Study author Dr. Raffi Topakian of the Academic Teaching Hospital Wagner-Jauregg in Linz, Austria, says asymptomatic carotid stenosis -- a narrowing of the carotid artery found in the neck with few or no symptoms -- increases the risk of stroke.
"There is debate over how to best treat people with asymptomatic carotid stenosis. A procedure called carotid endarterectomy can reduce the risk of stroke, but there are risks and costs involved with the surgery," Topakian says in a statement.
For the study, 435 people with asymptomatic carotid stenosis were tracked for two years. They underwent ultrasound of the carotid artery and of blood vessels in the brain to determine whether two markers for high risk of stroke were present.
The markers were signs of blood clots passing into the brain, and a type of carotid plaque called echolucent plaque, which has a higher fat content than other plaque. Of the participants, 38 percent had echolucent plaque, 17 percent had at least one sign of a blood clot and 6 percent had both markers.
The study, published in the American Academy of Neurology, finds people with the echolucent plaque in their carotid artery were more than six times more likely to have a stroke than people without the plaque and those with both plaque and signs of blood clots were more than 10 times more likely to have a stroke than those without both markers.