NEFL and Parkinson disease: More importantly, baseline CSF NfL levels were higher in the individuals with PD (99.9 pg/ml) than controls (98.7 pg/ml) (P = 0.024) [Figure 1B(a)], and CSF NfL levels were significantly elevated in men with PD (101 pg/ml) compared to women with PD (83.4 pg/ml) (P < 0.001) [Figure 1B(b)].