Table 1.

Facial Muscles’ actions and criteria for assessment.

Muscle Group	Action	Criteria for Treatment
Occipito-Frontalis	Moves de scalp back, raises the eyebrow and wrinkles the forehead	Asymmetry in eyebrow position. Frontal wrinkles (horizontal lines in the forehead) at rest on the nonparalyzed side
Corrugator supercilii	Pulls the eyebrows downward and toward the midline of the nose	Vertical medial lines in the glabellar region on the nonparalyzed side. Asymmetry in eyebrow positioning
Procerus	Draws down the skin between the eyebrows and assists in flaring the nostrils	Horizontal lines located at the root of the nose
Depressor supercilii	Draws down the eyebrows	Diagonal lines medially to the medial end of the eyebrow
Orbicularis oculi	Responsible for closing the eyelids, blinking and development of crow’s feet	Periorbital wrinkles in contraction and at rest, and pre-tarsal hypertrophy in the nonparalyzed side. Asymmetry in the eye opening.
Nasalis	Compresses the nostrils and may completely close them	Asymmetry of nasal wrinkles when sniffing
Levator labii superioris alaeque nasi	Dilates the nostril and elevates the lateral upper lip and wing of the nose	Asymmetry of the medial third of the nasolabial fold when sniffing. Center of the upper lip pulled up. Deepening of the nasolabial fold
Levator labii superioris	Elevates and everts the upper lip	Asymmetry of the medial third of the nasolabial fold. Exposure of the superior dental arch while smiling
Levator anguli oris	Pulls the angle of the mouth straight up and curves the mouth line upward at its ends	Asymmetry in the positioning of the lip corner
Zygomaticus Major	Pulls the angle of the mouth up out and backwards when smiling	Smile asymmetry in the upper lateral direction of the non-paralyzed side
Zygomaticus Minor	Pulls the middle section of the nasolabial furrow and middle portion of the side of the upper lip outward and slightly upward	Lip pulled upward and laterally, deepening of the upper middle portion of the nasolabial furrow
Orbicularis oris	Kissing, puckering and pressing lips against the teeth, closing the mouth	Philtrum deviation to the nonparalyzed sideAsymmetry of perioral wrinkles
Risorius	Pulls the modulus and therefore the angle of the mouth out and backwards	Lateral asymmetry at retraction of the angle of the mouth (sardonic expression)
Mentalis	Raises and wrinkles the skin of the chin, thus elevating the lower lip	“orange peel” texture and deep transverse mental crease on the nonparalyzed side
Depressor labii inferioris	Pulls the middle third of the lower lip straight downward	Smile asymmetries. Exposure of lower teeth arch on the non-paralyzed side when smiling. Lip asymmetry when ‘‘showing lower teeth’’
Depressor anguli oris	Depresses and lateral displace the angle of the mouth	Corner of the lips pulled down, Deepening of the nasolabial furrow
Platysma	Pulls the lower lip and corner of the mouth sideways and downwards	Excessive movement of the nonparalyzed side platysma when ‘‘showing lower teeth’’