We congratulate Dr. Visconti and Dr. Salgarello for their letter, as it nicely complements our article entitled “Anatomical Considerations to Prevent Facial Nerve Injury.”1 Their comments and figures help further clarify our attempt to improve understanding of facial nerve anatomy and the planes of dissection that are safe and help avoid injury.
The complexity of facial nerve branches and their variable course can be appreciated in the elegant dissection performed by Dr. Visconti and Dr. Salgarello. Their anatomical figures further highlight the importance of understanding safe planes of dissection, the relative constant, as opposed to the complex and variable two-dimensional course of facial nerve branches. For instance, with regard to the frontal branch, there are two planes of dissection that are safe, as one can appreciate in their figure. One can safely proceed either from a deep plane down onto the superficial leaf of the deep temporal fascia or from a superficial plane just above the temporoparietal fascia. This leaves the nerve safely located in what is referred to as the mesotemporalis in their figure. At the level of the zygomatic arch, the superficial leaf of the deep temporal fascia attaches to the arch, and surgeons should move to a subperiosteal plane when working from superior to inferior to make sure they are deep to the nerve, which is just superficial to the periosteum at that level. Otherwise, when moving from inferior to superior, one can stay within a plane just deep to the superficial musculoaponeurotic system that can be dissected off the parotid fascia, and the nerve will be safely maintained deep to that dissection. Having a good understanding of the third dimension of depth of the facial nerve, especially as one moves across different positions along the face, is of paramount importance to avoid injury.
Another interesting finding from the letter by Dr. Visconti and Dr. Salgarello is the comment on cervical branch anatomy and that there is often an ascending branch that contributes innervation to lower lip depressors. Their figure clearly depicts two branches of the cervical branch nerve, one listed as an ascending branch (ab) and another as the descending branch (db). With each dissection, it is difficult to ascertain what defines an ascending cervical branch versus a marginal mandibular branch. Who is to say that what they labeled as the cervical branch-ab is not a mandibular branch, and vice versa? Nevertheless, this is of no clinical significance. The importance of the nerve is by what it innervates. Even the innervation of the platysma, however, is of importance, as paralysis of the platysma itself can lead to an asymmetric smile, as it is well known that the platysma often inserts above the jaw line and therefore can contribute to lower lip depression, particularly in those with a full denture smile. Any asymmetry with animation is disturbing for the patient and surgeon and ideally should best be avoided even when it is only temporary. Improved understanding of facial nerve anatomy is an important first step in achieving such a goal. We encourage and applaud efforts such as that by Drs. Visconti and Salgarello to help shed further light on the complex anatomy of the facial nerve.
The authors have no financial interest to declare in relation to the content of this communication. Dr. Rohrich is a volunteer member of the Allergan Alliance for the Future of Aesthetics and receives instrument royalties from Eriem Surgical, Inc., and book royalties from Taylor and Francis Publishing.
Jason Roostaeian, M.D.
Department of Plastic Surgery
David Geffen School of Medicine at the
University of California, Los Angeles
Los Angeles, Calif.
James Stuzin, M.D.
Coconut Beach, Fla.
Rod J. Rohrich, M.D.
Department of Plastic Surgery
University of Texas Southwestern Medical Center
1. Roostaeian J, Rohrich RJ, Stuzin JM. Anatomical considerations to prevent facial nerve injury. Plast Reconstr Surg. 2015;135:1318–1327.