The cavernous sinus within the human head is one of the dural venous sinuses creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica. Structure The cavernous sinus is one of the dural venous sinuses of the head. It is a network of veins that sit in a cavity. It sits on both sides of the sphenoidal bone and pituitary gland, approximately 1 × 2 cm in size in an adult. The carotid siphon of the internal carotid artery, and cranial nerves III, IV, V (branches V1 and V2) and VI all pass through this blood filled space. Both sides of cavernous sinus is connected to each other via intercavernous sinuses. The cavernous sinus lies in between the inner and outer layers of dura mater. Nearby structures Above: optic tract, optic chiasma, internal carotid artery. Inferiorly: foramen lacerum, and the junction of the body and greater wing of sphenoid bone. Medially: pituitary gland (hypophysis cerebri), and sphenoidal air sinus. Laterally: temporal lobe with uncus. Anteriorly: superior orbital fissure, and the apex of the orbit. Posteriorly: apex of petrous temporal bone. Venous connections The cavernous sinus receives blood from: Superior and inferior ophthalmic veins Sphenoparietal sinus Superficial middle cerebral veins Inferior cerebral veins Blood leaves the sinus via superior and inferior petrosal sinuses as well as via the emissary veins through the foramina of the skull (mostly through foramen ovale). There are also connections with the pterygoid plexus of veins via inferior ophthalmic vein, deep facial vein and emissary veins. Contents Apart from the blood which passes through a venous sinus, several anatomical structures, including some cranial nerves and their branches, also pass through the sinus. Structures within the outer (lateral) wall of the compartment from superior to inferior: Oculomotor nerve Trochlear nerve Ophthalmic and maxillary branches of the trigeminal nerve Structures passing through the midline (medial) wall: Abducens nerve Internal carotid artery accompanied by the internal carotid plexus These nerves, with the exception of CN V2, pass through the cavernous sinus to enter the orbital apex through the superior orbital fissure. The maxillary nerve, division V2 of the trigeminal nerve travels through the lower portion of the sinus and exits via the foramen rotundum. The maxillary branch passes external to, but immediately adjacent to, the lateral wall of the sinus. The optic nerve lies just