Left trigeminal nerve and cavernous sinus wall. The right border of the image presents several midline structures. Anteriorly is the sella turcica containing the pituitary gland. It is covered by the diaphragma sellae that contains an opening through which the infundibulum or pituitary stalk passes, connecting the hypothalamus with the posterior pituitary. Laterally is a cut view of the left internal carotid artery and posterior to this, the posterior clinoid process of the dorsum sellae. Posterior to the dorsum sellae is the midline basilar artery in front of the pons and the superior cerebellar and, terminal, posterior cerebral branches. Lateral to the body of the sphenoid bone is the cavernous sinus between layers of the dura mater. The lateral wall (meningeal) layer has been stripped to expose the oculomotor and trochlear nerves in its superior portion. Both of these arise from the midbrain. The trigeminal nerve emerges from the anterolateral surface of the pons. The motor root (portio minor) is anterior and medial to the larger sensory root (portio major). The trigeminal nerve crosses the prepontine cistern and passes between the petrous apex and the tentorium cerebelli to enter and expand within Meckel's cave as the trigeminal ganglion. The entry point opening is the porus trigeminus. The anterior intercavernous sinus can be seen in the anterior diaphragma sellae connecting the right and left cavernous sinuses. (Image courtesy of AL Rhoton, Jr.)