Botulinum toxin in the frontalis muscle: patterns and risks

The forehead is one of the most requested areas for botulinum toxin and one of those that demands the most judgment. The horizontal lines are visible, the patient recognizes them at once, and the muscle responsible is easy to name: the frontalis. But the frontalis does more than wrinkle the forehead skin. It is the only brow elevator, and treating it means touching the position of the gaze.

This page reviews the functional anatomy, the contraction patterns and the risks of treating the frontalis, at a review level. There is no dose, injection point or technique. Management is the decision of the qualified professional, following the product label and the rules of their professional council in Brazil.

Functional anatomy of the frontalis

The frontalis muscle is the anterior portion of the occipitofrontalis complex. Its fibers arise from the galea aponeurotica, run up the forehead and insert into the skin and muscles of the brow, interlacing with the orbicularis oculi, the corrugator and the procerus. In some people there is a central separation between the two bellies, which affects the line pattern.

Points of practical interest:

• It is a wide, thin muscle, with variable extent in height and width.
• It has no direct bony insertion in the frontal area, which makes it dependent on the galea and the skin.
• It works together with the occipitalis muscle to pull the scalp.
• Its contraction is the only force lifting the brow, while several muscles pull it down.

The balance between the frontalis and the depressors, discussed in the glabellar complex, decides the brow position at rest and in expression.

Contraction patterns

Watching the patient raise the brows, from the front and slightly from above, shows the individual pattern. Common teaching descriptions:

The last pattern deserves emphasis. In patients with heavy eyelids, dermatochalasis or a low brow, the frontalis works all the time to keep the gaze open. Weakening it can worsen the droop, and the "smooth" forehead comes with a tired look.

Brow position

Brow position at rest is the most important piece of information before treating the forehead. Useful observations:

1. Height relative to the orbital rim: very low brows call for caution.
2. Shape: arched, straight, drooping laterally.
3. Symmetry between the sides and the difference in position at rest and in expression.
4. Upper eyelid skin: excess, laxity or prior surgery.
5. Role of the frontalis in keeping the gaze open: does the patient "lift" the brows to see better?

More on this subject is in brow position, botulinum toxin for the brow and aging of the forehead and brow.

Risks of treating the frontalis

• Brow ptosis: drooping of the brow as a whole, or of part of it. This is the central risk and is covered in ptosis after botulinum toxin.
• Heavy eyelid and a tired-looking gaze, with or without true eyelid ptosis, which comes from diffusion to the levator of the eyelid.
• "Mephisto" brow, with excessive lateral lift, described in Mephisto sign.
• "Frozen" forehead, with loss of expression and an artificial look.
• Asymmetry between the sides.
• Headache, reported by some patients.
• Bruising and local pain.
• Insufficient or short-lived effect, which may reflect the muscle pattern, the technique or the expectation. See lack of response to botulinum toxin.

When the frontalis should not be the focus

Some situations call for great care, or another strategy:

• Low brow or heavy upper eyelid at rest.
• A patient who uses the frontalis heavily to keep the gaze open.
• Thin, lax skin that loses support when the muscle relaxes, as in botulinum toxin in thin, sun-damaged skin.
• Prior surgery in the area (blepharoplasty, lifting), with altered anatomy.
• An expectation of a "completely smooth forehead," which is incompatible with safety.

In these cases, a more conservative approach, or choosing to treat only the glabella and preserve the frontalis, may be more prudent. The decision is the professional's and should be explained to the patient.

Relationship with the glabellar complex

Treating the frontalis without considering the glabella can change the shape of the brow: the depressors, without their antagonist, pull the brow down. Treating the glabella without considering the frontalis can leave the frontalis freer, lifting the medial portion. What matters is the balance between the two groups, which is why many plans consider both together, with the frontalis treated more conservatively.

The design of the plan varies from patient to patient and is the professional's decision.

How to assess at the visit

1. Observe at rest, in silence, for a few seconds.
2. Ask for brow elevation three times, from the front and from above.
3. Ask for a frown, to assess the glabella.
4. Compare the sides and record asymmetries.
5. Ask about toxin history, complications and prior satisfaction.
6. Photograph and film, following standardized clinical photography.
7. Align expectations: what the patient hopes to see when looking in the mirror.

How to talk to the patient

Where Harmy fits in

Harmy has the Glabella area and no specific area for the forehead or the frontalis. The app works with volume and does not simulate toxin in the forehead, wrinkles or brow position. The projection does not retouch the skin or change the expression.

Timeline

Quick review

The frontalis teaches a simple and costly lesson: the forehead is not a surface to smooth, but part of a system that holds up the gaze. Assessing the pattern, respecting brow position and explaining the limits to the patient is what makes toxin in the forehead a predictable procedure.