Interictal paroxysmal EEG abnormalities in childhood absence epilepsy

The aim of this study is to analyze the graphic features and the clinical significance of the focal interictal paroxysmal abnormalities (FIPA) which can be found in the EEG of patients with typical absences, on the basis of 29 personal cases. The children (15 female; mean age at the first evaluation = 8.2 years, range 4.8-14.3 years) were particularly selected, because they only showed absence seizures. In all subjects the ictal clinical and EEG features were typical for childhood absence epilepsy (CAE). The interictal EEG showed a normal background activity in all children and in 11 patients the presence of FIPA specially on frontal areas. The graphic aspects of FIPA and their spatial and temporal variability, often in the same subject, were in agreement with a functional form. Furthermore the excellent response to valproic acid and ethosuximide, with a complete seizure control also in the follow-up in 26 among 28 treated children, confirms the opinion that our cases are affected by a typical form of CAE. In conclusion FIPA probably are not uncommon in typical idiopathic CAE and their presence does not seem to change the benign prognosis. There is a relationship between our data and the experimental models proposed in the literature.