What is the management and treatment approach for a 5-week-old infant presenting with a seizure?

Management of Seizure in a 5-Week-Old Infant

A 5-week-old infant presenting with seizure requires immediate emergency medical system activation, urgent assessment for life-threatening causes, and phenobarbital as first-line treatment if seizures persist beyond 5 minutes or recur. 1, 2, 3

Immediate Emergency Response

Activate emergency medical services immediately - any seizure in an infant under 6 months of age is an automatic indication for EMS activation and hospital evaluation. 1, 2

Acute Stabilization During Seizure

• Position the infant on their side to reduce aspiration risk and maintain airway patency. 1, 2
• Do not restrain the infant or place anything in the mouth - these actions cause harm without benefit. 1, 2
• Ensure adequate oxygenation by positioning in "sniffing" position and providing high-flow oxygen if available. 2
• Protect from injury during seizure movements but allow the seizure to occur without interference. 1
• Do not give oral medications, food, or liquids during the seizure or immediately after when responsiveness is decreased. 1

When to Administer Emergency Medication

• If the seizure lasts longer than 5 minutes, benzodiazepines are indicated (lorazepam 0.1 mg/kg IV/IO). 2, 3
• Most neonatal seizures are self-limited and resolve within 1-2 minutes, but seizures exceeding 5 minutes require anticonvulsant intervention. 1, 2

Hospital-Based Diagnostic Workup

Immediate Laboratory Assessment

• Check blood glucose urgently - hypoglycemia is a rapidly reversible cause of neonatal seizures and must be identified immediately. 2, 3
• Obtain electrolytes including calcium, magnesium, and sodium - metabolic derangements are common treatable causes. 2
• Complete blood count and blood culture if infection is suspected. 2
• Consider arterial blood gas to assess for metabolic acidosis or hypoxia. 2

Neuroimaging Considerations

• MRI is the preferred imaging modality for neonatal seizures when the infant is stable enough for transport, as it provides superior sensitivity for detecting structural abnormalities, hypoxic-ischemic injury, and intracranial hemorrhage. 1
• CT may be performed initially if hemorrhage or trauma is suspected and the infant is too unstable for MRI, but has lower sensitivity for most neonatal seizure etiologies. 1
• Cranial ultrasound has limited utility - MRI shows findings in 11.9% of patients not apparent on ultrasound and contributes additional diagnostic information in 39.8% of cases. 1

Electroencephalography

• Continuous EEG monitoring is strongly recommended because the majority of neonatal seizures are subclinical (electrographic-only without visible clinical signs). 3, 4, 5
• Many abnormal movements clinically identified as seizures lack EEG correlation, while true seizures may have no visible manifestations. 6, 4

Anticonvulsant Treatment Protocol

First-Line Treatment

Phenobarbital remains the first-line anticonvulsant for neonatal seizures regardless of etiology (unless channelopathy is suspected based on family history, in which case phenytoin or carbamazepine should be used). 2, 3, 5

• Loading dose: 15-20 mg/kg IV, achieving therapeutic levels within minutes. 2, 6
• Up to 77% of neonatal seizures respond to phenobarbital at doses achieving serum concentrations up to 40 mcg/mL. 2
• Premature infants (<32 weeks) respond significantly better to phenobarbital than term infants. 2

Second-Line Treatment Options

If seizures persist after phenobarbital, the following may be used as second-line agents: 3

• Levetiracetam 40 mg/kg IV bolus (preferred in neonates with cardiac disorders, given over 5-10 minutes). 2, 3
• Phenytoin (avoid in cardiac disorders due to arrhythmia risk). 3
• Midazolam for ongoing seizures. 3
• Lidocaine for refractory cases (effective as second or third-line treatment). 6, 3

Maintenance Therapy After Seizure Control

• Lorazepam 0.05 mg/kg IV every 8 hours for 3 doses (maximum 1 mg). 2
• Levetiracetam 15 mg/kg IV every 12 hours (maximum 1,500 mg). 2
• Phenobarbital 1-3 mg/kg IV every 12 hours if used for loading. 2

Critical Etiologic Considerations in a 5-Week-Old

High-Priority Diagnoses to Evaluate

• Hypoxic-ischemic encephalopathy - most common cause of neonatal seizures, though less likely at 5 weeks unless there was a recent hypoxic event. 5
• Intracranial hemorrhage - particularly if history of birth trauma, low hematocrit, or coagulopathy. 1, 2
• Infection (meningitis/encephalitis) - perform lumbar puncture unless contraindicated by signs of raised intracranial pressure or coma. 2
• Metabolic disorders - inborn errors of metabolism may present in the first weeks of life. 2, 4
• Genetic epilepsy syndromes - neonatal-onset epilepsies require specific evaluation. 4
• Vitamin B6-dependent epilepsy - consider pyridoxine trial if seizures are unresponsive to second-line medications. 3

Lumbar Puncture Indications

• Perform LP if meningitis/encephalitis is suspected based on clinical presentation (fever, lethargy, poor feeding). 2
• Contraindications include coma or signs of raised intracranial pressure (unilateral sluggish or absent pupillary responses are the most reliable sign) - perform brain imaging first in these cases. 2

Medication Discontinuation

Following cessation of acute provoked seizures without evidence of neonatal-onset epilepsy, discontinue anticonvulsants before discharge home, regardless of MRI or EEG findings. 7, 3

• This applies to acute symptomatic seizures (provoked by identifiable acute cause). 3
• Long-term follow-up is necessary to screen for postneonatal epilepsy development. 5

Common Pitfalls to Avoid

• Do not assume all abnormal movements are seizures - many neonatal behaviors mimic seizures but lack EEG correlation. 6, 4
• Do not miss subclinical seizures - continuous EEG monitoring is essential as most neonatal seizures have no visible clinical signs. 3, 4, 5
• Do not use antipyretics for seizure prevention - acetaminophen and ibuprofen do not prevent seizures, though they may be used for comfort if fever is present. 1, 7
• Monitor for respiratory depression when using benzodiazepines and phenobarbital. 2
• Treating seizures (including electrographic-only seizures) to achieve lower seizure burden may improve neurodevelopmental outcomes - do not ignore subclinical seizures. 3