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.
Then the video jumps forward in time. The same man appears, still off medications. It is now eight years since Mendez transplanted dopamine cells from a fetus into the patient's brain. These neurons, which live in a midbrain region called the substantia nigra and secrete the neurotransmitter dopamine to initiate movement, are the ones that die off in Parkinson's. The man has aged, but his energy and demeanor are characteristic of a much younger man. Asked to do the same tasks, he smoothly raises his arms high and flicks his fingers open and shut rapidly. Arms crossed on his chest, he rises from a chair with apparent ease. Then he struts down the hall.