Views of the Parasellar Region. A, Anterior view showing the cavernous sinus after removal of the walls of the sphenoid sinus. The pituitary gland sits between the paired intracavernous carotids and the cavernous sinuses. The medial venous space extends between the pituitary gland and the artery. The anterior intercavernous sinus crosses the anterosuperior surface of the pituitary gland. The ophthalmic artery courses inferolateral to the optic nerve inside the optic canal. B, Posterosuperior view in another specimen showing the right intracavernous carotid, posterior clinoid, and adjacent part of the dorsum sellae removed to expose the medial wall of the right cavernous sinus. The medial wall of the cavernous sinus forms the medial border of the medial venous space on the left side. The anterior intercavernous sinus courses anterosuperior and the posterior intercavernous sinus courses posterosuperior to the pituitary gland in the margins of the diaphragma. The basilar sinus, the largest communication across the midline between the cavernous sinuses sits on the back of the dorsum and opens into the posterior part of both cavernous sinuses. The petrosphenoid ligament, below which the abducens nerve passes to enter the cavernous sinus, extends from the petrous apex to the lower part of the lateral edge of the dorsum sellae. The abducens nerve passes lateral to the posterior vertical segment of the intracavernous carotid. C, Lateral view showing the right cavernous sinus shown in B, A segment of the intracavernous carotid has been removed to expose the medial venous space located medial to the intracavernous carotid and in direct contact with the medial wall of the sinus. D, Right lateral view showing another cavernous sinus. The intracavernous carotid has been removed and the medial venous space partially evacuated to expose the medial wall of the cavernous sinus. The medial wall has two parts: the sellar and sphenoidal. The sellar part is positioned lateral to the pituitary gland. The sphenoidal part lines the carotid sulcus on the body of the sphenoid bone. The sellar portion of the medial wall separates the lateral surface of the pituitary gland from the cavernous sinus. The sphenoidal part of the medial wall is formed by the dura lining the carotid sulcus on the body of the sphenoid bone. The petrous carotid passes below the petrolingual ligament to enter the cavernous sinus. The abducens nerve passes below the petrosphenoid ligament (Gruber’s ligament), which roofs Dorello’s canal, enters the cavernous sinus, and courses lateral to the posterior vertical segment of the intracavernous carotid. E, Enlarged view showing that the dura lining the lower surface of the pituitary gland can be easily separated from the dura lining the sellar floor and that the inferior intercavernous sinus crosses between the two dural layers. The thin dural layer, which forms the sellar part of the medial wall of the cavernous sinus, separates the medial venous space from the pituitary gland. F, Right lateral view of another cavernous sinus showing the nerves and intracavernous carotid removed to expose the medial wall of the cavernous, which has two parts: sellar and sphenoidal. The sellar part covers the lateral surface of the pituitary gland, and the sphenoidal part is formed by the dura lining the carotid sulcus. (Images courtesy of AL Rhoton, Jr.)