Abstracts

Rationale: Initial EEG examination is frequently normal in patients with epilepsy. The literature on abnormalities of subsequent EEGs in children with epilepsy is scarce. The purpose of this study is to describe the spectrum of epileptiform abnormalities in these children with epilepsy. Methods: Children between the ages 2 months to 18 years with new onset epilepsy who had a normal initial EEG but showed epileptiform abnormalities on a subsequent EEG examination were identified. The charts were reviewed for clinical information including age, gender, seizure type, family history, prior febrile seizures, antiepileptic drugs, comorbidities, and neuro-imaging findings. Epileptiform EEG abnormalities were classified as focal, multifocal or generalized, and whether interictal or ictal. The study was approved by the University Institutional Review Board. Results: Fifty-seven children, 28 boys and 29 girls, mean age 5.7 years (range 4 months to 16 years) were included. Comorbid conditions, family history of epilepsy and history of prior febrile seizures were present in 21(36.8%), 10(17.5%) and 8(14%) children respectively. Clinically significant neuroimaging abnormalities were seen in 19%. Seizures were partial in 28 and generalized in 29 patients. Seizures occurred during wakefulness in 25, sleep in 17 and both sleep and wakefulness in 2. The initial normal EEG was a routine awake-only recording in 43(75.4%), routine awake and sleep in 12 (21.1%), and ambulatory in 2(3.5%) children. The abnormal EEG was a routine awake-only recording in 10(17.5%), routine awake and sleep in 15(26.3%), 24-72 hour ambulatory in 28(49%), and video in 4(7%). The mean interval from normal to abnormal EEG was 8.5 months (range 0.1 to 48 months), and it was sooner with ambulatory EEG than routine EEG (6 months vs 16 months; p=0.028 ANOVA). Most of the repeat studies were obtained due to recurrence of seizure activity. EEG abnormalities were noted in the 2nd EEG in 42(73.7%), 3rd in 12(21.1%), 5th in 2(3.5%), and 6th¬¬ in 1(1.8%). Overall, 53/57 (94.8%) children showing EEG abnormalities were identified by their third EEG. The abnormal EEG findings were focal spikes in 29(50.9%), generalized spike and wave discharges in 23(40.4%), combined focal and generalized discharges in 4(7%) and multifocal abnormalities in 1(1.8%). Fourteen (24.6%) patients showed ictal discharges (partial in 11 and generalized in 3). Generalized epileptiform discharges were significantly more frequent in boys vs girls (50% vs 31%, p=0.031), while focal epileptiform discharges were more frequent in girls (65.5% vs 35.7%, p=0.031). Generalized epileptiform discharges were more common in children with diurnal vs nocturnal seizures (56% vs 23.5%, p=0.0001), and focal discharges more common in children with nocturnal vs diurnal seizures (76.5% vs 40%, p=0.001). Conclusions: Of those patients who eventually had an abnormal EEG, the abnormality was seen within the first 3 EEG studies in 95% of cases. Using ambulatory EEG increases the probability of earlier detection of abnormalities as compared to routine EEG’s. Prospective studies are needed to validate these findings.