Left anterior medial view of the internal carotid artery and cavernous sinus. Portions of the petrous temporal, sphenoid, and clival bones have been removed. The petrous, lacerum and cavernous segments of the internal carotid arteries are exposed. The petrous carotid terminates in the lacerum segment shortly after turning superiorly out of the carotid canal. The cavernous carotid has a posterior genu in the posterior cavernous sinus, and an anterior genu immediately prior to entering the dural rings and the clinoidal segment. The carotid sympathetic plexus is visible as a perivascular plexus on the surface of the internal carotid artery. The dorsal meningeal artery, a branch of the meningohypophyseal trunk that arises from the cavernous segment of the internal carotid artery, enters the dura of the posterior cavernous sinus wall and supplies the clival dura and sixth cranial nerve. The oculomotor (CNIII), trochlear (CNIV), ophthalmic (CNV1), maxillary (CNV2), and abducens (CNVI) nerves traverse the cavernous sinus, though only the abducens and maxillary nerves are highlighted here. (Image courtesy of AL Rhoton, Jr.)