Parkinsons is Chiropractic and parasites. Unless he's a very indecisive person. Always fighting with himself. Am I right or am I wrong? Should I do it or not? Should I go or stay? That type of thing. Eventually that indecisiveness manifests in physical reality.
If not that, find a good chiropractor and get him on both Humaworm and Barefoots DeWormer.
Is he still mentally sharp??? If not, he'll need some colon cleansing. But usually Parkensions is a combination of upper cervical and parasites.
Drugs will NOT help and will lead to many other problems. Which is exactly what "They" want. Making tons of money drugging the seniors till they die.