Temporalis Muscle Fascial Planes and Dissection. A, The interfascial dissection starts approximately 4 cm above the lateral orbital rim at the upper edge of the interfascial fat pad (interrupted line). B, The layers converging on or attaching from the lateral side to the STL are, from superficial to deep, the superficial and deep layers of temporal fascia enclosing the interfascial fat pad, the temporalis muscle, and the temporal periosteum. The frontal pericranium is the only layer medial and attached to the STL. In the interfascial-subpericranial approach, to fold the scalp flap downward over the orbital rim, the superficial layer of temporal fascia lateral to the STL and the pericranium medial to the line must be separated from their attachment to the STL while maintaining the continuity of these 2 layers with the nerves on their outer surface across the STL. The incision in the superficial layer of temporal fascia has been extended across the frontal pericranium 4 cm above the lateral orbital rim. C, Enlarged view of B. D, Schematic view of the layers attached along the STL: superficial (red) and deep layer (green) of temporal fascia, interfascial fat pad (purple), temporalis muscle (yellow), temporal periosteum (light blue), and frontal pericranium (dark blue). There is a tendency to want to cut vertically across the junction of the frontal pericranium and superficial layer of temporal fascia at the STL, but an incision directed vertically across this junction at the STL will cut the nerves to the frontalis muscle. The cut separating the scalp flap from the STL should extend parallel to the outer surface of the skull while maintaining the continuity between the frontal pericranium medially and the superficial layer of temporal fascia laterally. E, The junction of the superficial layer of temporal fascia and frontal pericranium is being separated from the STL using a cut parallel to the surface of the skull. F, The interfascial-subpericranial flap has been folded downward. (Images courtesy of AL Rhoton, Jr.)