Rational use of EEG in childhood epilepsy.

Electroencephalogram (EEG) helps in diagnosing seizures and various childhood epileptic syndromes that have significant treatment implications. It represents the electric activity of the brain. Activating procedures can further increase the diagnostic yield. Besides diagnosing, it has a role in discontinuation of treatment and drug monitoring. EEG has its own limitations--it can be normal in an epileptic child and abnormal in a normal one. Electrical activity of the brain varies with age and physiological states like sleep. In neonates the background activity is much more important than epileptiform discharges unless these are repetitive and focal. Pseudo-epileptiform patterns like fourteen and six Hz activity can be confusing. Common typical epileptiform patterns seen in childhood are hypsarrhythmia in infantile spasm, burst suppression in early infantile epileptic encephalopathy, generalised 3 Hz spike wave discharges in absence seizures and periodic complexes in SSPE. EEG patterns like low voltage, electro-cerebral inactivity, multifocal spikes and excessive slow background are associated with poor outcome in neonates. Newer approaches have increased the yield and made localisation more precise. Epilepsy is a clinical diagnosis but EEG has significant role in substantiating the clinical suspicion, classification and management.