Objective: To investigate serum levels of cortisol (a biochemical marker of stress), S-100B and neuron-specific enolase (two biochemical markers of brain tissue injury), in acute phase in mild traumatic brain injury patients and the occurrence of post-traumatic stress-related symptoms 1 year after the trauma.
Methods: Blood samples were taken in patients (n = 88) on admission and approximately 7 hours later for analysis. Occurrence of post-traumatic stress-related symptoms was assessed for 69 patients using items from the Impact of Event Scale questionnaire (IES) at follow-up at 15 +/- 4 months after the injury.
Results: Serum levels of cortisol were more increased in the first sample (cortisol/1, 628.9 +/- 308.9 nmol L-1) than in the second blood sample (cortisol/2, 398.2 +/- 219.4 nmol L-1). The difference between these samples was statistically significant (p < 0.001). Altogether 12 patients (17%) showed post-traumatic stress related symptoms at the time of the follow-up. Stepwise forward logistic regression analysis of symptoms and serum concentrations of markers revealed that only S-100B in the second sample was statistically significantly (p < 0.05) associated to symptoms (three symptoms of the avoidance sub-set of IES).
Conclusion: A major increase in serum concentrations of cortisol indicates that high stress levels were reached by the patients, in particular shortly ( approximately 3 hours) after the trauma. The association between the occurrence of post-traumatic stress related symptoms and serum levels of S-100B (generally considered as a biochemical marker of brain injury) seem to reflect the complexity of interactions between brain tissue injury and the ensemble of stress reactions.