To compare the effect of 2 drug regimens consisting of either rufinamide or any other approved AED of the investigator’s choice as an add-on to the subject’s existing regimen of 1-3 AEDs on the overall safety and tolerability of rufinamide in subjects aged 1 to less than 4 years of age with inadequately controlled LGS To characterize the age group specific pharmacokinetics of rufinamide in a pediatric population, 1 to less than 4 years of age, with inadequately controlled LGS, using the population approach To evaluate the effect of rufinamide as adjunctive treatment on the cognitive development and behavioral effects in a pediatric population, 1 to less than 4 years of age, with inadequately controlled LGS.