Trautmann’s triangle and the carotid sheath entering the skull base. For orientation, the left side of the image is anterior, and the infratemporal fossa is exposed. The zygomatic process of the temporal bone articulates with the mandible in the mandibular fossa. The tympanic part of the temporal bone has been drilled to reveal the internal carotid artery, internal jugular vein, and vagus nerve within the carotid sheath. Immediately superior to the divergence of the jugular bulb and ICA is the mesotympanum, with the labyrinth medial (deep, in this image). Trautmann’s triangle represents the window to the posterior fossa from the mastoid cavity, and is bordered superiorly by the superior petrosal sinus, posteriorly by the sigmoid sinus, and anteriorly by the semicircular canals. The stylomastoid foramen has been opened, exposing the facial nerve and the stylomastoid artery - a branch of the posterior auricular artery. The chorda tympani branch of the facial nerve runs up and over the mesotympanum as it courses to ultimately join the lingual nerve. (Image courtesy of AL Rhoton, Jr.)