Children with epilepsy are at risk for cognitive disorders. They experience more academic underachievement and frequently suffer from impaired attention. These problems are found even in those children with epilepsy and a normal intelligence. In this chapter, we will concentrate on school-age children with epilepsy. We will review learning disorders (LD) and attention deficit hyperactivity disorder (ADHD). Additional information on mental retardation can be found in Chapters 27 and 28 and more information on cognitive problems in Chapter 33.

Learning disorders and ADHD will be covered together for several reasons. First, both have significant impact on academic success. While LD quite obviously impacts school performance, ADHD in children with epilepsy may have a similarly negative effect on school performance. Williams et al¹ found that ADHD in children with epilepsy was a better predictor of academic difficulties than memory, socioeconomic status, or self-esteem. Second, LD and ADHD are frequently comorbid conditions. Approximately 30–35% of children with ADHD have LD.² Finally, these two problems initially may be difficult to distinguish. Attention deficit hyperactivity disorder may be mistaken for LD and vice versa. However, treatment of the two disorders is quite different.

Learning disorders must be distinguished from intellectual disability or mental retardation (MR). Intellectual disability is defined as a significantly below average intelligence with IQ scores of 70 or below on standardized, individually administered tests of cognitive function, impairment in multiple areas, and an onset prior to 18 years of age. The IQ score is used to delineate severity levels. Severity levels range from mild MR, with IQ scores of 50–70, to profound MR, with IQ score less than 20 or 25.³

Learning disorders, also called academic skills disorders or learning disabilities, have been defined in two somewhat different ways. The first is the discrepancy model that compares academic achievement to intelligence. In the current DSM-IV-TR, a diagnosis of learning disorders requires scores of achievement on a standardized, individually administered test that are below the level expected for the child’s age, intelligence measured by psychoeducational testing, and education.³ The disability must cause impairment and should not be explained by sensory deficits. Categories are reading disorder, mathematics disorder, disorder of written expression, and learning disorder not otherwise specified. Motor skills disorder and communication disorders are separate categories.

A second way of classifying learning disorder uses a below-average performance on a standardized measure of academic performance without regard for the child’s intelligence. As an example, if a child had an IQ score 1.5 standard deviation (SD) below normal and a reading achievement score 1.5 SD below normal, the child would be considered to have a reading disorder. The distinction in definition of learning disorder is important practically in the determination of which child receives special education services in a school system.

Attention deficit hyperactivity disorder and problems with attention are similar and overlapping concerns but are not the same entities. Attention deficit hyperactivity disorder is a categorical (either present or absent) diagnosis defined by the presence of 6 of 9 symptoms of inattention and/or 6 of 9 symptoms of hyperactivity or impulsivity, starting before 7 years of age, causing impairment in two or more settings, and not better explained by other psychiatric disorders.³ The diagnosis is made on the basis of history and questionnaires completed by parents, teachers, and occasionally the child or adolescent. In comparison, attention is a dimensional (existing on a continuum) psychological construct. It is measured by a variety of tests of problem solving, executive function, and performance. In children with epilepsy, deficits in sustained attention are particularly common.⁴ Patients may have difficulties with attention without meeting criteria for ADHD and, in the unusual case of ADHD, predominantly hyperactive/impulsive type ADHD without impaired attention.

PREVALENCE OF LEARNING DISORDERS AND ADHD IN CHILDREN WITH EPILEPSY

We are aware of only one study that assessed the prevalence of learning disorder in children with epilepsy using the two separate definitions of learning disorder. Fastenau et al studied 173 children with epilepsy aged 7–15 years using an IQ screen and academic achievement testing.⁵ Domains assessed were reading, mathematics, and written expression. Using the IQ achievement discrepancy definition, they found that 48% of the children could be labeled as having a learning disorder. When learning disorder was defined by an achievement test score 1 SD below the mean, 62% of the children met criteria for LD and, using 1.5 SD below the mean, 41% could be considered to have a learning disorder. Depending on the definition used, 13–32% had a reading disorder, 20–38% a mathematics disorder, and 35–56% a disorder of written expression.

