Cavernous sinus thrombosis

Cavernous sinus thrombosis is a rare and life-threatening condition in which a blood clot develops in the cavernous sinuses.

The cavernous sinuses are a series of hollow spaces located under the bottom of the brain, behind each eye socket. A major blood vessel called the jugular vein carries blood through the cavernous sinuses away from the brain.

Symptoms of a cavernous sinus thrombosis include:

  • a sharp and severe headache
  • swelling and bulging of the eyes
  • eye pain that is often severe

Read more about the symptoms of cavernous sinus thrombosis.

When to see your GP

You should always contact your GP if you are experiencing a persistent and severe headache you have not had before, or if you develop swelling of the eyes or severe eye pain.

While it is highly unlikely to be the result of a cavernous sinus thrombosis, a persistent headache is a symptom that usually requires further investigation.

After an examination of your symptoms, you may be referred for several tests, including a computerised tomography (CT) scan, a magnetic resonance imaging (MRI) scan and blood tests.

Why does cavernous sinus thrombosis happen?

Most cases of cavernous sinus thrombosis occur when a bacterial infection in another part of the skull or face spreads into the cavernous sinuses.

In around 7 out of every 10 cases, staphylococcal (staph) bacteria, which can cause sinusitis and boils, is responsible. It often appears a few days before cavernous sinus thrombosis.

A blood clot then forms inside the cavernous sinuses in an attempt to prevent the infection from spreading further into the body.

This blood clot places the brain under increasing pressure by restricting the blood flow, which can damage the brain, eyes and central nervous system.

Read more about the causes of cavernous sinus thrombosis.

How is cavernous sinus thrombosis treated?

Cavernous sinus thrombosis needs treatment in hospital.

The main treatment for the condition is antibiotics, which are normally given through a drip into a vein in the arm. This treatment usually lasts at least three to four weeks.

Despite some uncertainty about their use, you may also be given additional treatment with anticoagulant medication (to dissolve and prevent blood clots) or steroid medication (to reduce any swelling).

Most people will need to stay in hospital for several weeks or even months before they are well enough to go home.

Read more about treating cavernous sinus thrombosis.


Cavernous sinus thrombosis is an extremely serious condition. Even with prompt treatment, as many as one in three people with the condition die.

Around 1 in 10 people who survive will develop long-term health problems as the result of damage to their brain, such as persistent headaches and fits, or some degree of visual impairment

Read more about the complications of cavernous sinus thrombosis

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