In addition to seizure type, epilepsy can also be defined in terms of etiology (cause). The etiology often affects the child’s prognosis and treatment. Doctors refer to three types of epilepsy: idiopathic, symptomatic, and cryptogenic.
Idiopathic epilepsy
About 30% of childhood epilepsy is idiopathic. Idiopathic epilepsy is epilepsy in which there is no apparent underlying cause, such as a structural problem with the brain or a metabolic disorder. It is possible that idiopathic epilepsy is caused by tiny abnormalities at the cellular level.
Idiopathic epilepsy syndromes often run in families. We are now learning that many idiopathic epilepsy syndromes have an associated genetic component.
The good news with a diagnosis of idiopathic epilepsy is that there is no brain tumour or other abnormality, and that the child is more likely to outgrow her seizures.
The terms “idiopathic” and “cryptogenic” are sometimes used interchangeably, especially in older books and articles.
Symptomatic epilepsy
Between 25% and 45% of childhood epilepsy is probably symptomatic. Symptomatic epilepsy is caused by known structural abnormalities or damage in the brain or by an underlying disease, such as:
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congenital brain malformation
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injury or trauma (at birth or later)
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lack of oxygen to the brain causing damage
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infection with permanent damage
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tumour
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tangle of blood vessels
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stroke
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metabolic disorder
Your child’s doctor will want to rule out these possible causes with a neurological exam, laboratory tests, and possibly with brain imaging such as a CT scan or an MRI. Structural abnormalities may or may not be visible with brain imaging.
Cryptogenic epilepsy
In cryptogenic epilepsy, doctors suspect that a child’s epilepsy is symptomatic, but cannot locate the underlying cause. In a case like this, the child usually has developmental delay or abnormal findings on her neurological exam. Sometimes doctors call this type of epilepsy “probably symptomatic.”
The terms “idiopathic” and “cryptogenic” are sometimes used interchangeably, especially in older books and articles.
You can read more about idiopathic, symptomatic, and cryptogenic epilepsy in this section. Click the links on the left to learn more.