Trigeminal ganglion in the floor of the middle cranial fossa.  The trigeminal nerve arises from the pons on the right of the image and crosses the petrous apex of the temporal bone to reach the floor of the middle cranial fossa where it expands as the trigeminal ganglion.  The ganglion is located within a dural pouch called Meckel’s cave at the posterolateral aspect of the cavernous sinus.  The dura mater forming Meckel’s cave has been removed to reveal the ganglion.  Superior to the ganglion in this image the oculomotor nerve (CN III) and trochlear nerve (CN IV) are seen traveling anteriorly within the cavernous sinus and entering the orbit via the superior orbital fissure.  The lateral wall of the cavernous sinus is formed by the meningeal layer of dura, which has been removed to reveal these nerves.  The petrous portion of the internal carotid artery can be seen entering the cavernous sinus deep to the trigeminal ganglion. (Image courtesy of AL Rhoton, Jr.)