The so-called cavernous sinus is a venous pathway, an irregular network of veins that is part of the extradural venous network of the base of the skull, not a trabeculated venous channel. This venous pathway, the internal carotid artery, and the oculomotor cranial nerves cross the medial portion of the middle cranial fossa in an extradural space formed on each side of the sella turcica by the diverging aspects of a dural fold. In this space the venous pathway has only neighborhood relations with the internal carotid artery and the cranial nerves. The space itself must be distinguished from the vascular and nervous elements that it contains. The revision of the anatomy of this region has not only theoretical interest but also important clinical implications.