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Facial Nerve Axonal Analysis and Anatomical Localization in Donor Nerve: Optimizing Axonal Load for Cross-Facial Nerve Grafting in Facial Reanimation

Hembd, Austin M.D.; Nagarkar, Purushottam A. M.D.; Saba, Salim M.D.; Wan, Dinah M.D; Kutz, J. Walter M.D.; Isaacson, Brandon M.D.; Gupta, Sachin M.D.; White, Charles L. III M.D.; Rohrich, Rod J. M.D.; Rozen, Shai M. M.D.

Plastic and Reconstructive Surgery: January 2017 - Volume 139 - Issue 1 - p 177-183
doi: 10.1097/PRS.0000000000002897
Reconstructive: Head and Neck: Original Articles
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Background: Donor nerve axonal count over 900 in two-stage reconstructions using cross-facial nerve grafts is possibly associated with improved outcomes in facial reanimation. Facial nerve axonal analysis was performed to determine the ideal location for optimizing axonal load. Correlation of axonal number, branch diameter, and age was also assessed.

Methods: Twenty-eight fresh unpreserved cadaveric hemifaces were dissected exposing the extracranial facial nerve branches. Axonal counts at 2-cm intervals from the pes anserinus along branches inserting into the zygomaticus major muscle were taken, noting position relative to the zygomatic arch, posterior ramus border, lateral border of the zygomaticus muscle, and anterior parotid gland border. Nerves were fixed, sectioned, and stained with SMI-31 antineurofilament stain for digital axonal analysis.

Results: All specimens had one or more intraparotid zygomatic branches with over 900 axons, and 96 percent had an extraparotid branch with over 900 axons. The likelihood that a zygomatic branch would have over 900 axons at its last intraparotid point (mean, 6 mm posterior to the parotid border) was 92 percent (range, 67 to 100 percent) in contrast to 61 percent (range, 25 to 100 percent) when sampled at the first extraparotid point (mean, 14 mm anterior to the parotid border). Nerve cross-sectional area was positively correlated to its axonal count (R° = 78 percent; p < 0.0001), with nerve diameter over 0.6 mm predicting over 900 axons. Age did not correlate with axonal counts.

Conclusions: Branches with adequate axonal load were found in all specimens. The likelihood of adequate branch selection improved from 61 percent to 92 percent with short retrograde intraparotid dissection. Nerve diameter correlated with axonal load.

Dallas, Texas; Beirut, Lebanon; and Bethesda, Md.

From the Department of Plastic Surgery, Department of Otolaryngology, and Department of Pathology, Division of Neuropathology, University of Texas Southwestern Medical Center; the Division of Plastic and Reconstructive Surgery, American University of Beirut; and Otology/Neurotology, Walter Reed National Military Medical Center.

Received for publication January 5, 2016; accepted August 15, 2016.

Presented at the 95th Annual Meeting of the American Association of Plastic Surgeons, in New York, New York, May 19 through 22, 2016.

Disclosure:The authors have no financial interests in this research project or in any of the techniques or equipment used in this study.

Shai Rozen, M.D., Department of Plastic Surgery, University of Texas Southwestern Medical Center, 1800 Inwood Road, Dallas, Texas 75390, shai.rozen@utsouthwestern.edu

Copyright © 2016 by the American Society of Plastic Surgeons