The most common cause of cavernous sinus thrombosis is when an infection in another part of the skull, such as the eye, nose or ears, spreads into the cavernous sinuses.
The two infections most commonly associated with a cavernous sinus thrombosis are:
- sinusitis, which is an infection of the small, air-filled cavities behind the cheekbones and forehead
- a boil, which is a large painful pus-filled swelling or lump that develops on the face
Attempting to squeeze a boil can sometimes result in an infection spreading into the cavernous sinuses.
The immune system will create a blood clot to prevent the infection from spreading further into the body.
However, the clot will usually block the flow of blood away from the brain through the jugular vein. This blockage increases the pressure on the brain and blood can also flow back up into the brain, both of which can damage the brain, as well as the eyes and the central nervous system.
In addition, the immune system, despite the blood clot, is normally ineffective in preventing the spread of infection out of the skull and into the rest of the body.
So the infection often spreads through the blood stream causing multiple organ failure, which is known as blood poisoning or sepsis.
Other causes
Other less common causes of cavernous sinus thrombosis include:
- A severe head injury that results in a blood clot. This is thought to be the second most common cause.
- An infection spreading from a tooth or gum infection .
- Having a health condition or other underlying factor that makes you more prone to blood clots - the most common being pregnancy.
- People who have conditions that cause inflammation (swelling) inside their body, such as lupus or Behçet’s disease, can occasionally develop blood clots.
- Some types of medication, such as the contraceptive pill or the medications used in hormone replacement therapy, can cause blood clots as a side effect, though this is very rare.
