This is a registry study, where sites will enter patients with LGS who require a modification in anti-epileptic therapy (either the addition of another anti-epileptic drug, or the change of one drug to another). This will include patients who are started on rufinamide. Patients will be reviewed according to local practice, but it is envisaged that review will occur at approximately one month, three months and six months, and then every six months. Upon entry to the registry baseline details concerning disease severity, diagnosis, prior therapy, and developmental assessment will be recorded. On each subsequent visit the patient (usually through their caregiver) will be asked about current medication, general seizure profile, any seizures deemed to be of medical significance, tolerability, AEs (including suicidal-related events), and healthcare resource utilisation.