They found a negative correlation between mPSPRS (Modified Progressive Supranuclear Palsy Rating Scale) and the glial cell-line-derived neurotrophic factor levels (GDNF) (r = −0.772727, p = 0.003) in the serum, a less pronounced negative correlation between progressive supranuclear palsy–quality of life parameter (PSP-QoL) and GDNF (r = −0.68390, p = 0.011) in the serum, and no correlations were observed in the analyses of inflammatory factors. Here, GDNF is linked to Classical progressive supranuclear palsy.