The possible explanation of this effect is that CSF from patients with these conditions contains higher levels of growth factors and cytokines that promote cell proliferation, such as those previously shown to be present during regeneration after brain injury-FGF, NGF, TGF-β, GDNF, BDNF, VEGF, which possess neuroprotective properties, improve the survival and proliferation rate of neurons (Lehtinen et al., 2011). Here, GDNF is linked to brain injury.