Supratrochlear nerve is the smaller of the two terminal branches of the frontal nerve, the other being supraorbital nerve.
After its origin from the frontal nerve midway between the apex and the base of the orbital cavity, the supratrochlear nerve passes above the pulley of the superior oblique muscle. Here it gives off a descending filament that joins the infratrochlear nerve (a branch of the nasociliary nerve).
Afterwards, the supraorbital nerve exits the orbit between the pulley of the superior oblique muscle and the supraorbital foramen. It then curves up onto the forehead and ascends beneath the frontalis muscle and the corrugator supercilii muscle.
The nerve then divides into branches that pierce the muscles and supply the skin of the lower part of the forehead.
The supratrochlear nerve innervates the following structures:
- Skin of the lower part of the forehead, close to the midline
- Conjunctiva of the eye
- Skin of the upper eyelid