Association between cerebrospinal fluid interleukin-6 concentrations and outcome after severe human traumatic brain injury

Acute inflammation plays a significant role in the pathophysiology of traumatic brain injury (TBI). However, the specific relationships between inflammatory mediators and patient outcome following TBI have not been fully established. In this study, we measured plasma and cerebrospinal fluid interleukin-1 (IL-1) and interleukin-6 (IL-6) concentrations in 36 patients, following severe TBI. Patients were monitored with continuous measurements of somatosensory-evoked potentials (SSEP) to derive an established surrogate outcome measurement, the 96-h evoked potential (SSEP96). Clinical outcomes were assessed at 3 months using the Glasgow Outcome Scale (GOS). Peak cerebrospinal fluid (CSF) IL-1 and IL-6 concentrations were significantly higher than those observed in the plasma [median 6.5 pg/mL (range 1.4-25.0) vs. 3.0 (0.8-7.6) for IL-1, and 650 (130-7,214) vs. 253 (52-1,506) for IL-6, p < 0.001 for both]. Peak CSF IL-6 levels correlated with SSEP96 (r = 0.42; p = 0.0133), and peak CSF IL-6 levels were higher with improved GOS (p = 0.024). Multiple regression analysis identified that age (p = 0.0072), pupillary abnormality (p = 0.021), the presence of mass lesion (p = 0.023), and peak CSF IL-6 concentrations (p = 0.026) were all statistically significant predictors of clinical outcome following TBI. These results suggest that peak CSF IL-6 concentrations correlate with improved outcome following TBI. This finding helps to characterize the inflammatory reaction associated with TBI and may help to develop improved treatment strategies for patients with TBI.