blood clots

MRI tool cuts risk of making strokes worse

JOHNS HOPKINS (US) — A new way of reading MRI brain scans measures blood-brain barrier damage more accurately, an advance doctors hope will lead to safer, more individualized treatment immediately after a stroke.

The tool may help doctors sidestep using clot-busting drugs in the minority of ischemic stroke patients who could be harmed. It may also enable them to use such treatment in situations they now consider too risky.


The traditional MRI scan on the left locates a stroke in the bright area to the bottom left of the image. The image on the right, produced with the new software tool, identifies blood-brain barrier damage. (Credit: Richard Leigh/Johns Hopkins)

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“A better characterization of blood-brain barrier damage opens the door to new approaches to treating stroke patients,” says study leader Richard Leigh. “We want to help patients, but we need to make sure our treatments don’t make things worse.”

The blood-brain barrier is a unique shielding of blood vessels that limits the passage of molecules from the blood stream into the brain. Without it, the brain is open to infection, inflammation and hemorrhage.

Leigh’s team, in a report published in the journal PLOS ONE, says it hopes to use its new software tool to identify barrier damage in victims of ischemic stroke, caused when a blood clot cuts off blood flow to a part of the brain. The affected area can begin to die if the blockage continues.

When patients come to the hospital within three to four hours after an ischemic stroke, doctors quickly move to give them the intravenous drug tPA. They hope it will dissolve the clot without causing additional damage, says Leigh, assistant professor of neurology and radiology at the Johns Hopkins University School of Medicine.

But in some people—roughly 6 percent of stroke patients treated in this manner—there already is too much damage to the blood-brain barrier; instead of helping, the drug causes bleeding in the brain, severe injury, and sometimes death. Doctors can’t currently predict which patients will have this bad outcome. If physicians knew the extent of damage to the blood-brain barrier, however, they would be able to choose the safer treatment option, Leigh says.

Most stroke patients, Leigh notes, don’t get to a hospital within the currently accepted window for optimal tPA use, so physicians don’t give them intravenous tPA for fear of hemorrhage. Sometimes more aggressive treatment is needed, such as pulling the clot out mechanically via a catheter threaded from the groin area or by directly injecting tPA into the brain.

Before any procedure, these patients traditionally receive an MRI to estimate the risks and benefits of such an aggressive approach. But there has been no reliable way to detect the subtle amount of blood-brain barrier damage that would offer clues about how well the patient would fare under various treatments.

That led Leigh to develop new software, which uses MRI images already being taken and overlays them with calculations that more precisely measure blood-brain barrier damage. Using the new MRI software could mean that for some patients, tPA could be safely used even if they arrive at the hospital later than safe-use time guidelines now indicate.

“It’s a personalization of medicine,” Leigh says of the new MRI technique. “Rather than lumping everyone together, we can figure out—on a case-by-case basis—who should and who shouldn’t get which treatment. In the long run, we can increase the number of patients we can help and decrease the number who have complications.”

Leigh and his colleagues say more research is needed before his software enhancement can be widely used, but “proof of concept” has been established in a review of MRI scans from nine stroke patients with known blood-brain barrier damage.

Each patient was found to have a different amount of damage. Leigh and his team are now looking at a larger group to better define the meaning of these variations and how physicians can use this information to choose the best treatment.

Source: Johns Hopkins University

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