Facial muscles in botulinum toxin: a review map
Botulinum toxin acts on the muscle, not on the wrinkle. That is why planning starts with anatomy: which muscle creates the line that bothers the patient, which way it pulls, who pulls against it and what lies next to it, a few millimeters away, waiting to be reached by unwanted spread.
This is a review map, organized by third of the face. It gives the origin and action in practical language, the role of each muscle in the balance between elevators and depressors, and what usually happens when it is weakened. It does not include doses, points or injection technique, which are decisions for the qualified professional, according to the product label and the rules of their professional council. The mechanism of the toxin is covered in botulinum toxin in facial harmonization: fundamentals.
Why think in terms of elevators and depressors?
Almost every facial expression is a tug of war. The eyebrow rises through the frontalis and falls through the glabellar muscles and the orbicularis oculi. The corner of the mouth rises through the zygomatic muscles and the levators and falls through the depressor anguli oris and the platysma. The resting position you see in a photo is the result of that balance, added to the weight of the tissues and to laxity.
Three practical consequences follow:
- Weakening a depressor lets the elevator act more. This is the principle behind some subtle lifts of the eyebrow and the corner of the mouth.
- Weakening the elevator lets the structure drop. If the frontalis loses too much strength, the eyebrow drops, because nothing else holds it up.
- The effect depends on what the patient already compensates for. Someone who uses the frontalis all the time to open the eyes has more to lose with a heavily weakened forehead.
A detail about innervation helps the reasoning: the muscles of facial expression are innervated by the facial nerve; the muscles of chewing, such as the masseter and temporalis, by the trigeminal nerve; and the levator palpebrae superioris by the oculomotor nerve. The toxin acts at the neuromuscular junction of any of them, as long as it gets there.
Upper third: forehead, glabella and eyes
| Muscle | Region | Main action | Elevator or depressor | When weakened | If it spreads beyond the target |
|---|---|---|---|---|---|
| Frontalis | Forehead | Lifts the eyebrow, forms the horizontal lines | Elevator (the only one for the eyebrow) | Softens forehead lines | Low eyebrow, heavy eyelid, peaked ("Spock") eyebrow if the lateral part stays active |
| Corrugator supercilii | Glabella, above the head of the eyebrow | Draws the eyebrow in and down, forms the vertical lines | Medial depressor | Softens the glabellar "11" | Eyelid ptosis through reach of the levator palpebrae |
| Procerus | Root of the nose | Lowers the head of the eyebrow, forms horizontal lines at the root of the nose | Medial depressor | Softens the transverse line at the nasal root | Uncommon in isolation; adds to the glabellar effect |
| Depressor supercilii | Inner corner of the eyebrow | Lowers the head of the eyebrow | Medial depressor | Helps open the medial region | Similar to the corrugator |
| Orbicularis oculi, orbital portion | Around the orbit | Closes the eye forcefully, lowers the tail of the eyebrow, forms crow's feet | Lateral depressor | Softens crow's feet, may slightly lift the tail | Altered smile through reach of the zygomaticus major; eye that closes poorly |
| Orbicularis oculi, palpebral portion | Eyelids | Closes the eye gently, blinking | Sphincter | Not a usual target | Dry eye, incomplete closure, lower eyelid sitting lower |
| Levator palpebrae superioris | Inside the orbit | Lifts the upper eyelid | Eyelid elevator | Not a target | Eyelid ptosis |
The frontalis has no bony attachment: it arises from the galea aponeurotica and inserts into the skin of the eyebrow, blending its fibers with those of the depressors. In practice, it "hangs" the eyebrow. The glabellar depressors, corrugator, procerus and depressor supercilii, work together in the expression of anger or concentration. The orbicularis oculi is a sphincter, with a stronger orbital portion and a palpebral portion responsible for blinking and protecting the cornea.
The levator palpebrae superioris appears on the map for one reason only: it is the neighbor nobody wants to reach. The eyelid droop that results is covered in ptosis after botulinum toxin.
Middle third: nose, upper lip and smile
| Muscle | Region | Main action | Elevator or depressor | When weakened | If it spreads beyond the target |
|---|---|---|---|---|---|
| Nasalis, transverse part | Lateral dorsum of the nose | Compresses the nostril, forms the "bunny lines" | Compressor | Softens nasal lines | Reach of the levator labii superioris alaeque nasi |
| Levator labii superioris alaeque nasi | Side of the nose to the lip | Lifts the upper lip and flares the nostril | Elevator | Reduces gum show in the central region and medial nasal lines | Lengthened upper lip, asymmetric smile |
| Levator labii superioris | Below the orbit to the lip | Lifts the upper lip | Elevator | Reduces gum show | Lengthened lip, "drooping" smile |
| Zygomaticus minor | Zygomatic bone to the lip | Lifts the upper lip | Elevator | Rarely an isolated target | Altered smile |
| Zygomaticus major | Zygomatic bone to the corner of the mouth | Pulls the corner of the mouth up and out when smiling | Elevator of the corner of the mouth | Not a usual cosmetic target | Asymmetric smile, corner that rises less |
| Levator anguli oris | Canine fossa to the corner of the mouth | Lifts the corner of the mouth | Elevator of the corner of the mouth | Not a usual target | Lower corner of the mouth |
| Depressor septi nasi | Base of the nose | Lowers the nasal tip when smiling | Depressor | May reduce the drop of the tip when smiling | Altered upper lip |
| Risorius | Side of the mouth | Retracts the corner of the mouth sideways | Retractor | Not a usual target | Asymmetric smile, common as a spread effect from the masseter |
The muscles of the upper lip are the protagonists of the gummy smile, discussed in botulinum toxin for the gummy smile. The zygomaticus major is the main smile muscle and the one most often recalled when talking about spread: it can be reached from the crow's feet area, from below, or from the masseter, from behind.
