Cavernous sinus

At a glance

English

Cavernous sinus

Latin (TA2)

Sinus cavernosus

System

Vein

Region

Whole body

Side

Paired, left and right

About the cavernous sinus

The cavernous sinus is a small blood-filled compartment, roughly one by two centimetres, lying on the side of the body of the sphenoid bone, next to the sella turcica. It counts among the dural venous sinuses but is not a simple tube; it is a trabeculated space, or a plexus of thin-walled veins, enclosed by dura. The pituitary gland and the sphenoidal air sinus lie medial to it, the temporal lobe and uncus lateral. The superior orbital fissure lies in front and the petrous apex behind.

Several structures run through or alongside it. In its lateral wall, from top to bottom, lie the oculomotor nerve, the trochlear nerve, and the ophthalmic and maxillary divisions of the trigeminal nerve; the maxillary nerve sits low, just outside the sinus proper, and leaves through the foramen rotundum. Within the sinus run the internal carotid artery, forming its S-shaped carotid siphon and wrapped in its sympathetic plexus, and the abducens nerve, lateral to the artery. Apart from the maxillary nerve, all of these pass forward into the orbit by way of the superior orbital fissure. The optic nerve passes above and medial to the sinus into the optic canal.

Blood enters the sinus through the two ophthalmic veins, superior and inferior, and through the sphenoparietal sinus and the superficial middle cerebral and inferior cerebral veins. The two sinuses are linked by intercavernous sinuses around the pituitary and connect behind with the basilar plexus. Outflow runs chiefly along the two petrosal sinuses, superior and inferior, to the sigmoid sinus and internal jugular vein, with further outflow through emissary veins, especially through the foramen ovale, to the pterygoid plexus.

This is the only place where an artery passes right through a venous space. A tear of the carotid here gives a carotid-cavernous fistula, with a bulging, pulsating eye. A pituitary tumour can grow sideways into the sinus, and tumours, aneurysms, inflammation and infection can all cause cavernous sinus syndrome: weakness of eye movements, loss of sensation over the forehead and cheek, and sometimes Horner's syndrome. A full lesion paralyses all eye movements and leaves a fixed, wide pupil. Infection from the central face, the so-called danger triangle, can spread along the facial and ophthalmic veins and produce cavernous sinus thrombosis, a medical emergency.

Course and drainage

Begins at

Receives both ophthalmic veins, the sphenoparietal sinus and the superficial middle and inferior cerebral veins.

Drains into

Drains by the two petrosal sinuses towards the internal jugular vein, and via emissary veins to the pterygoid plexus.

Drains

Drains the orbit, part of the cerebral cortex and the region round the pituitary, and carries the internal carotid artery and the nerves to the orbit.