EEG intercritical anomalies and cognitive performances.

The relationship between focal or generalized paroxysmal discharges and cognitive performances are complex. In the one hand, alertness is known as an important factor associated with the reduction of spike-wave discharges. In the other hand, it has been shown that interictal discharges non accompanied by apparent simultaneous clinical manifestations may be associated with transitory cognitive impairment detectable by appropriate psychological testing like continuous performance tests. The variables of importance are the nature of the task, the form, the duration and the extension of the discharges and the time of their occurrence within the stimulus processing. The studies of transitory cognitive impairment are very useful to evaluate the handicap due to apparently sub clinical epileptic discharges and its relationship with learning and attention disabilities often observed in epileptic children. The results of prospective studies particularly in so called benign childhood epilepsy might lend to reconsider the issue of the anti epileptic treatment.