By SABIN RUSSELL
San Francisco Chronicle
January 05, 2006
Most strokes - about 85 percent of them - are caused by a clot that blocks the flow of blood to part of the brain, starving vulnerable nerve tissue of oxygen.
Sharon was hospitalized for two days after such a stroke on Dec. 18. That blood clot in his brain, known as an ischemic stroke, made him feel poorly but appeared to cause no lasting damage.
But doctors put the Israeli prime minister on blood-thinning medications to reduce the chances that blood clots would form again while he underwent surgery scheduled for Thursday to repair a small hole found in his heart.
On Wednesday, Sharon was felled by a second type of stroke - a cerebral hemorrhage, or bleeding caused when a blood vessel bursts inside the brain. About 15 percent of strokes are of this nature, and the outlook for these patients is much bleaker than that from strokes caused by blood clots.
The most common cause of cerebral hemorrhages is chronic high blood pressure that is not properly treated. But they can also be caused by the blood-thinning medications taken to prevent the more common, ischemic strokes.
"An intracerebral hemorrhage is the most dangerous type of stroke," said Dr. Claude Hemphill, a University of California associate professor of clinical neurology at San Francisco General Hospital.
About 40 percent of patients with such a stroke die, and nearly all the rest are severely disabled. "They are unable to walk, or to completely care for themselves," said Hemphill.
In an article published in this month's edition of the journal Stroke, Hemphill wrote that the prognosis for cerebral hemorrhage patients who are taking anti-coagulants is worse than for those who are not: 2 out of 3 die.
Without blood thinners, victims of ischemic stroke live at high risk of another one. But taking the drugs poses a risk of at least 1 to 2 percent of a deadlier cerebral hemorrhage - because once a blood vessel bursts, the clotting activity that would contain the problem is blocked by the medication.
"There is no doubt that bleeding in the brain is the most feared complication of warfarin blood-thinning treatment," Hemphill said.
He stressed that he was unaware of any details surrounding Sharon's cerebral hemorrhage, but he said it was common practice to administer the blood-thinning drug warfarin to ischemic stroke patients prior to a surgery.
Of the 700,000 strokes that occur in the United States each year, about 90,000 are cerebral hemorrhages. Strokes can affect people of all ages but are much more common in the elderly.
The gush of blood from a broken artery in the brain causes a buildup of pressure inside the skull, which starves some parts of the brain of oxygen and can damage the brain stem responsible for controlling breathing. Patients may experience a severe headache and become comatose.
About 5 percent of cerebral hemorrhage patients have a better chance of survival because their bleeding occurs in the cerebellum, or back of the brain, instead of in the frontal lobes.
"You can live without part of your cerebellum," said Hemphill. If Sharon's stroke occurred in that part of his brain, and doctors were able to drain it of fluids quickly, he would have a chance of recovery. "Those are very special circumstances, but if that happened, he has a chance," Hemphill said.
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