Level of IL-6 in cerebrospinal fluid is a preoperative predictor of short - term outcome in acquired hydrocephalus

Abstract

Background: Acquired hydrocephalus (AH) is a common complication in patients with severe brain injury. Brain tissue injury has been proposed to induce a neuroinflammatory reaction reflected by cytokines release, particularly interleukin-6 (IL-6), which associates with early brain damage. The present study measured IL-6 in the cerebrospinal fluid (CSF) of AH patients and determined its relationship to functional outcome following shunt operation.Methods: The study included a total of 32 patients with a shunt operation due to hydrocephalus. CSF samples from 26 AH subjects and 6 iNPH patients were collected via lumbar puncture before surgery. IL-6 level was measured using the micro ELISA immunoassay method. AH subjects were dichotomized into good versus poor outcomes based on modified Rankin Scale (mRS) at 3 months after shunting.Results: CSF analysis demonstrated that IL-6 was significantly elevated in the CSF of the AH group compared to controls (p = 0.023). Within the AH group, eighteen (69.2%) had a good outcome while eight (30.8%) patients had a poor outcome. Mean IL-6 level in the good outcome group was approximately four-times higher than the poor outcome group (p = 0.004). Glasgow Coma Scale (GCS) on admission was significantly different between the two groups (p = 0.014). IL-6 level and admission GCS were significantly correlated with improvement of mRS score (r = 0.473, p = 0.015 and r = 0.691, p＜0.0001, respectively). Receiver operating characteristic curve analysis showed that both factors can accurately differentiate between patients with good versus poor functional outcome (AUC = 0.861, p = 0.0039 and AUC = 0.823, p = 0.0098, respectively). Conclusions: The CSF level of IL-6 is elevated in AH patients and higher levels correlate with improvement of post-shunt functional outcome. Therefore, IL-6 CSF level might serve as a complementary surrogate parameter for operative indication. A possible IL-6 threshold in clinical routine might be a 6.98-pg/ml cutoff value to rule out unresponsive and poor outcome AH patients that are under the 6.98-pg/ml threshold.