Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality worldwide. The consequences of a TBI generate the activation and accumulation of inflammatory cells. The peak number of neutrophils entering into an injured brain is observed after 24 h; however, cells infiltrate within 5 min of closed brain injury. Neutrophils release toxic molecules including free radicals, proinflammatory cytokines, and proteases that advance secondary damage. Regulatory T cells impair T cell infiltration into the central nervous system and elevate reactive astrogliosis and interferon-γ gene expression, probably inducing the process of healing. Therefore, the neutrophil-to-lymphocyte ratio (NLR) may be a low-cost, objective, and available predictor of inflammation as well as a marker of secondary injury associated with neutrophil activation. Recent studies have documented that an NLR value on admission might be effective for predicting outcome and mortality in severe brain injury patients.
Keywords: NLR; TBI; brain injury; lymphocytes; mortality; neutrophils.