View of the right cavernous sinus and middle cranial fossa floor. The tentorium has been removed with the exception of the tentorial edge, visible immediately adjacent to the trochlear nerve. The petrous temporal bone has been drilled to reveal the facial and vestibulocochlear nerves; the meatal and labyrinthine segments of the facial nerve are visible here proximal to the geniculate ganglion. The greater superficial petrosal nerve arises from the geniculate ganglion and courses anteromedially on the floor of the middle fossa, just superior to the petrous segment of the internal carotid artery (ICA). The superior petrosal sinus connects the cavernous sinus to the transverse sinus and runs along the petrous ridge, separating the middle and posterior fossae. The middle meningeal artery enters the skull base through foramen spinosum and provides vascular supply to the geniculate ganglion before coursing anterolaterally within the dura on the floor of the middle fossa. The oculomotor nerve, arising from the ventral midbrain, enters the cavernous sinus just superior to the trochlear and ophthalmic nerves and lateral to the internal carotid artery. The ICA’s distal dural ring is visible, marking the transition to the intracranial ICA. (Image courtesy of AL Rhoton, Jr.)