Researchers stopped treating Parkinson's Disease with brain cell transplants 14 years ago because it was largely unsuccessful and, in some cases, yielded negative side effects, like increased involuntary movement. But now they're giving an updated version of the transplant method another try, per NPR.
How it works: Parkinson's destroys cells that produce dopamine, which signals the brain's motor pathways to control how we move. Now, scientists are transplanting dopamine-producing cells into patients' brains to replace the ones that the disease destroyed. With new cells in place, the brain can control movement once again.