The corrugator supercilii is a muscle of the face. Situated immediately beneath either eyebrow toward the bridge of the nose, it is found at the very top of the eye socket between the frontalis muscle of the forehead and the orbicularis oculi muscle of the eyelid. When contracting, this muscle pulls the eyebrows down and in toward the nose, producing a frown or other expression of displeasure or discomfort. In addition, the corrugator supercilii is the muscle used to squint against bright light, as it pulls the brow forward to shield the eyes.
Located just below the eyebrows and with fibers running parallel to the medial portion of the eyebrow — the portion of the brow to the inside of the arch — the corrugator supercilii originates on the superciliary arch. The superciliary arch is a curved bony prominence on the frontal bone that can be felt behind either eyebrow. This muscle arises between the eyebrows from the innermost end of either arch. When it contracts, it produces several vertical folds between the brows, giving the muscle the name corrugator, as in corrugated cardboard.
From the superciliary arches, the corrugator supercilii directs lateralward, its fibers ascending slightly toward the arch of the eyebrow. The muscle tapers before inserting into the underside of the skin just above the orbital arch, the ridge at the top of the eye socket, at its centermost point. From its point of origin to its point of insertion, this muscle is perhaps an inch long.
Contractions of the corrugator supercilii cause the muscle to shorten, pulling the skin toward its fixed point of origin on the frontal bone. This produces the vertical lines known as glabellar lines that have come to signify frowning or other expressions of disgust. The adjective supercilious in fact means to be full of contempt, getting its name from the very arches to which this muscle attaches. Not just indicative of disgust or scorn, however, the corrugator is essential to forming several other expressions, including pain and suffering, as well as to squinting in order to concentrate or block out bright light.
It is not uncommon for an individual to have this muscle frozen with an injection of a product containing botulinum toxin, or to have it detached all together. Such a procedure may be performed for cosmetic reasons, as in eliminating wrinkles, or for the treatment of a condition like a chronic migraine. Additionally, the corrugator supercilii may be paralyzed by botulinum injection for the treatment of facial muscle spasms caused by certain neurological disorders.