In PPMS, CSF-NFL concentrations did not differ between treated or untreated patients (z = −1.0, p = 0.3) Figure 2, between patients with completely normal VEPs or only one eye with pathological VEPs (rho = −1.9, p = 0.05), and also not between study centers (p = 0.5); CSF-NFL concentrations were not related to disease duration (rho = −0.9, p = 0.5) or EDSS (rho = 0.17, p = 0.2) Figure 2. This evidence concerns the gene NEFL and primary progressive multiple sclerosis.