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New Technique for Diagnosing Alzheimer’s Disease
MRI measurement of brain blood flow identifies functional decline (Feb. 11)
Researchers at the University of Wisconsin–Madison School of Medicine and Public Health may be moving closer to identifying the first signs of decline in the brain in patients with Alzheimer’s disease (AD).
After years of frustrating failure to stop late-stage AD, it's essential to find and treat the milder stages, according to neuropsychologist Professor Sterling Johnson. “We need to identify Alzheimer's as early as possible, before the really destructive changes take place,” he said. “Typically, by the time we diagnose Alzheimer's disease, patients have already lost much of their brain capacity, and it's difficult or impossible for them to recover.”
The earlier phases of AD — before large numbers of brain cells have been killed — should be more amenable to treatment, Johnson said. AD is the largest single cause of dementia. Early symptoms include memory decline, which eventually progresses to widespread cognitive and behavioral changes.
In a new study published in Cerebral Cortex, Johnson and his colleagues reported on measurements of brain blood flow in 327 adults. The researchers used an advanced form of magnetic resonance imaging (MRI) to compare blood flow in people with mild cognitive impairment and in those without early symptoms of AD but with a family history of the disease.
Reduced blood flow signifies reduced activity in particular parts of the brain, often due to the atrophy of nerve cells. One affected structure — the hippocampus — is necessary for making new memories. In cases of mild-to-moderate AD, 40% or more of the hippocampus has disappeared.
As expected, the AD patients had reduced blood flow in several brain regions linked to memory. People with mild cognitive impairment had a milder version of the same deficits. Moreover, people whose mothers (but not fathers) had AD had clear signs of reduced blood flow, even though they lacked symptoms of the disorder.
According to Johnson, other techniques that can measure blood flow are more costly and require the use of radiation and the injection of a drug tracer during the scan. If the advanced, noninvasive MRI technique continues to prove itself, it could be a key to detecting AD in its early — and hopefully more treatable — phases, he said.
Source: University of Wisconsin–Madison; February 11, 2013.