Clinical Use of the Calcium-Binding S100B Protein, a Biomarker for Head Injury.

S100B is a calcium-binding protein most abundant in neuronal tissue. It is expressed in glial cells and Schwann cells and exerts both intra- and extracellular effects. Depending on the concentration, secreted S100B exerts either trophic or toxic effects. Its functions have been extensively studied but are still not fully understood. It can be measured in cerebrospinal fluid and in blood, and increased S100B level in blood can be seen after, e.g., traumatic brain injury, certain neurodegenerative disorders, and malignant melanoma. This chapter provides a short background of protein S100B, commercially available methods of analysis, and its clinical use, especially as a biomarker in minor head injury.