BACKGROUND: The mechanism of development of delayed cerebral ischemia (DCI) 
after aneurysmal subarachnoid hemorrhage (SAH) is poorly understood. 
Inflammatory processes are implicated in the development of ischemic stroke and 
may also predispose to the development of DCI following SAH. The objective of 
this study was to test whether concentrations of circulating inflammatory 
markers (C-reactive protein (CRP), interleukin-6 (IL-6) and interleukin 1 
receptor antagonist (IL-1Ra)) were predictive for DCI following SAH. Secondary 
analyses considered white cell count (WCC) and erythrocyte sedimentation rate 
(ESR).
METHODS: This was a single-center case-control study nested within a prospective 
cohort. Plasma inflammatory markers were measured in patients up to 15 days 
after SAH (initial, peak, average, final and rate of change to final). Cases 
were defined as those developing DCI. Inflammatory markers were compared between 
cases and randomly selected matched controls.
RESULTS: Among the 179 participants there were 46 cases of DCI (26%). In primary 
analyses the rate of change of IL-6 was associated with DCI (OR 2.3 (95% CI 1.1 
to 5.0); p=0.03). The final value and rate of change of WCC were associated with 
DCI (OR 1.2 (95% CI 1.0 to 1.3) and OR 1.3 (95% CI 1.0 to 1.6), respectively). 
High values of ESR were associated with DCI (OR 2.4 (95% CI 1.3 to 4.6) initial; 
OR 2.3 (95% CI 1.3 to 4.2) average; OR 2.1 (95% CI 1.1 to 3.9) peak; and OR 2.0 
(95% CI 1.2 to 3.3) final value).
CONCLUSIONS: Leucocytosis and change in IL-6 prior to DCI reflect impending 
cerebral ischemia. The time-independent association of ESR with DCI after SAH 
may identify this as a risk factor. These data suggest that systemic 
inflammatory mechanisms may increase the susceptibility to the development of 
DCI after SAH.