Study to Evaluate the Safety and Efficacy of Levetiracetam in Patients Suffering From Idiopathic Generalized Epilepsy With Primary Generalized Tonic-clonic Seizures

Inclusion Criteria: * Subject with a confirmed diagnosis consistent with idiopathic generalized epilepsy experiencing primary generalized tonic-clonic seizures (IIE) that are classifiable according to the ILAE Classification of Epileptic Seizures. * Presence of at least 3 PGTC seizures during the 8-week combined Baseline period. * Absence of brain lesion documented on a CT scan or MRI. * An EEG performed within 1 year of Visit 1 with features consistent with PGTC seizures or generalized idiopathic epilepsy. * Male/female subject, \>=4 or \<=65 years of age at Visit 1. * Subject on a stable dose of one or two AEDs during baseline. Exclusion Criteria: * Previous exposure to levetiracetam. * History of partial seizures. * History of convulsive or non-convulsive status epilepticus while taking concomitant AEDs within three months prior to Visit 1.