sentence: Therefore , the feasibility of treating advanced patients with neurotrophic factors is questioned by recent data showing that : ( i ) tyrosine hydroxylase-positive putaminal innervation has almost completely disappeared at 5 years post-diagnosis and ( ii ) in patients enrolled in the rAAV-NRTN trial more than 5 years post-diagnosis , NRTN was almost not transported to the substantia nigra pars compacta .