Introduction

The facial nerve, which is the seventh cranial nerve, is at risk during facial plastic, reconstructive, and parotid surgeries. It has six segments: intracranial, meatal, labyrinthine, tympanic, mastoid and extratemporal. The extratemporal frees up the posterior auricular nerve and then innervates facial muscles through its terminal branches and is responsible for facial expression. The trunk of the facial nerve, which emerges from stylomastoid foramen, runs for 1 cm and then enters the posteromedial surface of the parotid gland, where it usually bifurcates into upper temporofacial and lower cervicofacial divisions. Both divisions give rise to five terminal branches: temporal, zygomatic, buccal, marginal mandibular, and cervical,¹ which are frequently encountered during procedures such as parotidectomy, rhytidectomy, facial reconstruction, and cosmetic surgery.

Preserving these branches is essential to avoid postoperative facial paralysis and functional deficits. The branching of FN was first described by Davis et al, who described six types of facial nerve branching patterns (I, II, III, IV, V, and VI) based on the presence or absence of communications between its divisions and terminal branches.² Another classification was described by Katz et al, with nine types of branching patterns (IA, IB, II, IIIA, IIIB, IIIC, IVA, IVB, and V) based on the number of trunks of facial nerve, the origin of the buccal branch, and communications between terminal branches.³ A new classification with three additional “double-trunk” types (VA, VB, and VC) was proposed by Kopuz et al.⁴ Several anatomical landmarks commonly used in plastic and head-and-neck surgery—including the stylomastoid foramen, posterior belly of the digastric muscle, tragal pointer, tympanomastoid suture, and retromandibular vein—serve as guides for identifying the facial nerve trunk intraoperatively. However, anatomical variations in branching patterns and interbranch communications increase the complexity of surgical dissection.

Methods

During routine educational dissections conducted between 2016 and 2022 in the Department of Anatomy, the extratemporal segment of the facial nerve was examined in 50 sides from 25 adult cadavers of both sexes (M: 21; F: 4). All cadavers had been embalmed using a 10% formaldehyde solution.

A preauricular surgical incision was employed, extending posteriorly behind the ear lobe over the mastoid process and inferiorly along the mandibular border, simulating operative exposure used in parotid and facial surgeries. The skin, subcutaneous tissue, and superficial fascia were carefully reflected to expose the parotid gland. The main trunk of the facial nerve was identified at the stylomastoid foramen using deep anatomical landmarks and traced through the gland to its terminal branching pattern.

The facial nerve trunk was followed meticulously along its intraparotid course, and its terminal branches were dissected and documented. All findings were recorded and photographed.

The study protocol included assessment of:

Results

Terminal Branches of Facial Nerve and Its Communications

The five branches—namely the temporal, zygomatic, buccal, marginal mandibular, and cervical—arose from the two divisions of the facial nerve in all sides. The temporal and zygomatic branches originated from the temporofacial division and marginal mandibular and cervical branches originated from the cervicofacial division in all specimens. The buccal branch of facial nerve arose from both divisions in 20 sides (►Fig. 1).

Communications of facial nerve were classified according to Davis et al:²

Fig. 1 - Buccal branch arising from two divisions of facial nerve.

Fig. 1 - Buccal branch arising from two divisions of facial nerve.

Type I: In seven sides (14%), there was no major communication between the divisions and branches of facial nerve (►Fig. 2).

Fig. 2 - Type I branching pattern of Davis et al.


Fig. 2 - Type I branching pattern of Davis et al.

Type II: In nine sides (18%), communications between the branches of temporofacial divisions were observed (►Fig. 3).

Fig. 3 - Type II branching pattern of Davis et al.


Fig. 3 - Type II branching pattern of Davis et al.

Type III: In 14 sides (28%), a single communication between the temporofacial and cervicofacial divisions was observed (►Fig. 4).

Fig. 4 - Type III branching pattern of Davis et al.


Fig. 4 - Type III branching pattern of Davis et al.

Type IV: In 12 sides (24%), a single communication between the temporofacial and cervicofacial divisions and communications among the temporofacial branches were observed (►Fig. 5).

Fig. 5 - Type IV branching pattern of Davis et al.


Fig. 5 - Type IV branching pattern of Davis et al.

Type V: In four sides (8%), double communications between the temporofacial and cervicofacial divisions were observed.

Type VI: In four sides (8%), complex communications between the branches of facial nerve were observed (►Fig. 6).

Fig. 6 - Type VI branching pattern of Davis et al.


Fig. 6 - Type VI branching pattern of Davis et al.

Discussion

A single facial nerve trunk exiting through the stylomastoid foramen has been described in the standard textbooks and in the previous literature.², ⁵ Some authors have described that two facial nerve trunks exit from the stylomastoid foramen.⁶, ⁷ The presence of a single facial nerve trunk emerging from the stylomastoid foramen corresponds with classical anatomical descriptions and is consistent with previous studies. However, reports of multiple trunks emphasize the importance of cautious identification during surgical exposure. The mean distance between the emerging point of the facial nerve trunk from the stylomastoid foramen and its bifurcation point was 14.38 ± 3.04 mm according to Pascual et al.⁸ The measured trunk length in this study provides practical guidance for surgeons during deep parotid dissection, as excessive traction or blind dissection within this short segment increases the risk of nerve injury. Touré and Vacher classified the connection of the facial nerve to retromandibular vein in the parotid gland into six types, the most common type being that in which the facial nerve is lateral to retromandibular vein in 65.2% (Type I) of cases and medial to vein in 28% (Type II) of cases.⁹

Cruveilhier early on described six terminal branches, and Hovelacque later described eight terminal branches of facial nerve.¹⁰, ¹¹ Davis et al simplified these earlier classifications of terminal branches of facial nerve and described five terminal branches of the facial nerve.²

Earlier classifications of communications among terminal branches of facial nerve were proposed by McCormack et al, Dargent and Duroux, and Pons-Tortella.¹², ¹³, ¹⁴ Then, Davis et al in 1956 described a six-type classification based on the connections between the terminal branches.²

Katz and Catalano proposed a new classification of communications based on the origin of buccal nerve and the number of trunks of the facial nerve.³ Anewer classification of communications of facial nerve into 12 types has been described by Pascual et al.⁸ It is well known that connections are more commonly found in the temporofacial division than in the cervicofacial division.², ¹⁴ The observed communication patterns between branches highlight the complexity of intraparotid facial nerve anatomy. Such plexiform arrangements can obscure clear branch identification and increase the likelihood of inadvertent injury during facial lifting, parotidectomy, and reconstructive procedures.

Conclusion

Several variations in the branching pattern of facial nerve may increase the probability of a facial palsy after surgery if the surgeon is not aware of these anatomical variations.¹⁵ Variations in extratemporal facial nerve branching patterns and intraparotid communications significantly influence surgical safety. Detailed knowledge of these anatomical relationships and operative landmarks is essential to minimize postoperative facial nerve palsy during facial plastic surgery, parotid surgery, and reconstructive interventions.