Botulinum Toxin Injection



I would like to introduce our next model here, Michelle, who is currently 33 years old. If we look at her face, we notice that her face shape is essentially oval, however, she has a prominent jaw, and this has the effect of perhaps making her face look a little bit more square. The reason for this prominent jaw is that she has a very hypertrophic masseter muscle, and she tells me that she clenches her teeth, especially at night, often leading to headaches. So we can see that if we were able to contour the jaw, we would be able to give her face a more oval and more attractive facial shape.


When we look at Michelle’s eyes, we will notice that she has thick bands below each eye – these are due to hypertrophy of the orbicularis oculi muscle. If Michelle smiles we notice that they thicken even more, this can lead to a heavy appearance of the lower eye. You will also notice that at rest she has a very narrow aperture of the eye, so the narrowed aperture plus the thickened orbicularis makes her a good candidate for Botox treatment in the infraorbital region. If we are going to do this, we should assess the skin and integrity of the lower lid. If I pinch the skin and pull it away, you notice that it snaps back immediately, and we’d expect this because she is young. Her distraction test is also normal, and therefore we can treat her with Botox for this indication.


Let’s look at Michelle’s nose – she has a typical Asian nose, with a low, flat dorsum and a wide alar base. She is seeking an enhancement here, and by injecting along the dorsum, we can create more central projection, which may have the effect of narrowing the nose by creating better definition.


When Michelle smiles, notice that we can see excessive gum above her teeth, called a gummy smile, or smile with excessive gingival display. This is something that may be amenable to treatment as long as there are no other underlying causes, such as dental or skeletal issues. If I turn Michele to the side, we can see in profile, she has, as we saw from the front, good cheekbone projection and a strong jawline. We can see some chin dimpling that is almost certainly due to an overactive mentalis muscle. We can also see, if I turn her a little bit more, that she has a flat dorsum of the nose and a very closed angle of the nasolabial area, and her current radix is in line with her lower lash line. Ideally, we want to increase the radix to the upper lash line, as this will give the appearance of a longer, sharper nose.


Finally, her nasolabial angle is very acute, probably less than 90 degrees, and we need to increase that to 100 degrees. When we view Michelle from the front, we are aware of some dimpling at the base of her chin at rest. If I get her to activate her mentalis muscle by bringing her lip out, we can see very extensive and diffuse dimpling due to an overactive muscle. This, again, makes her a candidate for Botox.

Anatomy Markings

Let’s now review some of the relevant surface anatomy that will be important when we treat Michelle. If I turn her to the side, you will notice that I have marked out some important structures, and we will begin with the masseter. The masseter is a muscle of mastication, but the primary muscle for that is the temporalis. The masseter has origins from the undersurface of the zygomatic arch and inserts into the mandible. It is a thick muscle with three layers, and if we get the patient to bite, we can palpate it. In Michelle’s case, as she bites, you will actually see the muscle push against my finger because she has quite considerable hypertrophy.


By convention, we draw a line from the tragus to the oral commissure, and when we treat the masseter, it is important to stay below this line so that we can avoid potential damage to more superior structures such as the parotid duct. Also, we get our most important aesthetic benefit by treating the lower pole of the muscle. There may be some components of the parotid gland posterior to the masseter, and in some individuals we can treat the parotid if it is also implicated in excessive widening of the jaw. On the anterior border of the masseter, we can often feel the pulsation of the facial artery which crosses over the mandible at this point. It has a tortuous course to the modiolus and then gives off the inferior labial artery, superior labial artery, and continues up to the ala fossa, giving blood supply to the nose. Here we can also see, at the modiolus, a muscle arising from the masseteric fascia and pulling the mouth corner laterally, and this is the risorius. This can be affected by treatment of the masseter, and can lead to smile asymmetry, so again stay low and stay deep when treating the masseter.


Going back to the blood supply, we can see the superior labial artery gives off a columella branch and the facial artery, before changing to the angular will give off a subnasal and lateral nasal branches to supply the nose. The rest of the blood supply of the nose can be derived from the dorsal artery, which is a branch of the ophthalmic, which also gives off the supratrochlear and supraorbital arteries. It is important to understand the nose therefore has a dual blood supply from external carotid and ophthalmic. Looking at the chin, we can see that the mentalis is a paired muscle, and I typically like to inject this with a single injection point. In Michelle, she has such diffuse activity I will prefer to use two injection points to treat her chin.

Injection site markings and treatments

In treating Michelle’s chin, I have decided to have two injection points – I have marked off the midline, and I will now make the two additional points approximately 2 mm either side of the line. It is important to not venture too far laterally or we may get diffusion into the depressor labii muscle. To inject the chin I insert the Botox deep, all the way onto the bone, and I will inject 2.5 units of Botox in each of the two injection points.

Treatment outcome at 6 weeks

Let’s welcome back Michelle at her 6 week review, we can instantly see that she has had a significant impact from her treatment, with now an obviously thinner and more contoured face due to the fact that we have achieved our jawline contouring. We can also see that at rest her chin appears smoother. Michele underwent filler treatment to her nose, Botox to the infraorbital area, and Botox for gummy smile, mentalis, and jawline contouring. Let’s remind ourselves of what she looked like before, and we can instantly see that her eye aperture has opened up considerably, she has a more elegant nose, and the baseline dimpling she had has gone, but the most important change is the contouring in the jawline. If we look at her face shape, she has gone from square to oval. Now let’s look at her in animation – you can see she has a very nice, natural, pleasing smile, and when she smiles, she can open up the mouth without causing the excessive gingival display that she had pre-treatment. If we now also look at the gap between her nose, we can see that she has got improvement in the are between the nose and the upper lip, and we can also see that the eyes remain open during smile as the hypertrophic orbicularis aspect has been treated.


Finally, from profile, we are already aware of an improvement in her lateral profile, and we need to reminds ourselves of what she looked like before – we can see a higher radix point, a significantly greater nasolabial angle, and also improvement in a chin and jawline contour. All of this has been achieved with combination therapy. Accordingly, Michelle has had a nice and subtle but impactful treatment with dermal filler and botulinum toxin.