Background and purpose: We have previously demonstrated that stroke influences systemic immune responses. The aim of the present study was to investigate patterns of local inflammatory response as a consequence of acute stroke.

Methods: Thirty stroke patients were studied prospectively on days 0 to 3, 7 to 9, 21 to 26, and after day 90 with clinical evaluations, radiological assessments, and analysis of serum and cerebrospinal fluid cytokine levels.

Results: Significantly increased levels of interleukin-6 (IL-6) in cerebrospinal fluid (P < .001) were observed in virtually all patients studied compared with healthy control subjects. This increase was observed during the whole observation period but was significantly more pronounced within the first days after stroke onset, with a peak level on days 2 and 3. This initial increase was significantly correlated (r = .65, P = .002) with the volume of infarct measured by MRI 2 to 3 months later. Serum levels of IL-6 in stroke patients were significantly lower than cerebrospinal fluid levels of IL-6 (P = .013) and did not display any significant correlation to the size of the brain lesion. Also, increase in intrathecal but not systemic production of IL-1 beta was observed early during the stroke. Only minor increases of cerebrospinal fluid interferon-gamma levels were observed in two patients.

Conclusions: Our study demonstrates an intrathecal production of IL-6 and IL-1 beta in patients with stroke, supporting the notion of localized inflammatory response to acute brain lesion. In addition, the significant correlation between early intrathecal production of IL-6 and the subsequent size of the brain lesion can be used as a prognostic tool, predicting the size of the brain damage before it is possible to accurately visualize it with radiological methods.