NGF and Myelopathy: During the last two decades, much progress has been made in the field of neuroimmunology and have suggested that the pathogenesis of N2O-induced myelopathy could be explained by an imbalance between cytokines and growth factors exhibiting myelinotoxic (tumor necrosis factor alpha, sCD40:sCD40L dyad, nerve growth factor) or myelinotrophic (interleukin-6 and epidermal growth factor) effects [30,31,32,33,34].