The Food and Drug Administration changed the label for the stent, called the Wingspan system, after outside advisers to the agency in March recommended the device should not be used in most people.

Stryker's stent is already not widely used. The company has said it sells less than 2,000 devices each year.

But outside observers of the FDA were looking for the agency to act after a study showed the Wingspan stent caused more harm than anti-clotting drugs when used in stroke patients.

Stroke is the fourth-leading cause of death and a leading cause of disability in the United States. Blocked brain arteries caused by the build-up of fatty deposits called plaque account for more than 50,000 of the 795,000 strokes occurring in the United States each year.

Wingspan is meant to open blocked arteries in the brain caused by plaque, when clot-dissolving drugs like aspirin and Plavix do not work. The stent is supposed to improve blood flow and prevent people who have already had a stroke from having another one.

Plavix, known generically as clopidogrel, is made by Bristol-Myers Squibb Co and Sanofi SA.

But a study published in the New England Journal of Medicine showed stroke patients who were treated with both drugs and the Wingspan stent had more than twice the rate of strokes and death in the month after surgery compared to those treated with drugs alone. Researchers had expected the use of stents to help patients.

Some of the FDA's advisers called for the device to be withdrawn from the market, where it has been sold since 2005.

But the FDA said the stent could still be useful for patients who have had multiple strokes despite taking medications, and have not had any new stroke symptoms within seven days before getting treated with Wingspan.

Currently, there are no other options to treat these high-risk stroke patients.

"After careful consideration of available safety information, the FDA believes this device should remain available for this specific subgroup of patients who have exhausted other options," Dr. Jeffrey Shuren, head of the FDA's devices center, said in a statement.

The FDA also said Stryker must improve its program to train doctors to use the stent, and must also do a surveillance study of how well the device works for patients who have already gotten it.

The company was not immediately available to comment.

The FDA originally approved the Wingspan stent under a Humanitarian Device Exemption, when the agency allows up to 4,000 medical devices to be sold each year without requiring stringent evidence of effectiveness. To qualify, the device must address a rare disease or condition, and show "probable" benefit.

The trial supporting approval of Wingspan enrolled 45 patients who had a stroke caused by a blocked blood vessel in the brain and whose medical treatment failed to prevent another stroke.

(Reporting by Anna Yukhananov; Editing by Gerald E. McCormick and Sofina Mirza-Reid and Carol Bishopric)

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