Outcome following severe traumatic brain injury TBI correlates with serum S100B but not brain extracellular fluid S100B: An intracerebral microdialysis study

S100B protein is released by astrocytes into the brain extracellular fluid following acute brain injury and elevated levels in CSF and serum have been shown to correlate with patient outcome following traumatic brain injury. A prospective study of brain extracellular fluid (ECF) and serum S100B levels in 12 patients with severe head injury (GCS ≤ 8) was undertaken using intracerebral microdialysis to investigate whether a correlation with ECF S100B and outcome could be confirmed. Patient outcomes were assessed at 6 months using the Glasgow Outcome Scale (GOS) and divided into two outcome groups: group A, 8 survivors with either a good recovery or moderate disability (GOS scores of 4 or 5); and group B, 4 patients who died (GOS 1). Peak serum levels of S100B were significantly greater in group B (mean 6.03 ng/ml) compared with group A (mean 0.73 ng/ml) (P = 0.009). Group A had a mean peak S100B in the extracellular compartment of 186 ng/ml compared to 150 ng/ml in group B. There was no significant difference between the mean peak brain ECF S100B concentrations for the 2 outcome groups (P = 0.932). We confirm that intracerebral microdialysis can be used to sample S100B concentrations from brain extracellular fluid and our results suggest that the ECF S100B levels were variable and that there was no significant difference between the good outcome and poor outcome groups. In contrast, the serum levels of S100B of patients with a poor outcome were significantly higher than those with a good outcome.