The Deep Temporal Nerve Transfer: An Anatomical Feasibility Study and Implications for Upper Facial Reanimation

Background: Facial paralysis has a profound impact on the brow, and currently static procedures are the mainstay of treatment. The deep temporal branches of the trigeminal nerve, given their proximity to the brow, may serve as possible donor nerves for both potential innervation of a free muscle transfer in patients with prolonged facial palsy or nerve transfers in acute or subacute palsy. As such, the authors present the detailed surgical anatomy of the deep temporal nerve, assessing feasibility for both functional muscle and nerve transfers, including a proposed surgical technique. Methods: Thirty cadaver hemifaces were dissected to establish deep temporal nerve anatomy and perform axonal analysis. Results: Two (53 percent) or three (47 percent) divisions of the deep temporal nerve were noted, with the most consistent division being the middle division (30 of 30 specimens). This division was consistently found approximately 4.1 cm (range, 3.7 to 4.5 cm) anterior to the tragus at the level of the zygomatic arch. For each 1 cm cranial to the arch, the nerve courses approximately 1 mm posteriorly. The number of axons in the proposed temporal branch is 1469 as it emerges from behind the zygomatic arch, 889 at 1 cm, 682 at 2 cm, 534 at 3 cm, 355 at 4 cm, 377 at 5 cm, and 256 at 6 cm. Conclusion: Given its anatomical consistency, and expendability, the middle division of the deep temporal nerve is a viable donor nerve for dynamic upper facial reanimation with either nerve transfer or functional muscle transfer, depending on the length of facial palsy.