Abstracts

Rationale: Although the rate of seizure freedom (SF) has been reported for various epilepsy syndromes, overall there is no good information on what percentage of the patients with different type of seizure or epilepsy syndrome can achieve SF. We prospectively collected data over a long duration to determine SF rates at different durations in established epilepsy patients with well phenotyped seizure (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 at least 5 years old with definite epilepsy. 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 . Patients with current SZ frequency 0/month are selected and SF duration is determined for patients who had at least 3 follow up visits. A historical maximum and minimum monthly frequency was also collected, as well as demographics, ILAE SZ type and epilepsy syndrome, etiology, EEG results, neuroimaging, family history, and current and prior antiepileptic drug use. Results: A total of 1639 patients were analyzed. 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. 1079 patients (66%) were SF at their last visit. Among 495 of them with more than 3 visit, SF rates for at least 12 mo. and at least 24 mo. for the whole group were 80.6% and 52.3%, for partial onset were 78.8% and 52.6%, and for primary generalized were 83.9% and 52.1%. Analysis of each SZ type was determined: SF rates at 12 mo. and at 24 mo. for complex partial SZ (77.9% and 51.8%), secondary generalized tonic clonic (GTC) SZ (78.8% and 50.2%), absence SZ (82.5% and 50.9%) and primary GTC SZ (81.5% and 53.8%) were similar to each other and better than atonic, myoclonic and tonic SZs for SF at least 24 mo. (27.3%, 40.0% and 37.5%). Among epilepsy syndromes, current SF rate was best in childhood absence epilepsy (CAE) (70%), least in Lennox-Gastaut Syndrome (LGS) (25%), and intermediate in mesial temporal lobe epilepsy (MTLE) (45.4%). At 12 mo. and 24 mo. SF rates were 70.0% and 40.0% for CAE, 90.0% and 50.0% for LGS and 88.3% and 55.9% for MTLE. However, only 10 patients had CAE and LGS. 49 patients with MTLE underwent surgery and 20 had more than 3 visits with SF rates of 95.0% and 55.0%. For 12 patients who had temporal lobe lesion other than MTLE, the rates were lower at 50.0% and 25.0%. Conclusions: These data quantify and support the popular notion that 2/3 of epilepsy patients are SZ free at any one point in time. Rates were surprisingly similar for partial and generalized seizures but this is likely due to grouping several seizure types together. A surprisingly high SF rate is found in LGS and MTLE and prolonged SF may be lower than expected in CAE.