Surgical anatomy of the SMAS: a reinvestigation.

There has been considerable disagreement in descriptions of the SMAS. Fresh cadaver dissection, combining anatomic dissection done with the aid of the operating microscope and histologic cross section of facial tissues, was performed in 24 facial halves. Histologic preparation was made on tissue macrosections, each 10 cm in length. Consistent findings include the following: (1) Although the SMAS is closely applied to the superficial surface of the parotid gland, a thin but distinct parotid fascia can be identified between parotid gland and SMAS. (2) The SMAS terminates superiorly within 1 cm below the zygomatic arch, and is not continuous with the temporoparietal fascia. (3) The SMAS in the cheek lies in continuity with the orbicularis oculi muscle of the lower eyelid. (4) Considerable variability exists in the histologic appearance of the SMAS in different facial regions within a single cadaver, as well as in a given facial region between cadavers. Because of its variability, histologic identification of the SMAS should be made in continuity with known reference structures, such as the platysma.