There are two types of strokes, and Ariel Sharon has had both.
A stroke, by definition, disrupts blood flow within the brain. Alan Segal directs the stroke program at Weill/Cornell Medical College in New York City. He says in the most common type of stroke, an ischemic stroke, a blood clot blocks a vessel that delivers blood to the brain. "In that situation, an area of the brain is deprived of blood flow and oxygen, and that small area of brain tissue dies."
Ariel Sharon recovered from an ischemic stroke in December.
Doctors often put patients who've had an ischemic stroke on blood thinning drugs like aspirin for a simple reason. "After a person has had an ischemic stroke, the most likely event is another ischemic stroke," says Segal. And a blood thinner reduces the chance of another clot forming.
After Sharon's first stroke, his doctors discovered a common congenital malformation: a tiny hole in his heart about the size of a small seed. That hole can let blood clots travel from the heart to the brain, another reason to try to keep his blood from clotting.
But there's a second kind of stroke -- a hemorrhagic stroke. "A small area of the brain ruptures and then blood spills out into the tissue of the brain and damages the tissue," says Segal.
A blood thinning agent in this situation is bad. Segal isn't comfortable commenting on Sharon's care, since he doesn't know all the details. But he says Sharon's doctors faced an immediate problem last month -- the ischemic stroke. "That prompted his physicians to use blood thinning agents. He got caught between the yin and yang of too much blood clotting and not enough."
Sharon had seven hours of brain surgery to stop the bleeding and clear out the blood. His doctors Thursday put him into a medically induced coma for a couple of days, to lower the pressure in his brain and allow it to heal. What will happen to anyone after an ischemic and then a hemorrhagic stroke is difficult to predict, says Lewis Morgenstern, who heads the stroke program at the University of Michigan. He says recovery is exceptionally variable. "It depends on the amount of hemorrhage, and how early it's treated, and all the other medical problems." Some patients do quite well, he says. Others die.
Meanwhile, several large ongoing research trials in the U.S. may help doctors deal with cases like Sharon's some day. One study is aimed at determining the value of patching up holes in the heart. Another evaluates fast-acting blood clotting agents for hemorrhagic strokes. And two studies look at different ways of clearing out the blood that has leaked out in a hemorrhagic stroke like the one Sharon just had.