According to a story in the New York Times, the FDA is getting closer to approving a scan that will help diagnose Alzheimer's disease. Right now, we can't definitively diagnose Alzheimer's disease until death, when an autopsy can be done. What a lot of people don't realize is that not only are there many types of dementia, but other treatable medical conditions mimic Alzheimer's.
Other types of dementia are related to vascular problems, such as having several small strokes, or Parkinson's disease. In these cases it might be possible to better treat the cause, especially with vascular dementia, to slow or stop the decline. Depression, which is very treatable, can also mimic the memory loss of Alzheimer's. Delirium is another condition that can look like Alzheimer's. Delirium is frequently caused by an infection, and infections are often successfully treated.
This is good news, because it gives doctors the potential to definitively rule Alzheimer's in or out, allowing them to properly focus their treatment. The article says full approval is still several months away, but it's certainly a great stride forward.