Topographic and histomorphometric analysis of the stylohyoid nerve: A novel donor candidate for facial reanimation

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Abstract

BACKGROUND: The stylohyoid nerve (SN) is a potential supplementary donor nerve for cross-facial nerve grafting (CFNG), particularly when it is harvested from the unaffected hemiface to augment motor axonal input while preserving major facial expression branches. Despite its potential, the anatomical course and axonal load of the SN have not been thoroughly investigated in the context of facial reanimation. We aimed to delineate the macroscopic and microscopic anatomical features of the SN and evaluate its anatomical feasibility as a donor nerve. METHODS: Sixteen hemifaces from 8 fresh-frozen adult human cadavers were dissected. The anatomical course of the SN was delineated and measured. Nerve specimens were subsequently harvested from the SN and zygomatic branch of the facial nerve (ZN). The microscopic anatomy and myelinated axon count of the two nerves were compared using light microscopy. RESULTS: The mean branching distance of the SN was 7.13 ± 1.41 mm, with an average course length of 62.0 ± 7.70 mm. The mean myelinated axon count was 830.1 ± 163.7 for the SN and 836.6 ± 124.7 for the ZN, with no statistically significant difference (p = 0.90). Furthermore, light microscopic evaluation revealed that the histological architecture of both the nerves was highly comparable. CONCLUSION: The SN demonstrated a consistent anatomical course, sufficient mobilizable length, and a myelinated axon load comparable to those of the ZN. These findings establish anatomical feasibility and support further investigation of the SN as a supplementary donor source from the unaffected hemiface in CFNG procedures.

Abstract as published, via PubMed.