Trial to Assess Lacosamide as the First add-on Anti-epileptic Drug Treatment in Patients With Partial-onset Seizures

Inclusion Criteria: Group 1: * Subject has a diagnosis of epilepsy with simple partial seizures (motor component) and/or complex partial seizures with or without secondary generalization * Currently taking adequate monotherapy (defined as a single Antiepileptic Drug (AED) for at least 28 days prior to Screening) and has no history of AED polytherapy. Prior use of rescue medication (short-term intermittent use) is acceptable * Epilepsy diagnosis should be ≤24 months at the time of the Screening Visit * The minimum allowed seizure frequency at any time during the 12 weeks prior to the Screening Visit is ≥3 partial-onset seizures Group 2: * Subject has a diagnosis of epilepsy with simple partial seizures (motor component) and/or complex partial seizures with or without secondary generalization * Currently taking 1 to 3 AEDs, and has tried at least 2 prior AED treatment regimens (concurrently or sequentially) * Epilepsy diagnosis should be ≥5 years at the time of the Screening Visit * The minimum allowed seizure frequency during the 12 weeks prior to the Screening Visit is ≥1 partial-onset seizure per 28 days Exclusion Criteria: * Previous use of Lacosamide * History of seizure disorder characterized primarily by isolated auras * History of primary generalized seizures * History of status epilepticus within last 12-months * History of cluster seizures during the 12 week period prior to Visit 1 * Nonepileptic events, including pseudoseizures that could be confused with seizure * Lifetime history of suicide attempt or suicidal ideation in the past 6 months * Hypersensitivity to any component of Lacosamide * History of drug or alcohol abuse * History of an acute or subacutely progressive Central Nervous System (CNS) disease * Undergone cranial surgery within the last year prior to study entry * Concomitant treatment of Felbamate or previous Felbamate therapy within the last 6 months * Prior or concomitant Vigabatrin use