I found your post via a search for 'abseil' as I've developed quite a taste for it. More on that later.
This reply is long so here goes
There's a saying 'if it looks like a duck, waddles, swims and quacks like a duck, it's a duck'. Add in something more surreal, but supposedly definitive like does it answer when you call it Daffy and suddenly it may not be a duck, but actually a Disney cartoon(ist).
Now, what the eck has that to do with PD? Well, PD is a condition usually 'diagnosed' by a person experienced in observing symptoms and the reaction to outside influence, be it manipulation of limbs or drugs.
Typical PD symptoms begin to become noticeable when it is thought at least 70% of the brain cells that produce Dopamine have either died or ceased functioning correctly. These cells are contained within the Putamen area of the brain and once cut open the PD diagnosis is final, literally. QED, the PD duck test.
MRI and DAT scans aren't definitive in PD diagnosis but could reveal brain irregularities that relate to your symptoms. Weakness on one side, facial expression as typical Stroke evidence. There is a PET scan using a radioactive isotope that does show up the activity of Dopamine producing cells but they take 2 hours laying as still as you can, NO breaks in the narrow tube style machine but NO noise above the gentle cooling fans. They are Torture if you have PD as you have to be off meds for them. Cost around £10,000 each I'm told. I've had 2 as part of the GDNF CED trial. I knew I had PD when those were done.
When to Medicate
Check you're doing all you can to be as healthy a person you can be who also has PD. Brains and bodies are in essence an ageing machine. It will break down but you can influence the route if not the destination.
Staying healthy is more a state of mind than many give credit to. No point being perfect this or that if you're stressed out by what you eat or do.
Life is a balance between living and existing. If you have PD the medications available help you live not simply exist. An initial level of medication will require increasing in most cases, as and when more brain cells stop working, not because you began them too soon
My theory is that the link to Dopamine production may be why some people have young onset. In my theory, excluding traumatic damage, the brain cells die at roughly the same rate for all but young onset people are simply more sensitive to the reduction in dopamine production dropping. They may not have lost 70% and could benefit most from any treatment that can slow, pause, stop or even reverse the cell loss.
Treatment / Stages 1, 2, 3.....
Observe, medicate, evaluate, review medication, observe, tweak, increase. Manage symptoms on a 'fire fighting' basis.
This is where everyone needs to do their bit in taking responsibility for keeping your specialist and support team up to date on your symptoms pre and post meds, your dietary and activity schedule plus ANY suspected reactions.
The symptoms of PD are many and varied, drugs that work for one person may not work for others with the same symptoms.
You can view diagnosis as the end. For me, It was more like knowing I'm not going to win the marathon of longest life. Yes, it's a shock, unwanted and is going to affect everyone and everything I know. It was an opportunity to take a different route.
To quote Parkinson's UK:
This simple but powerful approach gives you as much control as you want or need.
I don't have wings but the view as I stepped out onto the abseil platform of the Spinnaker Tower was one those Matrix moments
Now for the non Matrix fans. I never ever thought I'd quote Keith Harris
I wish I could fly............but I can't, You can
Orville is a duck.......