The Regulation of Plasma Interleukin-6 Levels Is Modified by Hippocampal Sclerosis and Its Lateralization in Drug-Resistant Temporal Lobe Epilepsy

Background. Several studies have reported the association of the proinflammatory cytokine IL-6 with temporal lobe epilepsy (TLE), but the regulation of IL-6 in hippocampal sclerosis (HS) is less studied. Objectives. To analyse IL-6 levels and the IL-6/IL-10 ratio in a larger, well-characterized group of patients with drug-resistant focal epilepsy (DRE), focusing especially on TLE and TLE-associated HS. Methods. IL-6 levels were measured by ELISA in plasma in a cross-sectional cohort of 265 patients comprising TLE with HS (n = 34), TLE without HS (n = 103), extratemporal lobe epilepsy (n = 92), and idiopathic generalized epilepsy (n = 36). Results. The IL-6/IL-10 ratio was higher in TLE with HS than in TLE without HS (3.1 vs. 1.6, p = 0.042), whereas the median levels of IL-6 did not differ among epilepsy types. TLE without HS patients had a higher proportion of increased IL-6 levels than TLE with HS patients (p = 0.021). Additionally, IL-6 levels were higher in patients with right-sided HS than in those with left lateralization (1.71 vs. 0.80 pg/mL, p = 0.04). In TLE with HS patients, IL-6 levels showed a negative correlation with seizure frequency during the last month (r = −0.342; p = 0.047), whereas in TLE without HS patients, the correlation was positive but did not reach significance (r = 0.136; p = 0.169). Conclusion. IL-6 levels and the IL-6/IL-10 ratio are differentially regulated among patients with TLE depending on the presence of HS and its lateralization, suggesting that TLE with HS is a distinct category regarding cytokine activation.