The following report by medical editor Marilyn Brooks first aired Sept. 6, 2005, on Channel 4 Action News at 5 p.m. and re-aired on Dec. 28, 2005.

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Doctors at Allegheny General Hospital are now using a therapy that can remove blood clots from the brain when a stroke is in progress.

Of the 350,000 strokes that occur each year, 85 percent are caused by a blood clot that clogs a blood vessel in the brain.

For stroke victims, life is a race against time. While the best hope for a full recovery depends on clot-dissolving drugs, less than 5 percent of patients receive them.

Experts say clot-dissolving drugs are useful, but carry potential risks.

"If you have a lot of blood pressure going through those blood vessels going through a damaged areas, it can cause a hemorrhage," said Dr. Andrew Wu, a neuroradiologist at Allegheny General Hospital.

John Kelly, 56, recently woke up with a bad headache, numbness and tingling on one side of his body.

"I had no idea what a stroke was or what the symptoms were, which might have made a difference. But, I didn't, so I just went back to bed and went back to sleep," said Kelly.

He'd had an ischemic stroke caused by a clot in an artery supplying blood to his brain.

Doctors used the Merci Retriever to remove the clot. But, not all patients can benefit.

"If you have a narrowing of the carotid and the device can't get through, we obviously can't use it. If you have other blood vessel problems higher up, that also presents a problem," said Wu.

Merci is a catheter with a coil. It is threaded through the artery to the blood clot in the brain. Once deployed, the coil assumes a corkscrew shape and engages the clot. A balloon is inflated to control blood flow, while the clot and device are pulled into the catheter and out of the body.

But before patients undergo the procedure, they have an MRI. There's no sense in doing an invasive procedure if the patient can't benefit. The MRI shows whether the affected portion of the brain is already dead, or if it can be salvaged by restoring blood flow.

For John Kelly, the scan showed he was a candidate.

"Once they got the clot out, it was like someone through a switch it was almost magical. I couldn't move my left side, and then I could move my arm and I was able to get it up and scratch my nose. It just felt wonderful," said Kelly.

Allegheny General Hospital is exploring the Merci system, but also uses clot-busting drugs. Others use just the drugs, still others use both Merci and the drugs.

It will be at least three- to five years before doctors determine which system is best.