Facial Nerve Reconstruction with Free Vascularized Composite Nerve Flap from Intrapetrous Portion to Terminal Branches—Case Report

Abstract

The case presented here is a delayed reconstruction of a facial nerve defect after radical parotidectomy without a useful nerve stump at the stylomastoid foramen. A composite free flap was used to reconnect the nerve’s intrapetrous portion to the peripheral branches and reconstruct the soft-tissue deficit.

Keywords

facial palsy - radical parotidectomy - vascularized nerve transfer

Facial nerve palsy is a significant disability for most patients, especially young ones. The lack of hemifacial movement may cause social inhibition and a profound psychological disturbance. Impairment in eye protection through deficient blinking mechanism compounds the problem. It is widely accepted that the treatment of facial paralysis depends on the time of denervation. Roughly 1 year is set as the limit after which direct nerve repair should yield to muscle substitution techniques.[1] [2] The injury level also plays a role in the regeneration times, although to a much lesser degree than in longer extremity nerves.

Parotid tumor surgery is one of the leading causes of facial nerve injury, especially en bloc resections. Repair of the resultant nerve defect using nerve grafts (NG) from the main trunk at the stylomastoid foramen to the terminal branches has been widely described with overall good results.[3] NG depend on the revascularization from the surgical bed and, thus, are not optimal in previously irradiated wound beds.[4] Taylor and Ham described vascularized nerve transfers (incorrectly named vascularized nerve grafts in the past) first in 1976.[5] In contrast to NG, the regeneration through vascularized nerve transfers (VNT) is known to be independent of the wound bed’s quality. Regenerating axons grow faster through VNT, but the definitive outcome is not significantly better than NG in favorable wound beds.[6] [7] Under certain clinical conditions, a VNT can be superior to NG, that is, in heavily scarred or irradiated areas, in very long defects, when additional tissues are also needed for the reconstruction of composite defects, and probably in cases with long denervation time at presentation,[8] [9] [10] although the level of evidence of this superiority is low.

Reconstruction of extracranial defects of the facial nerve, especially after radical parotidectomy, has been widely described, with some reports on immediate vascularized nerve use with excellent results.[11] VNT, as part of composite free flaps for simultaneous nerve repair and soft-tissue reconstruction or augmentation, has also been described.[12] [13] [14]

The repair of the facial nerve’s intracranial injuries, mainly during tumor removal of the posterior fossa with NG from intra- to extracranial portions of the nerve, has been described with good results.[15] [16]

The case presented here is a delayed reconstruction of a facial nerve defect after radical parotidectomy without a useful nerve stump at the stylomastoid foramen. A composite free flap was used to reconnect the nerve’s intrapetrous portion to the peripheral branches and reconstruct the soft-tissue deficit.

Case Report

A 34-year-old woman presented with a right complete facial paralysis after radical parotidectomy and radiation therapy (60 Gy) for parotid adenocarcinoma ([Fig. 1a], [b]). The denervation time was 13 months. The parotid region was depressed and heavily scarred, and according to the previous operative notes, the facial nerve had been resected flush to the stylomastoid foramen. No perineural infiltration was present in the pathology report. No additional electrophysiologic tests were deemed necessary for decision-making in this case.

Fig. 1 (A,B) Preoperative image of the patient with 13-month-old right facial paralysis due to radical parotidectomy and radiation therapy.

Given the long denervation time, the irradiated area, and the unlikely presence of a suitable proximal extracranial nerve stump, a vascularized nerve reconstruction was planned. Though the previous parotidectomy scar, with a postauricular extension, the distal five main branches of the facial nerve (frontal, orbital, zygomatic, buccal, and marginal mandibular) were identified and tagged. A standard mastoidectomy was performed to expose the third portion of the intrapetrous facial nerve. The nerve was sectioned in the midpoint of this portion and examined visually at high magnification to confirm a healthy fascicular pattern. Using the right lateral circumflex femoral vessels (LCFV), a composite flap was harvested consisting of two adipofascial islands (one based on the anterolateral tight [ALT] perforator and the other on a branch to the tensor fasciae lata), and a 13-cm segment of the motor nerve of the vastus lateralis (VL) was dissected distally to include five distal branches with their associated vascular supply ([Fig. 2]). The right lingual artery and vein were dissected as recipients.

Fig. 2 A composite free flap from the lateral circumflex femoral vessels, including two soft-tissue islands and a 13-cm-long segment of the motor nerve of the vastus lateralis with five distal branches, was elevated from the right side.

