To determine the extent of the association between seizures and mental retardation (MR) or CP (cerebral palsy), investigators have also looked at the frequency of these disabilities in children with epilepsy.

Population-based studies

Finland

To obtain information on morbidity and development, children born in 1966 in two Finnish provinces were followed up to the age of 14.35 A combination of information sources was initiated during the mother’s pregnancy in 1965. Data were available for 96% of all children born in those provinces during that year. Among children who experienced at least “one episode of paroxysmal disturbance of consciousness, sensation, or movement not associated with acute febrile episodes,” the reported proportion with MR (IQ <70) was 21.2%, and the proportion with CP was 15.9%. Among children with MR, epilepsy was more common in children with lower IQ:

IQ Proportion with epilepsy
50–70 5.8 %
<50 15.4 %

An unselected population of children aged 4–15 years residing in the province of Turku, Finland, was investigated to identify those who had experienced at least two unprovoked seizures.36 More than 31% of all children with epilepsy also had MR, defined as an IQ of less than 70.

Metropolitan Atlanta

Murphy and colleagues7 determined the frequency of MR among 10-year-old children with epilepsy who were enrolled in the Metropolitan Atlanta Developmental Disabilities Study. The identification of children with epilepsy was extended to a review of records from electroencephalography laboratories in hospitals, clinics, and private physician’s offices serving children of the Atlanta area. Epilepsy was defined as a history of two or more afebrile epileptic seizures diagnosed by a physician. MR (IQ <70) was present in 30% of the children with epilepsy, and CP was present in 18% of the children with epilepsy. Among the children with epilepsy and MR, 34% had an IQ between 50 and 70, whereas 66% were severely retarded, having an IQ of less than 50.

Others

In Sweden, Steffenburg et al.37 reported that 38% of children aged 6 to 13 years who had active epilepsy (at least one epileptic seizure during the 5-year period preceding the prevalence day, regardless of AED treatment) also had MR.

In the incidence series of epilepsy in Rochester, Minnesota, 8% of all cases had MR, CP, or both. These were codiagnoses in nearly 15% of children younger than 15 years who had newly diagnosed epilepsy.38

The National Collaborative Perinatal Project, which examined the incidence of MR, CP, and seizures in a cohort of approximately 50,000 infants followed from conception to age 7 years, also found a substantially increased rate of MR and CP in children with seizure disorders, especially among those with minor motor seizures.16

Clinical series

Braathen and Theorell39 evaluated the frequency of MR alone or in combination with other disabilities in an unselected population of newly diagnosed childhood epilepsy cases. The study included all children younger than 16 years who had epilepsy, defined as “recurrent unprovoked seizures of cerebral origin,” and who started treatment with AEDs during a 2-year period (1990–1992) in the catchment area of a general hospital of Southern Stockholm. They identified 79 children with epilepsy, 19 (24%) of whom had MR alone or in combination with other disabilities.

More recent community-based series have reported significant neurologic disability in a smaller proportion of children. Berg and colleagues40 identified a community-based, unselected cohort of 613 children (age 1 month to 15 years), who presented at the time of the first seizure and were prospectively identified at the time of diagnosis of epilepsy between 1993 and 1997 in Connecticut. Of this cohort, 18% had a remote symptomatic etiology, on the basis of the International League against Epilepsy classification,26 and the majority of patients had MR or CP.

Adapted from: D'Amelio M, Shinnar S, and Hauser WA. Epilepsy in children with mental retardation and cerebral palsy. In: Devinsky O and Westbrook LE, eds. Epilepsy and Developmental Disabilities. Boston: Butterworth-Heinemann; 2001;3–16. With permission from Elsevier (www.elsevier.com). 

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