If the biopsy specimens prove positive for viable nerve, the problem is more distal to the positive biopsy site. If no viable nerve is found, further proximal biop- sies could be performed to determine the amount of axon penetration of the graft. Through this ex- posure, the entire facial nerve distal to the genic- date ganglion can be explored and evaluated, much as it had been done at the original operation.

If fibrosis is found at the geniculate ganglion area, I would not perform middle cranial fossa surgery that same day, but would await the re- sults of the permanent biopsy sections to ensure this is the appropriate step. If this biopsy shows only fibrosis, a middle cranial fossa exposure would be advisable. In this exposure, I would proceed to the internal auditory canal to find viable nerve

and would then dissect the labyrinthine segment toward the geniculate ganglion. I would rebiopsy the geniculate ganglion for confirmation of fibro- sis, cut it away, and route the nerve distally.

This graft would have to be performed with the opposite sural nerve and would probably be routed posteriorly through the mastoid cavity. It would be advantageous to cover the nerve graft with a muscle flap for protection of the graft, as well for graft vascularization. The latter effect would, of course, be possible with a free muscle graft and might be somewhat difficult with tem- poralis muscle, because it is usually divided in most middle fossa approaches. If this technique could be modified, I would use temporalis muscle; otherwise, a portion of the sternocleidomastoid muscle could be used to obliterate the cavity and cover the nerve graft.

If, after 8-10 months, reinnervation was not demonstrated on EMG, I would consider hypo- glossal-facial anastomosis.

Summary

Further diagnostic tests: None required (May, Hughes) Repeat high-resolution CT and magnetic resonance scans (Gantz)

Proximal nerve anastomosis disrupted by infection or tumor at proximal end of graft (Hughes) Infection and secondary scarring (May) Nonvascularized nerve graft secondary to abscess, dehiscence of proximal anastomosis, or

Cause of nerve graft failure:

recurrent tumor at either end of graft (Gantz) Diagnosis and treatment plan:

Explore proximal and distal ends of Raft. If intact, perform hypoglossal-facial anastomosis. Biopsy nerve: if tumor present, resect; if no tumor present, perform hypoglossal-facial anastomosis. If tumor present, be prepared for middle cranial fossa approach to resect proximal tumor (Hughes)

Explore distal nerve and continue exploration proximally, biopysing nerve at several levels. Consider regrafting from cerebellopontine angle through posterior fossa with a sural graft with the extracranial segment. Reanimate eye region with brow lift and eyelid procedure (gold weight, spring implant, and lid tightening procedure). Consider temporalis transfer and additional reinnervation at time of regraft procedure. Consider hypoglossal-facial anastomosis only after extensive discussion of residuals and “donor defect” (May)

If magnetic resonance and CT scans negative, biopsy nerve proximal and distal to abscess site. If fibrosis (and no axons) found at geniculate ganglion, do not perform middle fossa surgery the same day; instead, await permanent-section examination results. When performing middle fossa procedure, go immediately to internal auditory canal and proximal nerve. Cover nerve graft in mastoid cavity with muscle flap (temporalis or sternocleidomastoid) for protection and vascularization of nerve graft. Wait 8-10 months and obtain EMG. If no reinnervation imminent, consider hypoglossal-facial anastomosis (Gantz)

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