Abstracts

Population based epilepsy studies provide accurate estimates of incidence and prevalence but provide limited data about precise seizure (SZ) type and epilepsy syndrome characteristics because a detailed SZ history and diagnostic tests cannot be systematically obtained and detailed SZ frequencies are not known. We prospectively collected data on a finite epilepsy population to determine the characteristics defining each SZ type and epilepsy syndrome and correlated it with SZ frequencies, especially with regard to refractoriness. Standardized data were prospectively collected by epileptologists from patients seen in the UVA Epilepsy Clinic from April 1998 to November 2004. Data was acquired directly from patients and medical records, then refined and cleaned by standardized methods and updated at each clinic visit. Analysis was limited to patients with definite epilepsy at least 5 years old. Frequency of each SZ type was collected at each visit. Patients were categorized into 14 classes by the combination of SZ types they possessed. Epilepsy syndromes containing less than 10 patients were not included in comparisons. SZ frequency of each SZ type was plotted over time from June 2000 to November 2004. [ldquo]SZ-free[rdquo] was defined as a total frequency of 0 for all types combined at the last clinic visit. Duration of SZ freedom was defined by interval since last visit at which any SZ were reported (SZ frequency [gt] 0). Current SZ frequency was categorized as 0, 0 to [lt]1, [ge]1, and [ge]30 SZ/mo. A total of 1638 patients were analyzed. Overall, current SZ frequency was 0 in 51%, 0-1 in 14%, [ge]1 in 35%, and [ge]30 in 8%. SZ frequency was more likely to be 0 for patients with Only Generalized SZ (60%) compared to Only Partial SZ (47%) or Mixed SZ (40%) while Mixed SZ was more likely to be [ge]30 SZ/mo (21%). Among the categories of SZ combinations, GTC Only was most likely to be SZ free (73%) and CPS+SPS+Secondary Generalized was least likely (33%). SZ frequency [ge]30 was most common for Mixed SPS+Primary Generalized (57%) but this group only contained 7 patients. Among epilepsy syndromes, SZ freedom was most likely for Juvenile Absence (80%), Benign Rolandic (79%), and Idiopathic Localization-Related Not Further Classifiable (73%). Lennox-Gastaut (29%) was most likely to have [ge]30 and Juvenile Myoclonic Epilepsy (16%) is also likley but mostly due to myoclonic SZs. SZ frequency [ge]1 was most likely for LGS (65%), frontal lobe epilepsy (50%), and MTLE (42%). MTLE patients were generally unlikely to be SZ free (44%) and also unlikely to have essentially daily SZs (5%). The overall rate of SZ freedom is surprisingly high. Refractoriness varies by epilepsy syndrome and SZ type but associates best with epilepsy syndrome. Patients with mixed SZ types are more likely to be refractory and have essentially daily SZs. MTLE was among the most frequently refractory, which is important because it represents the most common identifiable epilepsy syndrome.