Open-Label Study to Assess Lacosamide Safety as Add-on Therapy for Primary Generalized Tonic-Clonic Seizures in Subjects With Epilepsy

Inclusion Criteria: * Subject has a diagnosis of uncontrolled epilepsy with primary generalized tonic-clonic (PGTC) seizures and idiopathic generalized epilepsy. Diagnosis should have been established by an electroencephalogram (EEG) with generalized spike-wave discharges within 5 years of the screening visit * Subject has ≥1 PGTC seizure within the 12 weeks prior to the screening visit * Subject has a stable dose regimen of 1 to 3 marketed antiepileptic drug(s) (AEDs) with or without additional concurrent stable Vagus Nerve Stimulation (VNS). The VNS must have been in place for at least 6 months prior to study entry with constant settings for at least 28 days prior to the screening visit and during the Baseline Phase. Benzodiazepines will be counted as an AED Exclusion Criteria: * Subject has a history of partial-onset seizures or EEG findings consistent with partial onset seizures * Subject has a history of status epilepticus within the 5-year Period prior to Visit 1 * Subject has a current or previous diagnosis of pseudoseizures, conversion disorders, or other non-epileptic ictal events * Subject has any medical or psychiatric condition * Subject has any history of alcohol or drug abuse * Subject is currently taking felbamate * Subject has ever taken vigabatrin and has no visual fields examination report available or if results of the examination are abnormal * Subject is on a ketogenic diet * Subject has a known sodium channelopathy