In 2010, a team of researchers led by Dr. Thomas Brott of Mayo Clinic in Florida conducted a landmark study comparing two common stroke-prevention treatments.

The National Institutes of Health-funded CREST trial randomly assigned 2,500 patients with partial blockage of the carotid artery to one of two treatments, so-called endarterectomy surgery, or stenting.

The carotid artery supplies blood to the brain, and it can silently develop plaque as we age. That is worrisome because plaque can break apart and cause strokes. Such an event is believed to cause 10 percent of all strokes.

More than 100,000 Americans get one of these two treatments each year, at great cost and a small risk of complications, and a debate over their benefit. The CREST trial found both stent and surgery lowered the risk of stroke from carotid blockage, from 5 percent to 2 percent within five years.

But it found them to be equal in terms of their associated risk of death. Neither treatment extended lifespans longer than the other, and the study didn't examine whether patients who received the treatments outlived people who received no treatment at all.

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It also found small ways the treatments had trade-offs. Both were slightly better than doing nothing, but compared to surgery, the stent slightly raised one's risk of stroke in the next 30 days, and compared to stent, surgery slightly raised one's risk of having a non-fatal heart attack in the next 30 days.

Since then, medications have come along to more easily reduce cholesterol and blood pressure. Also, social changes have have made quitting smoking more appealing. (Quitting smoking is the No. 1 thing a person can do to lower one's risk of heart attack.)

That's why Dr. Guiseppe Lanzino, of Mayo Clinic in Rochester, recently enrolled the first of what are expected to be hundreds of Rochester patients to take part in CREST 2, a second landmark trial that will answer a very important question: Are either of these treatments better than common, inexpensive medications and guided help in quitting smoking?

"Today, for people with 80-90 percent blockage of their carotid artery, if treated (with medicines and lifestyle change), their risk of stroke is kind of low," Lanzino said. "Whether surgery or stent are better than medication alone in preventing future strokes, all this is being questioned by the advancements in medical management."

Three-fourths of adults over age 65 have some blockage of the carotid artery. Seven percent of men over age 80 have a moderate level of blockage, while high blockage of the carotid affects only 1 percent of those over 65. High blockage leads to stroke within five years just 5 percent of the time.

That said, if you are in that 5 percent of adults, you might wish you had known. Blockage of the carotid artery is known to cause cognitive decline as well.

That's why carotid artery blockage screening is big business. Low-cost screening via ultrasound is offered at church events and shopping malls. The United States Preventive Services Task Force says the risks of these screenings outweigh their benefits. But people are clearly being tested and then getting treated, says Lanzino, so clarity as to whether treatment beats close attention from a medical professional is necessary.

No one questions the need for invasive treatments for those experiencing physical symptoms of a blocked artery. If you experience unexplained problems with speech or movements that then go away, you could have a transient stroke and it is likely that you could soon have a stroke. That makes it vital to have a procedure to remove the blockage.

Some patients are reluctant to enter into a randomly assigned trial because they cannot choose the treatment they will receive. Lanzino says the benefits of entering a trial are that patients in a trial normally do better than patients treated outside of a trial, no matter the treatment. He adds that patients assigned to the medication management arm will receive regular help from a health coach, a service not normally covered under insurance. And taking part in a clinical trial can help you help others.

"You help us answer important questions," says Lanzino, "so we can help other patients in the future."

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Get involved

What: The CREST 2 trial will study 2,480 patients in 120 centers in the US and Canada for five years.

Who qualifies: People with high levels of blockage but no symptoms of stroke.

Treatments to be compared: Endartectomy, carotid artery stent, or medical management.

Information: www.crest2trial.org, 844-956-1826