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New Alzheimer's guidelines redefine disease

April 19, 2011|By Marissa Cevallos, HealthKey

Guidelines for diagnosing Alzheimer’s — the memory-stealing disease — have been updated for the first time in 27 years.

The new guidelines recognize the disease as a continuum, not a single stage, according to a release Tuesday by the National Institutes of Health's National Institute on Aging and the Alzheimer’s Assn.

In 1984, Alzheimer’s was defined as having a single symptom — dementia — and the diagnosis was only confirmed at autopsy by the abnormal amounts of proteins forming plaques and tangles in the brain.

The new guidelines reflect the more modern understanding of the disease: Alzheimer’s can start progressing up to 10 years before signs of dementia.

And autopsies can reveal a brain riddled with plaques in someone who showed no signs of dementia.

In clinical settings, the guidelines reflect what many doctors already use to diagnose the disease. For example, memory isn’t always the first thing to go; vision, literary skills and speech can deteriorate while memory remains intact. And while Alzheimer’s is rare in people younger than 40, the disease progresses the same way as in a 90-year-old. And testing for mutations in three genes can help determine whether a patient has early onset of Alzheimer’s (though 10 related genes are known).

Not all the major changes will be evident in the doctor’s office, however. Many of the new recommendations for diagnosing the disease are for researchers only, especially for diagnosing the earliest stages of brain changes. Guidelines that use biomarkers, or medical indicators of a disease, aren’t standardized yet for clinical use, such as using positron emission tomography (PET) scans or analyzing cerebrospinal fluid to find amyloid buildup.

But some cutting-edge research tools will now be standardized to diagnose the disease’s early stage: mild cognitive impairment, having memory problems others notice but that don’t interfere with daily life. Such impairment may or may not turn into Alzheimer’s dementia. But in some specialized clinical settings, the diagnosis can be made clearer by using biomarkers such as levels of protein in the cerebrospinal fluid or atrophy in the brain as revealed by magnetic resonance imaging.

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