Interleukin-6 levels are increased in temporal lobe epilepsy but not in extra-temporal lobe epilepsy

Previous studies have reported activation of inflammatory cytokines in seizures, but clinical characteristics of epilepsy associated with cytokine activation have not been well established. In this study, serum levels of interleukin-6 (IL-6) and interleukin-1 receptor antagonist (IL-1RA) were measured, and clinical characteristics of epilepsy were assessed in 86 well-evaluated patients with refractory focal epilepsy and in 5 patients with controlled focal epilepsy. Epilepsy was evaluated based on patient histories, electroclinical findings, and high-resolution brain MRI scans. Sixty-three healthy blood donors served as controls. IL-6 concentrations were chronically increased in epilepsy patients (11%) compared with healthy controls (0%) (P = 0.007). Increased levels of IL-6 were more prevalent in patients with temporal lobe epilepsy (TLE) compared to patients with extra-TLE (P = 0.028). Also the mean and the median serum levels of IL-6 were higher in patients with TLE than in patients with extra-TLE (P = 0.042). Concentrations of IL-1RA were not significantly different in patients compared with controls. Indicated by increased levels of IL-6 in TLE, epilepsy type is important in determining chronic overproduction of cytokines in refractory focal epilepsy. The results may reflect a chronic immunological process in the brain in patients with refractory epilepsy.