Spontaneity Assessment in Dually Innervated Gracilis Smile Reanimation Surgery

Abstract

IMPORTANCESurgeons have sought to optimize outcomes of smile reanimation surgery by combining inputs from nerve-to-masseter and cross-face nerve grafts. An objective assessment tool could help surgeons evaluate outcomes to determine the optimal neural sources for smile reanimation.OBJECTIVE To evaluate the use of a novel video time-stamping method and standard outcome measurement tools to assess outcomes of facial reanimation surgery using various innervation strategies. DESIGN, SETTING, AND PARTICIPANTSCohort study assessing the outcomes of dually innervated gracilis free muscle transfers vs single-source innervated gracilis transfer performed at a tertiary care facial nerve center between 2007 and 2017 using a novel, video time-stamping spontaneity assessment method. The statistical analyses were performed in 2018. INTERVENTIONS Dually innervated gracilis free muscle transfers or single-source innervated gracilis transfer.MAIN OUTCOMES AND MEASURES Spontaneous smiling was assessed by clinicians and quantified using blinded time-stamped video recordings of smiling elicited while viewing humorous video clips. RESULTSThis retrospective cohort study included 25 patients (12 men and 13 women; median [range] age, 38.4 [29.3-46.0] years) treated with dually innervated gracilis free functional muscle graft for unilateral facial palsy between 2007 and 2017. Smile spontaneity assessment was performed in 17 patients and was compared with assessment performed in 24 patients treated with single-source innervated gracilis transfer (ie, nerve-to-masseter-driven or cross-face nerve graft-driven gracilis [n = 13]) (demographic data not available for NTM and CFNG cohorts). The use of time-stamped video assessment revealed that spontaneous synchronous oral commissure movement in a median percentage of smiles was 33% in patients with dually innervated gracilis (interquartile range [IQR], 0%-71%), 20% of smiles in patients with nerve-to-masseter-driven gracilis (IQR, 0%-50%), and 75% of smiles in patients with cross-face nerve graft-driven gracilis (IQR, 0%-100%). Clinicians graded smile spontaneity in dually innervated cases as absent in 40% (n = 6 of 15), trace in 33% (n = 5 of 15) and present in 27% (n = 4 of 15). No association was demonstrated between clinician-reported spontaneity and objectively measured synchronicity.CONCLUSIONS AND RELEVANCE Dually innervated gracilis free muscle transfers may improve smile spontaneity compared with masseteric nerve-driven transfers but not to the level of cross-face nerve graft-driven gracilis transfers. Quantifying spontaneity is notoriously difficult, and most authors rely on clinical assessment. Our results suggest that clinicians may rate presence of spontaneity higher than objective measures, highlighting the importance of standardized assessment techniques.LEVEL OF EVIDENCE 4.

Innervation options for gracilis free muscle transfer in facial reanimation

“…Faria et al [21] reported first contractions observed after 3-6 months, with an average of 3.7 months. This is in contrast to the CFNG, which can take up to two years for maximal results from the time of initial surgery [13] . Moreover, GFMT with masseteric nerve innervation can be done as a single-stage procedure, which is more ideal for patients with significant medical comorbidities and operative risk.…”

“…The nerve is then allowed to grow through the cable graft, and the second stage is performed when the regenerated axons have reached the distal end of the cable graft. The mean interval between the two stages of the operation typically ranges between 8 to 12 months in adults and 6 to 9 months in children [3,4,13] . This timeline depends on the rate of facial axonal regeneration through the nerve graft, which can be followed clinically using the progression of the Tinel sign through the length of the graft.…”

“…Using a CFNG to innervate the GFMT has the potential advantage of restoring a smile that is spontaneous and coordinated with the contralateral side and is considered by some as the only option that produces a spontaneous smile in patients with complete flaccid facial paralysis [13,19,21] . As previously mentioned, videography for the SSA found that 75% of patients with CFNG-innervated GFMT had spontaneous smiles compared to 20% of patients with masseteric nerve-innervated GFMT [14] .…”

“…In its original description by Harii et al [2] in 1976, the deep temporal nerve was used as the donor source of innervation. Since then, various other donor nerves have been described in the literature, including the cross facial nerve graft (CFNG) [3][4][5][6] , masseteric nerve [7][8][9][10][11] , hypoglossal nerve [12,13] , spinal accessory nerve (SAN) [6,13] , and combinations [14][15][16][17] of the above. Each donor nerve option has unique benefits and drawbacks, and there is no universal consensus on one option that is ideal for all scenarios.…”

“…The CFNG, which utilizes midfacial branches of the contralateral facial nerve, has the potential of creating a spontaneous and synchronous smile. However, it has lower reliability and less oral commissure excursion than other donor nerves [8,13,18] . In contrast, the masseteric nerve, a branch of the trigeminal nerve, contains a greater axonal load and more reliable oral commissure excursion, but at the expense of spontaneity [8,19] .…”