Exclusion criteria for all study participants - Severe medical, neurological, or psychiatric disorders or laboratory values, which may have an impact on the safety of the study participant - Study participant is currently participating in another study of an investigational medication (or a medical device) other than brivaracetam (BRV). Exclusion criteria for long-term follow-up (LTFU) study participants only - Study participant ≥ 6 years of age has a lifetime history of suicide attempt or has suicidal ideation in the past 6 months as indicated on the Columbia Suicide Severity Rating Scale (C-SSRS) Exclusion criteria for directly enrolled (DE) study participants in Japan only - Study participant has a history of primary generalized epilepsy, psychogenic non-epileptic seizures, or febrile seizures - Study participant has a history of status epilepticus in the 30 days prior to the Screening Visit (ScrV) or during the Screening Period - Study participant has any clinically significant illness - Study participant has clinically significant laboratory abnormality that may increase the risk associated with study participation or may interfere with the interpretation of study results - Study participant has a clinically significant ECG abnormality - Study participant had major surgery within 6 months prior to the ScrV