The supraorbital and supratrochlear nerves arise from the frontal nerve and are 2 of the 5 branches of V1 (ophthalmic division of the trigeminal nerve). The supraorbital nerve is the largest branch. It exits the orbit through the supraorbital notch or foramen, usually within the medial third of the orbital roof (mean distance from exit to medial angle of the orbit: 20 mm (range: 5–47) 1)). The supratrochlear nerve exits the orbit without a foramen or notch 3–38 mm medial to the supraorbital nerve (mean: 15.3 mm 2)); the most medial branch varies from 8–30 mm lateral to the patient’s midline 3))
It is smaller than the nearby supraorbital nerve. It passes above the pulley of the Superior oblique muscle and gives off a descending filament that joins the infratrochlear branch of the nasociliary nerve.
The supratrochlear nerve then exits the orbit between the pulley of the superior oblique and the supraorbital foramen, curves up on to the forehead close to the bone, and ascends beneath the Corrugator supercilii and Frontalis muscles. It then divides into branches which pierce these muscles and supplies the following areas:
skin of the lower part of the forehead, close to the midline conjunctiva skin of the upper eyelid.