Clinical meaning
The cavernous sinuses are paired dural venous sinuses flanking the sella turcica, receiving venous drainage from the face (via the ophthalmic veins and pterygoid plexus) and orbit. Critical structures traverse the cavernous sinus: cranial nerves III (oculomotor), IV (trochlear), V1 (ophthalmic branch of trigeminal), V2 (maxillary branch), and VI (abducens) along the lateral wall, with the internal carotid artery and CN VI passing through the center. Facial and orbital infections spread to the cavernous sinus via the valveless facial and ophthalmic veins, seeding septic thrombosis. Staphylococcus aureus is the causative organism in 70% of cases. The thrombus causes venous congestion, cranial nerve compression, and risk of meningitis, brain abscess, and carotid artery involvement. The valveless communication between the two cavernous sinuses means unilateral infection can rapidly become bilateral.