Interleukin-6 analysis of 572 consecutive CSF samples from neurological disorders: A special focus on neuromyelitis optica

Elevation of cerebrospinal fluid (CSF) interleukin (IL)-6 has been reported in various neurological disorders but has never been systematically analyzed. Our main objectives are to compare the CSF IL-6 levels among various neurological disorders and to evaluate the significance of CSF IL-6 measurements for the diagnosis of neuromyelitis optica (NMO). We retrospectively investigated the IL-6 levels of 572 consecutive CSF samples in patients with various neurological disorders. Additionally, the associations between clinical manifestations in NMO patients and CSF IL-6 levels were closely investigated. Among the neurological disorders, patients with NMO had the highest CSF IL-6 level. Receiver operating characteristic analysis found the optimal cutoff CSF IL-6 value for diagnosing NMO as 7.8 pg/ml, and the sensitivity and specificity were 0.7317 and 0.7694, respectively. In NMO, CSF IL-6 levels were correlated with the length of the spinal cord lesion and anti-aquaporin-4 antibody-positivity and decreased after treatment. CSF IL-6 can be high in various inflammatory and non-inflammatory CNS disorders, but its upregulation appears to be the most remarkable in NMO.