Why one side
 

Any thoughts on why PD predominantly starts on one side?

She's right hand dominant and I'm left
 

I often wondered about this too, or why my friend Maureen is my mirror opposite. She's right hand dominant and I'm left though we are both right handed.

Here's an abstract on the subject that takes a lot of breath to say "we don't know:"

http://www.sciencedirect.com/science...26f8d7b59da8e3

Guy

If you go with the Vagus Nerve Theory, then:
 

...the explanation would go something like this: There are three main branches of the vagus nerve, and the third branch has two branches that travel nearly throughout the entire body.One branch is vulnerable to inflammation from toxins, bacteria, viruses, etc. as it leaves the thorax and tavels close to the lungs, heart and components of the digestve system, while the other wanders around the pharynx, larynx and various other cranial components. These are left and right, affecting the corresponding limbs of the body but not necessarily the same-side organs of the body. I have counted at least 11 secondary symptoms that might appear with the primary symptoms of Parkinson's (including problems with swallowing, speaking, heart, lungs, peristalsis, digestion, smell, temperature control, and thyroid). Some of these secondary symptoms present if the right branch is affected, while others present if the left is affected. Since the two sides do branch from one of the 3 vagus nerve brnches, the eventual presentation will be bi-lateral unless the source of the inflammaion is discovered and stopped before that happens. The side that is affected first is dependent upon whether the inflammatory substance enters the body via ingestion, inhalation, absorption or through the skin, or through the umbilical cord. The branch affected would be the one that is in close proximity to the components of the compromised or insulted system.

That is the way I see it anyway. Here is a website that explains the vagus nerve more thoroughly.
The Vagus Nerve

michael b.

just a note
 

Mine started out on the right involving first my right hand then my right leg. I got really nervous (poor choice of words) when I noticed my left leg getting into the act. However what happened was I got a terrible tremor in both my legs but the tremor in my upper body disappeared completely for 8+ years. Just recently it has reappeared in my right hand/arm. But if my arm kicks in my legs often stop. At any given time I only have two limbs involved with tremor. It's a bit of a lottery to guess which two it will be today. Welcome to "Wonderland" ....that's the place we all stand around and wonder what the hecks going on here anyway???? :eek::eek::eek::eek:

When we say that PD starts on one side, are we mostly referring to specific symptoms?

AT the beginning.......
 

One notices PD symptoms usually on one side of the body, this is called "hemiparkinsonism", where "hemi" means "half".
It is this way because the brain is naturally divided into two "hemispheres" the left side of the brain controlls the right side of the body and the right side of the brain controlls the left side of the body.
Just like we have two eyes, the structures in the brain that die off are two pea size peices of tissue that compose the "substantia nigra". Usually, for reasons unknown , the dopaminergic cells in one of the pea like structures in one of the brain hemispheres die off at a greater rate than in the other half of the brain. Eventually, we lose a critical amount of cells in the other half too, and this is known as becoming "global". This means that both sides of the body suffer PD symptoms.