IMAGES OF BRAIN CAPTURE EARLY SIGNS OF ALZHEIMER'S

For the first time, brain images have captured the insidious destruction of approaching Alzheimer's disease in people whose thinking and memory are still rich and vigorous.

Combining brain scans with careful genetic screening, doctors can actually see bad spots inside the brain that are the all-but-certain early stages of the devastating illness.This latest innovation means doctors may be able to diagnose Alzheimer's more than a decade before it actually starts to steal its victims' mental powers.

"Accurate and early detection of Alzheimer's disease has been a goal for many years. This study shows it is possible to do that," said Zaven Khachaturian, director of the Alzheimer's Association's Ronald and Nancy Reagan Research Institute, named for the disease's most famous recent victim.

Many experts, however, caution against screening for impending Alzheimer's disease in completely healthy people because no one can predict precisely when the disease will start - or do anything to stop it.

The new technique is part of a whirlwind of research that over the past three years has brought doctors much closer to understanding and perhaps even treating Alzheimer's disease. All of it stems from the surprise discovery that a gene implicated in heart disease also appears to be involved in most Alzheimer's cases.

Dr. Eric M. Reiman and colleagues from Good Samaritan Regional Medical Center in Phoenix began with a blood test for the suspect gene and coupled its results with a form of brain imaging called positron-emission tomography - PET for short. They published their results in Wednesday's issue of the New England Journal of Medicine.

The gene is known as apolipo-pro-tein E, or apo E. It comes in three varieties - apo E-2, E-3 and E-4. It turns out that the E-2 version of the gene protects people from getting Alzheimer's, while E-4 makes it start at a younger age. The risk from E-3, the most common apo E gene, falls in between.

Since each person inherits two copies of every gene, one from each parent, everybody has one of six possible combinations of apo E, and each confers a different risk of Alzheimer's. However, no combination guarantees development of the disease.

Scientists have determined, however, that people born with two E-3 genes develop Alzheimer's 15 years later, on average, than people with two E-4s. With a combination of one E-3 and one E-2, the typical onset is later still.

About one-third of Americans carry one E-4 gene, but the worst genetic luck is to inherit two E-4s. These people, who make up 2 percent to 3 percent of the U.S. population, get Alzheimer's at an average age of 70.

An estimated 4 million Americans have Alzheimer's, and 100,000 die of its effects every year.