Infections of the midface or paranasal sinuses may spread to the cavernous sinus, resulting in thrombosis and inflammation of associated structures, including the internal carotid artery and cranial nerves III, IV, V, and VI. This manifests clinically as headache, photophobia, and periorbital edema with proptosis, ptosis, chemosis, and ophthalmoplegia. Without treatment, this life-threatening infection will spread to the contralateral cavernous sinus via communicating veins within 24–48 hours. Signs of meningeal irritation may appear. Systemic signs and symptoms of sepsis may also occur.

The most common infectious agents are Staphylococcus aureus and streptococci, although gram negative organisms, anaerobes, and fungi, such as Aspergillus, may also cause cavernous sinus thrombosis. Complications of cavernous sinus thrombosis include stroke, subdural empyema or brain abscess, meningitis, septic emboli to the lungs, blindness, pituitary insufficiency, or death. Many survivors suffer permanent sequelae such as cranial nerve palsies.