Evaluation and Management of Pediatric Absence Seizures
EEG is the cornerstone diagnostic test for suspected absence seizures in children, and ethosuximide is the first-line treatment when absence seizures occur in isolation.
Diagnostic Evaluation
Essential Diagnostic Testing
EEG is mandatory as part of the neurodiagnostic evaluation of any child with an apparent first unprovoked seizure, including suspected absence seizures 1.
Hyperventilation during the office visit can provoke absence seizures and aid in diagnosis, as the characteristic 3-Hz spike-and-wave pattern on EEG confirms the diagnosis 2.
Laboratory testing should be selective, not routine—order tests only when clinical circumstances suggest metabolic derangements such as vomiting, diarrhea, dehydration, or failure to return to baseline alertness 1, 3.
Toxicologic screening should be considered if there is any question of drug exposure or substance abuse across the entire pediatric age range 1.
Neuroimaging Considerations
MRI is the preferred imaging modality if neuroimaging is obtained 1, 3.
Emergent neuroimaging is NOT typically indicated for uncomplicated absence seizures where the child has returned to baseline mental status 3.
Non-urgent MRI should be considered in children with significant cognitive or motor impairment of unknown etiology, unexplained abnormalities on neurologic examination, or in children aged <1 year 1, 3.
Absence seizures typically do not require imaging unless there are focal neurologic findings or the EEG pattern is atypical 2.
Lumbar Puncture
- LP is of limited value in first non-febrile seizures and should be reserved primarily for concern about possible meningitis or encephalitis 1, 3.
Medical Management
First-Line Treatment
Ethosuximide is the treatment of choice for childhood absence epilepsy when absence seizures occur in isolation 2.
Initial dosing for ethosuximide: Start at 250 mg/day for children 3-6 years of age, or 500 mg/day for children ≥6 years of age 4.
Dose titration: Increase by 250 mg every 4-7 days until control is achieved with minimal side effects 4.
Optimal dose: 20 mg/kg/day for most pediatric patients, targeting plasma levels of 40-100 mcg/mL 4.
Maximum dose: Dosages exceeding 1.5 g daily should be administered only under strict physician supervision 4.
Alternative Treatment Options
Valproic acid is effective but has more adverse effects compared to ethosuximide 2.
Valproic acid dosing: Initiate at 10-15 mg/kg/day and increase by 5-10 mg/kg/week to achieve optimal clinical response 5.
Target dose for valproic acid: Ordinarily below 60 mg/kg/day, with therapeutic plasma levels of 50-100 mcg/mL 5.
Lamotrigine is less effective than ethosuximide for absence seizures 2.
Important Treatment Considerations
Combination therapy may be necessary when other seizure types coexist with absence seizures 4.
Monitor for thrombocytopenia with valproic acid—risk increases significantly at trough levels above 110 mcg/mL in females and 135 mcg/mL in males 5.
Refractory absence epilepsy occurs in fewer than half of patients, though efficacy data for alternative treatments are lacking 2.
Disposition and Follow-Up
Outpatient management is appropriate if the child has returned to baseline, has a normal neurologic examination, and no concerning features on history 3.
Arrange outpatient EEG if not performed in the emergency department 3.
Assess for psychosocial comorbidities, as careful evaluation and treatment of these is essential in caring for patients with childhood absence epilepsy 2.
Common Pitfalls to Avoid
Do not routinely order extensive laboratory panels (calcium, magnesium, phosphate) in otherwise healthy children who have returned to baseline—these are very low yield 1.
Do not confuse absence seizures with other staring spells—the EEG with 3-Hz spike-and-wave pattern is pathognomonic 2.
Do not delay EEG—it is the single most important diagnostic test and should be obtained promptly 1, 3.
Do not start valproic acid as first-line when absence seizures occur in isolation, as ethosuximide has a better side effect profile 2.