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Excerpt from EEG in Common Epilepsy Syndromes

Synonyms, Key Words, and Related Terms: absence epilepsy, neonatal seizures, symptomatic epilepsy, cryptogenic epilepsy, idiopathic epilepsy, benign partial epilepsy of childhood with occipital paroxysms, benign rolandic epilepsy, hypsarrhythmia, infantile spasms, juvenile absence epilepsy, juvenile myoclonic epilepsy, West syndrome, Lennox-Gastaut syndrome

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EEG is an essential component in the evaluation of epilepsy. The EEG provides important information about background EEG and epileptiform discharges and is required for the diagnosis of specific electroclinical syndromes.¹ Such a diagnosis carries important prognostic information, guides selection of antiepileptic medication, and suggests when to discontinue medication. Neurologic examination and imaging in the essential idiopathic, typically genetic, epilepsies are usually normal.²

EEG background frequencies

Following a seizure (ie, during the postictal period) the EEG background may be slow. However, interictal background EEG frequencies that are slower than normal for age usually suggest a symptomatic epilepsy (ie, epilepsy secondary to brain insult). Normal background suggests primary epilepsy (ie, idiopathic or possibly genetic epilepsy). Thus, EEG background offers important prognostic and classification information.

Epileptiform discharges

These help separate generalized from focal (ie, partial) seizures.

Epilepsy syndromes

Symptomatic epilepsy - Seizures resulting from an identifiable cerebral disorder
Cryptogenic epilepsy - Seizures occurring without identifiable cause in a patient with cognitive impairment or with neurological deficits (Examples of cryptogenic epilepsy include Lennox-Gastaut syndrome (LGS), infantile spasms, and myoclonic astatic epilepsy of Doose.)
Idiopathic epilepsy - Seizures occurring without an identifiable cause in a patient with entirely normal findings on neurologic examination and of normal intelligence (Examples of idiopathic epilepsy include benign partial epilepsy of childhood with centrotemporal spikes, benign partial epilepsy of childhood with occipital paroxysms, and juvenile myoclonic epilepsy.)

EEG characteristics of these specific electroclinical epilepsy syndromes are discussed in this article. Roles of EEG in temporal lobe epilepsy and frontal lobe epilepsy, among others, are not addressed here.

For related information, see Medscape's Epilepsy Resource Center.

Please click here to view the full topic text: EEG in Common Epilepsy Syndromes

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