What caused the blood clot in Hillary Rodham Clinton's head?
The secretary of state was in and out of the hospital relatively quickly, with so many details of her condition cloaked in secrecy that physicians are left to play armchair quarterback.
But a picture is emerging about what happened. The contours of that picture can help all of us recognize how to spot the warning signs of a blood clot, and just as important, how to prevent one from occurring.
"In her case, there's a 99 percent chance it's dehydration," says Dr. Michael Brant-Zawadzki, a neuroradiologist and executive medical director of the Neurosciences Institute at Hoag Hospital.
Dehydration is one of the prime risk factors for blood clots, seen most commonly in the leg. Vomiting and diarrhea bring on dehydration, which can make the blood "sludgy" and more predisposed to clots, Brant-Zawadzki said. People who travel by air a great deal like Clinton, who has logged nearly a million miles during her four years on the job, are at higher risk for clots due to dehydration and inactivity.
The doctor is not involved in Clinton's care and has no inside knowledge of her treatment, but he said it's extremely rare for a concussion to cause the kind of clot she has. It's possible the clot preceded her fall, not the other way around, he said.
Clinton, 65, was laid low last month by a stomach virus contracted during a trip to Europe. According to the account by the State Department, she experienced vomiting, leading to dehydration. At some point she passed out, hitting her head. On Dec. 13, she was diagnosed with a concussion. A follow-up scan revealed a blood clot on the right side of her head.
On Dec. 30, she was admitted to New York-Presbyterian/Columbia University Medical Center. She was discharged on Jan. 2, accompanied by her husband, former President Bill Clinton, and daughter Chelsea. She's being treated with blood thinners to make sure the clot doesn't get bigger, and she'll be watched closely over the next several months. But she returned to work Monday and likely will remain at her post until a successor is confirmed (Sen. John Kerry has been nominated).
Although Clinton was treated for a blood clot in her leg in 1998, there's little chance a clot like the one that developed in her head will recur, doctors say.
"I know from my own experience, as well as a review of the literature, that there are people who could go on to have complete recoveries," said Dr. Arun Amar, director of the endovascular neurosurgery program at USC's Keck School of Medicine.
Some patients might need to continue to take anti-coagulant medication for long periods, or permanently, which causes a greater risk of bleeding from otherwise minor injuries. Patients also might be urged to avoid certain leafy green vegetables and other foods high in vitamin K, which can interfere with anti-coagulants like Coumadin, the medicine most likely prescribed to Clinton, Amar said. But otherwise, "they can go about their business," added Amar, who was not involved in Clinton's care.
More about the clot
Clinton's clot, called a thrombus in medical terms, is in a vein that runs behind the right ear, between the brain and the skull. There is an identical one on the left side. The veins, called transverse sinuses, are like drainage canals for the blood that leaves the brain. This blood is depleted of oxygen, and makes its way back to the heart, and eventually the lungs, where it picks up more oxygen to nourish the body, including the brain.
Venous blood clots can be dangerous if left untreated: If a vein becomes completely blocked or ruptures, it could damage brain tissue and lead to neurological damage or death. Clinton was lucky because almost everyone has two transverse sinuses. So if one becomes plugged, the other one carries on the flow of blood.
"Some people are born with only one," Amar said, and most never know it because it never becomes an issue.
The brain has so many small blood vessels that many of us probably have suffered ruptures without ever noticing, Amar said.
Other types of clots
Blood coursing through the body needs to be somewhere between thin and thick to move efficiently to the organs that need it. "It's a very delicate balance," Amar said. If it's too thin and runny, a minor injury can cause major bleeding. If the blood is too thick and slow, a person is at risk of an interrupted blood flow, which brings its own set of dangers.
The clot Clinton has differs from the kind that can cause a stroke, a neurological impairment caused by halted blood flow in the brain: Ninety percent of strokes are caused by a blocked vessel, with the other 10 percent caused by a ruptured vessel. Symptoms of a stroke include sudden confusion, loss of speech or vision, or numbness, tingling or weakness in the face, arm or leg, especially on one side of the body.
Clinton had none of those neurological symptoms when her clot was diagnosed.
The most common type of blood clot is called deep vein thrombosis, which originates mostly in the leg or pelvis. This can cause swelling, discoloration or pain in the legs and can lead to disability. But the greatest danger is that a piece of the clot will break off and travel to other parts of the body. If the clot is large enough to prevent blood from traveling from the heart to the lung (called a pulmonary embolism), it can be fatal.
Medications can thin the blood to allow the body to make the clot go away, while others can actively dissolve or break up the clot. More severe cases might require a tool to extract it.
The deep vein thrombosis Clinton had in her leg years ago could mean she's more genetically inclined to have blood that coagulates too much. "You can be a clotter or a bleeder, on the basis of your genetics," Brant-Zawadzki said.
People who travel by plane a great deal are at a heightened risk of clots. The air inside jetliner cabins is often dry. "Our skin loses water and we don't replenish it, which is why we're told to drink plenty of fluids on airplane trips," he said.
Also, sitting for long periods doesn't promote proper blood circulation. Blood flowing from the heart to arteries is under pressure, but there's less pressure inside the veins, which carry blood back to the heart, Brant-Zawadzki said. "We're sitting there, and the blood has to work its way, without help from muscle activity, against gravity from our feet to our heart."
Before her health issues arose, the former first lady and U.S. senator acknowledged being exhausted, and looking forward to taking a year off before deciding what to do next in her life. That might include running for president in 2016.
A hectic schedule, an illness, dehydration and possibly a genetic predisposition might have teamed up to force Clinton to take a break.
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