The EEG background is normal.
CAUTION Background generalized slowing is not seen consider other syndromes.
CAUTION Focal slowing seen consistently over one area consider structural brain abnormality.
Brief bursts of fast (3-6 Hz) generalized polyspike-and-wave.
CAUTION Focal spikes seen consistently in one area consider structural brain abnormality.
CAUTION A normal EEG is not expected in this syndrome, even when seizures are controlled.
Eye closure (fixation off sensitivity) and intermittent photic stimulation activates the EEG and often elicits eyelid myoclonias with/without absences. Response to intermittent photic stimulation may be less in older patients and those on medication. EEG abnormality is also facilitated by hyperventilation.
Generalized spike-and-wave often becomes briefer and 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.
Eyelid myoclonia is accompanied by high amplitude generalized spike-and-wave or polyspike-and-wave at a frequency of 3-6 Hz. Ictal EEG and clinical events are terminated with complete elimination of light.