Cognition in school-aged children with "active" epilepsy: A population-based study. 
There is a lack of population-based data on specific cognitive profiles in childhood epilepsy.  This study sought to determine the frequency of impairments in global cognition and aspects of working memory and processing speed in a population-based sample of children with "active" epilepsy (on antiepileptic Drugs (AEDs), and/or had a seizure in the last year).  Factors significantly associated with global and specific difficulties in cognition were also identified.  A total of 85 (74% of eligible population) school-aged children (5-15 years) with "active" epilepsy underwent comprehensive psychological assessment including assessment of global cognition, working memory, and processing speed.  Scores on cognitive subtests were compared via paired-samples t tests.  The factors associated with cognitive difficulties were analyzed via linear regression.  A total of 24% of children were functioning below IQ 50, and 40% had IQ scores below 70.  Scores on the Processing Speed Index were significantly lower than scores on the Verbal or Performance indexes on Wechsler instruments.  The Coding subtest was a significant weakness compared with the other Wechsler subtests.  A total of 58% of children displayed "memory underachievement" (memory score 1 SD below assessed IQ) on at least one of the four administered working memory subtests.  Factors significantly associated with globally impaired cognition included being on polytherapy (β = -13.0; 95% CI [-19.3, -6.6], p = .000) and having attention-deficit/hyperactivity disorder (ADHD; β = -11.1, 95% CI [-3.0, -19.3], p = .008).  Being on polytherapy was also associated with lower scores on the working memory and processing speed composite scores.  Having developmental coordination disorder (DCD) was associated with a lower score on the processing speed composite.  There is a high rate of global and specific cognitive difficulties in childhood epilepsy.  Difficulties are most pronounced in aspects of working memory and processing speed.  Predictors of cognitive impairment in childhood epilepsy include epilepsy-related and behavioral factors, which may differ depending on the domain of cognition assessed.