BACKGROUND: This study examines the inflammatory response via interleukin-6 
(IL-6) in aneurysmal subarachnoid hemorrhage (aSAH) patients and its association 
with their clinical course (occurrence of acute focal neurological deficits, 
AFND; and delayed cerebral ischemia, DCI).
METHODS: A total of 38 consecutive aSAH patients were studied prospectively 
within 14 days after admission and classified as asymptomatic (n = 9; WFNS grade 
1 (1-2), median and quartiles) and symptomatic (n = 29; WFNS grade 4 (2-5)); the 
latter presenting with AFND (n = 13), DCI (n = 10) or both (n = 6). Levels of 
pro-inflammatory cytokine IL-6 were determined in cerebral extracellular fluid 
(ECF, using cerebral microdialysis), cerebrospinal fluid (CSF) and plasma for 10 
days after aSAH. Additionally, C-reactive protein (CRP) levels were measured in 
plasma.
RESULTS: High IL-6 levels in CSF, ECF and plasma were found in all patients, 
reflecting a pronounced local inflammatory response after aSAH, followed only in 
symptomatic patients by a delayed systemic inflammation (CRP P < 0.025, days 7-9 
after aSAH). In all compartments, IL-6 levels appeared to be higher in 
symptomatic patients, accompanied also by a higher ECF lactate-pyruvate ratio (P 
= 0.04). Cerebral, but not plasma IL-6, levels were indicative of the 
development of DCI in symptomatic patients (ECF P = 0.003; CSF P = 0.001).
CONCLUSIONS: A pronounced initial cerebral inflammatory state was observed in 
patients of all WFNS grades, suggesting that IL-6 elevations are not necessarily 
detrimental. Cerebral, but not plasma IL-6, levels were predictive of the 
development of delayed ischemic deficits in symptomatic patients, suggesting 
that CSF or ECF are the best sampling media for future studies.