Traumatic brain injury (TBI) is a Public Health problem, because of the numbers of events (more than 200,000 per year in France). Craniocerebral tomodensitometry (CCT) is widely used for the diagnosis of minor/mild TBI, but both the access to the CCT and the cost of this imagery are critical factors. We hypothesized that the blood level measurement of S100 protein (S100), a neurological biomarker of cerebral injury, would help to the clinical evaluation of minor/mild head injury events, and would be an economic alternative to CCT for the diagnosis of these pathologies. In addition, a part of the study will explore the prognostic value of such blood level S100 determination for the evaluation of medical/social consequences of minor/mild TBI.