Clinical framing

Differential diagnosis

• Simple febrile seizure - possible but atypical given age; some children have their "tail end" simple febrile seizures up to 6 years.
• Complex febrile seizure - if focal features, prolonged (>15 min), or recurs within 24 h.
• Febrile status epilepticus - if it had continued beyond ~20-30 minutes; carries a higher risk of underlying CNS infection and warrants LP (Rosen's Emergency Medicine, p. 3205-08).
• Febrile seizures plus (FS+) / GEFS+ spectrum - a genetic epilepsy syndrome defined by febrile (and often afebrile) generalized tonic-clonic seizures that persist beyond age 6, which fits this age group well and should be actively considered.

• Bacterial meningitis - look for meningeal signs, incomplete immunization, bulging fontanelle equivalent findings, irritability, altered sensorium (Harriet Lane, p. 741; Tintinalli's, p. 3168-73).
• Viral meningoencephalitis, especially HSV encephalitis - consider if focal seizure, prolonged post-ictal confusion, or behavioral change.
• Brain abscess.

• Hypoglycemia, hyponatremia/hypernatremia, hypocalcemia, hypomagnesemia - all can present with fever-associated seizures and are checked immediately in the ED (Tintinalli's, p. 2608-16).

• Anticholinergic or sympathomimetic toxicity, serotonin syndrome, neuroleptic malignant syndrome, isoniazid toxicity - fever here is a consequence of the toxidrome rather than a true infectious trigger (Rosen's Emergency Medicine, p. 1188).

• A pre-existing generalized epilepsy syndrome (e.g., genetic generalized epilepsy, Dravet syndrome if seizure burden and history fit, Lennox-Gastaut) can have its first or a breakthrough seizure precipitated by fever.

• Anti-NMDA-receptor encephalitis and related autoimmune encephalitides can present with fever, seizures, and behavioral/psychiatric change in school-age children.

• Previously healthy school-age child develops a febrile illness followed by refractory status epilepticus - an important, though rare, diagnosis in this exact age bracket.

• A prolonged unilateral (focal) febrile seizure leading to post-ictal hemiplegia and subsequent epilepsy.

• Tumor, vascular malformation, prior injury with gliotic focus - fever can be the "unmasking" trigger for a seizure from a pre-existing focal lesion.

• Heat stroke, malignant hyperthermia (rare), or cerebral malaria if there is relevant travel/exposure history.

• Vasovagal or cardiogenic syncope with convulsive movements, psychogenic non-epileptic seizures (increasingly seen in school-age children), paroxysmal dyskinesia (Harriet Lane, Table 20.3, p. 741).

Key red flags that push away from "simple febrile seizure" and warrant further workup (LP ± neuroimaging ± EEG, blood glucose/electrolytes/calcium, CBC, blood culture)

• Age outside 6 months-5/6 years (present here)
• Focal seizure activity or focal findings post-ictally
• Duration approaching or exceeding 15 minutes, or recurrence within 24 h
• Meningeal signs, bulging fontanelle-equivalent irritability, persistent altered sensorium beyond expected post-ictal period
• Incomplete immunization or prior antibiotic pretreatment (masks meningitis signs)
• Recent antibiotic exposure, toxic ingestion history, travel history

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