Hypoglossal and Masseteric Nerve Transfer for Facial Reanimation: A Systematic Review and Meta-Analysis

[Anatomical Identification and Possibilities of Transfer of the Masseteric Nerve for Facial Reanimation]

BACKGROUND

The masseteric nerve (MN) is often used as a donor nerve for facial reanimation. In addition to already established techniques, MN transfer is rapidly gaining importance, mainly due to the single-stage approach of the procedure and its reconstructive potential. This anatomical study and the associated questionnaire study aimed to evaluate the established methods for identification of the MN and its suitability for direct nerve transfer as well as to assess the importance of MN transfer in the daily clinical routine.

MATERIAL AND METHODOLOGY

Bilateral dissection of 25 fresh-frozen head specimens (n=50; 13 female, 12 male) was performed with accompanying measurement of the MN. In a questionnaire study conducted at established centres for facial surgery in German-speaking countries, clinical experience data of MN transfer was collected using the SurveyMonkey software. The data obtained was statistically analysed using Microsoft Excel and presented in numerical tables and boxplots.

RESULTS

Using anatomical landmarks such as the zygomatic arch and the mandibular notch for orientation, the MN was found in 100% of cases. Its average length from the emerging point below the zygomatic arch towards its entry into the masseter muscle was measured to be 22 mm and was the length available for nerve transposition. Tension-free coaptation of the MN with the zygomatic branch was possible in 94% of cases. The questionnaire showed that the MN is considered an important donor nerve for motor nerve transfers and that MN transfer is now largely established as a standard procedure.

DISCUSSION

In accordance with previously published studies, the MN was reliably found at the height of the mandibular notch and, in the vast majority of cases, was suitable for tension-free coaptation with the zygomatic branch. Differences to the existing literature, however, can be seen in the length of the nerve available for nerve transposition and the frequency of its division into several branches before entering the masseter muscle. In German-speaking countries, Cross-Face Nerve Grafting (CFNG) is still the preferred method for facial reanimation surgery. However, MN transfer is also well established by now, both as an alternative and a supplement to other techniques, possibly due to its low donor site morbidity and short time to regeneration.

Task force of the Brazilian Society of Otology - evaluation and management of peripheral facial palsy

OBJECTIVE

To review key evidence-based recommendations for the diagnosis and treatment of peripheral facial palsy in children and adults.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on peripheral facial palsy were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 main parts: (1) Evaluation and diagnosis of facial palsy: electrophysiologic tests, idiopathic facial palsy, Ramsay Hunt syndrome, traumatic peripheral facial palsy, recurrent peripheral facial palsy, facial nerve tumors, and peripheral facial palsy in children; and (2) Rehabilitation procedures: surgical decompression of the facial nerve, facial nerve grafting, surgical treatment of long-term peripheral facial palsy, and non-surgical rehabilitation of the facial nerve.

CONCLUSIONS

Peripheral facial palsy is a condition of diverse etiology. Treatment should be individualized according to the cause of facial nerve dysfunction, but the literature presents better evidence-based recommendations for systemic corticosteroid therapy.

Facial Reanimation After Intratemporal Facial Nerve Schwannoma Resection: A Systematic Review

Objective: To systematically analyze the outcomes of reanimation techniques that have been described for patients undergoing non-fascicle sparing resection of intratemporal facial schwannomas. Methods: A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines of the PubMed, MEDLINE, and Cochrane Central Register of Controlled Trials databases. Results: Eight hundred forty studies were screened with 22 meeting inclusion criteria comprising 266 patients. Most facial nerve reanimations (81.2%) were performed using an interposition nerve graft. The remaining patients underwent hypoglossal-facial nerve transposition (13.9%), primary anastomosis (3.4%), and free muscle transfer (0.1%). Of the reported interposition grafts, the two most utilized were the great auricular (113/199) and sural (86/199) nerves. Interposition nerve grafts resulted in significantly better outcomes in facial nerve function postoperatively than hypoglossal-facial transposition (3.48 vs. 3.92; p < 0.01). There was no difference between interposition grafts. Conclusion: This study systematically reports that interposition nerve grafts, after resection of intratemporal facial schwannoma, result in superior outcomes than hypoglossal-facial nerve transposition in these patients.

Hypoglossal Nerve Transfer for Facial Nerve Paralysis: A Systematic Review and Meta-Analysis

Background: Hypoglossal-facial nerve (12-7) anastomosis can restore symmetry and voluntary movement on the face in patients with facial nerve paralysis. Traditional 12-7 transfer includes direct end-to-end nerve anastomosis, sacrificing the entire hypoglossal nerve. Contemporary, end-to-side anastomosis, or split anastomosis techniques limit tongue morbidity by preserving some hypoglossal nerve. Direct outcome comparisons between these techniques are limited. Objective: To compare reported outcomes of facial movement, tongue, speech, and swallow outcomes among the different types of hypoglossal-facial nerve anastomosis schemes. Evidence Review: For this systematic review and meta-analysis, a comprehensive strategy was designed to search PubMed, Scopus, and the Cochrane Database from inception to January 2021, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis, reporting guideline yielding 383 results. Any participant who underwent 12-7 transfer using any of the three techniques, with or without an interposition graft, and had documented preoperative and postoperative evaluation of facial nerve function with a validated instrument such as House-Brackmann (HB), was considered for inclusion. Secondary outcomes of synkinesis, tongue atrophy, and speech or swallowing dysfunction were also compared. Forty-nine studies met inclusion criteria, representing data from 961 total patients who underwent 12-7 transfer. Results: The proportion of good HB outcomes (HB I-III) did not differ by anastomosis type: End-to-side and end-to-end anastomosis (73% vs. 59%, p = 0.07), split and end-to-end anastomosis (62% vs. 59%, p = 0.88), and end-to-side anastomosis and split anastomosis (73% vs. 62%, p = 0.46). There was no difference in reported synkinesis rates between the anastomosis types. However, end-to-side anastomosis (z = 6.55, p < 0.01) and split anastomosis (z = 3.58, p < 0.01) developed less tongue atrophy than end-to-end anastomosis. End-to-side anastomosis had less speech/swallowing dysfunction than end-to-end anastomosis (z = 3.21, p < 0.01). Conclusion: End-to-side and split anastomoses result in similar HB facial nerve outcomes as the traditional end-to-end 12-7 anastomosis. End-to-side anastomosis has decreased complications of tongue atrophy and speech/swallow dysfunction compared to end-to-end anastomosis. In addition, split anastomosis has decreased rates of tongue atrophy compared to end-to-end anastomosis.

