Anatomical Variation of Facial Nerve during Parotid Surgery

Lee, Hyung Seok; Cho, Seok Hyun; Lee, Seung Hwan; Tae, Kyung; Jeong, Jin Hyeok

Abstract

BACKGROUND AND OBJECTIVES
Although many approaches using various anatomic landmarks to identify the facial nerve trunk have been reported, each technique has its advantages and disadvantage. The author employed the tragal pointer as an anatomical landmark for identifying the facial nerve trunk. It had an advantage for ease use and safety, but influenced by the size, location of the tumor and adjacent tissue. The pattern of peripheral facial nerve branching is extremely variable in parotid gland. Davis et al. classified the peripheral pattern of the facial nerve by anastomoses pattern of the branches. The objectives of this study is to evaulate the usefullness of the tragal pionter as a landmark for identification of the facial nerve trunk, and anatomical variation of the facial nerve during patorid tumor surgery. MATERIALS AND METHOD: We analyzed the medical records retrospectively, 53 patients for whom parotid surgery due to parotid tumor were selected from 1989 to 1997.
RESULTS
1) Mean distance from the pointer to the facial nerve trunk and bifurcation were 12.3 mm and 13.5 mm respectively. 2) In atypical course of the retromandibular vein cases, the vein crosses facial nerve trunk medially and attaches to facial nerve branches. 3) The frequency of peripheral pattern of the facial nerve were type III (35.8%), type II (28.3%), type IV (15.1%), type I (9.4%), type V and others (5.7%) in order of frequency.
CONCLUSION
In most cases, the length of the facial nerve in deep lobe tumors of the parotid was shorter than that in superficial tumors. It located at more superficial portion than we expected, so we should pay more attention to it during parotid surgery. In type III pattern of peripheral branches of facial nerve, we should identify the anastomosis of buccal and zygomatic branches. Mandibular branch rarely had an anastomosis with the other facial nerve branches in its peripheral distribution.