Topographic Anatomy of the Facial Nerve Innervating the Muscles in Glabellar Area

Choi, Hyuk Gyoo; Jin, Sheng; Hwang, Kun; Kim, Yu Jin

Abstract

The aim of this study is to identify the branches of the facial nerve to the corrugator supercilii muscle(CSM), upper orbicularis oculi muscle(OOM) and procerus muscle(PM), and to elucidate the relation between the course of facial nerve and the superficial landmark of face. Furthermore, this study is also aimed to present anatomical information which is attributed to the treatment of the glabellar frowning wrinkles using selective neurectomy. Cadaver dissection was done on 19 hemifaces to investigate the distribution of the temporal branch of the facial nerve and its entering into the CSM. Twenty hemifaces of cadavers were dissected to investigate the pattern of the temporal branch of the facial nerve to the upper OOM, and the course of facial nerve into the OOM at three different sagittal/vertical planes through the lateral canthus, midpalpebral fissure, and medial canthus, respectively. Twenty-three hemifaces of cadavers were dissected for the investigation of nerve innervation to PM, and identification of the main trunk of the facial nerve and the buccal branches to the nasal bridge. A crossing point between buccal branch and the intercanthal line, and the entering point of the buccal branch into the PM were measured. 1. The temporal branch of the facial nerve contained 2 to 4 smaller branches on the zygomatic arch, and they were furtherly divided into 4 to 7 thin rami at the position 2.8 to 25 mm above the point 10mm lateral to the supraorbital notch. A plexus mainly from the inferior ramus, partially from the middle ramus entered into the CSM in the supraorbital area. 2. The ramifying point of the temporal branch was continued to the circular hazardous zone with a 10mm diameter, and its center was 7.5cm away from the lateral canthus at angle of minus 15 degrees. The highest level of the those rami that entered OOM on the X-axis and Y-axis from lateral canthus was +2.51+/-0.23cm, +2.70+/-0.35cm, and the lowest was +2.68+/-0.32cm, 0cm, respectively. The uppermost ramus on the Y-axis from lateral canthus, midpalpebral fissure, and medial canthus was +3.47 +/-0.27cm, +3.49+/-0.45cm, and +2.97+/-0.35cm, and the lowest ramus was +1.62+/-0.12cm, +1.82+/-0.17cm, and +1.63+/-0.22 cm, respectively. 3.The PM was innervated by the buccal branch of the facial nerve, which coursed infraorbitally. The buccal branch crossed the intercanthal line(nasion to the medial canthus) at approximately lateral one third. The nerve entrance was within a circle with a diameter of 5mm and the location of its center was 9.1mm lateral and 10.4mm superior from nasion. The present study shows the identification of nerve innervation to CSM, OOM and PM, and the relation between the course of facial nerve and the superficial landmark of face. We elucidated especially the course and entering point of buccal branch of the facial nerve to procerus muscle for the first time. We confirm that selective cutting of buccal branch of the facial nerve is essential to the treatment of the glabellar frowning lines. Furthermore, the anatomic knowledge from this study might be contributive to improve the efficacy of selective neurectomy and minimize the injury of facial nerve during surgical procedure of the face.