Alzheimer’s disease could be definitively diagnosed for the first time after scientists proved brain scans can pick up the condition in its earliest stages.

Currently the only way to determine whether Alzheimer’s is present is to look at the brain of a patient after death.

For patients who are still alive, doctors usually use special cognitive tests which monitor memory and everyday skills such as washing and dressing.

"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." Dr James Pickett, Head of Research at Alzheimer's Society

But now researchers at theUniversity of California have proven that it is possible to spot the sticky amyloid plaques and tau protein tangles which cause the disease and pinpoint the moment that they trigger Alzheimer’s disease.

The US scientists were able to track the progressive stages of Alzheimer’s disease, even in adults who showed no symptoms. It means that people at risk from the condition – such as one in five of the population who carry the APOE gene variant – could be regularly screened.

And it could reassure people who are suffering mild memory problems that they do not have the disease.