Blood clots such as the one for which Secretary of State Hillary Rodham Clinton has been treated can occur for a host of reasons. How serious a clot is depends on where it is and why it formed.
Blood pools and thickens into a clot after an injury or because of a heart problem, clogged arteries or other condition. Clots also can break off and travel to another part of the body.
Clots occur in leg veins (called deep vein thrombosis) or in blood vessels in the neck, brain or lungs. Leg clots are a common risk after someone has been bedridden. Clots are most dangerous when they travel to the lungs, a
potentially life-threatening situation, or to the brain, where they can cause a stroke.
Risk factors such as high blood pressure, diabetes, birth control pills, pregnancy, stroke, recent surgery, prolonged sitting, circulation problems and heart problems — especially an irregular heartbeat called atrial fibrillation — raise the chances of developing a blood clot.
Regarding treatment, a blood thinner such as warfarin (Coumadin) sometimes is prescribed to allow the clot to dissolve by itself over time and prevent new ones from forming.
Clinton’s doctors say the kind of blood clot in the skull such as Clinton’s is relatively uncommon but can occur after an injury such as the fall and concussion with which she recently was diagnosed. Doctors said that an MRI scan revealed a clot in a vein in the space between the brain and the skull behind Clinton’s right ear.
The clot did not lead to a stroke or neurological damage and is being treated with blood thinners, with her release coming with the proper dose worked out.
Clinton had been diagnosed with a concussion Dec. 13 after a fall in her home that was blamed on a stomach virus that left her weak and dehydrated.
The type of clot she developed, a sinus venous thrombosis, “certainly isn’t the most common thing to happen after a concussion” and is one of the few types of blood clots in the skull or head that are treated with blood thinners, said neurologist Larry Goldstein. He is director of Duke University’s stroke center and has no role in Clinton’s care or personal knowledge of it.
The area where Clinton’s clot developed is “a drainage channel, the equivalent of a big vein inside the skull — it’s how the blood gets back to the heart,” Goldstein explained.
It should have no longterm consequences if her doctors are saying she has suffered no neurological damage from it, he said.
Joseph Broderick, chairman of neurology at the University of Cincinnati College of Medicine, also called Clinton’s problem “relatively uncommon” after a concussion.
He and Goldstein said the problem often is overdiagnosed. They said scans often show these large “draining pipes” on either side of the head are different sizes, which can mean blood has pooled or can be merely an anatomical difference.
“I’m sure she’s got the best doctors in the world looking at her,” and if they are saying she has no neurological damage, “I would think it would be a pretty optimistic long-term outcome,” Broderick said.
A review article in the New England Journal of Medicine in 2005 describes the condition, which more often occurs in newborns or young people but can occur after a head injury. With modern treatment, more than 80 percent have a good neurologic outcome, the report says.