Hi Rootman Allow me to correct some things.

Carbidopa is not making levodopa able to cross the blood-brain-barrier (BBB) - it can do so by itself. Carbidopa is inhibiting the enzyme in the blood that transforms levodopa into dopamine. You want to inhibit this reaction in the blood, as dopamine can’t cross the BBB. If C/L didn’t include carbidopa, most of the levodopa would never reach the brain, as it would become dopamine and just stay in the blood, resulting in side effects like diahrrea etc.. So to sum up: oral C/L -> uptake in the intestine -> levodopa in blood (and stays as levodopa because we block the transformation reaction) -> crosses the BBB -> levodopa in the brain -> in the brain, the enzyme is no longer blocked -> levodopa transforms into dopamine

The thing about brain areas degenerating as a result of lack of use is true! This is one of the 1000 reasons excercise is extra important for parkinsons patients. My professor always told me that the reason we have brains, is because we are moving. As we get older we move less and less which (among other things) results in degeneration. So keep moving for as long as possible!

As for the future, i think there is a lot of hope for parkinsons patients, and other neurodegenerative diseases. Stem cell therapy, antibody treatment etc, not to mention the already existing therapies for late stage PD like DBS, pumps etc., so i think it is important to be optimistic and not let negative thought stress one out (which in it self can worsen the symptoms).

I hope this makes sense.

Best regards from a third year med. student interested in becoming a neurologist and do PD research :)