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A Reliable Approach for Massteric Nerve Dissection in the Setting of Facial Reanimation
Angela Cheng, MD; Thorir Audolfsson, MD; Andres Rodriguez, MD, PhD; Corrine Wong, MD; Shai Rozen, MD
University of Texas Southwestern Medical Center, Dallas, TX, USA
Introduction: The masseteric nerve remains a reliable and viable option during single-stage facial reanimation procedures in the appropriately selected patients. However, surgeons can be frustrated by difficulty locating the nerve intraoperatively due to a variety of described branching patterns and surgical approaches. More so, several studies including our own, present differing measurements in relation to the tragus and zygomatic arch rendering them occasionally less reliable in exact localization of the nerve. Based on our experience in 20 clinical cases and these 20 hemi-facial cadaveric dissections we suggest a technique relying on constant anatomical landmarks regardless of absolute measurements and describe a safe harvest technique.
Methods: Bilateral dissections of 10 fresh cadaveric specimens were performed in a similar technique we implement intraoperatively relying on an anatomical area defined by the condyle, coronoid process, zygmoatic arch, and mandibular notch dissecting through the parotid gland while preserving facial nerve branches. After localization of the masseteric nerve, measurements were taken in relation to the zygomatic arch and tragus for comparison to findings of other studies. Nerve diameter and maximal length were also measured.
Results: The masseteric nerve can be consistently found while dissecting a 1.0-1.5 cm2 area located in the center of a triangular zone defined by the borders of the coronoid process, condyle, and zygomatic arch with the mandibular notch as the caudal apex. Once identified, measurements found the masseteric nerve branch 12.22±3.68 mm caudal to the zygomatic arch and 22.9±2.61 mm anterior to the tragus further demonstrating inconsistent measurement among different studies. The average nerve diameter was 1.63±0.63 mm and the maximal length was 13.78±2.31mm.
Conclusions: Localizing the branch of the nerve to the masseter, where comfortable coaptation can be performed, can be achieved reliably when dissecting in the center of a triangular area defined by constant anatomical landmarks that include the coronoid process, mandibular notch, condyle, and zygomatic arch. We find this technique more consistent and reliable than measurements from the tragus and zygomatic arch, which may vary among different individuals.
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