Summary
Background
Synchronicity of the oral commissure movement of a bilateral smile is a significant
goal for reconstruction in facial reanimation and may only be guaranteed with use
of the facial nerve as a donor nerve. Yet over the years several studies report some
degree of spontaneity in certain patients when using a non-facial donor nerve, which
indicates that synchronous initiation of the smile might be achievable with other
donor nerves. We designed a prospective cohort study to evaluate whether pre-operative
involuntary activation of the masseteric nerve during smile predicts development of
a synchronous smile development when using the masseteric nerve for reanimation.
Methods
In a prospective cohort study unilateral long-standing facial palsy patients scheduled
for dynamic smile reanimation with a free functional muscle transplant using the masseteric
nerve as a donor nerve were preoperatively evaluated via EMG for involuntary activation
of the masseter muscle upon smiling, which we called coactivation. Postoperatively,
six months after noting the first muscle contraction smile synchronicity was evaluated.
We analyzed the synchronicity of the bilateral smile development by analyzing slow-motion
video sequences of the patients that were taken while the patients were watching funny
video sequences. Results were then correlated with the pre-operative EMG.
Results
30 patients were recruited for this prospective study and underwent facial reanimation
surgery with a free gracilis transfer innervated by the masseteric nerve. 19 patients
demonstrated involuntary coactivation of the masseter muscle upon smiling and 11 did
not. Postoperatively all patients could demonstrate a voluntary smile. 94% of patients
who had preoperative coactivation showed a synchronous movement of the oral commissure
when smiling. In those patients, that did not show activation of the masseter muscle
upon smiling 0% showed synchronicity. The preoperative coactivation of the masseter
muscle is able to predict the outcome regarding synchronicity of the smile with a
sensitivity of 99.7%, a specificity of 88.5% and 92.5% positive predictive value and
99.6% negative predictive value (p < 0.001 for all).
Conclusions
The lack of masseter co-activation with smile predicts a lack of spontaneous involuntary
smile after dynamic smile reconstruction using the masseteric nerve.
Keywords
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Article info
Publication history
Published online: November 22, 2018
Accepted:
November 11,
2018
Received in revised form:
November 5,
2018
Received:
May 9,
2018
Footnotes
✰Parts of this article have been presented at the following meetings:
1. 14.-17.01.2017 American Society of Reconstructive Microsurgery in Hawaii.
2. 19.-22.11.2016 Mayo-Chang-Gung Symposium in Munich.
3. 14.-17.06.2017 World Society of Reconstructive Microsurgery meeting in Seoul.
Identification
Copyright
© 2018 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
