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.

The surgical approach for clipping anterior communicating artery Aneurysm

Anterior communicating artery (ACoA) aneurysm, accounts for 30%-35% of all the aneurysm making it one of the most common intracranial aneurysms. Although the Pterional approach is considered as the safe and appropriate method in ACoA aneurysm surgery, temporalis atrophy and injury to a frontal branch of the facial nerve are few inexorable complications. With the advancement of minimally invasive surgery several modified approaches, such as the supraorbital eyebrow incision approach, the minipterional approach, the mini-supraorbital approach, and the lateral supraorbital approach has been recently introduced and has been used as an alternative.

Bony Tunnel Formation Associated with the Distal Segment of the Frontal Branch of the Middle Meningeal Artery

The knowledge of certain anatomical variations is fundamental and any surgeon who operates without that knowledge may encounter difficulty during surgery. In this context, there is the middle meningeal artery (MMA) which also engenders considerable clinical interest due to its location. The MMA is predominantly periosteal, irrigating the bone and dura mater. It enters the floor of the middle cranial fossa through the foramen spinosum, travels laterally through a middle fossa bony ridge, and curves anteriorly over the upper-greater wing of the sphenoid where it divides into parietal and frontal branches at a variable point. Occasionally, the distal segment of the frontal branch may pass through a bony tunnel of variable size. To the best of our knowledge, there is no evidence in the current literature on the incidence of this rare bony tunnel. Therefore, we decided to investigate the incidence of this bony tunnel in 85 dry skulls of adults (both genders) belonging to the didactic collection of the Human Anatomy Laboratory of the Universidade de Santa Cruz do Sul, Brazil. All the skulls were examined bilaterally for the presence or absence of the bony tunnel associated with the distal segment of the frontal branch of the MMA. Of the 85 skulls analyzed, the bony tunnel was present on the right side in 1.18% and on the left side in 5.88% (p = 0.045). Thus, in the studied sample, there was a significant tendency for this bony tunnel to be formed on the left side.