Seizure Types and EEG Findings of Juvenile Onset Idiopathic Generalized Epilepsy

ABSTRACT

PURPOSE: Juvenile myoclonic epilepsy, juvenile absence epilepsy, and epilepsy wth generalized tonic clonic seizure (GTCS) on awakening are the three syndromes of idiopathic generalized epilepsy of adolescent onset currently included in the classification of epilepsy syndromes of the International League Against Epilepsy (ILAE). Although they differ in their predominant seizure types, the syndromes share several seizure types. Also, there are no unique electrophysiologic or genetic markers. The question of phenotypic overlap and purity have arison. METHODS: We diagnosed 60 patients as idiopathic generalized epilepsy in Seoul National University Children's Hospital from August 1987 to June 1993 were analyzed in aspects of seizure types, electroencephalographic findings and follow up results. Their onset age of seizure was over 8 year old and the follow-up period was minimum 3 year. RESULTS: 1) seizure types : Four groups were defined by seizure type. The group with absence but not myoclonic (group A) were 19 cases (31.7%) and the group with myoclonic but not absence (group B), 12 cases (20.0%), the group with absence and myoclnic (Group C), 4cases (6.7%), and the group with GTCS only (Group D), 25 cases (41.6%). There was a tendency in that absence begins earlier and myoclonic seizure later in each group. 2) epilepsy syndromes : We could classify as 20 cases (33.3%) of jevenile absence epilepsy, 15 cases (15%) of jevenile myoclonic epilepsy, 5 cases (8.4%) of epilepsy with generalized tonic clonic on awakening, and 20 cases (33.3%) of isolated generalized tonic clonic seizure. 3) EEG characteristics by seizure type : 3-4Hz generalized bursts were most frequent in group A (p<0.05) and polyspike discharges were more frequent in group B than group A (p<0.05). The response to photic stimulation were more frequently observed in group B than group A. There was no significant differences in response to hyperventilation between group A and B. CONCLUSION: To define the combination of seizure types occurred in intervals make easy to approach the diagnosis and treatment of idiopathic generalized epilepsy syndromes. We found that the current classification does not include all patients such as isolated generalized tonic clonic seizure in this study. We can expect information from the fields of molecular genetics and neuroimaging to help to define the etiologic basis of many epilepsies and perhaps to refine the present system of classification, more etiologically oriented and disease-specifically.