Introduction: The different syndromes included in the idiopathic generalized epilepsies present an important overlapping of their electroclinical characteristics.
Aim: To compare the two actual classifications (International classification of epileptic syndromes: ILAE of 1989 and of 2001) in a sample of patients with idiopathic generalised epilepsy (IGE) and to evaluate which electro-clinical factors were more useful in order to classify a patient into a syndrome.
Patients and methods: 70 patients (44 women/26 men). Neurological examination and neuro-radiological examination were normal in all cases. The EEG (standard or sleep deprived) showed generalised epileptiform discharges in all patients. Clinical findings included a median age of onset 12.3 years. Most frequent first type of seizure was tonic-clonic (71%). Seizures during awakening were the most frequent (37%) and lack of sleep was the most important precipitating factor (44.7%). Generalized epileptiform discharges were present in 62.9% of the basal sleep deprived EEG, on the other hand, only 22.3% of the basal standard EEG showed epileptiform discharges, p = 0.048. 28% of patients were unclassifiable according to the 1989 ILAE classification, 7% were unclassifiable according to the 2001 ILAE classification. EEG during intermittent photic stimulation (p = 0.007), at awakening (p = 0.015) and the timetable of the seizures (seizures generalised at awakening) (p = 0.053) differentiated between idiopathic generalised syndromes of adolescence.
Conclusion: The 2001 ILAE classification is more useful in order to classify patients with IGE because includes patients previously considered unclassifiable in the syndrome of generalised epilepsy with different phenotypes.