Childhood Absence Epilepsy (CAE)

Overview

  • Childhood Absence Epilepsy is a common form of childhood epilepsy.
  • The seizures are typically brief with abrupt onset and offset, with automatisms present. Children can have many of these daily.
  • The EEG has 3 Hz spike and wave with an event. The EEG background is normal. The events with these correlates are accentuated by hyperventilation.
  • Monotherapy initially with ethosuximide, lamotrigine or valproate.
  • Juvenile Absence Epilepsy and Juvenile Myoclonic Epilepsy (with increased risk of generalised tonic clonic seizures) should be considered in a child with late seizure onset.

According to the NICE Guideline: The Epilepsies:

  • The seizure type(s) and epilepsy syndrome, aetiology, and co-morbidity, should be determined.
  • If there is diagnostic uncertainty, individuals should be referred to tertiary services soon (within 4 weeks) for further assessment.

Demographics

  • Prevalence: ~10% of childhood epilepsies.
  • Age at Onset: 2-10 years, Peak at 5 to 6 years.
  • Genetics: Genetically determined of unknown, probably polygenic, mode of inheritance.

Signs | Symptoms

Seizure Semiology

Absence seizure occurring frequently (tens or hundreds per day):

  • They are of abrupt onset and abrupt termination, lasting from 4 to 20 sec (mainly ~10 sec).
  • The hallmark of the absence is severe impairment of consciousness with unresponsiveness and interruption of ongoing voluntary activity. 
  • Automatisms occur in 2/3 of the seizures, but are not stereotyped. 
  • Mild myoclonic elements of eyes, eyebrows and eyelids may feature at the onset of the absence. 
  • More severe and sustained myoclonic jerks of facial muscles indicate other Idiopathic Generalised Epilepsies (IGEs).
  • Other seizure types (myoclonic astatic, myoclonus, and photic sensitive seizures) are incompatible with CAE.

Neurological and mental state

  • Normal

Seizure-precipitating factors

  • Absences are nearly invariably provoked by hyperventilation.

Differental diagnosis

  • Non-epileptic episodic disorders or daydreaming. 
  • Must be distinguished from focal seizures. Absences are multiple, brief with abrupt onset and offset. Focal seizures are often more prolonged, onset and offset are less clear, localizing signs maybe seen and typically there is a post ictal phase.
  • Hyperventilation for 3 mins will provoke an absence in as many as 90% of those with CAE who are not on medication.
  • Early onset absence epilepsy (less than 4 years) has been associated with GLUT1 disorders.
  • If late onset absence epilepsy (greater than 9 years), consideration of Juvenile Absence Epilepsy and Juvenile Myoclonic Epilepsy should be made. Age is not an absolute discriminator. Other factors such as the frequency and nature of absences and associated seizure types are critical. For example, in Juvenile Absence Epilepsy, there are few absences (<5 per day), while in Juvenile Myoclonic Epilepsy, myoclonic jerks are present and absences are subtle.
  • Patients who continue to have absences in teenage years are at risk of infrequent generalised seizures and may have other generalised epilepsies, not CAE.

Investigations

EEG

  • Normal background, with frequent rhythmic posterior delta activity.

  • Generalized 3 Hz (2.5 to 4 Hz) spike and slow-wave discharges.

Neuro imaging

  •   Not usually required

Prognosis

  • Excellent, with remission of absences usually before the age of 12 years if syndromal diagnosis correct. 
  • ~15% of patients with typical CAE prove later to have Juvenile Myoclonic Epilepsy.
  • If absences continue into adolescence, consider another syndromal diagnosis.
  • In patients with CAE, there is increased incidence of generalized tonic clonic seizures in adolescence.
  • Patients with CAE have increased incidence of learning difficulties and poor social adjustment has been reported.

Management

Management options

  • A randomised controlled trial1 showed ethosuximide has a better benefit to risk ratio for the treatment of CAE compared to sodium valproate and lamotrigine. The latter two drugs are alternative therapies. Ethosuximide does not protect against GTCS.
  • Vigabatrin, tiagabine, carbamazepine, and gabapentin can exacerbate absence seizures.

 Discuss with family

Resources

  • 1. Tracy A. Glauser et al. Ethosuximide, Valproic Acid, and Lamotrigine in Childhood Absence Epilepsy. N Engl J Med 2010; 362:790-799

References

  • Tracy A. Glauser et al. Ethosuximide, Valproic Acid, and Lamotrigine in Childhood Absence Epilepsy. N Engl J Med 2010; 362:790-799
  • Panayiotopoulos CP. The epilepsies: Seizures, syndromes and management: Based on the ILAE classifications and practice parameter guidelines. Chipping Norton, Oxfordshire: Bladen Medical Publishing; 2005.
  • Roger J, Bureau M, Dravet C, Genton P, Tassinari CA, Wolf P, editors. Epileptic syndromes in infancy, childhood and adolescence (4th ed).  Montrouge, France: John Libbey Eurotext Ltd ; 2005.