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Wednesday, 14 February, 2001, 05:22 GMT
Stroke advance 'could save lives'
Brain image
Stroke damages the brain tissue
An imaging technique could give doctors more time to prevent death and brain damage in patients who have had a stroke.

The technique, magnetic resonance imaging, can measure oxygen use in the brain tissue injured after a type of stroke caused by blockage to the arteries.

This may help doctors determine whether the injured tissue could be saved by giving the patient a powerful clot-busting drug.

Previous studies have shown that the drug - tissue plasminogen activator (tPA) - is effective for up to three hours after a stroke.

However, imaging could help to identify patients who would still benefit from the drugs well after the three-hour deadline has passed.


Brain imaging might be useful for other time-sensitive clot busters

Stroke Association
The drug is not currently used in the UK - but the research could have similar implications for the use of other clot-busters which are.

The technique has been tested by a team from the University of North Carolina at Chapel Hill in the US.

Researcher Dr Weili Lin said: "If one of the blood vessels is blocked, brain tissue goes through a process before it's going to die. This process takes time.

"It depends on how much cerebral blood flow is being reduced, and on how long the tissue is under attack."

Therefore, depending on extent of injury, tissue that gets limited blood flow could survive for much more than three hours.

Brains

Dr Lin and his collaborators at UNC and Washington University in St. Louis used MR imaging to look at the brains of seven stroke victims at two time points:

  • three to six hours after the onset of symptoms
  • three to five days later
Because the brain is roughly symmetrical, the researchers could compare oxygen usage in tissue at the site affected by a blood clot to the equivalent site on the opposite side of the brain, called the contralateral region.

They found that if, at the first time point, the blocked tissue was using less than about 35% of the oxygen used by its counterpart on the other side of the brain, the tissue did not survive to the second time point.

However, if the damaged tissue was using more than 35% of the normal oxygen supply, it could survive for much longer.

Dr Lin said: "If we can extend beyond three hours, I think that would open up a lot of opportunities for patients to receive adequate treatments."

A spokeswoman for the UK's Stroke Association said: "Unfortunately tPA is not used in the UK but brain imaging might be useful for other time-sensitive clot busters.

"We need a wider use of MR imaging, not every hospital in the UK uses it because it is expensive.

"We also need more emphasis on treating stroke as an emergency so patients get to hospital quickly and increase their chances of recovery."

It is estimated that only about 10% of US stroke victims are admitted to hospital within three hours.

This is partly due to the fact that many patients do not immediately recognise that they are having a stroke.

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07 Feb 01 | Health
Stroke test 'could save lives'
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