Cavernous sinus thrombosis is a very rare but serious condition that involves a blood clot in your cavernous sinuses. The cavernous sinuses are hollow spaces located at the base of your brain and behind your eye sockets. They allow major veins to drain blood from your brain and face.

The blood clot typically forms when an infection that starts in your face or head moves into your cavernous sinuses. Your body creates a blood clot to try to stop the infection from spreading. However, the clot can restrict the flow of blood from your brain, potentially damaging your brain, eyes, or nerves.

The symptoms of cavernous sinus thrombosis tend to show up about 5 to 10 days after you develop an infection on your face or in your head.

Possible symptoms include:

  • severe headache or facial pain, especially around your eyes
  • fever of 100.4°F (38°C) or above
  • blurred or double vision
  • eye muscle paralysis, leading to drooping eyelids or difficulty moving your eyes
  • protruding or swollen eye
  • swelling in or around eyelid
  • confusion
  • seizures

In cavernous sinus thrombosis, a blood clot develops in the sinuses behind your eyes or at the bottom of your skull after an infection. The clot is meant to prevent the infection from spreading, but it often blocks the blood flow out of your brain.

Several types of infection can cause this, including:

  • sinusitis, an infection of the sinuses behind your cheeks and forehead
  • abscesses or boils
  • dental infections
  • ear infections
  • infections following a facial procedure or surgery

More specifically, 70 percent of infections leading to cavernous sinus thrombosis involve the bacteria Staphylococcus aureus.

However, it doesn’t always involve a bacterial infection. Other potential causes include:

Cavernous sinus thrombosis is sometimes misdiagnosed because it’s so rare. Your doctor will likely review your medical history and any recent infections you’ve had. Be sure to tell them about any infections they might not know about. If they suspect there might be a blood clot, they may use an MRI scan or CT scan to look at your sinuses.

Depending on what they see in the scans, they may also do a blood culture test. This involves taking a small sample of your blood and testing it for bacteria. Depending on your symptoms, your doctor may also request a cerebrospinal fluid culture to check for meningitis, which sometimes occurs alongside cavernous sinus thrombosis.

Cavernous sinus thrombosis is a serious condition that usually requires high doses of intravenous (IV) antibiotics often for several weeks. You may need to stay in the hospital while receiving IV antibiotics.

Some common antibiotics used to treat cavernous sinus thrombosis include:

  • nafcillin
  • metronidazole
  • cephalosporin
  • vancomycin

Depending on the type of infection, you may need a combination of different antibiotics.

You might also be given a blood thinner, such as heparin, to stop or prevent blood clot development. Blood thinners could cause additional bleeding in your skull or cause the blood clot to spread to other parts of your body. Your doctor will weigh the risks and benefits based on the severity of your condition.

In some cases, your doctor might also prescribe corticosteroids to help reduce swelling and inflammation around your eyes.

Cavernous sinus thrombosis can lead to severe complications. About 1 in 3 cases are fatal, so it’s very important to tell your doctor right away if you think you have it, especially if you’ve recently had an infection.

Even with early, effective treatment, other possible complications include:

  • Vision issues. About 1 in 6 people will have permanent vision problems.
  • More blood clots. Having cavernous sinus thrombosis can increase your risk of developing blood clots elsewhere, such as your legs or lungs.
  • Spreading infection. If your infection spreads beyond the cavernous sinuses, it can lead to meningitis, an infection of the protective membrane surrounding your brain. It could also cause sepsis, a serious type of blood poisoning.

Cavernous sinus thrombosis is a very serious condition that can be life-threatening. However, it’s also relatively rare. If you’ve recently had a severe head injury or an infection in your head, keep an eye out for any of the symptoms listed above.

If you have an autoimmune condition or are at a higher risk of developing blood clots, you should also be aware of signs of cavernous sinus thrombosis. The sooner you recognize the symptoms, the sooner you can start IV antibiotics and prevent the infection from spreading.