Imad-
I sometimes have a hard time following me too.
While I have calmed down a little, I still find this to be very interesting. I don't know enough to have a position on these particular folks or even on the TMJ involvement, but I do think the following points are very important-
1) the recognition of the importance of the sole of the foot as the beginning point of the return half of the feedback loop that maintains posture. PD is referred to as a problem with motor function and we often forget that we have to have not only instructions going to the muscle but also reports of action and position coming back to the brain. The recognition by the brain (whether fact or illusion) would certainly trigger a stress response. Consider the stress levels associated with driving a car on a rainy night with a dirty windshield vs a clean one, for example.
2) this could come on slowly over several years and be hardly noticed. How vulnerable are the neurons of the SN to stress hormones?
3) to me this goes a long way toward explaining why we are so stress sensitive in the latter half of PD yet seemingly not in the first half. Rather than viewing it as just one more system succumbing to the onslaught, it may be more accurate to see it as part of the causative force itself.

As for practicle applications, how about "Don't worry. Be happy." ??