AUCs values for CSF levels of RTN4 were slightly higher in comparison to classical biomarkers in MS patients as compared to the Controls (AUC = 0.749, p < 0.001 vs. tau—AUC = 0.698, pTau181—AUC = 0.566, Aβ1-42/Aβ1-40 ratio—AUC = 0.653) and in PD versus Controls (AUC = 0.847, p < 0.001 vs. tau—AUC = 0.687, pTau181—AUC = 0.639, Aβ1-42/Aβ1-40 ratio—AUC = 0.739). Here, RTN4 is linked to Parkinson disease.