Microanatomy of the Temporal Division of the Facial Nerve in the Periorbital Region Applied to Minimally Invasive Keyhole Approaches

Background: Minimally invasive keyhole approaches (MIKA) to the anterior skull base and circle of Willis require small incisions near distal branches of the temporal division (TD) of the facial nerve. Few studies have focused on planning the incision to avoid the TD branches and maximize exposure in these approaches.

Objective: This article aims to define a safe zone away from the TD branches for skin incision during MIKA using reliable and practical skin landmarks.

Methods: In five cadaveric heads (10 sides) a Cartesian system was established with the orbitomeatal line (OML) connecting the lateral canthus and the external acoustic meatus (x-axis). A perpendicular line was drawn to the x-axis at the lateral canthus (y-axis). TD branches were dissected proximally to distally until the nerve–muscle junction of the orbicularis oculi (OO) and fronto-occipitalis (FO) muscles. Nerve-muscle junction points were registered in the Cartesian system. Probabilistic heat maps were generated to define a periorbital safe zone.

Results: A median of 3 and 3 branches innervated the OO, and FO, respectively. A semicircular area centered on the lateral canthus with a radius of 10 mm was found to have low (<10%) chance of containing a TD branch. This safe zone could be extended posteriorly to 15 mm inferior to the OML ([Figs. 1]–[2]).

Conclusion: Identifying a safe zone for preserving TD branches is crucial for surgical incisions planned in the superolateral region of the orbit. Our study provides a clinically applicable and reproducible landmark for planning incisions commonly used during MIKA.

Fig. 1 Cadaveric dissection of facial nerve in the superolateral periorbital region and depiction of the Cartesian coordinate system created based on the lateral canthus and tip of the tragus. Small arrows point to the subgaleal facial nerve branches of the TD.

Fig. 2 Magnified view of facial nerve dissection near the OO and FO muscles (small black arrows).

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
07 February 2025