PURPOSE:   The anatomical course of the frontal branch of the facial nerve has been described by multiple authors. However, the anatomic tissue plane that the nerve travels in as it traverses across the zygomatic arch into the temporal region varies in the literature.  By some reports the nerve runs in a superficial plane which would render it vulnerable to injury during the high SMAS facelift technique.  An anatomical study including fresh cadaver dissection and histologic evaluation is presented to definitively examine the plane of the frontal branch of the facial nerve as it relates to the fascial layers of the temporal zygomatic region and the zygomatic arch. This is correlated with the senior authors’ experience with the High SMAS facelift technique where a permanent injury to this branch has not been encountered.

METHOD: Eight fresh cadaver heads were included in this study for a total of 16 hemifaces. Twelve 8 cm x 4 cm blocks of tissue were excised full thickness from the temporal zygomatic region overlying the frontal branch of the facial nerve along its course, with specific attention to the nerve and its relation to the zygomatic arch.  These were sectioned and stained with Hematoxylin & Eosin and a Bielchowsky ­­ nerve stain to identify the path of the nerve.  The High SMAS technique was performed on 2 additional fresh cadaver heads, and four additional blocks were obtained in the same fashion to include the area of High SMAS dissection.  These samples were sectioned and stained in the same manner.  All histologic samples were reviewed by the authors and a board certified pathologist.

RESULTS:  The frontal branch of the facial nerve arises from the substance of the parotid gland just caudal to the zygomatic arch.  It courses under the parotidomasseteric fascia, and remains deep below the SMAS up onto the zygomatic arch.  Over the arch, the branch is found below the temporoparietal fascia, running superficial to the deep temporal fascia.  Cranial to the zygomatic arch, the branch begins to turn in a more superficial direction, but remains deep to the temporoparietal fascia.

CONCLUSION:   The frontal branch of the facial nerve is found to run deep to the temporoparietal fascia in and around the zygomatic arch.  It becomes more superficial within the substance of the superficial temporal fat pad, cranial to the zygomatic arch; however, within 2 cm cephalad of the zygomatic arch it remains deep to the temporoparietal fascia.  This result is expected, considering the clinical results seen with the senior author’s technique.  Our findings demonstrate the safety of the High SMAS technique in the area above the zygomatic arch.