The vast majority of patients with narrowed carotid arteries but no warning signs of a stroke can avoid plaque-removing surgery and be treated instead with lifestyle changes and intensive drug therapy, researchers suggest.

The carotid artery in one's neck is the main supplier of blood to the brain.

In a study led by the University of Western Ontario, researchers found that 95 per cent of symptom-free patients with even severely clogged carotid arteries wouldn't benefit from surgery to clean out plaque or from insertion of a stent to open up the blood vessels.

Instead, such patients can be successfully treated to prevent a stroke with "intensive medical therapy," said principal investigator Dr. David Spence, director of UWO's Stroke Prevention and Atherosclerosis Research Centre.

"It's a whole package," Spence said from London, Ont., noting that the therapy includes eating a cardiovascular-friendly Mediterranean diet, quitting smoking and taking certain vitamins, blood pressure medication and the maximum dose of an anti-cholesterol drug.

Spence said the study of 469 patients with narrowed carotids but no other symptoms showed that intensive medical therapy dramatically reduced the number who had tiny clots — called micro-emboli — developing from the plaque and travelling to the brain.

Larger clots can cause a stroke.

Before instituting the therapy at the London stroke clinic in 2003, 12.6 per cent of patients had microscopic clots travelling to the brain, detectable with a helmet-like ultrasound test.

Since therapy began, just 3.7 per cent of patients showed such clot activity.

As well, researchers found the risk of stroke in the patients "went way down," to less than one per cent from four per cent. Heart attack risk in the first year went from 6.5 per cent to zero.

Ultrasound helps detect clots

"What that means is that among patients with asymptomatic stenosis (clogging), the preferred treatment should be intensive medical therapy," said Spence, who presented the findings Thursday at the World Stroke Congress in Vienna.

He said using the ultrasound test — called transcranial Doppler embolus detection — would help doctors determine which patients have microscopic clots and would thus benefit from carotid-cleansing surgery [endarterectomy] or stenting.

That's important to determine because patients without the telltale clots have only a one per cent risk of suffering a debilitating or fatal stroke, while the chance of stroke or death related to the surgery or stenting runs as high as five per cent of patients.

"Since the risk of surgery is four to five per cent, patients without micro-emboli are better off with medical therapy, including medications and lifestyle modifications," Spence said.

"Only the ones with micro-emboli would benefit from carotid endarterectomy or stenting."

Commenting on the research, stroke expert Dr. Julia Hopyan of Sunnybrook Health Sciences Centre in Toronto said the study is important because it suggests a means of helping doctors decide which patients need surgical intervention and which don't.

However, Hopyan said more studies are needed to confirm the results.

The warning signs of a stroke include:

• Sudden numbness or weakness in the face, arm or leg, especially on one side of the body.
• Sudden confusion, trouble speaking or understanding.
• Sudden difficulty seeing.
• Sudden trouble walking, dizziness, loss of balance or co-ordination.
• Sudden, severe headache with no known cause.