An experimental device that works like a miniature corkscrew can halt devastating strokes by gently pulling blood clots from the brains of victims in the throes of an attack, researchers reported yesterday.

In the largest test of the new technique, doctors extracted blockages in dozens of patients around the country who otherwise would likely have died or suffered serious brain damage. In some cases the procedure dramatically restored their ability to move and talk immediately, the researchers said.

Although the approach requires much more testing and perhaps refinement, a Food and Drug Administration panel will evaluate the device at the end of the month, and could recommend that it be cleared to give doctors a new tool to fight one of the nation's biggest killers.

About 700,000 Americans suffer strokes each year, and nearly 170,000 die, making strokes the third-leading cause of death after heart attacks and cancer. Most strokes occur when a blood clot lodges in a vessel in the brain, cutting off blood flow and killing brain tissue. Those who survive are often left paralyzed and dependent on others for care, making strokes the leading cause of disability.

Currently, the only way doctors can stop a stroke once it has started is to give patients the clot-busting drug tissue plasminogen activator (tPA). But tPA is approved for use only within the first three hours of a stroke, cannot be used on many patients and takes one to two hours to work, often leaving victims brain damaged. So researchers have been trying to develop alternatives, such as destroying clots with ultrasound or lasers or capturing and removing them with tiny baskets.

The new device, known as the Concentric MERCI Retrieval System, has undergone the most extensive testing of the new approaches. The system involves inserting an extremely small tube containing the device into an artery in the groin and then carefully snaking the device through the body until it reaches the clot in the brain.

A nickel and titanium wire then springs into a coiled, corkscrew shape when deployed from the end of the tube, embedding itself into the clot. After snagging the clot, it is pulled back into the tube and a balloon inflates, temporarily blocking blood from flushing the clot back into the brain. The device is then withdrawn, removing the clot and restoring blood flow.

"It's just like pulling the cork out of a wine bottle," said Sidney Starkman, a professor of emergency medicine and neurology at the University of California, Los Angeles, who led the study.

Doctors tried the technique on 114 patients who could not undergo tPA treatment at 25 centers around the country. The device successfully removed clots in 61 of them as long as eight hours after the stroke began, Starkman reported at the American Stroke Association's 29th International Stroke Conference in San Diego.

"This study was primarily a safety study to see whether or not we could even do it. It was pretty amazing that, yes, we could pull clots out of blood vessels in peoples' brains," he said.

In some cases, the results were dramatic, with patients who were paralyzed regaining the ability to talk and move.

Of those patients who had clots removed, 53 percent had very good recoveries, with most being left with no problems or only relatively minor disabilities, Starkman said.