Neuronal-specific enolase (NSE) is a subunit of the enolase group specific for the central neural system, found in the neurons and the neuroendocrine tissue of the brain. NSE is released as a result of leakage across the injured neuronal membrane; elevations of serum NSE are due to neuronal injury and increased permeability of the blood–brain barrier. Protein S-100 (especially the B subunit) is a calcium binding protein found in high concentrations specifically in neurogliar and Schwann cells. Procalcitonin (PCT) is the precursor of calcitonin and under normal conditions it is not detected in the plasma (0–0.5 ng/ml). PCT is elevated in microbial sepsis and trauma.