Abstracts

Rationale: Idiopathic generalized epilepsy (IGE) is typically well controlled by first or second line medications. Some patients are resistant to multiple medications however. While drug resistance in partial epilepsy has been extensively studied, not much is understood about drug resistance in IGE. We therefore wished to examine whether particular clinical or electrophysiological varaiables were associated with drug resistance in a large cohort of patients with IGE Methods: Patients were identified using the searchable EEG database at our institution (1998-2008), regardless of referring physician. All individuals whose EEGs displayed bursts of generalized, bifrontally predominant, spike and slow wave discharges at greater than 2.5Hz on a normal background were identified. Clinical records were then reviewed and all individuals with a history consistent with IGE were further studied. Patients were subclassified into “drug-responsive”, “pseudoresistant” or “drug-resistant”. A detailed database containing multiple clinical and electrophysiological variables was constructed. Raw EEG data was then analyzed manually and quantitatively for each individual to determine the presence of interhemispheric spike amplitude asymmetry and interhemispheric spike time-lag as well as the presence of polyspikes, focal discharges and photoparoxysmal response. Univariate and multivariate analyses were performed to assess for correlation between the identified variables and drug resistance Results: A total of 364 patients were initially identified. 326 of these had a clinical picture consistent with an IGE syndrome. Of those included in the study 23% had CAE, 19% had JME. Overall 17% of our IGE cases were classified as drug-resistant. Analysis of clinical and electrophysiological variables was performed. Some degree of interhemispheric spike amplitude asymmetry was noted in over 50% of the total cases. A significant and persistent spike amplitude asymmetry did not necessarily exclude an IGE syndrome and did not always correlate with drug resistance Conclusions: In our cohort of IGE patients, 17% of cases were classified as drug-resistant. We used EEG as a starting point to obtain our cohort, thus ensuring it was taken from a broad cross-section of medical care ranging from primary care to specialized epilepsy clinics, helping to reduce the risk of ascertainment bias. We examined a large number of clinical and electrophysiological variables associated with drug resistance. This data may help predict patients with IGE who are at higher risk of developing drug resistance