Abstracts

Rationale: New-onset generalized tonic-clonic seizures (GTCS) only without focal features in teenagers and young adult are considered to be primarily generalized unless proven otherwise. It is not certain whether the seizure is truly of generalized or focal origin in patients with GTCS only. We attempted to establish the epilepsy classification, based on EEG and MRI findings in patients with GTCS only without focal features. We retrospectively analyzed clinical characteristics of patients with GTCS only. Methods: We included patients with at least two attacks of GTCS only who underwent scalp EEG and MRI evaluation from Yonsei Epilepsy Registry database which had been documented by a physician between 1999 and 2009. We excluded patients with 1) significant etiological factors except for febrile seizures and family history of epilepsy 2) mental retardation or focal neurological deficits, 3) focal ictal features, such as aura, loss of responsiveness without convulsive movements, conscious head version, and conscious or unconscious focal convulsive movements involving unilateral face or extremities, 4) GTCS only during sleep, and 5) occurrence of focal features on ictal semiology or EEG during the follow-up. Results: A total of 60 patients were selected. Mean number of EEG evaluations was 2 (1 to 5) per patient. Focal or generalized epileptiform discharges on EEG were found in 28% of patients (17/60). Focal structural abnormalities on brain MRI were demonstrated in 13% of patients (8/60). The patients were divided into three groups according to EEG and MRI findings. Group A with generalized epileptiform discharges and normal MRI (strict criteria of generalized epilepsy) consisted of seven patients (11.7%), and their mean age of onset was 18.7 5.7 years (range 12 to 30). Group B with normal EEG and MRI was 37 patients (61.7%), and their mean age of onset was 24.8 13.0 (range 1 to 55). Group C with focal epileptiform discharges or abnormal MRI was 16 patients (26.7%), and their mean age of onset was 34.3 19.0 (range 14 to 69). All patients of group A were under age of 30 years of onset. The onset age of group A was significantly earlier than group C (p=0.038). There was no difference in age of onset between group A and B, and between group B and C. In group C, 56% of patients (9/16) showed focal epileptiform discharges or structural abnormalities in the frontal region. Conclusions: Despite of small sample size, this study suggests that patients with semiologically primarily GTCS had either focal or generalized origin, as expected. The age of onset in addition to EEG and MRI findings may be helpful in differential diagnosis between focal and generalized origin. However, if strict criteria of generalized epilepsy are considered, epilepsy classification may not be possible in the majority of patients with GTCS only.