Jawline and platysma neck lifting with botulinum toxin

The anatomy of the platysma muscle

Fig. 1: The posterior and anterior platysmal bands can be specifically treated with botulinum neurotoxin.(A). Schematic illustration of the platysma muscle. The muscle merges into the depressor anguli oris, depressor labii inferioris, mentalis, risorius and orbicularis oris muscles (B). (DAO; depressor anguli oris).

The platysma muscle is a superficial, thin and broad muscle beneath the subcutaneous fat layer that covers most of the neck region (fig. below; A).

Two cadaver specimens of the lateral neck region: platysma and subcutaneous fat layer, the mandibular border marked with a dashed line, with colour marking of the injection plane

The upper part of the platysma, which is involved in facial expression, pulls the cheilion (corner-of-the-mouth point) downwards and widens the lips. The lower part of the platysma muscle pulls the skin of the neck upwards. Innervation is by the cervical branch of the facial nerve, and the blood supply by branches of the submental artery and the suprascapular artery. The platysma muscle arises from the fascial structure of the pectoralis major and ends at the anterior deltoid muscle. The muscle fibres merge superomedially into the depressor anguli oris, the depressor labii inferioris and the lower lip, and laterally form the superficial musculoaponeurotic system. One study found that 85% of the medial platysmal fibres decussate in the submental region. In 43% of subjects, the decussating fibres ran more than 20 mm below the mandibular border.

Injection points and methods for jawline lifting and platysma treatment

For jawline tightening, according to the publication, 2 U per point should be injected (Allergan or Merz units; for Speywood units [Galderma Laboratorium GmbH] it is 5 U). In total, 20 U (Merz units / Allergan units) or 50 Speywood units of botulinum are injected per side. The injection should be given in two lines (two finger-widths apart) (see figure above). To prevent diffusion into the depressor labii inferioris, the injection should be made into the inferior border of the mandible above the marionette line (45° from the cheilion). For jawline tightening, BoNT should be injected subdermally or intradermally.

For the platysmal bands, 2 Allergan units / Merz units or 5 Speywood units are injected per point (green dots). For the injection, 5 points are placed for each band at intervals of about 2 cm along the muscle band. In total, 40 Allergan units / Merz units or 100 Speywood units are used for both sides.

CAUTION:

Overdosing of BoNT into the platysma muscle can cause dysphagia, dysphonia and weakness of the neck muscles through diffusion of BoNT into the underlying muscles. In addition, diffusion into nearby muscles, such as the depressor labii inferioris muscle, can lead to an asymmetrical smile.

Quoted from: Yi et al. Toxins (Basel). 2022 Dec; 14(12): 868. Published online 2022 Dec 10. doi: 10.3390/toxins14120868