Risk of epilepsy among children with developmental disabilities

The reported frequency of epilepsy among children with mental retardation (MR) or cerebral palsy (CP) varies widely. Explanations for this variation include:

• differences in the definition of epilepsy (e.g., inclusion of single or complex febrile seizures or single seizures)
• sources for case ascertainment (hospitals, private doctor’s offices, services for children with mental disabilities)
• differences in the severity of MR or CP in children involved in the studies.

Current knowledge of the risk of epilepsy in mentally retarded children derives from three different sources:

• studies of MR that report information about epilepsy
• studies of CP that include information about epilepsy and MR
• studies of epilepsy that report information about MR or CP

Factors predictive of epilepsy

The factors associated with the development of epilepsy in children with neurologic deficits from birth are not simple. A study evaluating prenatal and perinatal etiologies characteristics of children affected by cerebral palsy (CP) alone, CP and mental retardation (MR), or CP, MR, and epilepsy found that patients with a combination of the three disabilities were more likely to have a history of neonatal convulsions (a reflection of severity of insult?) and a family history of epilepsy in first-degree relatives.41 The combination of CP, MR, and epilepsy was less likely to occur in some circumstances:

• mothers older than 32 years at delivery
• gestational age of less than 32 weeks
• birth weight of less than 1,500 g

Similar findings were observed in a clinic-based cohort from the Kennedy Center in the Bronx.27,28 In this series, mean birth weight was greater and gestational age longer in the children with CP and epilepsy. Neonatal seizures were more frequent in children with MR and CP without epilepsy.

Familial predisposition to epilepsy in children with CP was noted by Aksu,42 who found a history of epilepsy in parents or siblings of 16% of patients with CP, as compared to only 8% of children with epilepsy without CP.

The findings of these studies suggest that the nature of insults that occur in preterm low-birth-weight infants may differ from the insults that occur in full-term babies and may be less likely to be associated with subsequent epilepsy. They also indicate that a family history of epilepsy may be an additive risk factor for the development of epilepsy, even in children who are already at risk because of neurologic disability. This has been reported in children with febrile seizures, for whom a family history of epilepsy is a risk factor for the development of subsequent epilepsy even in children who are neurologically abnormal.16

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).
Reviewed and revised May 2004 by Steven C. Schachter, MD,epilepsy.com Editorial Board.