Abstracts

Rationale: The published yield of epileptiform discharges in patients with suspected new onset seizures has varied widely based on multiple variables including the patient population, the duration of the recordings and the presence of sleep. In this study, we evaluated the frequency of epileptiform discharges in a prospective study of patients with suspected newly diagnosed epilepsy. Methods: In this study, 28 neurologists from across Lebanon referred their patients (at least 6 month of age) with one or more suspected unprovoked seizures to the American University of Beirut where they underwent a full evaluation. Based on the clinical evaluation, patients were stratified into one of four categories. Category 1: Patients with newly diagnosed epilepsy; category 2: Patients with a single unprovoked seizure; category 3: Patients with non-epileptic events; category 4: Unclear if the event(s) represented a seizure or a non-epileptic spell. All patients underwent a three hours digital video/EEG performed by using 21-channel recordings with electrodes placed according to the International 10-20 system. Additional EMG electrodes were placed as necessary. Each EEG was reviewed by two experienced electroencephalographers and was classified as normal, abnormal without epileptiform discharges or abnormal with epileptiform discharges. In addition, the types and location of the abnormalities were tabulated in detail. Results: In the first 6 months of the study 280 patients were enrolled (Mean age =19 years range: 6 month- 82 years; M/F = 169/111). 98 patients were aged 18 years or older and 182 were aged less than 18 years. Based on the history and clinical examination alone, 135 (48%) were included in category 1 (53 were adults and 82 children and adolescents), 54 (19%) in category 2, 43 (15 %) patients in category 3, and 48 (17%) patients in category 4. The EEG showed interictal epileptiform discharges (IED) in 76 (56%), 17 (31%), 1 (2%) and 8 (17%) of patients stratified to categories I, II, III and IV respectively. The frequency of IED was significantly higher in category I compared to category 2 (76/135 vs. 17/54, p = 0.002), as well as compared to category IV (76/135 vs. 8/48, p< 0.001). There was no significant gender difference in the frequency of IED in Category I patients. The frequency of IED was significantly higher in the pediatric and adolescent age group compared to adults for patients stratified to category I (59/82 vs. 17/53, p < 0.001). A similar trend was found for categories II (13/32 vs. 4/22, p=0.08), and IV (8/35 vs 0/13, p = 0.06) patients. Conclusions: The yield of IEDs in patients with newly diagnosed epilepsy is substantial following a 3 hours sleep deprived EEG. Patients with two or more seizures are significantly more likely to have IEDs compared to patients presenting with a single unprovoked seizure. Age is a significant variable, with younger patients more likely to have IEDs. The study was partially funded by CNRS grant LCR 114110 522214.