What are the symptoms of absence seizures?

Absence Seizure Symptoms

Absence seizures are characterized by brief episodes of impaired consciousness lasting seconds, typically with a blank stare, cessation of activity, and sometimes subtle motor manifestations such as eye blinking or mild facial twitching. 1

Clinical Presentation

Primary Symptoms

• Sudden onset and termination of consciousness impairment (lasting 2-30 seconds)
• Blank stare or "absence" appearance
• Cessation of ongoing activities
• Unresponsiveness during the episode
• Immediate return to normal awareness after the episode without confusion

Associated Features

• Mild motor manifestations:
  • Myoclonic movements, mainly of facial muscles 1
  • Eye blinking
  • Automatisms (such as lip smacking or chewing movements)
  • Mild clonic, tonic, or atonic components 1
• Autonomic disturbances may occur

Severity Spectrum

• Impairment of consciousness varies from severe to mild or even inconspicuous 1
• Episodes may be brief (2-5 seconds) or longer (15-30 seconds) 1
• Frequency can range from several per day to occasional episodes

Distinguishing Features from Other Seizure Types

Absence seizures differ fundamentally from other seizure types:

• Unlike tonic-clonic seizures, there is no falling, jerking of limbs, or postictal confusion 2
• Unlike focal seizures, consciousness is altered rather than lost, and typically doesn't lead to falls 2
• Unlike syncope, there is no lightheadedness before the event or pallor 2
• Unlike complex partial seizures, the onset and termination are abrupt 1

Diagnostic Considerations

EEG Findings

• Characteristic generalized 3-4 Hz spike/polyspike and slow wave discharges on EEG 1
• The EEG discharge may be:
  • Brief (2-5 seconds) or long (15-30 seconds)
  • Continuous or fragmented
  • With single or multiple spikes associated with slow waves 1

Triggering Factors

• Hyperventilation precipitates absence seizures in about 90% of untreated patients 1
• Can be triggered by:
  • Photic stimulation
  • Pattern or video game stimuli
  • Mental or emotional factors 1

Clinical Pearls

• Absence seizures typically begin in childhood or adolescence but can occur in adults 3
• They are pharmacologically unique and respond to specific medications (ethosuximide, valproic acid, lamotrigine) 1
• Absence seizures may be the only seizure type or may occur alongside other generalized seizures 1
• Absence status epilepticus (prolonged episodes) occurs in about 30% of patients 1

Management Considerations

• First-line medications include ethosuximide (which suppresses the 3 Hz spike and wave activity) 4, valproic acid, and lamotrigine 1
• Ethosuximide controls about 70% of absence seizures but is unsuitable if other seizure types coexist 1
• Valproic acid controls absences in 75% of patients and also helps with other generalized seizures 1

When to Seek Emergency Care

Emergency medical services should be activated for 2:

• First-time seizures
• Seizures lasting more than 5 minutes
• Multiple seizures without return to baseline between episodes
• Seizures with associated traumatic injuries or breathing difficulties