Brain imaging may allow Alzheimer's diagnosis

By Will Dunham
12 aug 2008--An imaging method known as a PET scan may enable doctors to determine whether a person has "plaques" in the brain that are a hallmark of Alzheimer's disease, according to a Finnish study published on Monday.
The brain tissue of people with Alzheimer's disease contains abnormal clumps called amyloid plaques, but generally doctors cannot be sure if they are there until the brain is examined after death in an autopsy.
The findings of the small study led by Dr. Ville Leinonen of the University of Kuopio in Finland indicated that positron emission tomography, or PET, imaging can detect the plaques.
This shows PET scans may become a useful tool to diagnose Alzheimer's disease, a fatal and uncurable mind-robbing ailment that is the most common form of dementia in the elderly, Leinonen said.
"It's very promising," Leinonen, whose study was published in the American Medical Association's journal Archives of Neurology, said in a telephone interview.
Experts have been seeking ways to detect the plaques, short of obtaining a sample of brain tissue, in order to diagnose Alzheimer's in its early stages. These plaques and irregular knots of fibers in the brain called neurofibrillary tangles are hallmarks of the disease.
Early diagnosis can allow doctors to give people with Alzheimer's disease drugs aimed at slowing the cognitive decline associated with the condition.
The study involved 10 people, all of whom had undergone a brain biopsy because of a suspected abnormal increase of cerebrospinal fluid in the brain.
By examining this brain tissue, the researchers determined that six of the people had Alzheimer's disease-related plaques in their brain and four had no such brain changes.
The patients later underwent a 90-minute PET scan.
Following an injection of a chemical "marker" intended to help pinpoint the brain plaques, the PET scans accurately determined in nine of the 10 people who had the plaques and who did not, the researchers said.
"It's not 100 percent, but the correlation was very good," Leinonen said.
None of the 10 people in the study had yet developed severe dementia at the time of the study, the researchers said. They said larger studies are needed to verify that PET scans can become a common diagnostic tool.
The researchers said another potential use of PET scans would be to monitor plaque deposits in the brains of people taking part in research into potential new Alzheimer's drugs to see if the drugs are working.
PET scans currently are used by doctors to detect cancer, cardiac problems such as damage following a heart attack, brain abnormalities and other purposes.
Other studies have hinted at the promise of imaging methods in diagnosing Alzheimer's disease. Canadian researchers said last month they used magnetic resonance imaging, or MRI, scans to locate Alzheimer's-like plaques in rabbits.
An estimated 26 million people have Alzheimer's globally and experts predict this number will grow to 106 million by 2050.