Brain imaging gives further insight on Alzheimer's decline

Researchers at Washington University School of Medicine have identified a protein that could help trigger the decline caused by Alzheimer's disease.

It's well established that an excessive buildup of plaque and dysfunctional proteins contributes to the development of Alzheimer's disease. Many studies have focused on the protein amyloid beta, but the new research took a closer look at another protein - tau.

Although it has been linked to the neurological condition, it hasn't been the subject of much investigation as, until recently, it was difficult to find imaging techniques that were able to show the impact of tau.

The team at Washington University School of Medicine used an innovative imaging agent that attaches to tau, making it visible with positron emission tomography (PET) scans.

Published in the journal Science Translational Medicine, the research found that measuring this protein was far more accurate at measuring cognitive decline in Alzheimer's disease than amyloid beta in PET scans.

Brain images from 36 people with no cognitive problems were compared to those of ten patients with early-stage Alzheimer's disease. By doing this, the team determined that measuring tau can better predict symptoms of dementia than amyloid beta.

To help them arrive at this conclusion, participants who underwent brain imaging were also assessed with several other methods of diagnosis for Alzheimer's, including the clinical dementia rating (CDR) scale, cerebrospinal fluid measures, and widely used pen and paper tests of memory and other brain functions.

Dr Beau M. Ances, senior author of the study and an associate professor of neurology, said the findings support previous conclusions that early-stage dementia can be detected by looking at levels of the amyloid beta protein. However, he noted that for a long period of time, people with Alzheimer's disease can experience no problems with cognitive functions, meaning that their  memory and thought processes are still intact even with increased amyloid beta levels.

"What we suspect is that amyloid changes first and then tau, and it's the combination of both that tips the patient from being asymptomatic to showing mild cognitive impairment," Dr Ances explained.

Dr Ances said the findings would be important to better understanding the timeline of Alzheimer's progression and for defining which regions of the brain are involved.

"Usually we can only diagnose patients later in the disease process, when brain function already is diminished," he said.

"While we currently cannot prevent or cure Alzheimer's disease, delaying the onset of symptoms by ten to 15 years would make a huge difference to our patients, to their families and caregivers, and to the global economy," Dr Ances explained.

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