[Usefulness of ambulatory EEG in detecting critical and intercritical events in patients with epilepsy or with suspected epilepsy].

Ambulatory EEGs (EEGAs) were recorded in 251 patients. In 91 of these patients there was a suspicion of having epileptic seizures, in 117 a diagnosis of epilepsy was already established, in 43 the withdrawal of antiepileptic drugs was envisaged being apparently free from seizures for years. The EEGA showed epileptogenic abnormalities in 31% of patients of the first group. This percentage was not far from the one obtained with standard EEG (EEGS) recordings. In the second group, a divergence was found, as for the classification of seizures, between the ictal events actually recorded on the EEGA and the definition of seizures based on clinical information. Furthermore ictal events recorded by the EEGA were less frequent than one would have anticipated according to the seizure frequency asserted by the patients. In the third group the EEGA disclosed the persistence of epileptic seizures, mostly represented by diffuse spike and wave discharges, in about 30% of the patients. Finally, comparison of the results obtained by the EEGA with those obtained by the EEGS in all patients suggested that the two recording techniques are complementary.