Can Seizures Cause Fever?
No, seizures do not cause fever—fever causes seizures in susceptible children, not the reverse. The relationship is unidirectional: fever triggers seizures in predisposed individuals, particularly children aged 6 months to 5 years, through temperature-induced neuronal hyperexcitability 1, 2.
The Directional Relationship
Fever is the precipitating factor, not the consequence. Febrile seizures result from age-dependent hyperexcitability of the brain that is induced by fever, meaning it is the fever itself that causes the seizure in genetically susceptible children 2. The pathophysiology involves fever-induced inflammatory cytokines (IL-1β, IL-6, TNF-α) that cross the blood-brain barrier, increase excitatory glutamatergic neurotransmission, and decrease inhibitory GABAergic transmission, thereby lowering the seizure threshold 3.
Clinical Context: When Fever and Seizures Coexist
When evaluating a child with both fever and seizures, the critical distinction is whether this represents:
- Febrile seizures: Seizures accompanied by fever (≥100.4°F/38°C) without central nervous system infection, occurring in children 6 months to 5 years old 1, 4
- Seizures from intracranial infection: Where fever is a symptom of meningitis or encephalitis, and seizures result from the infection itself, not merely the fever 1, 2
The primary diagnostic imperative is excluding meningitis, as seizures are the presenting sign in one in six children with meningitis, and one-third of these patients may lack meningeal signs 2. Documented fever ≥38°C within 72 hours of presentation is considered a minor criterion for encephalitis diagnosis, but requires additional major criteria (altered mental status ≥24 hours) to establish the diagnosis 1.
Common Pitfall: Post-Ictal Temperature Elevation
A critical caveat: brief, transient temperature elevations can occur in the immediate post-ictal period following prolonged seizures due to increased metabolic activity and muscle contractions. However, this is distinct from true fever and typically resolves quickly. The 24-hour altered mentation requirement in encephalitis criteria specifically excludes the post-ictal state seen after febrile seizures 1.
Clinical Algorithm for Fever-Seizure Evaluation
When a child presents with fever and seizures:
- Determine timing: Was fever present before the seizure? 2, 4
- Assess age: Is the child 6 months to 5 years old? 1
- Classify seizure type: Simple (<15 minutes, generalized, single episode) vs. complex (≥15 minutes, focal, or recurrent within 24 hours)? 1
- Exclude CNS infection: Perform lumbar puncture if meningeal signs, septic appearance, behavioral disturbance, or any clinical uncertainty exists 2, 5
- Identify fever source: The primary goal is finding and treating the underlying infection causing the fever 2
In traumatic brain injury contexts, fever control is recommended in patients with severe TBI who have seizures or are at high risk of seizures, as uncontrolled fever can precipitate secondary brain injury 1. This represents a different clinical scenario where fever management is part of neuroprotection, not a consequence of the seizure itself.