Seizure relapse and development of drug resistance following long-term seizure remission

Abstract

Objective: To quantify and identify predictive risk factors for seizure relapse and development of drug resistance in patients who achieved long-term (>1 year) antiepileptic drug-induced seizure remission. Design: Prospective cohort study. Setting: Epilepsy Center, Rambam Medical Center. Patients: Two hundred fifty-six consecutive patients who entered long-term (>1 year) antiepileptic drug-induced seizure remission were followed up prospectively for 2 years or more. Main Outcome Measures: Seizure relapse and development of drug-resistant epilepsy. Results: Five years after entering seizure remission, 40.2% of patients experienced seizure relapse and 25.3% of patients developed drug-resistant epilepsy. The Kaplan-Meier curves could be fitted by monoexponential functions, with a maximal seizure relapse rate of 43.6%, maximal drug-resistance rate of 27.4%, and half-decay constant of 21.5 months for both curves. Treatment history served as a significant independent prognostic risk factor for both seizure relapse and development of drug resistance. The preremission seizure frequency and duration of epilepsy were also identified as significant prognostic risk factors in the univariant analysis but failed to reach statistical significance in the multivariate analysis. Conclusion: Seizure relapse commonly occurs in patients following long-term seizure remission. Treatment history and duration of epilepsy are predictive risk factors for both seizure relapse and development of drug resistance. ©2009 American Medical Association. All rights reserved.