The aims of this study were to investigate (i) whether CSF levels of contactin-1 and contactin-2 are reduced in CSF of PD patients, (ii) whether contactins can discriminate PD patients from controls and DLB patients, and (iii) their relationship with clinical outcome measures of disease severity, and with CSF markers of neurodegeneration α-syn, tTau and pTau, which are also associated with synucleinopathies [22,23]. Here, CNTN2 is linked to Parkinson disease.