Serial CSF and serum IL-6 and neuron-specific enolase after aneurysmal subarachnoid hemorrhage: temporal profiles and association with discharge outcome

Background Inflammation and neuronal injury contribute to secondary brain injury after aneurysmal subarachnoid hemorrhage (aSAH). We examined whether serial cerebrospinal fluid (CSF) and serum interleukin-6 (IL-6) and neuron-specific enolase (NSE) concentrations change over time after aSAH and whether these unadjusted biomarker patterns are associated with discharge outcome. Methods Seventy-five patients with aSAH underwent serial biomarker assessment across predefined hospital windows: days 1−3, 4−13, and 14−30. Outcomes were dichotomized by discharge modified Rankin Scale (mRS 1−3 vs 4–6). CSF/serum ratios were interpreted as compartmental gradients, not direct evidence of blood-brain barrier dysfunction. Results CSF IL-6 increased from 124.7 ± 57.5 pg/mL on days 1–3 to 464.2 ± 38.7 pg/mL on days 4–13 (p < 0.01). During days 4–13, CSF IL-6 was higher in patients with unfavorable versus favorable outcomes (671.0 ± 67.4 vs 347.8 ± 42.8 pg/mL; p < 0.01), whereas NSE was numerically higher but not statistically significant (21.3 ± 7.0 vs 10.0 ± 1.5 ng/mL; p = 0.15). Serum IL-6 was also higher in the unfavorable group (27.0 ± 9.6 vs 8.8 ± 1.3 pg/mL; p = 0.03). Two patients had intracranial nosocomial infections, both with unfavorable outcomes. Conclusions CSF IL-6 showed the clearest temporal rise and strongest unadjusted association with unfavorable discharge outcome. NSE provided complementary neuronal-injury information but was less discriminatory. Findings should be interpreted cautiously because of the observational design, modest subgroup sizes, and heterogeneous CSF sampling route.