[S100B protein: a novel biomarker for the diagnosis of head injury]

Acute head injury is a common reason for seeking care in an emergency department and in France accounts for more than 500 consultations daily. In most cases, though the trauma is minor/moderate, a computed tomography scan is necessary to establish the diagnosis and avoid medical and/or social sequelae. This examination is however expensive and not always readily available in the emergency setting. Until recently clinical chemists were unable to propose to physicians a pertinent biomarker of acute brain injury. S100B protein is a constitutive protein of glial cells, whose physiological functions are both intracellular, i.e. intracytosolic calcium binding, and extracellular, e.g. by promoting neuritic proliferation and/or neuronal apoptosis. Due to specificity of its cellular expression, S100B protein is a useful biological marker of acute neurological disorders, such as ischemic or hemorrhagic stroke, and traumatic brain injury. This brief review exposes the contribution of S100B measurement in biological fluids to the diagnosis, the follow-up, and the prognosis of acute minor/moderate head injury. In addition, we describe the French STIC-S100 study, a cohort study designed to determine the negative prognostic value of early determination of plasma S100B levels for the diagnosis of minor/moderate head injury and its medical/social consequences.