Background

The background EEG is normal.

Interictal

Occipital sharp- or spike-wave is seen in the interictal EEG of the majority of patients with this syndrome, but may only occur in the sleep EEG. Centrotemporal, frontal or generalized spike-wave may co-exist (seen in 20% of cases).

CAUTION This epilepsy syndrome can evolve to developmental and/or epileptic encephalopathy with spike-wave activation in sleep consider a sleep EEG if there is cognitive deterioration.

Activation

Fixation-off sensitivity (facilitation of epileptiform discharges with elimination of central vision) is seen in 20-90% of patients. EEG abnormality is enhanced by sleep deprivation, in drowsiness and in sleep. It is debated whether a response to intermittent photic stimulation can be seen in this syndrome or is exclusionary.

Ictal

At ictal onset, there is a reduction in the usual background occipital sharp- or spike-wave with appearance of occipital faster rhythms with spikes of low amplitude. There may be slower spike-wave during oculo-clonic seizures or ictal blindness.