Frontal nerve is the largest branch of the ophthalmic division of the trigeminal nerve. It provides sensory innervation to the skin of the forehead, mucosa of the frontal sinus and skin of upper eyelid.
The frontal nerve enters the orbit through the upper part of the superior orbital fissure. It then passes forward between the levator palpebrae superioris muscle and the periosteum of the roof of the orbit.
Midway between the apex and the base of the orbital cavity, the frontal nerve divides into two branches; supratrochlear nerve and supraorbital nerve.
These branches wind around the upper margin of the orbital cavity to supply the skin of the forehead. The supraorbital nerve also supplies the mucous membrane of the frontal air sinus.
As is evident from the previous discussion, the frontal nerve performs the following functions via its two branches:
- Provides sensory innervation for the skin of the forehead
- Provides sensory innervation for the mucosa of frontal air sinus
- Provides sensory innervation for the skin of the upper eyelid via general somatic afferent fibers