Botulinum Toxin for Brow Lifting

What is botulinum toxin for brow lifting?

Botulinum toxin for brow lifting means using botulinum toxin to temporarily relax the muscles that pull the brow down, so that the brow sits a little higher. No substance is used to push the brow up, and no tissue is lifted; what changes is the balance between the muscles that pull the brow in two directions. This is why the result depends on your own muscle structure and on why your brow sits where it does now.

In everyday speech the treatment is called by a product name, but its active ingredient is botulinum toxin type A. When it is injected in small amounts into a target muscle, it temporarily reduces the muscle’s contractions. According to a source on cosmetic treatments, in wrinkle treatment the full effect usually takes two weeks to appear, and the effect lasts about three to four months.

One basis for explaining brow position through muscle balance is a study that examined how the brow muscles work using electromyography (measuring the electrical activity in muscles). According to this study, the brow is held in place by a dynamic balance between the frontalis, the corrugator (the muscle that draws the brows together when you frown) and the orbicularis oculi, and its position is set by these muscles coming into play in different combinations. The researchers suggest that weakening the muscles that pull the brow down could restore this balance.

A systematic review (a review that brings together the studies on a topic using set rules) of botulinum toxin treatments for brow shaping states that there is no standard approach in this area and that the debate is ongoing. The dose, injection points and depth are decisions the doctor makes individually for each person.

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What holds the brow up, and what pulls it down?

The position of the brow does not depend on a single muscle. The frontalis lifts the brow. The corrugator, the depressor supercilii (the brow-lowering muscle), the procerus (the muscle at the root of the nose) and the upper outer part of the orbicularis oculi pull the brow down and inwards. A brow-lifting treatment targets this second group; how the frontalis should be treated is a separate question.

According to a cadaver (anatomical) study, the frontalis ends a few millimetres above the brow, where it merges with the opposing muscles, and this junction line drops lower in the outer third of the brow. It has also been reported that the corrugator spreads beneath most of the hair-bearing part of the brow, and that the soft tissue at the outer side of the brow is looser than at the inner side.

Another cadaver study, which mapped the position of the corrugator relative to the brow, shows that this muscle almost coincides with the inner end of the brow but diminishes markedly beyond the line of the pupil. In other words, the muscles that pull down the inner and outer parts of the brow are not the same. This is the anatomical explanation for why the inner and outer parts respond differently to treatment.

There is no consensus on how these muscles work, either. A split-face study (one side of the face compared with the other) of 298 patients challenges the view of the corrugator as purely a muscle that pulls the brow down; it suggests that this muscle may also play a part in raising the inner part of the brow. In the same study, targeting different parts of the muscle produced different amounts of lift, but with this approach, omega-shaped lines were also often seen between the brows.

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The outer end of the brow (tail of the brow)

Brow-lifting treatments most often target the outer part of the brow. Here, the main muscle that pulls the brow down is the upper outer part of the orbicularis oculi; weakening this part is associated with a lift in the outer part of the brow. The clearest measurements in studies also come from this area.

In a small study in which ten women were measured before treatment and two weeks after, a measurable lift in the outer part of the brow and a wider opening between the eyelids were reported after treatment to this part of the muscle; symmetry between the two sides was preserved. However, the study is small and has no comparison group, so it is not enough to generalise its results.

Studies on ageing also draw attention to this area. In a study comparing women aged 20 to 30 and 50 to 70, the outer tip of the brow sat lower in the older group in all the facial movements examined. In an electromyography study of women in the same age ranges, the activity of the orbicularis oculi was significantly higher in the older group in most movements.

Anatomical studies have also reported that the soft tissue at the outer side of the brow is looser than at the inner side. So a low outer brow may be caused not only by muscle activity but also by the tissue itself; which of these plays the bigger part for you is identified at your consultation.

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The inner brow and the area between the brows

Treatment between the brows can affect not only the lines there but also the position of the brow. This area contains the corrugator, the depressor supercilii and the procerus, which pull the brow down and inwards; relaxing these muscles can lead to different results in the inner, middle and outer parts of the brow.

In a dose study of treatment between the brows, participants were randomly assigned to groups, and neither the participants nor the assessors knew which dose was given (a randomised, double-blind trial). Photographs of the 79 women in this study were later re-examined. After treatment only between the brows, a lift was seen first in the outer part of the brow and then in the middle and inner parts; this lift peaked at week 12. In the lowest-dose group, a slight drop in the brow at first and the weakest response were reported. The researchers try to explain this change by the toxin spreading to the inner fibres of the frontalis.

