Area adjacent to the sphenoid sinus containing several vital nerves and blood vessels.

A large channel of venous blood creating a “sinus” cavity bordered by the sphenoid bone and the temporal bone of the skull. The cavernous sinus is an important structure because of its location and its contents which include the third cranial (oculomotor) nerve, the fourth cranial (trochlear) nerve, parts 1 (the ophthalmic nerve) and 2 (the maxillary nerve) of the fifth cranial (trigeminal) nerve, and the sixth cranial (abducens) nerve.

A cavernous sinus thrombosis is a blood clot within the cavernous sinus. This clot causes the cavernous sinus syndrome.