Background

The background is EEG normal.

CAUTION Focal slowing consistently seen in one area consider structural brain abnormality.

Interictal

Generalized spike- and polyspike-wave at 3-5.5Hz can be seen in awake and asleep states. This finding is required for diagnosis of this syndrome. Fragmented generalized spike-wave can appear as focal or multi-focal spike-wave, but is not consistently seen in one area. The morphology of the focal spike-wave is similar to that of the generalized spike-wave.

CAUTION Focal spikes consistently seen in one area consider structural brain abnormality.

CAUTION Slow spike-wave (<2.5Hz) is not seen consider other epilepsy syndromes.

Activation

A photoparoxysmal response to intermittent photic stimulation is seen in up to 90% of cases, however seizures induced by visual stimuli in daily life are seen in <10%.

Generalized spike- or polyspike-wave and (in patients with absence seizures) clinical absences may be provoked by hyperventilation.

CAUTION Where hyperventilation is performed well for three minutes and no generalized spike-wave is seen, absence seizures are unlikely.

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

Ictal

A single generalized polyspike-wave correlates with the myoclonic seizure, the myoclonus occurs concurrently with the polyspike.

With generalized tonic-clonic seizures, the ictal EEG is often obscured by artifact. Generalized fast rhythmic spikes are seen in the tonic stage. Bursts of spikes and after-coming slow waves are synchronous with clonic jerks. A postictal period of irregular slow activity follows.

A regular fast (3-5.5Hz) generalized spike- or polyspike-wave discharge accompanies absence seizures.