GDNF is significant as it is considered a crucial agent for dopaminergic cells preservation, although its role in neurodegenerative diseases is not fully recognized—in Parkinson’s disease, it favors dopaminergic neuron survival, and, additionally, the results of certain studies based on a limited cohort of PSP patients suggest that GDNF release may be a mechanism contrary to the neurodegeneration process in PSP-RS [23,25]. Here, GDNF is linked to Parkinson disease.