Diagnosis after Death
The hallmark of Alzheimer’s Disease is the accumulation of beta-amyloid and tau protein in the brain that forms plaques and tangles respectively. These prevent neurons from communicating and functioning normally, which results in connection and neuronal loss. Until very recently, amyloid plaques could be determined only after death, by examining the brain during an autopsy. This is why clinicians are usually cautious and diagnose memory loss as probable Alzheimer’s. Such inability to reliably diagnose patients in the early stages of Alzheimer’s disease may have hampered research. Indeed, it is possible that some of the drugs being researched are not efficient because they are tested in patients who have already progressed too far in the disease.
Diagnosis with a Brain Scan
The use of a radioactive agent that allows amyloid plaques in the brain to be observed with a scan could greatly boost research and treatment.
This is exactly what the test approved on April 6th 2012 by the Food and Drug Administration does. The test was developed by Eli Lilly & Co. and uses a chemical called florbetapir (brand name Amyvid), which is a radioactive agent that tags clumps of amyloid. The chemical can be detected using a brain imaging technique called positron emission tomography (or PET scan). Amyvid, which costs $1,600 per dose, will be available in limited quantities starting in June
For patients who already have some symptoms of cognitive decline, a positive scan suggests that moderate to frequent amyloid plaques are present in the brain, which is consistent with Alzheimer’s disease. A negative scan (indicating no or flew clumps of amyloid) suggests that Alzheimer’s is unlikely and that other potential causes for the memory decline should be explored.
What if someone does not show any memory decline? Could the new technique be used to diagnose Alzheimer’s? The answer is no.
The presence of amyloid in the brain does not alone suggest that someone has Alzheimer’s. Indeed, it is known from autopsies that 20% of cognitively healthy older adults do have large quantities of amyloid in the brain.
This new technique may accelerate research by helping to accurately identify people at high risk of developing the condition and to enroll such people in therapeutic trials. It also may be useful in tracking disease progression in the brain.
Note that training will be necessary so that physicians can accurately read the scans. Amyvid was rejected last year because the FDA thought Lilly needed a better training program in place to make sure different doctors come to similar conclusions when they read the scans. A three-hour online and in-person training programs is now available for physicians.
Of course, there is no treatment available yet but an early diagnosis may be helpful for planning purposes. Since lifestyle factors can also affect brain health, an early diagnosis may also help individuals identify in which areas of their life they could make changes. Specifically, a change toward a more balanced diet and an increase in mental and physical exercise may prove useful.
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