Etiology is the key determinant of neuroinflammation in epilepsy: Elevation of cerebrospinal fluid cytokines and chemokines in febrile infection-related epilepsy syndrome and febrile status epilepticus

Objective: To investigate intrathecal inflammation using cerebrospinal fluid (CSF) cytokines and chemokines in a subgroup of pediatric epilepsy patients with frequent daily seizures.

Methods: We measured 32 cytokines/chemokines using multiplex immunoassay in CSF collected from pediatric patients with febrile infection-related epilepsy syndrome (FIRES)/FIRES-related disorders (FRD; n = 6), febrile status epilepticus (FSE; n = 8), afebrile status epilepticus (ASE; n = 8), and chronic epilepsy with frequent daily seizures (n = 21) and compared the results with noninflammatory neurological disorders (NIND; n = 20) and encephalitis (n = 43). We also performed longitudinal CSF cytokine/chemokine studies in three cases with FIRES/FRD.

Results: The median age of onset of seizures was 2.4 years (range = 0.08-12.5). Median CSF timing from the onset of seizures was longer in chronic epilepsy (540 days), whereas FIRES, FSE, and ASE had CSF tested within 1-2 days of onset of seizures (P < .001). The elevation of cytokines/chemokines was higher in FIRES followed by FSE, when compared to chronic epilepsy and NIND controls. Th1-associated cytokines/chemokines (TNF-α, CXCL9, CXCL10, CXCL11), IL-6, CCL2, CCL19, and CXCL1 (P < .05) were elevated in FIRES, in contrast to the elevation of a broader network of cytokines/chemokines in encephalitis. The cytokines/chemokines (CXCL9, CXCL10, CXCL11, and CCL19) were elevated in FSE when compared to ASE despite the similar median seizure duration and timing of CSF testing in relation to seizures. Chronic epilepsy generally lacked significant elevation of cytokines/chemokines despite frequent daily seizures. The median concentrations of the cytokines/chemokines rapidly declined on serial testing during the course of illness in all three FIRES/FRD cases.

Significance: We identify significant differences in CSF cytokine/chemokine profile between FIRES/FRD and encephalitis. The prominent elevation of CSF cytokines and chemokines in FIRES/FRD and to a lesser extent FSE highlights that the cytokine/chemokine elevation is significantly associated with the etiology of the underlying process rather than purely reactive. However, it is unclear whether the immune activation contributes to the disease process.