Schwarzschild and colleagues have already discovered one interesting chemical in the CSF of people with Parkinson's: urate, an antioxidant that may protect brain cells. In 2009, the scientists reported that, on average, people with plenty of urate in the CSF and blood tend to have a slower progression of Parkinson's than people with low urate levels.
That does not necessarily mean that urate levels are a direct cause or consequence of Parkinson's, Schwarzschild notes, and it is too soon to use urate alone to predict the course of disease. But he is now treating people with urate supplements in a small clinical trial to see if the treatment is safe and if it boosts urate levels in the blood and CSF of people with Parkinson's. If so, researchers will probably study whether urate supplements slow Parkinson's.
In many cases, biomarkers may be most helpful in predicting severity, not diagnosing disease, says neuroscientist James Connor of the Penn State Hershey Medical Center. For example, neurologists don't need much help diagnosing Lou Gehrig's, he says. But telling those patients what to expect is harder. Many patients die within a few years, but others may survive for a decade or more. "It matters to the patient: Are you on the three-year plan or the 10-year plan?" he says.
Connor is working to find biomarkers that may help doctors make those kinds of predictions. In 2009, he and colleagues reported that 11 proteins related to inflammation go up in the CSF of people with Lou Gehrig's.
In the future, doctors might even screen elderly people for biomarkers for Alzheimer's or Parkinson's, and treat the disease early just as they do for people with high cholesterol -- perhaps staving off or slowing diseases that, for now, are impossible to prevent.
"If we have a treatment that works even a little bit in people with the disease, it may work a lot better in people that do not yet exhibit signs of the disease," Snider says.