TNF and amyotrophic lateral sclerosis: A recent meta-analysis involving 25 studies on peripheral cytokines levels in ALS confirmed that tumor necrosis factor-alpha (TNF-alpha), TNF receptor 1 (TNFR1), interleukin 6 (IL-6), IL-1β, IL-8, and vascular endothelial growth factor (VEGF) measured in blood were significantly elevated in ALS cases compared with controls (16).