Child Neurology Net

Absence Seizures

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Definition

Once known as petit mal seizures, absence seizures are probably very underdiagnosed.

Etiology/ Pathogenesis

Genetic and environmental factors both contribute to absence seizures. Genetic factors are thought to predominate in children who have typical absence seizures, whereas environmental factors predominate in children with atypical seizures.

Age of Onset

Generally between 6 and 8 years of age, if juvenile onset between 10 and 16 years.

Classic Presentation

Absence seizures can be difficult to tell apart from complex partial seizures. Children with absence seizures are often otherwise healthy, but may experience at least 1 generalized tonic-clonic seizure in their life. Seizures typically do not last longer than 30 seconds, and can occur up to hundreds of times a day.

During a seizure, the child will usually stop what they are doing, stare vacantly, and may have rhythmic movements of the eyelids or an extremity. Other associated features are myoclonus, head turning and semipurposeful movements such as picking at clothes. Longer seizures, such as those as long as 1 minute may be difficult to tell apart from complex partial seizures. The episodes are without aura or postictal state. The degree of consciousness impairment is variable, some remember nothing of the episodes, while others may be able to have conversations and remember everything that occurs during the seizure.

Rarer Symptoms

Usual Course

Absence seizures have a remission rate of 80%, generally stopping around the age of 10 years. Favorable prognosis is predicted by lack of a family history of epilepsy, young age at onset, normal interictal EEG and normal intelligence level. Those with juvenile onset are more likely to persist into adulthood.

Genetics

Although no genes have specifically been identified, studies show that between 15% - 40% of children with absence seizures have a family history of epilepsy. In addition, monozygotic twins have a 75% concordance rate for epilepsy, 85% concordance rate for EEG abnormalities.

Groups at high risk

Diagnostic Testing

EEG shows characteristic finding of 3 cps spike and wave complexes during the seizure. Interictal EEG is usually normal, those with abnormal interictal EEGs are more likely to have mental retardation or developmental delay.

Differential

Daydreaming
Complex partial seizures

Treatment

Ethosuximide and Valproate are used alone or in combination. Either may be used with Lamotrigine in combination therapy.

Misc

Websites with additional info

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Definition	Once known as petit mal seizures, absence seizures are probably very underdiagnosed.
Etiology/ Pathogenesis	Genetic and environmental factors both contribute to absence seizures. Genetic factors are thought to predominate in children who have typical absence seizures, whereas environmental factors predominate in children with atypical seizures.
Age of Onset	Generally between 6 and 8 years of age, if juvenile onset between 10 and 16 years.
Classic Presentation	Absence seizures can be difficult to tell apart from complex partial seizures. Children with absence seizures are often otherwise healthy, but may experience at least 1 generalized tonic-clonic seizure in their life. Seizures typically do not last longer than 30 seconds, and can occur up to hundreds of times a day. During a seizure, the child will usually stop what they are doing, stare vacantly, and may have rhythmic movements of the eyelids or an extremity. Other associated features are myoclonus, head turning and semipurposeful movements such as picking at clothes. Longer seizures, such as those as long as 1 minute may be difficult to tell apart from complex partial seizures. The episodes are without aura or postictal state. The degree of consciousness impairment is variable, some remember nothing of the episodes, while others may be able to have conversations and remember everything that occurs during the seizure.
Rarer Symptoms
Usual Course	Absence seizures have a remission rate of 80%, generally stopping around the age of 10 years. Favorable prognosis is predicted by lack of a family history of epilepsy, young age at onset, normal interictal EEG and normal intelligence level. Those with juvenile onset are more likely to persist into adulthood.
Genetics	Although no genes have specifically been identified, studies show that between 15% - 40% of children with absence seizures have a family history of epilepsy. In addition, monozygotic twins have a 75% concordance rate for epilepsy, 85% concordance rate for EEG abnormalities.
Groups at high risk
Diagnostic Testing	EEG shows characteristic finding of 3 cps spike and wave complexes during the seizure. Interictal EEG is usually normal, those with abnormal interictal EEGs are more likely to have mental retardation or developmental delay.
Differential	Daydreaming Complex partial seizures
Treatment	Ethosuximide and Valproate are used alone or in combination. Either may be used with Lamotrigine in combination therapy.
Misc
Websites with additional info