Duration of epilepsy and cognitive development in children: a longitudinal study

To study the pattern of cognitive development in relation to duration of epilepsy.

Participants were 113 children with epilepsy referred because of concerns about their cognitive development and tested at least twice at tertiary epilepsy settings. Verbal, Performance, and Full Scale IQ were measured with Wechsler Intelligence Scales. Various epilepsy and demographic variables were included. Change over time was modeled with multilevel analysis for longitudinal data with variable measurement occasion.

The Verbal and Full Scales could be fitted best as a downward progressing function. Earlier in time, decline was likely to be largest; later in time, decline followed a continuous, dwindling course. A similar trend was seen for the Performance Scale. Initially, Verbal IQ was higher than Performance IQ but this discrepancy decreased over time. Later onset of epilepsy was associated with an attenuated decline of the Verbal Scale. None of the other epilepsy variables were related to the course of cognitive development. Higher parental education was associated with higher IQ, but was not protective against decline.

Verbal IQ, though initially spared, drops. The Performance IQ, which may have shown its vulnerability earlier in the course of the epilepsy, shows overall smaller changes. It is suggested that seizures impact synergistically on an affected brain, which leads to progressive cognitive decline. Earlier onset of epilepsy is associated with relatively higher VIQ, larger VIQ > PIQ discrepancies and more decline.