The frontal nerve's primary function is to provide sensory innervation to specific areas of the forehead, upper eyelid, and scalp. It does not have any motor function.
Details of the Frontal Nerve's Sensory Function
The frontal nerve is a branch of the ophthalmic nerve (V1), which itself is the first branch of the trigeminal nerve (cranial nerve V). After branching from the ophthalmic nerve, the frontal nerve then divides into two terminal branches:
-
Supratrochlear Nerve: This branch travels medially and provides sensory innervation to the skin and conjunctiva of the medial portion of the upper eyelid, the skin of the forehead near the midline, and the scalp.
-
Supraorbital Nerve: This larger branch exits the orbit through the supraorbital notch (or foramen) and provides sensory innervation to the skin of the central forehead and the scalp as far back as the lambdoid suture. The supraorbital nerve can often be palpated just above the eye socket.
Summary
In summary, the frontal nerve is responsible for transmitting sensory information from the forehead, upper eyelid (primarily the medial portion via the supratrochlear nerve), and scalp back to the brain. It is a purely sensory nerve and does not control any muscle movement.
