Any untoward medical occurrence in a participant who received study drug was considered an adverse event (AE), without regard to possibility of causal relationship. Treatment-emergent adverse events: those which occurred or worsened after baseline. Severe AEs: those which interferes significantly with participant's usual function. An AE resulting in any of the following outcomes, was considered to be a serious adverse event: death; life-threatening; initial or prolonged inpatient hospitalization; persistent or significant disability/incapacity; congenital anomaly/birth defect.

The Response Ratio calculated by the following equation : Response Ratio = (T minus B) divided by (T plus B), where T is seizure frequency per 28 days (i.e., the number of seizures per 28 days) calculated from the total number of seizures for the 52-week treatment period, and B is seizure frequency per 28 days (i.e., the number of seizures per 28 days) calculated from the total number of seizures for the 6-week baseline period of the previous study A9451162 (NCT00603473).

Responder Rate was defined as the percentage of subjects with a 50 percent or greater reduction in the seizure frequency per 28 days for the 52-week treatment period in comparison with the frequency per 28 days for the 6-week baseline period of the previous study A9451162 (NCT00603473).

Percent change in seizure frequency (PCH) was calculated as follows: PCH = 100*(T minus B) divided by B, where T is seizure frequency per 28 days (i.e., the number of seizures per 28 days) calculated from the total number of seizures for the 52-week treatment period, and B is seizure frequency per 28 days (i.e., the number of seizures per 28 days) calculated from the total number of seizures for the 6-week baseline period of the previous study A9451162 (NCT00603473).