An add-on Study of E2007 in Patients With Refractory Partial Seizures Uncontrolled With Other Anti-epileptic Drugs (AEDs)

Inclusion criteria: 1. Male or female aged between 20 and 64 years old. 2. Patients diagnosed with partial seizure (including secondarily generalized seizure). 3. Patients who have at least 3 counts of partial seizures during the previous 4 weeks prior to observation start and no seizure-free for 21 days during 8 weeks before the treatment start based on medical records. Simple partial seizure without motor signs will not be counted. 4. Patients who have been treated for at least 12 weeks but confirmed to be uncontrolled with more than one standard AED for 2 years. 5. Patients treated with stable doses of up to three AEDs. Only one cytochrome P450 (CYP) 3A4 inducer shown below will be allowed for concomitant use: * Carbamazepine * Phenytoin * Phenobarbital * Primidone 6. Patients on stable dose of anti-depressants, anti-anxiety drugs, or mood stabilizers from before 8 weeks. Exclusion criteria: 1. Patients with present or a history of Lennox-Gastaut syndrome. 2. Patients with present generalized seizures (e.g., absence, myoclonic). 3. Patients with a history of status epilepticus within 1 year. 4. Patients with seizure clusters where individual seizure cannot be counted within 8 weeks. 5. Patients with a history of psychogenic seizure. 6. Patients who underwent surgical operation for epilepsy within 2 years. 7. Patients using rescue benzodiazepines at least twice in a 4-week duration within 8 weeks (if 1 or 2 doses over 24-hour period considered one-time rescue). 8. Patients whose alanine aminotransferase (ALT) or aspartate aminotransferase (AST) at enrollment in observation period exceeds 1.5-fold the upper limit of normal (ULN), but those whose ALT or AST are constantly higher than ULN, they can enroll if ALT or AST remain in 3-fold the ULN. 9. Patients with significant active hematological disease; white blood cell (WBC) count \</=2500/uL or neutrophil count \</=1000 uL. 10. Patients on anti-psychotics or who have psychotic disorder and/or psychotic disorder(s) or unstable recurrent affective disorder(s) with a history of suicidal attempt within 2 years. 11. Patients who operate heavy equipment or drive should not be recruited into the study.