How to avoid causing an S-shaped eyebrow from Botox treatment

When discussing botulinum toxin or Botox® treatment in the upper face, we must discuss complications and unwanted dynamic side effects. Previously, we explored issues following treatment around the eye area, including the presentation of bunny lines and under-eye lines; other less-than-desirable outcomes can affect the eyebrows, most notably causing the so-called Spock brow, and the perhaps lesser-known S-shaped brow and fish-hook brow.

Unwanted dynamic effects are caused by undertreatment or overtreatment with botulinum toxin; they are more commonplace than potentially more serious complications, yet, we must still aim to avoid them to ensure patient satisfaction from treatment.

In this blog, Dr Tim Pearce will discuss the dynamics of the S-shaped brow, the anatomy, and how it happens, alongside injection strategies to avoid it.

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What is an S-shaped brow?

The S-shaped eyebrow side effect following botulinum toxin treatment is closely related to the much-talked-about Spock brow. We will not be covering that in this blog, but for more insight from Dr Tim on Spock brows, please read,

• How to fix a Spock brow and avoid it happening again after Botox treatment
• Tutorial: 3D Anatomy Botox (Botulinum Toxin) Brow Lift
• Injecting the glabella: Botox injection points & safety advice
• Injecting Botox into the frontalis muscle, safety advice

The S-shaped brow tends to happen when treating frown lines in the glabella, sometimes done in isolation, and when treating the frontalis muscle for forehead lines. The shape created is as a result of a small, medial brow drop and a lateral brow lift or a neutral brow.

Eyebrows are typically a continuous arch shape but the combination of causing a lateral raise and a medial downwards push results in conflict and the arch becomes distorted and S-shaped or wiggled.

This manifestation is caused by treating the frontalis muscle too low down, whereby, a small amount of botulinum toxin from either the corrugator or frontalis injection point causes the slight medial drop and lateral lift. The problem can be either symmetrical (affecting both sides and both eyebrows) or asymmetrical (only affecting one eyebrow). Of course, patients find an asymmetrical occurrence the most disturbing, because it is more obvious. If it happens on both sides of the eyebrows, they will still be dissatisfied, but it can more easily go unnoticed by others.

How to avoid causing an S-shaped brow with Botox treatment?

The most likely origin of this effect is the middle injection of the corrugator when treating the glabellar area by injecting the botulinum toxin a fraction too superiorly. Similarly, if the frontalis muscle is treated with an injection placement that is too inferior, it can cause an S-shaped brow.

To avoid this, we must be very clear about safety margins and injection accuracy when treating the corrugator muscle with Botox. Inject towards the origin of the muscle and be very clear about the insertion points that you can normally see on the skin’s surface to help you identify the location of the corrugator.

By thinking clearly about the anatomy and injecting the botulinum toxin precisely into the body or belly of the corrugator muscle, you can avoid inadvertently hitting the frontalis muscle above.

Consistent safety margins help to defend or protect the frontalis muscle from unintentional impact. The safety margin maintains a 2cm boundary above the orbit or 50% of the forehead, whichever is less. Smaller foreheads may need a slightly shallower boundary, but you must ensure adequate muscle activity to avoid a drop in the forehead. It is good practice to draw a box that highlights your safety margin to avoid affecting the muscle responsible for lifting the medial brow.

Marking up a patient’s face before injecting is important because injection accuracy is maintained by your markings, even for experienced injectors, many of whom stop this practice over time, perhaps unadvisedly. Even with the best intentions and good habits, small variations in your bedside position or angle as you lean over a patient while assessing or injecting them can lead to asymmetry. To minimise this, it is essential to mark up the face, evaluate it head-on for asymmetries, and account for safety margins. Additionally, consider how your injection angle and consistent positioning – especially if injecting from one side – can create discrepancies, resulting in uneven treatment of muscles and unwanted effects.

What can you do if you have caused an S-shaped brow with Botox treatment?

Remember the presentation of the S-shaped brow is slightly more lift laterally and a slight depression medially. Any correction should aim to counterbalance these forces.

If the eyebrow is overly lifted – too much neurotoxin in one side and too little laterally – you can carefully place one Botox unit just above the arch to slightly lower the S-curve of the brow, provided the other side has sufficient symmetry to maintain balance. It is crucial to avoid causing a noticeable drop on one side, so this adjustment to smooth the lift requires careful consideration. Additionally, address any factors pulling the medial brow downwards, such as the superficial edge of orbicularis oculi within the eyebrow or the corrugator and depressor supercilii, which may contribute to the issue.

It is unlikely that any one of these muscles represents the whole problem, hence, even if you treat them individually, you may still have some noticeable depression medially, but treating all should produce a slight, additional lift which will give patients hope of improvement to their eyebrow shape.

How to manage patient expectations from a complaint about an S-shaped brow from Botox treatment

When complications, side effects, or unwanted results occur, it is essential to communicate clearly with your patient, so they understand what has happened.

In cases of subtle asymmetries, like an uneven eyebrow, take the time to explain what you have learned about their unique facial structure. Often, the issue may stem from something as simple as an injection point that is off by as little as half a centimetre. Helping your patient understand this can shift their perception from viewing you as a “bad injector” who has given them a “botched” result to recognising it as a learning moment for refining their future treatment. Remember to explain the proposed solution or potential fix and how it will work.

This not only builds trust but also reassures the patient that the likelihood of this outcome will be reduced and can be avoided next time.

Frame the experience as a collaborative learning process, because all faces are unique, to foster loyalty, minimise negative reviews, and turn a challenging situation into an opportunity to strengthen your relationship with the patient.

Here are additional blogs from Dr Tim, exploring potential side effects and unwanted outcomes related to Botox treatments in the upper face.

• How to avoid causing eyelid ptosis with botulinum toxin treatments
• How to avoid lateral rectus palsy and double vision from Botox treatment
• How to avoid lacrimal gland compromise and dry eye from Botox treatment
• How to avoid unwanted dynamic effects (new lines) from Botox treatment

If you have any questions or topics for discussion, you can find Dr Tim Pearce on Instagram.

Botox® is a registered trademark of Allergan Aesthetics plc.

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