What are the recommended initial laboratory tests and treatments for pediatric patients presenting with seizures?

Pediatric Seizure Laboratory Evaluation

Laboratory testing in pediatric seizures should be guided by clinical presentation rather than performed routinely, with serum glucose being the single most important test to obtain in all cases. 1

Essential Laboratory Tests

Universally Recommended

• Serum glucose should be checked in all pediatric patients presenting with seizures, as hypoglycemia is the most clinically significant and immediately treatable metabolic cause 1, 2
• Serum sodium should be obtained in all cases, as hyponatremia is the second most common metabolic abnormality requiring immediate intervention 1, 2

Selective Testing Based on Clinical Context

• Toxicology screening should be considered across the entire pediatric age range if there is any question of drug exposure or substance abuse 1, 2
• Calcium and magnesium levels should be checked when clinical findings suggest these abnormalities (vomiting, diarrhea, dehydration, failure to return to baseline alertness) 1, 2
• Complete blood count and comprehensive metabolic panel should be ordered only when suggested by specific clinical findings, not routinely 2
• Antiepileptic drug (AED) levels should be obtained in children with known epilepsy already taking AEDs, as levels are low in 32% of these patients presenting with status epilepticus 3

Evidence Against Routine Laboratory Testing

Multiple high-quality studies demonstrate the limited yield of routine laboratory testing in pediatric seizures:

• Abnormal serum electrolytes, calcium, magnesium, and glucose rarely cause seizures in children, and routine use of these tests is costly without contributing to seizure therapy 4
• In status epilepticus, laboratory abnormalities (sodium, electrolytes, calcium, glucose) occur in only approximately 6% of cases 3
• Severe electrolyte imbalance or hypoglycemia causing seizures was noted in only 3 of 319 children (0.9%) presenting with first seizures 5
• Routine diagnostic tests in 100 children with simple febrile seizures proved to be of little diagnostic value despite significant expense 6

Lumbar Puncture Indications

Lumbar puncture is of limited value in pediatric non-febrile seizures and should be used primarily when there is concern about possible meningitis or encephalitis. 1, 2

Specific Indications for LP:

• Fever with meningeal signs (neck stiffness, bulging fontanel) 2, 7
• Immunocompromised status 2
• Persistent altered mental status lasting longer than 1 hour after seizure 7
• Septic appearance, behavior disorders, hypotonia, or petechial purpura 7
• Complex febrile seizures (prolonged, focal, and/or repeated) with other suggestive clinical signs 7

Evidence Against Routine LP:

• The risk of bacterial meningitis or encephalitis after a simple febrile seizure with normal clinical examination is extremely low, even in children younger than 18 months 7
• In children with first simple febrile seizures, systematic lumbar puncture is not necessary even under 18 months of age 7
• When LP was performed in status epilepticus cases, CNS infection was found in at least 12.8% of cases, but this was in selected patients with clinical suspicion 3

Additional Diagnostic Studies

Electroencephalography (EEG)

• EEG is recommended as part of the neurodiagnostic evaluation of the child with an apparent first unprovoked seizure 1, 2
• EEG may be helpful in determining focal versus generalized epileptiform abnormalities (found in 43% of children with status epilepticus) to guide further testing 3

Neuroimaging

• MRI is the preferred imaging modality when neuroimaging is obtained 1, 2
• Emergent neuroimaging should be performed in children who exhibit a postictal focal deficit that does not quickly resolve or who have not returned to baseline within several hours after the seizure 1, 2
• Neuroimaging may be considered after stabilization if there are clinical indications or if the etiology is unknown 3
• Abnormalities on neuroimaging explaining the etiology were found in at least 8% of children with status epilepticus 3

Critical Clinical Pitfalls

Age-Specific Considerations

• Do not perform routine laboratory testing in simple febrile seizures (children 6 months to 5 years with fever and brief generalized seizure) 6, 5
• The presence of fever does not automatically warrant extensive laboratory evaluation unless other clinical signs suggest serious infection 5, 7

Clinical Decision-Making

• History and physical examination should guide laboratory testing, not protocols mandating routine comprehensive panels 6, 4, 5
• Abnormal brain imaging was noted in 26% of children with first seizures, but 75% of these had abnormal histories, physical examinations, or neurologic examinations 5
• Only 3 cases of metabolic abnormality were not predicted by history and physical examination in one large retrospective study 1

Metabolic Testing Considerations

• Studies for inborn errors of metabolism should be considered only when there are clinical indicators for concern or when the initial evaluation reveals no etiology (found abnormalities in 4.2% when performed) 3
• Evidence of ingestion was found in 3.6% of children with status epilepticus when toxicology was performed 3

Practical Algorithm

For a child presenting with first-time seizure:

1. Immediately check: Serum glucose and sodium 1, 2
2. Assess clinical status: Has the child returned to baseline neurologic function? 2
3. If NOT returned to baseline or has focal deficits: Consider emergent neuroimaging and broader laboratory evaluation 1
4. If returned to baseline with normal exam: Additional laboratory testing is generally not indicated 4, 5
5. Consider LP only if: Fever with meningeal signs, immunocompromised, or persistent altered mental status 2, 7
6. Obtain AED levels in children with known epilepsy on medications 3
7. Consider toxicology if any suspicion of exposure or substance abuse 1, 2