Background

The background EEG may be normal, or may show focal or widespread slowing.

Interictal

Focal interictal spikes or polyspikes may be seen. Multi-focal independent spikes or generalized spike-and-wave (usually < 3 Hz) may also occur.

Activation

EEG abnormality is enhanced by sleep deprivation and in sleep.

Ictal

The presence of focal, rhythmic epileptiform discharges may be seen, with focal seizure types. If generalized seizures are present, the ictal EEG associated with these seizure types may be seen.