There is as yet no test that can conclusively diagnose Alzheimer's in a living patient. Brain scans can detect atrophy, like enlarged ventricles and sulci, that often occurs in the later stages of Alzheimer's, but only an autopsy can reveal the neural plaques and tangles that make a diagnosis certain, if post-mortem. While there is no cure for Alzheimer's, early detection is important. Medication and lifestyle changes are sometimes able to slow degeneration, and even if these therapies are not effective, those with Alzheimer's may value the extra planning time that an early warning grants them. Alzheimer's is one of the most emotionally and economically costly diseases in the world, so a thorough care plan is crucial in making the 8-10 years before death as comfortable as possible for both the patient and the caregivers. That is why so many people are paying attention to a new fMRI study that took a different approach to picking up the earliest signs of Alzheimer's.
A decade of Alzheimer's devastates the mind and can leave sufferers unable to live without assistance, but its onset is insidious and easy to miss. The first symptom is usually memory impairment, but the problem develops so slowly that the occasional difficulty remembering a birthday or appointment is often overlooked by family and friends. Scientists have been trying to develop a more precise way to detect memory problems. If neural function changes at the earliest stage of memory impairment, or preferably even before memory impairment is noticeable on any task, then patients can receive a warning before the disease begins to appreciably impact their lives.
Dr. Jeffrey Petrella, from the radiology department of Duke University, published this recent interesting fMRI study in the newest issue of Radiology. He scanned 28 healthy subjects, 34 subjects with Mild Cognitive Impairment (thought to be a precursor to Alzheimer's because of similar memory problems), and 13 patients with symptoms severe enough that a diagnosis of Alzheime's could be confidently made. Dr. Petrella gave subjects common memory tests, but instead of scanning the regions of the brain that should be activated in those tasks, he had the novel idea to scan regions that should be inhibited while memories are stored and accessed. Those with Mild Cognitive Impairment showed less inhibition in the posteromedial cortices than controls, and this difference was even greater for those with Alzheimer's. Dr. Petrella speculates that Alzheimer's prevents the brain from muting the posteromdeial cortex, allowing its signals to interfere with memory tasks. This idea, if correct, should direct scientists to look at a failure to deactivate, rather than activate, crucial brain regions. As genetic testing alerts more people to their risk of Alzheimer's, techniques that can quickly assuage or confirm fears of dementia will become increasingly valuable.
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