Scans of Alzhemier's Patients Could Show How Disease Will Shrink the Brain

Scientists who scanned the brains of people with Alzheimer's disease say the build-up of protein tangles could predict how the brain will shrink.

The authors of the paper published in the journal Science Translational Medicine studied 32 patients in the early clinical stages of Alzheimer's Disease, the most common form of dementia which 5.8 million people in the U.S. are thought to be living with.

Lead author Renaud La Joie, a postdoctoral researcher at the University of California, San Francisco, In Vivo Molecular Neuroimaging Lab, told Newsweek the work is part of a larger, ongoing study involving patients with the condition.

At the institution's Memory and Aging Center, the participants had their cognitive skills tested and underwent MRI scans to measure brain volume and structure. The patients also had PET scans which detect the hallmarks of Alzheimer's disease in the brain, called amyloid plaques and tau protein tangles.

Researchers hope this will enable them to chart changes in patients, such as which of their cognitive skills have declined the most, and which brain regions are shrinking, La Joie explained. As Alzheimer's disease progresses, neurons die off, and regions start to shrink, leading to a loss of volume.

For this project, the participants were recruited between 2014 and 2017, and were followed up after 15 months on average. La Joie and colleagues found collections of tau protein tangles which showed up in PET scans were an indicator of how the brains of individual patients would get smaller in the future. They also found the link between the amount of tau detected in the first scan and later atrophy was particularly strong in younger patients.

However, the researchers were surprised that they didn't make similar findings with amyloid. This plaque collects early on in the disease while tau comes later, nearer the time a person starts to develop symptoms. For decades, scientists working on drugs to treat the condition have focused on amyloid.

The team believes tau PET scans could be useful for predicting the progression of the disease, and help to develop new treatments.

La Joie said: "Though we had strong hypothesis that brain atrophy/damage would be better related to tau than amyloid, we were amazed by the very strong relationship between tau and brain shrinkage.

"If you're looking at individual patient maps showing where the brain is shrinking, it really resembles the map showing where tau tangles were at the beginning of the study."

However, he acknowledged the study is limited because it involved only 32 patients, and the team looked at short-term brain changes. They hope to replicate their findings in larger samples and examine how tau PET scans could help predict decline in cognition and functions, not just brain shrinkage.

La Joie highlighted patients with the condition can be very different, which is a problem when trying to predict how the disease will develop.

"For instance, a given patient might have a pretty stable memory function, but it doesn't mean they don't progress: maybe they declined a lot in their language or visuo spatial abilities, but you missed it because you were focusing on memory," he explained.

Such scans could be useful as a precision medicine tool, to determine which brain region, and therefore which cognitive function, is expected to decline for a given patient, he said.

Experts not involved in the study welcomed the work. James Pickett, head of research at the U.K.-based charity Alzheimer's Society, told Newsweek: "Studies like this continue to remind us that, while amyloid has often taken much of the limelight in recent years, it is also vital we fully understand the role of tau as a driver in the progression of Alzheimer's disease."

"The scanning technique that is used here takes tentative steps to giving us a window into the brain to accurately assess the impact of future tau-targeting treatments," he said.

Laura Phipps of the charity Alzheimer's Research UK told Newsweek: "This relatively small study adds to evidence that tau may drive the death of brain cells, and could explain why symptoms get worse as tau spreads through the brain. While the majority of volunteers in the study were under the age of 65, making it harder to generalize the findings to everyone with the disease, the study highlights the importance of focusing future research efforts on the tau protein."

She added: "A number of potential Alzheimer's drugs have been developed to target the amyloid protein and we hope that by intervening early, these drugs could be effective at slowing or stopping the disease.

"But for the best chance of success, it's crucial to explore as many avenues for treatment as possible. Tau offers a promising alternative for future Alzheimer's medicines, and we're already seeing drugs against the protein starting to be developed. The ability to track tau in the brain will be critical for testing treatments designed to stop the protein causing damage, and the scans used in this study could be an important tool for future clinical trials."

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A stock image shows MRI brain scans. Getty