Early CSF inflammatory markers after aneurysmal subarachnoid hemorrhage and their relationship to disease severity and shunt placement

Abstract

Background: The inflammatory response within the central nervous system is a key driver of secondary brain injury after aneurysmal subarachnoid hemorrhage (aSAH). Less is known about the impact that inflammation has on complications like persistent post-hemorrhagic hydrocephalus. To explore the association between inflammation, disease severity, and permanent shunt placement, we characterized the early cytokine profiles of the blood and cerebrospinal fluid (CSF) of patients with aSAH.

Methods: Biological samples were collected from aSAH patients admitted to a single-center Neurosciences Intensive Care Unit between 2014 and 2024. Control CSF samples were collected from patients undergoing permanent shunt placement for normal pressure hydrocephalus. A multiplex bead-based immunoassay was used to analyze a panel of cytokines in plasma and CSF samples. Clinical variables, including demographics, disease severity, and permanent shunt placement were collected.

Results: Plasma and/or CSF samples were collected from 83 patients (58 aSAH patients, 25 controls). In aSAH patients, CC motif chemokine ligand-2 (CCL2), interleukin-6 (IL-6), granulocyte-colony stimulating factor (G-CSF), interleukin-8 (IL-8), and vascular endothelial growth factor (VEGF) were all elevated in CSF compared to plasma (p < 0.05 for all comparisons) and in the CSF of aSAH patients as compared to controls (p < 0.001 for all comparisons). However, only G-CSF and VEGF were associated with clinical severity at presentation when considering Hunt and Hess score as a dichotomized variable (p = 0.026 and p = 0.043, respectively). In multivariable models adjusted for age, sex, and modified Fisher Scale score, early CSF concentrations of IL-6 and IL-8 were associated with increased need for permanent shunt placement (p = 0.030 and p = 0.040, respectively).

Conclusions: Within 72 hours of aSAH, proinflammatory cytokines can be detected at higher concentrations in CSF than in plasma, and at higher concentrations in aSAH patients compared to controls. Early concentrations of certain pro-inflammatory cytokines are associated with increased likelihood of persistent post-hemorrhagic shunt dependent hydrocephalus, independent of initial disease severity. These data support preclinical models of CNS inflammation after aSAH and suggest that early innate inflammation contributes to hydrocephalus.

Keywords: cerebrospinal fluid; hydrocephalus; inflammation; subarachnoid hemorrhage.

Fig 1.

Comparison of cytokine concentrations between CSF and plasma samples. In CSF and plasma samples collected between day 0 and 3 after symptom onset, log concentrations of VEGF, IL-8, IL-6, G-CSF, and CCL2 were all significantly higher in CSF collected from aSAH patients (n = 58, n = 55 for VEGF, n = 57 for IL-8) compared to control CSF samples (n = 25) and plasma collected from aSAH patients (n = 18, VEGF not measured), as shown in heat map (A). (B) In paired CSF and plasma samples collected from the same patients with aSAH at the same time, log concentrations of CCL2, IL-6, G-CSF, and IL-8 were all significantly higher in CSF compared to plasma samples (n = 14). aSAH, aneurysmal subarachnoid hemorrhage; CCL2, C—C motif chemokine ligand-2; CSF, cerebrospinal fluid; G-CSF, granulocyte colony stimulating factor; IL-6, Interleukin-6; IL-8, Interleukin-8; VEGF, vascular endothelial growth factor.

Fig 2.

Comparison of CSF cytokine concentrations (A) In CSF samples collected from patients with aSAH and controls who were undergoing permanent shunt placement for normal pressure hydrocephalus, log concentrations of CCL2, IL-6, G-CSF, IL-8, and VEGF were all significantly higher in aSAH patient samples (n = 58, n = 55 for VEGF, n = 57 for IL-8) compared to control CSF samples (n = 25). (B) In univariate analyses, higher early log concentration of CSF IL-6 in patients with aSAH was associated with shunt dependent hydrocephalus (n = 58). aSAH, aneurysmal subarachnoid hemorrhage; CCL2, C—C motif chemokine ligand-2; CSF, cerebrospinal fluid; G-CSF, granulocyte colony stimulating factor; IL-6, Interleukin-6; IL-8, Interleukin-8; VEGF, vascular endothelial growth factor.