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Farber et al. Plast Aesthet Res 2020;7:72 I http://dx.doi.org/10.20517/2347-9264.2020.152 Page 15 of 28

Muscle/muscle group Muscle action Static/dynamic rhytids
Frontalis (A) Elevation brows Horizontal forehead lines
Glabellar muscles: Medial Elevation of brows Frown lines, glabellar creases
Corrugator supercilii (B) Depressor of brows
Procerus (C)
Orbicularis Oculi (D) Elevation of eyelids, concentric tightening of Crow’s feet
periorbital tissue
Nasalis (E) Medial elevation of nasal skin Bunny lines
Levator labii superioris alaeque nasi (F) Elevation of the central lip Gummy smile, nasolabial Folds
Orbicularis oris (G) Lip pursing, lower lip and corner of mouth Radial lip lines, smoker’s lines
depressor
Depressor anguli oris (H) Corner of mouth depressor Down turned smile, marionette lines
Mentalis (I) Elevation of chin and lower lip Dimpled chin, Chin lines
Common Neuromodulator Injection Sites

Figure 11. Muscles of facial expression, their actions, corresponding wrinkles, and points of neuromodulator injection [44]

The frontalis, which creates transverse forehead rhytids, as seen in Figure 13, should be injected in 1.25-2 unit
aliquots, depending on the injector’s preferred dilution. Injections should be deep given the anatomy of
the frontalis muscle and should be planned based on the individual patient’s forehead rhytid pattern. To
maintain an aesthetic brow shape, injections should not extend too inferiorly or laterally to preserve brow
height and arch.

The glabellar muscles, which create mid-brow rhytids, as seen in Figure 14, include the corrugator and
procerus. These can be injected in a V pattern with 4-5 units of botulinum toxin per injection. The plane of
injection should be deep in order to preserve frontalis in this area. The specific injection pattern should be
titrated to the individual patient’s rhytid morphology when animating.