This is a terrific site for hearing frank, revealing discussion by iminent scientists on the difficult problems that face them in sorting out what is happening in PD from early on (pre-tremor, pre-rigidity, etc) to the visible clinical stages that are accepted as applicable to diagnosis. I really learned a lot from listening to the discussion on non-motor symptoms and the mysteries that persist regarding the mechanisms underlying them. The concensus is that they are non-dopaminergic in origin.
My vote is in favor of neuroinflammation.

Robert