Active epilepsy in mentally retarded children

Abstract

A population-based study of active epilepsy was conducted in 6-13-year-old mentally retarded children born in 1975-86. The population at risk comprised 48, 873 children. Ninety-eight children were identified, 35 mildly retarded and 63 severely retarded 23 of whom were profoundly retarded. The prevalence rate was 2.0 per 1,000; 0.7 per 1,000 for mildly retarded and 1.3 per 1,000 for severely retarded. Sixty-nine children had a major additional neuroimpairment, 42 children had cerebral palsy and 24 children visual impairment. A biopathological origin was established in 66% of the mildly retarded and 92% of the severely retarded children: a prenatal etiology was considered in 51% and 57%, a perinatal one in 9% and 19%, a postnatal one in 6% and 16% and an untraceable etiology in 34% and 8% respectively. Thirty-four pre- and perinatal optimal items were defined. Children with a prenatal etiology did not differ from controls in any of the periods. Compared with controls, children with a perinatal etiology had higher proportions of non-optimal items, increasing successively through the pre- and perinatal periods and showing the accumulation of non-optimal events. The median age at seizure onset was 1.3 years, 3.1 years in mildly retarded children and 0.8 years in severely retarded children. Current seizure groups were partial in 20, generalized in 59 and mixed in 19. The prevailing seizure types were tonic-clonic, myoclonic, atypical absences and partial complex seizures which were present in 42, 33, 23 and 23 children respectively. Neonatal seizures (n = 25), infantile spasms (n = 12) and status epilepticus (n = 37) occurred independently of one another. Prognostic factors of poor neurological outcome were early onset of epilepsy, infantile spasms as onset type and prior neonatal seizures. Forty-four children, 9 mildly retarded and 35 severely retarded, had intractable epilepsy, defined as one or more seizures every day or week. The median age at onset was 0.8 years compared with 3.0 years for those with controlled epilepsy. Predictive factors of frequent seizures were the number of seizure types, severe mental retardation, status epilepticus and tonic seizures. Epileptiform activity on EEGs closest to the prevalence day was present in 91%, with signs of focality in 88%. Brain lesions were detected with computed tomography and magnetic resonance imaging in 70%, with generalized lesions in 60%. Three children had Lennox-Gastaut syndrome, accounting for 3% of all the children with mental retardation and active epilepsy. In the psychiatric study, 90 of the 98 children were evaluated. Fifty-nine per cent had at least one psychiatric diagnosis and the conditions in 33% could not be classified because of profound mental retardation. The most frequent psychiatric disorders were autistic disorder and autistic-like condition, present in 27% and 11% respectively, giving a combined prevalence rate of 0.7 per 1,000. Children with mental retardation and active epilepsy constitute a severely disabled group, indicating severe brain dysfunction and damage. Pediatric neurologists, child psychiatrists, neuroradiologists, neurophysiologists, neurosurgeons and physiotherapists need to develop comprehensive programmes for the adequate management of active epilepsy in mentally retarded children. This management should take place in a network comprising other medical services, school, social workers and in some cases epilepsy rehabilitation.