The patients, half of whom live on Long Island, are in advanced stages of the illness and were no longer responding to medicines when they signed on for the experimental therapy. The study was conducted by Andrew Feigin, MD, director of Neuroscience Experimental Therapeutics at The Feinstein Institute for Medical Research and his colleagues in collaboration with Parkinson's scientists at New York Presbyterian Hospital-Weill Cornell Medical Center in Manhattan.

One woman and 11 men received a surgical infusion of fluid containing a viral vector and genes for a protein called GAD, glutamic acid decarboxylase. This enzyme is critical in controlling a neurotransmitter called GABA. In Parkinson's, GABA is reduced in an area of the brain called the subthalamic nucleus. This region is working on overdrive in the disease process and GABA is an inhibitory transmitter and is important in trying to calm this hyper-reactive circuit.