Periocular Facial Nerve Axonal Analysis and Anatomical Localization: Implications for Blink Reanimation

Cross-face nerve grafting is widely performed in smile reanimation, but its application in dynamic blink restoration is less well characterized.

To compare axon counts of the frontal, zygomatic, and periorbital branches of the facial nerve in human anatomical specimens to provide insight on their suitability in cross-face nerve grafting surgery.

Four human anatomical specimens (eight hemifaces) were dissected. Facial nerve specimens were processed for histological cross-sectional analysis using FluoroMyelin staining. Quantitative axon analysis was conducted using semiautomated dot annotation in opensource QuPath software. Axon counts were compared using one-way analysis of variance (ANOVA).

The study included four male human anatomical specimens with an average age of 71 years. Mean axon counts were 405.0 for the frontal branch, 367.4 for the zygomatic branch, and 285.8 for the orbicularis branch. Substantial variability was observed across specimens. ANOVA did not detect a difference in mean axon count (p = 0.0757). Lateral orbicularis oculi branches were identified in all hemifaces and commonly arose directly from the upper facial nerve trunk.

This study demonstrates that sampled frontal, zygomatic, and orbicularis oculi facial nerve branches had axon counts that were not detectably different in this human anatomical specimen cohort.