Cavernous sinus thrombosis (CST) is the formation of a blood clot within the cavernous sinus, a cavity at the base of the brain which drains deoxygenated blood from the brain back to the heart. This is a rare disorder and can be of two types–septic cavernous thrombosis and aseptic cavernous thrombosis. The most common form is septic cavernous sinus thrombosis. The cause is usually from a spreading infection in the nose, sinuses, ears, or teeth. Staphylococcus aureus and Streptococcus are often the associated bacteria. Cavernous sinus thrombosis symptoms include: decrease or loss of vision, chemosis, exophthalmos (bulging eyes), headaches, and paralysis of the cranial nerves which course through the cavernous sinus. This infection is life-threatening and requires immediate treatment, which usually includes antibiotics and sometimes surgical drainage. Aseptic cavernous sinus thrombosis is usually associated with trauma, dehydration, anemia, and other disorders. Signs and symptoms The clinical presentation of CST can be varied. Both acute, fulminant disease, and indolent, subacute presentations have been reported in the literature. The most common signs of CST are related to anatomical structures affected within the cavernous sinus, notably cranial nerves III-VI, as well as symptoms resulting from impaired venous drainage from the orbit and eye. Classic presentations are abrupt onset of unilateral periorbital edema, headache, photophobia, and bulging of the eye (exophthalmos). Other common signs and symptoms include: Ptosis, chemosis, cranial nerve palsies (III, IV, V, VI). Sixth nerve palsy is the most common. Sensory deficits of the ophthalmic and maxillary branch of the fifth nerve are common. Periorbital sensory loss and impaired corneal reflex may be noted. Papilledema, retinal hemorrhages, and decreased visual acuity and blindness may occur from venous congestion within the retina. Fever, tachycardia and sepsis may be present. Headache with nuchal rigidity (neck stiffness) may occur. One or both pupils may be dilated and sluggishly reactive. Infection can spread to contralateral cavernous sinus within 24–48 hours of initial presentation. Cause Septic CST most commonly results from contiguous spread of infection from a nasal furuncle (50%), sphenoidal or ethmoidal sinuses (30%) and dental infections (10%). Less common primary sites of infection include tonsils, soft palate, middle ear, or orbit (orbital cellulitis). The highly anastomotic venous system of the paranasal sinuses allows retrograde spread of infection to the cavernous sinus via the superior and inferior ophthalmic veins. It was previously thought that veins in the area were valveless and that this was the