How do you diagnose and manage absence seizures?

Monitoring for Absence Seizures

The definitive diagnostic tool for monitoring absence seizures is electroencephalography (EEG), ideally with video recording, which should be performed in all suspected cases to confirm diagnosis and guide treatment decisions. 1

Clinical Presentation and Recognition

Absence seizures present with distinct characteristics that differentiate them from other seizure types:

• Key clinical features:

  • Brief episodes (seconds) of sudden onset and termination
  • Impairment of consciousness ranging from severe to mild
  • Staring spells with cessation of activity
  • Possible mild motor manifestations (eyelid fluttering, facial myoclonia)
  • Automatisms may occur
  • Rapid return to baseline after seizure ends
  • No post-ictal confusion

• Diagnostic triggers:

  • Hyperventilation can precipitate absence seizures in approximately 90% of untreated patients 2
  • Photic stimulation may trigger seizures in some patients
  • Emotional factors or mental stress can be triggers

Diagnostic Approach

EEG Monitoring

• Standard EEG findings: Generalized 3-4 Hz spike/polyspike and slow wave discharges 2
• Video-EEG monitoring: Essential for proper classification and differential diagnosis 3
  • Can record ictal events
  • Helps distinguish between different absence epilepsy syndromes
  • Allows correlation between clinical manifestations and EEG changes

Activation Procedures During EEG

• Hyperventilation: Most effective activation technique (3-5 minutes)
• Photic stimulation: May trigger seizures in photosensitive patients
• Sleep deprivation: May increase likelihood of capturing events

Laboratory Testing

For patients presenting with suspected absence seizures, essential laboratory tests include:

• Serum glucose
• Serum sodium
• Complete metabolic panel if altered mental status is present
• Antiepileptic drug levels in patients on seizure medications 1

Neuroimaging

• MRI is preferred when neuroimaging is indicated, though not routinely necessary for typical absence seizures with classic EEG findings 1
• CT may be performed initially in emergency settings if there are concerning features

Classification of Absence Seizures

Proper classification is important for treatment decisions and prognosis:

• Typical absence seizures:

  • Childhood absence epilepsy (CAE)
  • Juvenile absence epilepsy (JAE)
  • Juvenile myoclonic epilepsy with absence component

• Atypical absence seizures:

  • Often associated with developmental and epileptic encephalopathies
  • Usually more intractable than typical absences 4

• Special syndromes with absence features:

  • Eyelid myoclonia with absences
  • Perioral myoclonia with absences 3

Treatment Considerations

Treatment selection depends on accurate classification:

• First-line medications:

  • Ethosuximide: Drug of choice for pure absence seizures (70% effective) 2, 5
  • Valproic acid: Effective for absences (75%) and also controls other generalized seizures 6, 2
  • Lamotrigine: Alternative option, particularly effective when combined with valproic acid 2

• Treatment algorithm:

  1. Start with ethosuximide for pure absence seizures
  2. Use valproic acid if other seizure types coexist
  3. Consider lamotrigine as alternative or add-on therapy
  4. For refractory cases, combination therapy may be needed

Monitoring Treatment Response

• Follow-up EEG: Essential to confirm seizure control
• Seizure diary: Patients should maintain detailed records of suspected events
• Consider sleep-deprived or early morning EEG to capture abnormal activity during vulnerable periods 1

Common Pitfalls in Diagnosis

• Misdiagnosis as daydreaming or inattention: Absence seizures may be subtle and mistaken for behavioral issues
• Failure to perform adequate EEG with activation procedures: May miss diagnosis
• Overlooking comorbid seizure types: Absence seizures often coexist with other generalized seizures
• Not considering atypical absences: These require different treatment approaches and have different prognosis 4

When to Consider Emergency Intervention

Emergency intervention is rarely needed for typical absence seizures but may be required for:

• Absence status epilepticus (prolonged absence seizures)
• Seizures with traumatic injuries
• Seizures with breathing difficulties 1

Proper diagnosis and classification of absence seizures through video-EEG monitoring is crucial for effective treatment planning and management of this distinct seizure type.