A study has found a type of scan could definitively diagnose dementia, and even pick it up in its earliest stages

Although around 225,000 people are diagnosed with dementia each year, the only way to categorically confirm that someone has the condition is to look at the brain in a post-mortem. Diagnostic tests can pick up the condition, but until now, there was no way to say they definitely had it.

However, now a new type of scan developed by researchers at the University of California has proven that it’s possible to detect the tau tangles and amyloid plaques that can cause dementia and pinpoint the moment that they trigger the disease, even in adults that have no symptoms.

This could mean that people at risk of the condition (such as those that carry the APOE gene) could be regularly screened, and anyone who was concerned about memory problems could be checked to alleviate their fears.

The new brain imaging is carried out using positron emission tomography scanners (PET scans) which look at cellular-level changes in organs and tissue.

Current scans only look for a decrease in brain cells or check that symptoms are not caused by another condition, such as a brain tumour.

These new scans were also useful for checking how tau tangles and amyloid plaques build up in the brain – the scientists believe that both tau and amyloid work together to cause the disease.

The researchers were able to confirm that with advancing age, tau protein accumulates in the medial temporal lobe – home to the hippocampus and the memory centre of the brain. However when the tau went beyond that area Alzheimer’s begins.

‘Amyloid may somehow facilitate the spread of tau, or tau may initiate the deposition of amyloid. We don't know. We can't answer that at this point,’ said Dr William Jagust, a professor at UC Berkeley's School of Public Health.

‘All I can say is that when amyloid starts to show up, we start to see tau in other parts of the brain, and that is when real problems begin. We think that may be the beginning of symptomatic Alzheimer's disease.’

Dr James Pickett, Head of Research at Alzheimer's Society said:

‘We know it can take months, and sometimes years, for some people to get diagnosed with Alzheimer’s and so a definitive way to diagnose the disease would be a big leap forward. Currently, the only way to know for sure whether someone’s memory impairment is due to Alzheimer’s disease is to examine their brain tissue after death and look for damaged proteins.

‘This new scan allows us to see tangles of a protein called tau – one of the hallmarks of Alzheimer’s disease – inside the brain, but so far it has only been tested in a small number of people. Only 15 people with Alzheimer’s disease were included in this study, some of whom were not typical of the majority of cases. This makes it difficult to determine how useful the scan could be to support diagnosis.

‘This technology is in the early stages of development and while it is beginning to provide researchers with important data about how Alzheimer’s disease develops, it is still many years before we could expect to see the scan being used in the clinic.’

For more information on the types of brain scans used to diagnose dementia, click here.