Defining a Preauricular Safe Zone: A Cadaveric Study of the Frontotemporal Branch of the Facial Nerve.

Background: In the preauricular region, the frontotemporal branch of the facial nerve is vulnerable to injury, which can result in facial palsy and poor cosmesis after surgical interventions.

Objectives: The purpose of this study was to describe variations in the branching patterns of the frontotemporal branch of the facial nerve and the relation between this branch and the surrounding anatomic landmarks. Based on our findings, we propose a Danger Zone and Safe Zones for preauricular interventions to avoid frontal branch injury.

Methods: Twenty cadaveric half-heads, 10 freshly frozen and 10 embalmed, were dissected. The anatomy of the auriculotemporal nerve, facial nerve, and variations of its branching pattern in the preauricular region were investigated.

Results: The mean [standard deviation] number of frontotemporal branches crossing the zygomatic arch was 2.05 [0.6]. Beginning from the X point at the apex of the intertragal notch, frontal branches ran over the zygomatic arch at a distance extending from 10 to 31 mm anterior to the tragus, which can be defined as the Danger Zone for frontal branches. Safe Zones A and B are triangular regions located behind and in front of the Danger Zone, respectively.

Conclusions: Mapping of these Safety and Danger Zones is a reliable and simple approach in preauricular interventions to avoid frontal branch injury because the facial nerve typically has multiple frontal branches. This approach provides practical information for surgeons rather than estimating the trajectory of a single frontal branch from Pitanuy's line.