You can check for amyloid plaques in an autopsy, but apparently plenty of old people that show no significant cognitive decline also have amyloid plaques. So,

You can check for amyloid plaques in an autopsy, but apparently plenty of old people that show no significant cognitive decline also have amyloid plaques. So, while we would definitively call it Alzheimer's if you have significant cognitive decline + amyloid plaques, it's not 100% clear that this is a single diagnostic.