Chapter 557

### Seizures

An epileptic seizure is a change in neurologic function (motor, sensory, experiential, or autonomic) that is associated with an abnormal synchronous discharge of cortical neurons. Usually that discharge can be recorded by routine electroencephalogram (EEG) using scalp electrodes, although occasionally, because the discharge’s location is on a surface distant from the scalp (eg, mesial temporal, orbitofrontal, mesial frontal, basal, or insular cortex), it can only be recorded by surgically implanted electrodes. Although the term seizure is sometimes used to refer to any paroxysmal event, in this chapter seizure always refers to an epileptic seizure, driven by an abnormal neuronal discharge. A convulsion is an epileptic seizure that results in involuntary muscle contractions. The term epileptic seizure always requires some clinical change in the patient, either observed by others or reported by the patient himself or herself. Occasionally, a seizure discharge is recorded on the EEG without any associated clinical change. Such discharges are referred to as electrographic seizures or electrographic seizure patterns.

### Epilepsy

Epilepsy refers to a tendency to spontaneous, recurrent seizures usually defined by the experience of having had two or more unprovoked seizures. This definition excludes certain types of provoked seizures, such as seizures caused by fever during childhood (febrile seizures), seizures caused by a temporary metabolic derangement such as hypoglycemia or hyponatremia, or seizures that occur in the setting of an acute central nervous system (CNS) insult such as stroke, trauma, or meningitis. Seizures that occur exclusively during the newborn period are also traditionally excluded from the definition of epilepsy because the majority of these are considered provoked seizures.

#### A Note on the Terms Idiopathic, Cryptogenic, and Symptomatic

The term idiopathic epilepsy literally refers to an epilepsy “unto itself” (idios, Greek), meaning an epilepsy that has not occurred as a consequence of another condition or disorder (eg, head trauma) but a situation in which epilepsy is the disorder. The primary generalized epilepsies come under this category, and in this usage, the term primary is synonymous with idiopathic. The genetic focal epilepsy syndromes also belong to this category of idiopathic epilepsies. Note that the term idiopathic epilepsy does not imply an epilepsy without known cause, as the genetic underpinnings of the primary generalized (idiopathic) epilepsies are rapidly being elucidated. The term idiopathic epilepsy does not, however, simply apply to any epilepsy syndrome in which all neurological testing is negative. In some instances, an underlying cause is suspected, although it cannot be specifically identified. Such cases are referred to as cryptogenic epilepsy (the cause is hidden but presumed to exist). Finally, the term symptomatic epilepsy is used for a seizure disorder that has a clear cause (eg, the seizures that follow the occurrence of a stroke).

Variations in the reported population rates of epilepsy in children may be due to true differences in the populations studied but may also be ...

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