Botulinum Toxin Injection



Now we focus on Zoe’s jawline profile. We can see that at rest it is very smooth, however, if she activates her DAO (depressor angularis oris), she gets significant downturn of her mouth corner. At the same time, she activates her platysma muscle, forming a strong platysmal band which disrupts her jawline. Therefore, during animation, she goes from having a smooth jawline to having a blunted jawline purely due to muscle action. We can treat this using a technique known as the Nefertiti lift.

Anatomy markings

Let’s now take some time to review the surface anatomy of the muscles that are involved when we treat the lower face with botulinum toxin. The most important landmark here is the modiolus, which serves as a point of attachment for several muscles, and is just lateral to the oral commissure. We can see that there are a number of muscles indicated by the drawing here. Let’s start by looking at the orbicularis oris, which is a sphincteric muscle going around the lip, which allows us to open and purse the lips. We have the zygomaticus major from the maxilla to the modiolus which allows us to raise the mouth corners during a smile. Moving down, we next have the risorius, which attaches from the masseter to the modiolus and is important for the lateral component of a smile. Not every patient possesses a risorius muscle. Next, we can see the masseter, which is a bulky muscle in some patients, and is a muscle of mastication. In Zoe’s case, this is not particularly prominent. Moving forward, we can see the DAO, a paranodal shaped muscle which has a wide origin on the mandible, and inserts into the modiolus to draw the mouth corner down during active contraction. There is a close association between the DAO and the muscle behind it, the DLI, or the depressor labii inferioris. This muscle is frequently accidentally injected with Botox when we are trying to do a DAO treatment. We then have the mentalis, which is a paired muscle in the chin, which is actually a lower lip elevator. Finally, you can see the platysma stretching from the clavicle and pectoral fascia to insert into the mandible and then also continue up into the face as the SMAS. There are close connections between the platysma, the mentalis, and the DAO. An interesting aspect of treatment in the lower face is the tug of war which can occur between opposing muscles; look at the zygomaticus major and the DAO – the zygomaticus major pulls up the mouth corner during a smile, whereas the DAO brings the mouth corner down during a frown. If we therefore weaken the DAO by treating it with botulinum toxin, the zygomaticus major will predominate, and it can therefore elevate a drooping mouth corner.

Injection site markings and treatment

Let’s review the injection marks for treating Zoe in her lower face, in particular for the DAO and the Nefertiti lift. If I get her to activate her DAO, you can see that the mouth corners go down, and you can also see a visible bulge of the muscle – the DAO is often palpable. If you can palpate the muscle, it is ideal, because it aids in accurate placement of the mark. My preference is to inject low and closer to the mandible because this way there is less chance of diffusion to the depressor labii inferioris which sits up a little higher and posterior to the muscle. We can now make a marking on the other side, and again we get her to contract so we can palpate and see the muscle, and then we’ll make an injection point for treatment. In this position, I also get her to activate her platysma, and we can see one very dominant platysmal band, which is responsible for contributing to bringing the mouth corner down in association with the DAO. I make 4 marks along this platysmal band.


Finally, there is also a cervical component of the platysma, which is responsible for dragging the soft tissue over the jaw and blunting the jawline. I am taking a reference point as a line continuing down from the nasolabial fold, and I will make 4 little marks along the jawline in which to inject the botulinum toxin. This will target the cervical platysma.


Let’s begin by treating the DAO – we inject the needle inferiorly, aiming laterally and very superficially, with a starting dose of 2 units. I will continue treating Zoe on her left side, and we move onto the platysma muscle treatment. When she activates, we can clearly see the dominant platysmal band we marked out earlier, and I will inject 2 units into each location. I grip the cord-like band between my thumb and finger, insert the syringe into the band, and each mark will receive 2 units. Some injectors feel you only need to inject the upper part of the band to get the maximum aesthetic effect. Finally, we move on to treating the cervical platysma – I just draw the skin down, insert the needle subdermally, and we will inject one unit into each of these 4 locations. I notice that my needle and syringe become just a little bit sticky, so to avoid over injecting I use two hands for the first injection point. That concludes our treatment, and we will review Zoe in 4 weeks to see the results of her treatment.

Treatment outcomes at 6 weeks

In terms of the lower face, if I ask her to tense her DAO, you can see she has got much less activity. From the side, although she has got a flicker of movement in her neck, her jawline stays very smooth and contoured compared to pre-treatment. This is a successful Nefertiti lift treatment.