Personalized medicine in traumatic brain injury.

Patients who have sustained a mild traumatic brain injury (TBI) from both civilian and military populations exhibit clinical symptoms of varying severity with minimal to profound impact on their daily functioning. Although most patients make a full recovery, a subgroup of mild TBI patients develop cognitive, somatic, and neurobehavioral sequelae that generally resolve over 3 to 6 months; a smaller subgroup develop persisting symptoms. The reason why a mild TBI results in varying clinical symptoms is currently unknown. Based on evidence that microRNA species in peripheral blood mononuclear cells (PBMCs) may reflect molecular alterations in neurodegenerative disorders, it can be hypothesized that at early, preclinical phases of the disease, PBMC may provide an ideal and clinically assessable "window" into the brain. Thus, it is conceivable that changes in the expression profile of clinically accessible biological indices (biomarkers), such as microRNA in PBMC, may reflect molecular alterations following TBI that contribute to the onset and progression of TBI phenotypes including chronic traumatic encephalopathy. It is possible that the availability of TBI biomarkers may provide potential elements with clinical relevance to prevention, prognosis, and treatment of postconcussive disorders.