St. Jude Medical Inc. said Tuesday it got European regulatory approval to market the world's first implanted neurostimulation device to relieve chronic migraines that don't respond to drugs. However, it remains to be seen whether the the device will get past U.S. regulators.

The Genesis peripheral nerve stimulation device is a pacemaker-like product implanted in the chest; lead wires run up to occipital nerves in the back of the head. The wires deliver small electrical pulses to the nerves, believed to play some role in the often disabling headaches.

In Europe, the device got the CE mark -- regulatory approval -- for patients who have headaches lasting more than four hours a day, 15 days a month, and who aren't helped by at least three drugs.

The World Health Organization estimates about 10 percent of adults have migraines, and about 2 to 4 percent have about 15 attacks a month. The market for the device is estimated at around $1 billion, as few effective treatments exist to bring relief to patients.

The approval was supported partly by a randomized, controlled, blinded study of 157 patients conducted by the St. Paul, Minn.-based company.

The study found that patients who used the device for about three months had seven fewer headaches a month. Patients with an implanted, but initially non-stimulating, device only had one fewer headache a month. (All these patients enrolled in the trial had, on average, a mind-boggling 26 headaches per month.)

Overall, 41 percent of the "active" group reported pain reduction, compared with 13 percent for the control group after the first 12 weeks.

The results, initially presented at the International Headache Congress in Berlin in June, helped the company get the CE mark, but might not be enough for the Food and Drug Administration.

According to reports in June, when the data were first shared, the trial didn't meet the FDA's trial goals; the agency wanted to see a slightly greater reduction in pain in the "active" group.

At the time, the company said it was meeting with the FDA this year, and hopes to convince them that the product is safe and effective.

Boston Scientific is testing a rival device, named PRISM (PRecision Implantable Stimulator for Migraine). The trial for the device began in the U.S. in 2005.

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