ObjetiveThis study was performed to examine both brain and systemic interleukin-6 (IL-6) release in patients with an acute brain injury (ABI), to study whether a correlation exists between the transcranial IL-6 gradient during the first days after injury and prognosis, and finally, to investigate the relationship between a nucleotide polymorphism at position −174 in the promoter of the gene encoding IL-6, IL-6 responsiveness, and clinical evolution.DesignProspective clinical investigation.SettingA 19-bed intensive care unit in a university hospital.Patients and MethodsA total of 62 patients were followed up for 3 days after acute brain injury, and both their arterial and jugular IL-6 levels were measured serially and at the moment of brain death diagnosis. Genetic polymorphism of IL-6 was also determined in all patients. Data were correlated with those from score procedures for clinical severity. Neurologic outcome was graded according to the Glasgow Outcome Scale 6 months after injury. IL-6 levels and IL-6 genotyping was performed in control healthy individuals.Main ResultsThere is a significant transcranial IL-6 gradient at admission and at the moment of brain death. The gradient is higher in those patients who evolved toward a fatal outcome during the first 6 months after injury (p< .001). There is significant correlation between the transcranial IL-6 gradient and the acute brain injury severity.ConclusionsIL-6 is elevated in patients with acute brain injury, and a significant relationship exits between the severity of acute brain injury and the transcranial IL-6 gradient at admission. It can be considered to be a prognosis marker at admission. When data at the moment of brain death are considered, venous IL-6 (p< .01) and the transcranial IL-6 gradient (p< .005) are significantly higher than at the time of admission. Although the IL-6 C allele is associated with significantly lower concentrations of IL-6, there was no correlation between low or high IL-6 responders and patient outcome.