Background

The EEG background is normal.

Interictal

Interictal epileptiform abnormality may not be seen. Approximately 75% of cases show generalized ictal discharges, and approximately 25% have bilateral but asymmetric or unilateral discharges (lateralizing to the dominant hemisphere in all; 10% have focal temporoparietal discharges).

Activation

EEG abnormality is enhanced by sleep deprivation and in drowsiness and sleep.

Ictal

Myoclonic seizures are accompanied by brief sharp, spike, or sharp/spike-wave activity (which may be low voltage). These may be difficult to distinguish from accompanying myogenic artifact. Seizure features are subtle may be difficult to appreciate on video obtained during video-EEG, due to the subtle nature of the orofacial myoclonus and limited resolution of facial features during video-EEG. Direct video of the patient's face during reading can be helpful.