One of two cavities in the skull behind the eyes, which form part of the venous drainage system.
One of the paired cavities within the sphenoid bone, at the base of the skull behind the eye sockets, into which blood drains from the brain, eye, nose, and upper cheek before leaving the skull through connections with the internal jugular and facial veins. Through the sinus, in its walls, pass the internal carotid artery and the abducens, oculomotor, trochlear, ophthalmic, and maxillary nerves.
A channel for venous blood placed either side of the sphenoid bone at the base of the skull behind the eye sockets. Blood drains into it from the eye, the nose, the brain and part of the cheek, and leaves via the internal jugular and facial veins. Sometimes the sinus becomes blocked by a blood clot (thrombus), usually a complication of a nearby bacterial infection. A potentially serious condition, this should be treated with thrombolysis and antibiotics.