Disease outcome, alexithymia and depression are differently associated with serum IL-18 levels in acute stroke

Stroke has been shown to lead to depressive disorders, anxiety disorders and other emotional consequences. Although the cause of these disorders is a subject of debate, stroke has clearly been shown to lead to the production of pro-inflammatory cytokines, which we hypothesized to play a role in the production of post-stroke emotional disorders. Thus we investigated here whether acute stroke might be associated with changes in the normal serum levels of IL-18 and if these changes were related to stroke severity, as well as to the presence and severity of alexithymia and depression. Thirty patients with a first-ever symptomatic ischemic stroke were included. Alexithymia (Toronto Alexithymia Scale; TAS-20), depression (Hamilton Depression Rating Scale; HDRS-17) and serum IL-18 were assessed. Stroke patients showed serum levels of IL-18 significantly related to stroke severity. Furthermore, a strong positive correlation was observed between IL-18 levels and severity of alexithymia, particularly among patients with right-hemisphere lesions. Specifically, circulating concentrations of IL-18 were significantly increased in patients with categorical alexithymia (TAS-20 score ≥61), as compared with both non alexithymic patients and control subjects. In addition, stroke was more severe in alexithymic patients, as compared to non alexithymic patients. Following multivariate regression, serum IL-18 levels appeared to be specifically associated with alexithymia rather than with stroke severity in patients with right-hemisphere lesions only. These results suggest that IL-18 might be specifically implicated in the pathogenesis of poststroke alexithymia, ultimately contributing to impaired recovery from stroke.