Comparative microanatomy of the lateral wall of the 'cavernous sinus' in humans and the olive baboon.

Despite many studies of the 'cavernous sinus' lateral wall, the anatomy of this area remains controversial. We performed a comparative microanatomical and histoarchitectural study in 14 humans and in 10 nonhuman primates (Papio cynocephalus anubis). Venous channels and cranial nerves were embedded in the 'interperiosteodural space'. The dura propria of the lateral wall could be removed without entering the venous compartment. The oculomotor and trochlear nerves were accompanied by an arachnoidal and dural sheath. The oculomotor nerve sheath stopped under the anterior clinoid process in baboons. The trigeminal ganglion was covered posteriorly with an arachnoid membrane and adhered firmly to the dura propria on lateral and anterior sections. The three branches of the trigeminal nerve had no arachnoid covering, except for arachnoid granulations in humans. In baboons, the oculomotor and trochlear nerves were thicker than in humans, while the ophthalmic nerve was thinner. The abducens nerve belonged to the lateral wall of the sinus in baboons and had no arachnoidal sheath except in the first millimeters of Dorello's canal. After leaving their arachnoidal and dural sheath, the intracavernous cranial nerves acquired a typical peripheral sheath. The venous channels in both species were true dural sinuses. Willis cords and adipose tissue were identified.