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

Abstract

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, during various surgical interventions. Objectives The purpose of this study was to describe the variations in branching patterns of the frontotemporal branch and its relation to the surrounding anatomical 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 average number of frontotemporal branches crossing the zygomatic arch was 2.05 ± 0.6 (mean ± standard deviation). 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 the triangular regions located behind and in front of the Danger Zone, respectively. Conclusions The mapping of the triangular Safety and Danger Zones is a reliable and simple approach in preauricular interventions to avoid frontal branch injury as the facial nerve typically has multiple frontal branches. This approach provides practical information to surgeons rather than estimating the trajectory of a single frontal branch by using Pitanguy’s line.

A Novel Injection Technique to the Lateral Pterygoid Muscle for Temporomandibular Disorders: A Cadaveric Study

“…Our approach is an extraoral injection technique performed bimanually, with one hand palpating the maxillary tuberosity intraorally while the other performs the injection. The entry point of the needle (27 gauge × 50 mm) is within the preauricular safe zone 18 and located 10 mm anterior to the most anterior point of the tragus, with its tip pointed 5 mm posterior and 15 mm superior to the maxillary tuberosity. ( See Figure, Supplemental Digital Content 4 , which shows extraoral injection technique, http://links.lww.com/PRS/E654.)…”

Anatomical Relationship between the Inferior Temporal Septum and the Temporal Branch of the Facial Nerve for Clinical Applications

“…14 Furthermore, the anterior apex of the tragus (tragion) was chosen as a cartilaginous anatomical landmark with minimal variation and high versatility. 9,10 The ITS is a bilaminar structure consisting of crisscrossed fibers that reflect from the sDTF to the overlying superficial temporal fascia, caudal to the level of the division of the superficial and deep layers of the deep temporal fascia. 7,8 It has an oblique course along a line extending from the external acoustic meatus toward the frontotemporal region, and forms a fibrous strand 2 cm cranial to the zygomatic arch.…”

“…14 Furthermore, the anterior apex of the tragus (tragion) was chosen as a cartilaginous anatomical landmark with minimal variation and high versatility. 9,10…”

“…7,8 Despite the present knowledge of the temporal interfascial anatomy, facial nerve injury during surgical intervention is commonly reported. [9][10][11] We therefore aimed to determine the topographic structures and detailed anatomical relationships between the ITS and TBFN using gross dissections and microscopic observations for avoiding nerve injury during interfascial interventions on the temple.…”

Primary Neurorraphy of the Frontotemporal Branch of the Facial Nerve in Pediatric Patients

“…Surgery in the distal region becomes technically difficult because the nerve is thinner and, more importantly, as the frontotemporal nerve is divided into terminal branches coaptation cannot be achieved in a way that all segments of the muscle will be re-innervated. Kucukguven et al’s 35 cadaver study showed that the frontotemporal nerve is divided into 2 to 3 terminal branches at the level of lateral canthus. Similarly, in the present study the distal segment could not be detected in 2 of 6 patients with injuries medial to the lateral canthus.…”