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Alzheimer's disease "jumps" across brain cells to spread

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(CBS) Alzheimer's disease spreads through the brain by jumping from one cell to another, according to a new study.

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The study found that tau protein, which indicates the fibrous tangles found in the brains of Alzheimer's patients, spreads along the brain's neurons from one region to the other - resulting in severe dementia. The new clues to the neurodegenerative brain disorder might help scientists find a way to stop the disease from getting worse.

For the study - published in the Feb. 1 issue of PLoS One - researchers genetically modified mice to have a human gene for the abnormal tau protein in an area of the brain's temporal lobe where tau is thought to begin to accumulate. The researchers analyzed the mice brains over a 22-month period to map the protein's spread and found that as mice aged, the tau spread to different regions of their brains across synapses - the junctions neurons use to communicate with each other.

"This pattern very much follows the staging that we see at the earliest stages of human Alzheimer's disease," senior study author Dr. Karen E. Duff, professor of pathology at the Columbia University Medical Center in New York City, said in a written statement.

Duff told the New York Times that the mouse study answers many questions, since scientists had long thought the disease spread through some mechanism from one brain region to the other, but human autopsies and brain scan studies have been inconclusive. Duff told the paper that's because looking at brains of people who died with Alzheimer's is like "looking at a wrecked car and trying to find out the accident's cause."

The study authors now hope their new findings can be used to improve treatments.

"If, as our data suggest, tau pathology starts in the entorhinal cortex and emanates from there, the most effective approach may be to treat Alzheimer's the way we treat cancer - through early detection and treatment, before it has a chance to spread," study co-author Dr. Scott A. Small, professor of neurology at the Columbia University Medical Center, said in the statement. "It is during this early stage that the disease will be most amenable to treatment. That is the exciting clinical promise down the road."

The findings may also provide new clues on how other neurodegenerative disorders, like Parkinson's spread, the New York Times reported.

Dr. William Thies, chief medical & science officer at the Alzheimer's Association told CBS News that the findings are still early science, and it could take up to five years to really learn what the study's implications are.

"If the speculation of these investigators is correct and you can find a way to interrupt the movement of tau from one neuron to another, that might be a useful therapeutic pathway," Thies told CBS News. "But there are many steps that have to come before you're actually going to get to a useful product that could be used to treat human disease."

An estimated 5.4 million Americans live with Alzheimer's disease. Alzheimer's disease is the sixth leading cause of death in the U.S., according to the CDC's latest report, taking more than 83,000 lives this past year.

WebMD has more on Alzheimer's disease.

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