Abstracts

Rationale: Surgical intervention is expected to improve the quality of life in patients with intractable epilepsy by providing adequate seizure control. Although many previous studies showed various rates of seizure freedom, definite conclusions have not yet been made regarding outcomes.Methods: In order to clarify the long-term postoperative outcome for a period of up to 10 years, a retrospective chart review of patients who underwent epilepsy surgery at our department between 1992 and 2003 was performed. Only patients who underwent resection surgery for curative purpose and had multiple seizure episodes with adequate usage of the appropriate antiepileptic drugs were included. Eventually, 76 patients were included in this study. The clinical features of the entire group are summarized in Table. Intracranial electrodes were implanted in 28 (37%) out of 76 patients prior to resection surgery. MRI scans detected an abnormality in 70 cases out of 76. While 65 cases showed signal abnormality within the single lobe, only 5 cases showed lesion over multiple lobes. All patients were checked on their regular visits to the outpatient clinic, and all medical records were reviewed retrospectively up to 10 years after the resection surgery. The state of epilepsy after surgical treatment was assessed by the classification of Engel s criteria. Seizure outcome was evaluated 2, 5, and 10 years after the surgery. In addition to this conventional evaluation of seizure control, we adopted Kaplan-Meier survival analysis. In this analysis, patients were classified as seizure free if they achieved an Engel Class I rating postoperatively throughout the entire period of 10 years. The primary endpoint was decided at the first occurrence of disabling complex partial seizure and/or the occurrence of a secondarily generalized seizure.Results: Out of 76 patients, 6, 17, and 32 patients were lost to follow-up at 2, 5, and 10 years after the surgery, respectively. The patients were lost to follow-up for various reasons: referral to another hospital (25 cases), reoperation (6 cases), and death (1 case). The most favorable outcome, defined as an Engel Class Ia, was achieved in 26 (37%), 24 (40%), and 18 (41%) cases at 2, 5, and 10 years after surgery, respectively. The second favorable, outcome defined as an Engel Class Ib-d, was achieved in 22 (31%), 21 (36%), and 19 (22%) cases at 2, 5, and 10 years, respectively. These results did not reach significant differences regarding the favorable outcome group among the 3 different time periods of evaluation after surgery. The Kaplan-Meier survival curve illustrating seizure recurrence in the overall group is shown in Figure. The estimated probability of seizure freedom was 86% (95% CI, 82 90%) at 1 postoperative year, 75% (70 80%) at 2 years, 67% (62 72%) at 5 years, and 51% (45 57%) at 10 years.Conclusions: In this study, we showed that long-term favorable outcome of seizure control following resection surgery can be achieved in more than half of patients.