Composite Sterno-Omohyoid Functional Muscle Transfer for Dual-Vector Smile Reanimation: A Case Series

Background: Facial reanimation flaps often add bulk and produce single-vector smiles, and multivector flaps frequently require challenging intramuscular dissection. Objective: To evaluate the effectiveness of sterno-omohyoid flap (SOHF) transfer for dual-vector smile reanimation by measuring upper dental show and oral commissure movement. Methods: SOHF transfers from 2017 to 2020 were retrospectively evaluated using eFACE and Emotrics software. Results: Four patients with flaccid and one with nonflaccid facial paralysis were identified (four females and one male, median age: 39 years (range: 38-65); two acoustic neuromas, two congenital, one temporal bone fracture). Median follow-up was 20 months (range: 14-26). All flaps received masseteric nerves and two had additional cross-face grafts. Four developed contraction [median time to contraction: 5.5 months (range: 3-10)]. Mean oral commissure excursion and dental exposure improvements were 7.6 ± 4.0 mm (p = 0.03) and 2.9 ± 1.8 mm (p = 0.05), respectively. Dynamic, smile, and midface-smile eFACE improvements were 20.3 ± 6.8 (p = 0.007), 25.5 ± 14.5 (p = 0.03), and 50.5 ± 12.0 mm (p = 0.004) points, respectively. Mean SOHF mass was 14 ± 1.7 g. Conclusion: The SOHF is a small flap that provides dual-vector smile reanimation in flaccid and nonflaccid facial paralysis.

Resect, rewire, and restore: Nerve transfer salvage of neurological deficits associated with soft tissue tumors in a retrospective cohort series at a tertiary reconstructive center

AIMS

We aimed to explore the effectiveness of nerve transfer as an intervention to restore neurological deficits caused by extremity tumors through direct nerve involvement, neural compression, or as a consequence of oncological surgery.

METHODS

A retrospective cohort study of consecutive cases was conducted, including all patients who underwent nerve transfers to restore functional deficits in limbs following soft tissue tumor resection. The threshold for a successful nerve transfer was a BMRC motor grade of 4/5 and sensory grade of 3-3+/4 with protective sensation.

RESULTS

In total, 29 nerve transfers (25 motor and 4 sensory) were completed in 11 patients, aged 12-70 years at referral, over a 6-year period to 2020. This included 22 upper limb and 3 lower limb motor nerve transfers. The timing of delayed nerve transfer reconstructions was 1-15 months following primary oncological resection, with immediate simultaneous reconstructions performed in 4 cases. The threshold for success was achieved in 82% of upper limb and 33% of lower limb motor nerve transfers, while all sensory transfers were successful in restoring protective sensation.

CONCLUSION

Nerve transfer surgery, a well-established technique in restoring deficits following traumatic nerve injury, is further demonstrably relevant in extremity oncological reconstruction, especially as it can be performed remotely to the tumor location or resection site and introduces a healthy nerve or fascicle to rapidly reinnervate distal muscles without sacrificing major function. This study further illustrates the importance of early recognition and referral to specialist services where multi-disciplinary surgical resection and reconstructive planning can be conducted.

LEVEL OF EVIDENCE

IV Clinical Case Series.

Contribution and safety of the side-to-end hypoglossal-to-facial transfer in multidisciplinary facial reanimation

BACKGROUND

This study evaluates facial and tongue function in patients undergoing side-to-end hypoglossal-to-facial transfer (HFT) with additional techniques.

METHODS

Thirty-seven patients underwent a side-to-end HFT. Twelve had additional cross-face grafts, and 9 had an additional masseter-to-facial transfer. Facial was assessed with House-Brackmann (HB), Sunnybrook Facial Grading Scale (SFGS), and eFACE. Martins scale and the Oral-Pharyngeal Disability Index (OPDI) were used to assess tongue function.

RESULTS

Ninety-four percent of cases reached HB grades III-IV. Mean total SFGS score improved from 16 ± 15 to 59 ± 11, while total eFACE score from 52 ± 13 to 80 ± 5. Dual nerve transfers were a predictor for a better eFACE total score p = 0.034, β = 2.350 [95% CI, 0.184-4.516]), as well as for a higher SFGS total score (p = 0.036, β = 5.412 [95% CI, 0.375-10.449]). All patients had Martin's grade I. Mean postoperative OPDI scores were 84 ± 17 (local physical), 69 ± 16 (simple and sensory motor components), 82 ± 14 (complex functions), and 73 ± 22 (psychosocial).

CONCLUSIONS

The side-to-end HFT offers predictable facial function outcome and preserves tongue function in nearly all cases. Dual nerve transfers appear to improve the final outcome.