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Deadly glow. A new marker reveals brain plaques in patients with Alzheimer’s disease (right).

Scan Reveals Alzheimer’s Toxin

STOCKHOLM--Researchers suspect that future drugs for Alzheimer's disease will work best if given early, raising the need for an accurate test that spots the earliest signs. Today at the International Conference of Alzheimer's Disease and Related Disorders, a team unveiled the first images from a brain scan technique that picks up one of the defining--and first--features of the disease.

Alzheimer's is notoriously difficult to diagnose. With high-resolution brain scans, tests of memory and problem solving, and by excluding other diagnoses, clinicians can be fairly sure a patient has Alzheimer's--at least once the disease has done massive damage to the brain. But they only know for sure when an autopsy reveals plaques and tangles in the brain. The main ingredient of plaques is a protein called B-amyloid, and it congregates in the brain well before the onset of dementia.

To see if they could visualize b-amyloid in the brain, a team led by William Klunk at the University of Pittsburgh developed a molecule that sticks to b-amyloid. Animal studies showed that it crosses the blood-brain barrier, is nontoxic, and can be clipped to a radioactive tag. Then a group led by neurologist Henry Engler of Uppsala University in Sweden injected the molecule, dubbed PIB, into nine people with "mild" Alzheimer's and five healthy people. A positron emission tomography scan tracked where it went. Their results audibly took the breath away from Alzheimer's researchers at the conference: The marker sailed right through the healthy brains, but in people with early Alzheimer's, the marker stuck in the frontal lobes and temporal-parietal areas, two of the brain regions most damaged by plaques.

"This is something we've all been waiting for," says Michael Pontecorvo of Mitsubishi Pharma America in Warren, New Jersey. Adds Randy Buckner of Washington University in St. Louis, "we've been looking for early diagnostics, and this opens a new window on what we think to be the primary marker associated with disease."

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Imaging b-amyloid in the brain of people with mild Alzheimer's disease