A randomised trial compared two techniques: treating only the muscles that pull down the outer part of the brow, and treating the muscles of the outer and inner parts together. The two techniques produced different patterns of lift. In the group treated only in the outer part, the brow rose at all measurement points, whereas in the group in which both areas were treated, there was no change at the inner end of the brow.

It is hard to predict how the inner part of the brow will behave. In a case series describing three patients, after treatment between the brows using the usual technique, the patients described a flattening between the brows and a feeling that their brows had moved apart; an additional injection into the depressor supercilii was reported to lift the inner part of the brow. However, this is only a case series and cannot be generalised.

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How does forehead treatment affect the brow?

The frontalis is the muscle that lifts the brow. So treatment for forehead lines can work in the opposite direction to a brow-lifting treatment and lower the brow. In short, the wish to lift the brow cannot be considered separately from how the forehead is treated.

In a randomised trial in which the muscles pulling the brow down were treated and the frontalis was treated in three different patterns (15 patients in each group), the brow was lower two weeks later at all measurement points except its outer end; only the outer end measured higher. Treatment to the middle part of the forehead lowered the brow more than treatment to the upper part. Treatment to the upper part of the forehead was less effective for forehead lines, but it reduced the risk of a drooping brow.

In a study that used three-dimensional photography and followed participants over time, in the group treated in the forehead as well as between the brows, the brow had dropped significantly along almost its whole length two weeks later; this drop had lessened by the third month. No clear trend was seen in the group treated only between the brows. According to the researchers, the degree of change in the brow is determined by how much the frontalis is weakened; age alone is not a reliable predictor.

In practice, this means that the wish to lift the brow and the wish to soften forehead lines can conflict in the same face. A study reporting that frontalis activity increases with age, and that this compensation keeps the brow in place, also suggests that in some people the frontalis acts as a support that holds up the brow.

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How much lift do studies report?

In studies, the measured lift is in the millimetre range. In the systematic review of brow-shaping treatments, the greatest lift was seen in the outer part of the brow and was reported as between 0.4 and 4.8 millimetres. This range is wide and comes from different techniques and different patient groups, so it cannot be read as what any one person should expect.

This review covers 11 studies that used objective measurements, with 585 patients. All the studies used the same type of product; seven treated the muscles that pull down both the outer and inner parts of the brow, two treated only the outer part and two treated only the inner part. The researchers concluded that the treatment is safe and reproducible, but they stress that more randomised controlled trials are needed.

Figures from individual studies also fall within this range. In a randomised trial in which only the muscles of the outer part of the brow were treated, the brow rose by 0.6 to 2.1 millimetres, depending on the measurement point. In the group in which the outer and inner parts were treated together, a lift of 1 to 1.7 millimetres was measured from the line of the inner edge of the pupil to the outer end of the brow. These figures come from a small study in which 30 brows were measured in each group.

You should also know how limited the evidence is. The 65 randomised trials in the Cochrane review on facial wrinkles cover areas such as between the brows, the outer corners of the eyes, the forehead, around the mouth and the whole face; brow lifting is not included as a separate topic. The evidence on brow lifting is limited to small randomised trials, measurement studies and one systematic review that brings them together.

There is an expert opinion that deeper injection gives more lift when correcting a height difference between the two brows. To test this, 23 women had deep injections on one half of the face and superficial injections on the other; at week 4, there was no significant difference between the two sides in the change in brow height. The researchers attribute this to the toxin spreading between the muscle layers.

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Limits of this treatment

Botulinum toxin for brow lifting changes the muscle balance; it does not tighten the skin, lift the tissue or add volume. If your brow looks low because of loose skin and tissue rather than muscle, the treatment does not act on this cause. The effect is not permanent and wears off on its own over time; the treatment has to be repeated to maintain it.

Nor is it as clear as often assumed that the brow really drops with age. In a meta-analysis (an analysis that combines data from several studies) bringing together 19 studies and 3,634 people, brow height at the inner part of the brow and at the line of the pupil increased with age, while at the line of the outer corner of the eye there was no significant difference. Another study of 95 people found no difference in brow height between age groups; this study reported findings suggesting that excess skin on the upper eyelid increased as brow height decreased, as well as an increase in frontalis activity with age.

In practice, this means that what looks like a ‘drooping brow’ in the mirror may, in some people, actually be excess skin on the upper eyelid, with the brow being held in place by the effort of the frontalis. In such a case, relaxing the muscles that pull the brow down may not give the expected result, and weakening the frontalis can even lower the brow.

On the other hand, a case report describing a brow thread lift states that with ageing the forehead and brow move downwards, and that this can make the eyelids look heavy. According to this report, botulinum toxin can help raise the brow, but its visible effect may be limited. These differing views show that brow position depends on different causes in different people; which cause plays the bigger part for you is identified at your consultation.

