febrile seizure

**Definition:** Seizure in a child 6 months–5 years (peak 12–18 months) associated with fever ≥38°C, without intracranial infection (meningitis/encephalitis), metabolic derangement, or history of afebrile seizures. Often occurs early in a viral illness, as temperature rises rapidly (may be the first sign of fever).

**Classification:** - **Simple (~70-75%):** Generalized (tonic-clonic), lasts <15 minutes, occurs once in 24 hours, no focal features, return to baseline quickly. - **Complex (~25-30%):** Focal features, OR lasts ≥15 minutes, OR recurs within 24 hours (or within the same febrile illness). Higher risk of later epilepsy. - **Febrile status epilepticus:** ≥30 minutes (some use ≥5 minutes operationally for treatment).

**Pathophysiology/Associations:** - Age-dependent susceptibility of the immature brain to fever; likely cytokine-mediated (IL-1β) increased neuronal excitability, plus hyperthermia-induced hyperventilation/alkalosis. - Strong genetic component: family history in first-degree relative is a major risk factor. Associated with GEFS+ (SCN1A, SCN1B, GABRG2 mutations); Dravet syndrome (SCN1A) may initially present with prolonged febrile seizures. - Common triggers: viral infections (HHV-6/roseola, influenza, adenovirus), otitis media, and post-vaccination fever (e.g., MMR, DTP).

**Risk factors for recurrence (~30% overall; ~50% if first seizure <12 months):** Young age at onset (<12 months), family history of febrile seizures, low-grade fever at time of seizure, short duration of fever before seizure, and multiple prior episodes.

**Risk factors for later epilepsy (baseline ~1% in general population; ~2% after simple febrile seizure; higher with complex):** Complex febrile seizure, pre-existing neurodevelopmental abnormality, family history of epilepsy, and short duration of fever (<1 hour) before seizure.

**Workup:** - Primarily clinical; find the source of the fever. - **Lumbar puncture:** Strongly consider if meningeal signs, ill appearance, or age <12 months with incomplete Hib/pneumococcal immunization status; consider in children already on antibiotics (can mask meningitis). - EEG, neuroimaging, and routine labs are NOT indicated for simple febrile seizures in a neurologically healthy child. - Neuroimaging/EEG considered in complex cases with neurologic deficits.

**Management:** - Acute: ABCs, position safely; most stop spontaneously. If seizure >5 minutes: benzodiazepines (IV lorazepam, rectal diazepam, intranasal/buccal midazolam). - Antipyretics (acetaminophen/ibuprofen) improve comfort but do NOT prevent recurrence. - Prophylactic anticonvulsants are generally not recommended (risks outweigh benefits). Intermittent oral diazepam during febrile illness is an option in select high-risk recurrent cases. - Parental reassurance and education (first-aid for seizures, when to call EMS).

**Prognosis:** Excellent. No evidence of permanent neurologic damage, cognitive deficits, or increased mortality after simple febrile seizures.

**High-yield pearls:** - Febrile seizure ≠ epilepsy. - Most common cause of seizure in children <5 years. - Distinguish from meningitis, which is the key "can't miss" diagnosis. - Mesial temporal sclerosis is associated with prolonged febrile seizures in the history of some temporal lobe epilepsy patients.