The anatomy of the platysma muscle.

Platysma muscle was studied in 50 cadavers. The principal anatomic variation concerned the medical fibers. In 75 percent of the cases, the fascicles are separate in the suprahyoid region but interlace with those of the opposite side, 1 to 2 cm below the chin. In 15 percent, the fascicles come together at the level of the thyroid cartilage, like a single muscle in the suprahyoid region. In 10 percent of the cadavers, the fibers were separate, but inserted in the subcutaneous muscles of the chin without decussating. The posterosuperior fibers of the platysma always pass behind the angle of the jaw and over important structures, the most significant being the mandibular branch of the facial nerve.