THURSDAY, Sept. 25 (HealthDay News) -- The risk of stroke has become so low for patients with asymptomatic carotid stenosis (ACS), 95 percent of them would be better off receiving medical therapy rather than surgery or stenting, according to a Canadian-led study.

ACS is narrowing of the carotid (neck) artery that has not yet caused a stroke or transient ischemic attack (TIA). In the United States, one-half to two-thirds of patients who undergo revascularization surgery have no symptoms, according to background information in a University of Western Ontario new release about the study.

The less than 5 percent of ACS patients who might benefit from revascularization can be identified using a procedure called Transcranial Doppler Embolus Detection, which uses ultrasound to detect microemboli in arteries in the side of the head, said study leader Dr. David Spence, director of the Stroke Prevention and Atherosclerosis Research Centre at the university.

Microemboli are small blood clots or chunks of plaque that break off from the narrowing in the carotid artery and go into the brain arteries.

The study included 471 ACS patients -- 199 seen before 2003 and 272 seen after Jan. 1, 2003. Brain scans showed that microemboli were present in 12.6 percent of patients seen before 2003 and in 3.7 percent of patients seen after that. The decline in microemboli was associated with better control of plasma lipids and slower progression of carotid plaque, the study authors said.

"The 96 percent of patients without microemboli have only a 1 percent risk of stroke in the next year, whereas the ones with microemboli have a 14 percent risk of stroke," said Spence, a professor of neurology and clinical pharmacology. "Since the risk of surgery is 4 to 5 percent, patients without microemboli are better off with medical therapy including medications and lifestyle modifications. Only the ones with microemboli would benefit from carotid endarterectomy or stenting."

The study findings are to be presented Sept. 25 at the World Stroke Congress in Vienna, Austria.

More information

The American Heart Association has more about carotid artery disease.