Looking for trouble
Ever since Alois Alzheimer described the disease in 1907, a specter has haunted medicine -- who has Alzheimer's disease? Who's getting it?

Alzheimer's remains an autopsy diagnosis -- the only way to confirm a diagnosis is to view brain slices under a microscope. When Alzheimer's was untreatable, diagnosis was not all that important for the average patient. But with some treatments now available, diagnosis is a critical issue.

Diagnosis has improved over time. Even without digging into the brain, a competent diagnostician can be accurate 90 percent of the time. Still, a foolproof diagnosis would be useful for finding patients who could benefit from existing drugs, for testing new drugs, and for backstopping incompetent diagnoses.

Enter the magnetic resonance (MRI) machine, a mainstay of modern medicine. The machine uses a strong magnet and radio-frequency waves to evoke signals for computer processing into images of the body (more on MRI technology). As MRI machines became common, scientists have put them to new use. For example, Norbert Schuff of the San Francisco Veteran's Affairs Medical Center is using magnetic resonance to measure a chemical found in living neurons but not dead ones.

Alzheimer's, you'll recall, savages neurons in brain regions that govern memory and thought.

Absence makes the brain grow weaker
Schuff is focusing on N-acetyl-aspartate -- NAA to its friends -- in the hopes that low concentrations may identify Alzheimer's-caused cell death. He and his colleagues have combined a standard MRI with a newer technique called MR spectroscopic imaging, which measures the spectrum emitted by brain chemicals stimulated by an MR machine.

By itself, the structural information of a standard MRI can be difficult to interpret, Schuff says. "MRI measures basically the distribution of water in the brain." Therefore, an MRI may not specifically reflect the death of neurons in Alzheimer's. Adding MR spectroscopic imaging, however, allows measurements of brain chemicals such as NAA, which occurs only in living neurons.

Spectroscopic images from a magnetic resonance machine show levels of NAA, found in healthy neurons. Left: NAA is lower in the Alzheimer's brain, especially in the region that includes the hippocampus, a center of memory and a focus of Alzheimer's problems. Right: a spectrum from the left hippocampus also shows a scarcity of NAA.
Courtesy Norbert Schuff.

Unfortunately, because NAA is scarce in the brain, the images don't carry the detail of a standard MRI. Still, the results are revealing. "The changes we observed are consistent with the regional patterns of damage seen in Alzheimer's disease," says Schuff.

Although the combined image is not conclusive, he says, "it has the potential to improve our ability to diagnose Alzheimer's and to follow its progression."

Are there any real cures on the horizon?