The EEG background may be normal at presentation, but over time there is a loss of normal rhythms and progressive slowing in the affected hemisphere.
Epileptiform abnormality in the affected hemisphere.
In the chronic phase, EEG abnormality is enhanced by sleep deprivation, in drowsiness and in sleep.
The ictal EEG at presentation with focal motor status epilepticus is characterised by rhythmic slow (2-3Hz) waves that are usually bilateral with higher amplitude over the affected hemisphere.