What is the recommended work‑up and initial management for a 12‑month‑old infant who presents with a first seizure?

Management of First Seizure in a 12-Month-Old Infant

For a 12-month-old presenting with a first seizure, the critical initial step is determining whether the seizure is febrile or non-febrile, as this fundamentally changes the workup and management approach.

Initial Assessment Framework

Key Clinical Distinctions

The 12-month age is particularly significant because:

• Febrile seizures typically occur between 6 months and 5 years of age and require fever (≥100.4°F/38°C) without evidence of intracranial infection 1
• Children younger than 12 months at their first febrile seizure have approximately 50% probability of recurrence (versus 30% for those >12 months) 2
• Age ≤18 months is a predictor of clinically urgent intracranial pathology in non-febrile focal seizures 3

If FEBRILE Seizure (Simple)

No neuroimaging is indicated for simple febrile seizures 1. The workup should focus on:

Defining Simple vs. Complex:

• Simple: Generalized, <15 minutes, no recurrence within 24 hours
• Complex: >15 minutes, recurs >once in 24 hours, or focal features 1

Management for Simple Febrile Seizure:

• No routine imaging (MRI, CT, or ultrasound) 1
• No routine laboratory tests unless clinically indicated for fever source
• Assess for meningitis/encephalitis - perform lumbar puncture if clinical signs suggest intracranial infection 4
• Admission recommended for children under 18 months 4
• Parental education about benign prognosis: no IQ decline, no increased mortality, only 1% epilepsy risk (same as general population) 2

Critical caveat: Even though MRI abnormalities are found in 11.4% of simple febrile seizures, these findings do not alter clinical management 1.

If NON-FEBRILE Seizure

All children under 1 year with afebrile seizures should be admitted 4. The workup is more extensive:

Essential Immediate Workup:

• Blood pressure measurement (mandatory for all) 4
• Blood glucose if child is seizing or somnolent 4
• Consider metabolic panel including calcium, phosphate, magnesium, sodium - particularly important as metabolic disorders can present at this age 5

Neuroimaging Considerations:

• Emergent imaging indicated if:

  • Focal seizure manifestations (4.1% have clinically urgent pathology) 3
  • Persistent Todd's paresis 3
  • Abnormal neurological examination
  • Concern for trauma, hemorrhage, or structural abnormality

• MRI preferred over CT when feasible for non-emergent evaluation, as it better identifies structural abnormalities and has no radiation exposure 1

EEG Timing:

• Should be performed in non-febrile seizures to help distinguish epileptic from non-epileptic events and guide treatment decisions 6, 7
• In epileptic seizures, EEG shows abnormalities in approximately 70% of cases 6

Risk Stratification for 12-Month-Olds

Higher risk features requiring more aggressive workup:

• Age <12 months (at higher risk for recurrence and underlying pathology) 2, 3
• Focal seizure features (eye deviation, focal hypertonia, postictal confusion) 6
• Abnormal neurological examination
• Family history of epilepsy (increases epilepsy risk to 2.4% by age 25) 2

Common Pitfalls to Avoid

1. Don't assume all seizures with fever are benign febrile seizures - rule out meningitis/encephalitis, especially if child received antibiotics prior to presentation 4

2. Don't over-image simple febrile seizures - resist pressure for "reassurance imaging" as it doesn't change management 1

3. Don't miss metabolic causes - hypocalcemia and other metabolic disorders can present at this age with first seizure 5

4. Don't discharge young infants (<18 months) with first afebrile seizure without appropriate evaluation and observation 4

5. Don't order routine laboratory tests in simple febrile seizures - they have extremely low yield (4% abnormality rate) and don't change management 6