I had a talk with Dr. Jennings (www.parkinsonstmj.com) who says that most PD is caused by trigeminal nerve dysfunction usually secondary to jaw malalignment.
See http://www.dentalphysician.com/www07...dparadigm.html

The hypertonic nerve increases substance P that manifests in, among many other things, over activation of the microglial cells in the brain. So it is usually a bite disturbance that causes the brain inflammation that progresses PD.

Is the hypothesis accurate? If you search Youtube for Parkinson's tmj you will find several amazing videos. Here is one: http://www.youtube.com/watch?v=no0ifu7Yzo4

More can be found at www.tmjstack.com