Microanatomic study on musculus zygomaticus innervated by zygomatic branch of facial nerve

Objective To indentify the positions and surface marks of the terminal branches of zygomatic branch of facial nerve entering the musculus zygomaticus. Methods The path and branches of the zygomatic branch of facial nerve were dissected from 10 (20 sides) cadaveric head specimen which had been fixed by 10% formalin. Regarding the horizontal line through labial commissure as X axis, the vertical line through lateral canthus at the same side as Y axis, the two axises were used to establish the anatomic relationship between the musculus zygomaticus and the zygomatic branch of facial nerve. Results Zygomatic branch of facial nerve come out of the parotid from its anterior superior edge was divided into 1-3 branches and most of them were two branches (rated 65%, 13 sides). Orbicularis oculi muscle was innervated by the superfical branch ramus superfacialis which passed through the surface of head side of major zygomatic muscle; the ramus profundus which entered the major zygomatic muscle through its deep plate in the upper half part was divided into 2～6 branches, (average 3.40±1.06) innervating the muscle like segmented claw. The number of nerve branches entering the muscle was 3～8 (average 6.00±1.49). Conclusion In the midface surgical operations, it is safe to undermine on 2/3 depth below the major zygomatic muscle and for avoiding injuring the zygomatic branch of facial nerve, it is necessary to avoid undermining below the zygomatic plane, especially on the 1/2 depth; while undermining on 1/2 depth below major zygomatic muscle, it is good to operate through deep plane of this muscle to avoid injuing the buccal branch of facial nerve.