Seizure Disorder, Absence



  • A type of generalized nonmotor seizure characterized by a brief lapse of awareness
  • Classified by the International League Against Epilepsy (ILAE) (1):
    • Typical have an abrupt onset and offset of behavioral arrest, loss of awareness, and blank staring, sometimes with eyelid movements, eye opening, or oral automatisms (e.g., lip smacking).
      • Typically occurs at 3 Hz
      • Lasts 5 to 30 seconds, with immediate return to normal consciousness with no aura or postictal phase
      • Commonly associated with epilepsy disorders such as childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, and epilepsy with myoclonic absences
    • Atypical have a less abrupt onset and offset and often associated with loss of muscle tone or subtle myoclonic jerks.
      • Typically occurs at <2.5 Hz
      • Lasts 10 to 45 seconds with often incomplete impairment of consciousness with continued purposeful activity, albeit done more slowly.
      • Brief postictal confusion can sometimes occur.
      • Associated with Lennox-Gastaut syndrome and Dravet syndrome
    • Myoclonic have an abrupt onset and offset of staring and loss of awareness with continuous rhythmic jerks of shoulders, arms, legs, head, or perioral muscles.
      • Typically occurs at 2.5 to 4.5 Hz
      • Lasts 10 to 60 seconds with impairment of consciousness varying from complete loss of awareness to retained awareness
      • Associated with epilepsy with myoclonic absences, learning disability, and behavioral problems
    • Eyelid myoclonia have an abrupt onset and offset of repetitive, rhythmic jerks of the eyelids with simultaneous upward deviation of the eyeballs and extension of the head.
      • Typically occurs at 4 to 6 Hz
      • Lasts <6 seconds with incomplete impairment of consciousness and often with awareness mostly retained
      • Associated with epilepsy with eyelid myoclonus


  • Predominant age of onset: between 4 and 10 years, with peak onset between 5 and 7
  • Predominant gender: female > male (2:1) with male predominance in myoclonic absence seizure


  • 0.7 to 4.6 /100,000 in general population (2)
  • 6 to 8/100,000 per year in children up to 15 years of age (2)

Prevalence: 5 to 50/10,000 (3)

Etiology and Pathophysiology

  • Etiology is mainly genetic with complex, multifactorial inheritance; however, may be secondary to a variety of congenital or acquired brain disorders such as hypoxia–ischemia, trauma, CNS infection, cortical malformations, or inborn errors of metabolism.
  • Absences are triggered in the cortico-thalamic-cortical system when γ-aminobutyric acid (GABA)-mediated activity induces prolonged hyperpolarization and activates T-type (“low-threshold”) calcium channels, resulting in sustained-burst firing of these neurons, causing absence seizures.


  • 75% concordance occurs in monozygotic twins; 84% share EEG features (4).
  • 15–44% of patients with CAE have a family history of epilepsy.
  • Mutations of GABA-A/B receptors—involved in spike-wave discharges
  • Mutations in calcium channels (CACNA1 A, CACNA1 H, CACNA1 I, CACNG3)—thalamocortical dysrhythmia
  • Mutations of SLC21A, which encodes GLUT1—associated with worse prognosis
Onset of absence seizures <4 years; consider GLUT1 deficiency syndrome.

Risk Factors

Seizures of any kind can be triggered by:

  • Lack of compliance with medications
  • Lack of sleep
  • Alcohol use
  • Use of medications that lower seizure threshold
  • Hyperventilation

Commonly Associated Conditions

Approximately 60% of children have neuropsychiatric comorbidities including attention deficit and mood disorders (5).

  • Includes difficulties in visual attention and visuospatial skills, verbal learning and memory, fine motor skills, executive functions, reduced language abilities, ADHD, anxiety, depression, social isolation, and low esteem

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