Page 106 - Read Online

Page 10 of 14 Gossett et al. Plast Aesthet Res 2021;8:60 https://dx.doi.org/10.20517/2347-9264.2021.69

hypoglossal nerve need to push their tongue against their lower teeth to induce a smile, and there is a low
[13]
likelihood of patients being able to achieve spontaneous smile through cortical adaptation . Nevertheless,
hypoglossal innervation of GFMT may provide better excursion and shorter time to achieving movement
[51]
when compared to CFNG, likely due to the higher axonal (9778 ± 1516) . Hypoglossal innervation can also
provide a good resting tone and may be used in conjunction with other neural sources, including CFNG .
[52]
[53]
Ueda et al. performed 17 free muscle transplantations (12 latissimus muscle transfers, 4 GFMT, and 1
rectus abdominis muscle transfer) innervated by the hypoglossal nerve in patients between 22 and 74 years
of age. This procedure was chosen to minimize the operative time in older individuals (12 patients over age
60) and to rehabilitate three younger patients who had undergone a CFNG with no subsequent movement.
The initial movement of the free muscle transplant was noted from 4 to 9 months post-operatively. A
majority achieved a “good” function (n = 13) with synchronous and natural expressions, and the remaining
patients achieved a “satisfactory” function (n = 4) with less synchronicity. The study reported tongue
atrophy in all patients, with more atrophy when a larger portion of the hypoglossal was utilized.
Interestingly, there was no significant difference in functional outcome between patients with different
sections of hypoglossal nerve used. Therefore, morbidity could likely be reduced by utilizing lower branches
that innervate only suprahyoid musculature and avoiding branches innervating lingual musculature .
[53]
Hontanilla and Aubá also reported on a single 30-year-old patient who had bilateral facial nerve paralysis
[54]
after resection of a brain tumor, precluding availability of the facial or masseteric nerves. The surgeons
chose to perform bilateral GFMT innervated by hypoglossal in two separate procedures, each utilizing direct
coaptation of the obturator nerve to the hypoglossal nerve. This patient was not reported to experience
lingual atrophy or functional deficits from donor site morbidity .
[54]
AREAS FOR FUTURE INVESTIGATION
One of the greatest hurdles in the current literature for facial reanimation is the heterogeneity of outcome
measures that exist. While there is a growing body of research assessing the various sources of innervation
for GFMT, the ability to compare or aggregate data across different studies remains limited. In 2020,
[55]
Vila et al. performed the only systematic review and meta-analysis of outcomes for GFMT based on
different donor nerves. They included ten studies in their systematic review, each using excursion and
symmetry as outcome measures. Three of these studies reported outcomes using FACE-gram and were
ultimately included in their meta-analysis, which found that excursion was significantly higher in GFMT
with masseteric nerve innervation than CFNG. At the same time, symmetry was not significantly different
between the two groups. Unfortunately, spontaneity could not be included in the meta-analysis due to
heterogeneity in outcome measures, although the data suggested improved spontaneity with CFNG.
Overall, they concluded that they were unable to make definitive recommendations regarding the optimal
donor nerve for GFMT due to a lack of uniform reporting measures.

Adoption of universal outcome measures in the study of facial reanimation would be groundbreaking in our
ability to compare and reproduce future investigations. To this end, Sir Charles Bell’s Society for the
treatment of facial paralysis advocates for the use of a common facial analysis measurement software and
[56]
a quantitative assay for smile spontaneity [14,57] . In terms of donor nerve choice for GFMT, further study is
needed to assess the outcomes of single-stage vs. two-stage dually innervated GFMT and the optimal
patterns of dual nerve coaptation that optimize the individual benefits of masseteric nerve and CFNG
donors.

CONCLUSIONS
Dynamic smile restoration is crucial to treating the functional and aesthetic impairment resulting from
facial paralysis. For longstanding or congenital paralysis in which the native facial mimetic musculature is