Imaging techniques can detect Alzheimer's in the brain
The work has revealed that the brain starts to lose tissue at an accelerated rate up to five years before the disease becomes apparent.
The technique could enable doctors to monitor the progression of the disease from its earliest stages.
Early onset
The earliest possible detection is important because the quicker patients can be given drugs to slow its progression, the more impact they are likely to have.
A team from the National Hospital in London, UK, made the breakthrough using an imaging technique called voxel-compression mapping.
They were able to detect progressive brain cell degeneration in specific parts of the brains of patients in the very earliest stages of Alzheimer's.
The work was carried out on four patients who had a strong family history of the early onset form of Alzheimer's.
Each underwent a series of magnetic resonance imaging (MRI) scans, which produce detailed three-dimensional images over a period of up to eight years.
Cell degeneration
During the scanning period, none of the patients showed any signs of Alzheimer's, but all four later went on to develop symptoms.
Researcher Dr Nick Fox said: "The ability to track physical disease progression in an individual patient from the earliest symptomatic stages has implications for the assessment of new treatments.
"It raises the hope that we might one day be able to intervene with therapy at a very early stage, before the devastating cognitive decline of the disease has already become established."
Susceptible individuals
The director of research at the Alzheimer's Society, Dr Richard Harvey, said: "This is an exciting new technique for monitoring the progression of Alzheimer's disease.
"In the next few years, we are going to see a number of new drugs and vaccines aimed at slowing down the progression of Alzheimer's disease.
"Techniques such as this, using MRI, will enable us to prove whether or not these drugs work more quickly and with smaller numbers of patients."
Dr Kevin Morgan, of the Alzheimer's Research Trust, agreed that the technique was of "potentially great interest".
He said the major goal of all researchers in this field was to be able to identify individuals who are susceptible before they develop symptoms.
He said: "These patients are the ones that would benefit most from early implementation of therapeutic procedures which hopefully will be possible at some future point in time - there are a number of approaches currently under assessment."
The research was published in the Lancet medical journal.