The electronic search was performed on databases, namely ScienceDirect, PubMed, and Google Scholar, by using search terms: ‘Definition of brain injury’, ‘Epidemiology of brain injury’, ‘Interleukin-1 in stroke’, ‘BDNF in stroke’, ‘Interleukin-1 in traumatic brain injury’, ‘BDNF in traumatic brain injury’, ‘Interleukin-1 level and robotic rehabilitation’, ‘BDNF and robotic rehabilitation’, 'Interleukin-1 level and neurorehabilitation', and ‘BDNF and neurorehabilitation’. Here, BDNF is linked to brain injury.