How does it work? 

DBS devices are typically placed in the subthalamic region of the brain, and the simulator sends out the pulses of electricity that alter Parkinson's effect on movement. What Stanford researchers−Henderson was a member of the research team− recently discovered is that those changes happen because the electrical pulses are picked up by neural wires, called axons, which run from that region to outer regions of the brain.

Who can it help? 

Stanford evaluates patients for two days, one day on their medication and one day off. DBS is most effective with people who have had a good response to medication, but whose ability to live their life normally has been severely hampered by the side effects of the medication. Those side effects include uncontrollable movements. On average, DBS gives patients a 60 to 80 percent improvement in symptoms and a 50 to 60 percent reduction in medication use.

Who can’t it help? 

DBS will not alter the effect of Parkinson's disease on speech or cognition. Nor is it effective on other movement disorders that may have some of the same symptoms as Parkinson's disease. It cannot help those who do not respond to medications.