Temporalis Muscle Fascial Planes and Dissection. A, The scalp incision rises perpendicular to the zygomatic arch and curves anteriorly toward the midline just behind the hairline. The upper part of the incision lateral to the STL is directed between the galea and temporal fascia. Approximately 4 cm above the lateral orbital rim (interrupted line), the plane of dissection lateral to the STL is deepened using an incision through the superficial layer of the temporal fascia at the upper edge of the interfascial fat pad. This enables the superficial layer of temporal fascia with the facial nerve branches on its outer surface and the adjacent frontal pericranium medial to the STL to be elevated with the scalp flap. B, The galea is separated from the upper part of the outer surface of the temporal fascia, but the galea and superficial layer of temporal fascia below the interfascial incision are not separated. The upper edge of the interfascial fat pad can be seen through the temporal fascia. In the area medial to the STL, the frontal pericranium is separated from the bone. The continuity between the superficial layer of temporal fascia and the frontal pericranium is preserved to maintain the continuity of the nerves to the frontalis muscle, which cross the outer surface of these structures and the STL. C, To fold the frontotemporal scalp flap forward, the deep side of the junction of the superficial layer of temporal fascia lateral to the STL and the frontal pericranium medial to the STL must be separated from their attachments to the STL while the continuity between the frontal pericranium and superficial layer of temporal fascia is maintained. The green arrows show the cut in the superficial layer of temporal fascia at the upper edge of the interfascial fat pad, and the red arrows show the cut along the frontal pericranium. D, Cutting vertically through the junction of the lateral and medial parts should be avoided; the nerves to the frontalis muscle course along the outer surface of these layers, so a vertical cut is likely to cross them. The cut should be directed parallel to the outer surface of the skull at the STL so that it separates the frontal pericranium and superficial layer of temporal fascia from the STL while maintaining their continuity. E, The interfascial-subpericranial flap has been reflected forward. F, The temporalis muscle has been detached and can be reflected posteroinferiorly, leaving a narrow cuff of temporal fascia at the STL for closure. (Images courtesy of AL Rhoton, Jr.)