Primary Generalized Seizures with Spike and Wave Discharge
Primary generalized seizures are epileptic attacks in which the ictal discharge appears to start in all regions of the brain simultaneously (8). In this group bilaterally synchronous spike and wave (SW) discharges, as they occur in man during absence attack, can be regarded as the mildest form of generalized seizures. Generalized SW discharges appear suddenly and simultaneously in both cerebral hemispheres with an amplitude exceeding several times that of the normal EEG background activity. As shown in Figure 1, the SW pattern consists of an alternation between a brief polyphasic spike of usually less than 100 ms duration and a dome-shaped negative slow wave of about 300 ms duration occurring at a frequency of approximately 3 Hz. Within the polyphasic spike two brief negative and one longer positive components can often be discovered (44). A burst of generalized SW discharge stops just as abruptly as it had started and leaves no postictal depression of the EEG in its wave (Figure 1). If a generalized tonic-clonic convulsion evolves from generalized SW discharge, the slow wave component of the SW complex disappears and at least during the tonic phase, the discharge consists of uniform, rhythmic waves at a frequency of about 10 Hz.
KeywordsCortical Excitability Generalize Epilepsy Wave Discharge Thalamic Neuron Cortical Hyperexcitability
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