On this, Deep Brain Stimulation (DBS) got through the FDA on special humanitarian permission. The effects of continuously electrically stimulating nuclei (the substansia nigra for Parkinson's DBS patients) are not known, but there is some evidence that the patients have to up the amperage and voltage over time. The reason is unknown, it could be due to death of neurons, or downregulation of the ion pumps in the cells, we just don't know. What we do know, is that for DBS patients, it is better than the alternative of the tremors and stress. Really, that is most of medicine in the end. It's kinda ritual. For a long time, we didn't know that silver or copper was antibacterial, but we knew that if you ate with it, you would get less sick, same with pewter pots leaching out lead with acidic compounds in the food.