People who suffer slight memory loss or a decline in cognitive abilities typically don't go to the doctor until symptoms are significantly obvious. But a new study has revealed that early MRI scans can detect shrinkage in certain regions of the brain to accurately diagnose Alzheimer's disease (AD) at a much earlier stage, when currently available drugs could be used to forestall the onset of full–blown dementia.

"We were aware that there's a change in the brain that takes place with Alzheimer's disease. In particular, one could see those structural changes in the medial temporal lobe, an area where the disease is first noted on pathology on autopsy studies," Ranjan Duara, MD, the study's lead author, told Diagnostics & Imaging Week.

"As a result of the disease process, there is a loss of brain cells in those regions. The brain shrinks and you can see it on high resolution MRI scans with very thin slices.

"We wanted to know if using the MRI in this way would help us detect not only the people who have Alzheimer's disease, but those who are destined to develop it even if they don't have symptoms," said Duara, who is medical director of the Wien Center for Alzheimer's Disease and Memory Disorders at Mount Sinai Medical Center (Miami Beach, Florida).

The study, conducted by the Florida Alzheimer's Disease Research Center (Miami), adds to a growing body of evidence that MRI brain scans provide diagnostic information about AD.

Researchers already have begun been using MRI as part of a multi–part diagnosis. But Duara's approach was different.

"We refined the methods to a great degree by using much thinner slices of the brain and we divided the temporal lobe into discreet structures and rated the amount of atrophy," he said. "We also provide reference images to guide the individual who is reading the scans about various degrees of abnormalities. We find we are much more accurate in the diagnostic process."

Duara and his team used a new visual rating system to evaluate the severity of atrophy in the brain's medial temporal lobe, specifically in three structures essential for the conscious memory of facts and events. They compared the MRI brain scans of 260 people: a group with probable Alzheimer's disease; two groups with varying degrees of mild cognitive impairment; and a control group of normal elderly with no discernible memory loss.

They discovered that the scores generated by the MRI–facilitated test accurately distinguished each group from the other and were in line with the types of memory problems most frequently caused by Alzheimer's disease.

The more extensive the brain atrophy, the more advanced the clinical stage of AD.

"We found that with 80% to 85% accuracy we could diagnose Alzheimer's as well in people who had some symptoms and in those who would develop full–blown disease," Duara said. "We think that we can diagnose disease in patient with no symptoms at all."

Current criteria used to diagnose Alzheimer's disease were developed two decades ago and do not include MRI as a standard tool. Duara said he thinks those criteria should be changed.

"If one were to do that, from a research standpoint, it would have a tremendous benefit for drug discovery trials alone," he said. "There are many trials going on with experimental medications and billions of dollars are spent each year just for these trials.

"A certain proportion of patients in those trials don't have Alzheimer's disease but dementia from some other cause," Duara said. "I think if they included MRI, we would get much cleaner results and we could see if these drugs actually work with much greater accuracy. The same is true for genetics studies. In all these studies we're trying to compare people who have the disease with those who don't."

The National Institute on Aging reports that early, accurate diagnosis of Alzheimer's can help people to plan for the future and allow them to begin early treatment of disease symptoms.