Dural Sinus Thrombosis and Stroke

Diagnosis and Treatment of Dural Sinus Thrombosis

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If you have been diagnosed with a dural sinus thrombosis, you have probably never heard of it before. Here are answers to your questions about dural sinus thrombosis.

What is a dural sinus?

Like every organ of our body, the brain has a system of veins by which oxygen-depleted blood is channeled back to the lungs, where it can once again be repleted with oxygen. This system of veins is a web of small vessels that receive oxygen-depleted blood from all over the brain.

As the veins travel away from the brain's tissues, they fuse to form larger that gather between the brain and the skull bone to form what is called the "dural sinuses." The dural sinuses are the largest vessels through which blood flows out of the brain, on its way back to the lungs. There are a handful of dural sinuses, and they are called:

  • Superior and inferior sagittal sinus
  • Superior and inferior petrosal sinus
  • Transverse sinus
  • Sigmoid sinus
  • Straight sinus
  • Cavernous sinus
  • Confluence of sinuses

What is dural sinus thrombosis?

A thrombosis is a blood clot. A dural sinus thrombosis is a blood clot inside of one of the dural sinuses.

How can dural sinus thrombosis cause a stroke?

When a blood clot sits inside of one of the brain's sinuses, it causes a backup of blood inside the venous system of the brain, preventing blood from leaving the brain's tissues. At first, this is not a problem, as the small veins have some room to enlarge in order to accommodate for the extra blood.

But as time goes on and new oxygen-rich blood continues to enter the brain's tissues through the arteries, the excess build up of blood begins to cause pressure on the walls of the arteries until they burst, and  bleed inside the brain. This causes a hemorrhagic stroke.

What are the symptoms of dural sinus thrombosis?

One of the known features of dural sinus thrombosis is that it can cause symptoms ranging from a  headache to a sudden and complete paralysis of one side of the body.

More than 90% of people with dural sinus thrombosis complain of severe headaches, while 50% have typical stroke symptoms. Approximately 40% of dural sinus thromboses cause seizures. A person who has a dural sinus thrombosis can also experience memory loss or can stop speaking unexpectedly, depending on the specific dural sinus affected.

When a dural sinus thrombosis only causes headaches and blurry vision, it may be confused with a condition known as benign intracranial hypertesion, also known as pseudotumor cerebri.

How is dural sinus thrombosis diagnosed?

If you go to the emergency room with any of these symptoms, the doctors perform a full neurological exam and typically obtain a CT scan of the brain. The CT scan can show areas of bleeding inside the brain. If there is bleeding, surgery to drain the blood may be an option. However, in order to diagnose a dural sinus thrombosis doctors must perform a test known as magnetic resonance venography or MRV, a diagnostic imaging test which is similar to a conventional MRI, but which only shows blood inside the veins of the brain and the skull.

When MRV is not available, a CT angiography can also be used to visualize the dural sinuses.

How is dural sinus thrombosis treated?

  • Surgical treatments:
    When dural sinus thrombosis causes a large amount of bleeding inside the brain, surgery may be necessary to remove the blood. Bleeding in the brain can lead to compression of vital structures in the brain, causing permanent disability and possibly even death. The procedure for removing blood from the brain is called a decompressive hemicraniectomy. In some cases, increased intracranial pressure from large strokes requires the induction of hypothermia or cooling of the body's temperature, which helps to prevent further damage to the brain. Some experimental treatments are also available in selected hospitals across the country, in which blood clots can be broken up inside the affected sinus using special endovascular thrombolysis techniques.
  • Medical treatments:
    Unless it is medically contraindicated, every person who is diagnosed with dural sinus thrombosis should receive long-term treatment with blood thinners, such as heparin, coumadin, and Lovenox. These medications are given in order to prevent the enlargement of the blood clot that sits inside the affected dural sinus, and to prevent the formation of new blood clots which could lead to new and possibly worse strokes.

Who is at risk of dural sinus thrombosis?

Eighty-five percent of people who are diagnosed with dural sinus thrombosis have a predisposition to forming blood clots. Some of the conditions or events that make people more likely to form blood clots include:

Sources:

Medscape. Cerebral Venous Thrombosis as a Cause of Acute Headache.  http://www.medscape.com/viewarticle/482902_2

Stam, Jan; Thrombosis of the cerebral veins and sinuses; New England Journal of Medicine(2005) 352:17:1791-8

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