Optimising Botulinum Toxin in the Upper Face

The majority of practitioners in aesthetic medicine use botulinum toxin (BoNT-A) when rejuvenating the upper face. In fact, around three-quarters of practitioners use BoNT-A alone in this area with others using it in combination with hyaluronic acid (HA) fillers.^1,2 The efficacy and safety of BoNT-A in treating lines in the upper face – forehead, glabellar and lateral canthus lines – is well established.^3-5 It is also commonly used in elevating and shaping the eyebrows and in the reduction of hooding.^2,6 It has been suggested by one author at least, that treating the lines and features of the upper face has become a particular focus during the pandemic over the past two years. Face mask use obscures the lower face, making the expressive communication of the upper face even more significant.⁷

Whether you are experienced or newly qualified, it is important to ensure that we offer our patients the best outcomes from the use of BoNT-A in the upper face. This article gives a brief overview of how we optimise rejuvenation in this area, looking at optimal dosing, needle placement and injection technique whilst minimising the risk of unwanted adverse effects. While unwanted effects seldom occur and are usually mild and transient,8 practitioners nonetheless need to know how to respond to them.

Prior to the first injection

Optimal treatment begins the moment that the patient arrives in the practitioner’s office. During the initial consultation, information must be provided so that the patient understands both the procedure, and what outcomes are realistic.⁹ The patient’s treatment goals should be discussed, and an appropriate treatment plan should be put in place.¹

A thorough assessment of the patient’s physiognomy is a vital first step. This includes skin elasticity, expressivity, asymmetry and muscle strength as well as the position of the eyebrows, the height of the forehead, the pattern of glabellar, forehead or lateral canthal lines, and whether the lines are static or dynamic.^2,6,7,10 Age, ethnicity and gender will also affect treatment choices.^6,11,12 Once the practitioner has a full picture, they can select an appropriate dose, number and location of injection points and injection technique.

Injection technique

The recommended dose ranges are suitable for most patients but should be individualised, taking into account the assessment as described above.² In the treatment of lateral canthal lines, for example, clinical trials have shown that a total dose of 24U (units) of inco- or onabotulinumtoxin A is effective, consisting of 4U injections but it is important to note that a total dose as low as 4U across all injection points might be appropriate in some patients: consider older patients with reduced muscle mass or lower doses in the inferior lateral orbicularis oculi.^1,10 Similarly, for the treatment of forehead lines, the average total dose is 10U of inco- or onabotulinumtoxin A.² The range of total typical doses, however, runs from 8U to 25U, with a recommended range of one to 4U per injection and even 0.5U at two optional injection sites.^1,2,6,7 For glabella lines, the total recommended dose range for inco- or onabotulinumtoxin A is from 12U to 40U with individual doses ranging from 1U to 10U depending on the location and interplay between the different muscles.^7,13 In the UK onabotulinium A has regulatory approval for treating the upper face under the brand name Botox, incobotulinium A under the brand name Bocouture and abobotulnium A under the brand name Azzalure.^14-16 Note that doses of abobotulinumtoxin A differs from those for inco- or onabotulinumtoxin A.^6,9 A conversion ratio of 1:2.⁵ (inco/onabotulinumtoix A: abobotulinumtoxin A) has been suggested, however, the summary of product characteristics for each product should be checked before use.^6,14-16 Accommodating individual variation can also be done by selecting appropriate injection point patterns for the key areas of the upper face.^2,6,7,10 For forehead lines, between two and 11 injection points have been suggested.^1,2,6,7,14 The choice should be made based on the profile of the patient, whether a symmetrical pattern is more appropriate than an asymmetrical, depending on the number and pattern of rhytids in the forehead.^1,2,6,7,14 For lateral canthal lines, patterns of injection should correspond to the pattern of the lines that fan into the superior malar area, the lateral third of the brow, into both or neither.¹⁰ Similarly, five patterns of glabella contraction with corresponding doses and position of injections have been described.^13,15 These support an individualised rather than generic approach to the injection of BoNT-A in the upper face. The muscle contraction of the individual patient should be studied carefully in order to find the most appropriate model with further modification if needed.¹³

Injection technique, including appropriate needle size, angle of administration and depth of insertion, should also be selected to deliver the toxin to the required area while minimising risk of unwanted effects.^2,6,7 For example, in the treatment of the forehead and lateral canthal lines, insertion of the needle to a third of its depth is advised whereas in the glabella, deeper insertion is recommended in some muscles.²

Addressing the common adverse effects

The ‘frozen’ look

Over-injection of botulinum toxin or toxin given in inappropriate injection points in the frontalis can result in a ‘frozen’ appearance.² Due to the fact that the frontalis muscle raises the eyebrows which are used to express emotions such as delight, suspicion and surprise, the ‘freezing’ of the forehead can inhibit facial expressions.^2,6,7,11,12 ‘Frozen’ features due to over-injection are temporary and will resolve as the effects of the botulinum toxin wear off.⁹ However, the experience can be distressing for patients and prevention of this effect should be a priority for practitioners.¹³

Careful assessment of the patient’s face before injecting is of primary importance. Assess whether facial lines are dynamic or static in nature as well as the degree of severity. A 2020 review demonstrated that BoNT-A can be effective even in moderate to severe dynamic and static lines but patients with deeper static lines on the forehead may need a combination treatment of BoNT-A with HA fillers or other treatments.^2,9,11 Remember that both sides of the forehead may not be the same. Pre-existing asymmetry of brow height needs to be considered before choosing appropriate injection sites and the dose.² Forehead lines may not be evenly distributed across both sides of the forehead.7 Thus one side may require a higher dose or more injection sites than the other.⁷

