The serum and CSF concentration of S100B increases after traumatic brain injury (TBI), but its role in clinical practice is uncertain, especially in mild TBI.

S100 proteins are group of calcium binding proteins present within glial and Schwann cells. After acute injury the protein may be released, increasing its concentration in serum and CSF.


Its half-life in serum is 20-25 minutes. Units are in micrograms per liter.


The serum level is affected by:

(1) age of the patient

(2) time between TBI and blood sampling

(3) extracranial sources

(4) severity of TBI


For a patient with TBI serum levels are measured on admission, every 4 hours in the 24 hours after injury and then every 24 hours for several days. This continued monitoring can detect neurological complications.


The presence of a normal serum S100B may support a decision not to perform a head CT in the presence of supporting clinical evidence. The Cobas algorithm for serum: if the GCS is 13 to 15 and if the serum S100 is low within 3 hours of trauma, then the risk of intracranial lesions is very low.


The higher the serum concentration of S100B the worse the prognosis. The concentration is higher in severe trauma, associated with a low GCS on admission.


However, patients with an elevated values have had a complete neurological recovery.

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