Cavernous Sinus Thrombosis

What the cavernous sinus is

The cavernous sinuses are two spaces, one on each side of the pituitary gland at the base of the skull, filled with a network of veins. Several important structures pass through them:

• the internal carotid artery
• cranial nerves III, IV and VI, which move the eye
• the first two branches of the trigeminal nerve (V1 and V2), which carry sensation from the forehead, eye and cheek

The two sinuses connect with each other, so infection or clot can spread from one side to the other. Veins draining the face, nose, sinuses and eye run into the cavernous sinus and have no valves, so blood and infection can travel backward into it.

The danger triangle of the face

The area from the corners of the mouth to the bridge of the nose is sometimes called the "danger triangle". Infections here, such as a nasal furuncle, can spread through these veins to the cavernous sinus. This is why squeezing boils on the nose is discouraged. In practice, this complication is now rare thanks to antibiotics.

Causes

Septic (infectious) CST

Most cases. Sources include:

• sinusitis, especially sphenoid and ethmoid sinusitis
• facial skin infections, nasal boils and infected pimples in the danger triangle
• orbital cellulitis
• dental infections of the upper teeth
• ear infections and mastoiditis (less often)

Staphylococcus aureus, including MRSA, causes most cases. Streptococci, anaerobes and, in people with diabetes or weakened immunity, fungi such as Mucor and Aspergillus are other causes.

Aseptic CST

Rarer: after trauma, surgery, with clotting disorders, pregnancy, oral contraceptives or cancer.

Symptoms

Symptoms often begin days after a facial or sinus infection:

• severe headache, usually the earliest symptom, often behind or around the eye
• fever and feeling very unwell
• swelling and redness of the eyelids and around the eye
• bulging eye (proptosis)
• double vision and paralysis of eye movements, often the sixth nerve first (eye cannot move outward)
• drooping eyelid (ptosis)
• numbness or pain in the forehead and cheek
• reduced vision
• spread to the other eye within 24 to 48 hours, a strong clue
• confusion, drowsiness and seizures in advanced cases

Diagnosis

Diagnosis is clinical, confirmed with imaging:

• MRI with MR venography: the most sensitive test, showing the clot and the swollen sinus.
• CT with contrast or CT venography: widely available, shows filling defects and sinus infection.
• Blood cultures and cultures from the infected source.
• Blood tests: blood count, inflammatory markers, clotting tests.
• Lumbar puncture if meningitis is suspected.

It must be distinguished from orbital cellulitis, which usually affects one eye and does not spread to the other side.

Treatment

CST is treated in hospital, often in intensive care, by a team including infectious disease specialists, neurologists, ophthalmologists and ENT surgeons.

• Intravenous antibiotics: started immediately, covering Staphylococcus aureus (including MRSA), streptococci and anaerobes, and adjusted to culture results. Usually continued for 3 to 4 weeks or longer.
• Anticoagulation: heparin is often used to stop the clot from extending, after weighing bleeding risk. Evidence comes mainly from observational studies.
• Surgical drainage: of infected sinuses, dental abscesses or orbital abscesses.
• Antifungal treatment for fungal causes.
• Corticosteroids: sometimes used to reduce cranial nerve inflammation, but their role is debated.

Complications

• spread to the other cavernous sinus and other brain veins
• meningitis and brain abscess
• stroke from carotid artery involvement
• permanent vision loss or double vision
• pituitary damage causing hormone problems
• sepsis
• death

Outlook

Before antibiotics, CST was almost always fatal. Mortality today is reported at roughly 10 to 30%, and a significant proportion of survivors have lasting problems such as double vision, vision loss or nerve damage. Early recognition and treatment improve outcomes.

Prevention

• Do not squeeze pimples or boils on the nose or upper lip.
• Treat facial and nasal skin infections promptly.
• See a doctor for sinusitis with severe headache, high fever or eye swelling.
• Keep up dental care and treat tooth abscesses quickly.
• Control diabetes.

Frequently asked questions

What are the first signs of cavernous sinus thrombosis?

The earliest sign is often a severe, worsening headache, usually around or behind one eye, with fever. Eye swelling, a bulging eye, double vision and a drooping eyelid follow. Symptoms spreading to the other eye are a strong warning sign.

Can a pimple on the nose cause cavernous sinus thrombosis?

Very rarely. Veins from the nose and upper lip drain toward the cavernous sinus, so an infected pimple or boil there can, in rare cases, spread infection backward. Avoid squeezing such spots and seek care if redness spreads or the eye swells.

Is cavernous sinus thrombosis curable?

Yes, many people recover with prompt IV antibiotics, treatment of the infection source and often blood thinners. However, it remains serious, with significant risk of death or lasting vision and nerve problems, so early treatment is critical.

How is cavernous sinus thrombosis different from orbital cellulitis?

Both cause fever, eye swelling and painful eye movement. Orbital cellulitis usually stays on one side. Cavernous sinus thrombosis often spreads to the other eye, causes more cranial nerve problems and severe headache, and is confirmed with MRI or CT venography.