People in the early stages of Alzheimer’s disease may have more “leaks” in the barrier that separates the brain from the bloodstream, a small study suggests.

Known as the blood-brain barrier, it’s made up of tightly joined cells that line blood vessels in the brain. They form a filtration system that allows certain essential substances — such as water and sugar — into the brain, while keeping potentially damaging substances out.

The new study adds to evidence that leaks in the blood-brain barrier are detectable in Alzheimer’s patients.

But it’s not clear what it all means.

“They don’t know whether this leakage is a result of the disease, or a cause of it,” said Dr. Ezriel Kornel, an assistant clinical professor of neurological surgery at Weill Cornell Medical College, in New York City.

It’s also unclear exactly what is happening in the leaky areas spotted on patients’ brain scans, according to Kornel, who wasn’t involved in the study.

In theory, he said, the leaks could be opening the door for toxic substances to enter the brain — but the study doesn’t prove that.

“It’s an interesting issue,” said David Morgan, director of the Byrd Alzheimer’s Institute at the University of South Florida, in Tampa. Morgan also wasn’t involved with the current study, but reviewed its findings.

Researchers know that the pathological brain changes associated with Alzheimer’s begin at least 15 years before symptoms appear, Morgan explained.

First, there is an abnormal buildup of proteins called amyloid. There are no immediate symptoms because the brain is able to compensate for those protein deposits, Morgan said.

Eventually, though, another type of abnormality appears — twisted fibers of a protein called tau. Symptoms typically arise not long afterward, according to Morgan.

So, the question — according to Morgan — is where in that sequence of events does brain leakage occur?

The findings are based on 16 patients who’d been diagnosed with early Alzheimer’s disease, and 17 healthy adults the same age. Walter Backes and colleagues at Maastricht University, in the Netherlands, used a special MRI technique to detect areas of brain leakage in each study participant.


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