The frontal nerve is the largest branch of the ophthalmic division of the fifth cranial nerve. The ophthalmic nerve is responsible for conveying sensory information from the skin of the upper eyelids, forehead, and sides of the nose. It is formed by the union of the lacrimal, nasociliary, and frontal nerves.

The frontal nerve splits into the supratrochlear and supraorbital nerves. The supratrochlear nerve conveys information from the medial portion of the upper eyelid, medial forehead, and bridge of the nose. The supraorbital nerve relays information from the forehead, upper eyelid, and scalp.