Abstract
Objectives:
Describe extraparotid course of the facial nerve via microsurgical dissection. Analyze branch distribution and endpoint muscle innervation.
Methods:
Ten cadaveric hemifaces dissected under surgical microscopes. Facial nerve was identified from stylomastoid foramen to muscle. MAS measured number, length, and width at border of parotid, at level of the pes anserinus, and muscle border (frontalis, orbicularis oculi, zygomaticus major, and depressor anguli muscles). Analysis of variance and Student T test were performed.
Results:
At parotid border, zygomatic and buccal branches branched more often than temporal or marginal mandibular branches (2.7 +1.0, 2.9 + 0.7 vs 1.8 +1.2, 2.1 +0.9 mm respectively; p=0.06), branch diameter (1.1+0.3, 1.0+0.5 vs 0.9+0.3, 0.9+0.3 mm respectively p=0.238). At muscle border, similar results were found for zygomatic and buccal branches compared to temporal or marginal mandibular branches (2.3+1.3, 3.1+1.0 vs 1.3+0.5,1.3+0.5mm; P = 0.001), diameter (0.9+0.4, 1.0+0.4 vs 0.8+0.3, 0.7+0.3mm; p=0.737). Zygomaticotemporal pes showed more branching and greater diameter compared to cervicofacial, (7.6+2.2 vs 2.6+0.5mm; P =.0001) and (2.5+0.9 vs 1.9+0.4mm; p=0.10) respectively. Branch length from pes to muscle was consistent, the longest being temporal, zygomatic, marginal mandibular, and buccal (9.6 + 1.2, 8.3 +1.4, 8.0 +1.3, 7.4 +0.9 cm respectively; p=0.007). Anastomosis between temporal/zygomatic and zygomatic/buccal branches were found more consistently across all specimens than buccal/marginal mandibular anastomosis.
Conclusions:
Consistently fewer branches of the marginal mandibular branch at parotid border and at muscle border, and fewer anastomoses, may be the reasons for increased morbidity from surgical injury. Histologic analysis will further elucidate the number of innervations to the muscles of facial function.
Get full access to this article
View all access options for this article.