sentence: These data demonstrate that the extent of neuronal death at the time of symptoms onset is only 30 % whereas putaminal DA levels were 50 – 70 % reduced , suggesting that axon terminals become dysfunctional prior to cell death.Post-mortem analysis of four patients enrolled in the AAV2-NRTN trial , showed that although surviving melanin-positive dopaminergic neurons were still present in the SNpc , TH-positive dopaminergic terminals in the putamen were very sparse and NRTN transport from the putamen to the SNpc was very slow and inefficient ( Bartus et al ., 2011 , 2015 ) .