Can the motion of water inside the brain signal the early signs of Alzheimer’s disease?

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Doctors would love to find a way to look inside people’s brains and spot the initial changes that lead to Alzheimer’s disease, the mysterious and devastating disorder that robs patients of their memories and intellect. There is no cure, but treatments to preserve cognitive function are considered most effective when begun early.

A team of Italian researchers reported today that a cutting-edge brain-imaging test can recognize memory decline in older adults who may be in the initial stages of Alzheimer’s.

The brain scan measures the random motion of water inside the hippocampus, which plays a key role in forming new memories. It turns out that in people age 50 and older, those with a higher measure of this motion did worse on simple tests that measure verbal and visual-spatial memory.

The study included 76 healthy people who ranged in age from 20 to 80. All of them took a battery of tests. In one, they were asked to remember a list of 15 words after a 15-minute delay. In another, they were asked to reproduce a complex line drawing from memory after a 20-minute delay.

Then the subjects got MRIs, which measured the total size of the hippocampus. As in some prior studies, the total volume of the hippocampus was not linked to memory performance. But using a type of analysis called diffusion tensor imaging, the researchers did find that subjects with a high level of “mean diffusivity” in the hippocampus had lower scores on the memory tests. The results were published in the journal Neurology.

The researchers said they weren’t sure why increased water diffusivity would affect memory, but they suspect it is a sign of “enlarged extracellular spaces.” That could be a sign of pathologic changes in the brain that lead to Alzheimer’s, they said.

In a related editorial, radiology researcher Norbert Schuff of the Center for Imaging of Neurodegenerative Diseases at the Veterans Affairs Medical Center in San Francisco called the study “eloquent” and said the test could become a valuable tool for detecting early cases of Alzheimer’s disease. (Of course, more studies are needed to confirm these results.)

“As better medications for [Alzheimer’s] become available, it will be essential to identify individuals at high risk for the disease not only early but also as accurately as possible so that treatment interventions can be most effective,” he wrote.

-- Karen Kaplan