This is a multicenter, randomized (treatment is assigned by chance), open-label (everyone who is involved in the trial knows the study drug), parallel group trial. The study has three phases: a retrospective baseline assessment of patients (4 weeks), titration period (8 weeks) and maintenance period (8 weeks). After qualifying for trial entry in the retrospective baseline phase, eligible patients will be randomized in 1:1 ratio to receive either topiramate add-on therapy or topiramate monotherapy. During the titration period (period in which the dose of the study drug is increased or decreased at the discretion of investigator), topiramate, given as morning doses, will be started with daily doses of 25 mg/day for one week. After that, topiramate will be given as morning and evening doses, and the doses will be gradually increased every week to reach the initial target dose of 200 mg/day at the end of titration period. During the maintenance period, the dose of topiramate could be increased or decreased according to the investigator's judgment. Patients should keep seizure diaries during the 16 weeks of topiramate treated period and are followed with once monthly visits to the clinic, at which safety will be evaluated.