Though the definitions varied, other groups also found higher rates of academic problems in children with epilepsy. Seidenberg et al⁶ studied 122 children, 7–15 years of age, with an IQ of 70 or above. Using a definition of learning disorder as 1SD below expected for IQ, he found word recognition problems in 10.5% of boys and 10.1% of girls, spelling problems in 33.3% and 15.9%, mathematic difficulties in 28.1% and 31.9%, and reading comprehension impairment in 22.8% and 13%. Mitchell et al⁷ also used the IQ discrepancy model in a study of 78 children 5–13 years of age with an IQ of 80 or above and found reading disorder in 16%, reading comprehension problems in 38%, spelling difficulty in 32%, mathematics disorder in 31% and below average general knowledge in 50%. Bailet and Turk⁸ reported that 19% of children with epilepsy and a normal intelligence received special education services and 34% repeated a grade. Berg et al⁹ found that 58% received special education services at some time during the 5 years after an initial seizure.

Attention deficit hyperactivity disorder is also found frequently in children and adolescents with epilepsy. Reported prevalence rates have varied substantially with rates of 0–77% found depending on study population and methods of determining problems with attention. One population-based study noted symptoms of ADHD in 44% of children with epilepsy.¹⁰ Clinic-based studies utilizing DSM or other standard criteria commonly report symptoms of ADHD in 25–40% of children with epilepsy. Though not conclusive, there is some indication that ADHD, predominantly inattentive type is more common than ADHD combined type in children with epilepsy.¹¹

RISK FACTORS

Just as epilepsy is a heterogeneous disorder with multiple different syndromes and levels of severity, the causes of academic problems are multiple and specific for the individual patient. Variables interact with some having more direct effects on learning and other moderating the effects of the primary variables. Central nervous system function, including neuropsychological deficits and seizure-related variables seem to have the most direct effect on academic function, while family factors and child response to illness have moderating effects. Family history of LD and/or ADHD should be significant. Biederman and Faraone¹² estimated a heritability of 0.76 for ADHD in the general population; however, family history is seldom assessed in studies of LD and ADHD in children with epilepsy.

Support for the importance of underlying CNS dysfunction causing both epilepsy and academic problems comes from studies of new-onset seizures, from the different effects of seizure syndromes, and from results of imaging studies. Three studies of new-onset seizures found that children with epilepsy were more likely than controls to have repeated a grade, required special education services, or scored lower on teacher ratings or school-based standardized tests prior to the diagnosis of epilepsy.^9,13,14 This suggests that underlying CNS dysfunction caused both seizures and academic difficulties. Both Nolan et al¹⁵ and Berg et al¹⁶ found that children with symptomatic or cryptogenic generalized epilepsy syndromes had more cognitive or adaptive problems than children with idiopathic generalized epilepsy syndromes or with partial epilepsies. Symptomatic and cryptogenic generalized epilepsies are more often associated with CNS dysfunction than other seizure syndromes. Byars et al¹⁷ described an association between MRI abnormalities and deficits on neuropsychological testing in a sample of children with recent-onset seizures. Rantanen et al¹⁸ described intellectual disability in 50% of children 3–6 years of age with epilepsy noting an association between intellectual disability and early age of onset, abnormal MRI, additional neurological deficits, and complicated epilepsy.

Seizure-related factors are an additional direct cause of academic problems. There is an overlap with CNS dysfunction as symptomatic generalized epilepsies are most strongly associated with learning disorders and these are the epilepsies most likely associated with underlying CNS structural damages. Other seizure related factors seem to have lesser impact on academic performance. Aldenkamp et al found an association of academic underachievement with localized and symptomatic generalized epilepsies.¹⁹ In addition, frequent EEG discharges and antiepileptic drug (AED) polytherapy were associated with impaired vigilance. However, EEG discharges and AED polytherapy were associated with seizure syndrome, suggesting that seizure syndrome had the primary effect on academic performance. In a 3-year prospective study, there was no difference between reading and math scores of children with seizures and siblings at baseline, but the scores were lower in children with seizures than in siblings at 36 months.²⁰

Academic performance problems are often attributed to AEDs though disentangling the effects of AEDs from seizure syndrome, seizure frequency, frequency of EEG discharges, and the behavioral and psychosocial responses to illness is difficult. When compared to placebo, many AEDs have adverse cognitive effects, but when compared to other AEDs, barbiturates and topiramate appear more likely to cause academic problems.²¹ Polytherapy and elevated serum levels of AEDs also contribute to cognitive dysfunction. Even though adverse cognitive effects may be less likely with some of the newer AEDs, clinicians should monitor academic progress when starting any AED or increasing dosage as children may have their own unique idiosyncratic response to medication.