Lateralized effects of subclinical epileptiform EEG discharges on scholastic performance in children.

The interaction between lateralization of subclinical epileptiform discharges and cognitive tasks was investigated in 21 children (12 girls and 9 boys, mean age 10.6 years). Seventeen had a diagnosis of epilepsy (partial or secondarily generalized). Testing was by reading, arithmetic, and intelligence subtests during continuous telemetric EEG and video monitoring. Children with left-sided discharges had significantly lower reading performance than children with right-sided discharges. During reading, epileptiform discharges occurred relatively less frequently and with a shorter total duration over the left hemisphere than the right. This supports the view that cognitive tasks suppress epileptiform discharges when they activate a region of the brain within the epileptogenic zone. Discharges from other epileptogenic zones not directly activated by the tasks are increased, however.