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Summary:Purpose: Very fast activity was investigated on the ictal EEGs of epileptic spasms to elucidate the pathophysiology of West syndrome (WS) and related disorders from a novel point of view.Methods: The traces of scalp ictal EEG of spasms temporally were expanded in 11 patients whose clinical diagnosis was symptomatic WS in six, cryptogenic WS in two, Aicardi syndrome in one, and symptomatic generalized epilepsy after WS in the remaining two. Time evolution of averaged power spectra of the ictal fast activity also was analyzed in each patient.Results: Rhythmic gamma activity with frequency ranging from 50 to 100 Hz was detected in a total of 345 of 537 spasms.Fast activity was seen bilaterally in nine patients, was lateralized to one hemisphere in another, and appeared independently on each hemisphere in the remaining infant with Aicardi syndrome. Power spectra showed a clear peak corresponding to spasmassociated gamma rhythm, with frequency centering ∼65 Hz and ranging from 51 to 98 Hz. The morphology and spectral characteristics of ictal gamma rhythm were completely different from those of muscle activity or alternating current (AC) artifacts.Conclusions: Spasm-associated gamma activity was clearly detected on the scalp. This observation may provide a clue to the pathophysiology of spasms.

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Summary:Purpose: A population-based survey of childhood epilepsy was undertaken in Okayama Prefecture, Japan, to determine the prevalence rate and the distribution of epilepsies and epileptic syndromes according to the International Classification (ILAE, 1989).Methods: Information on patients younger than 13 years with active epilepsy was collected from medical records. Patients diagnosed with epilepsy according to clinical and EEG findings were put on the list even if those patients had had a single seizure or seizures occurring during febrile episodes.Results: In total, 2,220 cases were identified from a background population of 250,997. The prevalence rate was 8.8 per 1,000. If we exclude patients who had experienced a single seizure or seizures occurring during febrile episodes to compare our results with previous reports, the prevalence rate was 5.3 per 1,000. Of the 2,220 cases, 2,030 (91.4%) were classified into three major categories by ILAE classification. They consisted of 1,556 (76.7%) with localization-related epilepsy, 453 (22.3%) with generalized epilepsy, and 21 (1.0%) with undetermined epilepsy. Of the 2,030 cases, 309 (15.2%) were classified into epileptic syndrome categories, and 84.8% of the total were nonspecific types of epilepsy.Conclusions: The prevalence rate of childhood epilepsy was distributed from 5.3 to 8.8 per 1,000. The appearance rate of various types of epileptic syndromes was low. Most cases could not be classified into the detailed categories of the International Classification (ILAE, 1989). Key Words: PrevalenceChildhood epilepsy-Classification-Epileptic syndromesPopulation-based survey.Population-based surveys of epilepsy have been repeatedly undertaken in many countries. However, the appearance rate or distribution of various types of epilepsies and epileptic syndromes (1) (5) reported on the appearance rate of epileptic syndromes. In these population-based surveys, many types of epileptic syndromes were not detected because the patients numbered fewer than 200. We therefore carried out a population-based survey of childhood epilepsy within a large population in Okayama Prefecture, Japan. SUBJECTS AND METHODSWith December 31, 1999, as the prevalence day, the child population in Okayama Prefecture younger than 13 years was 250,997 (128,452 boys, 9,429-10,869 per year of age; 122,545 girls, 8,975-10,447 per year of age). We determined that the patients who had taken antiepilepAccepted October 8, 2005. Address correspondence and reprint requests to Dr. E. Oka at Asahigawa Rehabilitation Center Jidouin Hospital, Gion Chisaki, Okayama 703-8555, Japan. E-mail: e-oka@jidouin.jp tic medications (AEDs) or who had experienced at least one seizure during the previous 5 years had active epilepsy. If a case with a convulsion during a febrile episode has definite epileptic discharges in interictal EEG, it should be considered to have not only a simple febrile convulsion or a complex febrile convulsion, but also an epileptic seizure occurring during febrile episode.The patients diagnosed...

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