Correlation between baseline CSF NfL levels and motor severity, which was assessed by total UPDRS scores (β = 0.223, P = 0.008), UPDRSIII (β = 0.218, P = 0.009), mean caudate SBR values (β = −0.118, P = 0.019), and mean striatum SBR values (β = −0.107, P = 0.034), remained significant in PD groups. The gene discussed is NEFL; the disease is Parkinson disease.