The proximal end of the VL motor nerve was coapted to the intrapetrous facial nerve with epineural 10/0 nylon sutures under the microscope ([Fig. 3]). The distal five branches of the VL nerve were coapted to the facial nerve’s distal five branches with 10/0 nylon. The flap’s soft-tissue islands were used for filling the resultant dead space after the mastoidectomy and for subcutaneous augmentation of the parotid area ([Fig. 4]). The flap vessels were anastomosed end-to-end to the lingual artery and vein. A portion of fat tissue was left exposed in the mastoid region for monitoring and left to heal secondarily. The postoperative course was uneventful. Free ambulation was allowed at 2 weeks, and unrestricted physical activity at 1 month.

Fig. 3 After radical mastoidectomy and drilling of the third portion of the intrapetrous facial nerve, the proximal nerve repair was performed with 10/0 nylon sutures.

Fig. 4 The distal branches of the motor nerve of the vastus lateralis were coapted to the five distal main branches of the facial nerve with 10/0 nylon. The mastoidectomy defect and the parotid area were reconstructed with the two soft-tissue islands of the flap. The flap was revascularized to the lingual vessels.

At four months follow-up, the symmetry of the face was recovered at rest ([Fig. 5]). The voluntary function of the lower four branches improved steadily afterward. The frontal branch did not recover function. At 3 years of follow-up, active facial nerve function was grade II in the House–Brachmann score[17] in the lower branches but no function in the frontal branch. An eyebrow pexy was performed at 2 years to palliate the eyebrow asymmetry ([Fig. 6]). No identifiable functional donor deficit was reported by the patient.

Fig. 5 At 4 months, the symmetry of the face at rest was recovered.

Fig. 6 Function at 3 years at rest (a), mild contraction (b), and forced contraction (c). The profile of the mastoid defect and the parotid area was acceptable to the patient (d).

Discussion

Facial nerve palsy in a young patient can be devastating from a social and psychological standpoint. Multiple treatment options exist, depending basically on the denervation time, the limit for nerve repair being roughly 1 year.[1] [2] Late (over 12 months) paralysis has a worse prognosis since reinnervation is less predictable, and functioning muscle transfers have inferior results compared with early nerve repair.[2] The case presented was past the upper limit for direct nerve reconstruction, but given the patient’s age and gender, the best possible result was aimed. Time was a primary concern in this case, and the reported faster axonal growth in VNT compared with NG was considered in the planning.[6] [7] The irradiated field and the concomitant need for soft-tissue augmentation in the parotid region also favored a VNT as part of the composite free flap.[12] [13] [14]

Reconstruction of nerve defects after oncological resection of parotid gland malignancies usually entails nerve repair from the facial trunk near the stylomastoid foramen to the five main distal branches. NG and VNT have been described in this setting with overall good results, especially in immediate reconstructions.[11] When the proximal stump cannot be identified (usually in delayed cases), cross-facial grafts, or crossover transfers (masseteric nerve) are the usual treatments.[2] Intra-extra cranial NG have been described for acute repair of intradural or intrapetrosal injuries with acceptable results.[15] [16] Because these are immediate reconstructions, the time of regeneration is less of a concern.

There is a growing body of evidence of the noninferiority of expendable motor nerves compared with the more popular sensory nerves as donors for NG. The avoidance of skin hypoesthesia and possible painful neuroma and limited donor morbidity could be advantageous. Thoracodorsal nerve or portions of the femoral nerve have been investigated as donor areas for NG.[18] [19] [20] Motor nerves as VNT have also been described either alone or as a part of composite free tissue transfers for facial defects.[21] [22]

When the extracranial portion of the facial nerve is not usable, using the intrapetrous portion through mastoidectomy and petrous drilling seems logical to have a native ipsilateral proximal nerve stump, even at the expense of increasing the length of the nerve defect. In this case, the healthy intrapetrous facial nerve was the optimal choice for direct nerve reconstruction. Training in skull base approaches and familiarity with mastoidectomy and facial nerve drilling is advantageous for reconstructive surgeons. Otherwise, ENT surgeons should be consulted. Other alternatives of treatment as cross facial NG would have taken too long to regenerate in this case and would have likely resulted in poor function. The possibility of recycling these grafts as recipients for an eventual free functional muscle transfer in case of failure to reinnervate could be part of this hypothetical alternative. Closer-target nerve transfers, that is, masseteric nerve, would take shorter to grow into the ipsilateral facial nerve, but in this case, NG would have been necessary to reach the five distal branches since the main facial trunk was missing. This option was, therefore, discarded. The increase in the nerve defect’s length using the intrapetrous facial nerve can be compensated for by the faster axonal growth in VNT and still achieve a native facial nerve restoration. To the best of the authors’ knowledge, a VNT from the intrapetrous facial nerve to terminal branches has not been described before.

Conflict of Interest

None declared.

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Publication History

Article published online:
30 June 2021