Can childhood absence seizures present exclusively at night in a 2½‑year‑old girl?

Childhood Absence Seizures Do Not Occur Exclusively at Night

Childhood absence seizures (CAE) do not present only at night—in fact, typical absence seizures occur multiple times per day (often dozens to hundreds) when untreated, and exclusively nocturnal presentation should prompt reconsideration of the diagnosis. 1

Why This Matters for Your 2½-Year-Old Patient

Age and Diagnosis Concerns

• The age of 2½ years is atypical for childhood absence epilepsy, which characteristically begins around 6 years of age (mean age at onset) 1, 2
• CAE is most common in school-aged children, with peak onset between 4-8 years 3
• This young age alone should raise suspicion for an alternative diagnosis 1

Characteristic Seizure Patterns in CAE

• Absence seizures in CAE occur during wakefulness, not sleep, with multiple daily episodes (often 10-200+ per day) when untreated 1, 3
• The seizures are brief (typically lasting seconds), with sudden onset and termination 4, 5
• They are easily precipitated by hyperventilation in approximately 90% of untreated patients 4, 5

The Critical Exception: Absence Seizures During Sleep

• While extremely rare, absence seizures can occur during sleep in CAE, but this is considered a sign of drug resistance and poor prognosis 6
• One case report documented a child with refractory CAE who developed absence seizures during sleep at age 8, remaining resistant to multiple medications including valproic acid, lamotrigine, levetiracetam, and perampanel 6
• Absence seizures during sleep should be suspected when 3 Hz generalized spike-wave discharges last >2 seconds on EEG during sleep 6
• This presentation is so atypical that it suggests either drug-resistant epilepsy or an incorrect diagnosis 6

Alternative Diagnoses to Consider

Focal Seizures with Impaired Awareness

• Focal seizures can mimic absence seizures but may occur during sleep and have different characteristics 1, 7
• Focal seizures may have auras (which would exclude generalized absence seizures), focal EEG patterns, and can show focal features on examination 1, 7
• The presence of any focal feature is independently associated with clinically relevant abnormalities on neuroimaging 7

Other Seizure Types in Young Children

• At 2½ years, consider other seizure types more common in this age group, including focal seizures or other generalized epilepsy syndromes 8
• Neonatal and infantile seizures often have different underlying etiologies than older children 7

Diagnostic Approach

Essential Clinical Features to Assess

• Document whether there is true loss of awareness during the episodes (staring without documented loss of awareness should not be used to diagnose absence seizures) 1, 7
• Look for the presence of aura, which would suggest focal rather than generalized seizures 1, 7
• Assess for any focal neurologic features during or after the episodes 7
• Determine the frequency of episodes (infrequent or sporadic seizures should prompt reconsideration of CAE diagnosis) 1

EEG Findings

• True absence seizures show characteristic 3 Hz generalized spike-wave discharges on EEG 3, 4, 5
• Generalized seizures rapidly affect both hemispheres from onset without warning 7
• Focal EEG patterns would suggest focal seizures rather than absence seizures 1

Neuroimaging Considerations

• Although MRI is rarely required in neurologically normal children with typical generalized seizures (abnormalities found in ≈2% of cases), neuroimaging should be considered in younger children or atypical presentations to exclude structural etiologies 1
• This is particularly important given the atypical age and nocturnal presentation in your patient 1

Clinical Bottom Line

For a 2½-year-old with exclusively nocturnal seizure-like episodes, childhood absence epilepsy is highly unlikely. The combination of young age (below typical CAE onset) and nocturnal-only presentation strongly suggests either:

1. An alternative seizure type (most likely focal seizures with impaired awareness) 1, 7
2. Non-epileptic events that mimic seizures 1
3. If truly absence seizures occurring during sleep, this would represent an exceptionally rare and ominous presentation suggesting drug resistance 6

Proceed with comprehensive EEG evaluation (including sleep recording if possible) and consider neuroimaging given the atypical presentation 1, 7. The diagnosis should be confirmed with documented loss of awareness and characteristic EEG findings before labeling as CAE 1, 7.