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.
Diagnosis & workup
Diagnostics & workup: - MRI with MR venography (MRV): gold standard -- demonstrates thrombus within the cavernous sinus, extent of thrombosis, and surrounding inflammation; superior to CT for soft tissue detail - CT with contrast: shows cavernous sinus enlargement, filling defects, proptosis, extraocular muscle swelling; less sensitive than MRI but faster in emergencies - Blood cultures: positive in 70% of septic CST; obtain before starting antibiotics - CBC with differential: leukocytosis with left shift (bandemia) - Inflammatory markers: ESR and CRP markedly elevated - Lumbar puncture: if meningitis suspected; CSF may show pleocytosis, elevated protein, positive cultures (perform only after imaging rules out mass effect) - D-dimer: may be elevated but non-specific; normal D-dimer does NOT exclude CST - CT angiography: evaluate for carotid artery narrowing or mycotic aneurysm formation