# The Tragus-Facial Angle: Proposition of a New Method to Estimate the Trajectory of the Frontal Branch of the Facial Nerve

## TL;DR

This paper introduces a new method to estimate the facial nerve's trajectory using the tragus-facial angle, which could help reduce surgical risks.

## Contribution

A novel, simple method for estimating the frontal branch of the facial nerve using the tragus-facial angle is proposed.

## Key findings

- The mean tragus-facial angle was 33.5° with acceptable variability.
- The method showed no significant differences compared to Pitanguy’s line, confirming its accuracy.
- The frontal branch trajectory was found to be ~2.5 cm below the tragus at a ~30° angle.

## Abstract

Introduction

Pterional craniotomy is a cornerstone of skull base surgery; however, extended approaches such as orbitozygomatic craniotomies require wider dissections, which increase the risk of injury to the frontal branch (FB) of the facial nerve. Several methods of varying complexity have been proposed to estimate the nerve’s trajectory, but no consensus has been established. This study aims to describe a new, straightforward method for estimating the FB position.

Methods

Cadaveric heads were dissected from the stylomastoid foramen to the distal part of the FB. The anterior edge of the tragus was set as the starting point A, point B was the vertical intersection with the facial nerve, and point C was the horizontal intersection with the FB. The angle between AB and BC was defined as the tragus-facial angle (TFA). Validation was performed against Pitanguy’s line using deviations between estimation methods and FB location.

Results

Eleven sides were dissected. The mean tragus-facial angle was 33.5° (range: 26.6°-37.7°). Key anatomical measurements included an average AB distance of 26.8 mm (SD ± 2.7), BC distance of 30.5 mm, AC distance of 16.9 mm, and A′-NF distance of 11.4 mm. The frontal branch trajectory followed the BC line, positioned approximately 2.5 cm below the tragus at an angle of ~30° to the vertical. Validation against Pitanguy’s classic line demonstrated no statistically significant differences across multiple measurement points (all p > 0.24), supporting the accuracy and reproducibility of the proposed method.

Conclusion

The tragus-facial angle method displayed acceptable variability and represents a simple alternative for estimating the position of the FB of the facial nerve during anterolateral approaches.