A Simple Clinical Application for Locating the Frontotemporal Branch of the Facial Nerve Using the Zygomatic Arch and the Tragus.

Background: The seventh cranial nerve (CN VII), also known as the facial nerve, is an anatomically intricate structure the branches of which serve several physiologic functions. CN VII innervates the muscles of facial expression which are crucial for eye protection, oral competence, and social interaction. The temporal branch, clinically referred to as the frontotemporal branch (FTB), is the most superior of the 5 branches and is at risk during cutaneous surgery of the parotid gland and in the temporal region. Several methods for delineating the FTB trajectory exist, the most widely known being Pitanguy's Line, which is defined as running from 0.5 cm below the tragus to 1.5 cm above the lateral eyebrow. However, variations in eyebrow location, often affected by modern-day cosmetic trends, complicate the accuracy of this approach.

Objectives: The aim of this study was to develop a surgical landmark to identify FTB location without relying on soft tissue structures.

Methods: To minimize variation, we chose landmarks that were both consistent and easy to locate based on simple surface anatomy. Twenty-one cadaver hemifaces were dissected in order to locate the FTB in relation to the inferior border of the zygomatic arch and the apex of the tragus.

Results: We found that the mean ± SEM distance from the apex of the tragus to the point where the FTB crossed the inferior border of the zygomatic arch was 3.21 ± 0.05 cm.

Conclusions: Through the use of this measurement, we aim to avoid the pitfalls of previous techniques by providing a widely applicable clinical tool based on landmarks easily found on any patient.