On each side of the sella turcica, because of the existence of vascular and nervous elements, the two aspects of the parasellar segment of the tentorium cerebelli diverge and with the wall of the sphenoid bone form an extradural lodge. In this space are included a venous pathway (the cavernous sinus of the classics), the internal carotid artery and the three oculo-motor cranial nerves. The venous pathway is a plexus of small sized veins, mainly draining the orbital blood, and has neighborhood relations with the carotid. The morphology of the region and the relations of the internal carotid artery and the cranial nerves with the dura propria are the result of the embryonnic development of the brain and the formation of the anterior and middle cerebral fossae. In the parasellar space the cranial nerves have a dural sheath as well as a leptomeningeal one. Nerves III and IV are very close to the lateral wall explaining its multilayered aspect. The internal carotid artery, extradural in its parasellar segment, at the level of the anterior clinoid process, is involved by dura propria to become intradural (the artery does not pierce the dura). Because of the adhesion of the dura propria to the intracranial periosteum the artery is attached to the bone whereas in its extradural and intradural segments it has some mobility. Recent studies have confirmed and completed this topographical concept, first presented in 1949, allowing successful approaches to vascular and tumorous lesions considered inoperable.
Abducens Nerve Arachnoid