Answer:
The frontal branch of the facial nerve leaves the parotid gland immediately caudad to the zygomatic arch. As it crosses the superficial surface of the arch, the frontal branch courses within the temporoparietal fascia (superficial temporal fascia) and travels along the undersurface of this fascial layer across the temporal region. The frontal bracnh enters the frontalis muscle above the level of the superior orbital rim.
The frontal branch of the facial nerve travels in a constant plane along the undersurface of the temporoparietal fascia and is quite superficial as it crosses the zygomatic arch. The deep temporal fascia and superficial temporal fat pad are anatomically important structures which adjoin the periosteum of the zygomatic arch and lie deep to the frontal nerve.
The superficial layer of the deep temporal fascia inserts along the superficial surface of the arch. The deep layer of the deep temporal fascia inserts along the deep surface of the arch. The superficial temporal fat pad adjoins the superior surface of the arch. The recommended path of dissection to the arch is within the subaponeurotic plane until approximately 2 cm above the arch. The dissection then deepens to penetrate the superficial layer of the deep temporal fascia, dissecting within the fat pad inferiorly to the arch periosteum.
On the face, the path of the frontal branch can be approximated by a line connecting the lateral edge of the eyebrow to the lower edge of the earlobe.