@jmc247 I appreciate your knowledge as well as
@wiking. I have always worked in Emergency Medicine (first as a PJ, them as a paramedic and now as a PA in the ER). So I am not as educated as I wish in neuroscience, I have a lot of interest in it because my Wife had a seizure disorder, of course like anyone else on this site I love history. So I have looked at this and I even asked my Wife's Neurologist about it.
I have always been under the impression that Hitler was showing signs as soon as around the anschluss.
I agree with you about the Parkinson's diagnosis as much as we can diagnosis of historical people. I think given the proper medical care (as it stood then) and no war you get him to the late '40's. How coherent he could and effective he could have been? Who knows.
Given a cold war scenario, I would guess you have gotten the full cast of characters competing for it. What might have been interesting is that you might have had a situation where you had a Fuhrer, head of the party, a separate Chancellor and a ceremonial President. Maybe the Chancellor is the head of the party or not.