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Cavernous sinus thrombosis

Photo depiction of the para nasal sinuses

What is cavernous sinus thrombosis?

Cavernous sinus thrombosis is a blood clot that occurs in the cavernous sinus. This is a serious, potentially life-threatening condition, but it is also extremely rare. The cavernous sinuses are hollow areas filled with blood located under the brain, behind the eye sockets. 

Many important nerves and blood vessels pass through this area. 

The key blood vessel that travels through the cavernous sinuses is the internal carotid artery. The jugular vein also travels through the cavernous sinuses. The internal carotid artery carries blood to the brain, while the jugular vein drains blood away from the brain.

When an infection develops in the head or the face, it’s possible for it to spread to the cavernous sinuses. To prevent the infection from spreading to other parts of the body, a blood clot may form in the cavernous sinus.

While this effectively keeps infection from spreading, the clot also blocks blood flowing away from the brain. This can affect the brain, the eyes and the nerves that run through the cavernous sinus infection pathway.

It’s also possible for the blood clot to happen spontaneously, without a pre-existing infection.

SEE RELATED: Subconjunctival hemorrhage (blood in eye) — Causes & treatment

Symptoms of cavernous sinus thrombosis

You may experience cavernous sinus thrombosis symptoms from the onset of the condition, or they may develop over a few days. They may also be experienced in different degrees of severity.

Initial symptoms include:

Over time, symptoms may progress into:

Causes of cavernous sinus thrombosis

Cavernous sinus thrombosis can be septic (it stems from infection) or aseptic (infection isn’t an underlying cause). It’s usually caused by a bacterial infection that spreads from another area of the face or skull.

A region known as the “danger triangle” of the face (from the corners of the mouth to the bridge of the nose) is particularly susceptible to the condition when infection occurs there.

These infections can include:

  • Sinusitis – infection in the area behind the cheekbones and forehead, causing sinus eye pain

  • Abscess – swollen area within body tissue that contains a collection of pus

  • Dental infection – may occur after an extraction, procedure or something as simple as a numbing injection

  • Otitis media – middle ear infection, which is an infection behind the eardrum

  • Maxillofacial surgery – surgery performed on the face, jaw or mouth

  • Acne – rare, but possible that popping a pimple in this zone can cause an infection 

As mentioned, in septic cases of cavernous sinus thrombosis, a blood clot forms to prevent the infection from spreading. The blood clot keeps blood from flowing away from the brain, which can raise pressure within the cavernous sinuses. This rise in pressure can damage the eyes, brain and certain nerves.

Aseptic causes of cavernous sinus thrombosis are much less common than septic causes. In these cases, a blot clot occurs spontaneously rather than to prevent the spread of infection. 

Some causes of aseptic cavernous sinus thrombosis include:

  • Trauma

  • Pregnancy

  • Surgery

  • Inflammatory diseases, such as lupus or Behçet’s disease

  • Complications of COVID-19

SEE RELATED: The COVID-19 vaccine: Will it affect your vision?

Risk factors and complications 

While cavernous sinus thrombosis is very rare, there are some factors that put a person at a higher risk of experiencing it. These risk factors include:

  • Facial infections, such as a sinus infection or periorbital cellulitis

  • Having a disease that makes your blood clot too easily (thrombophilia)

  • Severe dehydration

  • Sickle cell disease

  • Obesity

  • Pregnancy or postpartum

  • Taking oral contraceptives or hormone replacement

  • Immunosuppression

  • Uncontrolled diabetes

  • Steroid use

  • Cancer or chemotherapy 

In addition to raising a person’s risk of occurrence, these risk factors also make an individual more susceptible to experiencing complications associated with cavernous sinus thrombosis. 

Complications include one or more of the following:

  • Third or sixth nerve palsy

  • Diplopia (double vision)

  • Stroke

  • Subdural empyema (collection of pus between the dura mater and the arachnoid mater of the brain)

  • Sepsis

  • Vasospasm (narrowing of blood vessels in the brain)

  • Meningitis

  • Panhypopituitarism (reduced production of all hormones made by the pituitary gland)

  • Brain abscess

  • Blindness

  • Intracranial hypertension (increased pressure in the skull)

SEE RELATED: How does the brain control eyesight?

Treatment of cavernous sinus thrombosis

Treatment of cavernous sinus thrombosis must be administered quickly and in a hospital as it’s a very serious condition. You’ll be closely monitored by medical professionals and given one or more of the following treatments:


Antibiotics are prescribed in most cases of cavernous sinus thrombosis because it’s usually caused by an infection. It’s common for antibiotics to be administered intravenously (through an IV) first. If it’s determined that the cause was not infection, antibiotic treatment will stop.

If infection is the cause, antibiotics may be given for a few weeks to make sure the infection has cleared completely.


If the thrombosis was caused by inflammation, corticosteroids will likely be prescribed to calm the swelling and inflammation in the body.


Also called blood thinners, anticoagulants are used to help dissolve the blot clot responsible for the cavernous sinus thrombosis. They also work by prolonging the blood’s clotting time, which should help prevent another clot from forming.

It’s possible that you’ll have to continue taking the anticoagulants even after you’ve left the hospital. 


If the cause of thrombosis is related to sinusitis or an abscess, surgery may be performed to drain the infection. This helps remove the pus and infection from the area, allowing it to heal.

Draining may be administered using a needle, if the abscess is superficial. It can also be performed with a surgical procedure, when you’re under anesthesia.

When to see a doctor

It’s important to seek medical attention right away if you notice sudden vision changes. Sharp pain or swelling behind or around the eyes, as well as sudden eye bulging, are also signs that immediate medical attention is needed. 

Time is of the essence with this condition. If you start to notice symptoms, it’s crucial to have a doctor examine you while they are still somewhat mild. As symptoms progress, they can become more dangerous and carry a greater risk of complications or lasting effects.

READ MORE: Eye strokes: Retinal artery and retinal vein occlusions

Overview: Cavernous sinus thrombosis. National Health Service. August 2021.

Neuroanatomy, cavernous sinus. Stat Pearls. July 2021.

Cavernous sinus thrombosis. Stat Pearls. July 2022.

Cavernous sinus thrombosis. Merck Manuals. August 2021.

Causes: Cavernous sinus thrombosis. National Health Service. August 2021.

Cavernous sinus thrombosis treatment & management. Medscape. July 2018.

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