Clinical and electroencephalographic studies were carried out to clarify the characteristics of latent epilepsy (LE) in children and to obtain criteria for treatment. LE was defined as a condition manifesting epileptic EEG abnormalities without any clinical epilepsy, febrile convulsion or other seizures. Three hundred and thirty-nine children with LE seen at the Department of Child Neurology, Okayama University Hospital were divided into four groups by their etiological backgrounds (e. g., organic brain damage and convulsive predisposition) and were compared with 149 controls with clinical epilepsy. Clinical epileptic seizures appeared in 14 (4.1%) of the 339 children during follow-up of two months to 19 years. Thirteen of the 14 cases belonged to the organic brain damage group. The EEG findings in children susceptible to clinical seizures consisted of slow spike-wave, generalized cortico-subcortical discharges, multiple focal cortical discharges, focal discharges with forcal slow wave, and discharges activated by hyperventilation.
The EEG findings in children not disposed to develop clinical epilepsy consisted of sharp wave, small sharp wave, Rolandic spike, parietal focal spike, and photo-sensitivity discharges in adolescence. Convulsive and epileptic predisposition was not regarded as a risk factor in clinical epilepsy. On the basis of these findings, criteria for antiepileptic drug therapy for LE were proposed.