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The EEG background is normal.

CAUTION Generalized slowing is not seen.

CAUTION Focal slowing seen consistently over one area right arrow consider structural brain abnormality.


Generalized spike-and-wave or polyspike-and-wave is seen in the interictal EEG. Half of patients have these abnormalities only in sleep.

CAUTION Although focal spike-and-wave can occur, if seen consistently in one area right arrow consider structural brain abnormality.

CAUTION Slow spike-and-wave (<2.5Hz) is not seen right arrow consider other epilepsy syndromes.


An intermittent photoparoxysmal response to photic stimulation may be seen.

EEG abnormality is enhanced by sleep deprivation and in sleep. Generalized spike-and-wave often becomes fragmented with sleep deprivation or in sleep. Fragmented generalized spike-and-wave can appear focal or multi-focal but usually is not consistently seen in one area. The morphology of the focal spike-and-wave typically appears similar to the generalized spike-and-wave.


With generalized tonic-clonic seizures, the ictal EEG is often obscured by artifact. Generalized fast rhythmic spikes are seen in the tonic stage. Bursts of spikes and after-coming slow waves are synchronous with clonic jerks. A postictal period of irregular slow activity follows.

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