Anatomy of the frontotemporal branch of the facial nerve and indications for interfascial dissection

Many studies have been conducted of the surgical anatomy of the frontotemporal branch of the facial nerve (FTBFN). However, very few have addressed the indications for interfascial dissection. When the zygomatic arch needs to be exposed, the interfascial approach is recommended to protect the FTBFN. With the transbasal or subfrontal approaches, however, when a bicoronal skin incision is used, the need for the interfascial approach is not clear. We studied 10 temporal regions (5 cadaveric heads). We dissected the recognized fascial layers of the temporal region and the FTBFN. We performed a histological study in a sixth specimen. We observed the following. 1) The galea and the superficial layer of the deep temporal fascia become fused in a curved line from the lateral orbital border 2.8 cm above the zygomatic arch to a point 3 cm posterior to the inferolateral angle of the orbit. 2) After this transitional area of adherence, the subgaleal loose cellular layer is lost and is replaced by a fibrofatty tissue. 3) The FTBFN in its course above the zygomatic arch runs in this tissue layer without being protected by the galea. 4) Over the superolateral angle of the orbital rim, the galea protects FTBFN, and there are no subgaleal adhesions in that area. Ahove the zygomatic arch, the FTBFN is not protected by the galea. During bicoronal approaches, if only the superolateral angle of the orbital rim needs to be exposed and not the zygomatic arch, there is no need to protect the FTBFN using an interfascial approach.