Researchers at Alberta Children’s Hospital Research Institute, Calgary, AB, Canada, and Epilepsy Center, New York University, NY analyzed WISC-IV scores from 212 children, 106 with epilepsy (46 girls, 60 boys; mean age 11 years), and 106 controls matched for age, gender, ethnicity, and parental education. Full Scale IQ for the epilepsy group was significantly lower than for controls; 36.8% had FSIQ < 70 vs <1% controls. In children with epilepsy, Working Memory and Processing Speed Index scores were lower than those for Verbal Comprehension and Perceptual Reasoning (p<0.01). Scores were highest on visual and verbal subtests measuring reasoning skills such as Matrix Reasoning, and lowest on Coding. The Coding subtest identified the most children (28.3%) with low scores, and the Similarities subtest identified the fewest (16%). Later age at onset and shorter epilepsy duration were both correlated with higher WISC-IV FSIQ and index scores. Number of AED trials but not seizure frequency was inversely correlated with FSIQ and index scores. FSIQ, index scores, and subtest scores were not related to left or right-hemisphere seizure foci or to MRI findings. The WISC-IV is useful in detection of cognitive deficits related to childhood epilepsy. [1]

COMMENT. Cognitive impairments in children with epilepsy are secondary to the effects of seizures and AEDs and are sometimes primary, associated with abnormal brain circuitry of epilepsy and predating the onset of seizures. The WISC-IV intelligence test is sensitive to cognitive impairments in children with epilepsy but is not sufficient for measuring some cognitive problems such as memory, sustained attention, executive function, and language deficits often present in children with epilepsy [2] Evaluation of the IQ and other neuropsychological functions is an important aspect of the comprehensive management of childhood epilepsy and an essential component of an Epilepsy Center.

Cognitive effects of interictal epileptiform EEG discharges. Simultaneous video-EEG recordings and cognitive testing in 188 children with epilepsy found that the association between frequent epileptiform activity and cognitive function, although less pronounced, is comparable to impairment of global cognitive function, central processing speed, and memory function that accompanies short nonconvulsive seizures. [3]. Transient cognitive impairment (TCI) is demonstrated in about 50% of patients who show epileptiform activity during testing Whether TCI influences school performance is unclear and is not generally an indication for AED therapy. The EEG activation or suppression effect of cognitive tasks is a phenomenon to be recognized in the evaluation of TCI effects on learning. [4]