My TCM doctor told me that her daughter developed gluten sensitivity that didn't manifest as the usual enteric symptoms but as neurological ones. This is not uncommon. Though only 21 she moved like an 80 year old with shuffling gait as well as slurred speech and fatigue. These symptoms disappeared when she went on a gluten-free diet. That made me curious so I googled gluten and PD. There were a lot of links but two I found interesting. One said that Michael J. Fox's symptoms abated while visiting Bhutan where gluten is not found in the food (also verifying that dopaminergic cells are dormant, not dead). The other talked about gluten and GABA.

Here is an excerpt from that article:

"A key enzyme of the subthalamic nucleus (STN) is glutamic acid decarboxylase (GAD) that was mentioned earlier. GAD helps convert glutamic acid or glutamate into GABA. Glutamate is a most powerful neural stimulator and GABA is a most powerful neural inhibitor. In Parkinson’s Disease as well some other disorders, GAD levels drop causing an imbalance in the regulation of the conversion of glutamate to GABA disrupting the entire cascade.

I bring this up in the context of gluten sensitivity because according to the research of Dr. Marios Hadjivassiliou in the UK one common antibody created in the gluten sensitivity complex of antibodies is to the enzyme GAD. People who are gluten sensitive tend to increase production of the antibody to GAD. This is important not just in the basal ganglia but also other parts of the brain that are important for focus, learning and general movement control. Problems with gluten sensitivity leading to decreased GAD have been linked to ADD and ADHD, dementia, headaches, insomnia, cerebellar ataxia, Parkinsonian syndromes and others."

Gene therapy is aimed at restoring GAD, the better to produce more GABA. Acetylcholine tightens muscles and dopamine relaxes muscles. Normally, they are in balance but when dopamine gets depleted acetylcholine predominates leading to tremors and rigidity. Gamma-aminobutyric acid (GABA), is a chemical that reduces how sensitive muscle cells are to stimulation from the brain. It is also depleted in the brains of those with PD. Experiments using gene therapy to increase the brain's supply of GABA have been successful at controlling symptoms. Normally, synthetic GABA does not get into the brain if taken orally but a natural form (PharmaGABA) does and might be worth trying.
It might also be useful to go gluten-free for a while to see if it helps.