NGF and Cerebral atrophy: In MS patients, the influx of peripheral blood mononuclear cells (PBMC) to the CNS can compensate for the deficiency of neuroprotective factors, in particular, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and neurotrophin 4/5 (NT-4/5), reducing the rate of cerebral atrophy.