Abstracts

Rationale: Although the incidence of seizure (SZ) freedom has been studied in a few syndromes with a good prognosis, such as benign Rolandic epilepsy and childhood absence epilepsy, it has not been studied in most epilepsy syndromes. The frequency of SZs among those who continue to have SZs has not been prospectively studied. We prospectively collected data over a long duration to determine the SZ frequency distribution and SZ freedom rate in established epilepsy patients with well classified SZ types and epilepsy syndromes. Methods: 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. Analysis was limited to patients with definite epilepsy at least 5 years old. SZ frequency (number per month) was collected at each visit for each SZ type. The most recent SZ frequency collected is considered the current SZ frequency . A historical maximum monthly frequency and minimum monthly frequency was also collected, as well as demographics, ILAE SZ type, ILAE epilepsy syndrome, etiology, EEG results, neuroimaging, family history, and current and prior antiepileptic drug use. Results: A total of 1639 patients were analyzed. Overall, mean current age was 31.9 years, mean age at SZ onset was 14.4, and 49% were female. Overall, 60% (976 patients) had only partial onset SZ, 37% (602 patients) had only primary generalized SZ and 2% (61 patients) had mixed partial and generalized SZ. Median current SZ frequency was lower in partial SZ (2.6/mo) compared to primary generalized (5.0/mo) and mixed (9.0/mo). Maximum SZ frequency was lower in partial (32/mo) than primary generalized (46/mo) and lower yet in mixed (24/mo). Rate of SZ freedom was lower in partial (49%) than primary generalized (62%) and similar to mixed (42%). Differences between partial and generalized were significant (p< 0.001). Analysis of each individual SZ type was determined. For primary generalized tonic-clonic SZ (GTC) the current median SZ frequency was 5.0/mo, maximum SZ frequency 13.0/mo, and SZ freedom rate 77%. Absence SZ had a higher current SZ frequency (9.0/mo) and maximum SZ frequency (220/mo) and a similar rate of SZ freedom (70%). Complex partial SZ had a lower current SZ frequency (2.5/mo) and maximum SZ frequency (37/mo) and lower rate of SZ freedom (48%). Secondary GTC SZ had the lowest current SZ frequency (1.0/mo) and maximum SZ frequency (9.1/mo) and highest rate of SZ freedom (78%). Among epilepsy syndromes, SZ freedom was most likely in childhood absence (70%), least likely in Lennox-Gastaut (25%), and intermediate in mesial temporal lobe epilepsy (45.4%).