Editor’s note: This is one in a 10-part series of the top medical research advances of 2016 as determined by the American Heart Association.

For people who suffer a stroke in the small arteries deep within the brain, the best way to prevent another one is to aggressively treat risk factors such as high blood pressure and follow a healthy lifestyle. But that’s not enough for everyone, recent research shows.

Some patients with strokes caused by an intracranial stenosis – a blocked artery in the brain due to plaque buildup or another condition – are at higher risk for a recurrent stroke despite aggressive medical therapy. Research published last March in JAMA Neurology helps predict who those patients are: people who had an old stroke in the same area of the brain, those who weren’t taking a cholesterol-lowering drug called a statin, or people who had a very recent stroke compared to those who had a mini-stroke, known as a transient ischemic attack.

This research development was selected by the American Heart Association as a top 10 heart and stroke science advance of 2016.

Back in 2011, the SAMMPRIS (Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis) trial found that aggressive medical treatment was more effective alone than combined with stenting to prevent strokes in patients with an intracranial stenosis that was causing symptoms. Stents are tiny tubes inserted into a brain artery to help keep blood flowing.

However, about 15 percent of participants in the medical treatment group suffered another stroke or died within three years. Colin Derdeyn, M.D., and the other SAMMPRIS researchers wanted to find out why that rate was so high and who was at greater risk.

“Even though medical treatment was better than stenting, the risk of stroke on medical therapy is very high. Better treatment options are really important,” said Derdeyn, co-principal investigator of SAMMPRIS and chairman of the department of radiology at the University of Iowa School of Medicine. “This paper is an effort to help point us in the right direction for the next steps.”

Intracranial stenosis is responsible for 8 percent to 10 percent of the nearly 800,000 strokes in the United States each year. An estimated 6.6 million American adults have had a stroke.

Among the major findings was that patients with intracranial stenosis had a lower risk of another stroke if they took a statin. It appears that taking statins may help stabilize plaque in the arteries, stopping it from rupturing and lowering patients’ stroke risk, Derdeyn said. Patients who were not taking statins saw a higher risk of stroke, he added.

“It shows that patients with intracranial stenosis should be on a statin,” said Larry B. Goldstein, M.D., chair of the University of Kentucky’s department of neurology who was not involved in the study. In addition, prescribing a statin is the “only potentially actionable intervention” of the three high-risk factors revealed in the analysis, he said.

SAMMPRIS included 227 patients who had a recent stroke or TIA that was attributed to an intracranial artery being 70 percent to 99 percent blocked. Their medical treatment included aspirin, a statin, a short-term blood thinner and lifestyle changes, such as exercise and smoking cessation, to lower blood pressure and cholesterol.

Goldstein is cautious about applying all of the latest findings to practice considering the small number of patients in the retrospective study and a lack of statistical power to determine whether other risk factors, such as being female and having diabetes, were significant. He added that many patients who have had a prior stroke and those with coronary heart disease and other high-risk conditions should already be on a statin.

However, he said such analyses can provide “clues” and help shape future clinical trials for alternative therapies for intracranial stenosis.

Carving out patient subgroups may help researchers identify patients at higher risk of stroke and help develop new therapies to prevent or treat strokes, Derdeyn said. He and others plan to publish further analysis of the SAMMPRIS data on reducing risk factors, such as through exercise, for recurrent strokes.

“We still need better treatments,” Derdeyn said. “While we’ve taken a big step forward with SAMMPRIS, it’s not enough.”