Variations in Facial Nerve Branches and Anatomical Landmarks for Its Trunk Identification: A Pilot Cadaveric Study in the Lithuanian Population.

Dominykas Stankevicius,Andrej Suchomlinov

doi:10.7759/cureus.6100

Abstract

ObjectiveThe purpose of this study was to evaluate facial nerve (FN) branching variations based on Davis and Kopuz classifications in the Lithuanian population and measure the shortest distance from the facial nerve trunk (FNT) to its anatomical landmarks.MethodsTwenty-two hemifaces of 11 cadavers were dissected. The preauricular skin cut was made and extended behind the ear lobe and along the inferior border of the mandible. The skin with subcutaneous tissue and superficial fascia were separated and medially retracted, and the parotid gland was dissected anterogradely. The FNT and its furcation type and branching pattern were disclosed and noted based on Davis and Kopuz classifications. Further, the shortest distance from the FNT to the anatomical landmarks of the tragal pointer (TP), the angle of mandible (AM), and the tip of mastoid process (TMP) was measured.ResultsThe prevalence of branching patterns did not differ significantly compared to Davis classification. Based on Kopuz, type IVA pattern was the most common in six cases (27%). Eighteen (82%) trunks split as bifurcations and two (9%) trifurcations, while two (9%) had separate double trunks. The shortest distance (mm) from the FNT to the TP is 9.30 ± 0.93, AM 36.45 ± 4.14, and TMP 12.52 ± 2.30.ConclusionThe prevalence of FN variations in the Lithuanian population is similar to Davis classification. The AM and TMP are consistent superficial bony landmarks for trunk identification, while the distance from the TP highly varies among studies. Surgeons should be aware of double FNT during parotidectomy, which is described in Kopuz classification.

Highlights

The facial nerve (FN) is the VII th cranial nerve that controls mimic muscles and is responsible for facial expression
Eighteen (82%) trunks split as bifurcations and two (9%) trifurcations, while two (9%) had separate double trunks
The trunk of FN emerges from stylomastoid foramen and passes through the parotid gland, and it usually bifurcates into upper and lower divisions, both of which further give rise to five terminal branches: temporal, zygomatic, buccal, marginal mandibular, and cervical

Summary

Introduction

The facial nerve (FN) is the VII th cranial nerve that controls mimic muscles and is responsible for facial expression. The branching of FN was first described by Davis and colleagues in 1956 [1] They outlined six FN types (I, II, III, IV, V, and VI) with their recurrence, based on the presence or absence of the anastomoses between terminal branches. A newer classification was released in 1987 by Katz and Catalano, which did not fit Davis classification [2] It had nine types of branching patterns (IA, IB, II, IIIA, IIIB, IIIC, IVA, IVB, and V) and was based on anastomoses between terminal branches, the origin of the buccal branch, and the number of FNTs. The improved version with three additional “double-trunk” types (VA, VB, VC) was released in 1994 by Kopuz et al [3]

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Discussion

Conclusion