Men tend to have greater muscle mass and forehead surface area than women and may require a higher dose.^6,11 Dr Javier Anido and colleagues recommend 2U in males compared to 1U of ona- or incobotulinum toxin A in females in most cases for lines on a ‘normal kinetic’ forehead.⁶ In an older patient, however, lower doses may be more appropriate due to decreased muscle mass and skin elasticity and when aiming for an age-appropriate effect.¹ Lower doses should also be considered in people with a low hairline as well as an immobile galea aponeurotica, in those with a forehead height less than 5cm and in those at risk of ptosis (see below).¹¹ It is sensible to start with a low dose when treating a patient for the first time or if there are any reasons to question the amount required to achieve the desired outcome.¹²

Ptosis

The incidences of downward displacement of the eyelid or eyebrow are reported to be around 0.71% to 1.8% and 0.98% to 2.6% respectively.^11,16 As with the ‘frozen’ appearance described above, eyebrow ptosis can result from over-correction of the frontalis muscle when treating forehead lines.^9,17,18 To minimise the risk of brow ptosis, injecting 1.5 to 2cm above the eyebrow or 2.5 to 3cm above the orbital rim is recommended.^6,7,11 Furthermore, smaller doses can be injected intra- or subcutaneously particularly closer to the eyebrows to limit depth and extent of effect.1,6 Check for low flat eyebrows in women in whom the frontalis muscle may be weaker and be mindful that men tend to have lower flatter eyebrows than women.² In individuals with very low brows, smaller doses injected superficially are recommended or injecting 4cm above the brow.^12,13

It is important to consider the interaction between the elevator frontalis muscle and the depressor muscles of the glabellar and eye area (procerus, corrugator, brow depressor, and orbicularis oculi) which governs the movement of the eyebrows (Figure 1).^1,6 Some authors recommend injecting the depressor muscles with BoNT-A when treating the frontalis.^2,12 This approach is recommended in patients with low brows, pre-existing brow ptosis or in patients aged over 60 years.¹²

If brow ptosis or brow asymmetry is the result of injection into only one group of muscles, physician Dr Rebecca Small from the University of California suggests that it can be corrected by injection into the opposing muscle group.⁹ Dr Small also reminds us that, as with a ‘frozen’ appearance, ptosis is temporary.⁹ Eyelid ptosis can occur during the treatment of glabellar lines with BoNT-A due to the migration of toxin through the orbital septum leading to the weakening of the levator palpebrae superioris muscle.^2,16,17 This can occur particularly when the injection is close to the bony supraorbital margin at the mid-pupillary line and contains a large dose.^2,16 Further, treatment with BoNT-A in the frontalis can reveal a pre-existing weakness in the levator palpebrae superioris muscle, leading to eyelid ptosis. The evaluation of the upper eyelid muscle is recommended prior to injection particularly in patients who may have experienced trauma in this area.⁶ Ensure that injections into the corrugator muscles are placed at least 1cm above the supraorbital ridge at the mid-pupillary line.⁹ The needle in injections in the glabellar and periocular area should be angled upwards away from the eye.² A corrective response to eyelid ptosis is the use of alpha-adrenergic agonist eye drops which widens the eyelid gap.^19,20 Apraclonidine has been shown to be effective in the treatment of eyelid ptosis.^19,21 Naphazoline or phenylephrine may also be used.¹⁹

The ‘Spock’ effect

The ‘Spock’ or Mephisto effect is the excessive lifting of the lateral part of the eyebrow either symmetrically or asymmetrically. It is related more to the positioning of the injection than to the dose of BoNT-A itself.¹⁸ When injecting the frontalis ensure that injection points extend far enough across the forehead to block the lateral as well as the central regions.^7,22 The effect can also occur when injecting the lateral canthus and glabellar lines with the aim of elevating the eyebrows. To prevent this, two lateral injections can be given in the frontalis.² To rectify the ‘Spock’ effect, one solution which has been shown to be efficacious is to inject a little more BoNT-A into the lateral-most point of the frontalis muscles.^7,23

Unwanted effects at the injection site

Oedema, erythema, bruising and tenderness can occur at or near to the site of infection.^2,9 These are usually mild and transient, resolving within 24 hours, although bruising can take two weeks to resolve.⁹ The lateral canthus area is particularly prone to bruising because of its high levels of blood vessels.² Paying close attention to superficial blood vessels in this area along with using a small gauge needle can minimise this particular unwanted effect.¹⁷ Ice is also useful as it causes vasoconstriction to limit bruising as well as for reducing pain.¹⁷ Headaches associated with BoNT-A injection are usually transient.⁹

Utilising botulinum toxin

Treatment with BoNT-A in the upper face is an integral part of contemporary aesthetic medicine. It is important to remind ourselves that, as practitioners, we can optimise this treatment by making wise choices in terms of injection points, dose and injection technique. Furthermore, we need to know how to prevent and respond to any unwanted effects. Underpinning these treatment choices lies our knowledge of facial musculature and vasculature as well as the careful assessment of the individual patient and of their treatment expectations. If the practitioner can apply this knowledge and careful patient assessment, they are likely to be well-equipped to offer the individualised treatment that minimises facial lines in a natural way, with lower doses and fewer injection points that we are moving towards in today’s practice.^1,7