The evaluation of interictal focal EEG findings in adult patients with absence seizures

Abstract

Purpose To investigate the focal interictal EEG abnormalities in adult patients with absence seizures (ASs) and to identify their clinical, EEG and semiological correlates. Methods Fifty patients older than 18 years, diagnosed as having IGE with AS documented with ictal recordings. Interictal focal sharp or spike–waves and strictly focal paroxysmal slow activity were considered as focal EEG features. The patients having focal EEG features were classified as “Group I”, whereas the remaining of them was classified as “Group II”. Results We observed focal findings in 34% of the patients, mainly in frontotemporal (41%), and frontal (29%) regions. There were no significant differences with respect to the clinical parameters such as sex, epilepsy duration, positive family history and the age of the onset between the groups. Psychiatric co-morbidities were significantly higher in Group I when compared to Group II ( P = 0.00). Accompanying automatisms were higher in Group I, whereas eye deviation during absences was higher in Group II. In Group I, the asymmetry of the ictal discharges was more frequently observed. Focal EEG features were more frequently seen in juvenile absence epilepsy syndrome, without reaching a significance level. Conclusion The focal findings in adult absence epilepsy patients could have some unknown etio-pathogenetic and prognostic implications. We emphasize the cautious interpretation of isolated interictal focal EEG abnormalities to prevent a wrong diagnosis of focal epilepsy in patients who may indeed suffer from generalized epilepsy.