Well, we call it alzheimer, and due to his young age (63) it's categorized as early onset alzheimer, but one doctor said it looks like it really is multi infarct dementia (a.k.a. MID).
(Another doctor told us last week that you can only surely diagnose Alzheimer disease by autopsy.)
Not that it makes the pain or burden any easier... the symptoms are exactly the same... but now you know.