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JUVENILE MYOCLONIC EPILEPSY

Background

The background is EEG normal.

CAUTION Generalized slowing is not seen.

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

Interictal

The interictal EEG may have generalized spike-and-wave and polyspike-and-wave, usually at 3.5-6Hz. In one third of cases, fragmented generalized spike-and-wave can appear focal or multi-focal, but usually is not consistently seen in one area.

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

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

Activation

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

Generalized spike-and-wave or polyspike-and-wave and clinical absences may be provoked by hyperventilation.

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

EEG abnormality is enhanced by sleep deprivation and by sleep. Generalized spike-and-wave often becomes fragmented with sleep deprivation or in sleep. Fragmented generalized spike-and-wave can appear focal or multi-focal but usually is not consistently seen in one area. The morphology of the focal spike-and-wave typically appears similar to the generalized spike-and-wave.

Ictal

A single generalized polyspike-and-wave correlates with the myoclonic seizure.

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.

Regular fast (3.5-6Hz) generalized spike-and-wave or polyspike-and-wave accompanies absence seizures.

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