Lower third: mouth, chin, neck and chewing
| Muscle | Region | Main action | Elevator or depressor | When weakened | If it spreads beyond the target |
|---|---|---|---|---|---|
| Orbicularis oris | Around the lips | Closes and projects the lips, forms the perioral lines | Sphincter | Softens perioral lines | Difficulty whistling, using a straw, articulating words, holding liquids |
| Depressor anguli oris | Mandible to the corner of the mouth | Pulls the corner of the mouth down | Depressor of the corner of the mouth | May soften a downturned corner | Reach of the depressor labii inferioris: asymmetric smile |
| Depressor labii inferioris | Mandible to the lower lip | Lowers and everts the lower lip | Depressor | Not a usual target | Shows fewer lower teeth on one side |
| Mentalis | Chin | Lifts the chin and projects the lower lip, forms the "orange peel" look | Elevator of the chin | Softens a wrinkled chin | Altered position and seal of the lower lip |
| Platysma | Neck to the mandible and mouth | Tenses the neck, pulls the lower third down | Depressor | Softens neck bands, may ease the pull on the jaw | Difficulty swallowing, voice change, neck weakness |
| Masseter | Zygomatic arch to the angle of the mandible | Lifts the mandible, closes the mouth with force | Elevator of the mandible | Reduces strength and, over time, volume | Altered smile through reach of the risorius and zygomaticus major |
| Temporalis | Temporal fossa to the mandible | Lifts and retracts the mandible | Elevator of the mandible | Reduces closing force; may be considered in the context of bruxism | Little described; watch for temporal hollowing in thin faces |
The orbicularis oris is a sphincter and acts as an antagonist to almost every muscle that opens and moves the lips. The depressor anguli oris is a neighbor and partly overlaps the depressor labii inferioris, which explains the smile asymmetry when toxin reaches the wrong muscle. The mentalis is the main elevator of the chin and the lower lip.
The platysma is a broad, thin muscle of the neck that rises over the mandible and blends with the muscles of the mouth. Because it lies over structures of swallowing and speech, it calls for special attention to spread. Finally, the masseter is not a muscle of facial expression but of chewing; its treatment is covered in botulinum toxin in the masseter.
How do you use the map in the assessment?
The map becomes clinical reasoning when you apply it to the concern:
- Identify the wrinkle or position that bothers the patient and ask for the movement that forms it.
- Name the responsible muscle and the direction it pulls.
- Ask who the antagonist is and whether it is compensating for something.
- List the neighbors at risk, those that would change function or expression if reached.
- Decide whether toxin is the right tool. Static wrinkles, laxity or volume loss do not respond to toxin alone, and the dynamic wrinkle is the one that responds best.
The list of complications by region, with a timeline and initial management, is in complications with botulinum toxin. When something does not go as planned, the path for talking with a lay patient is in botox gone wrong.
And in Harmy?
Anatomy review checklist before toxin
- Movement that forms the concern observed and photographed.
- Responsible muscle and antagonist identified.
- Compensations assessed, especially the use of the frontalis to open the eyes.
- Neighbors at risk listed for the planned region.
- Smile assessed at rest and in motion when the plan involves the middle or lower third.
- Previous asymmetries recorded.
- Indication checked against the label of the registered product.
- Patient informed about the possible effects of the treated region.
Frequently asked questions
Which facial muscles are treated with botox?
The most commonly mentioned are the frontalis, corrugator, procerus and orbicularis oculi in the upper third; the muscles of the nose and upper lip in the middle third; and the orbicularis oris, depressor anguli oris, mentalis, platysma and masseter in the lower third. The choice depends on the assessment of each patient.
Which muscle lifts the eyebrow?
The frontalis is the only eyebrow elevator. On the other side are the depressors: the corrugator, procerus, depressor supercilii and the orbital portion of the orbicularis oculi. The shape of the eyebrow depends on the balance between them.
Which muscle causes a drooping eyelid after botox?
In eyelid ptosis, the affected muscle is usually the levator palpebrae superioris, which lies inside the orbit and is not a target of cosmetic toxin. It can be reached when toxin spreads from injections near the orbital rim.
Why does botox in the face act on muscles that lift and muscles that lower?
Because expression results from the balance between elevator and depressor muscles. Weakening one side lets the other act more, which can reposition the eyebrow or the corner of the mouth, for better or worse.
Harmy images are illustrative simulations generated by AI from the patient's photo to support the conversation between practitioner and patient. They are not a promise of results. Indication, technique, product and volume are solely the decision of the licensed practitioner. This content is for information only and does not replace a clinical assessment.