Neurosurgeon Ivar Mendez of the University of Saskatchewan often shows a video clip to demonstrate his work treating Parkinson's disease. It features a middle-aged man with this caption: “Off medications.” The man's face has the dull stare typical of Parkinson's. Asked to lift each hand and open and close his fingers, he barely manages. He tries but fails to get up from a chair without using his hands. When he walks, it is with the slow, shuffling gait that is another hallmark of Parkinson's, a progressive neurological disorder that afflicts an estimated one million Americans, most of them older than 60.