Just to provide the counter-point: also possible that increased protein metabolism and synthesis (the defining feature of ketogenic diets) increases the likely hood of long -lived prions: proteins that fold abnormally, which can be learned by other newly synthesised proteins leading to these "mutant proteins" forming plaques on the brain (which is now burning protein for energy due to depletion of glucose).

And there might be a runaway/tipping point somewhere here: some amino acids have acidic metabolites and also need to capture hydrogen ions from red blood cells to metabolise/synthesise protein. Some of these metabolites also cause acetone build up in body, which starts to be expelled via lungs.

So combo of high rates of protein synthesis, abnormal blood plasma pH balance and increases cell oxidisation and anion gap == greater rate of prion formation and survival.

This is just a personal hypothesis, no real evidence to back it up. Just suggesting caution should be exercised here. PD is a horrible disease, I wouldn't wish it on my worst enemy.