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  CHILDHOOD ABSENCE EPILEPSY

Introduction.
    One must be clear about the distinction between "absence Seizure" and "absence Epilepsy". Absence seizures are the main type of seizures seen in the condition named "absence epilepsy". However absence seizures may be seen in other epileptic syndromes and other types of seizures are seen in absence epilepsy. The main epileptic syndrome in which absence seizures are present is "Childhood Absence Epilepsy" (opposed to "Juvenile Absence Epilepsy", which has its onset later in life).

Historical.
Poupart 1705: first description
Tissot 1770: first well documented description.
Calmei 1824: "absence"
Esquirol 1838: "petit mal"
Gowers 1881: typical and atypical absences
Sauer 1916: Piknolepsy
Adie 1924: good prognostic epilepsy of children
Gibbs 1935: EEG description
Gas taut 1970: opposition typical vs. atypical absences

Definition.
1. Onset before puberty, but may start at a much later age.
2. Normal children prior to onset of epilepsy. CAE is idiopathic epilepsy and as such typically occurs in children with no neurological dysfunction.
3. Absences as FIRST type of seizures. Although a great number of children with CAE will have several different types of seizures, the absences must be the first type seen. Absences may occur during the evolution of another epileptic problem; this does not establish the diagnosis of Absence Epilepsy.
4. Frequent absences of all variety except myoclonic. Absences are of several subtypes: absences with impairment of consciousness only, absences with clonic component, absences with atonic component, absences with tonic component, and absences with automatisms. In childhood absence epilepsy, there are no myoclonic absences. The presence of this latter type of absences would exclude the diagnosis of CAE.
5. EEG bilateral, symmetrical, synchronous 3 Hz (Herz = number of impulses per second) SW (Spikes and Waves) discharges, usually regular, although more irregular SW are acceptable providing they occur with typical absences.

Description.
With these criterions CAE is a fairly homogenous entity.

General facts.
Frequency: About 7/100.000 children 0 to 15 years of age, 8% of school aged children epilepsies.
Sex ratio: Female more than male 3:1
Aetiology: Genetic predisposition: 15% to 44% cases have a family history of either absences or GTCS (Generalized Tonic Clonic Seizures).

Summary: 

    Childhood absence Epilepsy is a relatively rare form of generalized idiopathic epilepsy, occurring in until then normal children. There is a strong genetic predisposition. All types of absences except myoclonic absences, are the first type of seizures with the onset between 3 and 12 years of age, max. around 6-7 years. Absences are very frequent during the day, occurring either spontaneously or under external influencing factors. Their EEG correspondence is a bilateral, symmetrical and synchronous SW discharge. The SW's are in most of the patients regular, at a 3 c/s rhythm, but they may be irregular. Background activity is usually normal but may be mildly altered. A posterior slow rhythm may be seen in CAE, but it is probably simply a "genetic marker" which does not have major pathological signification. In fact it may have some protective value since when present, the child has fewer chances to develop generalized tonic clonic seizures than children with absence epilepsy and no slow posterior rhythm. One should add that this slow posterior rhythm has a greater diagnosis value than even the 3 Hz SW classically described in CAE. Slow posterior rhythm even without 3Hz SW would be enough to make the diagnosis of childhood absence epilepsy.
Absences tend to spontaneously disappear and are in 80% of cases easily stopped by specific anticonvulsive therapy. Long-term stabilization of the condition is frequent but 40% of the children will develop, during adolescence or even later an epilepsy with GTC seizure with a  relatively benign evolution. Very few patients have only absences during adulthood. Social insertion of these patients is often difficult. Childhood absence epilepsy must be carefully distinguished from other forms of epilepsy in which absences occur.