Hand and body shaking and general instability

[MayaElz]

My father is 74 years old, a retired carpenter. Around 5 years ago he was diagnosed with early stage prostate cancer which he treated with chemo/radio therapy. Since then he has had issues with his bladder and relies on disposable underwear, but more concerning is his body shakes like someone with parkinsons and often falls. He also has low energy. He has been investigating his symptoms with several doctors and specialists (neurologists) or a couple of years now and they are all at a loss. His blood work comes back fine. He has also had a few MRI's of the brain that show nothing unusual. We feel he is deteriorating and may need a wheelchair in the near future. We would truly appreciate some suggestions on which path to take next