ARticle | boTulInuM ToxIn A |
Figure 4 47-year-old with deep labiomental furrows and downward projecting corners of the mouth before (A) and after (B) 4 U of onabotulinumtoxin A were injected into the depressor anguli oris bilaterally
subcutaneous tissue and into the muscle, and inject 3–6 u of onabotulinumtoxinA (Figure 4). Advancing the needle too deeply may unavoidably expose some of the posterior fibres of the depressor labii inferioris to the injected toxin. If the depressor anguli oris cannot be palpated, then it should not be treated. Inject precise amounts into the depressor anguli oris; as
the orbicularis oris and depressor labii inferioris are immediately adjacent, unsightly and dysfunctional perioral changes can result if either of these muscles is inadvertently weakened along with the depressor anguli oris. Care should be taken not to inject into the marginal mandibular nerve and facial artery and vein that lie in this vicinity in a bony groove just anterior to the masseter (Figure 4). If the depressor anguli oris is palpated over this bony groove, lift the skin and muscle with the non‑dominant hand before injecting. With this technique the toxin can be injected directly into the fibres of the depressor anguli oris, while avoiding injecting the neurovascular structures of that area16–18
. As the depressor anguli oris is wider at its origin, it is
advisable to inject in this location and not near its insertion close to the corners of the mouth.
sadness. In certain patients, the inferior aspect of the
marionette line contributes to the formation of the pre‑jowl or labiomandibular sulcus.
Dosing The downward angling of marionette lines can be improved by injecting 3–6 u of onabotulinumtoxinA intramuscularly in the centre of the mandible at a point that is most inferior to an imaginary vertical line that passes through the nasolabial sulcus. This point should be approximately 8–10 mm lateral to the oral commissure and 8–15 mm inferior to this point. The appropriate injection point can be identified by palpating someone who is actively contracting the corners of the mouth downward, while pronouncing the letter ‘e’ in an exaggerated fashion10, 15
. Another
manoeuvre to assist in the localisation of the depressor anguli oris is to have the patient bite down, forcibly contracting the jaw muscles. This will contract and enlarge the belly of the masseter, which is a muscle very easily identified by palpation. In most individuals, the depressor anguli oris lies approximately 1–2 mm to 1 cm anterior to the masseter depending on the shape of the jaw. At the point where the contracted and thickened belly of
the depressor anguli oris can be felt, insert the needle perpendicular to the skin surface over the body of the mandible. Advance the needle until it passes through the
Outcomes Injections of botulinum toxin A will relax the depressor anguli oris and permit unopposed elevation of the corners of the mouth by the upward pull of the risorius, levator anguli oris, and the zygomaticus major. When the corners of the mouth are relaxed and elevated by injections of botulinum toxin, a person appears younger and naturally relaxed and pleasant. Depending on the extent and depth of marionette lines, this area is best treated in combination with soft tissue fillers and some form of laser treatment, whether ablative or non‑ablative.
Complications It is vital to inject inferior to and far enough away from the orbicularis oris when treating the depressor anguli oris. otherwise, botulinum toxin A can diffuse focally into the muscle fibres of the orbicularis oris and produce a localised area of inadequate sphincteric closure of the oral cavity, and a segmental inability to pucker the lips. This will result in a localised area of eclabium, an asymmetric smile, drooling, and a change in speech and word pronunciation. Injections given too medially can also weaken the depressor labii inferioris, causing a flattening of the contour of the lower lip and an asymmetric smile. overzealous injections with doses over 6–8 u of onabotulinumtoxinA into the depressor anguli oris will
Treatment implications when injecting melomental folds 1 Inject botulinum toxin A only
when the depressor anguli oris can be accurately palpated and unmistakably identified.
2A lateral platysmal band can 36 ❚ July 2011 |
prime-journal.com
identify the location where the depressor anguli oris and platysma decussate along the inferior border
of the mandible. It is this point of maximal contraction that is the recommended site for an injection.
3Avoid injecting into the
marginal mandibular nerve and facial artery and vein by lifting the skin and soft tissue before injecting.
4Avoid injecting into the
depressor labii inferioris and orbicularis oris by remaining at least 1 cm lateral and 1–1.5 cm inferior to the lateral oral commissure and in the centre of or just above the body of the mandible.
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