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The cognitive deficit often associated with epilepsy is attributable to the presence and interaction of several factors but whether recurrent subclinical spike-wave discharges interfere with cognitive development is not yet clear. In the present study, the presence of subclinical discharges proved to be significantly associated with lower than average Full-Scale Intelligence Quotient (IQ), Verbal IQ and Performance IQ scores (Wechsler Intelligence Scale for Children) in comparison with patients not presenting EEG abnormalities during test. These findings confirm the adverse effect both of generalized and focal EEG epileptiform abnormalities, even if unaccompanied by overt seizures.

Altered cognitive functioning has often been reported in patients with epilepsy. In our study we looked for quantitative correlation between the recurrence of Subclinical Spike-and-Wave Discharges (SSWD) during EEG recording, the scores on the intelligence test (WISC) and the electro-clinical characteristics of 29 epileptic children with subclinical discharges of generalized spike-and-wave complexes. In our sample we found a below-normal mean IQ, with greater impairment on performance than on verbal tasks. No clear quantitative correlation was found between the weighted scores on the various subtests and the "time density" of the spike-and-wave complexes. These findings suggest that the SSWD interfere with cognitive development (mainly with visuo-spatial and sensorimotor coordination abilities) and selectively impair some of the functions involved in the cognitive processes.