The corrugator supercilii (CS) are paired, obliquely oriented muscles located in the inferomedial brow deep to the inferior portion of the frontalis muscles.

The CS muscle originates from the bony superomedial orbital rim and passes in a superior and lateral direction to insert onto the fascia of the frontalis muscle and into the overlying skin (FIG 1).

In addition to coursing superiorly and laterally from its insertion, the CS becomes more superficial as it travels laterally.

The CS muscle body is pierced by the supraorbital and supratrochlear neurovascular bundles carrying sensory input to the trigeminal nerve (V1). The nerves then pierce the frontalis muscles approximately 2 to 3 cm above the supraorbital rim to travel subcutaneously to the forehead and scalp (FIG 2).

The medial head of the CS has motor innervation from the zygomatic branch of the facial nerve, whereas the lateral portion is supplied by the temporal branch of the nerve.

Contraction of the muscle causes vertical grooves in the glabellar skin and imparts an angry expression. Contraction also causes an inferomedial descent of the medial clubhead of the brow.

The procerus is a midline flat and pyramidally shaped muscle located at the root of the nose contributing to upper nasal contour.

The procerus originates from the periosteum and perichondrium of the nasal bones and upper lateral cartilages and from the fascia of the nasal superficial musculoaponeurotic system (SMAS) (see FIG 2).

Procerus inserts into the midline skin overlying the nasal root and interdigitates superiorly with the frontalis muscle (see FIG 2).

The motor innervation to the procerus is supplied by the zygomatic branch of the facial nerve.

Contraction of the midline muscle is responsible for horizontal glabellar rhytids, transverse rhytids on the nasal dorsum, and descent of the medial brow.