A new landmark for the identification of the facial nerve during parotid surgery: A cadaver study

Khalid Hussain Al-Qahtani, Fahad Mohammad AlQahtani, Mahmoud Mohammad Muqat, Mubarak Shaie AlQahtani, Ali M Al-Qannass, Tahera Islam, Jabir Alharbi, Haneen Sebaih, Mohammad Alqarni, Hadi Hakami, Khalid Hussain Al-Qahtani, Fahad Mohammad AlQahtani, Mahmoud Mohammad Muqat, Mubarak Shaie AlQahtani, Ali M Al-Qannass, Tahera Islam, Jabir Alharbi, Haneen Sebaih, Mohammad Alqarni, Hadi Hakami

Abstract

Objective: Precise knowledge of facial nerve anatomy is crucial for parotid surgery. Although several surgical landmarks to identify the facial nerve have been described in literature, their position is variable, inconsistent, and difficult to follow in some cases. The purpose of this study was to prove that the facial nerve trunk (FNT) is located midway between the mastoid tip (MT) and osteocartilaginous junction of the external auditory canal (EAC).

Methods: A prospective study of 7 frozen cadaver specimens, of which 13 facial sides were dissected. The distances between the osteocartilaginous junction and the MT, between the FNT and the MT, and between the FNT and the osteocartilaginous junction were recorded, respectively.

Results: The distance between the osteocartilaginous junction and the MT ranged from 17 to 21 mm, with a mean of 19.5 mm (SD = ±1.19). The mean distances between the osteocartilaginous junction and the FNT and between the MT and the FNT were 9.2 mm (±1.58) and 10.3 mm (±1.79), respectively.

Conclusion: The FNT was consistently located close to the midpoint between mastoid tip inferiorly and bony-cartilaginous junction of the EAC superiorly.

Level of evidence: NA.

Keywords: anatomy; facial nerve; landmark; parotidectomy.

Conflict of interest statement

The authors declare that no potential conflict of interest.

© 2020 The Authors. Laryngoscope Investigative Otolaryngology published by Wiley Periodicals LLC. on behalf of The Triological Society.

Figures

FIGURE 1
FIGURE 1
Right lateral view of a cadaver showing the facial nerve trunk (FNT) and some of its landmarks. TP, tragal pointer; MT, mastoid tip (blue arrow); PBDM, posterior belly of the digastric muscle. The black dotted line represents mastoid process. The green line represents the osteocartilagenous junction (OCJ) of the EAC. The red line represents the tympanomastoid suture. The white line represents an imaginary line drawn between the OCJ and MT. The yellow line borders the fatty tissue bellow mastoid process that was not dissected
FIGURE 2
FIGURE 2
Schematic representation of the landmarks for the identification of the facial nerve in a cadaver. A, mastoid tip; B, osteocartilaginous junction of the external auditory canal; C, facial nerve trunk; D, the external auditory canal (dashed line indicates its localization); E, posterior belly of the digastric muscle; F, tragal pointer
FIGURE 3
FIGURE 3
A three‐dimensional CT of the skull bones showing the facial nerve trunk (yellow, dashed line). The osteocartilaginous junction (OCJ) of the external auditory meatus (black curved line), the location of the tympano‐mastoid suture (red dashed line), and an imaginary line drawn from the mastoid tip (MT) to the OCJ (blue line)
FIGURE 4
FIGURE 4
The distance from the osteocartilaginous junction of the external auditory canal (EAC) to the mastoid tip of all cadavers. The black line represents the position of the facial nerve trunk (FNT)

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