More recent efforts in PD have focused on using convection-enhanced delivery (CED) systems (Barua et al., 2013; Taylor et al., 2013; Whone et al., 2019) and gene therapy vectors [e.g., AAV2-GDNF - (Rocco et al., 2022; Heiss et al., 2024)] to improve distribution and achieve sustained expression in the putamen of treated patients. Here, GDNF is linked to Parkinson disease.