The Mc Master University database using Ovid/MEDLINE database was searched for articles published between 1946 and July 2013 using the following combination of the terms: cognitive impairment, traumatic brain injury, cytokines (IL-1, IL-6, IL-8, and TNF-a), neuroinflammation, concussion like symptoms, blood brain barrier, systemic inflammatory response, and polytrauma. The gene discussed is TNF; the disease is brain injury.