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How it differs from a surgical brow lift and a thread lift

Botulinum toxin for brow lifting is not a smaller version of a surgical brow lift or a thread lift; it answers a different problem. Surgical and thread methods aim to lift the tissue mechanically, whereas botulinum toxin only changes the muscle balance temporarily. Which one makes sense depends on why your brow looks low.

Of the ten methods covered in a review of brow-lifting methods, two are non-surgical: botulinum toxin and fillers. According to the review, these two methods are temporary and are easier to correct if a problem arises; on the other hand, no brow-lifting technique is fully satisfactory, because of limited effectiveness, short duration and possible complications.

Surgery has its limits too. In a meta-analysis of 12 studies combining the long-term results of endoscopic brow lift (an operation done through small incisions with the help of a camera), the average lift at the inner, middle and outer parts of the brow was 3.25, 3.86 and 4.35 millimetres respectively. According to another review of open or endoscopic forehead and brow lift methods, the highest long-term lift did not exceed 5.6 millimetres in any study, and the lift decreased markedly over time.

A thread lift sits between these two approaches. A case report describing a brow thread lift defines this method as a middle path between surgical and non-surgical methods; it states that it gives a more limited improvement than surgery and needs to be repeated at certain intervals. A publication on the anatomy of the area also highlights the importance of assessing the blood vessels in the forehead and the mobility of the tissue before treatment.

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Why isn’t the same injection pattern used for everyone?

In the brow area, a standard injection pattern does not give the same result in every face. The shape and thickness of the muscles, and how they relate to each other, vary from person to person; treatment at the same point may lift the brow in one person but create an unwanted brow shape in another.

According to two reviews of the anatomy of the forehead and the area between the brows, a lack of detailed knowledge about the shape and position of the muscles can lead to unwanted effects such as a drooping eyelid (ptosis) or a sharp upward lift of the outer end of the brow (a ‘Spock brow’, also called a ‘samurai brow’). Both reviews suggest injection points based on anatomical landmarks that can be identified from the surface, and see detailed knowledge of the anatomy as the basis for reducing the risk of unwanted effects.

According to a review by a group of experts, when the general injection patterns recommended by manufacturers do not take anatomical differences into account, they contribute to outcomes such as a drooping brow, an unnatural brow lift and a distorted brow shape. The suggested solutions include adjusting the dose, depth and injection site to the individual, and considering linked or opposing muscles together. The level of evidence of this review is expert opinion.

Targeting is not as precise as often thought, either: the lack of a difference in the study comparing deep and superficial injection was explained by the toxin spreading between the muscle layers. A source on upper-face complications also names two conditions for reducing the risk of unwanted effects: knowing the anatomy of the area, and individual planning based on the contraction patterns of the forehead, the area between the brows and the outer corners of the eyes.

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Known risks

Botulinum toxin is a prescription-only medicine, and side effects of treatment in the brow area have been described. Most of them are mild and temporary; however, effects on the position of the brow and eyelid can last until the medicine wears off. The rates below come from other studies and cannot be used to calculate your personal risk; even so, knowing the possible effects in advance is part of the decision process.

Common effects: In the systematic review of brow-shaping treatments, the most frequently reported adverse effects were bruising and headache; five cases of drooping eyelid were recorded in this review of 585 patients. The studies in the review are small. A source on cosmetic treatments also states that mild bruising and swelling can occur.

Drooping brow and eyelid: In a systematic review covering 8,787 people, drooping eyelid was reported in 2.5% and drooping brow in 3.1% after upper-face treatments, and all cases resolved on their own. According to the Cochrane review, treatment probably increases the risk of a drooping eyelid. The source on cosmetic treatments also lists temporary drooping of the eyelid and brow among technique-related complications.

Unwanted change in brow shape: A sharp upward lift of the outer end of the brow is known as a ‘Spock brow’ (also called a ‘samurai brow’; medical name: ‘Mephisto sign’). One case has been reported in which this appearance developed after treatment to the frontalis for migraine; an additional injection at the outermost point of the frontalis corrected the brow shape. A feeling that the brows have moved apart has also been described in individual cases.

Other effects: A source on upper-face complications lists brow asymmetry, double vision, the eyelid not closing fully, the lower eyelid turning outwards and more prominent under-eye bags. In a review of 20 studies, the most frequently reported notable complication was drooping of the upper eyelid; this was mostly managed with conservative (non-invasive) methods such as eye drops. The review states that the evidence in this area is of a low level.

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