{{{GC, GF, and family}}} What an awful choice. I'm so sorry for everyone involved.
sj, I feel you. I am still not sure what the difference between senile dementia and Alzheimer's is, but my grandma developed it, and it was awful to see what it did to her. It was what she didn't want to happen, and it tore my dad up to watch it. Now that he's getting older, it is his, and now my, worst fear. It's horrible.
From what I have read. Alzheimer's is one of possibly many causes of dementia, which is the larger category. You really can't tell for sure if someone had Alzheimer's unless you do an autopsy, so a diagnosis is really just a guess on the part of the doctor that he/she thinks best explains the symptoms. Of course I could be totally wrong about all of that.
My step-grandmother had Alzheimer's, and it was just so awful. It remains a big fear of my mother's and my stepfather's as a result. I can tell they think about it everytime they forget where their keys are, etc.