Why is it so hard to diagnose early on-set Alzheimer’s?

It is hard to diagnose as there is no known cause or explanation of dementia, there is no known cure – in fact, we don’t really know anything about the disease. My wife had a very rare type of Alzheimer’s in where her first signs were not physical but visual. Almost a year later we got a proper diagnosis from a neurologist who was no help in how we should go about after-care. There was no follow through – because the truth is – nobody really knows.