MONDAY, May 27, 2002 (HealthDayNews) -- Head scans that measure the size of a key memory center in the brain may help doctors predict Alzheimer's disease decades before a patient's mental ability falters, new research has found.
The findings involve an area deep in the brain called the hippocampus, one of the earliest sites to be affected by Alzheimer's. Using magnetic resonance imaging (MRI), the researchers showed that at death women with dementia linked to the degenerative disorder had markedly smaller hippocampus volume compared with women who died with normal brain function intact. More modest changes were also evident in women with the cellular scars of early Alzheimer's but no memory loss when they died.
"We wanted to see if we looked at people who were not demented and had no memory impairment, could we identify which had Alzheimer's by looking at the volume of the hippocampus," said James Mortimer, director of the Institute on Aging at the University of South Florida in Tampa and a co-author of the study. "We can do it with great accuracy."
"We're probably able to pick up Alzheimer's disease before clinical symptoms appear," added Karen Gosche, a brain imaging expert and lead author of the study, which appears in tomorrow's issue of Neurology. Gosche performed the work as a doctoral student at the University of South Florida.
Mortimer said MRI scans of the hippocampus, which helps encode and access memories, will become both a predictive and a diagnostic tool for Alzheimer's disease, though not a stand-alone technology.
Rather, he said, it will make a valuable addition to other tests, such as scans of additional brain areas, a family history of the disease and whether a person has APOe4, a gene linked to the condition.
Alzheimer's disease affects an estimated 4 million Americans, though as the population ages that number could surge to 15 million by the middle of the century. The condition, which is believed to be caused by the buildup of sticky protein plaques in the brain, typically occurs after age 65, but in some cases can strike as early as the 40s.
The latest work comes from the ongoing Nun Study, a long-term research project examining the effects of aging in hundreds of Catholic sisters. That effort began in 1992, with 678 nuns who at the time ranged in age from 75 to 102.
The researchers analyzed MRI scans taken from 56 of the nuns in autopsies. Two dozen of the sisters were demented at death, and 33 had signs of Alzheimer's disease in their brain tissue, including the buildup of sticky protein plaques and fibers.
That some women had brain changes associated with Alzheimer's but no dementia probably reflects their advanced age, which averaged around 90 at death. "There are a lot of people who have rather severe Alzheimer's disease in their brains yet never develop a dementia in their lifetime," Mortimer said.
While hippocampal volume varies from person to person and with age, Gosche's group found that after considering total brain size, MRIs could almost always pick out nuns with dementia based on shrinkage of the region.
The scans could identify not only which sisters had full-blown disease, but which had more subtle and early stage brain changes, like plaques and tangles, that occur decades before memory loss sets in. "We could find the people who had the disease even though they hadn't shown it yet," Mortimer said.
Gosche, who wrote the computer software that helped speed up the volume analysis from more than a half hour to just a few minutes, is now conducting a study to see if the results hold in men.
She has formed a company, NeuroImaging Sciences, out of her home in Gainesville, Fla., to help researchers conduct similar experiments. In the future, she said, she'd like to offer the program to radiologists to let them perform the volume analysis on their patients who undergo MRI.
Mony de Leon, a brain imaging expert at New York University and the scientist who first discovered the link between shrinking hippocampal volume and Alzheimer's, said the new research "locks in the argument even stronger" that the region indeed reflects the presence of the disease.
Why the hippocampus is among the brain's first victims of Alzheimer's isn't clear, de Leon added.
One reason for its dwindling volume may be that as neurons in the region die off, the entire area shrivels around the missing cells. Another possibility is that the afflicted neurons themselves are shrinking. A third (though least likely) prospect is that the site becomes dehydrated with the loss of brain and spinal fluid.
What To Do
To find out more about Alzheimer's disease, try the National Institute of Neurological Disorders and Stroke, or the Alzheimer's Association.
