brain scans
Image: COURTESY OF THE PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES

First there is absent-mindedness, then deficits in speech and perception, and eventually an inability to perform even the most basic daily tasks without assistance. Indeed, the cruel symptoms of Alzheimer's disease (AD)--the most common cause of dementia--are well known. Exactly how the pathology progresses in the brain, however, is less obvious. To that end, a new study using 3-D magnetic resonance imaging has proved illuminating. According to a report published today in the early online edition of the Proceedings of the National Academy of Sciences, research conducted using that technique revealed changes in the brain structure of AD patients over time.

The investigators, led by Nick Fox of University College London, compared presymptomatic, mildly affected and moderately affected patients, each of whom underwent two separate brain scans. Whole-brain atrophy, or tissue loss, occurred in all subjects as the disease progressed, the team found. But the rate of atrophy in different brain regions varied among the groups. Perhaps not surprisingly, the researchers observed that atrophy starts--and proceeds most rapidly--in the areas of the brain involved in memory. As the disease progresses, however, it spreads to the neocortical areas, which figure importantly in speech and perception. "Our results suggest that the sites showing the most significant rates of atrophy alter as the disease advances," the team writes. The scans also revealed regional atrophy in patients before the onset of symptoms.

The good news is that researchers may one day be able to use such neuroimaging techniques to detect changes brought about by AD early enough to thwart it. "There is every expectation that modifiable risk factors for the initiation and spread of AD pathology will be discovered," A. David Smith of the University of Oxford writes in a commentary accompanying the report, "and therefore we can trust that it will be possible before too long to prevent or delay the development [of] this terrible disease."